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Article

Sandwich Composite Panel from Spent Mushroom Substrate Fiber and Empty Fruit Bunch Fiber for Potential Green Thermal Insulation

by
Mohammad Aliff Shakir
1,
Mardiana Idayu Ahmad
1,2,*,
Yusri Yusup
1,2,
Saikh Mohammad Wabaidur
3,
Masoom Raza Siddiqui
3,
Mahboob Alam
4 and
Mohd Rafatullah
1,2,*
1
Environmental Technology Division, School of Industrial Technology, Universiti Sains Malaysia, Penang 11800, Malaysia
2
Green Biopolymer, Coatings & Packaging Cluster, School of Industrial Technology, Universiti Sains Malaysia, Penang 11800, Malaysia
3
Chemistry Department, College of Science, King Saud University, Riyadh 11451, Saudi Arabia
4
Division of Chemistry and Biotechnology, Dongguk University, 123, Dongdaero, Gyeongju-si 780714, Republic of Korea
*
Authors to whom correspondence should be addressed.
Buildings 2023, 13(1), 224; https://doi.org/10.3390/buildings13010224
Submission received: 30 November 2022 / Revised: 7 January 2023 / Accepted: 10 January 2023 / Published: 13 January 2023
(This article belongs to the Special Issue Advancements in Prefabricated Construction: Materials, Structures, Construction, and Management)
Browse Figures
Versions Notes

Abstract

:
Massive generation of natural waste fiber from agricultural industries followed by improper disposal management might result in a detrimental effect on our ecosystem contributing to various types of environmental pollution. With the growing significance of climate change, an effort is being undertaken by utilizing natural waste fiber into eco-friendly insulation panels to reduce the environmental impact of buildings. In this research, a composite panel was developed from spent mushroom substrate (SMS) and empty fruit bunch (EFB) fibers via a sandwich technique. Five samples were made, each with a different fiber ratio (100 SMS: 0 EFB, 80 SMS: 20 EFB, 60 SMS: 40 EFB, 40 SMS: 60 EFB, and 0 SMS: 100 EFB) at density 0.8 g/cm3. Fourier transformation infrared (FTIR) Soxhlet extraction followed by thermogravimetric analysis (TGA) indicated that the SMS and EFB fibers were relevant for fabrication into a composite panel for thermal insulation. Thermal conductivity, thermal resistance, and thermal diffusivity values for these five composite samples were 0.231 to 0.31 W/(mK), 0.0194 to 0.0260 m2K/W, and 0.2665 to 0.3855 mm2/s, respectively. The flexural strength of the composite was at the range 15.61 to 23.62 MPa. These research findings suggest that the fabrication of a sandwich composite panel from SMS and EFB fiber is a promising alternative way to utilize natural waste fiber.

1. Introduction

The rise of environmental consciousness and a scarcity of natural resources have prompted many manufacturing industries to look for a new potential material derived from renewable resources to replace conventional materials. This urging for ‘green’ material has led the manufacturing companies to utilize natural waste fiber as an alternative material [1]. Natural waste fiber has been identified as a renewable and biodegradable resource frequently generated by the agriculture and wood industries. Spent mushroom substrate (SMS) fiber is one of the valuable natural waste fibers taken from the mushroom industry that has a significant potential to be utilized in a fiber-based product. Technically, it is a form of lignocellulose substance that contains carbon and is used as a nutrient to enhance mushroom growth, mushroom production, and mushroom fruiting bodies [2]. Another potential natural waste fiber used for utilization in fiber-based products is empty fruit bunch (EFB) fiber. The EFB is considered the most valuable natural waste fiber generated abundantly during the process, which has many potentials to be used in various applications [3]. As a replacement for conventional cellulose-based materials, the chemical properties of EFB fiber have been reported to contain an almost similar composition to that of hardwood material [4]. According to recent studies, the mushroom industries generated around 50 million tonnes of SMS fiber per year, while the oil palm sector generated approximately 51.19 million tonnes of EFB fiber per year globally [5,6]. A massive stockpile of SMS fiber has been declared environmentally hazardous after it was discovered to be a new breeding ground for flies and a source of foul odors [7]. These environmentally hazardous actions have resulted in environmental pollution such as contamination of water sources, air pollution, and eutrophication [8,9]. From the environmental perspective, it appears that the EFB fiber holds similar issues to those of SMS fiber, where both natural waste fibers have tremendous quantity generation with low commercial value, resulting in significant environmental pollution. This issue has gained considerable attention from researchers, scientists, and engineers to develop appropriate technologies for utilizing the SMS and EFB fibers based on a waste-to-resource approach. Previous research indicated that increasing the stockpile of natural waste fibers in landfills and flawed waste fiber management systems has resulted in significant environmental and air pollution due to increased dumping areas and open burning, respectively [10].
Concerning this, a few developed methods have been implemented in utilizing the SMS and EFB fibers in various applications, such as animal feed and plant fertilizer and including composite insulation panels [11,12]. Apart from the numerous advantages of the utilization of natural waste fibers in terms of abundance, availability, and low cost, they also have high strength and eco-friendly properties that make them suitable for use in a wide variety of applications such as the automotive industry, construction, packaging, furniture, and shipping pallets [13]. During material selection, additional criteria such as processing costs, chemical composition, thermal stability, shelf life behavior, elongation at failure, and fiber adhesion must be considered before being fabricated into particular products. A previous study report by Ramlee [14] revealed that one of the most effective approaches was to utilize the natural waste fibers in composite panels for thermal insulation applications. In addition, throughout the literature, it was evident that natural fiber was one of the earliest materials employed in construction and building that was also capable of serving as an insulation panel owing to its superior thermal and mechanical properties [15].
However, Rebolledo [16] indicated that the composite panel for heat insulation applications made from natural waste fibers tends to generate the formation of multiple void structures inside the panel cavity. This void formation occurs due to less homogeneity in fiber packing, fiber entanglement, and fiber distribution in the composite panels, which is affected mainly by the fiber particle size [17]. It is important to note that the void structures play an important role in influencing the thermal characteristic of the composite panel by lowering the thermal conductivity value. Despite all the above facts, it is worth mentioning that the insulation panels made from natural waste fibers also possess disadvantages in terms of low mechanical properties due to poor fiber particle contact in order to generate the formation of void structures within their cavities.
Previous studies suggested that adding an adhesive/binder, reducing particle size, or adding filler could improve the mechanical properties of the insulation panel [18]. However, the studies also stated this action would lead to an increase in the composite thermal conductivity and lower its insulation panel performance. It is important to consider the characteristics of a composite panel as it should be able to resist the least amount of load feasible when utilized in any heat insulation application. Therefore, the objective of this study was to fabricate and evaluate a sandwich composite panel made from SMS and EFB fibers to be used for potential green thermal insulation materials with adequate thermal characteristic and acceptable mechanical properties.

2. Materials and Methods

2.1. Materials

The spent mushroom substrate (SMS) fiber with an average fiber length of 686.75 μm was collected from a mushroom farm house at PPK Lahar Bubu, Penang, Malaysia. The empty fruit bunch (EFB) fiber was obtained from oil palm trees supplied from United Oil Palm Sdn. Bhd., Penang, Malaysia. In the beginning of the experimental work, the geometrical structure of the EFB fiber was physically modified using a Waldron Disc refiner using a refining gap of 1.75 mm and achieved a fiber length with an average value of 60,000 µm.

2.2. Methods

2.2.1. Sample Preparation of SMS and EFB Fiber

The SMS fiber sample preparation was begun by withdrawing the fiber from the mushroom substrate plastic blocks as shown in Figure 1a and disintegrating it homogeneously and manually, as shown in Figure 1b. The water content of the SMS fiber used in the characterization was maintained at below 5%, while for the composite fabrication process, it was maintained at 65%. For the EFB fiber, the fiber was prepared in the form of a fiber mat at four different percentages: 20%, 40%, 60%, and 100%, based on composite target density. The EFB fiber mat was stored in the oven at a temperature of 100 °C before the composite fabrication process to ensure the water content of the fiber was maintained at 0%. This step is crucial to initiate the liquid transfer (hot water-soluble content) from the SMS fiber to the EFB fiber during the hot press process. In this experimental work, the SMS and EFB fiber ratios were formulated into five ratios, namely, 100 SMS: 0 EFB, 80 SMS: 20 EFB, 60 SMS: 40 EFB, 40 SMS: 60 EFB, and 0 SMS: 100 EFB.

2.2.2. Fabrication of Sandwich Composite Panel

In the fabrication process, the composite panels made of EFB and SMS fibers were fabricated at dimensions of 300 mm (length) × 210 mm (width) × 6 mm (thickness) using a hot press process at a temperature of 130 °C for 40 min. It was developed using a sandwich method, where the SMS fiber was positioned as a core layer of the sandwich composite. This core layer was then sandwiched and hot pressed by two layers of EFB fiber mats. The sandwich composite panel in this study was developed at five different variation of fiber ratio (100 SMS: 0 EFB, 80 SMS: 20 EFB, 60 SMS: 40 EFB, 40 SMS: 60 EFB, and 0 SMS: 100 EFB) with an average targeted density of 0.8 g/cm3. The fabricated composite panel samples were cut and stored in the conditioning room for 24 h before testing. A few examples of sandwich composite panels produced after hot pressing and the appearance of the fiber distribution on a composite surface are shown in Figure 2a,b, respectively.

2.2.3. Fourier Transformation Infrared (FTIR)

The chemical composition of the SMS and EFB fibers was identified using FTIR analysis by the presence of functional groups using a Nicole infrared spectrophotometer (Avatar 360 FTIR ESP) analyzer. Low transmittance in the FTIR graph was indicated as a higher amount of light being absorbed during the analysis, which eventually generated a high intensity of the functional group. The functional group was presented in the range of 4000 cm−1 and 470 cm−1 with a resolution of 4 cm−1 [19].

2.2.4. Soxhlet Extraction Analysis

The chemical composition was quantified using the Soxhlet extraction method. Two type of samples (SMS fiber and EFB fiber) were analyzed in this section. The process was divided into five stages, starting with hot water-soluble content, extractives content, lignin removal, cellulose and hemicellulose content, and lignin content. The analysis of hot water-soluble content extraction was performed based on the American Society for Testing and Materials (ASTM) D1110-84 standard method [20], with slight modifications as described in a prior work by [21]. The hot water-soluble content was calculated using Equation (1). The fiber was then dried and used at the next stage of the extraction process.
HWS c =   W b −   W a W i   ×   100
where HWSc is the total percentage of hot water-soluble content extracted from the fiber, %; Wb is the weight of fiber before extraction, g; Wa is the weight of fiber after extraction, g; and Wi is the initial weight of fiber before extraction, g.
Next in the extractives content analysis procedure, the fiber was taken from previous hot water-soluble content samples. The method was conducted using the ASTM D1107–96 standard method [22]. The extractive content was calculated using Equation (2).
E c = W d e OD   ×   100  
where Ec is the total percentage of extractive in the fiber, %; Wde is the weight of dried extractive obtained in the experiment, g; and OD is the oven dry weight of the fiber, g.
In the lignin removal process, the fiber sample from extractives content was used. This step is necessary to measure the cellulose and hemicellulose content in fiber. It was carried out according to the ASTM D1104-56 standard method [23] and followed previous studies [24]. The measurement of cellulose and hemicellulose content in fiber used the method based on ASTM 1695-77 [25] and followed previous studies [26]. The cellulose content was measured based on oven dry weight of fiber samples using Equation (3). The percentage of hemicellulose content was calculated using Equation (4) based on the remaining cellulose content [24].
  C c = W e   OD   ×   100
where Cc is the total percentage of cellulose in the fiber, %; We is the weight of extracted fiber, g; and OD is the oven dry weight of the fiber, g.
H o − C c = H c
where Ho is the total percentage of holocellulose in the fiber, %; Cc is the total percentage of cellulose in the fiber, %; and Hc is the total percentage of hemicellulose in the fiber, %.
For the lignin content measurement, the fiber sample used in this stage was taken from fiber-free extractives content samples. The method used was based on the ASTM D1106–96 standard method [27]. The percentage of lignin collected was calculated using Equation (5).
  L c = W l OD     ×   100  
where Lc is the total percentage of lignin in the fiber, %; Wl is the weight of lignin extracted from the fiber, g; and OD is the oven dry weight of the fiber, g.

2.2.5. Thermogravimetric Analysis

The thermal degradation temperature of the fiber was carried out using a thermogravimetric analyzer (Perkin Elmer model YGA-7). Two types of samples (SMS fiber and EFB fiber) were analyzed in this section. The sample decomposition was studied under a heating rate of 20 °C min−1 under the nitrogen atmosphere. The thermal degradation temperatures of the fiber sample from 30 to 800 °C were plotted in graphic form.

2.2.6. Thermal Conductivity Measurement

The sandwich composite panel thermal conductivity measurement was carried out based on the transient plane source (TPS) thermal characterization method [28]. There were five types of composite samples tested in this section. The thermal conductivity of the sandwich composite panel samples was measured using a hot disk thermal constant analyzer TPS 2500. This instrument measured the thermal conductivity of a given sample according to the steady-state method. Its principal was that by measuring the temperature gradient and the power input and following the ASTM C1045-07 standard [29], one can calculate the thermal conductivity value.

2.2.7. Thermal Measurement

The thermal measurement of the sandwich composite panel was carried out following the method in a previous study by Hassanin [30]. There were five types of composite samples tested in this section. The thermal resistance was calculated based on thermal conductivity values obtained from the TPS 2500 measurement data [31]. Equation (6) expresses the thermal resistance formulation [30].
    R = l   k
where R is indicated as thermal resistance, m2K/W; l is referred to thickness of composite panel, m; and k is referred to thermal conductivity, W/mK.

2.2.8. Thermal Diffusivity Analysis

Thermal diffusivity analysis of the sandwich composite panel was calculated based on data obtained from the thermal conductivity measurement, specific heat capacity value, and sandwich composite density. The thermal diffusivity of the sandwich composite panel was carried out based on following method by Abubakar [32]. Five types of composite samples were tested in this section. In this work, the thermal conductivity and specific heat capacity values were obtained from TPS 2500 measurement data. The measurement was carried out based on the transient plane source (TPS) thermal characterization method [28]. The thermal diffusivity value of a composite panel was calculated by dividing the thermal conductivity with density and specific heat capacity, as shown in Equation (7) [32].
      α = k ρ C p  
where α; is indicated as thermal diffusivity, mm2/s; k is indicated as thermal conductivity, W/mK; ρ is composite panel density, kg/m3; and Cp is composite panel specific heat value, MJ/m3K.

2.2.9. Density Profile Measurement

The density profile through the thickness of the sandwich composite panel followed the method used in a previous study [33]. Five types of composite samples were tested in this section. The density profile was determined by using scanning X-ray radiation transmitted at scan speed 0.25 mm/s. The scanning was carried out using a DA-X density profiler with an accuracy of 0.25%.

2.2.10. Mechanical Testing

The evaluation of the sandwich composite panel flexural strength was carried out through three-point bend testing as shown in Figure 3, specified in JIS A5908 (2003) [34]. Five types of composite samples were tested in this section. Five replicated samples from each composite ratio were prepared. The span length was set up at 120 mm, and the speed of the crosshead was set at 10 mm/min based on the standard.
F c = 3 P L 2 b t 2
where Fc is the flexural strength of composite sample, MPa; P is the maximum load, N; L is span length, mm; b is width of the composite sample, mm; and t is the thickness of composite sample, mm.

2.2.11. Physical Testing

The water absorption of the sandwich composite panel was analyzed according to JIS A5908 (2003) [34]. Five types of composite samples were tested in this section. Five replicated samples from each composite ratio were prepared. All samples were immersed 30 mm below the water surface for 24 h. Weights of the samples were measured using digital weight balance with accuracy ± 0.0001 g.
W a b s = W b c   −   W a c W i c   ×   100  
where Wabs is the total percentage of water absorption of composite panel, %; Wbc is the weight of composite panel before water immersion, g; Wac is the weight of composite panel after water immersion, g; and Wic is the initial weight of composite panel, g.

3. Results and Discussion

3.1. Chemical Composition Analysis

3.1.1. Fourier Transformation Infrared (FTIR) Analysis

Figure 4 shows the chemical composition of SMS fiber and EFB fiber using the FTIR approach. The figure shows the chemical composition of SMS and EFB fibers was analyzed based on the intensity of the functional group, which is illustrated in terms of the O–H peak, C–H peak, C=O peak, C=C peak, and C–O–C peak. It was revealed that the O–H peaks for SMS and EFB fibers had similar trends and intensities. In relation to the C–H peaks, the results indicated that a strong intensity of the EFB fiber was present, while the intensity of the SMS fiber was slightly lower. For the C=O peak, it showed both SMS and EFB fibers had a similar trend and intensity. For the C=C and C–O–C peaks, the SMS fiber showed a similar intensity trend to the EFB fiber. From the overall results, it was revealed that the chemical compositions of both fibers were almost similar.
In Figure 4, the strong absorption band at the fingerprint area 3200 to 3600 cm−1 and the small absorption band at 1000 to 1200 cm−1 were clear indications of the stretching hydroxyl group (O–H) and the vibration of the glycosidic bond (C–O–C) of cellulose and hemicellulose, respectively. The strong and broad peak intensities of hydroxyl are indicated as higher amounts of cellulose and hemicellulose content in the fiber. However, the slight degradation on the glycosidic bond of the SMS fiber also indicates that a small degradation occurred on cellulose and hemicellulose in the fiber. For the fingerprint areas at 2800 to 3000 cm−1 and 1371 to 1427 cm−1, the peak corresponded to the cellulose (C–H) stretching. Based on the strong intensities of the O–H, C–O–C, and C–H peaks that occurred on SMS and EFB fiber samples, it was indicated that the cellulose composition in the fiber was high [35]. Studies reported that cellulose and hemicellulose play essential roles in providing strength to the natural fiber and contribute to produce a composite panel with excellent properties [36]. For the fingerprint area of 1650 to 1740 cm−1, the C=O peak was attributed to the stretching in the acetyl, carbonyls, and ester group of the hemicellulose [37]. The indication of lignin was shown clearly at the peaks at 1442 to 1612 cm−1 [38]. The trends for both sample peaks looked similar but still had a slight difference in intensity. The low peak of the C=C peak intensities of the SMS fiber was presumed due to lignin degradation, which occurred when it was used as a mushroom substrate.

3.1.2. Soxhlet Extraction Analysis

Figure 5 shows the average percentage of chemical composition in SMS and EFB fibers based on hot water-soluble content, extractives content, cellulose content, hemicellulose content, and lignin content. Results showed that the average percentages of hot water-soluble content of the EFB fiber were the highest at 22%, while those for SMS fiber were 17.74%. For extractive content, the average value for the EFB fiber was 3.12%, while that for the SMS fiber was 3.01%. The cellulose content of the EFB fiber was found to be the highest at 44.93%, while that for the SMS fiber was slightly lower at 33.46%. The hemicellulose content of the EFB fiber was 18.13%, and that for the SMS fiber was higher at 20.69%. For lignin content, the EFB fiber was obtained as 11.82%, while that for the SMS fiber was higher at 25.1%. Overall, it was revealed that the EFB fiber had higher lignocellulose content than the SMS fiber except for hot water-soluble content.
The changes of the chemical composition in the SMS were affected by the sterilization process using the heating treatment and enzymatic reaction where the hemicellulose and cellulose in the SMS fiber underwent chemical degradation, which led them to break down into a small monomer of sugar. Studies reported that this process was crucial in order to generate the nutrients and increase the absorption efficiency of the mushroom for their growing process [39]. A study by Lui [40] stated that when the rate of nutrient uptake by the mushroom is low, it will remain as hot water-soluble content. The study also indicated that this action might occur due to a few environmental factors, such as high indoor temperature, lower humidity, and contamination of green mold. Therefore, it can be assumed that the increase in hot water-soluble content in the SMS fiber could be due to the environmental factors, which cause less productivity of the mushrooms to perform efficient nutrient absorption during their growing process [41].
Overall, although the degradation of the lignocellulose component may lead to reduction of the fiber strength and affect the composite properties, it has been reported that the hot water-soluble content could provide an extra advantage to provide and increase the efficiency of self-bonding between fibers in the composite [42]. In this analysis, it was revealed that the chemical degradation that occurred in the SMS fiber did not seem at par with that of the EFB fiber. However, from this perspective, the SMS and EFB fibers are still deemed suitable and relevant for fabrication into sandwich composite panels for potential green thermal insulation since the average chemical composition was within the range of the other types of natural waste fibers used to produce composites thermal insulation such as coconut fiber [43], sugarcane bagasse [14], and rubber wood fiber [44].

3.2. Thermal Analysis

3.2.1. Thermogravimetric Analysis

The initial degradation temperature (TIN), mass loss (%) at TIN, major weight loss region, and major degradation temperature range (T) are among the crucial physical properties of interest for insulation materials. Figure 6 and Table 1 show the thermal degradation pattern of SMS and EFB fibers at heating temperatures from 30 to 800 °C. The figure shows that the ranges of thermal degradation of the weight loss curves for the SMS and EFB fibers were 30 to 550 °C. The weight loss curve of the fibers was divided into three stages, in which the first stage occurred in the temperature range between 30 and 100 °C, followed by the second stage in the range of 230 to 390 °C and the third stage in the range of 390 to 550 °C.
In the first stage, a slight reduction of weight loss that occurred in the SMS and EFB fibers was due to the evaporation of moisture in the fiber [45]. Studies indicated that the moisture absorption into the fiber corresponded to the presence of the hydroxyl group attached on the backbone of cellulose and hemicellulose in the fiber [46]. In the overall trend profile in this stage, both the fibers exhibited similar weight losses. Next, at the second stage, the SMS and EFB fibers started to degrade at temperatures of 282.23 °C and 309.39 °C, respectively, corresponding to TIN. At this TIN, the SMS and EFFB fiber samples lost 56.24% and the EFB fiber sample lost 72.70% of their original weights. The drastically decreased weight loss curve for all samples occurred due to the decomposition of hemicellulose content in the fiber [47]. In addition, at this stage, previous studies reported that the decrease in weight loss for the samples also corresponded to the degradation of cellulose in the fiber [48].
In the third stage, the presence of lignin in the fiber remained and only started to degrade when reaching 390 °C [49]. Compared with other lignocellulose components, lignin contains an aromatic ring resulting in a longer extended period and higher temperature required to ensure that the degradation is complete, which was seen to occur in stage three. In addition, studies also indicated that at this stage, the decomposition of hydrocarbon that formed during polysaccharide degradation in stage two also occurred [50]. From this analysis, it can be concluded that thermal degradation for the SMS and EFB fibers has a similar trend to the weight loss degradation, and this occurs similarly for all fibers at each stage. Particularly, all the fibers began to undergo lignocellulose degradation above 230 °C. The TIN for the SMS and EFB fibers was a very high temperature, one not yet realized for any building insulation material during the normal application period. Therefore, it was indicated that the SMS and EFB fibers are considered suitable for use as building insulating material.

3.2.2. Thermal Conductivity (k)

Figure 7 shows the effect of the SMS and EFB fiber ratio on the composite panel thermal conductivity. From the figure, it can be seen that the thermal conductivity of the composite panels ranged from 0.231 to 0.310 W/(mK). The lowest thermal conductivity was obtained by the sandwich composite sample made of 100 SMS: 0 EFB, whereas the composite sample made of 0 SMS: 100 EFB had the greatest thermal conductivity. Thermal conductivity fluctuated with increasing EFB fiber ratio in the composite.
The main factor that influenced the changes of the thermal conductivity value of the composite was the existence of the void, void gap reduction, and elimination of void in the composite panel. Therefore, it could be that the inconsistent values of the thermal conductivity of this study as illustrated in Figure 7 could be due to the varied forms of void structure in the sandwich composite panel generated during the hot press process [51]. The composite made from fine fiber particles could contribute to the formation of a small void structure. The small void influenced the composite to achieve a low thermal conductivity value by reducing the heat flow when passing through the composite panel [52]. This explained the fact that when the composite sample was made from fine fiber particle alone, which was 100 SMS: 0 EFB fiber, the thermal conductivity was the lowest value of all the sandwich composite panel samples.
Moreover, the number of void formations and void gap reduction also can be influenced by increasing the composite density, which more likely occurred during the composite manufacturing process [53]. It should be kept in mind that in this research, the overall sandwich composite panel density was set using the same targeted density, which was 0.8 g/cm3. However, the compression effect of the hot press caused the density of the SMS fiber in the core layer and the EFB fiber in the face layer of the sandwich composite panel to become variable and distinct for each layer [54]. This compression mechanism on the composite face and core layers can be observed through density profile analysis. Technically, each sandwich composite panel sample in the present study was produced with the same bulk density, but the density distribution within the face and core layers was different. This condition occurred because of a few factors such as the bulky effect of fiber, fiber particle size, and fiber moisture content.
When comparing the composite panel samples made of 100 SMS: 0 EFB and 80 SMS: 20 EFB, the thermal conductivity value had undergone incremental changes of 0.017 W/(mK) when the 20% ratio of the EFB fiber was increased in the composite. This increment value occurred due to the small portion of small void structure provided by the SMS fiber in the sandwich composite panel being decreased and replaced by the large void structure provided by 20% of the EFB fiber in the composite panel [55]. However, when the EFB fiber ratio was added up to 40%, the thermal conductivity once again decreased. At this point, it was assumed that the bulky structure of the EFB fiber at the face layer probably had begun to experience a higher compression effect and undergone an incremental change in density at the face layer of the sandwich composite panel [56]. As a result, the void structure provided by the EFB fiber at the face layer becomes smaller, and thereby the thermal conductivity value at ratio of 60 SMS: 40 EFB decreased.
Meanwhile, the thermal conductivity was then increased when the EFB fiber ratio in the sandwich composite panel was raised to 60%. This was because when the EFB fiber ratio increased, the fiber at the face layer of the sandwich composite panel became more plentiful and thicker owing to its increased volume, increasing the compression effect. This action resulted in the density at the face layer becoming extremely densified. Instead of reducing on the void size, higher compression effect had caused the fiber at the face layer to undergo a greater fiber contact and led to the elimination of the void structure. At this phase, the heat transfer through the composite was more likely to change from convection to conduction, where the heat movement had become faster and was initiated through the solid particle [57]. Therefore, this mechanism explained the increasing thermal conductivity value of the sandwich composite panel when the EFB fiber ratio was high [17].
As it was claimed that the changes in thermal conductivity were influenced by variable distribution of density on the sandwich composite panel, the density profile analysis was considered crucial. The density profile analysis was carried out as supporting data in investigating the compression effect of the EFB fiber at the sandwich composite panel face layer as shown in Figure 8. By this analysis, the compression effect of the EFB fiber during the hot press that led to increased density in composite panel can be examined in more detail through the composite thickness. The figure shows that the pattern of the obtained profile occurred from a smooth U-shaped to a steep V-shaped profile. The U-shaped profile was obtained at the sandwich composite panel sample made of 80 SMS: 20 EFB, and the V-shaped profile was obtained at the sandwich composite panel sample made of 40 SMS: 60 EFB. From the overall results, the density profile of the sandwich composite panel became gradually steeper with an increasing EFB fiber ratio.
It was observed that the changes of the profile pattern from a U shape to a V shape occurred when the EFB fiber ratio in the sandwich composite panel was increased. The formation of a steeper density profile occurred due to the density of the EFB fiber at the face layer being higher than the SMS fiber at the core layer, which was affected by the compression effect during the hot press [58]. Theoretically, the primary mechanism of the composite formation during the hot press process was initiated by the reduction of void structure between fiber particles. In this matter, the reduction of void in the EFB fiber seemed to be greater than that in the SMS fiber. This was because the bulky effect of the EFB fiber tended to have more void as it also was affected and created by a random distribution of the fiber network during fiber mat forming [59]. Based on Figure 8, this compression effect on the face layer could be seen clearly in the density profile where the U shape was gradually turned into a V shape when the EFB fiber ratio in the sandwich composite panel increased from 20 to 60%. In relation to the thermal conductivity analysis, the analysis of the density profile of the sandwich composite panel was consistent with the theory in which the higher compression on the sandwich composite panel face layer was affected by a higher ratio of the EFB fiber and influenced the elimination void structure, causing the thermal conductivity of sandwich composite panel to increase.

3.2.3. Thermal Resistance (R)

Figure 9 shows the effect of the SMS and EFB fiber ratio on the sandwich composite panel thermal resistance. From the figure, it can be seen that the thermal resistance ranged from 0.0194 to 0.0260 m2K/W. The highest thermal resistance was obtained by the sandwich composite panel made of 100 SMS: 0 EFB, while the lowest thermal resistance was obtained by the sandwich composite panel made of 0 SMS: 100 EFB. From the overall composite results, the thermal resistance fluctuated with increasing EFB fiber ratio in the sandwich composite panel.
It can be seen that the thermal resistance of the sandwich composite panel had an opposite trend to the previous thermal conductivity value. The thermal resistance of an insulation panel was inversely proportional to the thermal conductivity value if the thicknesses among the panels were similar. On the contrary, when composite panels had similar thermal conductivity values, the composite panel with highest thickness obtained the highest thermal resistance [60]. However, as the sandwich composite panels in the present study had similar thicknesses, this condition was neglected. In this analysis, it can be concluded that the changes in thermal resistance of a sandwich composite panel affected by the formation of void structures had the same mechanism with thermal conductivity, although both values were inversely proportional. As previously mentioned, this condition was obtained due to the thicknesses of the sandwich composite panels being similar.

3.2.4. Thermal Diffusivity (α)

Table 2 shows the effect of the SMS and EFB fiber ratio on the sandwich composite panel thermal diffusivity. From the table, it can be seen that the range of thermal diffusivity was from 0.2665 to 0.3855 mm2/s. The lowest thermal diffusivity was obtained by the composite panel sample made of 80 SMS: 20 EFB, while the highest thermal diffusivity was obtained by the sandwich composite panel sample made of 0 SMS: 100 EFB. It was revealed that the thermal diffusivity was increasing with increasing EFB fiber ratio in the sandwich composite panel. In addition, the specific heat capacity of the sandwich composite panel shown in the table was fluctuating with increasing EFB fiber ratio without showing any specific trend.
The thermal diffusivity value of the composite was influenced by the specific heat capacity and thermal conductivity of the composite. The specific heat capacity is described as the amount of energy required to raise a unit of mass by one degree of temperature [61]. In this study, the increasing specific heat capacity of the sandwich composite panel was due to the increasing density at the face layer affected by the increasing EFB fiber ratio. The increased specific heat capacity necessitated a greater amount of heat energy to be transferred throughout the sandwich composite panel volume [62]. As a result, the thermal diffusivity of the sandwich composite panel became lower. Table 2 also shows that the thermal diffusivity was also influenced by the thermal conductivity value of the sandwich composite panel. This was due to the thermal diffusivity value being proportional to the thermal conductivity and inversely proportional to the specific heat capacity with the sandwich composite panel density. Therefore, it can be concluded that the lower thermal diffusivity of the sandwich composite panel could be achieved by increasing the specific heat capacity higher than the thermal conductivity value.

3.3. Mechanical Properties

Flexural Strength of the Sandwich Composite Panel

Figure 10 shows the effect of the SMS and EFB fiber ratio on the sandwich composite panel flexural strength. From the figure, it can be seen that flexural strength ranging from 6.18 to 26.47 MPa was recorded. Based on the evaluation result, it was revealed that the flexural strength of the composite made of 100 SMS: 0 EFB was obtained at 6.18 MPa, followed by 80 SMS: 20 EFB (15.61 MPa), 60 SMS: 40 EFB (16.21 MPa), 40 SMS: 60 EFB (23.62 MPa), and 0 SMS: 100 EFB (26.47 MPa). From the overall results, the flexural strength was increasing significantly by a p-value < 0.0001 with an increasing EFB fiber ratio in the composite.
Based on Figure 10, the increasing flexural strength with a higher ratio of EFB fiber could be due to the increasing degree of the fiber network in the sandwich composite panel. The increasing degree of the fiber network in the sandwich composite was affected by the geometrical structure of the EFB fiber, which is a long and stranded structure. The longer fiber geometrical structures were able to form stronger reinforcement by forming fiber particle overlaps, fiber entanglement, and fiber interlock, which led to an increase in the degree of the fiber network in the sandwich composite panel [63]. This condition increased the efficiency of internal stress transfer from one particle to another in the composite. Hence, it was reported that longer fiber particles also could provide an advantage in reducing the amount of defects in the sandwich composite panel by preventing and reducing the initial failure site that occurred during composite load testing.
Moreover, the improvement of the flexural strength could also be due to the increment of the sandwich composite panel’s compressibility, which was affected by the low density and bulky structure of the EFB fiber. When the ratio of the EFB fiber was high, the compressibility of the fiber in the face layer of the sandwich composite panel also increased. As a result, it modified the face layer at the sandwich composite panel surface to become more compacted. This explained the fact that when a higher EFB fiber ratio was used, the face layer became dense and robust, which resulted in improving the flexural strength of the sandwich composite panel.
To obtain a clear understanding of the influence of the fiber geometrical structure toward improving the degree of the fiber network in the sandwich composite panel, a comparison analysis on the breakage structure analysis between the composite panel samples made of 100 SMS: 0 EFB and SMS: 100 EFB is presented in Figure 11. It can be seen that the sandwich composite panel sample made of 100 SMS: 0 EFB had higher breakage failure where the composite structure was completely detached. This condition was consistent with the theory in which a higher ratio of fine fiber particles had caused less efficiency of load distribution and became easily broken due to the low degree of the fiber network formed in the composite panel.
Meanwhile, the physical structure of the sandwich composite panel sample made of 0 SMS: 100 EFB still remained attached. This showed that a higher fiber length of the EFB fiber did contribute to increasing the degree of the fiber network by forming multiple fiber particle overlaps and influenced the increase in the flexural strength of the sandwich composite panel. It can be concluded that the addition of the EFB fiber had acted as a reinforcement material, which had influenced the improvement of the flexural strength of the sandwich composite panel.

3.4. Physical Properties

Water Absorption of the Sandwich Composite Panel

Figure 12 shows the effect of the SMS and EFB fiber ratio on the sandwich composite panel water absorption. From the figure, it can be seen that the recorded water absorption ranged from 106.33 to 166.63%. The lowest water absorption was obtained by the sandwich composite panel sample made of 100 SMS: 0 EFB with an average value of 106.33%, while the sandwich composite panel sample made of 0 SMS: 100 EFB with an average value of 166.63% exhibited the maximum water absorption. From the overall results, the water absorption was increasing significantly by a p-value < 0.0001 with an increasing EFB fiber ratio in the composite.
The increasing water absorption of the sandwich composite panel was due to the presence of void structure in the composite panel [64]. Technically, the void in the composite was formed due to low uniformity of fiber distribution and poor fiber packing in the sandwich composite panel [65]. The primary factor that influenced the initiation of this condition was the geometrical structure of the EFB fiber, which has a long and stranded structure [66]. Generally, the presence of void was responsible for allowing the penetration of water molecules into the sandwich composite panel.
Another factor that influenced the increasing water absorption in the sandwich composite was the low dimensional stability of the sandwich composite panel. Particularly, the fiber particle bonding in the sandwich composite panel was bonded only by hydrogen bonding [67]. When exposed to wet conditions, these hydrogen bonds were disrupted and vanished. The disappearance of the hydrogen bonding loosened the fiber arrangement triggering the swelling effect, which led to creating more void opening in the sandwich composite panel cavities. As a result, the amount of water that penetrated the sandwich composite panel increased.
In addition, the water absorption of the composite was technically also influenced by both the SMS and EFB fibers due to the ability of the fiber itself to store a substantial amount of water. This was because both fibers possessed amorphous cellulose structure allowing them to absorb water molecules, which contributed to individual fibers swelling and also resulted in an increasing rate of water absorption in the composite. In a comparison between the SMS and EFB fibers, the EFB fiber has the highest fiber swelling effect. This is because the cellulose component in the EFB fiber is much greater than that in the SMS fiber, whereby a greater amount of amorphous structure is present in the EFB fiber. Moreover, the SMS fiber might possess lower swelling effect due to degradation of the amorphous structure that occurred during its use as mushroom substrate.
It can be inferred that raising the EFB fiber ratio improved the mechanical properties, but it also caused poor physical properties of the sandwich composite panel. In contrast, the sandwich composite panel made of a larger proportion ratio of SMS fiber was considerably more preferred since it retained the sandwich composite panel physical structure. This was because the SMS fiber had fine particles that were able to contribute to improving fiber packing and eventually reducing the void structure in the sandwich composite panel. It can be concluded that using a higher ratio of fine fiber particle size is considered one of the mechanisms that are able to increase the water-resistance properties by reducing the amount of water that penetrates into the sandwich composite panel.
In this analysis, the influence of increasing the EFB fiber ratio could be observed clearly by comparing the images of the sandwich composite panel samples made of 100 SMS: 0 EFB, 60 SMS: 40 EFB, and 0 SMS: 100 EFB as shown in Figure 13. The figure shows that the spring-back effect of the sandwich composite panel samples made with a higher EFB fiber ratio underwent greater thickness swelling. This concluded that although the previous analysis found that the addition of EFB fiber had resulted in the improvement of the mechanical properties of the sandwich composite panel, in this section, it was revealed that it also provided poor physical properties to the sandwich composite panel.

4. Conclusions

Spent mushroom substrate (SMS) fiber and empty fruit bunch (EFB) fiber, abundant forms of natural waste fiber, were utilized here to develop a green thermal insulation panel. The aim was to develop a more environmentally friendly green material for use as thermal insulation that could be implemented in building applications. Therefore, some limitations should be highlighted during the fabrication process. The efficiency of green thermal insulation is heavily dependent on its properties and thermal characteristics, which are determined by a variety of typical factors such as the material’s density, porosity, and moisture content. Therefore, the insulation panel has limitations to manipulate these factors as it is bound by the fabrication method. For example, the composite mixing compounding method and the addition of a binder have required the composite to obtain a high-density and low-porosity structure in order to provide sufficient mechanical strength properties. Technically, the binder was used in the composite as an adhesive to bind the fiber particles and to increase the degree of the fiber network making the composite robust. However, the binder was not meant to be utilized in the development of green thermal insulation panels owing to the elimination of air voids in the composite, which might impair the thermal performance of the insulation panel. In addition, by implementing the sandwich method, the composite fabrication process involves a three-fiber layering process that has a significant impact by increasing the mechanical properties without reducing the thermal characteristic of the composite panel. Therefore, the development and investigation of green thermal insulation panels through a sandwich method fabrication process was conducted.
In this work, the FTIR and Soxhlet extraction data revealed that the chemical compositions of the SMS and EFB fibers, such as hot water-soluble content, cellulose, hemicellulose, and lignin, were found to be still deemed suitable and relevant for fabrication into the sandwich composite panel. The TGA data showed that both the SMS and EFB fibers had similar weight loss multi-stage patterns at temperatures ranging from 30 °C to 100 °C, 230 °C to 390 °C, and 390 °C to 550 °C. The thermal degradations of the SMS and EFB fibers are considered suitable for use as building insulating materials during the normal application period. The thermal conductivity and thermal resistance were improved as the EFB fiber ratio rose by 40% and decreased by increasing it to 60%. Meanwhile, the thermal diffusivity decreased with a 20% EFB fiber ratio and further increased with 40% and greater EFB fiber ratios. The analysis of the density profile was consistent with the proposed theory as stated in the thermal conductivity analysis, where the higher compression on the sandwich composite panel face layer was affected by a higher ratio of the EFB fiber and influenced the elimination void structure causing the thermal conductivity value to become higher. The prepared sandwich composite panel has a flexural strength of 15.61 to 23.62 MPa and water absorption at range of 106.33 to 166.63%. In the present study, the sandwich composite panel made of 60 SMS: 40 EFB was selected as the best ratio. The selection of the sandwich composite panel with this ratio was carried out based on the properties and thermal performance data toward potential green thermal insulation. An insulation panel does not require higher properties as long as it can provide an adequate thermal performance. Therefore, thermal performance takes precedence in the choosing of the sandwich composite panel. However, it is also important to consider the mechanical properties of a composite panel as it should be able to resist the least amount of load feasible when utilized in any insulation application. In the present study, the sandwich composite panel made of 60 SMS: 40 EFB exhibited the highest thermal performance. Moreover, it also showed an optimum value of composite flexural strength among other samples. So it becomes preferable to be selected as the best ratio for the present study.

Author Contributions

Conceptualization, M.A.S., M.I.A. and Y.Y.; methodology, M.A.S. and M.I.A.; validation, Y.Y. and M.R.; writing—original draft preparation, M.A.S.; writing—review and editing, M.I.A., Y.Y., S.M.W., M.R.S., M.A. and M.R.; supervision, M.I.A., Y.Y. and M.R.; project administration, M.I.A.; funding acquisition, M.I.A. and M.R. All authors have read and agreed to the published version of the manuscript.

Funding

The authors are grateful for the FRGS research grant scheme (FRGS/1/2016/TK07/USM/02/1). The authors are grateful to the Researchers Supporting Project Number (RSP2023R326), King Saud University, Riyadh, Saudi Arabia.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Acknowledgments

The authors are grateful for graduate assistance (GA) and thank the School of Industrial Technology, Universiti Sains Malaysia, Penang. The authors are grateful to the Researchers Supporting Project Number (RSP2023R326), King Saud University, Riyadh, Saudi Arabia.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Antov, P.; Savov, V.; Neykov, N. Utilization of Agricultural Waste and Wood Industry Residues in the Production of Natural Fiber- Reinforced Composite Materials. Int. J. Wood Des. Technol. 2018, 6, 64–71. [Google Scholar]
  2. Mortada, A.N.; Bolhassan, M.H.; Wahi, R. Physicochemical Composition of Spent Oyster Mushroom Substrate. Malays. J. Anal. Sci. 2020, 24, 848–854. [Google Scholar]
  3. Onoja, E. Oil Palm (Elaeis guineensis) Biomass in Malaysia: The Present and Future Prospects. Waste Biomass Valorization 2019, 10, 2099–2117. [Google Scholar] [CrossRef]
  4. Yiin, C.L. Recovery of Cellulose Fibers from Oil palm Empty Fruit Bunch for Pulp and Paper using Green Delignification Approach. Bioresour. Technol. 2019, 290, 121797. [Google Scholar] [CrossRef] [PubMed]
  5. Hamzah, N.; Tokimatsu, K.; Yoshikawa, K. Solid Fuel from Oil Palm Biomass Residues and Municipal Solid Waste by Hydrothermal Treatment for Electrical Power Generation in Malaysia: A Review. Sustainability 2019, 11, 1060. [Google Scholar] [CrossRef] [Green Version]
  6. Rajavat, A.S.; Rai, S.; Pandiyan, K.; Kushwaha, P. Sustainable Use of the Spent Mushroom Substrate of Pleurotus florida for Production of Lignocellulolytic Enzymes. J. Basic Microbiol. 2020, 60, 173–184. [Google Scholar] [CrossRef] [PubMed]
  7. Najafi, B.; Faizollahzadeh, S.; Shamshirband, S.; Chau, K.W. Spent Mushroom Compost (Smc) as a Source for Biogas Production in Iran. Eng. Appl. Comput. Fluid Mech. 2019, 13, 967–982. [Google Scholar] [CrossRef] [Green Version]
  8. Wan, W.A.; Peng, W.; Nam, W.L.; Yang, H. A Review on Valorization of Oyster Mushroom and Waste Generated in the Mushroom Cultivation Industry. J. Hazard. Mater. 2020, 400, 123156. [Google Scholar]
  9. Ariff, I.N.M.; Bahrin, E.K.; Ramli, N.; Abd-Aziz, S. Direct Use of Spent Mushroom Substrate from Pleurotus pulmonarius as a Readily Delignified Feedstock for Cellulase Production. Waste Biomass Valorization 2019, 10, 839–850. [Google Scholar] [CrossRef]
  10. Owodunni, A.A.; Lamaming, J.; Hashim, R.; Taiwo, O.F.A. Adhesive Application on Particleboard from Natural Fibers: A Review. Polym. Compos. 2020, 41, 4448–4460. [Google Scholar] [CrossRef]
  11. Khoo, S.C.; Peng, W.X.; Yang, Y.; Ge, S.B. Development of Formaldehyde-Free Bio-Board Produced from Mushroom Mycelium and Substrate Waste. J. Hazard. Mater. 2020, 400, 123296. [Google Scholar] [CrossRef] [PubMed]
  12. Grimm, D.; Wosten, H.A.B. Mushroom Cultivation in the Circular Economy. Appl. Microbiol. Biotechnol. 2018, 102, 7795–7803. [Google Scholar] [CrossRef] [Green Version]
  13. Thyavihalli, Y.G.; Mavinkere Rangappa, S.; Parameswaranpillai, J.; Siengchin, S. Natural Fibers as Sustainable and Renewable Resource for Development of Eco-Friendly Composites: A Comprehensive Review. Front. Mater. 2019, 6, 226. [Google Scholar] [CrossRef]
  14. Ramlee, N.A.; Naveen, J.; Jawaid, M. Potential of Oil Palm Empty Fruit Bunch (Opefb) and Sugarcane Bagasse Fibers for Thermal Insulation Application—A Review. Constr. Build. Mater. 2020, 271, 121519. [Google Scholar] [CrossRef]
  15. Sair, S.; Mandili, B.; Taqi, M.; El Bouari, A. Development of a New Eco-Friendly Composite Material Based on Gypsum Reinforced with a Mixture of Cork Fibre and Cardboard Waste for Building Thermal Insulation. Compos. Commun. 2019, 16, 20–24. [Google Scholar] [CrossRef]
  16. Rebolledo, P.; Cloutier, A.; Yemele, M.-C. Effect of Density and Fiber Size on Porosity and Thermal Conductivity of Fiberboard Mats. Fibers 2018, 6, 81. [Google Scholar] [CrossRef] [Green Version]
  17. Ferrandez, A.; Ortuno, T.; Ferrandez-Garcia, C. Influence of Particle Size on the Properties of Boards Made from Washingtonia Palm Rachis with Citric Acid. Sustainability 2020, 12, 4841. [Google Scholar] [CrossRef]
  18. Iswanto, A.H.; Ompusunggu, P.L. Sandwich Particleboard (Spb): Effect of Particle Length on the Quality of Board. IOP Conf. Ser. Earth Environ. Sci. 2019, 374, 012002. [Google Scholar] [CrossRef]
  19. Ghodake, V.; Khare, R.; Mhaske, S. An Insight into Formation and Characterization of Nano-Cellulose Prepared from Industrial Cellulosic Wastes. J. Polym. Environ. 2022, 30, 319–332. [Google Scholar] [CrossRef]
  20. ASTM D1110-84; Standard Test Methods for Water Solubility of Wood. ASTM International: West Conshohocken, PA, USA, 2013.
  21. Franko, B.; Carlqvist, K.; Galbe, M.; Lidén, G. Removal of Water-Soluble Extractives Improves the Enzymatic Digestibility of Steam-Pretreated Softwood Barks. Appl. Biochem. Biotechnol. 2018, 184, 599–615. [Google Scholar] [CrossRef] [Green Version]
  22. ASTM D1107-96; Standard Test Method for Ethanol-Toluene Solubility of Wood. ASTM International: West Conshohocken, PA, USA, 2001.
  23. ASTM D1104-56; Standard Method of Test for Holocellulose in Wood. ASTM International: West Conshohocken, PA, USA, 1977.
  24. Alvarez, A.; Cachero, S.; Gonzalez, C.; Montejo-Bernardo, J. Novel Method for Holocellulose Analysis of Non-Woody Biomass Wastes. Carbohydr. Polym. 2018, 189, 250–256. [Google Scholar] [CrossRef]
  25. ASTM 1695-77; Standard Method of Test for Cellulose and Cellulose Derivatives. ASTM International: West Conshohocken, PA, USA, 2007.
  26. Gadzama, S.W.; Sunmonu, O.; Isiaku, U.; Danladi, A. Isolation and Characterization of Nanocellulose from Pineapple Leaf Fibres Via Chemo-Mechanical Method. Sci. World J. 2020, 15, 100–105. [Google Scholar]
  27. ASTM D1106-96; Standard Test Method for Acid-Insoluble Lignin in Wood. ASTM International: West Conshohocken, PA, USA, 2007.
  28. Zheng, Q.; Kaur, S.; Dames, C.; Prasher, R.S. Analysis and Improvement of the Hot Disk Transient Plane Source Method for Low Thermal Conductivity Materials. Int. J. Heat Mass Transf. 2020, 151, 119331. [Google Scholar] [CrossRef] [Green Version]
  29. ASTM C1045-07; Standard Practice for Calculating Thermal Transmission Properties Under Steady-State Conditions. ASTM International: West Conshohocken, PA, USA, 2013.
  30. Hassanin, A.H.; Candan, Z.; Demirkir, C.; Hamouda, T. Thermal Insulation Properties of Hybrid Textile Reinforced Biocomposites from Food Packaging Waste. J. Ind. Text. 2018, 47, 1024–1037. [Google Scholar] [CrossRef]
  31. Adeogun, S.O.; Adebayo, O.A.; Ose, M.O.; Abiona, B.G. Information and Training Needs of Cotton Farmers on Their Farming Activities in Zambia. Sci. Pap. Manag. Econ. Eng. Agric. Rural. Dev. 2019, 19, 9–16. [Google Scholar]
  32. Abubakar, M.; Raji, A.; Hassan, M. Comparative Study of Thermal Insulation Boards from Leaf and Bark Fibres of Camel’s Foot (Piliostigma thonningii L.). Niger. J. Technol. 2018, 37, 108–114. [Google Scholar] [CrossRef] [Green Version]
  33. Hunt, J.F.; Leng, W.; Tajvidi, M. Vertical Density Profile and Internal Bond Strength of Wet-Formed Particleboard Bonded with Cellulose Nanofibrils. Wood Fiber Sci. 2017, 49, 1–11. [Google Scholar]
  34. JIS A 5908 2003; Japanese Industrial Standard for Particleboards. Japanese Industrial Standards: Tokyo, Japan, 2003.
  35. Salim, R.M.; Asik, J.; Sarjadi, M.S. Chemical Functional Groups of Extractives, Cellulose and Lignin Extracted from Native Leucaena leucocephala Bark. Wood Sci. Technol. 2021, 55, 295–313. [Google Scholar] [CrossRef]
  36. Yang, J.; Ching, Y.C.; Chuah, C.H. Applications of Lignocellulosic Fibers and Lignin in Bioplastics: A Review. Polymers 2019, 11, 751. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  37. Parre, A.; Karthikeyan, B.; Balaji, A.; Udhayasankar, R. Investigation of Chemical, Thermal and Morphological Properties of Untreated and Naoh Treated Banana Fiber. Mater. Today 2020, 22, 347–352. [Google Scholar] [CrossRef]
  38. Zhu, Z.; Mo, B.; Hao, M. Study of Contents Ratio of Cellulose, Hemicellulose and Lignin on the Mechanical Properties of Sisal Fibers Reinforced Polylactic Acid (Pla) Composites. IOP Conf. Ser. Mater. Sci. Eng. 2019, 544, 012012. [Google Scholar] [CrossRef]
  39. Nurfitri, N.; Mangunwardoyo, W.; Saskiawan, I. Lignocellulolytic Enzyme Activity Pattern of Three White Oyster Mushroom (Pleurotus Ostreatus (Jacq.) P. Kumm.) Strains during Mycelial Growth and Fruiting Body Development. J. Phys. Conf. Ser. 2021, 1725, 012056. [Google Scholar] [CrossRef]
  40. Lui, F.H.Y.; Kurokochi, Y.; Narita, H.; Saito, Y. The Effects of Chemical Components and Particle Size on the Mechanical Properties of Binderless Boards Made from Oak (Quercus spp.) Logs Degraded by Shiitake Fungi (Lentinula edodes). J. Wood Sci. 2018, 64, 246–255. [Google Scholar] [CrossRef] [Green Version]
  41. Bellettini, M.B.; Fiorda, F.A.; Maieves, H.A.; Teixeira, G.L. Factors Affecting Mushroom Pleurotus spp. Saudi J. Biol. Sci. 2019, 26, 633–646. [Google Scholar] [CrossRef] [PubMed]
  42. Boon, J.G.; Hashim, R.; Danish, M.; Nadhari, W.N.A.W. Physical and Mechanical Properties of Binderless Particleboard Made from Steam-Pretreated Oil Palm Trunk Particles. J. Compos. Sci. 2019, 3, 46. [Google Scholar] [CrossRef] [Green Version]
  43. Owodunni, A.A.; Lamaming, J.; Hashim, R.; Taiwo, O.F.A. Properties of Green Particleboard Manufactured from Coconut Fiber Using a Potato Starch Based Adhesive. Bioresources 2020, 15, 2279–2292. [Google Scholar] [CrossRef]
  44. Sungsee, P.; Tanrattanakul, V. Biocomposite Foams from Poly (Lactic Acid) and Rubber Wood Sawdust: Mechanical Properties, Cytotoxicity, and in Vitro Degradation. J. Appl. Polym. Sci. 2019, 136, 48259. [Google Scholar] [CrossRef]
  45. Radzi, A.M.; Sapuan, S.M.; Jawaid, M.; Mansor, M.R. Water Absorption, Thickness Swelling and Thermal Properties of Roselle/Sugar Palm Fibre Reinforced Thermoplastic Polyurethane Hybrid Composites. J. Mater. Res. Technol. 2019, 8, 3988–3994. [Google Scholar] [CrossRef]
  46. Supian, M.A.F.; Amin, K.N.M.; Jamari, S.S.; Mohamad, S. Production of Cellulose Nanofiber (Cnf) from Empty Fruit Bunch (Efb) Via Mechanical Method. J. Environ. Chem. Eng. 2020, 8, 103024. [Google Scholar] [CrossRef]
  47. Wang, J.; Wang, B.; Liu, J.; Ni, L. Effect of Hot-Pressing Temperature on Characteristics of Straw-Based Binderless Fiberboards with Pulping Effluent. Materials 2019, 12, 922. [Google Scholar] [CrossRef] [Green Version]
  48. Asim, M.; Paridah, M.T.; Chandrasekar, M.; Shahroze, R.M. Thermal Stability of Natural Fibers and Their Polymer Composites. Iran. Polym. J. 2020, 29, 625–648. [Google Scholar] [CrossRef]
  49. Zhang, N.; Tao, P.; Lu, Y.; Nie, S. Effect of Lignin on the Thermal Stability of Cellulose Nanofibrils Produced from Bagasse Pulp. Cellulose 2019, 26, 7823–7835. [Google Scholar] [CrossRef]
  50. Alharbi, M.A.H.; Hirai, S.; Tuan, H.A.; Akioka, S. Effects of Chemical Composition, Mild Alkaline Pretreatment and Particle Size on Mechanical, Thermal, and Structural Properties of Binderless Lignocellulosic Biopolymers Prepared by Hot-Pressing Raw Microfibrillated Phoenix Dactylifera and Cocos Nucifera Fibers and Leaves. Polym. Test. 2020, 84, 106384. [Google Scholar]
  51. Goncalves, M.; Simões, N.; Serra, C.; Flores-Colen, I. A Review of the Challenges Posed by the Use of Vacuum Panels in External Insulation Finishing Systems. Appl. Energy 2020, 257, 114028. [Google Scholar] [CrossRef]
  52. Abu, B.; Mourad, A.H.; Hittini, W.; Hassan, M. Traditional, State-of-the-Art and Renewable Thermal Building Insulation Materials: An Overview. Constr. Build. Mater. 2019, 214, 709–735. [Google Scholar]
  53. Barkhad, M.S.; Abu-Jdayil, B.; Iqbal, M.Z.; Mourad, A.H.I. Thermal Insulation Using Biodegradable Poly (Lactic Acid)/Date Pit Composites. Constr. Build. Mater. 2020, 261, 120533. [Google Scholar] [CrossRef]
  54. Benthien, J.T.; Ohlmeyer, M. Effects of Flat-Shaped Face Layer Particles and Core Layer Particles of Intentionally Greater Thickness on the Properties of Wood-Reduced Particleboard. Fibers 2020, 8, 46. [Google Scholar] [CrossRef]
  55. Boribayeva, A.; Zharbossyn, A.; Berkinova, Z.; Yermukhambetova, A. Packing Structure of Binary Particle Compacts with Fibers. IOP Conf. Ser. Mater. Sci. Eng. 2020, 829, 012020. [Google Scholar] [CrossRef]
  56. Parlato, M.; Porto, S. Organized Framework of Main Possible Applications of Sheep Wool Fibers in Building Components. Sustainability 2020, 12, 761. [Google Scholar] [CrossRef] [Green Version]
  57. Muthuraj, R.; Lacoste, C.; Lacroix, P.; Bergeret, A. Sustainable Thermal Insulation Biocomposites from Rice Husk, Wheat Husk, Wood Fibers and Textile Waste Fibers: Elaboration and Performances Evaluation. Ind. Crops Prod. 2019, 135, 238–245. [Google Scholar] [CrossRef] [Green Version]
  58. Hussein, Z.; Ashour, T.; Khalil, M.; Bahnasawy, A. Rice Straw and Flax Fiber Particleboards as a Product of Agricultural Waste: An Evaluation of Technical Properties. Appl. Sci. 2019, 9, 3878. [Google Scholar] [CrossRef] [Green Version]
  59. Kadivar, M.; Gauss, C.; Ghavami, K.; Savastano, H. Densification of Bamboo: State of the Art. Materials 2020, 13, 4346. [Google Scholar] [CrossRef] [PubMed]
  60. Cai, Z.; Al Faruque, M.A.; Kiziltas, A.; Mielewski, D. Sustainable Lightweight Insulation Materials from Textile-Based Waste for the Automobile Industry. Materials 2021, 14, 1241. [Google Scholar] [CrossRef]
  61. Shafigh, P.; Asadi, I.; Mahyuddin, N.B. Concrete as a Thermal Mass Material for Building Applications—A Review. J. Build. Eng. 2018, 19, 14–25. [Google Scholar] [CrossRef]
  62. Shahedan, N.F.; Abdullah, M.; Mahmed, N.; Kusbiantoro, A. Thermal Insulation Properties of Insulated Concrete. Rev. Chim. 2019, 70, 3027–3031. [Google Scholar] [CrossRef]
  63. Setyawan, P.; Sugiman, S.; Lingkar, A. Effect of Bamboo Fiber Length in Opened Cell Foam Core Sandwich Composite on Water Absorption and Their Mechanical Properties. AIP Conf. Proc. 2018, 1977, 030021. [Google Scholar]
  64. Kusmono; Hestiawan, H.; Jamasri. The Water Absorption, Mechanical and Thermal Properties of Chemically Treated Woven Fan Palm Reinforced Polyester Composites. J. Mater. Res. Technol. 2020, 9, 4410–4420. [Google Scholar] [CrossRef]
  65. Mohamed, W.Z.W.; Baharum, A.; Ahmad, I.; Abdullah, I. Effects of Fiber Size and Fiber Content on Mechanical and Physical Properties of Mengkuang Reinforced Thermoplastic Natural Rubber Composites. Bioresources 2018, 13, 2945–2959. [Google Scholar] [CrossRef]
  66. Halip, J.A.; Hua, L.S.; Tahir, P.M.; Al Edrus, S.S. Kenaf and Kenaf-Rubberwood Hybrid Particleboards. Int. J. Recent Technol. Eng. 2019, 8, 464–468. [Google Scholar]
  67. Yunus, N.Y.; Kasim, J.; Yusof, N.; W.A.Rahman, W.M.N. Effects of Particle Sizes and Board Densities on Opf Phenol Formaldehyde Particleboard Properties. In Regional Conference on Science, Technology and Social Sciences (RCSTSS 2016); Springer: Singapore, 2018; pp. 777–786. [Google Scholar] [CrossRef]
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Figure 1. (a) Appearance of spent mushroom substrate (SMS) fiber block and (b) SMS fiber sample disintegration process.
Figure 1. (a) Appearance of spent mushroom substrate (SMS) fiber block and (b) SMS fiber sample disintegration process.
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Figure 2. (a) Finished samples of sandwich composite panel and (b) surface appearance of sandwich composite panel.
Figure 2. (a) Finished samples of sandwich composite panel and (b) surface appearance of sandwich composite panel.
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Figure 3. Three-point bending testing on the sandwich composite panel sample.
Figure 3. Three-point bending testing on the sandwich composite panel sample.
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Figure 4. The FTIR trend peaks and intensity on each functional group to indicate chemical composition in the SMS, FRS, and EFB fibers.
Figure 4. The FTIR trend peaks and intensity on each functional group to indicate chemical composition in the SMS, FRS, and EFB fibers.
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Figure 5. The average percentage of chemical composition (hot water-soluble content, extractives, cellulose, hemicellulose, and lignin) for the SMS and EFB fibers using the Soxhlet extraction method.
Figure 5. The average percentage of chemical composition (hot water-soluble content, extractives, cellulose, hemicellulose, and lignin) for the SMS and EFB fibers using the Soxhlet extraction method.
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Figure 6. Thermal degradation trends of the TG profile of the SMS and FRS fibers in three stages.
Figure 6. Thermal degradation trends of the TG profile of the SMS and FRS fibers in three stages.
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Figure 7. The effect of the SMS and EFB fiber ratio against the thermal conductivity of the sandwich composite panel.
Figure 7. The effect of the SMS and EFB fiber ratio against the thermal conductivity of the sandwich composite panel.
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Figure 8. Density profile of the sandwich composite panel at different fiber ratios.
Figure 8. Density profile of the sandwich composite panel at different fiber ratios.
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Figure 9. Effect of the fiber ratio of SMS and EFB fiber on the thermal resistance of the sandwich composite panel.
Figure 9. Effect of the fiber ratio of SMS and EFB fiber on the thermal resistance of the sandwich composite panel.
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Figure 10. Effect of the fiber ratio of SMS and EFB fibers on the flexural strength of the sandwich composite panel.
Figure 10. Effect of the fiber ratio of SMS and EFB fibers on the flexural strength of the sandwich composite panel.
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Figure 11. Examples of specimens after the flexural test. (a) Composite panel made from 100 SMS: 0 EFB and (b) composite panel made from 0 SMS: 100 EFB.
Figure 11. Examples of specimens after the flexural test. (a) Composite panel made from 100 SMS: 0 EFB and (b) composite panel made from 0 SMS: 100 EFB.
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Figure 12. Effect of the fiber ratio of SMS and EFB fiber on the water absorption of the sandwich composite panel.
Figure 12. Effect of the fiber ratio of SMS and EFB fiber on the water absorption of the sandwich composite panel.
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Figure 13. Examples of specimens after water absorption test. (a) Composite panel made from 100 SMS: 0 EFB, (b) sandwich composite panel made from 60 SMS: 40 EFB, and (c) composite panel made from 0 SMS: 100 EFB.
Figure 13. Examples of specimens after water absorption test. (a) Composite panel made from 100 SMS: 0 EFB, (b) sandwich composite panel made from 60 SMS: 40 EFB, and (c) composite panel made from 0 SMS: 100 EFB.
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Table
Table 1. Thermal degradation analysis of the SMS and EFB fibers.
Table 1. Thermal degradation analysis of the SMS and EFB fibers.
Thermal PropertySMS FiberEFB Fiber
Initial degradation temperature at (TIN) (°C)282.23309.39
Mass loss (%) at (TIN)56.2472.70
Major degradation temperature range (°C)282.23–325.75309.39–366.77
Maximum degradation temperature (Tmax)339.12346.13
Table
Table 2. Thermal conductivity, specific heat capacity, and thermal diffusivity of the sandwich composite panel at different SMS and EFB fibers ratios.
Table 2. Thermal conductivity, specific heat capacity, and thermal diffusivity of the sandwich composite panel at different SMS and EFB fibers ratios.
SMS:EFB Fiber RatioThermal Conductivity (W/mK)Specific Heat Capacity (MJ/m3K)Thermal Diffusivity (mm2/s)
100 SMS: 0 EFB0.2310.7490.3855
80 SMS: 20 EFB0.2481.1630.2665
60 SMS: 40 EFB0.2341.0090.2898
40 SMS: 20 EFB0.2891.2150.2973
0 SMS: 100 EFB0.311.2020.3223
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MDPI and ACS Style

Shakir, M.A.; Ahmad, M.I.; Yusup, Y.; Wabaidur, S.M.; Siddiqui, M.R.; Alam, M.; Rafatullah, M. Sandwich Composite Panel from Spent Mushroom Substrate Fiber and Empty Fruit Bunch Fiber for Potential Green Thermal Insulation. Buildings 2023, 13, 224. https://doi.org/10.3390/buildings13010224

AMA Style

Shakir MA, Ahmad MI, Yusup Y, Wabaidur SM, Siddiqui MR, Alam M, Rafatullah M. Sandwich Composite Panel from Spent Mushroom Substrate Fiber and Empty Fruit Bunch Fiber for Potential Green Thermal Insulation. Buildings. 2023; 13(1):224. https://doi.org/10.3390/buildings13010224

Chicago/Turabian Style

Shakir, Mohammad Aliff, Mardiana Idayu Ahmad, Yusri Yusup, Saikh Mohammad Wabaidur, Masoom Raza Siddiqui, Mahboob Alam, and Mohd Rafatullah. 2023. "Sandwich Composite Panel from Spent Mushroom Substrate Fiber and Empty Fruit Bunch Fiber for Potential Green Thermal Insulation" Buildings 13, no. 1: 224. https://doi.org/10.3390/buildings13010224

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