Bamboo Fiber Reinforced Chemically Functionalized Acrylonitrile Butadiene Styrene Composites by Palsule Process

ABSTRACT

Bamboo fibers (BBF) and reinforced chemically functionalized acrylonitrile-butadiene-styrene (CF-ABS) composites (BBF/CF-ABS) have been processed up to 190ºC, extending Palsule process to higher processing temperatures. The composites show higher tensile and flexural properties than CF-ABS. BBF act as stress concentrators, reduce deformation and thus impact strength of the composites relative to the matrix. Esterification reaction and hydrogen bonds are formed between BBF and CF-ABS at higher processing temperatures also, and these bonds impart adhesion between them in the composites. Thermal stability of the BBF/CF-ABS composites is between those of BBF and CF-ABS, and their degradation starts above 270ºC. The composites show better mechanical properties than the same composite by the fiber treatment, the compatibilizer and their combined processes.

SUMMARY

• Palsule process has been used for composites requiring lower processing temperatures only.

• The process is extended to higher processing temperatures for bamboo fibers/CF-ABS composites.

• This study establishes fiber/matrix adhesion by the process at higher processing temperatures.

• The composites show higher mechanical properties except impact strength than CF-ABS.

• Shows advantages of Palsule process over fiber treatment and compatibilizer processes.

摘要

竹纤维（BBF）增强的化学官能化丙烯腈-丁二烯-苯乙烯（CF-ABS）复合材料（BBF/CF-ABS）已加工至190ºC，将Palsule工艺扩展至更高的加工温度. 复合材料显示出比CF-ABS更高的拉伸和弯曲性能. BBF充当应力集中器，减少变形，从而降低复合材料相对于基体的冲击强度. 在较高的加工温度下，BBF和CF-ABS之间也会形成酯化反应和氢键，这些键在复合材料中赋予它们之间的粘附力. BBF/CF-ABS复合材料的热稳定性介于BBF和CF-ABS之间，其降解开始于270ºC以上. 通过纤维处理、增容剂及其组合工艺，复合材料显示出比相同复合材料更好的机械性能.

KEYWORDS:

• Bamboo fiber/CF-ABS composite
• Palsule process
• fiber/matrix adhesion
• morphology
• mechanical properties
• thermal analysis

关键词:

• 竹纤维/CF-ABS复合材料 过程
• 纤维/基质粘附
• 形态学
• 机械性能
• 热分析

Introduction

Eco-friendly and sustainable natural fibers (NF) offer good properties and therefore are being used for several applications, including for composites for ballistic applications (Nayak et al. 2022), as reinforcements for geopolymer composites, for example, those based on fly ash, (Furtos et al. 2021a, 2021b) developed as an alternative to Portland cement, and mainly as reinforcements for polymer composites, in place of synthetic and inorganic fibers. NF-reinforced polymer composites have good properties, several applications and also support agro-based economy. The recent literature reviews describe their processing and sustainability (Manral et al. 2021), performance, properties, applications and future potential (Rangappa et al. 2022) and also the recent progress (Kannan and Thangaraju 2021). Performance of a NF/polymer composite is dependent upon the characteristics of the polymer and the fiber, their relative amounts and also the orientation and the aspect ratio of the reinforcement.

NFs are polar and hydrophilic and polymers are nonpolar and hydrophobic, because of which they have poor interfacial adhesion in their composites, that is being improved by the following three processes: (i) Fiber treatment process imparts treatments to NFs for their adhesion with the matrix and the chemical, physical and biological treatments (Kenned, Sankaranarayanasamy, and Kumar 2021), and microwave radiation treatments (Romero-Zúñiga et al. 2021) to NFs have been reviewed. (ii) Compatibilizer process uses a coupling agent that works as a compatibilizer improving adhesion of NF and the matrix polymer. This process has also been reviewed (Lu, Wu, and McNabb 2000). (iii) Palsule process (Palsule 2007) uses a chemically functionalized polymer as the matrix that develops interfacial adhesion with NF through esterification and hydrogen bonding, and this mechanism has been reviewed recently (Liu et al. 2021). Palsule process has been applied to develop NF-reinforced chemically functionalized (CF) polymer composites based on functionalized polyolefins, CF-PE (Palsule et al. 2013; Singh and Palsule 2014) and CF-PP (Biswas and Palsule 2016; Singh and Palsule 2016), and functionalized thermoplastic elastomers, CF-EPR (Dinesh and Palsule 2020a, 2021) and CF-SEBS (Dinesh and Palsule 2020b). Comparative studies indicate that polypropylene (PP) and also HDPE composites by Palsule process offer better properties than the same PP composites and the same HDPE composite by other processes, as compared in Priyanka and Palsule (2013) and Singh and Palsule (2013), respectively. Expenses for Palsule process are the same as for the fiber treatment process, because of the use of the functionalized polymer in the former and requirement of treatment chemicals and manpower in the latter, but are slightly more than those for compatibilizer process, because only upto 5% compatibilizer is used. Thus, although, Palsule process is preferable because of its composites offering overall techno-economic advantages; however, it has been used for composites requiring lower processing temperatures. Therefore, efforts are now being made for the applicability of Palsule process for composites requiring higher processing temperatures. In view of the successful development of styrene-containing CF-SEBS composites (Dinesh and Palsule 2020b) by Palsule process, for this study, a styrenic polymer, a chemically functionalized acrylonitrile butadiene styrene, ABS grafted with maleic anhydride (CF-ABS), requiring higher processing temperature, has been selected as the matrix and bamboo fibers (BBF) have been selected as reinforcements. ABS offers good properties and several applications (Abdelhaleem et al. 2016). However, only one cellulose-fiber-reinforced ABS composite, based on bleached cellulose fiber, is reported (Fonseca, Waldman, and De Paoli 2021) and limited literature is available on NF/ABS composites as follows: A commercially available wood fibers (WF)-based WF/ABS composite (Porebska et al. 2015) has been studied. Reported NF-reinforced ABS composites by fiber treatment process are based on WF (Yang et al. 2011), pineapple leaf fiber (PALF) (Threepopnatkul et al. 2012, 2013; Threepopnatkul, Krachang, and Kulsetthanchalee 2014) and oil palm fiber (OPF) (Ahmad et al. 2020, 2021; Ong et al. 2019); the ABS composites by compatibilizer process are based on WF (Yang et al. 2011), OPF (Nikmatin et al. 2018; Nikmatin et. al. 2017a) and kenaf fiber (KNF) (Andilolo et al. 2017; Nikmatin et al. 2017b). Bamboo-fibers-based BBF/ABS composites also have been investigated as follows: as a simulated replacement for an ABS-based car window panel (Santoso et al. 2020); BBF grafted with diisocyanate and reacted with a polyol (DI-PO-BBF)-reinforced ABS, DI-PO-BBF/ABS composite filaments for its 3D print specimens (Gama et al. 2021); and BBF/ABS composites by fiber treatment, compatibilizer and their combined processes (Ma et al. 2012). Potential of CF-ABS, maleic-anhydride-grafted ABS, with various percentages of maleic anhydride as matrix has been evaluated for the composites with the following nanomaterials and also fibers as reinforcements: nano-zinc oxide (Olongal et al. 2021) and aramid, carbon and glass fiber fabrics and their layers (Ayten 2021a, 2021b). However, this is the first study using NFs as reinforcements for CF-ABS composites. With approx. 65% holocellulose and approx. 25% lignin, BBF offer high tensile strength (approx. 185 MPa) and modulus (approx. 15 GPa) and other good properties (Faruk et al. 2012) and therefore have been used as reinforcements for several polymer composites. Interfacial bonding mechanism (Liu et al. 2021), mechanical properties (Mousavi et al. 2022) and recent developments (Muhammad et al. 2019) of BBF-reinforced polymer composites have been reviewed. Thus, NF-reinforced CF-ABS composites have not been reported and no ABS composite is reported by Palsule process. Accordingly, the aim of this study is to extend the Palsule process to composites requiring higher processing temperatures, relative to the reported composites by the Palsule process, developed at lower processing temperature, by selecting higher processing temperature requiring chemically functionalized acrylonitrile butadiene styrene (CF-ABS) as the matrix, and BBF as the reinforcements and to develop their BBF/CF-ABS composites, at relatively higher processing temperatures, establish their mutual compatibility and adhesion at higher temperatures, and compare their performance with the same BBF/ABS composite reported by other processes and evaluate the superiority and advantages of Palsule process over the other three processes.

Materials, processing and sample preparation

The BBF/CF-ABS composites have been developed in this study without imparting any treatment to BBF and without using any third component as a coupling agent. Chemically functionalized acrylonitrile butadiene styrene (CF-ABS) (0.8% maleic anhydride grafted ABS) is being used as matrix. It is a commercial product, NG6002 (termed as ABS Impact Modifier, by its supplier Shanghai Jianqiao Plastic Co. Ltd., Shanghai, China). It was supplied as free-flowing granules of light-yellow or off-white color. Figure 1 shows the chemical structure of CF-ABS. Bamboo culms were purchased from local market (Saharanpur, India) and were converted and chopped into approx. 3-mmlength fiber.

Figure 1. Chemically functionalized acrylonitrile butadiene styrene (CF-ABS).

Reinforcing BBF and CF-ABS matrix had been dried separately, first, at 80ºC for 12 hours in an air oven and then at 60ºC for 3 hours in a vacuum oven, and were mixed appropriately to get 10/90, 20/80 and 30/70 BBF/CF-ABS composites. These were extruded in a co-rotating twin screw extruder [Specific Engineering & Automats (ZV 20α), Vadodara, India] of screw diameter of 30 mm and l/d ratio of 40:1, which was operated with 160 rpm with temperatures of five different zones ranging from 155ºC to 190ºC and varying as follows: 155–165–175–185–190ºC. The extruder die temperature was set at 185ºC and melt pressure at 12 bar. Extruded composite compositions were cooled in water, their pellets were dried in an air oven and then molded to obtain their samples by injection molding machine [Electronica Endura 90, Endura Ltd., Pune, India], set at the screw speed of 120 rpm, feed zone and nozzle temperatures of 180ºC and 190ºC, respectively, and the injection and back pressures of 80 bar and 100 bar, respectively.

Testing and characterization

Mechanical properties, morphology and thermal stability of the composites have been evaluated. Tensile and flexural properties of CF-ABS and the BBF/CF-ABS composites have been evaluated as per ASTM D638-14 standard (ASTM D638-14 2014) and ASTM D790-17 standard (ASTM D790-17 2017), respectively, by the UTM (5 kN capacity, Model 3365, Instron, Massachusetts, USA), operated at 23 ± 2ºC with the crosshead speed of 5 mm/min and 2 mm/min, respectively. The size of the samples for tensile tests were as follows: length 165 ± 1 mm, thickness 3.21 ± 0.1 mm, middle width 12.7 mm and width of griping area 19.0 mm; the size of the samples for the flexural tests were as follows: length × width × thickness of 127 ± 3 × 12.71 × 3.21 mm³. Unnotched Izod impact strengths of the materials were tested at 23 ± 2ºC as per the ASTM D4812-19 standard (ASTM D4812-19 2019) by the impact tester (Tinius Olsen 104, Salfords, England, UK), equipped with a nominal pendulum weight 3.77 kg, nominal impact energy 22.6 J, drop height 609.6 mm and impact velocity of 3.46 m/s. The size of the samples for the impact tests were as follows: length × width × thickness of 64 ± 1 × 12.71 × 3.21 mm³, respectively. All the test results are reported as the average of the five samples tested. Morphology of the composites has been examined by aluminum stub mounted and thin layer of gold-coated tensile fractured samples of the composites by field emission scanning electron microscopy (FE-SEM, Mira 3 Tescan, Libusina, Brno, Czech Republic) operated with 5 kV. The interactions creating CF-ABS/BBF adhesion in the composites were established by the FTIR Spectrometer (Perkin Elmer Spectrum Two, Perkin Elmer, Valencia, USA) by using a pellet of the material mixed with KBr and recording the spectrum in the range of 4000–500 cm⁻¹. Thermal stability of the composites and of its constituents has been evaluated by Thermo Gravimetric Analyzer (Discovery 55, TA Instrument, New Castle, USA) following the ASTM E1131-20 standard (ASTM E1131-20 2020). Approximately 10 mg sample for each material was examined in the range of 23–800ºC at heating rate of 10ºC/min in nitrogen flowing at the rate of 200 mL/min.

Results and discussions

Mechanical properties

The tensile stress versus strain graphs for the materials are displayed in Figure 2. Relative to the matrix CF-ABS, the 10/90, 20/80 and 30/70 BBF/CF-ABS composites showed (Table 1) approximately 25%, 34% and 55% higher tensile strength, respectively, and approximately 147%, 238% and 371% higher tensile modulus, respectively, but 68%, 80% and 82% decreased elongation at break, respectively. Literature reports that alkali-treated (AT) banana fiber (BNF)-based 10/90, 20/80 and 30/70 AT-BNF/ABS composites (Kusić et al. 2020) and AT bauhinia vahlii bast fibers (BVF)-based 10/90, 20/80 and 23/77 AT-BVF/ABS composites (Sahu et al. 2022) showed increasing tensile modulus, and the AT-BVF/ABS composites (Sahu et al. 2022) also showed increasing tensile strength, with increasing reinforcing fibers in them. NF-reinforced CF-PE (Singh and Palsule 2013, 2014), CF-PP (Biswas and Palsule 2016; Singh and Palsule 2016), CF-EPR (Dinesh and Palsule 2020a, 2021) and CF-SEBS (Dinesh and Palsule 2020b) composites by Palsule process also showed increasing tensile modulus and strength with increasing NF in them. Similarly, BBF/CF-ABS composites developed by Palsule process in this study also show increasing tensile modulus and increasing tensile strength with increasing BBF contents in them. Relative to the matrix CF-ABS, the 10/90, 20/80 and 30/70 BBF/CF-ABS composites showed (Table 1) approximately 17%, 34% and 50% higher flexural strength, respectively, and approximately 109%, 234% and 417% higher flexural modulus, respectively. Literature reports that the AT-BNF/ABS composites, referred above (Kusić et al. 2020), the AT-BVF/ABS composites, referred above (Sahu et al. 2022), and NF-reinforced CF-PE (Singh and Palsule 2013, 2014) and CF-PP (Biswas and Palsule 2016; Singh and Palsule 2016) composites by Palsule process also showed increasing flexural modulus and strength with increasing reinforcing NF in them. Similarly, BBF/CF-ABS composites developed by Palsule process in this study also show increasing flexural modulus and strength with increasing BBF contents in them. Good fiber/matrix adhesion has adverse effect on impact strength of ABS composites (Speri and Jenkins 1973). Basalt (Abdelhaleem et al. 2016; Abdellah et al. 2018) and bamboo (Ma et al. 2012) fibers-reinforced ABS composites are reported to show lower impact strength than the matrix. Relative to the CF-ABS, the 10/90, 20/80 and 30/70 BBF/CF-ABS composites also show approximately 21%, 34% and 40% lower unnotched Izod impact strengths (Table 1). BBF act as stress concentrators, reduce deformation and thus impact strength of the BBF/CF-ABS composites relative to the matrix. AT-BNF/ABS composites, referred above (Kusić et al. 2020), showed decreasing charpy impact strength and the AT-BVF/ABS composites, referred above (Sahu et al. 2022), also showed decreasing impact strength. Although the NF-reinforced CF-PE (Singh and Palsule 2014) and CF-PP (Biswas and Palsule 2016) composites by Palsule process showed increasing Izod impact strength with increasing reinforcing NF in them, however, the BBF/CF-ABS composites developed in this study by Palsule process show decreasing Izod impact strength, analogous to other literature-reported ABS composites.

Figure 2. Tensile stress versus strain curves of the materials.

Table 1. Tensile, flexural and unnotched Izod impact properties of the materials.

Serial No.	Sample	Tensile Strength (MPa)	Standard Deviation	Tensile Modulus (GPa)	Standard Deviation	Elongation at break (%)	Standard Deviation	Flexural Strength (MPa)	Standard Deviation	Flexural Modulus (GPa)	Standard Deviation	Unnotched Izod Impact Strength (kJ/m^2)	Standard Deviation
1	CF-ABS	44.51	0.261	1.04	0.026	11.37	0.707	76.67	0.245	2.62	0.011	34.51	0.627
2	10/90 BBF/CF-ABS	55.63	0.940	2.57	0.068	3.62	0.217	89.81	0.515	5.47	0.333	27.34	0.910
3	20/80 BBF/CF-ABS	59.69	0.438	3.52	0.200	2.32	0.020	102.84	1.301	8.76	0.448	22.66	1.090
4	30/70 BBF/CF-ABS	68.83	0.819	4.90	0.096	2.04	0.198	115.26	0.488	13.56	0.324	20.55	0.317

During the processing of the composites, there is a possibility of fiber breakage reducing the BBF length relative to their original 3 mm length. BBF/CF-ABS composites demonstrate higher tensile properties than the CF-ABS, and the properties increase with the BBF contents increasing in the composites, indicating that in the final processed composites, the reinforcing BB fibers have retained effective fiber length and also effective aspect (l/d) ratio. Higher tensile and flexural modulus and strengths of BBF/CF-ABS composites, with respect to CF-ABS and their increase with increasing BBF in the composite compositions, establish the formation of the BBF/CF-ABS composites due to good fiber/matrix adhesion that has been investigated by SEM and FTIR as follows.

Morphology and fiber/matrix interactions

FE-SEM images (Figures 3(a–c)) of the tensile fractured BBF/CF-ABS composites, with the reinforcing BBF indicated between the arrows, show relatively increasing BBF contents in the 10/90, 20/80 and 30/70 BBF/CF-ABS composites. These images show the BBF fully covered with and deeply embedded in the CF-ABS matrix, which was also observed to a greater extent in BBF/ABS (SMA) composites and to a limited extent in AT-BBF/ABS composites (Ma et al. 2012). The images of these composites do not show any reinforcing BBF pull-out, unlike reinforcement pull-out visible in BBF/ABS (Ma et al. 2012), OPF/ABS (Ong et al. 2019) and palm-fiber-reinforced PMLF/ABS (Neher et al. 2014) composites. These images show no voids and no gaps between BBF and CF-ABS, as was also the case for BBF/ABS (SMA) composites, but, it is unlike PMLF/ABS composites (Neher et al. 2014) that showed voids. However, some possible fiber breakage during the tensile testing of the composites is observed. All these observations confirm good adhesion of the reinforcing BB fiber with the CF-ABS matrix in all the BBF/CF-ABS composite compositions. This adhesion facilitates stress transfer from the matrix to the reinforcement in the BBF/CF-ABS composites, and improves the tensile properties of the composites, relative to the matrix, as discussed earlier in this report. Chemical interactions imparting this adhesion have been established by FTIR, as follows.

Figure 3. FE-SEM images of (a) 10/90, (b) 20/80, and (c) 30/70 BBF/CF-ABS composites.

FTIR spectroscopy investigated the 20/80 BBF/CF-ABS composite (Figure 4), as all other compositions will show the same results. The FTIR plot of the CF-ABS (Figure 4) indicates peaks at 1452 cm⁻¹ and 759 cm⁻¹ corresponding to bending vibrations of –CH₂ and –CH₃ aliphatic groups, respectively, and at 698 cm⁻¹ representing the rocking vibrations of –CH₂ of the matrix. The peak at 2922 cm⁻¹ is indicative of symmetric and asymmetric C–H alkyl stretch, and the one at 2237 cm⁻¹ is indicative of acrylonitrile. The bands at 1602 cm⁻¹ and 1494 cm⁻¹ appear due to the C=C aromatic stretching. The band at 1780 cm⁻¹ corresponds to the carbonyl (C=O) asymmetric stretching band of the anhydride and thus also indicates grafting of MA onto ABS forming CF-ABS. Reversible hydration reaction forms carboxylate groups of the maleic acid (Figure 5). Fourier transform infrared spectroscopy (FTIR) of the BBF/CF-ABS composite exhibits a characteristic band at 1736 cm⁻¹ (between 1750 cm⁻¹ and 1720 cm⁻¹) that indicates the stretching of C=O of ester group. The other new band at 1115 cm⁻¹ (between 1300 cm⁻¹ and 1100 cm⁻¹) shows C–O of ester group. These two new bands, the 1115 cm⁻¹ and the 1736 cm⁻¹, and also the disappearance of the 1780 cm⁻¹ peak in the composite spectra confirm the esterification reaction. BBF/CF-ABS composites have been processed at higher temperatures, where esterification (as shown in Figure 6) is known to occur with the formation of mono-ester by only one of the two potential acid groups (Rowell et al. 1993) and also with the formation of both mono-ester and di-ester (Matsuda 1987). This has also been observed for BGF/CF-SEBS composites by Palsule process (Dinesh and Palsule 2020b). The 3436 cm⁻¹ band in the composite spectra (Figure 4) indicates hydrogen bonding between the groups of holo-cellulose of BBF and of the MAH of the CF-ABS matrix (Figure 7). The esterification and hydrogen bonding results in BBF/CF-ABS interfacial adhesion in the composite and the same has also been observed in BBF/CF-PP (Biswas and Palsule 2016) and recycled BBF-reinforced, R-BBF/CF-EPR (Dinesh and Palsule 2020a) composites and other NF/polymer composites by Palsule process. This has also been confirmed in a review on NF/polymer composites, addressing fiber/matrix adhesion in bamboo/polymer composites (Liu et al. 2021).

Figure 4. FTIR of CF-ABS matrix and the 20/80 BBF/CF-ABS composite.

Figure 5. Reversible hydration reaction.

Figure 6. Esterification between BBF and CF-ABS forming (a) monoester and (b) diester.

Figure 7. Hydrogen bonding between BBF and CF-ABS.

Comparison of the composites by Palsule process with the composites by other processes

Of the reported BBF/ABS composites, the BBF/CF-ABS composites developed in this study are comparable with the composites reported by Ma et al. (2012) as compared in Table 2: Alkali-treated BBF-based AT-BBF/ABS composites, SMA compatibilizer-based BBF/ABS (SMA) and AT-BBF and SMA-based AT-BBF/ABS (SMA) composites. Table 2 shows that the flexural modulus and the tensile, the flexural, and the unnotched Izod impact strengths of 30/70 BBF/CF-ABS composite developed by Palsule process, in this study, are higher than those of the three other composites by the other three processes. Relative to their matrix, the other composites show lower tensile strength, maximum 13% higher flexural strength, maximum 119% higher flexural modulus and upto 72% lower unnotched Izod impact strength, but the 30/70 BBF/CF-ABS composite shows 55% higher tensile strength, 50% higher flexural strength, 417% higher flexural modulus and only 40% lower unnotched Izod impact strength. Thus, BBF/CF-ABS composites by Palsule process offer techno-economic advantages relative to the same composite by the other three processes.

Table 2. Comparison of the composites by Palsule process with the composites by other processes.

Serial No.	Sample	Tensile Strength (MPa)	% increase (+)/decrease (-) Relative to the Matrix	Flexural Strength (MPa)	% increase (+)/decrease (-) Relative to the Matrix	Flexural Modulus GPa	% increase (+)/decrease (-) Relative to the matrix	Unnotched Izod impact strength (kJ/m^2)	% increase (+)/decrease (-) Relative to the matrix	Source
1	CF-ABS	44.51	NA	76.67	NA	2.62	NA	34.51	NA	From this study
2	30/70 BBF/CF-ABS by Palsule process	68.83	+55	115.26	+50	13.56	+417	20.55	−40	From this study
3	ABS	50	NA	82.50	NA	1.80	NA	40	NA	(Ma et al. 2012)
4	30/70 AT-BBF/ABS by fiber treatment process (alkali treatment)	45	−11	78.10	−6	2.66	+48	9.55	−76	(Ma et al. 2012)
5	30/70 BBF/ABS (SMA) by compatibilizer process with SMA as the compatibilizer	47	−6	87.00	+5	3.24	+80	10.30	−74	(Ma et al. 2012)
6	30/70 AT-BBF/ABS (SMA) by combined fiber treatment and compatibilizer process	49	−2	93.00	+13	3.95	+119	11.30	−72	(Ma et al. 2012)

Thermal analysis

Figures 8(a,b) record the TGA and DTG analysis of the materials. BB fibers show approx. 5% weight loss, between 50°C and 100°C, due to the release of volatile matters and moisture with a DTG peak at 60°C, initiation of degradation at around 246ºC because of the lignocelluloses and other components and the maximum rate of degradation at 334ºC, finally leaving 21.77% residual mass at 800ºC. CF-ABS matrix does not release any volatile matter. It shows the initiation of its degradation around 364ºC, the maximum rate of degradation at 416ºC and, finally, leaves 0.09% residual mass at 800ºC. The initiation of the degradation of the 10/90, 20/80 and 30/70 BBF/CF-ABS composites is noted at 342ºC, 284ºC and 274ºC, respectively, their maximum rate of degradation is at 414ºC, 413ºC and 411ºC, respectively, and they, respectively, leave 4.30%, 7.68% and 8.23% residual mass at 800ºC. Thus, the thermal stability of the composites is in between those of BBF and CF-ABS, and the temperature of initiation of their degradation decreases with increasing BBF contents in the composites, but CF-ABS matrix shows higher thermal stability than the reinforcing BBF and the composites.

Figure 8. (a) TGA curve and (b) DTG curve of BB fiber, CF-ABS matrix and the BBF/CF ABS composites.

Conclusions

BBF/CF-ABS composites, successfully developed at a relatively higher processing temperature, by Palsule process, show higher tensile and flexural properties, than the CF-ABS, that increase with the BB fibers increasing in them, but the composites have lower impact strength than the CF-ABS matrix. Esterification and hydrogen bonding between BBF and CF-ABS impart adhesion between them in the composites. Their thermal stability is in between those of BBF and CF-ABS, but CF-ABS matrix shows higher thermal stability than the reinforcing BBF and the composites. BBF/CF-ABS composites show higher mechanical properties than the same composite by any other process. This study establishes the applicability of Palsule process at higher processing temperatures and also its techno-economic advantages over other processes.

Ethical approval

The authors certify that every component of research adheres with moral standards and adheres by the country of study’s legal regulations. There are no concerns about human or animal welfare in the research.

Acknowledgments

Fellowship of Indian Institute of Technology, Roorkee (India) (Ministry of Education, Govt. of India) to the research scholar Piyush Kumar is thankfully acknowledged.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was supported by the fellowship of Indian Institute of Technology, Roorkee (India) (Ministry of Education, Govt. of India) to the research scholar Piyush Kumar.