In this article, we report the effects of hybridization and fiber-surface modification on the properties of hybrid composites prepared from recycled polypropylene (RPP), coupling agents, oil palm empty fruit bunch (EFB), and glass fibers through a twinscrew extruder and an injection-molding machine. The surface of the EFB fibers was modified with different concentrations (10-15 wt %) and temperatures (60-908C) of alkali solutions. The structure and morphology of the fibers were observed with the help of Fourier transform infrared spectroscopy and scanning electron microscopy. Different types of composites were fabricated with untreated, alkali-treated, and heat-alkali-treated fibers. Comparative analysis of the mechanical, structural, morphological, and thermal properties of the composites was carried out to reveal the effects of treatment and hybridization. The analysis results reveal that composites prepared from the alkali-treated (in the presence of heat) fibers show improved mechanical, thermal, and morphological properties with a remarkably reduced water absorption. Additionally, the crystallinity of RPP also increased with the development of biaxial crystals. The improvement of various properties in relation to the structures and morphologies of the composites is discussed.

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Composites were prepared from recycled polypropylene (RPP), oil palm empty fruit bunch (EFB) and/or glass fibre (GF) using extrusion and injection moulding techniques. Two types of maleic anhydride-grafted polypropylene such as Polybond 3200 and Fusabond P 613 were used to improve the interfacial adhesion between fibres and matrix. The EFB: GF ratio was fixed as 70:30 and fibre loading was considered as 40 wt%. Microwave was used to treat the EFB fibre, which was soaked in a fixed mass concentration (12.5%) of alkali solution at different temperatures (70, 80 and 90°C) for a fixed period of time (60 min) and for different times (60, 90 and 120 min) at a fixed temperature (90°C). A magnetron controller was developed to control the time and temperature accurately for the treatment of fibre. Various characterization techniques such as density, melt flow index, tensile, Izod impact, flexural, field-emission scanning electron microscopy and water uptake testing were performed for the composites. Besides, thermogravimetric analysis and differential scanning calorimetry were also used to evaluate the thermal and crystalline properties of the composites, respectively. Result analyses revealed that microwave-treated fibre-based composites showed improved mechanical and thermal properties. EFB fibres treated at 90°C for 90 min were found to be suitable for better reinforcement into the composite in terms of mechanical, thermal and crystalline properties. Moreover, onset degradation temperature and water absorption properties were also found to be changed apparently due to treatment.

Abstract Glass fiber (GF) and ultrasound-treated oil palm empty fruit bunch (EFB) were used to prepare recycled polypropylene (RPP)-based hybrid composites through the extrusion and injection molding technique. The ultrasound technique was used to remove the lignin and other surface impurities from the EFB fiber by varying the treatment conditions (treatment time and temperature). A fixed concentration (10%) of NaOH solution was used as the treatment medium. Fiber loading was considered as 40%, while EFB and GF ratio was maintained as 70:30. Two types of coupling agents of maleic anhydride grafted PP (MAPP), Polybond and Fusabond, were used, each of an amount 2.5% (of the total fiber content), to improve the interfacial adhesion between fibers and matrix. Composites were characterized through density, melt flow index (MFI), tensile, flexural and Izod impact testing. In addition, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) were also performed to evaluate the thermal and morphological properties, respectively. X-ray diffraction (XRD) analysis was performed to evaluate the crystalline structure of the samples. Finally, water uptake (WU) measurement was performed for 180 days of soaking period. Result analyses revealed improved mechanical, thermal and crystalline properties, with reduced WU as the outcome of treatment and coupling agent effects.

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