Microwave-assisted alkali treatment of sisal fiber for fabricating composite as non-structural building materials

Abstract

Currently, the world needs sustainable materials to replace and minimize the use of synthetic materials in order to reuce environmental pollution. In this context, natural fiber-reinforced composites (NFRCs) are in high demand. However, the low thermal and mechanical properties have limited their application spectrum. The current research investigation explores the effectiveness of alkali treatment and microwave-assisted alkali treatment (MAAT) on sisal fiber and sisal/high-density polyethylene (HDPE) composites. The MAAT was performed at three different power levels (300, 640 and 800 W) and treatment time was kept constant (10 min); the power level was optimized based on the fiber’s performance. The chemical analysis of treated fibers showed an increased ratio of cellulose percentage in the fibers when compared to untreated fibers. The MAAT (at 640W10) showed improvement in the thermal stability of sisal fiber as compared to untreated and alkali treated fibers. The single fiber test showed the highest (21.92% and 45.77%) increase in tensile strength for MAAT (at 640W10) as compared to alkali treated and untreated sisal fibers, respectively. Scanning electron microscopy (SEM) showed the effectiveness of the MAAT (at 640W10) in terms of a more uniform surface roughness on the fiber surface. The research also focused on using time efficient microwave-assisted molding (MAM) method for the fabrication of NFRCs. Vector network analyzer (VNA) was used to determine the dielectric constant of the fibers as it plays a critical role in heat generation during microwave heating. Mechanical, X-ray diffraction (XRD) and thermogravimetric analysis (TGA) tests were performed on the fabricated composites. It was observed that the MAAT sisal fiber (at 640 W) reinforced HDPE composites (640W10/HDPE) had recorded the best performance as they showed increased thermal stability, percentage crystallinity (3.56% and 10.26%), tensile strength (14.93% and 32.04%) and flexural strength (10.28% and 28.60%) as compared to alkali treated sisal fiber reinforced HDPE composites (NTSF/HDPE) and untreated sisal fiber reinforced HDPE composites (USF/HDPE), respectively. From the results, it is observed that MAAT has strong potential to be commercially employed for the time-efficient treatment of natural fibers before fabricating the sustainable construction components, parts, and products.