Polylactide-Based Renewable Green Composites from Agricultural Residues and Their Hybrids

Abstract

Agricultural natural fibers like jute, kenaf, sisal, flax, and industrial hemp have been extensively studied in green composites. The continuous supply of biofibers in high volumes to automotive part makers has raised concerns. Because extrusion followed by injection molding drastically reduces the aspect ratio of biofibers, the mechanical performance of injection molded agricultural residue and agricultural fiber-based composites are comparable. Here, the use of inexpensive agricultural residues and their hybrids that are 8-10 times cheaper than agricultural fibers is demonstrated to be a better way of getting sustainable materials with better performance. Green renewable composites from polylactide (PLA), agricultural residues (wheat straw, corn stover, soy stalks, and their hybrids) were successfully prepared through twin-screw extrusion, followed by injection molding. The effect on mechanical properties of varying the wheat straw amount from 10 to 40 wt % in PLA-wheat straw composites was studied. Tensile moduli were compared with theoretical calculations from the rule of mixture (ROM). Combination of agricultural residues as hybrids is proved to reduce the supply chain concerns for injection molded green composites. Densities of the green composites were found to be lower than those of conventional glass fiber composites.

Twin-screw extrusion impact on natural fibre morphology and material properties in poly(lactic acid) based biocomposites

“…Variations in used values for this theoretical melting enthalpy could be found ranging from 93 to 93.7 J/g in two of the previously reported works (Tokoro et al, 2008;Nyambo et al, 2010).…”

“…9). This phenomenon was imputed in previous works to a reduced chain mobility (Nyambo et al, 2010;Sreekumar et al, 2010) and resulted from the steric hindrance caused by fibre dispersion on polymer chain motion, as well as the slight crystallinity increase mentioned above. Indeed, mobility of polymer chain organized in crystallites was even more reduced.…”

“…Nevertheless, fibres and PLA have different densities, what could cause volume variations in the die depending on the fibre/polymer ratio. Natural fibre density is usually higher than PLA one (Nyambo et al, 2010) so adding more fibre should reduce matter volume. But a rod expansion was observed at the die exit and was a clue of trapped air into the blend while mixing was done.…”

“…Fibres coming from wood (Huda et al, 2006;Sykacek et al, 2010), flax (Oksman et al, 2003), hemp (Masirek et al, 2007), kenaf (Ogbomo et al, 2009) and jute (Plackett, 2004) have been tested among others. Lezak et al (2008) and Nyambo et al (2010) also studied the incorporation of various agricultural residues. From these studies, it was revealed that the fibre type has a real importance on composite performance.…”

Flexural Properties of Wheat Straw Reinforced Polyester Composites

“…It is shown from the literature that the research on wheat straw reinforced composites is quite limited [2][3][4][5]. Mishra and Sain [4] explored the advantages and commercial viability of using wheat straw as filler for thermoplastic composites.…”