Hybrid green composites of PLA incorporated with upcycled waste cellulose and vermiculite

Abstract

The work aims to utilize a hybridization method where vermiculite and waste cellulose fibers are embedded inside bio-based PLA to manufacture green composites with superior characteristic properties such as improved thermal conductivity, enhanced processability, and increased mechanical strength in the resulting green composites. The potential of polymeric composites for emerging greener material development is very high. Originating from this point, this article reports the experimental findings on a hybrid composite reinforcement strategy where two types of renewable materials are employed as co-reinforcement agents in a biodegradable polylactic acid (PLA) matrix. Green composite sample manufacturing was performed via high shear mixing (5000 rpm). Composite samples containing waste cellulose fibers (WC), (average diameter: 15 µm) and vermiculite platelets (VC), (average size: 1.4milimeters) as inclusions and a low crystallinity thermoplastic PLA matrix are targeted. Two-phase composites having 10, 20,30 wt% WC, 30 wt% VC, and hybrid composites having 15VC-15WC wt. % and 7.5VC-22.5WC wt. % are manufactured. Composite samples are then tested for their thermal, rheological, and mechanical responses. Thermal analysis suggests that thermal conductivity is improved by 68 % for PLA30VC samples and in hybrid composites, thermal conductivity is regulated by WC, while crystallinity is regulated by VC. Rheological measurements suggest both filler materials contribute to the processability of PLA, and hybrid composites are more readily processable than neat PLA at 200 °C. While the tensile strength remains the same in all composites, a 137 % increase in E modulus and 127 % increase in flexural modulus is achieved with hybrid composites. The damage modes and contribution of both inclusion types to macro and micro fracture mechanisms are discussed in detail. Overall, results suggested that a stronger, easily processable, and thermally more conductive yet stable superior material alternative could only be achieved by the synergistic use of WC fibers and VC platelets.