Development of high void fraction polylactide composite foams using injection molding: Mechanical and thermal insulation properties

Polylactide (PLA) and PLA composites with void fractions as high as 65% were fabricated using low-pressure foam injection molding (FIM) and high-pressure FIM (HPFIM) equipped with mold opening and gas counter pressure. The cellular morphology and crystallinity were characterized using scanning electron microscopy and differential scanning calorimetry, respectively. The mechanical (flexural and impact resistance) and thermal insulation properties were also measured. Unlike, talc, the addition of nanoclay markedly enhanced the ductility of solid PLA samples as well as significantly improved the cell morphology of foamed samples, which resulted in the increased specific modulus, strength and impact resistance. In all the PLA samples made using HPFIM, with an increased void fraction up to 55%, the flexural rigidity increased up to four times, the specific impact resistance increased up to 15%, and the thermal insulation increased up to three times. The results of this investigation revealed that low-density PLA composite foams with improved rigidity, impact strength, and thermal insulation can be developed using HPFIM for various applications such as transportation and construction industries.