Effect of recycling and bio‐filler addition on the mechanical, thermal, and morphological behavior of the injection molded flax/PLA green composite

Abstract This study explores the mechanical, thermal, and morphological behavior of polylactic acid (PLA) composites reinforced with flax fiber (FF) during recycling. The influence of the addition of bio‐filler (w/w) on the recycling of FF/PLA composites was also analyzed. The recycling influencing the performance of FF/PLA composite was compared with that of halloysite nanotube (HNT)/FF‐PLA composites. The FF/PLA and HNT/FF‐PLA composited were fabricated by injection molding subjected to multiple recycling. The tensile and flexural properties of both composites were assessed after each recycling. Fractured specimens of the recycled samples were analyzed using a scanning electron microscope to study their morphology. Thermal degradation was evaluated through thermogravimetric analysis of the recycled FF/PLA and HNT/FF‐PLA samples. After the fifth recycling process, the HNT/FF‐PLA composite experienced a decrease in tensile strength by 75.01% and flexural strength by 59.88%. The performance of FF/PLA and HNT/FF‐PLA composites was detrimentally affected due to the thermal deterioration of flax fiber and the subsequent decrease in fiber length resulting from repeated reprocessing. The highest degradation for non‐recycled FF/PLA and HNT/FF‐PLA samples occurred at temperatures of 354°C and 347°C, respectively. Whereas the maximum degradation for recycled cellulose (RC)‐5 (fifth recycled) FF/PLA and HNT/FF‐PLA composite occurred at 328 and 327°C. Highlights Adding 1% HNT increased the tensile and flexural strength by 12.5% and 1.79%. The behavior of the composites was affected by the thermal degradation of FF. The maximum degradation of RC‐5 FF/PLA composite occurred at 327°C. The maximum degradation for RC‐5 HNT/FF‐PLA composite was noticed at 328°C.