Upcycling of waste plastic: value-added sustainable composites from biocarbon-reinforced post-consumer recyclates comprising bale wrap and waste automotive parts

This study reports for the first time a new class of injection molded sustainable composites from a blend of two waste recyclates as matrix and pyrolyzed miscanthus biomass (biocarbon) as a filler. Recycled polypropylene (r-PP) obtained from waste automotive parts and recycled linear low-density polyethylene (r-LLDPE) obtained from discarded bale wrap (an agricultural waste plastic), were upcycled to value-added composite materials. A 50:50 blend of r-PP (a stiff polymer) and r-LLDPE (a tough polymer) was chosen to have a suitable matrix of balanced stiffness-toughness balance suited for composite uses. Maleated compatibilizers were used to improve filler-matrix adhesion. More significantly, the use of compatibilizer improved impact strength by 24 %, tensile and flexural strength by 8 and 13 %, flexural and tensile modulus by 13 %, the heat deflection temperature (HDT) by 19 %, and reduced coefficient of linear expansion in flow direction by 10 % compared to uncompatibilized composites. A 24 % biocarbon filled recycled plastics resulted in a light-weight composite (density being less than 1 g/cm 3 ) with balanced mechanical properties for internal parts usage in automotive.