Sustainable biocarbon from pyrolyzed perennial grasses and their effects on impact modified polypropylene biocomposites

Using biocarbon as a biobased filler in polymers is gaining increased attention because of its carbon neutrality and low cost. However, systematic studies investigating the effect of pyrolysis temperature on the surface characteristics and properties of biocarbon and how these biocarbon affect the composite properties are lacking. In this study, biocarbons from pyrolyzed miscanthus grass at two different conditions were characterized for their physical and chemical properties for biocomposites uses. To evaluate the effect of these biocarbons in polyolefin based biocomposites, two loading levels of 10 and 20 wt % of each biocarbon sieved to a particle size range of 20-75 μm were melt blended with a toughened polypropylene/poly (octene-ethylene) copolymer (POE) (70/30 wt %) blend. The results validated that higher pyrolysis temperature eliminated the surface functional groups and increased the specific surface area which promoted better compatibility between the biocarbon and polyolefin matrix. Also, the high temperature pyrolyzed biocarbon (HTBioC) produced significantly better stiffness-toughness balance in the composite compared to low temperature pyrolyzed biocarbon (LTBioC). Morphology of the composites and biocarbon were analyzed by scanning electron microscopy (SEM), nano-mechanical mapping through atomic force microscopy (AFM), surface area and pore size distribution measurements. The results confirmed encapsulation of both types of biocarbons by the POE phase. Filler-polymer interactions were compared using dynamic strain and frequency sweep rheometry and results were suggesting that HTBioC had stronger interactions with the matrix. While HTBioC caused nucleating effect on the matrix no changes were observed in crystallization behavior of LTBioC based composites.