Recycled polypropylene-polyethylene torrefied almond shell biocomposites

The present study revealed that torrefied almond shells (TAS) can be used as a bio-reinforcing agent for recycled polypropylene-polyethylene (PP-PE) blends without requiring a compatibilizer. Torrefaction of almond shells was performed to increase their hydrophobicity and provide good interfacial adhesion between matrix and filler. PP-PE samples blended with TAS were prepared using 3 different size ranges (sieved between mesh sizes of 100 and 120, 60 and 70, 35 and 45) and 7 different weight percent (%wt) loadings (0, 5, 10, 20, 30, 40, and 50). An increase in TAS loading resulted in an increase in flexural and tensile moduli, but a decrease in strength, elongation, and toughness. The effect of particle size and %wt loading on the heat deflection temperature (HDT) and crystallinity of PP-PE biocomposites were analyzed by thermo-mechanical analysis (TMA) and differential scanning calorimetry (DSC), respectively. HDT increased with higher TAS loading and with smaller particle size. The maximum observed increase was 10 °C at 30%wt loading of the small particles compared to neat PP-PE. The results for these biocomposites show that they can be potential candidates for consumer plastic applications.