Manufacturing and Characterization of High-Density Polyethylene Composites with Active Fillers from Persimmon Peel Flour with Improved Antioxidant Activity and Hydrophobicity

The potential of persimmon peel waste (PPF) as renewable active filler in biobased polyethylene composites, with improved antioxidant properties and resistance to water uptake is shown. To improve the interaction between the hydrophilic biofiller and the highly hydrophobic matrix, several compatibilization approaches are assessed. The first approach consists of using a polyethylene grafted copolymer with maleic anhydride (PE-g-MA). The second approach consists of modifying the PPF surface with two treatments before compounding with Bio-HDPE. The first consists on conventional silanization with (3-glycidyloxypropyl)trimethoxysilane, while the second consists on esterification with palmitoyl chloride. The results show an improvement of the matrix/biofiller interaction, as observed by field emission scanning electron microscopy (FESEM), leading to an increase in Young's modulus of 10% in composites compatibilized with PE-g-MA, and silanized PPF compared to composites without compatibilizer and no surface treatment on PPF. Interestingly, treatment with palmitoyl chloride leads to an increase in the hydrophobic behavior of composites keeping the water contact angle virtually constant at 128 degrees. This effect is also reflected in a clear decrease in water absorption capacity of only 0.3 wt% over 9 weeks. Finally, PPF increases stabilization against oxidation, improving the oxidation induction time from 4.8 min (Bio-HDPE) to 82.5 min for composites with silanized PPF.