Experimental investigation into the direct feeding of coupling agent, cellulose nanocrystals, and nano zinc oxide in high-density polyethylene

Abstract

High density polyethylene (HDPE) is widely used in composite industry as a host polymer because of its low cost and competitive mechanical properties. However, the addition of hydrophilic reinforcing nanofillers in HDPE-based composites is challenging and often requires chemical treatment. This study explored the addition of coupling agent maleic anhydride (MA) for improving the dispersion of cellulose nanocrystals (CNCs) and nano zinc oxide (ZnO) in HDPE matrix, using two separate methods. MA grafted HDPE (MAPE) and HDPE with MA powder (HDPE-MA) were melt compounded with CNCs and ZnO. These nanofillers has been of recent interest due to their superior properties, wide availability, and biocompatibility. Physical and mechanical properties of the composite samples were studied using different characterization techniques (FTIR, SEM, DMA, Tensile and Rheology). Overall, composites with HDPE-MA showed improved adhesion between fillers and matrix, compared to the MAPE composites. Furthermore, using CNCs and ZnO in powder form and separately, displayed better interactions between nanoparticles and HDPE matrix, indicating improved energy dissipating properties. HDPE-MA composites showed relatively similar values for mechanical properties compared to the virgin HDPE, however, adding nanofillers into MAPE increased the maximum tensile strength up to 42% but lowered the Young's modulus. The addition of nanofillers increased the complex viscosity for HDPE-MA nanocomposite whereas decreased this measure for MAPE nanocomposites, compared to their respective virgin polymers. Similarly, loss and storage moduli improved for HDPE-MA nanocomposites and declined for MAPE nanocomposites compared to their respective virgin polymers.