Influence of cellulose nanocrystal on strength and properties of low density polyethylene and thermoplastic starch composites

Starch is a renewable and readily available material. Adding starch to low density polyethylene (LDPE) is a sustainable way to reduce the dependency on petroleum based polymers. In this study we investigated the strength and barrier performance of low density polyethylene (LDPE)/thermoplastic starch (TPS) nano composites reinforced with cellulose nanocrystals (CNC). In order to assure well dispersion of CNC in nano composites, initially CNC was added to TPS and then reinforced TPS were blended in extruder with LDPE at various loading levels. Mechanical properties, glass transition temperature (Tg) and melting point (Tm), moisture absorption and barrier properties of the nanocomposites were studied. All mechanical properties, including tensile strength, modulus of elasticity (MOE) and hardness were considerably improved by CNC. Tg and Tm of the nanocomposites were higher in comparison to CNC free nanocomposites. Water absorption showed a significant decrease as a result of addition of CNC to LDPE/TPS blends. The values of water vapor permeability coefficient (WVP) and water vapor transmission rate (WVTR) were reduced by adding CNC, meaning that CNC considerably improved barrier properties of LDPE/TPS composites. Adding 1% CNC to LDPE/TPS blends was the optimal level of CNC loading leading to the highest improvement in the strength and barrier performance of LDPE/TPS blends and satisfied very well required standard tensile strength for extruded and molded LDPE.