Use of functionalized metallocene copolymers from ethylene and polar olefins as compatibilizers for low-density-polyethylene/starch and low-density-polyethylene/dextran blends
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Functionalized metallocene copolymers synthesized from ethylene with 5-hexen-1-ol and ethylene with 10-undecen-1-ol were used as compatibilizers in LDPE/starch and LDPE/dextran blends in order to improve the interfacial adhesion between hydrophobic LDPE and hydrophilic natural polymers. An increase in tensile modulus and a slight decrease in tensile strength was observed when poly [ethylene-co-(10-undecen-1-ol)] was added to a 70:30 wt.-% LDPE/dextran blend, whereas the addition of poly[ethylene-co-(5-hexen-1-ol)] as compatibilizer resulted in obtaining a more rigid material with a slightly higher modulus. Scanning electron microscopy of modified dextran blends containing 3 wt.-% of both compatibilizers showed some degree of phase cocontinuity. Enhanced interfacial adhesion and decrease in particle size of starch was observed when 5 wt.-% of poly [ethylene-co(5-hexen-1-ol)] copolymer was used as the compatibilizer in starch blends. The crystallization temperature of LDPE, determined by DSC, was shifted to a slightly higher temperature as a consequence of the addition of the compatibilizers. The existence of phase segregation was also revealed by thermal analysis when 5 wt.-% of the copolymers were used as blend modifiers.