Novel functionalized polyolefins as compatibilizers in polyolefin/polyamide 6 blends and polyethylene/metal hydroxide composites

Abstract

Ricinoloxazoline maleinate (OXA) was grafted by melt free radical grafting onto polyolefins and elastomers to produce new compatibilizers for polymer blends. Effects of initial monomer and peroxide concentrations on the degree of grafting, on the amount of residual monomer, and on the side reactions were investigated. Reactive compatibilizers could be prepared with a suitable choice of processing conditions and initial concentrations. These oxazoline functionalized polyolefins and elastomers were found to act as effective compatibilizers in polymer blends.

Blends of polyolefins and polyamide 6 were compatibilized with two novel types of compatibilizers: oxazoline functionalized polymers prepared by grafting and functionalized polyolefins prepared by copolymerization using metallocene catalysts. Comparison was made with commercial compatibilizers. Effects of the compatibilizers on blend morphology and thermal, tensile, and impact properties were studied. All of the functionalized polyolefins were effective compatibilizers in polyethylene/polyamide 6 blends. They were able to reduce the particle size and attach the particles more firmly to the matrix. The toughness was improved, though usually at the cost of stiffness. Only functionalized polyethylenes prepared with metallocene catalysts were able to improve the stiffness and strength along with toughness.

In commercial polyolefin composites, fillers are usually coated with a fatty acid to make them organophilic. Replacement of fatty acid coatings with polymeric compatibilizers was studied in polyethylene/aluminum hydroxide (PE/ATH) and polyethylene/magnesium hydroxide (PE/MH) composites. The polymeric compatibilizers were oxazoline grafted polyethylene prepared by melt free radical grafting, hydroxyl and carboxylic acid functionalized polyethylenes prepared with metallocene catalysts, and commercial functionalized polyethylenes. Adhesion fracture changed to cohesion failure when the fatty acid coating was replaced through the addition of polymeric compatibilizers. Improvement in both stiffness and toughness was achieved, and improvements in flammability properties achieved with ATH or MH were preserved when polymeric compatibilizers were used as adhesion promoters.