Improved Barrier and Mechanical Properties of Laminar Polymer Blends

Abstract

Transformation of the spherical particles of dispersed phase in polymer blends into laminar morphology may have significant effect on the diffusion of gases and hydrocarbons through films and container walls. Tailoring the morphology of immiscible polymer blends to achieve specific properties, needs knowledge of the parameters that affect morphology development. Among them, flow field, viscosity ratio, interfacial tension, and elasticity ratio are the most important material characteristics that affect the morphology. This chapter presents how these parameters might be manipulated to develop laminar blends with barrier properties comparable to co-extruded materials. Optimizing the maleation level of high density polyethylene provides good mechanical performance for these blends. The effect of precompounding in a twin-screw extruder on the mechanical and barrier properties of the blends is also reported and discussed. The above observations regarding the barrier and mechanical properties are supported by morphological studies. By optimizing both the maleation level of polyethylene and twin-screw compounding of the HDPE/PA-6 blends combined with a special die design, it is possible to generate laminar structure in extruded ribbons of HDPE/PA-6 blends. Such blends have barrier properties in the range of co-extruded materials. These extraordinary barrier properties are accompanied by good mechanical properties.