Morphological and mechanical characterization of foamed polyethylene via biaxial rotational molding

Abstract

Foamed linear medium density polyethylene parts were prepared by rotational molding in biaxial mode, using different amounts of chemical-blowing agent (azodicarbonamide). Morphological and mechanical properties are presented and discussed in terms of foam density, cell density, average cell diameter, and open cell content. Internal air temperature of the mold was measured as a function of time. Significant differences were observed between unfoamed and foamed parts. The use of an exothermic chemical-blowing agent increased the peak internal air temperature and part cooling was slower due to the presence of gas bubbles acting as insulating material. The most important changes were observed for foam density: adding 1 phr of azodicarbonamide the density decreased from 0.931 g/cm3 (0 phr azodicarbonamide) to 0.295 g/cm3. Finally, the mechanical properties were highly influenced by azodicarbonamide content. Tensile and impact properties were correlated with part density using a simple power–law equation.