Compression Moulding of Polypropylene Foams and Their Properties

Compression moulding was used to produce polypropylene foams using azodicarbonamide as a chemical blowing agent. The morphology of the foams is reported in terms of cell size, cell density, and skin thickness using 1.5, 2, 2.5 and 3% of blowing agent. The resulting foams were characterized mechanically in terms of tensile and flexural moduli and comparison with mechanical models was made to predict foam performance. In general, mechanical properties, cell density, skin thickness and foam density decreased, while cell size increased with increasing amount of blowing agent. It was also found that simple mechanical models based solely on foam density and skin thickness were not able to correctly predict all the experimental data. For better prediction, foam density profile must be used.