PP-blends with tailored foamability and mechanical properties

The optimisation of physical foaming of branched Daploy ™ WB130HMS polypropylene foam resin and corresponding blends with a Polypropylene Blockcopolymer are described in this paper. The resulting foam morphologies of blends consisting of linear and branched polypropylene materials produced at various processing temperatures were studied using a single-screw tandem foam extrusion system and their volume expansion behaviours were compared. Three different die geometry's were tested for physical foaming of PP-blends using 5 and 10 wt% of butane. A correlation between extensional rheology and lower limit of foam density for blends was found. Depending on die geometry the use of different concentrations of branched polypropylene resin in the blends was required to achieve foam densities < 50 kg/m 3 . The influence of foam density and blend ratio on mechanical properties of foams will be discussed on a model and representative samples.