Structural changes of homopolymer polypropylene foam with molecular weights and rheological properties: (1) In batch process

The effects of molecular weights and rheological properties of polypropylene (PP), on its foam structures in batch process were investigated. The effects of cross[inking process were also considered in this studs. The rheological properties of polypropylene, storage modulus (G'). loss modulus (G"), zero shear viscosity(eta(0)), and relaxation as time(lambda), increased with the increase of molecular weights, and these increases in rheological properties directly affected the stability improvement, of the PP foam. The increase of crosslinked PP's gel content stopped at the irradiation dose of 3.2 Mrad. The development of foam Structures was more enhanced Lis the irradiation dose increased up to 3.2 Mrad. When the irradiation dose exceeded 3.2 Mrad. however. it negatively affected the structural development of the foam by diminishing gel contents of the foaming material, which resulted in instability of the foam structure.