Polydimethylsiloxane assisted supercritical CO₂ foaming behavior of high melt strength polypropylene grafted with styrene

Abstract

Foamable high melt strength polypropylene (HMSPP) was prepared by grafting styrene (St) onto polypropylene (PP) and simultaneously introducing polydimethylsiloxane (PDMS) through a one-step melt extrusion process. The effect of PDMS viscosity on the foaming behavior of HMSPP was systematically investigated using supercritical CO₂ as the foaming agent. The results show that the addition of PDMS has little effect on the grafting reaction of St and HMSPP exhibits enhanced elastic response and obvious strain hardening effect. Though the CO₂ solubility of HMSPP with PDMS (PDMS-HMSPP) is lower than that of HMSPP without PDMS, especially for PDMS with low viscosity, the PDMS-HMSPP foams exhibit narrow cell size distribution and high cell density. The fracture morphology of PDMS-HMSPP shows that PDMS with low viscosity disperses more easily and uniformly in HMSPP matrix, leading to form small domains during the extrusion process. These small domains act as bubble nucleation sites and thus may be responsible for the improved foaming performance of HMSPP.

Graphical abstract

Keywords

high melt strength polypropylene (HMSPP) / polydimethylsiloxane (PDMS) / supercritical CO₂ / foaming behavior

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Acknowledgements

This work was financially supported by National Natural Science Foundation of China (Grant Nos. 21476085 and 21306047), Fundamental Research Funds for the Central Universities of China (22A201514016; 222201314051).

Funding

RIGHTS & PERMISSIONS

2016 Higher Education Press and Springer-Verlag Berlin Heidelberg