Formation of nanoscale pores in shish-kebab structured isotactic polypropylene by supercritical CO2 foaming.

In this article, a new technique combining polymer dynamic processing and low temperature foaming was proposed to fabricate isotactic polypropylene (iPP) foams with nano-scale cellular structures. A self-developed loop oscillating push–pull molding (LOPPM) device was first used to fabricate the highly oriented iPP samples with shish-kebab crystalline structure. A temperature-quench batch foaming device was used to foam the shish-kebab structured iPP sample at 100 °C with supercritical carbon dioxide (sc-CO 2 ) as blowing agent. Nano pores with average size of 55.3 nm were generated during foaming, attributing to the hindrance and nucleation synergistic effects of the shish-kebab crystalline structure. The LOPPM-PP foam samples showed high ultimate tensile strength (100% higher than PP) and strain-at-break (186% higher than LOPPM-PP), and excellent impact strength (658% higher than PP). [ABSTRACT FROM AUTHOR]