The role of nucleating agents in high-pressure-induced gamma crystallization in isotactic polypropylene.
Nucleation of the γ-form in isotactic polypropylene (PP) under high pressure was investigated. Three nucleating agents were used to nucleate crystallization of PP under atmospheric pressure: commercial Hyperform HPN-20E from Milliken Chemical, poly(tetrafluoroethylene) particles nucleating the α-form, and calcium pimelate nucleating the β-form. Crystallization of neat PP and PP with addition of 0.2 wt% of the nucleating agents was studied. Specimens were either kept at 200 °C under pressure of 200 MPa for time ranging from 2 min to 4 h or for 15 min under pressure ranging from 1.3 to 300 MPa. After cooling to ambient temperature and releasing the pressure, the specimens were analyzed by DSC, WAXD, and PLM to have an insight into the structure and to determine a crystallinity level and contents of crystallographic forms. Both α-nucleating agents strongly nucleated crystallization of PP under high pressure in the γ-form, whereas the β-nucleating agent had only a slight effect. The results show the possibility to use nucleating agents to nucleate the γ-form of PP under high pressure.
Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Sienkiewicza 112, 90 363 Lodz, Poland.
Przemyslaw
P
Sowinski
Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Sienkiewicza 112, 90 363 Lodz, Poland.
Ewa
E
Piorkowska
Department of Physics and Mechanics of Materials, P PRIME Institute-ISAE-ENSMA, UPR CNRS 3346, 1 Avenue Clément Ader, 86961 Futuroscope Chasseneuil, France.
Severine A E
SA
Boyer
Centre for Material Forming, MINES ParisTech, PSL-Research University, UMR CNRS 7635, 1 Rue Claude Daunesse, 06904 Sophia Antipolis, France.
Jean-Marc
JM
Haudin
Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Sienkiewicza 112, 90 363 Lodz, Poland.
Kinga
K
Zapala
Crystallization; Gamma nucleation; High pressure; Isotactic polypropylene; Nucleating agents