Effect of in-situ formed core–shell inclusions on the mechanical properties and impact fracture of polypropylene

Effect of in-situ formed core–shell inclusions on the mechanical properties and impact fracture of polypropylene

WoS Article

To obviate the reduction of stiffness in rubber toughened and yield strength in rigid particle toughened iPP, various strategies were adopted. Here, we report on the static and impact properties of isotactic polypropylene (iPP) with in situ formed (rigid thermotropic liquid crystalline core)-(soft copolymer shell) inclusions (RCSS inclusions). We found that, at constant soft shell thickness (t(s)) and stiffness (E-s), the elastic modulus of iPP/RCSS (E-c) increased with the total RCSS volume fraction (nu(RCSS)), and, at constant nu(RCSS), the E-c increased with E-s. At constant ts and Es, the yield strength of iPP/RCSS (sigma(yc)) decreased with the nu(RCSS) and, at constant nu(RCSS) and t(s), the sigma(yc) decreased with E-s in an agreement with the simple micromechanics models of Matonis and Small. At small nu(RCSS), the changes in E-c and sigma(yc) with nu(RCSS) contributed simultaneously to the significant enlargement of the crack tip plastic zone size, enhancing the impact fracture toughness in terms of the apparent critical strain energy release rate (G(c)'), substantially, without significantly reducing stiffness and yield strength. The SEM fractography revealed extension of the RCSS inclusions into fibrous shape providing an additional means for dissipation of mechanical energy stored in the fracturing solid. Experimental data agreed reasonably well with the prediction based on a simple mixed mode fracture model proposed earlier.

To obviate the reduction of stiffness in rubber toughened and yield strength in rigid particle toughened iPP, various strategies were adopted. Here, we report on the static and impact properties of isotactic polypropylene (iPP) with in situ formed (rigid thermotropic liquid crystalline core)-(soft copolymer shell) inclusions (RCSS inclusions). We found that, at constant soft shell thickness (t(s)) and stiffness (E-s), the elastic modulus of iPP/RCSS (E-c) increased with the total RCSS volume fraction (nu(RCSS)), and, at constant nu(RCSS), the E-c increased with E-s. At constant ts and Es, the yield strength of iPP/RCSS (sigma(yc)) decreased with the nu(RCSS) and, at constant nu(RCSS) and t(s), the sigma(yc) decreased with E-s in an agreement with the simple micromechanics models of Matonis and Small. At small nu(RCSS), the changes in E-c and sigma(yc) with nu(RCSS) contributed simultaneously to the significant enlargement of the crack tip plastic zone size, enhancing the impact fracture toughness in terms of the apparent critical strain energy release rate (G(c)'), substantially, without significantly reducing stiffness and yield strength. The SEM fractography revealed extension of the RCSS inclusions into fibrous shape providing an additional means for dissipation of mechanical energy stored in the fracturing solid. Experimental data agreed reasonably well with the prediction based on a simple mixed mode fracture model proposed earlier.

Polypropylene, Core–shell, Liquid crystalline polymer, Ionomer, Impact fracture

Polypropylene, Core–shell, Liquid crystalline polymer, Ionomer, Impact fracture

JANČÁŘ, J.; ŽÍDEK, J.

2016

11.08.2015

0014-3057

EUROPEAN POLYMER JOURNAL

71

7023

United Kingdom of Great Britain and Northern Ireland

221

230

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