Origin of toughness in .beta.-polypropylene: the effect of molecular mobility in the amorphous phase

0440934 - ÚMCH 2016 RIV GB eng J - Journal Article
Policianová, Olivia - Hodan, Jiří - Brus, Jiří - Kotek, Jiří
Origin of toughness in .beta.-polypropylene: the effect of molecular mobility in the amorphous phase.
Polymer. Roč. 60, 9 March (2015), s. 107-114. ISSN 0032-3861. E-ISSN 1873-2291
R&D Projects: GA ČR(CZ) GA13-29009S
Institutional support: RVO:61389013
Keywords : isotactic polypropylene * β-modification * toughness
Subject RIV: JI - Composite Materials
Impact factor: 3.586, year: 2015

This study aims to explore the origin of toughness in β-phase isotactic polypropylene (i-PP). Samples of commercial-grade i-PP, both neat and nucleated with a specific β-nucleating agent (N,N′-dicyclohexylnaphthalene-2,6-dicarboxamide), were subjected to a combination of structure-sensitive methods and fracture mechanical testing. In addition to common structural characterisation methods, solid-state NMR data were collected to obtain information about the dynamics of the polymer segments as well as the structure. In particular, temperate-induced transformation between the free and constrained amorphous phase was monitored by variable-temperature 13C MAS NMR, whereas T1ρ(1H) relaxation was used to estimate correlations times of segmental motions. Lower thermodynamic stability of rigid amorphous fraction was found in the β-crystalline systems. In contrast helical chains in crystalline and constrained amorphous phase were found to be more restrained in the α-crystalline system. Overall, the results indicate larger restrictions in chain mobility in the amorphous phase of the α-polymorphic PP system than in that of the β-crystalline ones.
Permanent Link: http://hdl.handle.net/11104/0246163