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Effects of molecular weight and molecular weight distribution on creep properties of polypropylene homopolymer
Author(s) -
Kurt Gökçe,
Kasgoz Alper
Publication year - 2021
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.50722
Subject(s) - creep , materials science , viscoelasticity , rheology , polymer , dispersity , polypropylene , tacticity , molar mass distribution , composite material , strain (injury) , polymer chemistry , polymerization , medicine
Abstract The molecular weights of the industrial‐grade isotactic polypropylene ( i‐ PP) homopolymers samples were determined by the melt‐state rheological method and effects of molecular weight and molecular weight distribution on solid and melt state creep properties were investigated in detail. The melt‐state creep test results showed that the creep resistance of the samples increased by M w due to the increased chain entanglements, while variations in the polydispersity index (PDI) values did not cause a considerable change in the creep strain values. Moreover, the solid‐state creep test results showed that creep strain values increased by M w and PDI due to the decreasing amount of crystalline structure in the polymer. The results also showed that the amount of crystalline segment was more effective than chain entanglements that were caused by long polymer chains on the creep resistance of the polymers. Modeling the solid‐state viscoelastic structure of the samples by the Burger model revealed that the weight of the viscous strain in the total creep strain increased with M w and PDI, which meant that the differences in the creep strain values of the samples would be more pronounced at extended periods of time.