The effect of molecular weight on tensile property and fracture toughness of the polyimide resin

Mitsuo Notomi, Hisashi Inaba, Kikuo Kishimoto, Toshikazu Shibuya, Atsushi Morita, Yasunori Yoshida

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The effects of molecular weight on mechanical properties of the thermoplastic polyimide are investigated. The specimens which have 4 different molecular weights (Mw) ranging from 2.5×104 g/mol to 3.8×104g/mol are prepared. Young's modulus, tensile strength and Poisson's ratio are determined by the tensile tests. To obtain the fracture toughness, Jic the multiple specimen method is applied since the crack propagation occurs in a stable manner. Although Young's modulus, tensile strength and Poisson's ratio are almost constant over the range of Mw tested, the Jic increases with the increase of molecular weight. The rib-like pattern and the river-like pattern are observed on the fracture surfaces of lower and higher Mw specimen, respectively. These observations indicate that the crazes significantly grow for the specimens with higher Mw. This is considered to be the reason for the increase of fracture toughness. The relationship between the fracture toughness and molecular weight is obtained based on Kusy and Turner.

Original languageEnglish
Pages (from-to)67-71
Number of pages5
JournalNihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A
Issue number629
Publication statusPublished - 1 Jan 1999


  • Fracture toughness
  • Material testing
  • Molecular weight
  • Polyimide
  • Polymer materials
  • Sem observation
  • Tensile properties

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