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Internal stress, lattice deformation, and modulus of polymers

Authors

  • Anqiu Zhang,

    Corresponding author
    1. Man-made Fiber Research Institute, China Textile University, Shanghai, People's Republic of China
    • Department of Polymer Science, University of Akron, Akron, OH 44325-3909
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  • Hao Jiang,

    1. Man-made Fiber Research Institute, China Textile University, Shanghai, People's Republic of China
    Current affiliation:
    1. Department of Materials Science and Engineering, Georgia Institute of Technology, School of Textile & Fiber Engineering, Atlanta, GA 30332-0295
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  • Zongquan Wu,

    1. Man-made Fiber Research Institute, China Textile University, Shanghai, People's Republic of China
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  • Chenxun Wu,

    1. Man-made Fiber Research Institute, China Textile University, Shanghai, People's Republic of China
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  • Baojun Qian

    1. Man-made Fiber Research Institute, China Textile University, Shanghai, People's Republic of China
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Abstract

The relationships among internal stress, lattice deformation, and the moduli of polymers, such as poly(ethylene terephthalate) (PET), polypropylene (PP), polyethylene (PE), polyacryonitrile (PAN), and poly(p-phenylene terephthalamide) (PPTA), have been studied systematically. Compared to small molecule crystals, polymer crystals have many more defects and their parameters of the crystal unit cells and the density of the crystalline region are easy to vary to a certain extent. During the processing, external stresses were put on the polymer fibers and polymer molecules were drastically deformed, which induced polymer crystallization and preferred orientation. After processing, there are many macromolecules frozen in the nonequilibrium status, which is the cause of internal stress. Heat treatment could give energy to the macromolecules to release the internal stress and to approach thermodynamic equilibrium. For polymer crystals, the higher the annealing temperature, the shorter the lengths of the unit cell axes, the more integral and regular the crystal lattice, and the smaller the unit cell volume. Crystalline modulus changes not only with different kinds of polymer materials, but also with measurement temperature and processing history. Polymer processing, mainly drawing, causes orientation and internal stress which causes lattice deformation and raises tensile modulus of polymer materials.

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