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Strain‐induced crystallization kinetics of vinylidene chloride/vinyl chloride (VDC/VC) copolymers. Part III. Comparison of the effect of biaxial and uniaxial strain
Author(s) -
Lund Monty,
Steinbrunner Jim
Publication year - 1988
Publication title -
journal of vinyl technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.295
H-Index - 35
eISSN - 1548-0585
pISSN - 0193-7197
DOI - 10.1002/vnl.730100204
Subject(s) - materials science , copolymer , crystallization , amorphous solid , composite material , vinyl chloride , kinetics , stress (linguistics) , strain rate , activation energy , strain (injury) , polymer chemistry , crystallography , thermodynamics , polymer , chemistry , medicine , linguistics , physics , philosophy , quantum mechanics
Specimens of amorphous VDC/VC tube taken immediately after the water quench bath on the blown film process were stretched uniaxially and biaxially using a T. M. Long film stretcher. The stress and temperature responses were monitored. The crystalline content as a function of time was calculated based on an energy balance and the observed temperature response. It was found that SIC kinetics shows a similar dependence on extension ratio (ER) for the uniaxial and biaxial cases. The crystallization rate increases rapidly when an extension ratio of 3.5 is first reached in either the machine direction (MD) or transverse direction (TD). However, significantly greater engineering and true stress values are reached for biaxial stretching than for uniaxial stretching. This is due to the greater molecular alignment in the plane of the specimen versus the thickness direction and to the lesser specimen thickness for the biaxial case. The copolymer studied was an 88/12 wt/wt VDC/VC copolymer with a weight average molecular weight of 100,000 containing liquid additives that function as processing aids.