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Plastic deformation of polypropylene in relation to crystalline structure
Author(s) -
Seguela Roland,
Staniek Eric,
Escaig Bertrand,
Fillon Bertrand
Publication year - 1999
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/(sici)1097-4628(19990314)71:11<1873::aid-app18>3.0.co;2-i
Subject(s) - materials science , tacticity , polypropylene , nucleation , plasticity , monoclinic crystal system , strain rate , crystal (programming language) , slip (aerodynamics) , composite material , crystallography , thermodynamics , crystal structure , polymer , chemistry , physics , computer science , programming language , polymerization
The tensile drawing behavior of quenched and annealed films of isotactic polypropylene is investigated as a function of draw temperature and strain rate. A strain‐induced structural change from the smectic to the monoclinic form is observed for the quenched films. A kinetic interpretation is proposed for the phenomenon. Data of thermal activation volume at the yield point indicate two regimes of plastic flow for the quenched sample, between 25 and 60°C, but only one regime for the annealed sample. Homogeneous and heterogeneous crystal slip processes are proposed to account for these regimes in relation to the nucleation and propagation of screw dislocations. The basic mechanism of molecular motion in the polypropylene crystal is suggested to be a wormlike motion of conformational defects along the 3/1 helix chains that allows a 120° rotation and a c /3 translation. The occurrence of the smectic form as a transitory state in the deformation pathway is discussed in terms of plasticity defect generation. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1873–1885, 1999