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Experimental study of post‐shear crystallization of polypropylene melts
Author(s) -
Lee O.,
Kamal M. R.
Publication year - 1999
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.11410
Subject(s) - materials science , polypropylene , crystallization , composite material , shear (geology) , thermodynamics , physics
Abstract In order to study the effects of Processing shear stresses on crystallization behavior, a fiber pullout technique was applied in conjunction with polarized light microscopy and a hot stage. The shear apparatus consisted of a single glass fiber sandwiched between two layers of polypropylene films mounted on the hot stage. At the crystallization temperature, shearing was introduced by pulling the fiber at a constant velocity for a fixed period of time. Static crystallization of the polymer then ensued. Computerized data acquisition and image analysis were employed to observe the evolution of crystallinity, morphology, and growth rates of crystallites in various shear and temperature fields. Two distinct morphological zones were produced upon fiber pullout: bulk spherulites and a shear‐induced layer localized within the vicinity of the fiber surface. The two zones displayed similar kinetic behavior despite the difference in appearance. A comparison of growth behavior in the two zones revealed rates independent of the shear rate but strongly dependent on the crystallization temperature. The main influence of the shear appeared to be in producing higher nucleation rates in the shear zone near the fiber.