Premium
Polypropylene during crystallization from the melt as a model for the rheology of molten‐filled polymers
Author(s) -
Boutahar Khaled,
Carrot Christian,
Guillet Jacques
Publication year - 1996
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(19960404)60:1<103::aid-app12>3.0.co;2-9
Subject(s) - materials science , rheology , volume fraction , polypropylene , differential scanning calorimetry , polymer , crystallization , composite material , dispersion (optics) , relaxation (psychology) , chemical engineering , thermodynamics , social psychology , psychology , physics , optics , engineering
Polarized light microscopy shows that polypropylene crystallizes from the melt into a well‐distinguished spherulitic structure. Therefore, it provides a useful model for molten‐filled polymers, where the growing spherulites are considered to be filler particles dispersed in a matrix fluid. Although spherulites are randomly dispersed in the space, two dispersion models (simple cubic and centered cubic) are discussed to correlate the transformed fraction α( t ) with the volume fraction of filler ϕ(t). The combination of these results with those of differential scanning calorimetry (DSC) shows that the transformed fraction α( t ) is a direct indication of the volume fraction of filler ϕ( t ). The rheological study, using oscillatory experiments coupled with DSC results, shows the relative sensitivity of the rheological functions to structural changes of the liquid during crystallization. Furthermore, they reveal the existence of a yield effect above a certain criticl value of the filler content (ϕ c = 0.4). In the absence of this yield effect, a model is proposed to predict the variation of the rheological functions with the filler content. This model shows not only a variation of the plateau modulus, but also the modification of the characteristic times of relaxation of the polymer matrix, whereas the shape of the relaxation spectrum remains unchanged. © 1996 John Wiley & Sons, Inc.