Crystallization and melting behavior of polypropylene and maleated polypropylene blends

Citation
Kw. Cho et al., Crystallization and melting behavior of polypropylene and maleated polypropylene blends, POLYMER, 40(7), 1999, pp. 1719-1729
Citations number
26
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Organic Chemistry/Polymer Science
Journal title
POLYMER
ISSN journal
0032-3861 → ACNP
Volume
40
Issue
7
Year of publication
1999
Pages
1719 - 1729
Database
ISI
SICI code
0032-3861(199903)40:7<1719:CAMBOP>2.0.ZU;2-I
Abstract
The melting behavior of blends of polypropylene (PP) and maleic anhydride g rafted PP (mPP), crystallized both non-isothermally and isothermally, have been investigated by differential scanning calorimetry (DSC). Also the rela tionship between co-crystallization, phase separation and the corresponding crystallization conditions in the blends is presented. It has been found t hat either co-crystallization or phase separation in the blends can be obta ined, depending on the crystallization conditions. If the cooling rate is v ery slow in the non-isothermal case, or the crystallization temperature is relatively high in the isothermal case, phase separation between PP and mPP molecules will be observed in the blends. Otherwise, co-crystallization be tween different molecules will dominate in the blend system. An effort was made to elucidate these phase phenomena with the aid of kinetic parameters by isothermal crystallization. Fractional values of the Avrami exponent are obtained, which range from 1.93 to 3.21, indicating an average contributio n of simultaneous occurrence of various types of nucleation and growth of c rystallization. The half-life t(1/2) Of crystallization shows that incorpor ation of mPP in PP can either have little effect or greatly increase the cr ystallization rate of PP, depending on the crystallization temperatures. At higher crystallization temperatures, the crystallization rate of the blend s is higher than both the pure homopolymers, resulting in phase separation morphology. The results by small angle X-ray scattering (SAXS) are consiste nt with those of the DSC measurements. It has been concluded that the cryst allization kinetics, not the thermodynamics, mainly determine the final pha se morphologies in this particular system. (C) 1999 Elsevier Science Ltd. A ll rights reserved.