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| Titel: |
NON-ISOTHERMAL CRYSTALLIZATION AND MELTING BEHAVIOR OF POLY(PROPYLENE)-POLY(ETHYLENE VINYL ACETATE) [PP/EVA] AND POLY(PROPYLENE)-(ETHYLENE-PROPYLENE) [PP-EP/EVA] BLENDS |
| Auteur: |
Ramirez-vergas, E. Navarro-Rodriguez, D. Huerta-Martinez, B. M. Avila-Orta, C. A. Palacios-Mezta, M. Medellin-Rodriguez, F. J. |
| Verschenen in: |
International journal of polymeric materials |
| Paginering: | Jaargang 51 (2002) nr. 6 pagina's 485-496 |
| Jaar: |
2002-01 |
| Inhoud: |
The melting behavior of PP/EVA and PP-EP/EVA blends non-isothermally crystallized was studied. The morphology of blends was evaluated in terms of crystal habits, spherulitic structure and melting characteristics. For PP and EVA homopolymers the observed crystal habits were f-monoclinic and orthorhombic corresponding to PP and PE cyrstals since this last is a part of the EVA copolymer. Two types of f-crystals were associated to the experimental data and they were designated as low (LPf-C) and high (HPf-C) perfection f-crystals. These crystals were relatively unaffected in nature after blending the PP or the PP-EP with the EVA copolymer. Nevertheless, crystallinity decreased and the spherulitic structure changed. In differential scanning calorimetry [DSC] heating traces two partially overlapped endothermic signals were observed during heating of the non-isothermally crystallized specimen. The low temperature endotherm (I) was associated to melting of LPf-C structures while the high temperature endotherm (II) was related to two different melting processes, one corresponding to HPf-C structures and the other to recrystallized or reorganized material. The shifting of endotherm I to lower temperatures was considered an effect of interfacial interactions in the crystalline zones between the LPf-C of PP and the orthorhombic crystals of EVA. Modulated differential scanning calorimetry [MDSC] traces corroborated that recrystallization is higher in PP/EVA blends the opposite being the case in PP-EP/EVA blends. Differences in the multiple melting between PP/EVA and PP-EP/EVA blends are discussed in terms of molecular interactions. |
| Uitgever: |
Taylor & Francis |
| Bronbestand: |
Elektronische Wetenschappelijke Tijdschriften |
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