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Influence of composition, crystallization conditions and melt phase structure on solid morphology, kinetics of crystallization and thermal behavior of binary polymer/polymer blends
Author(s) -
Martuscelli Ezio
Publication year - 1984
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.760240809
Subject(s) - crystallization , materials science , nucleation , tacticity , chemical engineering , phase (matter) , crystallization of polymers , polymer , polymer blend , melting point depression , polymer chemistry , thermodynamics , composite material , melting point , polymerization , organic chemistry , chemistry , physics , engineering , copolymer
Results of an investigation on the morphology, the crystallization and the thermal behavior of several binary crystallizable blends are reported. The composition, molecular mass and crystallization conditions strongly influence the crystallization and the thermal behavior as well as the overall morphology of crystallizable binary blends. Quantities such as nucleation density ( N ), radial growth rate ( G ) of spherulites, overall rate of crystallization ( K ), and equilibrium melting temperature ( T m ) are strongly dependent upon composition, crystallization conditions, and molecular mass of components. The type of dependence is to be related to the physical state of the melt, which, at the crystallization temperature, is in equilibrium with or coexists with the developing solid phase. In the ease of compatible blends such as poly(ethylene oxide)/poly(methyl methacrylate) the depression observed for G and T m is mainly to be attributed to the diluent effect of the non‐crystallizable component. For such a blend it is found that, after crystallization, the non‐crystallizable component is trapped in intralamellar regions increasing the distance between adjacent lamellae. Depression of G , in the case of incompatible blends such as isotactic polypropylene/rubbers is mainly accounted for by rejection and deformation of rubber drops. The coexistence during crystallization of different processes such as molecular fractionation and segregation, preferential inclusion or dissolution of molecules with lower molecular mass and/or high degree of steric disorder of the crystallizable component in the phase rich in non‐crystallizable component and vice versa may explain some minima observed in the plots of T m ′and T m , vs. composition in the case of blends semicompatible in the melt. It was found that the addition of a second non‐crystallizable component causes drastic variations on some morphological and structural quantities of the semicrystalline matrix (isotactic polypropylene or nylon 6) such as the shape, dimensions, and regularity of spherulites and interspherulite boundary regions and lamella and interlamella thickness. In some cases the formation of new boundary lines connecting occluded particles are also observed. Such phenomena may have great importance on crack propagation and on impact behavior as well as on the tensile mechanical properties of binary blends characterized by a semicrystalline polymer component with a relatively high T g and a rubber‐like component with a lower T g .