Polymer phase transcrystallinity

In semi-crystalline polymers the interaction of the matrix and the tiller changes both the structure and the crystallinity of the interphase. The changes induced by the interaction in bulk properties are reflected by increased nucleation or by the formation of a transcrystalline layer on the surface of anisotropic particles [48]. The structure of the interphase, however, differs drastically from that of the matrix polymer [49,50]. Because of the preferred adsorption of large molecules, the dimensions of crystalline units can change, and usually decrease. Preferential adsorption of large molecules has also been proved by GPC measurements after separation of adsorbed and non-attached molecules of the matrix [49,50]. Decreased mobility of the chains affects also the kinetics of crystallization. Kinetic hindrance leads to the development of small, imperfect crystallites, forming a crystalline phase of low heat of fusion [51]. 

Transcrystalline morphology is formed when crystallization takes place on the solid surface of fillers or reinforcements. Transcrystallizafion takes place when the density of the crystal nuclei is substantially greater on the surface of solid inclusions than in the melt bulk (77). Because polyhedral sphemlites cannot develop due to restricted lateral growth on the solid surface, crystallites are allowed to grow only in stacks perpendicularly to the surface plane (78). In the case when only one crystal form occurs in a polymer, Keller (79) confirmed that the microstructure of transcrystalline layer and bulk crystalline phase is identical. For PP, however, the situation is more complicated by the polymorphism so that one crystal form can exist in the transcrystalline layer and another in the polymer bulk. The nature of nucleation of the transcrystalline layer is still somewhat con-... 

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