Lamellae properties, polymer crystal nucleation

Crystallization is an inherently time-dependent process the nucleation and growth of crystalline structures, the degree of crystallinity, the phase structure and quality of crystal lamellae, and their connectedness strongly influence the mechanical properties of semi-crystalline polymers. It is for this... 

Another side benefit that accompanies with the use of certain nucleants is improved clarity. Since clarity or transparency is evidently related to the crystalline structure of the polymer and the structure is determined by the conditions of crystallization, parameters characterizing crystallization must be also connected with the optical properties of a PP product. The peak temperature of crystallization (Tc) is one of the quantities often used for the characterization of the crystallization process and efficiency of nucleating agents. With increased crystallization temperature, the thickness of the lamellae increases well. Higher efficiency and concentration of nucleating agent lead to an increase of Tc (as determined by DSC) and decrease of the size of the spherulites. 

The crystalline structure of the polymer changes considerably in the presence of the silicate and all changes depend on the bentonite content. However, the relative amount of y modification and the crystallinity change the same way in the presence of the two organophilic silicates used in this study the nontreated filler behaves somewhat differently. The only dissimilar effect appears in the nucleation of the composites a lower crystallization temperature results in thinner lamellae and a softer matrix. This could explain the smaller modulus of the composite containing the filler coated with the aliphatic amine, but this small effect does not justify the drastic differences in other mechanical properties. Changing the crystalline structure does not seem to be the factor determining the properties of the nanocomposites studied. 

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