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Abstract. Thermoplastic polymer/layered silicate composites were prepared from the same organophilized montmorillonite (OMMT) and four different matrices, polypropylene (PP), the blend of PP and a maleated polymer (MAPP), poly(lactic acid) (PLA) and polyamide (PA) in order to study the effect of their chemical structure and interactions on composite structure and properties. The components were homogenized by extrusion and then specimens were injection molded, which were then characterized by a variety of methods. The results showed that competitive interactions among silicate layers and between the silicate and the polymer determine the extent of exfoliation, and structure. The morphology of the composites is complicated, exfoliation is never complete, besides individual silicate layers, the composite can contain a silicate network, stacks of silicate platelets and larger particles in various amounts. Several local deformation processes can take place around the structural entities as well as in the matrix. Fracture and debonding are the main particle related processes, while cavitation takes place in the polymer, at least in PA and PLA. The macroscopic properties of layered silicate composites are determined by the extent of exfoliation and interfacial adhesion that decreases upon organophilization. Increased reinforcement and improved composite properties can be achieved only by the proper control of all interactions prevailing in the composite.

Application of nucleating agents is the most versatile and industrially applied way to manipulate the crystalline structure of isotactic polypropylene (iPP). Various materials possess a nucleating effect, but from the viewpoint of dispersibility, the partially soluble ones are the most advantageous. Our objective was to synthesize new N , N ′-dicyclohexyldicarboxamide homologues and study their applicability as nucleating agents in iPP. Carbon-13 nuclear magnetic resonance ( 13 C NMR) and infrared spectroscopy were used to prove that the synthesis reactions were successful. Thermal stability of the compounds was investigated with simultaneous thermal analysis. Nucleating efficiency and solubility were characterized by polarized light microscopy and differential scanning calorimetry. Polarized light microscopy was also applied to study the effect of novel additives on the morphology of iPP. The properties, important from the viewpoint of applicability, were also investigated. Tensile tests were performed to characterize the main mechanical properties, and standard haze measurements were performed to characterize optical properties. It can be concluded that the investigated compounds are partially soluble nucleating agents and influence the crystalline structure of iPP. Most of the studied compounds have a moderate nucleating efficiency, but a very interesting dendritic structure develops in their presence. Two of them proved to be non-selective β-nucleating agents, which result in a remarkable improvement of impact resistance and higher opacity.

This work demonstrates and models the self-organization of mixed polymorps in polymers containing simultaneously growing phases with different growth rates. The model was verified and demonstrated in isotactic polypropylene nucleated by a nonselective nucleating agent. The crystallization and melting processes were studied by calorimetry (DSC) and polarized light microscopy (PLM). The morphology of the samples was investigated using PLM and scanning electron microscopy (SEM). The fundamental rules of the formation of two polymorphic modifications developing simultaneously on the same nucleating particle are introduced. A simple equation is suggested to predict the morphological geometry on the lateral surface of the nucleating agent. The results indicated good agreement between the predicted and observed geometry. The proposed model explains the self-organization of micro-sized reinforcements of α-modification in the matrix of β-iPP. Although the proposed equation was tested for this particular case it is a general equation for all structures in which different polymorphs are growing simultaneously with different growth rates.