Polymer blends, microcomposites

The physical mixing of two or more polymers to crate a material with properties different from each of the components has become an increasingly popular route to new materials development. The resulting blend or alloy greatly reduces the associated time and costs while permitting improved processibility and enhanced properties tailored to specific application areas. Many commercial examples of two-phase polyblends consist of a matrix polymer impact modified by the addition of rubber particles. Recently, however, TLCPs have received increasing attention in the scientific and technical literature as in situ reinforcements in polymer blends and microcomposites. The matrices examined in the literature include polyimides, PES, PEI, PEEK, polycarbonate, PET, PPS, and polyarylate. 

Pluta, M., Galeski, A., Alexandre, M., Paul, M.A., Dubois, P. Polylactide/montmorillonite nanocomposites and microcomposites piepaied by melt blending Structure and some physical properties. J. Appl. Polym. Sci. 86, 1497—1506 (2002)... 

The preparation of nanocomposites by melt intercalation is a very attractive environmentally friendly process since no solvent is required. In this method, the polymer matrix is blended in the molten state with a known amount of layered silicate. Under these conditions, if the layered surfaces are sufficiently compatible with the chosen matrix, the polymer can crawl into the interlayer space and forms an intercalated nanocomposite. In the case of poor compatibility between the silicate host and the polymer matrix, polymer intercalation is not allowed and micro-size clay particles are randomly dispersed in the matrix, forming a microcomposite. 

The preparation of PCL nanocomposites by melt blending leads to microcomposites when Cloisite Na is used whereas intercalated structures are obtained with organo-modified clays such as Cloisite 25A and Cloisite 30B. As expected, the mechanical and barrier properties of the conventional microcomposites are in the same range of unfilled PCL. In contrast, all main properties of the material are improved by intercalating polymer chains between silicate sheets. 

Pluta M, Caleski A, Alexandre M, Paul M-A, Dubois P (2002), Polylactide/ montmorillonite nanocomposites and microcomposites prepared by melt blending structure and some physical properties , J Appl Polym Sci, 92, 1497-506. 

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