[en] Chlorinated polyethylene (CPE) nanocomposites were synthesized by melt blending clay-rich/poly(e-caprolactone) (PCL) masterbatches to CPE matrices. The masterbatches were prepared following two synthetic routes: either PCL is melt-blended to the clay or it is grafted to the clay platelets by in situ polymerization. The microscopic morphology of the nanocomposites was characterized by X-ray diffraction, atomic force microscopy, transmission electron microscopy, and modulated temperature differential scanning calorimetry. When using free PCL, intercalated composites are formed, with clay aggregates that can have micrometric dimensions and a morphology similar to that of the talc particles used as fillers in commercial CPE. PCL crystallizes as long lamellae dispersed in the polymer matrix. When using grafted PCL, the nanocomposite is intercalated/exfoliated, and the clay stacks are small and homogeneously dispersed. PCL crystallizes as lamellae and smaller crystals, which are localized along the clay layers. Thanks to the grafting of PCL to the clay platelets, these crystalline domains are thought to form a network with the clay sheets, which is responsible for the large improvement of the mechanical properties of these materials.
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The chemical masterbatches were synthesized with organo-modified MMTs derived from natural sodium MMTs that have a cation exchange capacity (CEC) of 92 mequiv/100 g, i.e., with a clay area per cation of 142 Å2. The polymerization conditions were set to obtain masterbatches with 25 wt % inorganics. From these data, the organic layer that covers the clay surfaces is estimated to be about 3 nm thick for a dense organization of the chains (the density of the PCL layer has been considered to be close to the density of bulk PCL).
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To calculate Mn (PCL) for the chemical masterbatches, the alkylammonium cation to which PCL is grafted has been taken into account. It is located at the end of the PCL chain for MMT-HDMOH75 and in the middle of the PCL chain for PCL-MMT-TAOH200.
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