engleski

MODIFICATION OF MONTMORILLONITE WITH POLYESTER HYDROCHLORIDES

Montmorillonite (MMT) is a layered alumosilicate mineral most often used in preparation of polymer nanocomposites. To ensure a good intercalation of polymer molecules between the MMT platelets, the surface of MMT platelets has to be modified. MMT is mostly modified by the cation exchange with organic ammonium salts, 1 usually quaternary ammonium salts or amine hydrochlorides with one or more long alkyl chains.2, 3 Polyelectrolytes have been used for modification of MMT for several decades. The influence of polymer molar mass and cationicity (τ ) has been extensively studied. It has been observed that the amount of absorbed polymer (Q) increases with increasing molar mass when cationicity is low. However, when the molar mass is fixed and the cationicity is varied then Q decreases with increasing cationicity.4 Polycations that could also be used for MMT modification are polyester hydrochlorides. These are new polymers obtained by reacting alkyldiethanolamine with organic acid chlorides, and can be transformed to polyesters by extraction in water.5 If excess of polyester hydrochloride is bound to MMT, HCl could be extracted, leaving pendant polyester chains which may improve interaction between the resin and modified MMT. This could lead to enhanced intercalation, and improved physical and mechanical properties in comparison to the nanocomposites prepared with MMT modified with simple alkyl ammonium salts. Cation exchange of MMT with polyester hydrochlorides results in increased interlayer distance of MMT layers as measured by X-ray diffraction. The peak, which determines the interlayer distance shifts towards lower angle indicating the increase in layer thickness. The interlayer distance of modified MMT increases with PHCl/MMT ratio up to 1:3 while at higher ratios it remains constant. The effect of the acid chain length on interlayer distance is of only minor importance. By increasing the number of methylene units of acid from one to six the interlayer distance changed for 0.08 nm. The influence of side chain is more significant. Increasing its length from methyl to octyl the interlayer distance increased for 0.4 nm.

montmorillonite; modification

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