Properties of epoxy and unsaturated polyester nanocomposites with polycation modified montmorillonites

• Mt was modified by polycations.
• Nanocomposites Mt/epoxy and Mt/unsaturated polyester have been prepared.
• Plasticizing effect of longer alkyl side-chains is observed.
• Better mechanical properties being compared to commercial modified Mt nanocomposites.
• Unchanged thermal stability of UP while increased decomposition of epoxy resin.

Polyesters (P) based on N-alkyldiethanolamines (alkyl being octyl, ODEA; dodecyl, DDEA; or hexadecyl, HDEA) and succinic acid anhydride were synthesized and transferred to polyester hydrochlorides (P-HCl) by the addition of HCl. They were used for modification of mineral montmorillonite (Mt). It was assumed that one part of the P-HCl molecule exchanged sodium cations from the interlayer spaces, while the other part was subsequently unprotonated with water. This part of the macromolecule should be better miscible with polymers of similar polarity, such as unsaturated polyesters (UP) and epoxides (E), than quaternary ammonium salts. Molar ratio Mt:P:HCl was 1:3:3 or 1:3:1.5 in accordance with Mt cation exchange capacity. The d-values of Mt, modified with polyesters P-ODEA, P-DDEA and P-HDEA, were 1.80 nm, 3.65 nm, and 4.12 nm, respectively, and they were independent of HCl ratio.Unsaturated polyester and epoxy resin nanocomposites with 1%, 3%, and 5% of modified Mt were prepared and characterized by dynamic mechanical analysis (DMA), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). The storage modulus increases with the increasing Mt content, and it decreases with the length of alkyl side chain in modifying polyester, indicating a plasticizing effect of the long alkyl chain, which is supported also by the decrease of glass transition temperatures. The thermal stability of the clay polymer nanocomposites (CPN) is the same as that of the neat resin for unsaturated polyester and deteriorates for epoxy nanocomposites.