Properties of radiation crosslinking of natural rubber/clay nanocomposites

The properties of radiation cured natural rubber/clay nanocomposites were studied. The natural rubber used in this work is of grade SMRL (Standard Malaysian Rubber) and the clay used was sodium montmorillonite modified with various types of cationic surfactants in order to make the galleries hydrophobic and thus more compatible with the elastomer. The natural rubber/clay nanocomposites were prepared by melt mixing at 120 deg C in an internal mixer Haake for 10 minutes. The compound was then irradiated with electron beam at optimum dose. X-ray diffraction results indicated intercalation of the natural rubber into silicate interlayers. Upon irradiation at 250 kGy, the tensile strength of the NR/Na-MMT nanocomposites constantly reduced slightly with increasing clay loading. Whereas the tensile strengths of NR/DDA-MMT and NR/ODA-MMT increases to optimum levels, 12.1 MPa and 9.5 MPa respectively at 3 phr clay contents before decreasing and remain constant up to 10 phr clay content. On the other hand, the elongation of NR/DDA-MMT nanocomposites is less affected with increasing clay content up to 3 phr after which the elongation drop drastically. TGA studied showed that NR/DDA-MMT and NR/ODA-MMT nanocomposites have higher decomposition temperatures in comparison with the NR/Na-MMT. (author)