Compounding of poly(dimethyl siloxane) to reduce tack in natural rubber

Tack in natural rubber latex was reduced by compounding poly(dimethyl silox ane) (PDMS) emulsion in concentrated latex. Sheet and dipped film surfaces were examined with Fourier transform infrared spectroscopy using attenuated total reflection (FTIR-ATR) and by contact angle measurements. Autohesive tack and tensile properties were also determined. For both sheet and dipped film, FTIR-ATR showed that the PDMS concentration was higher at the glass surface than at the air surface, The contact angle of ethylene glycol on th e rubber decreased with increasing PDMS content. Autohesive tack for sheet and dipped film also decreased with increasing PDMS amount; however, anneal ing for 1 week at 70 degreesC in air did cause tack to rise in the sheets. The rubber surface could be made nonadhesive by addition of sufficient PDMS . PDMS caused a decrease in tensile strength for the sheet, especially afte r annealing; however, PDMS did not cause a substantial decrease in percenta ge elongation for the sheets, except at relatively high PDMS contents. The tensile strength and percentage elongation for dipped film was not affected by PDMS over the much more limited PDMS concentration range studied. (C) 2 001 John Wiley & Sons, Inc.