NR (air-dried sheet; ADS) was received from Khuan Pun Tae Farmer Co-operation, Phattaluang, Thailand. PP used in this study was Stamylan P 11E10 with a melt flow index (MFI) of 0.3 g/10 min, measured at 230 °C and 2.16 kg, as obtained from DSM Polypropylenes B.V., the Netherlands. The stabilizers, Irganox®1076 and Irgafos® 168 were obtained from Ciba Geigy, Switzerland.