1. Department of Rubber Technology and Polymer Science, Faculty of Science and Technology; Prince of Songkla University; Pattani 94000 Thailand
2. Faculty of Science and Technology; Rajamangala University of Technology Srivijaya; Nakhon Si Thammarat 80110 Thailand
3. Faculty of Science and Industrial Technology; Prince of Songkla University; Surat Thani 84000 Thailand