1. Department of Materials Science and Technology, Faculty of Science, Prince of Songkla University, Songkhla, Thailand
2. Department of Physics, Faculty of Science and Technology, Al-Neelain University, Khartoum, Sudan
3. Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems, Faculty of Engineering Technology, University of Twente, Enschede, Netherlands
4. Malaysian Rubber Board, RRIM Research Station Selangor, Malaysia