Improvement of the study on polarization current of filler added natural rubber / Mohd Hasrul Naim Omar

The paper describes the polarization current characteristics of filler added natural rubber. There are many parameters that can be employed for predicting the insulation properties and the charging and discharging is one of them. One of the ways to observe the charging and discharging activities is by measuring the polarization and depolarization currents. In this study, samples of natural rubber filled with varying amount of fillers were moulded and measurement will be focused on their polarization current, which is through their charging processes. The measurement of the samples is conducted by the use of Keithley 6517A Electrometer, which is interfaced to and controlled by a personal computer via a computer program using the TestPoint™ Software. The samples are placed on a specially designed test jig. The polarization current process is set for 5 minutes (300 sec) with 500 V DC injected between the terminals of the test jig. Fillers of three types namely, French Chalk, China Clay and Carbon Black, were added in varying amount to the natural rubber. Natural rubber with French Clay, China Clay and Carbon Black used as a sample because the cost are cheaper, easy to get locally and compatible in production as a samples. For all the samples, certain chemicals have to be added to ensure proper vulcanisation and long lasting, and they are Zinc Oxide, Stearic Acid, Ozone Wax, Colour (Green), Sulphur, MBTS and Nonox CNS, which act as additives, ozone wax, colour, vulcanizes agent, accelerator, and antioxidant agent, respectively. For the case of French Chalks and China Clay, it is found that filler amount of 30 phr or less proved to improve the insulating properties of natural rubber. This is evident from the magnitudes of the polarization current. For the case of Carbon Black as filler, it is found that any amount of more that 10 phr increases the material's conductivity and this is also evident from the polarization current magnitudes.