Dielectric phenomena in hevea rubber latex and its applications

Hevea rubber latex is a biological product with a complex composition. The basic components of freshly tapped natural rubber latex are 50-80% water, 18-45% rubber hydrocarbon and 2-5% non-rubber constituents. The typical non-rubber constituents are protein, lipids and inorganic salts. In this work the dielectric properties of hevea rubber later have been measured at various moisture contents, temperatures from -30 C to 50 C and frequencies from 10^-3 Hz to 20 GHz. Experimental results have shown that in the liquid state a conductive loss dominated in a range less than 2 GHz, while above 2 GHz the loss mechanism is dominated by dipole orientation of water molecules. However below -5 C, solidified latex shows dielectric behaviour which is almost similar to ice and a relaxation frequency of about 10 KHz. In conclusion, the dielectric phenomena in hevea latex are mainly due to polarisation of water molecules and in the liquid state it is conductive at a frequency lower than 2 GHz. These experimental results give valuable information for the analysis and design of microwave moisture meter and for estimating microwave absorption during microwave heating