Original Article |
2015, Vol.37, No.6, pp. 713-718
Design and implementation of microwave attenuation measurements to estimate the dry rubber content of natural rubber latex
Pattara Aiyarak and Piti Sunheem
pp. 713 - 718
Abstract
An accurate, quick and practical method for measuring the dry rubber content (DRC) in natural rubber latex is proposed and investigated experimentally, based on microwaves. The concept exploits the microwave absorption of water molecules to infer the DRC. However, various design aspects had to be experimentally investigated. In this study, rectangular waveguide antennae were used for microwave transmission. The latex was placed between two antennae, and the signal was analyzed by a vector network analyzer (VNA). A calibration curve was fitted with least squares regression for sample DRCs ranging from 10.26% to 60.63%. The best linearity with 0.9996 correlation between attenuation and DRC was obtained at 2.36 GHz. To validate this measurement technique, 17 fresh local rubber latex samples were measured both with the slow reference gravimetric determination of DRC that involves oven drying, and with the microwave transmission technique. The measurements had a 0.43 mean error in %DRC, and a 0.9047 correlation to the gravimetric DRC. The study supports potential design and construction of a prototype DRC measurement device for field use.