Use of visible pulsed photoacoustic technique for the non-destructive measurements of absorption coefficients, thermal diffusion and viscosity properties of natural and clay-blended rubber nanocomposites

Abstract

The paper reports the use of visible 532 nm wavelength of 7 nS pulse obtained from Q-switched Nd:YAG laser at 10 Hz repetition-based time-domain photoacoustic spectroscopy for measuring the effect of carbon and inorganic fillers blending in natural rubber (NR)/chlorobutyl rubber (CIIR). All the measurements were carried out in the indigenously designed solid photoacoustic (PA) cell of 5×5×6cm3 made of aluminum. A pre-polarised microphone of 50 mV/Pa responsivity coupled with a pre-amplifier was used as the sensor. The time-domain PA signal was recorded using a 200 MHz oscilloscope. The time-domain signal was converted into frequency-domain signal using indigenously designed data acquisition software developed using lab view software. The experimental data were also used to measure the absorption coefficients in the 1.672--4.48cm-1 range. The absorption coefficient value varies with respect to the variation of clay percentage in the rubber matrix. We also calculated the thermal diffusivity, thermal diffusion coefficient and penetration depth as 1.0405--1.0698×10-5cm2s-1, 8.165--8.602cm-1, 1162--1224.6μm, respectively. Finally, we have ascertained the effect of fillers on the viscosity of natural and chlorobutyl rubber samples using Einstein–Guth–Gold equation and determined the size of the filler particles.