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 $5 \times 5 \times 6 \,\hbox {cm}^{{3}}$ 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 $1.672\hbox {--}4.48 \,\hbox {cm}^{{-1}}$ 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 $1.0405\hbox {--}1.0698 \times 10^{\mathrm {-5}}\,\hbox {cm}^{\mathrm {2}}~\hbox {s}^{{-1}}$, $8.165\hbox {--}8.602 \,\hbox {cm}^{{-1}}$, $1162\hbox {--}1224.6 \,\mu \hbox {m}$, 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.