Ultrasonic degradation of polymers: Effect of operating parameters and intensification using additives for carboxymethyl cellulose (CMC) and polyvinyl alcohol (PVA)

Abstract

Use of ultrasound can yield polymer degradation as reflected by a significant reduction in the intrinsic viscosity or the molecular weight. The ultrasonic degradation of two water soluble polymers viz. carboxymethyl cellulose (CMC) and polyvinyl alcohol (PVA) has been studied in the present work. The effect of different operating parameters such as time of irradiation, immersion depth of horn and solution concentration has been investigated initially using laboratory scale operation followed by intensification studies using different additives such as air, sodium chloride and surfactant. Effect of scale of operation has been investigated with experiments in the available different capacity reactors with an objective of recommending a suitable type of configuration for large scale operation. The experimental results show that the viscosity of polymer solution decreased with an increase in the ultrasonic irradiation time and approached a limiting value. Use of additives such as air, sodium chloride and surfactant helps in increasing the extent of viscosity reduction. At higher frequency operation the viscosity reduction has been found to be negligible possibly attributed to less contribution of the physical effects. The viscosity reduction in the case of ultrasonic horn has been observed to be more as compared to other large capacity reactors. Kinetic analysis of the polymer degradation process has also been performed. The present work has enabled us to understand the role of the different operating parameters in deciding the extent of viscosity reduction in polymer systems and also the controlling effects of low frequency high power ultrasound with experiments on different scales of operation.

Carbon Nanofibers‐Poly‐3‐hydroxyalkanoates Nanocomposite: Ultrasound‐Assisted Dispersion and Thermostructural Properties

“…This was attributed to the increase in polymer degradation (hence control crystallinity) with a decrease in applied ultrasonic frequency. There is a wealth of experimental information that showed increased polymer degradation with a decrease in insonation frequency [49,50]. At 40 kHz sonication frequency, negligible decrease and increase in the viscosity average molecular weight ( ), and crystallinity ( ) were observed, respectively, when irradiation time was prolonged from 30 minutes to 40 minutes.…”

Sonochemical Grafting of Poly(vinyl alcohol) onto Multiwall Carbon Nanotubes in Water

“…25 Sonication power, irradiation time, and frequency mainly determine the degradation of polymers, the change of molecular weight, and their limiting molecular weight. 20,[26][27][28] Figure 1 explains the reduction of molecular weight of PVA during ultrasonication under 300 and 500 W at different irradiation time due to ultrasonic degradation. It is noted that frequency of applied ultrasound was 20 kHz.…”

“…19 Lately, Gogate et al, investigated the reduction of intrinsic viscosity of carboxymethyl cellulose and PVA solutions. 20 The ultrasonic degradation of the polymer is often expressed as the reduction in the molecular weight of polymers under ultrasound. An interesting fact is that the polymer chains are severed statistically around the middle of them, leaving polymeric radicals at the ends.…”

The Study of Ultrasonic Degradation of Superabsorbent Hydrogels

“…Ultrasound, photo, and chemical methods require less energy for polymer degradation. Further, interaction between them and the polymeric systems can help find the degradation pathways or mechanisms [8][9][10][16][17][18].…”