The Effects of Different Physical Fields on Swelling Kinetics of PMAA-LTA Zeolite Composite Hydrogel Under Controlled Isothermal Conditions

Abstract

Composite hydrogels are the subject of intensive research due to there specific 3D cross-linked structure with extraordinary physical and chemical properties which enables variety of applications In spite of increasing interest for using different external fields in physical-chemical processes, three are no available literature data about the effects of external fields on swelling and swelling kinetics of hydrogels. Therefore, the effects of (conventional) thermal (TH), ultrasonic (US) and microwave (MW) fields, on the swelling degree and swelling kinetics. A sample of poly(methacrylic acid) (PMAA) xerogel with 10%wt of LTA-zeolite (PMMA-LTA) was synthesized and thoroughly characterized. The isothermal kinetic swelling curves were determined within a temperature range T= 293-323K in the TH, US and MW fields. The results were well fitted with the Peppas’ kinetic model. At all applied fields, with an increase in temperature, there is an increase in the equilibrium swelling degree (SDeq) and the swelling rate constant (k), while the parameter of Pepass's model (n) decreases. The maximum value of SDeq and parameter n is achieved at TH, while the US assisted process leads to the maximum value of k. The minimum value of the activation energy (Ea) and at the same time the maximum value of the pre-exponential factor (lnA) lnA were achieved by applying the MW field. The influence of US and MW fields on the diffusion of water molecules through the polymer network, activation of the polymer network for swelling and relaxation of the polymer network was analysed.