Physical Chemistry of Crosslinking

Abstract

Crosslinked cotton fabrics suffer significant losses in strength and abrasion resistance. In order to understand why these losses occur and also to reduce them, the physical chemistry of the process of crosslinking and the role of adsorption in the crosslinking reaction were studied. An attempt is made to relate adsorption and reactivity of different cyclic urea derivatives (DMEU, DMPU, DHEU, and DMDHEU) to the molecular structure, solution properties, pH, nature and concentration of catalyst, temperature, and time of reaction. Solution properties of crosslinking compounds were determined from measurements of electrical conductivity and the depression of the freezing points of aqueous solutions of the crosslinking compounds. A study on chemisorption with different cyclic urea derivatives showed that the maximum chemisorption takes place at pH 2.5 with DMEU and DMPU, and at 0.8 and zero pH with DHEU and DMDHEU, respectively. The kinetics of chemisorption in these crosslinking compounds revealed that the amount of DMEU and DMPU chemisorbed increases initially with time and then decreases and finally reaches an equilibrium value. The chemisorption of DHEU and DMDHEU increase with time and finally reach an equilibrium value. The data show that the chemisorption of these crosslinking compounds are pseudo first-order reactions with respect to the concentration of the crosslinking agent. Equilibrium physical and chemisorption for all the four crosslinking compounds were studied and found to be of the Langmuir type. The thermodynamic parameters such as affinity, enthalpy, and entropy of chemisorption were calculated. The saturation value for different crosslinking compounds are found to be in the order DMEU > DMPU > DHEU > DMDHEU.