Study On Structure And Properties Of PVA/NaCl Mixing System

In this study NaCl was expected to disrupt the inter and intra chain hydrogen bonding of the PVA chains, weaken the tangle of macromolecules in PVA/NaCl solution. It would induce an increase of hot-draw ratio and be in favor of improvement on mechanical properties. In the article Na+ were considered the 'catalyst' of formation of hydrogen bonds between H20 molecules and PVA macromolecules. Namely, salt ion polarized water molecule in PVA/NaCl solution,and the hydrogen bonds formed between ionized water molecules and PVA decreased the hydrogen bonds among the macromolecules. This study was divided into three parts as follows:Firstly, the viscosity of PVA/NaCl solution(solvent:H20/DMSO=60/40 ; volume ratio) with different NaCl content was discussed. The result showed that the viscosity of PVA/NaCl solution containing 3wt% NaCl was higher than that of PVA/NaCl solutions containning 0, 1, 2, 4, 5wt% NaCl, and the more was DMSO percentage in H20/DMSO solvent, the higher was viscosity of PVA/NaCl solution.Secondly, the effects of NaCl content on structure of PVA/NaCl films, especially on macromolecular hydrogen bonds, were analysed by the optical microscope, the differential scanning calorimetry, FT-IR and Raman spectrum. The results showed that the uniformity of PVA/NaCl film containing 3wt% NaCl was better than that of PVA/NaCl films containning 0,1,2,4,5wt% NaCl, and the former had lower melting temperature ; the degree of crystallization was increased with an increase of NaCl content and then decreased. Besides, the results showed that the uniformity of film casted from PVA/NaCl/H20/DMSO solution was better than film from PVA/NaCl/H20 solution with the same NaCl content.Finally, the strength and modulus of PVA/NaCl fibres with different NaCl content were analysed.It was indicated that the strength of PVA/NaCl fibrewith 3wt% NaCl is higher than that of PVA/NaCl fibres containning 1,2,4,5wt% NaCl when draw-ratio is 4-8.