Study On Plasticization Of Polyvinyl Alcohol

Water-soluble polyvinyl alcohol fiber has a good acid,alkali,dry heat resistance,it's tasteless and non-toxic when dissolved in water.However,PVA has a lot of hydroxyl groups,which leads to strong hydrogen bonds between moleculars.It makes the melting point of PVA close to the decomposition temperature.Normal PVA is difficult to melt processing.In tradition PVA fibers is made by wet spinning.The technology of wet spinning is complex and the pollution is serious.Realization of PVA melt spinning is important breakthrough,and has scientific significance and economic benefits.The conclusions are as follows:Polyalcohol A as main plasticizer and Polyalcohol D as auxiliary plasticizer were used to plasticize PVA.The melting point,crystallization temperature of PVA decreased when the ratio of A and D was 7:2.The tensile strength of PVA fiber decreased and the melt flow ability increased with increasing of the amount of plasticizer.When the amount of the compounded plasticizer was 45%,the modified PVA had a melt index of 12.5g/10 min,a melting point of 180.7?,a thermal decomposition temperature of 216.0 ?.The breaking strength of primary fiber was 2.05 c N/dtex,and elongation at break was 64.57%.The low molecular weight PVA has a great influence on the modified PVA blends.With increasing the content of low molecular weight PVA,the melting temperature(Tm)and the initial crystallization temperature(To)of the blends decreased gradually,the crystallization rate first increased and then decreased.The shear sensitivity index,?E? of the PVA blends first increased and then decreased,while nonewtonian index and spinnability showed a tendency to increase first and then decrease.The crystallization rate reached its maximum with 20 % low molecular weight PVA.And the spinnability of the system is best.The nonisothermal crystallization behavior of modified PVA-nucleating agent composite was investigated by differential scanning calorimetry(DSC).The nonisothermal crystallization kinetics of modified PVA was analyzed by Ozawa,Jeziorny and Mo Zhishen methods.The results showed that crystallinity(Xt),crystallization peak temperature(Tc),t1 / 2,crystallization rate depend on the cooling rate significantiy.With increasing of the cooling rate,the crystallization rate constant and the crystallinity were increased.Moreover,at the same cooling rate,the crystallization rate of the PVA-nucleating agent composite was larger than modified PVA.This indicates that the addition of nucleating agent can increase the crystallization rate of the modified PVA and has an effect of heterogeneous nucleation.The Mo Zhishen method could explain the non-isothermal crystallization process of modified PVA better than other methods.With increasing of nucleating agent,the crystallization rate of the modified PVA increased first and then decreased.The apparent viscosity,shear sensitivity index,temperature sensitivity index of the modified PVA melt were increased and the nonewtonian index,spinnability was decreased with increasing of nucleating agent,and the obtained PVA was suitable for melt spinning when the mass fraction was about 1.5%.The results showed that the mechanical properties of modified PVA could be enhanced with thermal treatment at 120 ? in 30min-40 min.