冷冻温度对聚乙烯醇水凝胶性能的影响

Influence of freezing temperatures on the properties of polyvinyl alcohol hydrogel

目的:冷冻温度对制备性能优良的聚乙烯醇水凝胶有较大的影响,拟通过采用反复冷冻-融化方法制备聚乙烯醇水凝胶,探讨在不同冷冻温度下制备的聚乙烯醇水凝胶的物理性能和力学性能,寻求制备聚乙烯醇水凝胶的最佳冷冻温度。方法:实验于2007-04/06在中国矿业大学材料学院摩擦学与可靠性工程实验室完成。实验选用白色絮状的聚乙烯醇20-99作为原料,按一定比例将聚乙烯醇溶于去离子水中,在恒温水浴箱中于90℃下加热4h,配制成一定浓度的聚乙烯醇水溶液;然后将聚乙烯醇水溶液在超低温冷冻储存箱中冷冻成型,冷冻温度分别设为-10℃,-15℃,-20℃,-25℃,-30℃,冷冻时间为6～10h,取出试样后室温下融化2～4h,上述冷冻-融化过程重复3次制得聚乙烯醇水凝胶。实验选用聚乙烯醇的质量分数为15%,制备不同厚度的聚乙烯醇水凝胶试样若干备用。测试各种冷冻温度下制备的聚乙烯醇水凝胶的密度、含水率、再溶胀性和结晶度等物理性能以及弹性模量和应力松弛等力学性能。结果:聚乙烯醇水凝胶的物理性能和力学性能随冷冻温度的不同而明显变化;-20℃反复冷冻融化制备的聚乙烯醇水凝胶具有较好的物理性能和力学性能,其密度为1.06543g/cm3,含水率为82.61%,再溶胀率达238.8%,结晶度为74.03%,弹性模量为0.0974MPa。结论:-20℃是反复冷冻-融化法制备聚乙烯醇水凝胶的常选冷冻温度。

AIM： Freezing temperature may affect the properties of polyvinyl alcohol （PVA） hydrogel, this study was aimed to prepare PVA hydrogel by reiterative freezing-thawing method, investigate the physical mechanical properties of PVA hydrogel at different freezing temperatures, and research the best freezing temperature for preparing the PVA hydrogel. METHODS： From April to June in 2007, the experiment was accomplished at the laboratory of Tribology and Reliability Engineering in School of Material Science and Engineering at China University of Mining and Technology. White flocculent PVA 20-99 was dissolved in the deionized water and heated for 4 hours in thermostatic waterbath box at 90 ℃, in order to prepare PVA solution. Afterwards PVA solution was frozen in different freezing temperatures （-10 ℃, -15 ℃, -20 ℃, -25 ℃, -30 ℃） for 6-10 hours, and then thawed at room temperature for 2-4 hours. The freezing-thawing process was repeated for 3 times to prepare PVA hydrogel, and PVA hydrogel samples of different thickness were also obtained at the mass fraction of 15%. Their physical performances such as density, water containing rate, swellability, crystallinty, and mechanical performances such as modulus of elasticity and stress relaxation were measured. RESULTS： The freezing temperature obviously influenced the physical and mechanical performances of PVA hydrogel. PVA hydrogel sample at the freezing temperature of -20 ℃ had good physical and mechanical performances, with density of 1.065 43 g/cm^3, water containing rate of 82.61%, swellability of 238.8%, crystallinty ratio of 74.03%, and elastic modulus of 0.097 4 MPa. CONCLUSION： -20 ℃ is the common temperature of the freezing-thawing method when preparing PVA hydrogel samples.