高分子量聚乙烯醇增强冰的研究

EFFECT OF HIGH MOLECULAR WEIGHT PVA ON MECHANICAL PROPERTIES OF ICE

以本体光聚合法制备的高分子量聚乙烯醇(HMWPVA)为增强剂,考察了增强冰的力学性能.当HMWPVA的浓度为3%(质量分数)时,增强冰的拉伸强度、断裂伸长率、压缩强度和压缩模量分别为普通冰的11.7,3.5,2.3和2.1倍.对比试验发现PVA分子量对冰的拉伸性能影响较大,对冰的压缩性能影响较小.此外,在室温29℃时纯冰的融化时间为5 min,而4%HMWPVA增强冰的融化时间长达240 min.

A sample of polyvinyl acetate with Mn=1.48×106（by GPC） was obtained by bulk photo-polymerization,and then it was conversed into poly（vinyl alcohol） with Mη=2.3×10^5,as HMWPVA thereafter.The specimens of ice strengthened by HMWPVA were prepared per following procedures：（1） the aqueous solutions of HMWPVA with predetermined concentrations were prepared and then degassed;（2） poured the above solutions in models and then put them in a-18℃ refrigerator for over 48 h.The tensile and compression testing was performed at-18℃.It showed that with addition of 3%（mass fraction） HMWPVA,the values of the tensile strength,elongation at break,compressive strength and compressive modulus of ice were 11.7,3.5,2.3 and 2.1 times of those of pure ice,respectively.It implied that there was a strong dependence of the tensile strength on the molecular weights of the PVA.Furthermore,the addition of HMWPVA increased the melting time,for example,the melting time of pure ice is about 5 min at 29℃,but the samples with 2%,3% and 4% HMWPVA are 25 min,60 min and 240 min,respectively.