膨润土土工合成材料的研究

Synthesis of A New Type Bentonite Geosynthetic Clay Liner

将所合成的相对分子质量约为3-4万的聚丙烯酰胺（PAM）与甲醛反应使之羟甲基化,然后将羟甲基化聚丙烯酰胺和单体丙烯酰胺（AM）脱水缩合,得到产物改性聚丙烯酰胺.适宜的反应物摩尔比n（PAM）∶n（甲醛）∶n（AM）=1∶0.6∶0.6,羟甲基化转化率可达99%以上,丙烯酰胺转化率可达93%以上.改性聚丙烯酰胺以过硫酸铵为引发剂,N,N′-亚甲基双丙烯酰胺为交联剂在室温下发生交联反应.其优点是交联速度快、聚合放热温度低、在侧链发生交联反应、抗水解能力强,吸水膨胀倍数与膨润土相当.将改性聚丙烯酰胺与膨润土混合（其中膨润土质量约占70%）制成的膨润土土工合成材料,其体积膨胀率为190%,基本达到我国建筑行业标准实用要求.该产品经久耐用,为土工合成材料的制备技术探索了一条新路.

A room temperature cross-linking polyacrylamide（PAM） was synthesized in this study. The PAM can be used as adhesive for geosynthetic clay liner（GCL）. First a polyacrylamide with low relative molecular weight（3× 10^4-4× 10^4） was synthesized. Then the polyacrylamide with low relative molecular weight was hydroxymethylated with formaldehyde. Finally the hydroxymethylated polyacrylamide and acrylamide（AM） reacted to form the modified polyacrylamide. The suitable mol-ratio of reactants n（PAM） ： n （formaldehyde） ： n（AM） is 1 ： 0.6 ： 0.6, the conversion rate of hydroxymethylation reaction is above 99% and the conversion rate of AM is above 93 %. At room temperature the modified polyacrylamide, cross-linking agent N,N＇-methylene-bis- （acrylamide） and initiator ammonium persulfate can cross-link. The merit of this process is that cross-linking speed is quicker, the temperature of polymerization is lower; the cross-linking is at side chain; the anti-hydrolyzation ability is strong and the water absorption ability of the cross-linked polyacrylamide is close to bentonite. The volume expansion rate of GCL which is made by mixing the modified polyacrylamide and the bentonite （about 70%） is about 190%, and it basically reaches the building industry standard in China. This product is durable. It will probe a new road for synthetic technique of the GCL.