水性纯丙乳液的合成及单体配比对乳液附着性能的影响

Synthesis and adhesion properties of waterborne polyacrylate emulsions with different mass ratios of hard/soft monomer

摘要:

以甲基丙烯酸甲酯(MMA)、丙烯酸异辛酯(2-EHA)分别为硬单体、软单体，甲基丙烯酸(MAA)为功能单体，过硫酸铵(APS)为引发剂，十二烷基硫酸钠(SDS)、脂肪醇聚氧乙烯醚(AEO-9)为乳化剂，采用半连续种子乳液聚合方法合成单体配比不同的水性聚丙烯酸酯乳液。利用衰减全反射-傅立叶变换红外光谱、核磁共振氢谱、凝胶渗透色谱、热重分析和动态热机械分析层测定水性聚丙烯酸酯的结构及性能。结果表明：随着硬软单体比的减小，聚丙烯酸酯乳液的粒径约为100nm；聚丙烯酸酯共聚物的低分子量部分，数均分子量约为3万，重均分子量约为5万；乳液膜的热分解温度从327.5℃升高到343.5℃，玻璃化转变温度从21℃降至-3.5℃；乳液的表面张力从39.83mN/m降至36.71mN/m、界面张力从19.01mN/m降至4.87mN/m、接触角从62.6°降到27.8°，附着牢度从50%提高到95%，当硬软单体比为7：13时，乳液的润湿性最好，附着牢度最高，满足乳液在BOPP薄膜上的应用要求。说明提高聚合物中软单体含量有利于提高乳液的润湿性，从而提高乳液的附着力。

Abstract:

The waterborne polyacrylate emulsions with different mass ratios of hard/soft monomer were synthesized by semi-continuous emulsion polymerization technology using methyl methacrylate (MMA), 2-ethylhexyl acrylate (2-EHA), methylacrylic acid (MAA) as hard monomer, soft monomer and functional monomer respectively, ammonium persulfate (APS) as initiator, Sodium dodecyl sulfate (SDS) and AEO-9 as emulsifier. Attenuated total reflection -Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, gel permeation chromatography, thermogravimetric analysis and dynamic thermomechanical analysis were utilized to characterize the bulk structures and properties of waterborne polyacrylate. The results show that the particle size of waterborne polyacrylate emulsions was approximately 100nm, the number average molecular weight and weight average molecular weight of lower molecular weight of polyacrylate copolymers was about 30000g/mol and 50000g/mol respectively. For polyacrylate film, the decomposition temperature increased slightly from 327.5℃ to 343.5℃ and the glass transition temperature decreased from 21℃ to -3.5℃. Moreover, the surface tension of polyacrylate emulsion decreased from 39.83mN/m to 36.71mN/m, the interfacial tension between emulsion and BOPP film decreased from 19.01mN/m to 4.87mN/m, the contact angle of emulsions on BOPP film decreased from 62.6° to 27.8° and the adhesion ratio increased from 50% to 95% with the decreases of mass ratios of hard/soft monomer, indicating that the improvement of the wettability of emulsions was conducive to obtain good adhesion. The wettability of emulsion is the best and the fastness is the highest when the mass ratio of hard/soft monomer is 7/13, which can satisfy the application requirement of polyacrylate emulsion on BOPP film.