全氟物改性煅白的防吸湿机理

摘要

对煅白表面锚固偶氮二氰基戊酸引发全氟烷基乙基丙烯酸酯(FM)聚合而制备的防吸湿煅白进行研究，利用 XPS、IR、DSC、TG、SEM 物理吸收和接触角测量等方法对改性前后煅白的结构、比表面积、形貌和疏水接触角等进行表征，并分析改性后煅白吸湿性降低的原因和机理。结果表明：煅白表面发生了偶联、锚固及聚合反应。锚固引发剂的煅白引发FM原位分散聚合而制得防吸湿煅白，其吸湿率随FM质量分数的增加而降低，当FM质量分数达到7%时，吸湿率不再下降，改性后煅白1 h的吸湿率由1.39%下降到0.017%；聚全氟烷基乙基丙烯酸酯(PFM)的接枝率为0.5%、接枝效率为26.6%，煅白表面出现一层连续而完整的全氟聚合物膜，其厚度约为8 nm。%4,4'-Azobis(4-cyanovaleric acid) (ACPA) was anchored onto the surface of calcined dolomite and radical graft polymerization of perfluoroalkylethyl acrylate (FM) from the modified calcined dolomite through dispersion polymerization were investigated. The structure, specific surface area, morphology and hydrophobic contact angle of calcined dolomite surface were characterised by XPS, IR, DSC, TG, SEM, physical absorption and contact angle measurement, and the reason and mechanism on the decreasing the moisture absorption rate of calcined dolomite after the modification were studied. The results show that the coupling, anchoring and polymerization reactions happen on the surface of calcined dolomite. Poly (Perfluoroalkylethyl acrylate) (PFM) is effectively grafted onto calcined dolomite through the initiation of anchored ACPA during in-situ dispersion polymerization. It shows that the moisture absorption rate of calcined dolomite decreases with increasing of the mass fraction of FM. When the mass fraction of FM is 7%, The moisture absorption rate decreases from 1.39% to 0.017% after modification for 1 h. The grafting rate and efficiency of PFA are 0.5% and 26.6%, respectively. The PFM/calcined dolomite composite particles have a continuous and complete layer of polymer membrane on the surface, and the thickness is about 8 nm.