紫外光引发LDPE膜接枝含氟丙烯酸酯的研究

通过紫外光引发表面接枝聚合反应的方法 ,把含氟丙烯酸酯单体R 5 6 1 0引到LDPE薄膜上 .对经丁酮抽提后的接枝膜进行FTIR、ESCA、SEM和DSC等表征 ,证实含氟聚合物以化学键的方式接枝在LDPE基体膜上 .在一定范围内 ,增加紫外光强、引发剂和单体浓度以及反应温度等均有利于提高接枝率 .经计算R 5 6 1 0的紫外光引发接枝聚合反应总活化能为 5 4 2kJ mol.接枝膜的接触角随着接枝率的提高逐步增大 ,直至趋于恒定 .作者提出接枝膜存在一个在接触角测定时影响基体膜与探测水滴相互作用过程的边界层 .当接枝率较低、接枝层厚度小于边界层临界厚度时 ,基体LDPE影响接触角的大小 ,但随着接枝率提高 ,接枝层逐渐变厚 ,氟聚合物层对接触角的贡献逐渐占优势 ,导致接触角随之增大 .当接枝率超过一定值以后 ,接枝层厚度超过边界层临界厚度 ,接枝层对接枝膜的接触角起全部贡献 ,接触角测定值随之稳定

FLUORINATED ACRYLATE-GRAFTED LDPE FILMS FROM UV-INDUCED PHOTOGRAFT POLYMERIZATION

One kind of fluorinated acrylate monomer,R5610,was grafted onto the surface of LDPE films by UV-induced photograft polymerization.The existence of a fluorinated polymer layer and its linkage with the LDPE substrate through chemical bonds were confirmed by FTIR,ESCA,SEM and DSC measurements on the butanone-extracted grafted films.It's found that a moderate increase of the UV intensity,concentration of both photoinitiator and monomer,and reaction temperature favored the improvement of grafting yield.The overall activation energy for the photograft polymerization reaction of R-5610 on LDPE was calculated to be 54.2 kJ/mol.The surface contact angles of the grafted films were found to increase with the improvement of grafting yield before they became constant,which implied that there could be a boundary layer that influenced the interaction between the LDPE substrate and the probe water drops during the measurement of contact angles.The LDPE substrate interacted with the probe water drop through the boundary when grafting yield of the grafted film was low and the grafted polymer layer was thinner than the critical boundary thickness,which resulted in the similarity between contact angles of LDPE and grafted film.As grafting yield increased,the grafted polymer layer became thicker and the interaction between LDPE substrate and probe water drop was weakened,so the influence of fluorinated polymer on the contact angle became more remarkable and caused the increase of contact angle.When grafting yield went further higher and the thickness of grafted polymer layer exceeded the critical boundary thickness,the interaction between LDPE substrate and probe water drops disappeared,and the contact angle became stabilized thereafter as a result of fluorinated polymer becoming the only one to influence contact angle of grafted films.