二步法聚丙烯/丙烯酸表面接枝聚合研究

STUDY ON SURFACE GRAFTING POLYMERIZATION OF CPP/AA SYSTEM WITH TWO-STEP METHOD

研究了二步法聚丙烯膜表面的丙烯酸接枝反应 .实验发现 ,以醋酐为溶剂的反应体系所得接枝率明显好于以水为溶剂的体系 ;接枝率随光敏剂浓度、单体浓度增大而增加 ;提高反应温度 ,可使接枝率明显增大 ;接枝后的聚丙烯膜表面亲水性可明显改善 .并用红外光谱证实了丙烯酸在聚丙烯膜表面的接枝 .

Surface grafting polymerization of cast polypropylene (CPP)/acrylic acid( AA) system was studied with two-step method, which is a novel technique advantageous over traditional surface grafting polymerization initiated by UV. It consists of two steps. Firstly, dormant groups (semi-benzopinacol) were introduced on the CPP film under UV irradiation in the presence of benzophenone ( BP) solution; and then, AA was grafted on the substrate surface by thermoactivating polymerization. The principle is as following, after BP is excited with UV irradiation, it extracts the H atoms from CPP surface and is reduced into semipinacol free radicals, meanwhile macromolecular free radicals are produced on CPP film surface. Because of spatial hindrance originated from its aromatic group, it is difficult for semipinacol free radicals to perform coupling termination and so does the surface radical. If no monomer was available, these two kinds radicals will combine. When CPP film with dormant groups is heated in a monomer solution, the C-C bonds of surface semipinacol groups break into the surface free radicals and semipinacol free radicals. The surface radicals induced monomer to propagate, result in grafting chains; whileas the reactivity of semipinacole free radical is too low to initiate grafting polymerization. Consequently, this method has two advantages:high grafting efficiency and suited to more monomers which can not be used directly in traditional photografting polymerization. The results show that acetic anhydride is an ideal solvent for CPP/AA surface grafting system; grafting yield increases with the growth of photosensitizer and monomer concentration; and polymerization temperature has positive effect on grafting yield. The contact angle of grafted CPP film against water decreases with the increase of grafting yield. In addition, the grafted CPP-g-AA film was identified by FTIR spectra.