Study On Higher A-olefin Based PE Film Hydrophile Modification Agent

A series of amphiphilic copolymer based on poly(long-chain a-olefin) was prepared and used as surface modification agent for low density polyethylene (LDPE) film to make anti-fog agriculture film.Firstly, poly(1-octene-co-l-tetradecene) was prepared with Ziegler-Natta catalyst. The influence of comonomers feed ratio on the molecular weight and the composition of poly(1-octene-co-l-tetradecene) was investigated. As the consumption of1-octene increased, the molecular weight of poly(1-octene-co-l-tetradecene) decreased. The chemical composition of poly(1-octene-co-l-tetradecene) was similar to the feed ratio. Diethyl zinc (ZnEt2) was an efficient chain transfer agent to regulate molecular weight. As the dosage of ZnEt2increased, the molecular weight of poly(1-octene-co-l-tetradecene) decreased. Elevating polymerizaiton temperature can also reduce the molecular weight. Initiated by t-butyl peroxybenzoate (TBPB),maleic anhydride (MAH) was grafted onto poly(1-octene-co-l-tetradecene). The composition of poly(1-octene-co-l-tetradecene) did not affect the content of MAH in poly((1-octene-co-l-tetradecene)-g-MAH. However, as the molecular weight of poly(1-octene-co-l-tetradecene) increased, the content of MAH decreased. Using MAH as reactive groups, polyethylene glycol (PEG) was grafted onto the chain of poly(1-octene-co-l-tetradecene) through esterification reaction. However, the content of PEG was low under the experimental conditions. Poly((l-octene-co-l-tetradecene)-g-MAH) and poly((1-octene-co-1-tetradecene)-g-PEG) were spin coated onto the surface of LDPE film respectively. But these two copolymers could only slightly improve the hydrophily of LDPE film.Secondly, to further increase the content of hydrophilic groups in the amphiphilic copolymers, poly(1-octene-co-t-butyl acrylate) was prepared by free radical polymerization. The influence of polymerization temperature, initiator concentration, polymerization time and comonomer feed ratio on the copolymerization were systematically investigated. The comonomer conversion could be as high as50.2%by increasing the polymerization temperature (>105℃), initiator concentration and polymerization time. As the consumption of1-octene increased, the content of1-octene in poly(1-octene-co-t-butyl acrylate) increased from0to37mol%. By hydrolysis reaction poly(1-octene-co-t-butyl acrylate) was turned into poly(1-octene-co-acrylic acid). Through polyesterification PEG was grafted onto poly(1-octene-co-acrylic acid). Poly((1-octene-co-acrylic acid)-g-PEG) with52.5mol%of PEG was mixed with LDPE film for modification. It could efficiently improve the hydrophilicity of LDPE film. By annealing the modified LDPE film at110℃, the PEG segments rearranged and were enriched on surface of the film. By this surface modification method, the amphiphilic graft copolymer was fixed on the surface of LDPE film. The water contact angle of the modified film was further reduced to as low as58°.