| Grafting modification is the main one of the means for preparing modified polyolefin. To carry out grafted polyolefins containing special functional groups that have polarity and reactivity can not only improve their performance deficiencies, but also add new performance, which is a simple and effective method to expand uses of polyolefin materials. In recent years, modifying the existing polyolefin to produce functional and high-performance polyolefin materials has been developing rapidly by the reactive processing technology.Ethylene-vinyl alcohol copolymers (EVOH) are one of the three high gas-barrier materials. They are used widely in various fields such as good packing, gasoline tanks, or other materials. EVOH are expected to work as one of the soft materials for no emission of poisonous gas upon incineration and chlorine-free. However EVOH are hygroscopic and the absorbed water lowers their ability to inhibit oxygen diffusion, which is undesirable in food packaging. Introducing crosslinking bonds between polymer molecules by chemical or radiation treatments is a powerful method to reduce the hygroscopicty. But it is difficult for EVOH to cross-link, which can't form gel below 800kGy. The radiation crosslinking of particular ethylene copolymers can markedly be enhanced by introduction of pendant radiation-sensitive functional groups and that reactive melt processing offers an attractive alternative to introduce the pendant groups. EVOH can be activated by the branched-chain groups hydroxyl and occur grafting polymerization with vinyl monomers, and functionalized EVOH may become crosslinked easily by radiation. and EVOH with vinyl monomers as its pendant group can be used as polyfunctional monomers (PFM), which may promote crosslinking as a kind of macromolecules crosslinking promoter and be potential to overcome the unfavorable factors of common PFM and to be applied blending polymers in the or modifying engineering plastics and so on. This paper studies the following elements: 1) preparation, characterization and radiation effects of functionalized EVOH by esterification grafting; 2) whether functionalize EVOH can be used as macromolecules PFM; 3) the effect of enhanced crosslinking of macromolecules PFM on the properties of EVOH/PLA (polylactic acid) blends, and to compare with the effect of the small molecule PFM 4) pre-irradiation induced graft reaction of maleic anhydride onto EVOH.FTIR spectrum of functionalized EVOH show that peak values of neighborhood 1717cm-1 increase corresponding to C=O peak formed by esterification. Because EVOH contains a small amount of unhydrolyzed vinyl acetate unit, we found after EVOH functionalized, the ratio value increased significantly that demonstrated AA and MAH were grafted to the matrix of EVOH by calculating the ratio of the strength of the absorbed peak of -OH and C=O groups (AbsC=O/AbsO-H). The results of gel fraction of functionalized EVOH at different doses showed that EVOH-AA materials become easier to crosslink by radiation, and gel fraction can reach more than 45% after having received a radiation dose of 10kGy. but EVOH-MAH materials that were prepared only when reaction time was 5 min, 2%MAH or reaction time was 10 min, 1%MAH can elevate the gel fraction after irradiated but gel content increased less than that of EVOH-AA. For EVOH-MAH at other processing conditions, gel content changed little as the absorbed dose increased.The results of gel extraction experiment of EA1T1/PLA blends show that the blends can form gel when EA1T1 was used as macromolecular PFM whose content was more than 5%. At the same absorbed dose, gel fraction of blends increased as the content of EA1T1 increased. However the gel content of 20% EA1T1 was more than that of 30% and 40%. The calculated results show that the content of PLA which entered the crosslinking network was more than others and EA1T1 had certain enhanced radiation crosslinking effect, and the best content is 20%. When EA2T1, Et2M1 and Et1M2 were used as macromolecular PFM, gel content of blends increased as the content of PFM, but the calculated results showed that only Et2M1 PFM was used, a little PLA entered the crosslinking network, and Et2M1 PFM had certain enhanced radiation crosslinking effect. When EA2T1 and Et1M2 was used, no or only minimal amount of PLA entered the crosslinking network and enhanced radiation crosslinking was less effective. When Et1M1 was used, whose content was not more than 50%, blends didn't form gel at the absorbed dose below 100kGy. The results of the properties of EVOH/PLA which were enhanced radiation-crosslinked by macromolecular show that mechanical properties EVOH/PLA did not change much, only in the 50/50 system, heat deformation temperature of the blend had been improved. The results of the properties of EVOH/PLA which were enhanced radiation-crosslinked by small molecular PFM show that when the tensile strength of blends that had 3% or 5% PFM at the absorbed dose of 30-50kGy. The heat deformation temperature had been significantly improved at the absorbed dose of 50-100kGy. But the elongation at the breaking and the impact strength didn't change much. Compared to macromolecular cross-linking agent, small molecule PFM was more suitable for enhanced radiation-crosslinking of EVOH/PLA blend.The analysis results of torque and gel content in the process of pre-irradiation reaction grafting of F101 show that the gel content of product increased as the MAH content and changed not much as the absorbed dose with the same content of MAH. It is deduced that reaction was mainly esterification. Infrared spectra of product confirmed that, where a new peak appeared in 1718cm-1 corresponding to C=O in the ester bonds. E171 has a similar pre-irradiation grafting process with F101, but owning the same MAH content, gel content of product is lower than F101 system. Titration results also confirmed that esterification reactions occurred in the grafting process. According to the application, MAH content was below 2% for pre-irradiation grafting of F101 and was less than 3% for E171.
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