Studies On EVOH And Materials With High Property

The expansion of industrial and economic activities results in a continuous demand for new, low-cost materials able to meet increasingly stringent conditions. Polymers are commonly admixed with a variety of both natural and synthetic compounds to improve their performance. Inorganic components used for this purpose are called"fillers"and give rise to"filled polymers"with greater mechanical strength or impact resistance, or reduced electrical conductivity or permeability to gases, such as oxygen, and moisture. In these conventional materials, there is a distinct macroscopic separation between the organic and the inorganic phase without any significant interactions between them. Microscopic dispersion is the most that can be achieved by treating the surface of the inorganic material. Nano-composites, on the other hand, constitute a new class of materials with an ultra-fine phase dispersion (e.g. of clay) of the order of a few nanometers that endows them with unique properties not shared by conventional materials and offers new technological and economic opportunities. Nano-composites can be classified depending on the shape of the nano-filler. Particles are characterized by a three-dimensional nano-size distribution whereas in nano-tubes or whiskers nano-size is limited to two dimensions in space. Finally, in the case of phyllosilicates (e.g. clay) single silicate layers with one-dimensional nano-size can be dispersed in the polymer. 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.Our research group has researched on radiation effect of ethylene-vinyl alcohol copolymers (EVOH). On the basis of this work, my work focuses on the research on the preparation, characterization and radiation effect of EVOH/inorganic nano-composites. Using EVOH-56(VA content 56mol%) and EVOH-68(VA content 68mol%) as matrix and different nano-particles as the filler, different kinds of nano-composites were prepared by melt blending. Tensile tests, FTIR and X-Ray were used to characterize the mechanical properties, rheological properties and morphological structure in order to research and compare the following contents: 1. Effects of nano-particles with different chemical structures on the properties of nano-composites. 2. Effects of nano-particles with different interface structures on the properties of nano-composites. 3. Effects of nano-particles with different aggregation statuses on the properties of nano-composites. 4. Effects of matrixes with different VA contents on the properties of nano-composites. 5. Effect of radiation on the properties of nano-composites. The main results of this work are as followings:1.Effects of nano-particles with different chemical structures, interface structures and aggregation statuses on the properties of nano-composites were researched and discussed using models of interaction among phases of composites and structures of MMT nano-composites. Results show that the less is the parameter B in the model of interaction among phases of composites-TPT equation, the better the interaction among phases of composites, the smaller the adhesion degree of the systems, and the better the mechanical properties of the composites. The value of B of EVOH-56/nano-TiO2 composite is higher than that of EVOH-56/nano-ZnO composite, and so are the mechanical properties. The mechanical properties of treated nano-particles filled composites are better than those untreated nano-particles filled composites. The elongation at break of ZQ-602 coupler treated nano-TiO2 filled composite is higher than that of YGO-1203 coupler treated nano-TiO2 filled composite. Nano-fillers with different aggregation structures have different interaction styles with matrixes, but they exhibit almost the same mechanical properties.2.The value of B of EVOH-56/nano-TiO2 is higher than that of EVOH-68/nano-TiO2 composite, and so are the mechanical properties. The value of B of EVOH-56/nano-ZnO is higher than that of EVOH-68/nano-ZnO composite, and so are the mechanical properties. The mechanical properties of EVOH-56/MMT composites are generally lower than those of EVOH-68/MMT systems. But the elongation at break of EVOH-56/MMT composite has increased to 200% of neat matrix. 3.After radiation, the mechanical properties of all the samples were discussed. It is found that mechanical properties of irradiated nano-composites based on EVOH-68 decrease dramatically, while the mechanical properties of irradiated nano-composites based on EVOH-56 improve at low radiation doses and decrease at high radiation doses, and in general have small changes. For nano-composites with different nano-fillers, different systems have different reactions to radiation. EVOH-56/nano-ZnO system exhibits better endurance to radiation than EVOH-56/nano-TiO2 system. At the irradiation doses of 10M,20M and 60M, The mechanical strength of EVOH-56/ZQ602/nano-TiO2 system improves more than EVOH-56/YGO-1203/nano-TiO2 system. At different irradiation doses, EVOH-56/nano-ZnO system, EVOH-56/nano-TiO2 system, EVOH-56/nano-SiO2 system and EVOH-56/nanoMMT system have different mechanical property trends. However, the mechanical strength of EVOH-56/nanoMMT system improves most, increasing to 140% of neat matrix at the irradiation dose of 20M.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 treaments 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 showe that EVOH-AA materials become easy 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 showe 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 ammount 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 macromlecular 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 occured 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.