侧链为亚乙氧基结构的EVOH梳型聚合物的合成

以乙烯-乙烯醇共聚物(EVOH)为原料，制备了一种主链为疏水的聚乙烯链段，侧链具有亚乙氧基结构的多羟基梳形聚合物，用元素分析法、凝胶渗透色谱法、核磁共振谱法对其进行了结构表征；用热重分析法和示差扫描量热法对其热学性能进行了表征。结果表明，接枝后产物的玻璃化转变温度在-52--40℃之间，熔点在55～600℃之间，由于侧链的引入破坏了EVOH的结晶，因此梳形聚合物的热分解温度比EVOH降低了约20℃。     

乙烯乙烯醇共聚物与聚乙烯共混物的性能研究

以HDPE-g-MAH为相容剂,分别制备EVOH/HDPE二元共混物和EVOH/PA6/HDPE 三元共混物.分别研究EVOH/HDPE和EVOH/PA6/HDPE共混物的阻透性、加工流动性、物理机械性能及其微观形态结构.从SEM可以看出：共混体系呈两相结构,分散相HDPE和PA6以球状均匀的分散在连续相EVOH中.二元体系中,随着HDPE质量分数的增加,共混体系的阻透性能略有下降;加工流动性有所提高;当m（EVOH）∶ m（HDPE）∶ m（DPE-g-MAH）为100∶15∶5时,共混体系的拉伸强度和冲击强度达到最大.与二元体系相比,三元体系的阻透性能和机械性能不如二元体系.     

Incorporating amylopectin in poly(lactic acid) by melt blending using poly(ethylene‐co‐vinyl alcohol) as a thermoplastic carrier. (I) morphological characterization

In this study, the possibility of using a biodegradable grade of thermoplastic poly(ethylene‐co‐vinyl alcohol) with high (71 mol %) vinyl alcohol (EVOH‐29), as a carrier to incorporate the renewable and biodegradable component amylopectin (AP) into poly(lactic acid) (PLA) through melt blending, was investigated. The effect of using a plasticizer/compatibilizer (glycerol) in the blend systems was also investigated. In a first step, the EVOH/AP blends were produced and thereafter, in a second step, these were mixed with PLA. In this first study, the blend morphology was investigated using optical microscopy, scanning electron microscopy and Raman imaging spectroscopy and the thermal properties were measured by differential scanning calorimetry. Despite the fact that EVOH and AP are both highly polar, their blends were immiscible. Still, the blends exhibited an excellent phase dispersion on a micron level, which was enhanced further by the addition of glycerol. A good phase dispersion was finally observed by incorporation of the latter blends in the PLA matrix, suggesting that the proposed blending route can be successfully applied for these systems. Finally, the Differential scanning calorimetry (DSC) data showed that the melting point of EVOH dropped in the EVOH/AP blends, but the properties of the PLA phase was still relatively unaffected as a result of blending with the above components. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Novel glycopolymers containing aminosaccharide pendant groups by chemical modification of ethylene-vinyl alcohol copolymers

Ethylene-vinyl alcohol, EVOH, copolymers with two different vinyl alcohol compositions have been modified to incorporate different reactive functional groups by using phthalic anhydride, chloroacetyl chloride and 4-nitrophenyl chloroformate. Moreover, coupling reactions between EVOH copolymers functionalized with 4-nitrophenyl carbonate groups and three aminosaccharides (d-(+)-glucosamine, d-(+)-galactosamine and d-(+)-mannosamine) have been carried out in dimethyl sulfoxide at 70 °C. The structure of the resulting functionalized copolymers and new glycopolymers was confirmed by FTIR, ¹H and ¹³C NMR. In addition, the thermal characterization of glycopolymers has been performed by DSC. A unique thermal transition, ascribed to the glass transition, is observed in both glycopolymer series. The semicrystalline character of the initial EVOH copolymers is vanished and complete amorphous polymeric materials are obtained since the resulting glycopolymers present relatively long and bulky pendant chains impossible to be included in the EVOH crystallites.     

Biodegradable composites based on starch/EVOH/glycerol blends and coconut fibers

Unripe coconut fibers were used as fillers in a biodegradable polymer matrix of starch/ethylene vinyl alcohol (EVOH)/glycerol. The effects of fiber content on the mechanical, thermal, and structural properties were evaluated. The addition of coconut fiber into starch/EVOH/glycerol blends reduced the ductile behavior of the matrix by making the composites more brittle. At low fiber content, blends were more flexible, with higher tensile strength than at higher fiber levels. The temperature at the maximum degradation rate slightly shifted to lower values as fiber content increased. Comparing blends with and without fibers, there was no drastic change in melt temperature of the matrix with increase of fiber content, indicating that fibers did not lead to significant changes in crystalline structure. The micrographs of the tensile fractured specimens showed a large number of holes resulting from fiber pull‐out from the matrix, indicating poor adhesion between fiber and matrix. Although starch alone degraded readily, starch/EVOH/glycerol blends exhibited much slower degradation in compost. Composites produced 24.4–28.8% less CO₂ compared with starch in a closed‐circuit respirometer. Addition of increasing amount of fiber in starch/EVOH/glycerol composite had no impact on its biodegradation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Application of FTIR spectroscopy to determine transport properties and water-polymer interactions in polypropylene (PP)/poly(ethylene-co-vinyl alcohol) (EVOH) blend films: Effect of poly(ethylene-co-vinyl alcohol) content and water activity

This paper reports the use of FTIR spectroscopy along with gravimetric analysis to simultaneously study water sorption, transport properties and water-polymer interactions in PP/EVOH films at 25 °C, as a function of EVOH content and water vapour activity. The results indicate the existence of two different mechanisms, below (dual-mode) and above a critical concentration value close to the clustering limit activity. Several spectroscopically distinguishable “types” of sorbed water molecules with different diffusion rates have been detected, and their evolution as a function of the penetrant concentration followed. The main changes in the water structure take place from the clustering limit activity onwards. Significant differences both in the state of water and diffusion sequence of free/bound water have been found between 90/10 PP/EVOH films and blends with EVOH content ≥20%, suggesting not only composite-dependence but also morphology-dependence.     

高阻隔性树脂EVOH在肉类包装中的应用

介绍了肉类及制品包装的形态和发展动向以及阻隔包装的概念,EVOH能有效地防止食品变质从而延长保质期.     

Barrier property by controlled laminar morphology of LLDPE/EVOH blends

Using the extrusion blown film process, we obtained linear low density polyethylene (LLDPE)/ethylenevinyl alcohol copolymer (EVOH) blends with an improved barrier property by generating a laminar structure of the dispersed phase in the matrix phase. This laminar morphology induced by drawing and blowing was found to result in a significant decrease in toluene permeability with only 10 wt% EVOH. Effects of compatibilizer content and processing parameters such as blending sequence, screw configuration, and stretch ratio on the toluene permeability and morphology of the blends were investigated. It was revealed that the optimum amount of compatibilizer, maleic anhydride grafted LLDPE, should be used to improve the barrier property of the LLDPE/EVOH blends with a well developed laminar structure. The blending sequence had a significant influence on the permeability of the blends. The blend films exhibited a more pronounced laminar structure when all blend components were simultaneously melt blended in a single screw extruder. In addition, the screw configuration designed to impart a low shear stress and the balanced stretching in the machine and transverse directions were more favorable processing conditions in obtaining high barrier blends.     

Limonene transport and mechanical properties of EVOH and nylon 6,6 films as influenced by RH

The transport properties of d‐limonene through ethylene vinyl alcohol copolymers (EVOH) and nylon 6,6 films as functions of relative humidity (RH) and temperature were studied. Permeation properties of these polymers were strongly influenced by temperature and RH. Compared to the EVOH films, the nylon 6,6 film had much greater limonene permeability. Mechanical property studies indicated that both the tensile modulus and yield strength of the EVOH films decreased with an increase in RH. The polymer changed from being stiff and brittle at low RH to being soft and ductile at high RH. In addition, ethylene content and orientation were found to affect the transport and mechanical properties of limonene through EVOH polymers. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1949–1957, 2001     

Water effect on the morphology of EVOH copolymers

The effect of water on the morphology of four ethylene vinyl alcohol copolymers (EVOH) with different ethylene contents was studied by differential scanning calorimetry (DSC). EVOH film samples equilibrated in controlled atmospheres at different relative humidities (RH) and 23°C were analyzed. Under dry conditions, the glass transition temperature (T_g) was unaffected by copolymer ethylene content. As RH increases, T_g decreases. It seems that the presence of water within the polymer matrix results in plasticization of the polymer. T_g varies from around 50°C (dry) to below room temperature. EVOH copolymers are glassy polymers when dry and rubbery polymers at high RHs. Fox and Gordon–Taylor's equations well describe T_g depletion at low water uptake, although severe water gain results in a considerable T_g decrease, which is not predicted by these theories. Melting temperature, T_m, and enthalpy, ΔH_m, were also analyzed. When dry, T_m decreases as ethylene content increases. No significant water effect was found on either T_m or ΔH_m. Hence, crystallinity seems to be unaffected by water presence. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1201–1206, 1999