新型接枝共聚物EVA-g-PU的研究

通过乙烯一酷酸乙烯共聚物(EVA)的皂化产物与聚醚型聚氨酷预聚体(PU)之间的接枝反应,合成了一种新型的接枝共聚物EVA-g-PU。用13C-NMR和FTIR对共聚物EVA-g-PU进行结构表征。结果表明,PU预聚体成功接枝在EVA主链上。力学性能测试表明,EVA-g-PU接枝聚合物的拉伸强度与断裂伸长率优于纯EVA。动态力学分析(DMA)表明,EVA-g-PU接枝共聚物的储能模量相对于纯EVA有较大程度的提高。热失重(TG)分析表明,PU预聚体的加人能有效改善接枝聚合物的热稳定性能。     

EVA-g-PU的制备与表征

通过乙烯-醋酸乙烯共聚物(EVA)的皂化产物EVAL与聚醚型聚氨酯预聚体(PU)之间的接枝反应,合成了一种新型的接枝共聚物EVA-g-PU,用13C NMR和FTIR对产物进行了结构表征.结果表明,PU预聚体成功接枝在EVA主链上;接枝共聚物的熔点随PU预聚体含量的升高而升高,接枝共聚物的储能模量相对于纯EVA有较大程度的提高,PU预聚体的加入能有效改善接枝聚合物的热稳定性能.     

用螯合树脂分离三价铬离子

含三价铬离子的溶液与含有肼基的螯合树脂接触,可以吸附分离三价铬离子。具体方法是,用肼处理丙烯酸和共聚性乙烯单基聚物的共聚物,或者用肼处理无水马来酸和乙烯单基聚物的共聚物,制成含肼     

低模温玻纤增强PET复合材料的制备与表征

采用差示扫描量热法研究了聚对苯二甲酸丁二醇酯(PBT)、乙烯-醋酸乙烯酯共聚物(EVA)、乙烯-正丁基丙烯酸酯-甲基丙烯酸缩水甘油酯共聚物(PTW)对聚对苯二甲酸乙二酯(PET)冷结晶峰温的影响,发现随着PBT含量的增大,PET的冷结晶峰温;当PBT的添加量为50份时,冷结晶峰基本消失;同时加入20份PBT和15份EVA亦可使冷结晶峰消失;PBT、PTW和EVA在降低冷结晶峰温的同时还有助于提高玻纤增强PET复合材料的冲击强度;在PET/PBT体系中,加入适量的无机填料硫酸钡和滑石粉可使热变形温度达到220℃以上。     

PC/BPT共混体系的研究(Ⅱ)——EVA对共混物性能和形态的影响

本文研究了聚碳酸脂(PC)/聚对苯二甲酸丁二脂(PBT)/乙烯—乙酸乙烯酯共聚物(EVA)三元共混物的性能、形态和组分比的关系。结果表明,加入适量的EVA可提高共混物的拉伸强度和断裂伸长率,聚碳酸酯的熔体流动性亦得到改善。     

低发泡POE／AS／EVA共混材料的研究

利用试验设计方法研究了聚乙烯弹性体（POE）、苯乙烯－丙烯腈共聚物（AS）、乙烯－醋酸乙烯共聚物（EVA）和油（Oil）、碳酸钙（CaCO3）、二氧化硅（SiO2）对低发泡POE／AS／EVA共混材料物理力学性能的影响。实验结果:POE对共混材料的硬度、撕裂强度的影响不大，而拉伸强度、断裂伸长经、压缩永久变形随POE用量的增加而增加；AS对低发泡POE／AS／EVA共混材料的拉伸强度，撕裂强度的影响较小，断理解伸长率、压缩永久变形在一定范围内随AS用量的增加而下降，硬工随AS用量的增加而增加；EVA对共混材料性能的影响不大。     

EVACO共聚物热分解动力学研究

研究了乙烯/醋酸乙烯酯(EVA)二元共聚物和乙烯/醋酸乙烯酯/—氧化碳(E-VACO)三元共聚物的热分解机理和动力学。用 Doyle—Ozawa 积分法处理实验数据,给出分解活化能。结果表明,共单体一氧化碳作为第三组分引入 EVA 共聚物分子链上可以提高其热稳定性。     

EVA/金属复合材料界面及VA含量对其拉伸剪切强度的影响

利用X射线光电子能谱分析了乙烯-乙酸乙烯共聚物(EVA)/Al,EVA/Cu复合材料的界面,测试了不同乙酸乙烯(VA)含量的EVA/Al,EVA/Cu复合材料的拉伸剪切强度。结果表明:EVA与金属复合的界面大多是羰基与金属相互作用的结果;VA含量低时,随着VA含量的增加,与金属反应的羰基数量也会增加,EVA/金属复合材料的拉伸剪切强度也随之增加。但VA含量超过一定程度后,EVA本身的强度下降,从而造成EVA/金属复合材料的拉伸剪切强度整体降低。     

国内外EVA产品的开发现状及进展

介绍了乙烯—醋酸乙烯共聚物(EVA)产品的特性、国内外EVA产品的生产工艺特点、生产现状、产品消费结构及市场前景等，并针对国内EVA产品的消费结构提出了新产品开发建议。     

PP编织袋回收技术研究

研究了苯乙烯－丁二烯嵌段共聚物（SBS），苯乙烯－异戊二烯－苯乙烯接枝共聚物（SIS），乙烯－丙烯酸或丙烯酸酯共聚物（EAA），乙烯－醋酸乙烯共聚的（EVA）和乙烯－辛烯共聚物（POE）几种聚烯增韧剂对废聚丙烯（PP）编织袋回收料的改性效果。研究结果表明，当增韧剂加入量为11份时，SIS的增韧效果最好，悬臂梁缺口抗冲击强度为134.kJ/m^2，比新鲜无规共聚PP13304的缺口抗冲击强度10.8kJ/m^2还高，EAA最低，其缺口抗冲击强度还不到均聚PP1300的缺口抗冲击强度5.8kJ/m^2，其它几种增韧材料的抗冲击强度在1300和1330之间，当用量达到20份时，其抗冲击强度迅速增加，达到15.2kJ/m^2的最高值。     

Melt grafting of poly(ethylene‐vinyl acetate) copolymer with maleic anhydride

Poly(ethylene‐vinyl acetate) (EVA) copolymer was melt grafted with maleic anhydride (MAH) in a twin screw extruder in the presence of peroxide. It is confirmed that MAH has been melt grafted on the backbone of EVA by FTIR using the method of hydrolysis. The NMR analysis suggests that the grafting reaction occurs on the tertiary carbon of main chain of EVA other than the methyl moiety of vinyl acetate (VA) group. The incorporation of VA groups onto the matrix shows a competitive effect on the grafting. The existence of VA groups promotes the extent of MAH graft onto EVA; nevertheless, it also weakens the crystallizability of main chain. When the content of peroxide initiator is 0.1 wt % based on the polymer matrix, the grafting degree increases with increasing the concentration of monomer. When the peroxide content is higher than 0.1 wt %, side reactions such as crosslinking or disproportionation will be introduced into this system. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 841–846, 2006     

Mechanical properties of ethylene–vinyl acetate/polystyrene blends studied by in situ polymerization

This study examined ethylene–vinyl acetate (EVA)‐toughened polystyrene (PS). EVA is well‐known to be incompatible with PS; thus, the PS graft to the EVA backbone (EVA‐g‐PS) was used as a compatibilizer and provided good adhesion at the interface of PS and EVA. In addition, the mechanical properties and impact resistance of the PS matrix were obviously improved by EVA‐g‐PS and by EVA itself. Meanwhile, differential scanning calorimetry results showed that the grafted PS chain influenced the crystallization of EVA; for example, the melting temperature, the crystallization temperature, and the percentage crystallinity related to EVA were reduced. Moreover, the addition of 10% EVA increased the impact strength by a factor of five but reduced the modulus by the same factor. Additionally, a lower number‐average molecular weight EVA delayed phase inversion and resulted in poor mechanical properties. A fracture surface photograph revealed that the major mechanism of EVA‐toughened PS was craze and local matrix deformation. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 699–705, 2003     

Use of EVA-containing mercapto groups in natural rubber–EVA blends. I. Mechanical,thermal, and morphological properties

The effect of ethylene–vinyl acetate (EVA) modified with mercaptoacetic acid on mechanical, thermal, and morphological properties of blends of natural rubber (NR) and EVA copolymers has been investigated. The introduction of EVASH promotes a crosslinking of natural rubber phase as indicated by extraction experiments and microscopy analysis. This crosslinking may be attributed to bonding between sulfhydryl groups along the EVASH backbone and double bonds in rubber phase and may be responsible for the hardness improvement of most of the studied blends. Better results on hardness and ultimate tensile strength with EVASH addition were achieved for NR–EVA (60 : 40) ratio, probably due to cocontinuous morphology of this composition. The influence of EVASH on crystallinity degree of NR–EVA blends was also studied by differential scanning calorimetry. The morphology of the blends was studied through scanning electronic microscopy. © 1995 John Wiley & Sons, Inc.     

EVA弹性体对PHBV的增韧改性研究

采用熔融共混法,通过在聚（3⁃羟基丁酸酯⁃co⁃3⁃羟基戊酸酯） PHBV中添加不同比例含量的乙烯⁃乙酸乙烯酯（EVA）弹性体,制备了一系列PHBV/EVA复合材料,并通过傅里叶红外光谱仪、转矩流变仪、差示扫描量热仪、热失重分析仪、力学性能测试、热台偏光显微镜等设备,对PHBV/EVA复合材料的结构和性能进行表征。结果表明,PHBV与EVA之间的氢键作用、链缠结作用以及相似的主链结构使得二者之间的相容性和分散性较好;随着EVA含量的逐渐升高,PHBV/EVA复合材料的结晶度表现出先升高后降低的趋势;EVA添加量小于10 %（质量分数,下同）时,随着EVA含量的增加,PHBV的球晶数量逐渐增加,球晶尺寸逐渐变小;EVA的添加量为30 %时,PHBV/EVA复合材料的断裂伸长率和冲击强度增长幅度最大,与纯PHBV相比,分别增长了87.8 %和338.4 %。     

Water treeing,AC breakdown,and dielectric loss characteristics of EVA‐OH as a function of conversion rate

Four kinds of ethylene–vinyl acetate–vinyl alcohol (EVA–OH) terpolymers containing different contents of hydroxyl groups were prepared using the transesterification reaction between a ethylene–vinyl acetate (EVA) copolymer and alcohol. Structural and thermal analyses of the EVA‐OH produced were performed with Fourier transform infrared spectroscopy and differential scanning calorimetry. Electrical properties such as water treeing, AC breakdown, and dielectric loss characteristics were investigated. It was found that both water tree length and the probability of water tree generation decreased as a function of hydroxyl group content. AC breakdown characteristics such as average breakdown strength and characteristic breakdown strength (breakdown probability = 63.2%) of EVA improved as a function of the conversion rate of EVA‐OH from acetate to hydroxyl groups. Dielectric loss increased with hydroxyl group content in the low‐frequency range. In contrast, it was observed that dielectric loss decreased with hydroxyl group content in the high‐frequency range. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 420–424, 2006     

The effect of mercapto‐modified EVA on rheological and dynamic mechanical properties of NBR/EVA blends

The effect of mercapto‐modified ethylene vinyl acetate copolymer (EVALSH) on the rheological and dynamic mechanical properties of acrylonitrile butadiene rubber (NBR) and ethylene vinyl acetate copolymer (EVA) blends was evaluated at different blend compositions. The addition of 5 phr of EVALSH in the blends resulted in an increase of the melt viscosity and a substantial decrease of the extrudate swell ratio. These results can be attributed to the interactions occurring between the double bond of the NBR phase and the mercapto groups along the EVALSH backbone. The power–law index also presents a slight increase in the presence of EVALSH, indicating a decrease in the pseudoplastic nature of the compatibilized blends. The reactive compatibilization of NBR/EVA blends with EVALSH was also confirmed by the decrease of damping values and an increase of glass transition temperature, in dynamic mechanical analysis. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2335–2344, 2002     

Dynamic–mechanical properties of modified poly(ethylene‐co‐vinyl acetate)

To study the relationship among relaxation peaks observed in dynamic mechanical experiments and the structure of poly(ethylene‐co‐vinyl acetate) (EVA), EVA copolymers with different substitution in the carbonyl group were synthesized. EVA was hydrolyzed to obtain poly (ethylene‐co‐vinyl alcohol) and was subsequently reacted with formic, hexanoic, and octanoic acids. The copolymers synthesized were characterized by infrared spectroscopy. Analysis of the DMA spectra of the copolymers showed that their relaxation behavior depends on the vinyl acetate concentration. The α‐ and β‐transitions were observed in EVA copolymers with 8 and 18 wt % of functional groups, and the relationship among relaxation process with the structure of polymer was investigated. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1371–1376, 2005     

Ethylene vinyl acetate and ethylene vinyl alcohol copolymer for thermal spray coating application

Ethylene vinyl acetate (EVA) copolymer with varying vinyl acetate (VAc) content, viz. 18%, 28% and 40% has been hydrolyzed using alcoholic NaOH solution. Fourier Transform Infrared Spectroscopy (FTIR) analyses of hydrolyzed polymer showed the presence of both OH group and acetate group indicating that the EVA has been partially hydrolyzed. Differential Scanning Calorimeter (DSC) and Thermo Gravimetric Analyzer (TGA) of EVA and hydrolyzed EVA showed large difference in melting and decomposition temperature, respectively. Hydrolyzed EVA showed higher tensile strength and elongation at break compared to corresponding EVA. Blends of different grades of EVA and ethylene vinyl alcohol (EVAl) with low density polyethylene (LDPE) were applied on grit blasted mild steel surface by flame spray technique. FTIR analysis of blends before and after coating showed no degradation during flame spray. Measurement of adhesion strength of these coating showed that adhesion strength increased on hydrolysis of EVA.     

Characterization of eva-based adhesives containing different amounts of rosin ester or polyterpene tackifier

Different amounts (50-170 php--parts per hundred parts of EVA, 33-63 wt%) of two tackifiers (hydrogenated rosin ester, polyterpene resin) were added to an ethylene vinyl acetate (EVA) copolymer containing 28 wt% vinyl acetate. The EVA and the tackifier were characterized using infrared (IR) spectroscopy, DSC measurements, and stress-controlled plate-plate rheology. The properties and compatibility of the EVA-tackifier mixtures were studied using DSC, DMTA, and stress-controlled plate-plate rheology. Immediate adhesion was measured as a quantification of tack, and the T-peel strength of roughened styrene-butadiene rubber/EVA-tackifier adhesive joints was also obtained. The increase in the amount of tackifier noticeably changed the crystallinity of polyethylene blocks in the EVA, and the temperature at the cross-over between the curves of the storage and loss moduli as a function of the temperature was displaced to a lower value. Whereas the hydrogenated rosin ester was compatible with the amorphous ethylene vinyl acetate copolymer regions of the EVA (Tg value increased) reducing its crystallinity, the polyterpene resin was compatible with the polyethylene blocks of the EVA (T g value was not modified), increasing its crystallinity. Immediate adhesion of the EVA-tackifier mixtures was improved by adding both hydrogenated rosin ester and polyterpene tackifiers. On the other hand, there was an optimum tackifier content at which the maximum T-peel strength value was obtained.     

乙烯—醋酸乙烯酯共聚物的化学接枝改性

综述了乙烯－醋酸乙烯酯共聚物的化学接枝方法,重点探讨了乙烯－醋酸乙烯酯与马来酸酐的接枝原因,并对接枝物的表征及应用加以论述。