热塑性聚氨酯弹性体与乙华平橡胶共混物的性能

将聚酯型和聚醚型聚氨酯弹性体(TPU385E,TPU8685)分别与不同乙酸乙烯酯含量的乙华平橡胶(EVM400,EVM700)进行共混,考察了原料种类、共混比对共混物力学性能和耐磨性的影响。结果表明,随着TPU用量的增加,EVM/TPU共混物的拉伸强度、邵尔A硬度、100%定伸应力和300%定伸应力均提高,扯断伸长率下降;随着EVM用量的增加,EVM/TPU共混物的拉伸强度、邵尔A硬度、100%定伸应力和300%定伸应力均降低,扯断伸长率增大;随着TPU用量的增加,EVM/TPU共混物的耐磨性提高;TPU8685/EVM400共混物具有最大的拉伸强度,TPU385E/EVM700共混物具有最大的扯断伸长率,TPU8685/EVM700共混物具有最好的耐磨性;当2种TPU与EVM400质量比都为50/50时,TPU385E/EVM400的耐磨性最差。     

我国乙烯-乙酸乙烯酯树脂的进出口分析

根据海关数据,从进出口数量和金额,进出口国家或地区,进出口省市区以及进出口贸易方式等方面分析了 2020年我国乙烯-乙酸乙烯酯(EVA)树脂的进出口情况.     

乙酸-乙酸乙烯酯橡胶/聚乳酸共混体系的发泡及阻尼性能

以乙烯-乙酸乙烯酯橡胶(EVM)/聚乳酸(PLA)共混物为基体材料,过氧化二异丙苯(DCP)为硫化剂、偶氮二甲酰胺(AC)为发泡剂,经模压发泡制备橡塑共混发泡材料,用扫描电子显微镜观察材料的泡孔结构及泡孔尺寸分布,采用动态黏弹谱仪对发泡材料的阻尼性能进行研究,考察了AC和DCP用量、发泡时间及白炭黑用量对EVM/PLA发泡材料泡孔结构及阻尼性能的影响。结果表明,随着AC用量的增加,材料的泡孔数目增多但孔径相差不大,阻尼性能也无明显变化,在AC用量为4份时材料的阻尼性能较好;随着DCP用量的增加,材料的泡孔尺寸略有减小,阻尼性能变化不大,DCP用量为5份时材料的阻尼性能较好;随着发泡时间的延长,泡孔尺寸逐渐减小,阻尼性能逐渐提高,发泡时间为5 min时,泡孔孔径与损耗因子均出现突变;填料用量增加,泡孔孔径减小,发泡材料整体损耗因子上升。     

Thermogravimetric kinetic model of the pyrolysis and combustion of an ethylene-vinyl acetate copolymer refuse

A kinetic study of the pyrolysis as well as the combustion of EVA copolymer refuse originating from the footwear industry was carried out by thermogravimetric analysis. Different runs were performed at heating rates between 5-20 °C min⁻¹ and atmospheres with different percentages of oxygen: 0, 10 and 20% (v/v).Pyrolysis and combustion processes can be simulated by two series reactions. The results obtained indicate that the second reaction begins when the first one is almost finished which implies that a good correlation is also obtained by simulation of the thermal decomposition of two independent fractions.     

Thermal and physicomechanical properties of ethylene-vinyl acetate copolymer and layered double hydroxide composites

A series of ethylene-vinyl acetate (EVA) copolymer films have been prepared with different compositions viz. 2, 4, 6, and 8 wt % layered double hydroxide (LDH) nanoparticles by solution intercalation method. These solution-casted EVA/LDH nanocomposite films were dried and characterized by differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy. EVA/LDH films were further tested for tensile strength, density, moisture content, solubility resistance, flammability, and electrical properties. The DSC and FTIR analysis indicate strong interactions between the LDH layers and vinyl acetate groups in EVA. Further, EVA nanocomposite films show enhanced tensile strength, limiting oxygen index (LOI), and flammability rating for the addition of LDH without sacrificing the electrical properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

乙烯-乙酸乙烯酯共聚物Levapren 800硫化胶溶度参数的测定及应用

采用溶胀实验及计算机HSPiP软件对牌号为Levapren 800的乙烯-乙酸乙烯酯硫化胶的溶度参数进行了研究。结果表明,单一溶剂与混合溶剂都可用于Levapren 800硫化胶溶度参数的测定,用溶胀法测得其一维溶度参数(δt)为18.90~19.25(J/cm3)1/2。通过HSPiP软件测得Levapren 800硫化胶的δt为19.97(J/cm3)1/2;三维溶度参数的色散力、极性力和氢键力溶度参数分别为18.20,5.50,6.10(J/cm3)1/2。利用三维溶度参数可以预测Levapren 800硫化胶在标准实验油中的溶胀行为;相对能量差对预测聚合物在溶剂中的溶胀性能方面具有一定的应用价值。     

On the processability of metallocene-catalysed polyethylene: effects of blending with ethylene-vinyl acetate copolymer

The rheological properties of metallocene-catalysed linear polyethylenes and those of blends prepared with ethylene-vinyl acetate copolymers were evaluated. The pure polyethylenes showed characteristic features of linear polymers in the melt state, but poor processability, as would be expected for materials of narrow molecular weight distribution. The characteristic sharkskin and slip-stick regimes appear at around 0.16 and 0.35 MPa, respectively, during extrusion. Blending polyethylene with ethylene/vinyl acetate copolymers gave rise to smooth extrusion for a characteristic blend composition. The linear viscoelastic response of the blends revealed the behaviour of heterogeneous emulsion-like polymer systems. Through the application of several rheological criteria, we were able to locate the phase inversion concentration of the system. This concentration was found to closely correspond to that at which distortion regimes disappear during extrusion.     

乙烯-醋酸乙烯共聚物对天然橡胶/丁腈橡胶并用胶性能的影响

研究了EVA(乙烯-醋酸乙烯共聚物)对天然橡胶(NR)/丁腈橡胶(NBR)并用胶硫化特性、力学性能、阻尼性能、压缩生热的影响。结果表明:随着EVA含量的增多,NR/NBR并用胶的硫化速度先升后降;拉伸强度降低,撕裂强度则先增加后下降,硬度增加,回弹性降低;NR/NBR并用胶在拉伸/压缩-恢复过程中的HED和HLE均先减少后增大; DMA谱图中NR与NBR相损耗峰均移向低温,有效阻尼温域拓宽;压缩永久变形和疲劳温升增加。     

乙烯-乙酸乙烯酯共聚物/聚乙烯热塑性硫化胶的形态结构及流变性能

使用双转子密炼技术制备了具有双连续相结构的乙烯-乙酸乙烯酯共聚物(EVA)/聚乙烯(PE)的热塑性聚烯烃(EVA/PE-TPO)和热塑性硫化胶(EVA/PE-TPV)材料,并利用扫描电子显微镜、Han曲线和vGP曲线对二者的相形貌进行了分析和表征。动态流变行为的结果表明,在低频区,EVA含量对EVA/PE-TPO材料体系的储能模量(G′)和复数黏度的影响均大于EVA/PE-TPV体系;在高频区,组成相同的两种体系的G′相近。当两相的组成比例相同时,时温等效原理适用于210℃以下的EVA/PE-TPV体系。修正Palierne模型对双连续相结构EVA/PE-TPV材料的线性黏弹性的拟合程度不高。     

Incorporation of indolinospirooxazine on ethylene-vinyl acetate copolymer to produce a intelligently temperature-regulated nonwhite cool material

Cool materials that adjust cooling efficiency according to sunlight intensity are needed because people have different needs for cooling at different times. Several colors of commercial microencapsulated photochromic powder were melt blended with ethylene-vinyl acetate copolymer in a two-roll mill at 90 °C to prepare the photochromic films of corresponding colors. Pink photochromic films [the organic photochromic compound is indolinospirooxazine (NISO)] were selected to continue the following variable experiment due to its best performance in the indoor cooling test. The pink photochromic films change color as well as transmittance according to the intensity of sunlight, thereby achieving an intelligent cooling effect. A maximum decrease around 10 °C was observed in natural environment when the addition amount of pink photochromic powder reaches 2.0 phr under strong sunlight and all films did not show cooling effect under weak sunlight. This material can be covered on buildings to regulate the indoor temperature. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48887.     

Flame retardancy and thermal stability of ethylene-vinyl acetate copolymer nanocomposites with alumina trihydrate and montmorillonite

The development of fire retardant for wire and cable sheathing materials has oriented toward low smoke and halogen-free flame retardant technology to achieve better safety for electrical equipment and devices and to satisfy standards. However, many polymer flame resistance materials require a very high proportion of metal hydrate filler within the polymer matrix (60 wt%) to achieve a suitable level of flame resistance, which may lead to inflexibility, poor mechanical properties and problems during compounding and processing. In this study, the alumina trihydrate (ATH) was added to montmorillonite (MMT) as the halogen-free flame retardant of ethylene-vinyl acetate (EVA) copolymer, with various ratios of EVA/ATH/MMT. The prepared nanocomposites were characterized through various techniques of XRD, tensile test, DSC analysis, TGA, LOI evaluation, and FE-SEM to explore the effects of organic modified clay (OMMT) and the layer distance on the mechanical, thermal, and flame resistance properties. In the XRD examinations, the layer-distance of MMT increased from 1.27 to 1.96 nm when polymer was added to the octadecylamine modified MMT. The best tensile strength was obtained at 3 wt% MMT. In addition, the halogen-free flame resistance grade of EVA containing 3 wt% OMMT and 47 wt% ATH revealed the best elongation and fire resistance (LOI = 28). The tensile and flame resistance properties of the nanocomposites were also significantly improved.     

基于乙烯-乙酸乙烯共聚物/丁腈橡胶热塑性硫化橡胶超亲水材料的制备与性能

采用动态硫化法制备了基于乙烯–乙酸乙烯酯共聚物/丁腈橡胶的热塑性硫化橡胶（EVA/NBR TPV）,以不同型号金相砂纸为模板,通过模压法在其表面构建具有微纳米结构的表面,研究了橡塑质量比对EVA/NBR TPV粗糙表面超亲水行为的影响及EVA/NBR TPV超亲水表面的微观结构和超亲水性能,并初步探讨了EVA/NBR TPV表面的亲水机制。结果表明,当EVA/NBR TPV的橡塑质量比为20/80时,采用模板法且以耐水砂纸为模板制得的EVA/NBR TPV表面亲水性较好。其中,当橡塑质量比为20/80时,以NO 1000砂纸为模板,模压温度为165 ℃,经过预热10 min、热压3 min、冷压5 min后制得的EVA/NER TPV薄膜表面的亲水性最佳。     

Nanocomposites of ethylene-vinyl acetate copolymer (EVA) and organoclay prepared by twin-screw melt extrusion

Preparation of nanocomposites based on ethylene-vinyl acetate copolymer (EVA) and organoclay by melt intercalation is described in this paper. Effects of VA content, melt flow index (MFI) and maleation of EVA on melt intercalation were investigated by X-ray diffraction. The level of intercalation into the organoclay increases greatly as VA content increases from 6 to 12 wt%, but shows minimal change from 12 to 28 wt%. For 28 wt% VA content polymers with MFI from 3 to 150, interlayer expansion exhibited a maximum at MFI = 6. Exfoliated nanocomposites were not obtained for a range of unfunctionalized EVA's of different VA content and MFI. Use of maleated EVA (MEVA) had an obvious improvement on exfoliation of the silicate layers probably due to chemical interaction between the MEVA matrix and silicate layers. FTIR results showed that the MA functionality reacts during processing. Lower clay content favored formation of an exfoliated nanocomposite structure. Exfoliated nanocomposites from MEVA exhibited higher Young's modulus and tensile strength than either pure EVA or intercalated nanocomposites from non-maleated EVA. Polym. Compos. 25:535–542, 2004. © 2004 Society of Plastics Engineers.     

Influence of molten-state annealing on the phase structure and crystallization behaviour of high impact polypropylene copolymer

The phase structure evolution of high impact polypropylene copolymer (IPC) during molten-state annealing and its influence on crystallization behaviour were studied. An entirely different architecture of the IPC melt was observed after being annealed, and this architecture resulted in variations of the crystallization behaviour. In addition, it was found that the core-shell structure of the dispersed phase was completely destroyed and the sizes of the dispersed domains increased sharply after being annealed at 200 °C for 200 min. Through examination of the coarseness of the phase morphology using phase contrast microscopy (PCM), it was found that a co-continuous structure and an abnormal ‘sea-island’ structure generally appeared with an increase in annealing time. The original matrix PP component appeared as a dispersed phase, whereas the copolymer components formed a continuous ‘sea-island’ structure. This change is ascribed to the large tension induced by solidification at the phase interface and the great content difference between the components. When the temperature was reduced the structure reverted to its original form. With increasing annealing time, the spherulite profiles became more defined and the spherulite birefringence changed from vague to clear. Overall crystallization rates and nucleation densities decreased, but the spherulite radial growth rates remained almost constant, indicating that molten-state annealing mainly affects the nucleation ability of IPC, due to a coarsened microstructure and decreased interface area.     

撕裂模式下乙烯-乙酸乙烯酯共聚物/氯丁橡胶热塑性硫化胶的Mullins效应及其可逆回复

采用动态硫化法制备了乙烯-乙酸乙烯酯共聚物（EVA）/氯丁橡胶（CR）热塑性硫化胶（TPV）,对其微观形貌、撕裂强度、撕裂模式下的Mullins效应、热处理后的可逆回复行为及其机制进行了研究。结果表明,EVA/CR TPV橡塑质量比为30/70时其撕裂模式下的应变和撕裂强度较高,橡胶相与树脂相呈“海-岛”结构;撕裂模式下EVA/CR TPV的单轴循环测试中表现出明显的Mullins效应,增大应变时,其最大撕裂强度、瞬时残余应变、内耗值和阻尼因子均增加,但应力软化因子趋于下降;随着热处理温度的上升,Mullins效应的可逆回复效果获得改善,且温度为70℃时其可逆回复行为最好。     

Effect of vinyl acetate on aging mechanism of polyacrylate under UV light

Diversity of aging behaviors of polyacrylate and poly(vinyl acetate‐acrylate) with the ultraviolet light radiation was studied. The aging degree was evaluated and the mechanism dominated the behaviors was investigated by color aberration, the degree of cross‐linking, molecular weight and its distribution by gel permeation chromatography (GPC), ultraviolet absorption spectroscopy (UV–vis), and fourier transform infrared spectrometer (FTIR). These studies found that although photodegradation mechanism of poly(vinyl acetate‐acrylate) still preserves three main steps of the scission of main chain, formation of double bond and the generation of cross‐linking reaction, introducing structural units of vinyl acetate to polyacrylate cause the rules various. The structural units can aggravate the aging of polyacrylate, through increasing formation of double bonds and generating cross‐linking reaction. However, what is interesting is that the structural units can strikingly restrain main chain from scission. It is significant for modifying the photodegradation behaviors of polyacrylate coatings. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Rheology of molten blends of polyoxymethylene and ethylene-vinyl acetate copolymer and the microstructure of extrudates as a function of their melt viscosities

Blends of polyoxymethylene (POM) with a copolymer of ethylene and vinyl acetate (CEVAc) have been studied. The effect of viscosity ratio for melts of the components on the processes of fiber formation in extrudates and on the rheological properties of the molten blend has been tested. The viscosity ratio of the fiber-forming POM and the matrix varied in the range 0.35-27.7. POM ultrathin fibers of unlimited length can be formed in the CEVAc only at a viscosity ratio close to unity. For ratios much greater than unity, the extrudate is found to contain short fibers and a finely dispersed powder or no fibers at all. If the viscosity of the POM melt is lower than that of the matrix, films are formed in addition to fibers. The second factor that governs fiber formation is the extrusion shear stress. An optimum shear stress exists at which the amount of ultrathin fibers is a maximum.     

Durability of the flame retardance of ethylene-vinyl acetate copolymer cables: Comparing different flame retardants exposed to different weathering conditions

Scientific publications addressing the durability of the flame retardance of cables during their long-term application are rare and our understanding lacks. Three commercial flame retardants, aluminum hydroxide, aluminum diethyl phosphinate (AlPi-Et), and intumescent flame retardant based on ammonium polyphosphate, applied in ethylene-vinyl acetate copolymer (EVA) model cables, are investigated. Different artificial aging scenarios were applied: accelerated weathering (UV-irradiation/temperature/rain phases), humidity exposure (elevated temperature/humidity), and salt spray exposure. The deterioration of cables' surface and flame retardancy were monitored through imaging, color measurements, attenuated total reflectance Fourier transform infrared spectroscopy, and cone calorimeter investigations. Significant degradation of the materials' surface occurred. The flame retardant EVA cables are most sensitive to humidity exposure; the cable with AlPi-Et is the most sensitive to the artificial aging scenarios. Nevertheless, substantial flame retardance persisted after being subjected for 2000 h, which indicates that the equivalent influence of natural exposure is limited for several years, but less so for long-term use. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 47548.     

Effect of molecular structure on ethylene-vinyl alcohol copolymer thermal degradation and stability

To study the effect of molecular structure on ethylene-vinyl alcohol copolymer (EVOH) thermal stability during processing, EVOH samples with different molecular weights and comonomer distributions were prepared by solubility fractionation from two different commercial materials, and then, the structure features of samples were characterized by ¹H-NMR, viscometry, differential scanning calorimetry, and, especially, successive self-nucleation and annealing. Their thermal stabilities were further analyzed by isothermal oxygen treatment and thermogravimetry. Attenuated total internal reflectance Fourier transform infrared spectroscopy and UV were used to obverse the structural changes in samples (the formation of chromogenic groups: CO and  CC ). According to the results of isothermal oxygen treatment at 200°C, at the same ethylene content, low-molecular-weight samples have worse thermal stability, which were extremely easy to yellowing and form insoluble gel. To investigate the structure differences between the low-molecular-weight samples, it was found that long vinyl alcohol segments may not worsen the thermal stability in the conditions of the same ethylene content. But samples with a uniform distribution of ethylene segments and a certain length of ethylene segments will have better thermal stability, which makes it more difficult to form carbonyl even diketene conjugation structure.     

Effect of hot air aging on the properties of ethylene‐vinyl acetate copolymer and ethylene‐acrylic acid copolymer blends

The aim of this investigation is to evaluate the effect of hot air aging on properties of ethylene‐vinyl acetate copolymer (EVA, 14 wt % vinyl acetate units), ethylene‐acrylic acid copolymer (EAA, 8 wt % acrylic acid units), and their blends. Attenuated total reflection‐Fourier transform infrared spectroscopy, differential scanning calorimeter (DSC), wide angle X‐ray diffraction, and mechanical tests are employed to investigate the changes of copolymer blends' structures and properties. Increase of carbonyl index derived from ATR measurements with aging time suggests the incorporation of oxygen into the polymeric chain. By DSC measurements, the enthalpy at low temperature endothermic peak (T_m2) of EAA becomes less and disappears after 8 weeks aging, but enthalpy at T_m2 of EVA is not influenced by the hot air aging and remains stable despite of the aging time. For various proportions of EAA and EVA blends, enthalpy at T_m2 decreases as the EAA proportion increases when aging time is 8 weeks; after several weeks of hot air aging, the various blends appear a same new peak just over the aging temperature 70°C which is due to the completion of crystals which are not of thermodynamic equilibrium state. Mechanical tests show that increase of crystallinity and hot air aging deterioration both have influence on the hardness, tensile strength, and elongation at break. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009