Effect of rubber content on mechanical properties and heat shrinkage of ethylene vinyl acetate copolymer blended with epoxidized natural rubber

Ethylene vinyl acetate (EVA, 18 mol % vinyl acetate) and epoxidized natural rubber (ENR, 50 mol % epoxidation) were blended in an internal mixer and compared to EVA. Dicumyl peroxide (DCP) was used as a curing agent. The blends consisted of 10–50 wt % of ENR and were compared with crosslinked EVA in terms of heat shrinkage, mechanical properties, and degree of crystallinity. It is found that the blends showed a decrease in mechanical properties with increasing ENR content because DCP was not a good vulcanizing agent of ENR. The addition of ENR did not affect heat shrinkability of EVA. The maximum heat shrinkage obtained was 80% for EVA and the blends. ENR did not affect thermal properties of EVA investigated by the differential scanning calorimetry. The X‐ray diffractometry showed discrepancy in degree of crystallinity before and after specimen stretching and after heat shrinking. It is believed that ENR particles decreased molecular orientation of EVA resulting in a decrease in degree of crystallinity but the remained orientation was sufficient for heat shrinking. The blend showed better extrudability than EVA after increasing take‐up speed. Therefore, the extruded tube prepared from the blend provided higher heat shrinkage than EVA tube. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

EVA熔体流动速率对PLA/EVA共混物性能的影响

通过熔融共混法制备了聚乳酸（PLA）/乙烯-乙酸乙烯酯共聚物（EVA）共混物,采用SEM、DSC、旋转流变仪等研究了VA质量分数为28%,熔体流动速率（MFR）不同的EVA对PLA/EVA共混物性能的影响。结果表明,EVA熔体流动速率越小,其在PLA基体中分散越均匀,EVA颗粒粒径也越小。共混物的结晶度随EVA熔体流动速率的增大而增大,但PLA的玻璃化转变温度（Tg）基本不受EVA的影响。PLA/EVA共混物的复数黏度和储能模量均随EVA的熔体流动速率的增高而减小。力学性能测试结果表明,当EVA的质量分数为15%时,PLA的断裂伸长率明显升高,冲击强度约是纯PLA的2倍。     

Thermal,viscoelastic and adhesion properties of EVA (ethylene-co-vinyl acetate) hot melts containing polypropylene waxes of different nature

Wax determines the compatibility of tackifier and polymer in hot melt adhesives. Although the influence of the addition of microcrystalline and Fischer-Tropsch waxes on the properties of ethylene-co-vinyl acetate (EVA) hot melts has been studied, the addition of polypropylene wax has not been considered yet. In this study, different polypropylene waxes (polypropylene wax – PP, – maleic anhydride grafted polypropylene wax – PPMA – copolymer of polypropylene and 10.9?wt.% polyethylene wax – PP-E) were added to EVA hot melts and they were characterized by Brookfield viscosity, softening point measurement, differential scanning calorimetry, thermal gravimetric analysis, dynamic mechanical thermal analysis, plate–plate rheology, tack, and single-lap shear adhesion. The viscosities of EVA hot melts containing polypropylene waxes were relatively high, the highest viscosity corresponded to the formulation containing PP-E wax which also showed pseudoplasticity. The change in viscoelastic properties (i.e., from dominantly viscous to dominantly elastic) was produced at lower temperature in EVA hot melt containing PP-E wax, this adhesive exhibited the highest tack. On the other hand, the addition of acrylic PPMA wax increased the adhesion of EVA hot melt but lower tack was obtained. Finally, the PP-E wax was more compatible with EVA copolymer than the other polypropylene waxes.     

The effect of expanded graphite on the physical properties of conductive EVA/wax phase change blends for thermal energy storage

A study of the morphology, dynamic mechanical, impact, and tensile properties of ethylene vinyl acetate copolymer (EVA)/expanded graphite (EG) and EVA/wax/EG composites is presented. The composites were prepared by melt blending. The EVA/EG composites showed ductile behavior, while brittle behavior was observed in the presence of wax. A finer dispersion of EG was observed in the matrix when wax was present. The storage modulus of the EVA/wax/EG composite was higher than that of the EVA/EG composite, which is ascribed to a better interaction between the EVA and the wax‐covered EG that significantly reduced the EVA chain mobility. The composites showed a decrease in impact strength with increasing EG and wax contents. There was a significant difference in the elongation at break between the EVA/EG and EVA/wax/EG composites, and little change in Young's modulus of EVA in the presence of EG and with increasing EG content. However, Young's modulus of the EVA/wax blends increased in the presence of and with increasing EG content. In all the investigated samples containing EVA and wax, irrespective of the EG content, the stress at break decreased with an increase in wax content. POLYM. COMPOS., 37:3025–3032, 2016. © 2015 Society of Plastics Engineers     

Titanium Dioxide and Gamma Irradiation Induced Changes in the Structural,Morphology, and Mechanical Behavior of Ethylene Vinyl Acetate Copolymer

Some composites were prepared depending on ethylene vinyl acetate (EVA) copolymer with 18% VA content and titanium dioxide (TiO₂). These composites were prepared in the ratios of 100/0, 90/10, 80/20, 70/30, and 60/40 by melt mixing method. Gamma radiation at differing doses was applied on pure EVA and composites to investigate the impact on modification of composites. Gel percentage and the Charlesby‐Pinner equation were used to confirm crosslinking increases. X‐Ray diffraction measurement (XRD), scanning electron microscope (SEM), and mechanical testing were all used to investigate the varying effects of the different processes on the structure, morphology, and mechanical behavior of EVA. It was observed that the addition of TiO₂ and gamma irradiation both have a significant effect on the structure and, therefore, the composites' surface morphology. Notable changes of the lattice structure were revealed by the XRD results for both unirradiated and irradiated composites, which were also confirmed by examination of the samples' surface morphology. It was found that the presence and amount of TiO₂ along with the irradiation process has a significant influence upon the EVA's mechanical behavior. When compared with the pure EVA, the results demonstrated a significant enhancement in the mechanical parameters of both unirradiated and irradiated composites, except elongation at break. The mechanical results were in line with gel content analysis. The reliability of gamma radiation as an applied method for controlling long‐term properties is clearly demonstrated. J. VINYL ADDIT. TECHNOL., 26:224–235, 2020. © 2019 Society of Plastics Engineers     

Mechanical Modifications of Paraffin‐based Fuels and the Effects on Combustion Performance

In order to enhance the mechanical properties, 6 kinds of additives of stearic acid, polyethylene wax (A−C®6A), ethylene vinyl acetate copolymer (EVA), low density polyethylene (LDPE), polypropylene (PP) and high density polyethylene (HDPE) were blended in the paraffin fuel. Mechanical properties of paraffin‐based fuels were investigated by mixing 5 % in mass of different additives and increasing the mass percent of A−C®6A and LDPE. In addition, the combustion performance of the so modified paraffin‐based fuels were tested by a 2D‐radial burner at Nanjing University of Science and Technology. The effects of additives on regression rate were analyzed by thermal performance test (melting point and DSC) and viscosity measurement. Overall, all the additives can improve mechanical properties and the mechanical properties are enhanced by increasing mass% of additives. A−C®6A revealed the best for improving compressive strength (64.0 % increase by blending 5 mass %), LDPE revealed the best for improving tensile strength (105.3 % increase by blending 5 mass %). For combustion performance, the regression rates of paraffin‐based fuels blended with stearic acid increased owing to the decreased melting points while the regression rates of the other five formulations decreased due to the increased melted liquid viscosity. The relationship between regression rate and viscosity is a power function which is not affected by additives at high temperature, thereby it is convenient to predict the regression rate by measuring viscosity.     

EVA/纳米蒙脱土复合降凝剂对长庆含蜡原油的作用规律

利用纳米蒙脱土(MMT)特殊的带电性,使用含长烷基侧链的季铵盐对其插层改性得到有机改性蒙脱土(O-MMT)。采用熔融共混法制备O-MMT与EVA(聚乙烯醋酸乙烯酯)降凝剂的复合产物EVA/O-MMT,以国内典型含蜡长庆原油为研究对象,通过流变实验从宏观上评价EVA/O-MMT对长庆油的作用效果,并与EVA降凝剂进行对比,利用DSC和偏光显微镜考察加剂前后原油的结晶特性和蜡晶形貌的变化。结果表明:与纯EVA降凝剂相比较,EVA/O-MMT在最优加剂浓度50 mg·kg^-1下使长庆原油胶凝点、黏度、屈服值进一步降低(胶凝点降低2.5℃,5℃下的平均降黏率为25%,3℃下的屈服值下降55.5 %),从而大幅改善长庆原油的低温流变性。DSC放热特性表明O-MMT的引入可以提升EVA的初始结晶温度,拓宽EVA结晶放热区间,降低原油析蜡点。显微结果表明添加EVA/O-MMT的原油在低温下蜡晶结构更致密。     

Mechanical,Thermal and Electrical Properties of Ethylene Vinyl Acetate Irradiated by an Electron-Beam

The effects of electron beam irradiation of (ethylene vinyl acetate) EVA containing 18% vinyl acetate was studied. The EVA sample was then irradiated by using 3 MeV electron beam machine at doses ranging from 120 to 360 kGy in air at room temperature and analyzed for mechanical, thermal and electrical properties. It was revealed by DSC analysis that the crystallinity of the electron-beam radiated EVA decreased slightly as verified by a marginal reduction in the densities and heats of melting. Thermal degradation of EVA occurred through two steps as shown by the thermogravimetric curve with maximum rates of 350 and 450°C, respectively. The results obtained from both gel content and hot set tests showed that under the irradiation conditions employed, the EVA sample cross-linked by the electron beam irradiation, and the degree of cross-linking in the amorphous regions was dependent on the irradiation dose. A significant improvement in the tensile strength of the neat EVA samples was obtained upon electron-beam radiation up to 210 kGy with a concomitant decline in elongation of break. Various electrical properties of EVA such as surface and volume resistance, breakdown voltage and dielectric constant were studied as a function of radiation dose. It was revealed that the surface resistance and volume resistivity of the EVA reaches a maximum at a 190 kGy dose of radiation. No considerable change of breakdown voltage and dielectric constant was observed with increasing irradiation dose. These studies suggest that radiation-cured EVA is more thermally and mechanically stable than pure EVA. Similarly, the results from the electrical properties revealed that surface and volume resistance are higher than pure EVA.     

Experimental investigation on the abrasive wear behavior of nanoclay‐filled EVA/LDPE composites

The article presents the results of experimental investigation on three‐body abrasive wear behavior of nanoclay‐filled EVA/LDPE (NC‐EVA/LDPE) composites. NC‐EVA/LDPE composites with and without compatibilizer were prepared by Brabender Co‐Twin extruder (Make: CMEI, Model: 16CME, SPL) and poly(ethylene‐co‐glycidyl methacrylate) was used as the compatibilizer. The mechanical properties were evaluated using Universal testing machine. In three‐body wear tests, silica sand particles of size 200–250 μm were used as dry and loose abrasives. Three‐body abrasive wear studies were carried out using dry sand/rubber wheel abrasion test rig. The effect of abrading distance on the abrasive wear behavior of neat EVA, EVA/LDPE, and NC‐EVA/LDPE composites was reported. The results showed that the wear volume loss is increased with increase in abrading distance and the specific wear rate decreased with increase in abrading distance. However, the presence of nanoclay filler in EVA/LDPE composite showed a promising trend. Abrasive wear volume of the composites was correlated with mechanical properties such as hardness, tensile strength, and percentage elongation. However, higher weight percentage of LDPE in EVA increased the wear rate. The results indicate that NC‐EVA/LDPE with compatibilizer composite exhibits good abrasive wear resistance compared with NC‐EVA/LDPE without compatibilizer. Attempts to explain these differing trends are made in this work by analyzing the features observed on the worn surface samples by employing scanning electron microscopy (SEM). POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

EPDM-g-MAH对EPDM/CPE共混性能的影响

为改善三元乙丙橡胶(EPDM)和氯化聚乙烯(CPE)的相容性,提高共硫化反应程度,采用氢化钠(NaH)/马来酸酐(MAH)体系,在橡胶加工设备中对EPDM进行改性反应,得到了改性的三元乙丙橡胶(EPDM-g-MAH)。研究了加入EPDM-g-MAH后EPDM/CPE共混胶的硫化特性、动态力学性能、加工性能和微观相态结构。结果表明,EPDM-g-MAH的加入,使EPDM/CPE共混胶相容性得到明显改善,胶料硫化速度加快,力学性能及动态力学性能得到提高。     

Ethylene vinyl acetate/layered silicate nanocomposites prepared by a surfactant-free method: Enhanced flame retardant and mechanical properties

Exfoliated EVA/layered silicate nanocomposites were prepared by a masterbatch process using polymer-modified layered silicate instead of small molecule surfactant-modified clays. The nanocomposites exhibited improved mechanical properties and flame retardancy. Microscale flammability test showed that the heat release capacity (HRC) and total heat release (THR) were reduced by 21-24% and 16%, respectively. Radiant gasification studies revealed that the exfoliated EVA nanocomposites exhibited better improvements in flame retardant properties of EVA than did the corresponding intercalated nanocomposites. The peak mass loss rate of the exfoliated EVA nanocomposite containing about 5 wt% clay was reduced by 80% and the mass loss rate plot was spread over a much longer period of time. The mechanical and flammability tests revealed that the observed improvements in all the desirable properties were due to the presence of both the incorporated polymeric surfactant and the nanoclay.     

非流线型双绕柱旋涡流量计流体振动特性的研究

The characteristics of the dual bluff body vortex shedding is investigated, and the possibility to use dual bluff body combinations to strengthen the hydrodynamic vibration around the bluff body objects is explored. The numerical and experimental approaches were utilized to examine the time dependent flow field and the pressure oscillation around the bluff bodies. The numerical data were obtained by the advanced large eddy simulation model. The experiment was conducted on a laboratory scale of Karman vortex flowmeter with 40 mm diameter. It is revealed that the optimized dual bluff body combinations strengthened the hydrodynamic vibration. It was also found that the hydrodynamic vibration with 180° phase difference occurred at the axisymmetric points of circular pipe on the lateral faces of the equilateral triangle-section bluff bodies. Using the dual bluff body configuration and the differential sensing technique, a novel prototype of vortex flowmeter with excellent noise immunity and improved sensibil     

Effect of the addition of depolymerised ethylene vinyl acetate on the mechanical,thermal, chemical and shrinkage properties of cured unsaturated polyester resins

Unsaturated polyester resins (UPRs) are versatile compounds. However, their major drawback is the high shrinkage exhibited on curing. An attempt was made to reduce the shrinkage of UPRs without affecting other properties. In the present study a commonly used iso‐reactive UPR was modified by the addition of ethylene–vinyl acetate (EVA; subjected to controlled depolymerisation to obtain samples of various molecular weights), and was cured at room temperature. The peak exotherm temperature and gel time were both observed to decrease with an increase in EVA content. The composition incorporating 0.5% of depolymerised EVA1 (highest degree of branching) showed maximum improvement in tensile and flexural properties with the heat deflection temperature and impact properties remaining almost unaffected. A uniform dispersion for the UPR containing 0.5% of EVA1 was observed. Addition of EVA reduced the percentage shrinkage in the modified matrix. Incorporation of depolymerised EVA can be an attractive option for the reduction of shrinkage in UPRs. The advantage of using depolymerised EVA is that generated waste EVA can be depolymerised and reused for this application making it cost effective. Copyright © 2010 Society of Chemical Industry     

高孔隙率泡沫铜强化相变材料熔化特性

为了研究纯石蜡与泡沫铜/石蜡相变复合材料吸热熔化性能的不同,探究泡沫铜对石蜡熔化换热过程的影响,本文对纯石蜡和孔隙率为0.98的高孔隙率泡沫铜/石蜡复合材料的相变熔化过程进行了可视化实验研究,并数值模拟分析了纯石蜡及泡沫铜/石蜡复合材料熔化过程。结果表明：复合材料与纯石蜡的液相率变化出现交点,即临界液相率值,此时复合材料具有的液相占比与纯石蜡液相占比相同;泡沫铜的填充能明显改善纯石蜡传热系数低的问题,加快相变材料的整体熔化速率,当热通量为1200W/m2时,孔隙率为0.98的泡沫铜填充使纯石蜡完全熔化时间缩短了约12.5%,并使整体温度分布更均匀,改善热分层现象,且复合材料最大温差比纯石蜡最大温差低约27.5K。     

Regression Rate Studies of Paraffin Wax‐HTPB Hybrid Fuels Using Swirl Injectors

Studies on the regression rates of three compositions of paraffin wax‐HTPB hybrid fuel grains in a stream of gaseous oxygen using two different swirl injectors at a fixed injection pressure were carried out. It was found that the regression rate in the hybrid fuel increases with increasing paraffin wax percentage, which may be attributed to melt‐flow effects. The local regression rates, average regression rates, fuel mass consumption rates, and total mass fluxes for the hybrid fuels were found to be dependent on the swirl injector configuration. All three hybrid fuels were characterized by scanning electron microscopy (SEM). Furthermore, the thermal stability and thermal degradation behavior of the hybrid fuels were investigated by DTA/TGA techniques.     

Effect of different curing systems on heat shrinkability and mechanical properties of ethylene vinyl acetate/epoxidized natural rubber blends

Ethylene vinyl acetate (EVA)/epoxidized natural rubber (ENR) blends containing 10 and 30 wt % ENR were prepared by using an internal mixer. Five different types of curing systems were employed: dicumyl peroxide (DCP), sulfur (S), phenolic resin (Ph), DCP + S, and DCP + Ph. DCP could crosslink with both EVA and ENR while S and Ph were curing agents for ENR. The DCP system provided the lowest tensile properties and tear strength because of low crosslinking in ENR phase. Addition of sulfur or phenolic resin increased the mechanical properties due to a better vulcanization of the rubber phase. The mechanical properties of the blends decreased with increasing ENR content. The rubber particle size in the blends containing 30% ENR played a more important role in the mechanical properties than the blends containing 10% ENR. ENR particle size did not affect heat shrinkability of EVA and a well vulcanized rubber phase was not required for high heat shrinkage. Furthermore, heat shrinkage of the blends slightly changed as the ENR content increased for all curing systems. With regard to the mechanical properties and heat shrinkability, the most appropriate curing system was DCP + Ph and in the case the 10 wt % ENR content produced a more favorable blend. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Viscoelastic and adhesion properties of EVA/tackifier/wax ternary blend systems as hot-melt adhesives

Two types of wax were added to a ethylene vinyl acetate (EVA) copolymer/aromatic hydrocarbon resin (tackifier) blend in the molten state and the miscibility, viscoelastic and adhesion properties of ternary blends as hot-melt adhesives (HMAs) were investigated. Miscibility and viscoelastic properties were studied using differential scanning calorimetry (DSC), Brookfield viscometry and dynamic mechanical thermal analysis (DMTA), and their adhesion strength was determined in terms of single lap shear strength. DSC thermograms of both types of waxes showed their melting peaks in a similar region to that of EVA/tackfier blend. It was difficult to evaluate the miscibility of ternary blends using DSC because the melting peaks of the waxes overlapped with those of the EVA/tackifier blend, although the glass transition temperature (T _g) of the ternary blend systems slightly increased with increasing wax concentration. However, their storage modulus (E′) increased slightly and loss tangent (tan δ) showed different peaks when two types of wax were added to the EVA/tackifier blend. Therefore, the miscibility of EVA/tackifier blend altered with addition of waxes. In addition, their melt viscosity decreased with increasing wax concentration. Furthermore, the adhesion strength of the ternary blends decreased with increasing wax concentration, despite the increment of storage modulus. These results suggested that the ternary blends of EVA/tackifier/wax were heterogeneous.     

Properties of uncompatibilized and compatibilized poly(butylene terephthalate)–LLDPE blends

In this work, blends of poly(butylene terephthalate) (PBT) and linear low‐density polyethylene (LLDPE) were prepared. LLDPE was used as an impact modifier. Since the system was found to be incompatible, compatibilization was sought for by the addition of the following two types of functionalized polyethylene: ethylene vinylacetate copolymer (EVA) and maleic anhydride‐grafted EVA copolymer (EVA‐g‐MAH). The effects of the compatibilizers on the rheological and mechanical properties of the blends have been also quantitatively investigated. The impact strength of the PBT–LLDPE binary blends slightly increased at a lower concentration of LLDPE but increased remarkably above a concentration of 60 wt % of LLDPE. The morphology of the blends showed that the LLDPE particles had dispersed in the PBT matrix below 40 wt % of LLDPE, while, at 60 wt % of LLDPE, a co‐continuous morphology was obtained, which could explain the increase of the impact strength of the blend. Generally, the mechanical strength was decreased by adding LLDPE to PBT. Addition of EVA or EVA‐g‐MAH as a compatibilizer to PBT–LLDPE (70/30) blend considerably improved the impact strength of the blend without significantly sacrificing the tensile and the flexural strength. More improvement in those mechanical properties was observed in the case of the EVA‐g‐MAH system than for the EVA system. A larger viscosity increase was also observed in the case of the EVA‐g‐MAH than EVA. This may be due to interaction of the EVA‐g‐MAH with PBT. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 989–997, 1999     

回收高密度聚乙烯/废胶粉共混体系的力学性能研究

探讨了废胶粉（WRP）和回收高密度聚乙烯（RHDPE）共混改性时废胶粉的质量分数、相容剂的种类以及胶粉改性剂对RHDPE／WRP共混体系力学性能的影响。实验结果表明，当废胶粉的质量分数为20％时，体系的综合力学性能最佳。在RHDPE／WRP体系中分别添加EPDM、EVA、EAA时，EVA的增容效果最好，添加5％的EVA能使RHDPE／EVA／WRP体系的冲击强度增加55％。废胶粉经自制表面改性剂ACDI预处理后，其相应的RHDPE／EVA／MWRP体系的拉伸强度和弯曲模量分别增加35％和25％，而对共混物的其它性能影响不大。     

Use of pyrolyzed oil shale as filler in poly(ethylene‐co‐vinyl acetate) with different vinyl acetate contents

Pyrolyzed oil shale (POS) obtained from the pyrolysis of bituminous rock was used as filler in poly(ethylene‐co‐vinyl acetate) (EVA). The effects of the VA content of EVA and the particle size of POS on the mechanical properties were investigated. The composites were prepared in a rotor mixer at 180°C with a concentration of POS of up to 30 wt %. The stress–strain plots of the compression‐molded composites are similar to the EVA (18% VA content) behavior for low concentrations (1–5 wt %) of POS with a particle size lower than 270 mesh. It was observed that decreasing the POS particle size and increasing the VA content of EVA produced better compatibility between the polymer and filler. The mechanical properties, differential scanning calorimetry, and dynamic mechanical analysis also demonstrated the compatibility between EVA and POS under the increase of the VA content in the EVA. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1544–1555, 2002; DOI 10.1002/app.10494