Structure–shrinkability correlation in polymer blends of ethylene vinyl acetate and chlorosulfonated polyethylene

Heat shrinkability, which is a collective property of polymers, is being utilized in various applications, mainly in the field of encapsulation. Elastic memory is introduced into the system in the form of an elastomeric phase. Here the blends of ethylene vinyl acetate and chlorosulfonated rubber were studied with reference to their shrinkability. It was found that an increase in the elastomer content increased the shrinkage and an increase in cure time also increased the shrinkage. It was seen that high temperature (H‐T) stretched samples showed higher shrinkage than the low (room) temperature (R‐T) stretched one. Generally, the crystallinity of the H‐T stretched sample was higher than that of the low temperature stretched sample, which was again higher than that of the original unstretched sample; but for the low elastomer content blend the crystallinity of the R‐T stretched sample was found to be greater than the corresponding H‐T stretched one. The H‐T differential scanning calorimetry showed that an increase in the CSM content caused the stability toward oxygen to increase. The first decomposition temperatures were found to be higher and the second decomposition temperatures appeared to be lower for the H‐T shrunk sample than the corresponding unstretched sample. The rate of degradation appeared to be enhanced initially, then after 50% decomposition the rate started going down compared to the usual unstretched sample. From SEM it was seen that the H‐T stretched sample was more elongated than the R‐T stretched one. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 707–715, 2000     

Effects of compatibilizer on the layered silicate/ethylene vinyl acetate nanocomposite

Dispersion behavior of monmorillonite (MMT) is investigated in ethylene vinyl acetate (EVA)/MMT nanocomposite with various vinyl acetate content. Maleic anhydride (MAH) grafted polyethylenes with various MAH contents are used as a compatibilizer to enhance the dispersion of MMT. DMA and XRD studies indicate that an intercalated/exfoliated structure is obtained and vinyl acetate content and the concentration of PEMA play a critical role in EVA/MMT nanocomposite. Higher vinyl acetate content and concentration of grafted maleic anhydride result in better dispersion of MMT. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1057–1061, 2004     

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。     

改性剂和增容剂在EPDM/蒙脱土纳米复合材料中的作用

采用熔融插层和不同链长的改性荆改性蒙脱土的方法制备了三元乙丙橡胶(EPDM)／蒙脱土(MMT)纳米复合材料。X-射线衍射(XRD)和透射电镜(TEM)的测试结果表明：采用分子中亚甲基的数量小于16的改性剂改性MMT获得的有机蒙脱土与EPDM复合所得到的复合材料为传统型复合材料。而采用分子中亚甲基的数量大于16的改性剂改性MMT获得的有机蒙脱土与EPDM复合所得到的纳米复合材料为插层型。同时，笔者还探讨了EPDM接枝马来酸酐增容剂时复合材料形态的影响以及获得剥离型纳米复合材料的增容剂中马来酸酐的临界接枝率和增容剂最佳含量。此外，时该纳米复合材料的物理机械性能进行了评价。     

Thermal and mechanical properties of uncrosslinked and chemically crosslinked polyethylene/ethylene vinyl acetate copolymer blends

Uncrosslinked and chemically crosslinked binary blends of low‐ and high‐density polyethylene (PE), with ethylene vinyl acetate copolymer (EVA), were prepared by a melt‐mixing process using 0–3 wt % tert‐butyl cumyl peroxide (BCUP). The uncrosslinked blends revealed two distinct unchanged melting peaks corresponding to the individual components of the blends, but with a reduced overall degree of crystallinity. The crosslinking further reduced crystallinity, but enhanced compatibility between EVA and polyethylene, with LDPE being more compatible than HDPE. Blended with 20 wt % EVA, the EVA melting peak was almost disappeared after the addition of BCUP, and only the corresponding PE melting point was observed at a lowered temperature. But blended with 40% EVA, two peaks still existed with a slight shift toward lower temperatures. Changes of mechanical properties with blending ratio, crosslinking, and temperature had been dominated by the extent of crystallinity, crosslinking degree, and morphology of the blend. A good correlation was observed between elongation‐at‐break and morphological properties. The blends with higher level of compatibility showed less deviation from the additive rule of mixtures. The deviation became more pronounced for HDPE/EVA blends in the phase inversion region, while an opposite trend was observed for LDPE/EVA blends with co‐continuous morphology. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3261–3270, 2007     

Study on the morphology and properties of metallocene polyethylene and ethylene/vinyl acetate blends

Two commercial polymer materials, metallocene linear low density polyethylene (m‐LLDPE) and ethylene/vinyl acetate copolymer (EVA) have been used to form binary blends of various compositions. The mechanical properties, morphology, rheological behavior, dynamic mechanical properties, and crystallization of m‐LLDPE/EVA blends were investigated. It was found that with the addition of EVA, the fluidity and processability of m‐LLDPE were significantly improved, and the introduction of polar groups in this system showed no significant changes in mechanical properties at lower EVA content. As verified by morphology observation and differential scanning calorimetry analysis, miscible blends were formed within certain weight ratios. Dynamic mechanical property studies showed that flexibility of the blends was enhanced in comparion with pure m‐LLDPE, where the peak value of loss modulus shifted to lower temperature and its intensity was enhanced as EVA content increased, indicating the existence of more amorphous regions in the blends. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 905–910, 2004     

尼龙66/乙烯-醋酸乙烯酯共聚物接枝马来酸酐共混体系的研究(Ⅰ)乙烯-醋酸乙烯酯共聚物熔融接枝马来酸酐的制备与表征

以马来酸酐为单体、过氧化物为引发剂，采用熔融挤出法制备了乙烯-醋酸乙烯酯共聚物接枝马来酸酐(EVA-g-MAH)。重点讨论了不同型号的EVA、过氧化物引发剂品种及用量、单体MAH用量和加工工艺条件等因素时接枝反应的影响。通过化学滴定法和傅立叶红外光谱法(FTlR)证实部分马来酸酐确实以化学键连接到EVA分子链上。与聚乙烯(PE)、聚丙烯(PP)相比，EVA中由于含有醋酸乙烯(VA)基团，极性较大，与MAH的相客性较好，因而在相同的条件下接枝效率也更大；而且VA含量越大，越有利于接枝反应。比较不同的过氧化物引发剂BPO和DCP。发现DCP的引发效果更好。实验结果还表明，在EVA进行接枝反应的同时存在着交联反应，引发剂DCP的用量不宜过高，为得到接枝率适中，交联度很小的接枝产物，还要选择合适的MAH与DCP的用量。     

Electrical,physicomechanical, and X‐ray studies on ethylene‐vinyl acetate copolymer/polyaniline blends

The conductive blend consisting of ethylene‐vinyl acetate (EVA) and a polyaniline/p‐toluene sulfonic acid (PAn/TSA) complex were prepared by a thermal doping process using a Brabender plasticorder at 150°C. The conductivity, dielectric constant, dissipation factor, mechanical behavior, and structural aspects of these blends were investigated. A higher percentage of the PAn/TSA complex in the EVA matrix resulted in an increase in the electrical properties and a decrease in the mechanical properties like the tensile strength and percentage of elongation. These results were compared with the microcrystalline parameters of the blend obtained from X‐ray profile analysis. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1730–1735, 2002     

Preparation and characterization of ceria nanoparticles supported on poly(4‐vinyl pyridine‐co‐divinyl benzene)

Formation of ceria nanoparticles in 2% divinyl benzene (dvb) crosslinked 4‐vinyl pyridine (4vp) polymer [poly(4vp‐co‐dvb)] microspheres was investigated. The polymer was prepared by free radical suspension polymerization method. Poly(4vp‐co‐dvb)/ceria nanocomposites were prepared by reacting CeCl₃·7H₂O and NaOH in the presence of poly(4vp‐co‐dvb) at room temperature in aqueous media. The mole ratio of the metal to polymer was varied from 2.5 to 10% with an increment of 2.5. The polymer and nanocomposities were characterized by various spectrochemical methods. The coordination of nitrogen atoms of the polymer with Ce(IV) of ceria (CeO₂) has been confirmed from X‐ray photoelectron spectroscopy (XPS). The method has yielded ceria nanoparticles in an average size of 15 nm according to transmission electron microscopy. Differential scanning calorimetry, thermogravimetric analysis, X‐ray diffractometry and XPS analysis with respect to mole percentage of ceria in the composite are discussed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3439–3445, 2006     

PET／POE-g-MAH的性能研究

利用熔融法，采用马来酸酐接枝乙烯-辛烯共聚弹性体(POE-g-MAH)增韧聚对苯二甲酸乙二醇酯(PET)，研究了热处理对PFT／POE-g-MAH共混体系增韧效果的影响。结合共混材料的室温缺口冲击断面SEM照片，淬断刻蚀照片和宏观力学性能，分析了共混体系发生脆韧转变对应的微观形貌特征。结果表明POE-g-MAH与PET具有良好的相容性，热处理不但可以使PET／POE-g-MAH共混体系的拉伸强度增大，而且可以显著提高其冲击强度。     

双向可逆形状记忆乙烯⁃醋酸乙烯酯共聚物的制备和性能研究

以乙烯⁃醋酸乙烯酯共聚物（EVA）为原料,过氧化2⁃乙基己基叔丁酯（TBPE）为交联剂,合成了交联EVA双向形状记忆聚合物（SMP）,并且考察了TBPE含量对于交联EVA性能的影响。结果表明,交联EVA的T_m和T_c随着TBPE含量的上升呈现下降的趋势,可以通过交联剂比例调节材料的驱动温度;交联EVA的形状固定率会随着TBPE含量的增加呈现下降趋势,最低达到88.83 %,而样品的形状恢复率均超过99 %,并且都具有单向和双向形状记忆功能;交联EVA也具有双向记忆性能,R_a,_2W随着TBEC的含量增大而减小,R_r,_2W则相反;因此,通过改变交联剂EVA的量,对于双向交联EVA的性能有较大影响。     

Study of heat shrinkability of crosslinked low‐density polyethylene/poly(ethylene vinyl acetate) blends

In this study, the heat‐shrinkage property in polymer was induced by first compounding low‐density polyethylene/poly(ethylene vinyl acetate) (LDPE/EVA) blends with various amounts of peroxide in a twin‐screw extruder at about 130°C. The resulting granules were molded to shape and chemically crosslinked by compression molding. A process of heating–stretching–cooling was then performed on the samples while on a tensile machine. Shrinkability and effective parameters were also investigated using thermal mechanical analysis. The results showed that the gel fraction was higher for the sample of higher EVA content with the same amount of dicumyl peroxide (DCP). A decrease in the melting point and heat of fusion (ΔH_f), as determined from DSC, was observed with an increase in the DCP content. Studies on the heat shrinkability of the samples showed that samples stretched above the melting point had a higher shrinkage temperature than those stretched around the crystal transition temperature. The results showed that by increasing the peroxide content, the shrinkage temperature was decreased. These could be attributed to the formation of new spherulites as well as changes in the amount and the size of crystals. Furthermore, in samples elongated at 120°C (above the melting point), the rate of stretching had no effect on the shrinkage temperature. The results showed that the extent of strain had no effect on the temperature of shrinkage, but rather on the ultimate shrinkage value. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1389–1395, 2004     

Preparation and rheological characterization of intercalated polystyrene/organophilic montmorillonite nanocomposite

Polystyrene (PS)/organophilic montmorillonite (OMMT) clay nanocomposites were prepared by a solvent casting method using chloroform as a cosolvent. Intercalation of the OMMT in the PS matrix was achieved as revealed by X‐ray diffraction. The IR spectra of the products indicated that the OMMT is homogeneously dispersed in the PS matrix. A thermogravimetric analysis (TGA) showed that the onset temperature increases linearly with the clay content. The glass‐transition temperature of the PS, examined using differential scanning calorimetry, had a trend similar to that from the TGA. The rheological properties of the PS/OMMT nanocomposites were also investigated via a rotational rheometer with a parallel plate geometry, and they exhibited sharper shear thinning and increased storage and loss modulus with clay content. Furthermore, the shear viscosity obtained from the steady shear experiment was well correlated with the complex viscosity obtained from the oscillatory experiment via the Cox and Merz relation. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2106–2112, 2003     

X‐ray diffraction studies and phase volume determinations in poly(ethylene glycol)–montmorillonite nanocomposites

Poly(ethylene glycol)–montmorillonite nanocomposites were prepared by both solution and melt intercalation methods with a range of polymer molecular weights and at a range of polymer loadings. Particular attention was given to the reliability of low‐angle X‐ray diffraction results for basal plane spacing and a sound correlation between three diffractometers was obtained (±0.005 nm). Expansion of the basal plane spacing from 1.23 nm to 1.82 nm by solution intercalation was independent of polymer molecular weight in the range 300–20 000. Furthermore, the clay expansion was independent of the method of intercalation; melt intercalation also gave d₀₀₁ = 1.82 nm irrespective of polymer molecular weight. The maximum amount of polymer intercalated by clay and the maximum loading of clay that polymer can sustain were also studied for the determination of nanocomposite formulations. The confined polymer exerts a reduced effective density (670 kg m^?3) in the galleries. Copyright © 2005 Society of Chemical Industry     

Preparation and properties of poly(vinyl alcohol)-clay nanocomposite materials

A series of polymer-clay nanocomposite (PCN) materials that consist of poly(vinyl alcohol) (PVA) and layered montmorillonite (MMT) clay are prepared by effectively dispersing the inorganic nanolayers of MMT clay in organic PVA matrix via an in situ free radical polymerization with AIBN as initiator. Organic vinyl acetate monomers are first intercalated into the interlayer regions of organophilic clay hosts and followed by a one-step free radical polymerization. The prepared poly(vinyl acetate)-clay (PVAc-clay) solution are then saponified via direct-hydrolysis with NaOH solution to form PVA-clay nanocomposite materials. The as-synthesized PCN materials are typically characterized by Fourier-Transformation infrared (FTIR) spectroscopy, wide-angle X-ray diffraction and transmission electron microscopy.The molecular weights of poly(vinyl alcohol) (PVA) extracted from polymer-clay nanocomposite (PCN) materials and bulk PVA are determined by gel permeation chromatography (GPC) analysis with THF as eluant. The viscosity property of PCN materials with different feeding amount of MMT clay is studied by an ubbelohode capillary viscometer. The morphological image of as-synthesized materials is studied by scanning electron microscopy (SEM) and optical polarizing microscope (OPM). Effects of the material composition on the thermal stability, mechanical strength, optical clarity of PVA along with a series of PCN materials, in the form of fine powder and free-standing film, are also studied by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analyzer (DMA) and UV-visible transmission spectra, respectively.     

Poly(ethylene‐co‐vinyl acetate) blends with phenoxy

EVA was blended with phenoxy over the whole range of composition using a twin‐screw Brabender. Two‐phase separation caused by EVA crystallization was observed in the EVA‐rich blends and the dispersed domain of EVA was not clearly shown in the phenoxy‐rich blends. Differential scanning calorimetry (DSC) showed that the glass transition temperature (T_g) of EVA was increased by 5–10°C in the EVA‐rich blends but the T_g of phenoxy was superposed over the melting behavior of EVA. X‐ray diffraction measurement indicated that EVA crystallization was restricted in the phenoxy‐rich blends and the EVA crystal structure was influenced by incorporation of phenoxy into the EVA‐rich blends. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 227–236, 1999     

Effects of silicon additive as synergists of Mg(OH)2 on the flammability of ethylene vinyl acetate copolymer

The present work dealt with the effects of nine kinds of silicon additives on flame retardancy of ethylene‐vinyl acetate copolymer (EVA)/magnesium hydroxide [Mg(OH)₂] composites, as well as mechanical properties. The limiting oxygen index (LOI) test, horizontal fire test, vertical fire test, and cone calorimeter test were employed to evaluate flame retardancy of the composites. It was found that different silicon additives had different synergistic effects with Mg(OH)₂ on flame retardancy of the EVA matrix and exerted different influences on mechanical properties of the composites. The incorporation of organic montmorillonite (MMT) clay or silicone rubber not only made the composite reach FH‐1 rating in the horizontal fire test and FV‐1 rating in the vertical fire test, respectively, but also dramatically reduced the peak rate of heat release (Peak RHR) and increased the fire performance index (FPI) and ignition time (IT). The composites filled with precipitated SiO₂ exhibited the longest IT, the highest FPI, and FV‐1 rating. However, only the composites filled with silicone rubber could attain a balance between mechanical properties and flame retardancy. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

The effect of isopropanol addition on enhancement of transdermal controlled release of ibuprofen from ethylene vinyl acetate copolymer membranes

This work reports the study of the addition of isopropanol on controlled release of ibuprofen from ethylene vinyl acetate (EVAc) copolymer membranes. An EVAc solution in cyclohexane (4% w/v) containing triethyl citrate (7% w/v) as plasticizer was mixed with ibuprofen at three different concentrations of 4, 6, and 8%. Isopropanol was mixed with each of the previous mixtures to form solutions of 1, 3, and 5% isopropanol concentrations. Samples were solvent cast on glass petri‐dishes to form membranes. Home‐made diffusion cells were used for in vitro study. These cells were composed of two compartments, donor (exposed to ambient conditions), and receptor (including buffer solution maintained at 37°C). Each cell was equipped with a sampling port and water in and out system. An ultraviolet spectrometer at 222 nm was used to measure release rates of obtained membranes. The diffusion mechanism for drug release was examined by zero‐order, first‐order, Higuchi and Korsmeyer‐Peppas theories to confirm the obtained membranes follow the matrix‐type system. By increasing the drug concentration from 4 to 8%, drug release (cumulative amount) was improved from 20 (47.5%) to 30 (36%) μg/cm² after 24 h. Addition of 5% isopropanol to the above samples (4 and 8% loading) further increased drug release to 24 and 43 μg/cm². Results were in good agreement with the Korsmeyer‐Peppas theory for samples with 4 (% w/w) of ibuprofen. The highest percentage of drug release after 24 h was 59% for the sample with 4% drug loading compared to 50% for the sample with 8% drug loading, both with 5% isopropanol. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

乙烯-醋酸乙烯-氯乙烯共聚树脂合成试验研究

介绍了在10L聚合釜中合成乙烯-醋酸乙烯-氯乙烯(EVA-g-VC)共聚树脂的试验情况。分别研究了EVA种类及用量、EVA的溶胀方法、助剂对聚合过程和树脂颗粒性能的影响规律,制得的EVA-g-VC共聚树脂的加工性能基本达到了国外同类产品水平。