醋酸乙烯酯-叔碳酸乙烯酯乳液共聚动力学研究

以十二烷基硫酸钠为乳化剂,聚乙烯醇为保护胶体,过硫酸钾为引发剂,进行醋酸乙烯酯-叔碳酸乙烯酯(VAc-VeoVa10)乳液共聚.研究了引发剂含量、乳化剂含量、单体配比和聚合温度等对VAc-VeoVa10乳液共聚速率的影响.结果表明:共聚体系的总表观活化能为106.55 kJ/mol,单体组成对共聚速率的影响不明显,Ⅱ阶段共聚合速率同引发剂浓度的0.658次方,乳化剂浓度的0.371次方成正比.     

Maximizing production rate and scrub resistance of vinyl acetate–VeoVa 10 latexes

Optimal strategies for the emulsion copolymerization of vinyl acetate and VeoVa 10 have been developed. These strategies are based on a hybrid mathematical model for the process that includes rigorous material and energy balances and empirical equations for uncertain terms. The strategies were implemented in a lab‐scale calorimetric reactor. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 475–485, 2000     

丙-叔-醋共聚乳液的研制与应用

通过使用非离子型乳化剂和阴离子型乳化剂组成的复合乳化剂和保护胶体,利用各反应物中丙烯酸酯,叔碳酸乙烯酯憎水性强、抗剪切强度好和较好的内增塑作用的特性,以丙烯酸酯、叔碳酸乙烯酯、醋酸乙烯酯为反应单体进行聚合,采取对混合单体先预乳化后滴加,控制反应过程的方式,制得丙-叔-醋多元共聚乳液,以其为基料,根据乳胶漆的生产需要,加入各种填料和助剂,制成乳胶漆,产品具有良好的耐水、耐酸碱和耐擦洗性,满足优质乳胶漆的应用性能要求。     

Effect of vinyl acetate plus vinylene carbonate and vinyl ethylene carbonate plus biphenyl as electrolyte additives on the electrochemical performance of Li-ion batteries

For application to Li-ion batteries, we studied the electrochemical behavior and thermal stability of the following two combinations of binary electrolyte additives in a triphenylphosphate (TPP)-containing ionic electrolyte: vinyl acetate (VA) plus vinylene carbonate (VC), and vinyl ethylene carbonate (VEC) plus biphenyl (BP). Mesocarbon microbeads (MCMB) and LiCoO₂ were used as the anode and cathode materials, respectively. Cyclic voltammetry (CV), differential scanning calorimetry (DSC), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM) were used for the analyses. These results confirmed the capability of the VEC + BP electrolyte additive to improve the cell performance and electrolyte thermal stability in TPP-containing solutions in Li-ion batteries.     

Semicontinuous emulsion polymerization of vinyl acetate: Effect of ethoxylation degree of nonionic emulsifiers

Poly(vinyl acetate) latices were prepared in the presence of an ammonium persulfate initiator, 10–50 mol of an ethoxylated nonylphenol nonionic emulsifier, and a poly(vinyl alcohol) colloid stabilizer by applying semicontinuous emulsion polymerization (delayed monomer and initiator addition process) in a laboratory scale similar to industrial practice. Two approaches were applied: the molar concentration of the nonionic emulsifier was kept constant and the weight ratios in the polymerization recipe varied or the weight ratios were kept constant. The effects of the change in the ethoxylation degree of the emulsifier to the final latex viscosity, average polymer molecular weight, polymer grafting degree, surface tension of the latex, and the surface free energy of the dried films were investigated. It was determined that the resultant latex viscosity decreases and the viscosity‐average polymer molecular weight increases with increase of the nonionic emulsifier ethoxylation degree. The increase of the ethoxylation degree does not seriously affect the surface tension of the resultant latex or the surface free energy of the dried poly(vinyl acetate) films. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 844–851, 2002     

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     

非保护胶体稳定醋叔丙乳液及其乳胶漆耐擦洗性能的研究

通过乳液聚合法,使用叔碳酸乙烯酯类及丙烯酸酯类单体对醋酸乙烯酯进行改性共聚,以改善醋酸乙烯酯聚合物的缺点。在聚合过程中不使用传统的保护胶体,而采用乳化剂稳定技术制备了一种小粒径的醋叔丙(醋酸乙烯酯/叔碳酸乙烯酯/丙烯酸酯)乳液,并研究了其用于内墙高PVC(颜料体积浓度)乳胶漆时单体组成、乳液粒径、功能单体等因素对耐擦洗性能的影响。结果表明成功地开发了一种小粒径非保护胶体稳定的醋叔丙乳液,可以满足高PVC经济环保内墙乳胶漆乳液高耐擦洗性能要求。     

Effect of intumescent compositions on flammable properties of ethylene vinyl acetate and polypropylene

An intumescent flame retardant (IFR) system was prepared by 2 ways. Firstly, bis(2,6,7‐trioxa‐1‐phosphabicyclo[2,2,2]octane‐1‐oxa‐4‐hydroxymethyl) phosphonate methyl (bis‐PM) was synthesized and characterized by ¹H nuclear magnetic resonance (NMR), ³¹P NMR, and Fourier transform infrared spectroscopies. This carbonization agent was mixed with melamine (ME), ammonium polyphosphate (APP), and pentaerythritol (PER) to constitute an IFR system. Secondly, an IFR system by reaction was prepared by reaction, and the presence of compositions in product was confirmed by ¹H NMR and Fourier transform infrared. Both of systems enhanced the flammable retardation of ethylene vinyl acetate (EVA) and polypropylene (PP). Flammability and thermal behaviors of IFR‐EVA and IFR‐PP were investigated by vertical burning test (UL‐94 V) and thermogravimetric analysis. Results indicated that the IFR systems performed excellent flame retardancy and antidripping ability for PP. At 30 wt% loading, the optimum flame retardant formulations that are bis‐PM/ME: 4/1, bis‐PM/ME/PER: 3/1/1, APP/ME/PER: 3/1/1, and bis‐PM/ME/PER/APP: 1.5/1.5/1/1 give UL‐94 V‐0 rating. However, V‐0 rating results were only obtained for EVA when systems contain bis‐PM/ME: 4/1 and bis‐PM/ME/PER: 3/1/1. The char yield from decomposition of the IFR‐EVA and IFR‐PP has effects on the flame retardancy and antidripping behaviors of EVA and PP.     

Emulsion copolymerization of vinyl acetate and 2‐ethyl hexyl acrylate using nonionic emulsifiers in loop reactor

Batch emulsion copolymerization of vinyl acetate and 2‐ethyl hexyl acrylate (VAc/2EHA = 90 : 10) was initiated by the thermal initiators ammonium persulfate and potassium persulfate at 70°C in the presence of nonylphenol ethoxylates with varying chain lengths and poly(vinyl alcohol). VAc–2EHA copolymer latexes were synthesized as two different series in a loop reactor. The first series was initiated by ammonium persulfate, and the second series was initiated by potassium persulfate. The influence of the counterions or initiators and chain lengths of a nonionic emulsifier on the properties of VAc–2EHA copolymer latexes were determined by measuring the viscosities, weight‐average molecular weights, number‐average molecular weights, molecular weight distribution, and surface tension of latexes to air. The results for the copolymer latexes indicated that some of their physicochemical properties increased with increasing chain length of the nonionic emulsifier, but some of them followed a different trend for the two initiators. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1380–1384, 2005     

Rheological study on the adhesion properties of the blends of ethylene vinyl acetate/terpene phenol adhesives

Measurements of the shear, tensile, peel, and creep strength of ethylene vinyl acetate (EVA)/CaCO₃/terpene phenol adhesive system at three different ratios [100/60/0 (EVA-O), 80/48/20 (EVA-20), and 60/36/40 (EVA-40) by weight, using wood and aluminum as adherends] were conducted. Over a wide range of temperatures and rates of deformation, adhesion shear, tensile, and peel strength results, as well as the creep response over a broad range of temperature and stresses, were found to yield a single master curve by means of the reduced-variable technique. It was observed that the peak of E′ representing Tg, shifted toward higher temperatures as the amount of terpene phenol in the blend was increased. The most obvious effect of increasing the tackifier resin was the shifting of the adhesion strength master curves to the direction of lower rates. The shift was associated with the rise in Tg as the blend ratio was increased. The influence of the tackifier resin in modifying the viscoelastic properties of the adhesive was further described in a comparison of the adhesion strength master curves with corresponding dynamic viscoelastic curves of the adhesive films. The master curves for the creep response of the adhesives showed that the stress-breaking time relationship shifts toward longer time for EVA-40 with high Tg. Thus, it was found that the strength of adhesion is due mainly to dynamic effects in the adhesive of a viscous nature in the same way to the cohesive strength of the viscoelastic materials. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 409–418, 1998     

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     

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     

Effect of irradiation on mechanical and structural properties of ethylene vinyl acetate copolymers hollow fibers

Effect of irradiation on mechanical and structural properties of ethylene vinyl acetate copolymers (EVA) hollow fibers was studied by the tests such as determination of gel content, density, tensile, FTIR, SEM, and DMA. These effects were discussed based on dose and irradiation environment. The results of gel content depicted that irradiated EVA in ambient conditions had tendency to chain scission while the crosslinking overcame in irradiated samples under nitrogen. Density insignificantly enhanced with irradiation dose. In tensile test, irradiation induced increase in tensile strength and decrease in elongation at break (especially in samples irradiated in nitrogen). Also, changing in layer orientation could be observed by SEM images. In addition, irradiation caused altering peak intensity in FTIR spectrum. DMA results demonstrated that irradiation broaden the elastic zone. Totally, irradiation enhances features especially in irradiated EVA18 in nitrogen. Since, according to stabilization of induced deformation and improvement of mechanical properties (that created by radiation), the irradiated samples can be used in different applications. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and characterization of ethylene vinyl acetate copolymer/montmorillonite nanocomposite

Ethylene vinyl acetate copolymer (EVA) and monmorillonite (MMT) nanocomposites have been investigated as a function of vinyl acetate content and molecular weight of EVA and types of substituted alkyl ammonium of MMT. It is found that vinyl acetate content and type of substituted alkyl ammonium are important factors for the intercalation behaviour of MMT in MMT/EVA nanocomposite. Maleic anhydride grafted high‐density polyethylene was used as a compatibilizer to improve the intercalation behaviour of MMT. X‐ray diffraction and transmission electron microscopy were used to characterize the intercalation/exfoliation behaviour, and mechanical properties were measured. © 2003 Society of Chemical Industry     

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     

Effect of flexibility of ethylene vinyl acetate and crystallization of polypropylene on the mechanical properties of i‐PP/EVA blends

Polymer blend technology has been widely used for the past several years for the modification or enhancement of mechanical properties of polymers to obtain an overall balance of properties over those of the constituents. Despite its interesting mechanical and thermal properties, the impact strength of polypropylene leaves wide scope for improvement. A series of blends of ethylene vinyl acetate (EVA) copolymer with an impact grade of isotactic polypropylene (i‐PP) were prepared by single screw extrusion at 0–0.32 volume fraction of the dispersed phase. The mechanical properties such as tensile behavior, elongation‐at‐break, and impact strength of these blends systems as well as crystallinity were evaluated. Crystallinity data have been used in greater depth to support the mechanical properties. Differential scanning calorimetry studies conducted to study the modification in crystallinity of the crystalline component, i‐PP, of the blend revealed that the rubber component of the blend enhanced the crystallinity of i‐PP phase by providing sites for nucleation. Tensile modulus and strength decreased while the impact strength and breaking elongation enhanced with blending elastomer concentration. The improved properties of these PP/EVA blends are encouraging for carrying out further work on this system (composites) and suggest potential high impact strength applications for PP. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

醋酸乙烯-乙烯共聚乳液的生产及市场前景

概述了醋酸乙烯－乙烯共聚乳液的合成工艺及市场前景。     

Cure characteristics,morphology, mechanical properties,and aging characteristics of silicone rubber/ethylene vinyl acetate blends

Silicone rubber/ethylene vinyl acetate (SR/EVA) rubber mixes with different ratios were prepared by using dicumyl peroxide (DCP) and benzoyl peroxide (BP) as curing agents. The vulcanization characteristics such as cure kinetics, activation energy, and cure rate of the blends were analyzed. The effects of blend ratio and curing agents on the mechanical properties such as stress–strain behavior, tensile strength, elongation at break, tear strength, relative volume loss, hardness, flex crack resistance, and density of the cured blends have been investigated. Almost all the mechanical properties have been found to be increased with increase in EVA content in the blends particularly in DCP‐cured systems. The increment in mechanical properties of the blends with higher EVA content has been explained in terms of the morphology of the blends, attested by scanning electron micrographs. Attempts have been made to compare the experimental results, from the evaluation of mechanical properties, with relevant theoretical models. The aging characteristics of the cured blends were also investigated and found that both the DCP‐ and BP‐cured blends have excellent water and thermal resistance. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1069–1082, 2006     

PVAc/VAE共混乳液与聚烯烃界面行为的研究

通过接触角的测量及表面和界面张力的计算 ,对PVAc/VAE共混乳液与聚烯烃的界面行为进行了研究 ,表明胶粘剂与被粘材料之间的界面张力是影响粘接强度的重要因素     

Surfactant concentration effects on the microemulsion polymerization of vinyl acetate

The polymerization of vinyl acetate in oil-in-water microemulsions stabilized with cetyltrimethylammonium bromide (CTAB) is reported here as a function of surfactant concentration. Reaction rate decreases as the CTAB/water ratio is increased in the parent microemulsions. Polymer particles in the latexes grow with conversion; they also become bigger as the initial surfactant content is increased. Number-average molar masses are smaller than those expected by termination by chain transfer to monomer, but weight-average molar masses increased as the surfactant concentration in the parent microemulsion is raised. However, the latter are much smaller than those obtained by polymerization in an emulsion stabilized with the same surfactant. Possible explanations to this unusual behavior are provided here.