Starve fed emulsion copolymerization of vinyl acetate and 1‐hexene at ambient pressure

A novel emulsion copolymer of vinyl acetate (VAc) and 1‐hexene was synthesized at ambient pressure. The feeding technique, initiation system and reaction time of the copolymerization were optimized based on molecular characteristics such as the weight contribution of 1‐hexene in the copolymer chains and glass transition temperature (T_g) as well as on bulk properties like minimum film‐formation temperature (MFFT) and solid content. According to nuclear magnetic resonance spectroscopy and differential scanning calorimetry results, the combination of starve feeding and redox initiation, within a reaction time of 4 h, effectively led to the copolymerization at ambient pressure between highly reactive polar VAc monomers and non‐polar 1‐hexene monomers of low reactivity. The copolymer showed a lower T_g and MFFT, and a reasonable solid content compared to the poly(vinyl acetate) (PVAc) homopolymer. The consumption rate, hydrolysis of acetate groups and chain transfer reactions during the polymerization were followed using infrared spectroscopy. Based on the results, the undesirable reactions between the VAc blocks were hindered by the neighbouring 1‐hexene molecules. Tensile testing revealed an improvement in the toughness and elongation at break of VAc–1‐hexene films compared to PVAc films. © 2014 Society of Chemical Industry     

Effect of vinylidene chloride content on film-formation property of vinylidene chloride-methyl acrylate copolymer latex

Minimum film-formation temperature (MFFT) of vinylidene chloride (VDC)-methyl acrylate (MA) copolymer latexes prepared by batch emulsion polymerization with various compositions from 20 to 97 wt % of VDC were measured. For latexes with VDC content below 90 wt %, MFFT was similar to polymer T_g. As VDC content increased beyond 90 wt %, the MFFT curve plotted against VDC content rose sharply, in contrast with the T_g curve that descended smoothly. Measurements of infrared absorption of latexes in the dispersed state, and X-ray diffraction and infrared absorption of lyophilized polymers were conducted on 40 : 60, 80 : 20, and 95 : 5 VDC-MA specimens. These observations indicated that only 95 : 5 VDC-MA specimens were highly crystalline. It was therefore believed that film-formation property of latex with high VDC content was significantly affected by polymer crystallinity of particles in the dispersed state. Morphology and oxygen gas transmission rate of heat-treated and non-heat-treated coatings of 95 : 5 VDC-MA latex were investigated. Heat treatment of coatings beyond the temperature at which crystalline polymer began to melt induced effective particle coalescence, resulting in reduced oxygen gas transmission rate. This supported our belief that film-formation property of VDC-MA latex with high VDC content was significantly affected by polymer crystallinity. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 565–572, 1998     

Miscibility enhancement on the immiscible binary blend of poly(vinyl acetate) and poly(vinyl pyrrolidone) with bisphenol A

The miscibility behavior and hydrogen bonding of ternary blends of bisphenol A (BPA)/poly(vinyl acetate) (PVAc)/poly(vinyl pyrrolidone) (PVP) were investigated by using differential scanning calorimetry and Fourier transform infrared spectroscopy (FTIR). The BPA is miscible with both PVAc and PVP based on the observed single T_g over the entire composition range. FTIR was used to study the hydrogen-bonding interaction between the hydroxyl group of BPA and the carbonyl group of PVAc and PVP at various compositions. Furthermore, the addition of BPA is able to enhance the miscibility of the immiscible PVAc/PVP binary blend and eventually transforms into miscible blend with single T_g, when a sufficiently quantity of the BPA is present due to the significant Δχ and the ΔK effect.     

单组分聚醋酸乙烯酯乳液的改性研究

以AA-PVA(乙酰乙酰化聚乙烯醇)为保护胶体、丙烯酸丁酯(BA)和叔碳酸乙烯酯(VeoVa10)为聚醋酸乙烯酯(PVAc)乳液的共聚改性单体,制得改性PVAc乳液胶粘剂。研究结果表明:当聚合温度为75℃、AA-PVA浓度为5%、w(BA)=7%和w(VeoVa10)=16%(均相对于PVAc乳液质量而言)时,相应改性PVAc乳液的剪切强度和耐水性俱佳。     

PVAc耐水性能改性研究

以过硫酸钠作为引发剂,以甲基丙烯酸甲酯(MMA)、叔碳酸乙烯酯(VeoVa10)和丙烯酸丁酯(BA)作为醋酸乙烯酯(VAc)的共聚改性单体,采用先预乳化后半连续滴加法制备改性聚醋酸乙烯酯(PVAc)乳液.探讨了搅拌速率、共聚单体配比、聚乙烯醇(PVA)和引发剂含量等对改性PVAc乳液性能的影响.结果表明:当m(VAc ...     

Study of miscibility of poly(vinyl acetate) and poly(vinyl alcohol) blends by fluorescence spectroscopy

Secondary relaxation of poly(vinyl alcohol) (PVA), poly(vinyl acetate) (PVAc), and their blends in different proportions (9 : 1, 1 : 1, and 1 : 9) were studied by photoluminescence of anthracene, fluorescein, and both probes dissolved in the polymer blends. The temperature of the glass transition in the homopolymers was determined by the radiationless deactivation of anthracene as T_g(PVAc) ? 304 K and the photobleaching of fluorescein as T_g(PVA) ? 350 K. The relaxation processes of the different phases of the polymer blends occur at temperatures close to the homopolymers, which may be explained by the localization of each molecular probe within the matrix. These deactivation curves, however, are not similar to those of the individual homopolymers, suggesting a partial miscibility between these polymers. © 1995 John Wiley & Sons, Inc.     

Non equilibrium annealing behavior of poly(vinyl acetate)

The water absorbed by poly(vinyl acetate), PVAc, at 23°C was found in two states. The first, which can account for up to 4 weight percent, was bound to the polymer. The second was in a freezable or clustered form. The latter type of water had no effect on PVAc's glass temperature, whereas, the former kind plasticized T_g. In annealing studies, the enthalpic and dielectric response of PVAc when held at a fixed temperature increment, ΔT, below T_g, was observed to be independent of the amount of bound water. The time dependence of the shift in the dielectric relaxation spectrum and the recovery of the enthalpy towards its equilibrium value as PVAc approached its equilibrium glassy state from a lower temperature as compared to a higher temperature was initially slower. This delayed response to expansion was of the order of the polymer's average relaxation time at the lower temperature. A model was proposed to explain this asymmetric behavior based upon changes in the polymer's free volume as well as its occupied volume.     

Preparation and characterization of biodegradable polymer blends from poly(3‐hydroxybutyrate)/poly(vinyl acetate)‐modified corn starch

Biodegradable polymer blends prepared by blending poly(3‐hydroxybutyrate) (PHB) and corn starch do not form intact films due to their incompatibility and brittle behavior. For improving their compatibility and flexibility, poly(vinyl acetate) (PVAc) was grafted from the corn starch to prepare the PVAc‐modified corn starch (CSV). The resulting CSV consisted of 47.2 wt% starch‐g‐PVAc copolymer and 52.8 wt% PVAc homopolymer and its structure was verified by FT‐IR analysis. In comparison with 35°C of the neat PVAc, the glass transition temperature (T_g) of the grafted PVAc chains on starch‐g‐PVAc was higher at 44°C because of the hindered molecular mobility imposed from starch on the grafted PVAc. After blending PHB with the CSV, structure and thermal properties of the blends were investigated. Only a single T_g was found for all the PHB/CSV blends and increased with increasing the CSV content. The T_g‐composition dependence of the PHB/CSV blends was well‐fitted with the Gordon‐Taylor equation, indicating that the CSV was compatible with the PHB. In addition, the presence of the CSV could raise the thermal stability of the PHB component. It was also found that the presence of the PHB and PVAc components would not hinder the enzymatic degradation of the corn starch by α‐amylase. POLYM. ENG. SCI., 55:1321–1329, 2015. © 2015 Society of Plastics Engineers     

Ternary nanocomposites: Curing,morphology, and mechanical properties of epoxy/thermoplastic/organoclay systems

The influence of two organically modified montmorillonites on the curing, morphology and mechanical properties of epoxy/poly(vinyl acetate)/organoclay ternary nanocomposites was studied. The organoclays and poly(vinyl acetate) (PVAc) provoked contrary effects on the epoxy curing reaction. Ternary nanocomposites developed different morphologies depending on the PVAc content, that were similar to those observed in the epoxy/PVAc binary blends. The organoclays were only located in the epoxy phase independently of the morphology. All nanocomposites showed intercalated structures with similar clay interlayer distances. Both PVAc and organoclays lowered the T_g of the epoxy phase, the presence of clays did not influence the T_g of the PVAc phase. The addition of the organoclays to the epoxy improved stiffness but lowered ductility while the adition of PVAc improved toughness although reduced stiffness of epoxy thermoset. Ternary nanocomposites exhibited optimal properties that combine the favourable effects of the clay and the thermoplastic. POLYM. COMPOS., 37:2184–2195, 2016. © 2015 Society of Plastics Engineers     

聚醋酸乙烯酯/纳米SiO_2复合乳液的制备与性能

采用原位乳液聚合法制备了聚醋酸乙烯酯／纳米二氧化硅复合乳液。考察了纳米二氧化硅在聚醋 酸乙烯酯乳液内及乳胶膜中的分散性:纳米二氧化硅用量对复合乳液性能的影响。结果表明:与普通乳液相 比,复合乳液的干态粘接强度和耐水性明显提高。     

Stress development and film formation in multiphase composite latexes

Designed appropriately, multiphase soft-core/hard-shell latex particles can achieve film formation without the addition of a coalescing aid, while preserving sufficient film hardness. Achieving optimal performance in these materials requires an understanding of how particle morphology affects film formation and stress development in the film. In this study, soft-core/hard-shell latex particles with different shell ratios, core and shell glass transition temperatures (T _gs), and particle sizes (63–177 nm) were synthesized using a two-stage emulsion polymerization. The film formation behavior of the composite particles was investigated with cryogenic scanning electron microscopy, atomic force microscopy, and measurements of the minimum film formation temperature (MFFT). Results show that film formation was enhanced for particles with thinner hard shells, smaller particle size, and a smaller difference in T _g between the core and shell polymers. For example, the MFFT decreased and the particle deformation increased for particles with thinner shells and smaller particle sizes. Stress development during drying was characterized using a cantilever beam bending technique. A walled cantilever design was used to monitor stress development without the complication of a lateral drying front. The film formation behavior and stress development correlated well with practical paint properties like scrub resistance and gloss.     

Preparation and structure control of hollow polymer particles: Influence of seeded emulsion polymerization and alkalization treatment process

Hollow polymer latex particles containing a hydrophilic core were prepared by seeded emulsion polymerization with MAA/BA/MMA/St as comonomers, followed by stepwise alkalization treatment with ammonia. The size and morphology of composite latex particles was determined by TEM. The effects of the seeded emulsion polymerization conditions and alkalization treatment on the size and hollow structure of latex were investigated. The results showed that the optimum content of crosslinking agent in the shell polymers was about 0.5–1.0 wt %, emulsifier was about 0.8–1.1 wt %, and the core/shell weight ratio was 1/7. To obtain uniform hollow latex particles with large size, the starved feeding technique should be adopted in seeded emulsion polymerization, and the neutralization temperature should equal to the T_g of the shell polymer. Then, the obtained polymer particles under this condition had an excellent hollow structure. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

马来酸酐改性聚醋酸乙烯酯乳液的研究

以马来酸酐(MA)作为醋酸乙烯酯(VAc)的改性共聚单体,采用半连续种子乳液聚合法合成了改性聚醋酸乙烯酯(PVAc)乳液,并考察了MA含量对VAc/MA共聚乳液性能的影响。结果表明:当w(MA)=0.3%～0.4%(相对于VAc质量而言)时,改性乳液的聚合稳定性、储存稳定性和稀释稳定性良好;随着MA含量的不断增加,种子反应阶段回流时间延长,共聚速率变慢,最终合成的改性乳液黏度逐渐增大;当w(MA)=0.4%时,改性乳液的综合性能相对最好,其粘接强度(9.70 MPa)比VAc均聚乳液增加了70%。     

PVAc Microspheres via Semicontinuous Emulsion Polymerization: Synthesis,Characterization, Kinetic,and Surface Morphology Studies

Poly (vinyl acetate) (PVAc) latexes are economically important products with many desirable features. They are used as adhesives for porous materials in various processing stages of industries. Synthesis parameters have an important role on the physico-chemical properties of PVAc latexes such as: viscosity, average molecular weight, degree of polymerization, and surface morphology. In this work, PVAc was prepared via semicontinous emulsion polymerization (delayed monomer and initiator addition process) in the presence of ammonium persulfate (APS) as conventional anionic initiator, poly (vinyl alcohol) (PVA) as stabilizer, and sodium lauryl sulfate (SLS) as anionic emulsifier. The surface morphology of PVAc microspheres was, examined using a scanning electron microscope (SEM) and atomic force microscope (AFM). It is evident from the SEM photographs that all the particles became microspheres and are uniform in shape. The use of AFM for imaging of polyvinyl acetate confirms a typical sphere polymer. The effect of changes in the different parameters such as concentration of emulsifier, initiator concentration, and presence or absence of buffer on the vinyl acetate (VAc) conversion, the steady state polymerization rate, the viscosity-average molecular weight, and the final latex viscosity of synthesized PVAc were investigated. The effects of anionic emulsifier on the synthesized PVAc are also compared with those obtained by the nonionic emulsifier. The comparison indicated that the VAc monomer conversion and the final latex viscosity of the anionic system were higher than for the nonionic system but the viscosity-average polymer molecular weight of the anionic system was lower than that of the nonionic system. The adhesive strength of the synthesized PVAc latex was examined and the load and deflection data were reported.     

Effect of colophony emulsion on the adhesive properties of vinyl acetate/n‐butyl acrylate copolymeric latex

We prepared a novel copolymeric latex of vinyl acetate and n‐butyl acrylate (V‐B) using a semibatch emulsion polymerization process. The glass‐transition temperature (T_g), steady viscosity, flow activation energy (E_f), dynamic moduli, and amphiphilic properties of the V‐B latex in the presence of colophony were systematically investigated. The experimental results demonstrate that excellent adhesive behaviors were achieved for the V‐B latex blended with 20 wt % colophony, whereas good adhesive performance was related to the moderate T_g, viscosity, E_f, storage modulus, and low contact angle on the adherent. The debonding mechanisms for V‐B and its colophony‐modified latexes were analyzed. A possible mechanism for the V‐B latex blended with colophony emulsion was determined. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

DSC and DMTA characterization of ternary blends

The phase behavior of ternary blends made of poly(epichlorohydrin) (PECH), poly(vinyl acetate) (PVAc) and poly(methyl methacrylate) (PMMA) has been investigated by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). DMTA measurements have been shown to be more sensitive than DSC for the detection of a second phase, for the determination of the composition of each phase, and the distribution of PECH in each of them. About 70% PECH was required to obtain a single narrow T_g in the ternary system, which suggests a single homogeneous phase in the limit of sensitivity of DMTA. This study also emphasizes the importance of the composition of the immiscible polymer pair (i.e. the PVAc/PMMA pair in the PECH/PVAc/PMMA system), in addition to the thermodynamic interaction parameters, for controling the phase behavior of ternary systems.     

Modified emulsifier‐free emulsion polymerization of butyl methacrylate with ionic or/and nonionic comonomers

A modified emulsifier‐free emulsion polymerization of butyl methacrylate (BMA) with ionic or/and nonionic comonomers was successfully used to prepare nanosized poly(butyl methacrylate) (PBMA) latices with high polymer contents. After seeding particles were generated in an initial emulsion system, consisting of a portion of BMA, water, ionic comonomer [sodium styrenesulfonate (NaSS)] or nonionic comonomer [2‐hydroxyethyl methacrylate (HEMA)] and potassium persulfate, most of the BMA monomer or the mixture of BMA and HEMA was added dropwise to the polymerizing emulsion over a period of 6–12 h. Stable latices with high PBMA contents up to 27% were obtained. It was found that the latex particle sizes (2R_h) were largely reduced (34 nm) by the continuous addition of monomer(s) compared to those (107 nm) obtained by the batch polymerization method. The effect of comonomer concentration on the particle size, the number of PBMA particles/mL of latex (N_d), and the molar mass (M_w) of copolymer during the polymerization were discussed. The surface compositions of latex particles were analyzed by X‐ray photoelectron spectroscopy, indicating that the surface of latex particles was significantly enriched in NaSS or/and HEMA. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3080–3087, 2004     

Thermodynamic studies related to emulsion polymerization

Liquid–liquid and vapor–liquid phase equilibria for the binary, ternary, and quaternary systems of vinyl acetate, surfactant, water, and poly(vinyl acetate) (PVAc) were obtained using liquid–liquid equilibria, inverse gas chromatography, and the headspace methods. The Flory–Huggins interaction parameters for the different species in the emulsion polymerization of PVAc latices are reported. These parameters could not be used to predict the phase equilibria because of their strong dependence on concentration. The UNIFAC‐vdW‐FV model was applied to predict the vapor–liquid equilibria in the binary and ternary systems containing vinyl acetate, 4‐nonylphenol polyethoxilate surfactant, and PVAc. The predicted results compare favorably with the experimental data for all systems. Diffusion coefficients were also measured for the solvents in the PVAc. Analysis confirmed that the diffusion in the latex particles was so fast compared to the reaction that the assumption of uniform monomer composition through the particles was valid. On the other hand, the results indicate that the complex thermodynamic interactions will lead to changes with time in the monomer concentration in the reacting polymer phase. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

聚乙烯吡咯烷酮对聚醋酸乙烯酯共聚乳液性能的影响

以醋酸乙烯酯(VAc)和丙烯酸丁酯(BA)为聚合单体、聚乙烯醇(PVA)为保护胶体、聚乙烯吡咯烷酮(PVP)为分散剂、十二烷基硫酸钠(SDS)为表面活性剂及羟丙基甲基纤维素(HMPC)为增稠剂等,制备出一种低黏度聚醋酸乙烯酯(PVAc)乳液胶粘剂。考察了PVP用量对PVAc乳液胶粘剂的黏度、粘接性能、稳定性能及单体转化率等影响。结果表明:红外光谱(FT-IR)证实,PVP参与了VAc和BA的接枝共聚反应;适量的PVP可使乳液黏度明显降低;当w(PVP)=0.15%时,PVAc乳液胶粘剂的综合性能相对最好。     

Gas transport in poly(vinyl benzoate)

The transport parameters of nine gases (O₂, N₂, CO₂, He, Ne, Ar, Kr, Xe) through poly(vinyl benzoate) (PVB) have been measured by the time lag method above and below the glass transition temperature, T_g The results are compared with the related data of poly(vinyl acetate) (PVAc) by Meares and discussed as the effect of replacement of the methyl group by a phenyl group in the side chain of PVAc. Small molecules, such as H₂, He, and Ne, diffuse more easily through PVAc than PVB, but the tendency is reversed for the larger gases. The activation energy for diffusion is proportional to the squares of the Lennard–Jones diameters of the gases below the T_g. On the other hand, above the T_g, linear relation is obtained to the cubes of the diameters. Solubility behavior is discussed by comparing the heats of solution for PVB and PVAc.