Acrylate Copolymer Latex Research Articles

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 Tg. As VDC content increased beyond 90 wt %, the MFFT curve plotted against VDC content rose sharply, in contrast with the Tg 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

Paper Sheets Treated by Polymeric Substances

Poly(vinyl acetate) (PVAc) and vinyl acetate with butyl acrylate (VAc-BuA) copolymer latices are prepared by semicontinuous emulsion polymerization technique. The prepared latices are used in paper treatment using two different techniques. In the first technique, the latices are added during the paper sheet formation, but in the second one the untreated paper sheets are dipped in either the polymer or acetone polymer solution of different concentrations. The effect of different concentrations of the prepared emulsion latices by using different emulsifier and initiator concentrations on the paper sheet is studied. Increasing the initiator concentration in the preparation of PVAc latex decreases the retained polymer on the treated paper sheets. Also, increasing the butyl acrylate percentage in the copolymer latices improves the mechanical properties. The water uptake of the treated paper sheets is decreased by increasing the retained polymer. The effect of thermal treatment of the treated paper sheets is investigated.

Preparation and characterization of polystyrene and styrene-butyl acrylate copolymer latices

Emulsion polymerization of styrene (S) and emulsion copolymerization of styrene with butyl acrylate (BuA) using potassium persulfate (KPS)/different aromatic aldehydic sodium bisulfite adducts as developed redox pair initiation systems were investigated at variable initiator, emulsifier concentrations and feed monomer compositions for studying the morphological characteristics of the obtained latices. It was found that the developed redox pair initiation system increased the number of polymer particles per unit volume of water ( Nt) more than the classical system. Also, N t , decreased with increasing initiator concentration, but increased with increasing emulsifier concentration for both the classical and developed ones. The volume-average particle diameter D ̄ v was found to be dependent on the different redox initiators: potassium persulfate/methylbenzaldehyde sodium bisulfite (KPS/MeBSBS), potassium persulfate/chlorobenzaldehyde sodium bisulfite (KPS/CBSBS), potassium persulfate/methoxybenzaldehyde sodium bisulfite (KPS/MBSBS), potassium persulfate/benzaldehyde sodium bisulfite (KPS/BSBS) and potassium persulfate/sodium bisulfite (KPS/SBS) to the powers 0.15, 0.27, 0.30, 1.80 and 0.70, respectively, while N t , is dependent on emulsifier concentration to the powers 0.48, 1.00, 2.08, 3.33 and 4.41 with respect to the different redox systems KPS/SBS, KPS/MBSBS, KPS/CBSBS, KPS/BSBS and KPS/MeSBSB. The polydispersity index ( D w D w ) for the emulsion latices prepared using different emulsifier concentrations was found to be in the range 1.00–1.29, i.e. they are relatively narrow. This means that the emulsion polymerization of styrene was not in the so-called induction period. Increasing BuA ratio in the feed monomer composition of the prepared S/BuA copolymer lattices led to a decrease in N t .

Synthesis of Silicone - Acrylate Copolymer Latexes and their Film Properties

Emulsion copolymerization of silicones (octomethyl tetracyclosiloxane, D4 and methacryloxypropyl trimethoxy silane, MATS) and acrylics was carried out using three different polymerization processes: semicontinuous monomer emulsion addition, batch and initiator solution addition. Results showed that only the semicontinuous process led to a stable latex with monodisperse particles. Various polymerizations were carried out through this process with varying silicone/acrylic ratios and MATS content. Films were obtained from different latexes: their properties are significantly influenced by silicone and MATS contents in copolymers.

Synthesis of Silicone – Acrylate Copolymer Latexes and their Film Properties

Synthesis of Silicone – Acrylate Copolymer Latexes and their Film Properties

Nonwoven glued cloth for reinforcement of polymer composites

The strengthening properties of fibres in polymer composite materials are realized to a greater degree when reinforcing systems in the form of cloth with a two-dimensional structure of filaments held together by frictional forces alone are used. However, in fabrication of composites with the wet impregnation method (for example, in fabrication of prepregs based on polyether resins), the inherent strength of such cloth is insufficient to ensure its passage with respect to changes in the impregnation unit. The purpose of the present study was to create nonwoven cloth bound with a binder which should ensure the necessary strength and preserve the textile structure of the material in the stage of impregnation with a synthetic binder and at the same time be able to subsequently dissolve in the polymer medium and not impede the mobility of the fibres during molding of articles. The analysis of the published data indicates the promise of using acrylic copolymer latexes as binders in production of glued nonwoven materials for the domestic sector due to their elevated technological and operational characteristics, aggregate stability, sufficient adhesion to fibre linens, and elevated deformation-strength characteristics of latex films in particular [1, 2]. An experimental batch of nonwoven material was prepared for the study from Nitron polyacrylonitrile fibre wastes (STP 6-01-15-01-78) with a surface density of 100-10 g/m 2. The material was formed on a Ch-llSh-1 combing machine, excluding the stage of mechanical binding of the fibres (by needle punching or piercing). Based on the specific requirements for the binder, noncross-linked carboxyl-containing acrylic dispersions with a concentration of dry residue of no less than 30% were investigated. The capillary rise method showed that Nitron fibre is satisfactorily wet with the acrylic dispersion with a concentration of 15-25 wt. %: Concentration of dispersion, % Capillary rise height, mm

Influnce of Initiator Type on the Latex Particles Size in Emulsion Copolymerization of Styrene With Butyl Acrylate

Abstract Styrene (St) and butyl acrylate (BA) copolymer latexes were synthesized using two polymerization systems with different initiators. In System I a water-soluble initiator (K2S2O8/Na2S2O4·2H22O) was used. System II contained hydroperoxide groups bound to water-insoluble oxidized isotactic polypropylene (OPP) powder combined with the Fe2+/ethylenediaminetetraacetic acid activator. The size of PSt/PBA latex particles (D) of the synthesized copolymer latexes was determined. The dependence of D and surface tension was studied as a function of monomer conversion. It was found that the above parameters are dependent on the type of initiation system employed. In System II, larger latex particles are formed of increasing size as a function of monomer conversion. Smaller particles are produced in System I, and their size is almost unchanged during polymerization.

Effect of Film Aging on the Pervaporation Properties of Latex Membranes

Abstract Latex membranes have recently been investigated for their application in pervaporation separation processes. Acrylonitrile-butyl acrylate copolymer latex membrane showed selective permeation to water in pervaporation with water-ethanol mixtures. Different from solvent-cast membranes, the pervaporation properties of latex membranes were found to change with the membrane aging time or under different aging conditions. It is shown that aging leads to better membrane fusion, thus decreasing the permeation rate and increasing the separation factor. Aging the membrane in a medium which keeps the latex particle from good fusion would cause a high permeation rate but a low separation factor. Based on our observations, a comprehensive transport mechanism of the permeant through latex membranes during pervaporation is proposed.

Some water‐borne adhesives based on styrene butyl acrylate copolymer latices

Emulsion adhesives can be subdivided on the basis of chemistry to acrylics, styrene‐butadiene latices, styrene‐butadiene/natural rubber blends, vinyl acetate copolymers and natural rubber latices. Acrylics have the advantages of being easily modified by changing the type and amount of polar comonomers. They have excellent ageing characteristics.

Removal of industrial latex dispersions from waste waters using microporous alumina membranes

A study has been made on the utilization of alumina membranes for the microfiltration of dilute latex dispersions in latex production. In this operation tubular microfiltration membranes were used with the mean pore diameter equal to 0.1 μm. Feed circulation velocities ranging from 0.4–3.6 m/s (Reynolds number, Re=2,200–20,000) were investigated. It has been shown that the ceramic membranes used are acceptable for microfiltration of industrial waste water containing poly(vinyl acetate) and acrylic copolymer latex dispersions. A limiting flux was observed which depended on the species of the latexes and on the flow velocity of the feed. The decrease in the flux of permeate was attributed to the resistance of the cake (gel) layer formed on the membrane or blocking of the pores in the membrane. Several technical parameters of interest such as flux characteristics, membrane fouling, and latex stability are discussed.

Semicontinuous emulsion copolymerization to obtain styrene–methyl acrylate copolymers with predetermined chemical composition distributions

AbstractFour types of emulsion copolymerization processes were applied to produce various styrene–methyl acrylate copolymer latices. (1) Batch emulsion copolymerization. (2) Monomer starved semicontinuous emulsion copolymerization, i.e., a monomer mixture of constant composition was fed to the reactor at a constant rate. Sufficiently low addition rates led to homogeneous copolymers. (3) Optimal addition rate profiles were used to produce homogeneous emulsion copolymers in relatively short times. The profiles were determined in a semiempirical way, and applied to three different copolymer compositions. (4) We made an attempt to determine an addition rate profile to produce a heterogeneous emulsion copolymer with predetermined heterogeneity, i.e., a copolymer of which the chemical composition distribution (CCD) did not consist of one narrow peak, as with homogeneous copolymers, but had a predetermined broadness profile. Strategies (2) and (3) were used to produce homogeneous emulsion copolymers with varying fractions of styrene. Strategy (3) was also used to demonstrate the influence of the monomer ratio on the kinetics. The advantage of this method is that the monomer ratio is constant over the whole conversion range in the latex particles. High performance liquid chromatography (HPLC) was used to determine the homogeneity/heterogeneity of the copolymers produced, and proved to be invaluable in determining the optimal addition rate profile. The final goal will be to study the influence of the chemical composition distribution (CCD) on mechanical properties of these copolymers, as both homopolymers used in this study have quite differentglass transition temperatures; the results will be published later. © 1993 John Wiley & Sons, Inc.

The effect of latex particle size on the rheology of thickened dispersions

The rheological behavior of model 100-nm poly(methyl methacrylate) (PMMA) latices thickened with hydroxyethyl cellulose (HEC) and with commercial Hydrophobe-modified Ethoxylated URethane (HEUR) associative polymers are compared with thickened 220-nm model PMMA latices. This study also includes a model film-forming (i.e., low glass transition temperature) methyl acrylate copolymer latex and two commercial 100-nm latices. In HEC-thickened pigmented and unpigmented dispersions, the smaller latices (at 0.32 volume fraction) are higher in viscosity due to a greater surface area and the related effect of hydration on the effective volume fraction of the dispersion. In HEUR associative thickeners, the viscosity of the smaller particle size latex is also influenced by the hydrophobicity of the synthesis surfactant, its concentration in the aqueous phase, particle separation distances and ion-dipole interactions. The viscosity is also dependent on the ratio of free surfactant to associative thickener concentration, the amount of formulation surfactant added with titanium dioxide in a pigmented coating, and on the adsorption of HEUR thickener on the latex, as determined by the relative size of the HEUR hydrophobes to that of the conventional surfactants. The studies indicate that HEUR associative thickeners facilitate lower viscosities at low shear rates (not attainable with cellulose ethers) in 100-nm latices, due to network disruption related to an excess of conventional surfactant in the total formulation.

Crosslinking ability of styrene—butyl acrylate copolymer latices functionalized with glycidyl methacrylate

Styrene—butyl acrylate copolymers functionalized with glycidyl methacrylate have been produced by emulsion polymerization using either a batch terpolymerization process or a semi-continous process, in some cases with delayed addition of the glycidyl monomer. The location of the epoxy groups has been studied by surface analysis using soap adsorption methods, and also by kinetic analysis of the results of titration with HCl. It has thus been possible to analyse the distribution of the epoxy groups inside the particle. The crosslinking reaction was carried out with hexamethylene diamine introduced into the latex just before use; film formation was by simple water evaporation and was followed by maturing of the films for up to 6 weeks at room temperature or by thermal treatment for 12 h at 100 °C. The crosslinking process was followed by swelling experiments or by measurement of the mechanical properties. These mechanical properties are very dependent upon the radial distribution of the glycidyl monomer units, which is itself governed by the polymerization process. The material may be viewed as a highly crosslinked network with soft, poorly crosslinked, inclusions.

Particle size as it relates to the minimum film formation temperature of latices

AbstractThe relationship between the particle sizes and minimum film formation temperature (MFT) of polymer colloids was studied. Early workers had developed theoretical models predicting small particle colloids should coalesce easier and have lower MFTs than those of large colloids. Early published work examining this question reported that MFT was independent of particle size. In 1990, Eckersley and Rudin, using monodisperse acrylic latexes ranging from 148–1234 nm, reported finding that MFT was a function of particle size as predicted.We synthesized a series of monodisperse acrylic copolymer latexes ranging from 63–458 nm and measured MFTs of these latexes and blends of them. We have also found particle size does affect MFT with small particle polymer colloids having lower MFTs than larger ones. Our results differ somewhat in that the MFTs of our latexes are below the glass transition temperatures (Tg) of the polymers while Eckersley et al. report MFTs above Tg.

Structure-property relationships in styrene-butyl acrylate emulsion copolymers: 2. Viscoelastic properties of latex films-experimental results and simulation

Dynamic mechanical properties as a function of temperature (−100 to 130°C) have been investigated on films made from styrene-butyl acrylate copolymer latexes prepared by emulsion polymerization using three different processes and various comonomer compositions ( 25 75 , 50 50 , 75 25 ) so as to obtain different particle morphologies. With the homogeneous copolymers, it was found that the variation of the viscoelastic properties vs. the composition can be modelled with a linear law, which shows the similarity, at a molecular level, between a two-phase composite and a homogeneous copolymer. In the case of core-shell or multilayered latex particles, thermomechanical analysis of the corresponding films suggests that two or three phases exist; the nature and the composition of the matrix and inclusion phases were deduced from the simulation of the experimental data using a self-consistent composite model based on Kerner's equation adpated by Dickie for a strain model.

Influence of the electroviscous effect and particle swelling on the hydrodynamic behavior of acrylate copolymer latices

We have demonstrated that the dissociation of carboxylic groups on the polymer particle surface induces changes in the effective hydrodynamic volume due to an increased electroviscous effect and swelling. The influence of the former effect on the hydrodynamic properties of dispersions predominates, so that even a small amount of acrylic acid (1 and 2%) in copolymers with ethyl acrylate caused a strong increase in the hydrodynamic volume of polymer particles after their alkalinization, while the swelling of these particles under the same conditions was negligibly small, as shown by light scattering measurements. The presence of styrene in acrylate copolymers resulted in the suppression of both these effects.

Characterization of particle surface and morphology in vinyl acetate-butyl acrylate emulsion copolymers ? Influence of the copolymerization pathway

Surface characterization was investigated in vinyl acetate (VAc) butyl acrylate (BuA) copolymer latexes of various compositions and prepared with four different emulsion polymerization processes: conventionnal batch, composition-controlled batch, core-shell, emulsifier-free semi-continuous. Surface end-groups (sulfate or carboxylic) titration results were first compared and discussed according to the type of process and as a function of conversion. As previously shown [1], it was confirmed that batch latex particles present a heterogeneous structure with a rich VAc outlayer, as in core-shell particles. As expected, semi-continuous and composition-controlled batch particles exhibit surface end-group characteristics revealing a more homogeneous distribution of both monomers within the particles. These differences in particle morphology were corroborated by analyzing water-polymer interface in these latexes using the soap titration method, with the sodium dodecyl sulfate (SDS) or sodium hexadecyl sulfate (SHS) as emulsifier probes. When the BuA was batch-polymerized onto PVAc seed particles, the estimated surface composition seemed to show that probably phase rearrangement occurs in the particle during the synthesis or upon aging. It was also confirmed that SDS displays an abnormal adsorption due to complexation and solubilization in the rich-VAc shell of the particles.

Comment on “quantitative determination of the surface composition of acrylate copolymer latex films by XPS (ESCA)” by A. P. Pijpers and W. A. B. Donners, j. polymer sci., polym. chem. edn. 23, 453-462 (1985)

Comment on “quantitative determination of the surface composition of acrylate copolymer latex films by XPS (ESCA)” by A. P. Pijpers and W. A. B. Donners, j. polymer sci., polym. chem. edn. 23, 453-462 (1985)

Reply to Gardella et al.'s “comments on ‘quantitative determination of the surface composition of acrylate copolymer latex films by XPS (ESCA)’”

Reply to Gardella et al.'s “comments on ‘quantitative determination of the surface composition of acrylate copolymer latex films by XPS (ESCA)’”

Comparison of micromechanical properties of latex films obtained by different emulsion copolymerization pathways

A comparative study is reported on the micromechanical behaviour of polymer films made from vinyl acetate-butyl acrylate (VAc-BuA) copolymer latices prepared by different emulsion processes: (i) conventional batch, (ii) two-step polymerization, (iii) corrected batch, and (iv) mixture of the two corresponding homopolymers. Using special equipment well adapted for micromechanical analysis, the real and imaginary parts of the dynamic shear modulus ( G′ and G″ respectively) and the internal friction (tan δ = G″ G′ ) of these films were measured as a function of temperature (from 100 K to 340 K, i.e. in the glass temperature zone of both hompolymers) and of frequency (from 5 × 10 −5 Hz to 5 Hz). Results are compared and discussed in relation to particle morphology of the latex from which the polymer films were obtained. An analysis of the results confirms that the plots of tan δ would clearly show the inadequacy of time-temperature superposition for the dynamic mechanical behaviour of polymer blends in the range of the glass transition temperature.