Emulsion Copolymerization Of Vinyl Acetate Research Articles

Emulsion Copolymerization of Vinyl Acetate and Vinyl Silanes: Kinetics and Development of Microstructure

AbstractThe batch emulsion copolymerization of vinyl acetate with different vinyl silane functional monomers (vinyl trimethoxysilane [VTMS], vinyl triethoxysilane [VTES], and vinyl silanetriol [VSTO]) is studied. The nature of the silane strongly affects the development of the microstructure and crosslinking ability of the latexes. A combination of techniques (Soxhlet extraction, centrifugation, assymetric‐flow field flow fractionation AF4/MALS/RI) shows that the factor controlling the molar mass and crosslinking density is the degree of hydrolysis of the alkoxysilane, producing higher molar masses and degrees of crosslinking when the degree of hydrolysis is high. Thus, the copolymer containing VSTO produced a very crosslinked latex, the one with VTMS produced a latex with a low degree of crosslinking in the wet state that can yield high degrees of crosslinking upon drying, and the latex with VTES do not produce significant amounts of crosslinking neither before nor after drying.

Smart reactors – Combining stimuli-responsive hydrogels and 3D printing

Reactor design and development are key disciplines in process engineering. In order to keep up with modern-day production demands, new reactor concepts have to be conceived, which transcend the mere purpose of a reaction vessel. With the availability of improved fabrication methods and insight into new materials, novel process integration measures and process-adapted setups can be developed to provide a new generation of reactors. The application of smart materials allows for response-triggered actuation, which can be used in setups for self-contained process control without external input. In combination with available 3D fabrication technologies, smart materials can be integrated and adapted to the reaction system demands, to develop smart reactor concepts. Herein, we demonstrate an exemplary application of a smart reactor module for an exothermic emulsion copolymerization of vinyl acetate (VAc) and Versa® 10, a vinyl neodecanoate. The flow manipulation of the reaction medium on a preparative scale is presented by using poly(N-iso-propylacrylamide) (pNIPAM) hydrogels as temperature-triggered actuators, which are able to distinguish the course of the reaction by separating the flow of reactant from product stream during continuous operation.

Mathematical Model of the Emulsion Polymerization Stability for Vinyl Acetate, Methyl Methacrylate, Butyl Acrylate and Acrylic Acid Tetra-polymers

Based on the growth of latex particles surface area during the emulsion polymerization process and the DLVO (Dergagai-Landan-Vervey-Overbeek) theory of emulsion polymerization, a mathematical model of emulsion stability is established. The main hypothesis, based on the concept that the emulsion polymerization reaction occurs very quickly, is that emulsifier placed in the polymerization system is immediately wrapped on the surface of the latex particles. It is proposed that if the latex particle surface area growth (ΔS) and the latex particle surface area which is stabilized by added emulsifier () satisfy the relationship of , the polymerization system will be a relatively stable system where N is the number of seed latex particles and (/N)0.3 and (/N)0.7 signify the surface area of each stable latex particle when the coverage rate of emulsifier is 30% and 70%, respectively. Based on this hypothesis, the influences of emulsifier amount, diameter of the seeded latexes and distribution of the emulsifier in initial emulsion and the emulsifier added dropwise during the polymerization on the emulsion polymerization stability is simulated and calculated to realize the minimum aggregation during polymerization. According to the simulation results, two optimized polymerization process parameters were determined and verified through experiments based on the emulsion copolymerization of vinyl acetate, methyl methacrylate, butyl acrylate and acrylic acid.

Effect of geometry and hybrid adhesive on strength of finger joints of Pinus elliottii subject to humidity and temperature

ABSTRACTThe optimized bonding of glued finger joints is required for structural and nonstructural applications. The use of nonspecific adhesives, combined with the joint geometry and exposure of joints to humidity and temperature, are factors that can compromise the durability of glued joints. The main objective of this study is the development of cross-linking poly(vinyl acetate) (PVAc) hybrid adhesive to produce nonstructural finger joints of Pinus elliottii with finger lengths of 6.5 and 4.5 mm. The adhesives were produced by emulsion copolymerization of vinyl acetate with n-butyl acrylate with different amounts of N-methylol acrylamide and blended with resorcinol-formaldehyde resin (RF) and aluminum chloride (AlCl3). The rheological behavior of adhesives was investigated. We found that the joint configuration and the exposition time employed influenced joint strength. The PVAc/RF adhesive showed a thicker bond line and consequent deeper penetration into the pores of the wood as verified by microscopy analysis. Statistically differences in bond strength of the adhesive joints were found with respect to different conditioning times and finger length. The highest values were exhibited by the joints produced with a finger length of 6.5 mm and glued with the hybrid adhesive (AD-4) than that joints produced with a finger length of 4.5 mm.

RAFT/MADIX emulsion copolymerization of vinyl acetate and N-vinylcaprolactam: towards waterborne physically crosslinked thermoresponsive particles

Controlled radical emulsion polymerization as a tool to synthesize thermoresponsive PVCL-based amphiphilic copolymer particles crosslinked by supramolecular hydrophobic interactions.

Semicontinuous Emulsion Copolymerization of Vinyl acetate and Butyl acrylate with Nonionic Surfactants (Triton X Series)

SummaryIn this study, the copolymerization of vinyl acetate (VAc) and butyl acrylate (BuA) in water semicontinuous emulsions made with the nonionic surfactants, Triton Xs, was studied as a function number of ethylene oxide (EO, X) and their concentrations. The copolymerization of VAc and BuA was initiated by peroxide at proper temperature in order to improve the efficiency of droplet nucleation and maintain the stability of the emulsion. The effects of EO's in the surfactant structure and surfactant concentration on latex colloidal and physicochemical properties were investigated.

Preparation of Syndiotacticity-Rich High Molecular Weight Polyvinyl Alcohol by Low Temperature Emulsifier-Free Emulsion Copolymerization of Vinyl Acetate and Vinyl Pivalate

Low temperature emulsifier-free emulsion copolymerization of vinyl acetate (VAc) and vinyl pivalate (VPi) was carried out using a redox initiation system to prepare syndiotacticity-rich high-molecular weight (HMW) polyvinyl alcohol (PVA) with high yield. The effects of the polymerization conditions on the conversion, the molecular weight, the structure of poly (vinyl acetate-co-vinyl pivalate) (P (VAc-VPi)) and syndiotacticity of PVA were investigated. With the increases of the initiator concentration, the VPi molar ratio in monomer and polymerization temperature, the degree of polymerization (DP) of PVA decreases distinctly, but VPi contents in copolymer and syndiotactic diad (S-diad) contents of PVA increase obviously. PVA with the maximum DP of 11030 can be prepared by complete saponification of P(VAc-VPi) obtained under condition that the molar ratio of KPS to monomer is 1/2000, the molar ratio of VAc to VPi is 7:3 and reaction temperature is 12°C. The highest S-diad content in PVA can be up to 59.31% while the DP of PVA decreases to 5180 under the condition that the feed ratio of VPi is 70 mol%, which means the syndiotacticity-rich HMW PVA can be prepared successfully. And the conversions of all reactions are above 80%. Syndiotacticity-rich HMW PVA is effectively prepared in this study, which is useful for the preparation of high-strength and high-modulus PVA fiber.

Quinoline-functionalized cross-linked poly(vinyl acetate) and poly(vinyl alcohol) nanoparticles as potential pH-responsive luminescent sensors

A series of cross-linked organic nanoparticles (NPs) have been prepared through emulsion copolymerization of vinyl acetate (VAc) and of luminescent quinoline based monomers in the presence of divinylbenzene. Furthermore, hydrolysis of VAc led to the respective cross-linked poly(vinyl alcohol) nanoparticles. The two luminescent vinylic quinoline derivatives employed, namely 2,4-diphenyl-6-(4-vinylphenyl)quinoline (SDPQ) or 2-(pyridin-2-ylo)-6-styrene-4-phenylquinoline (QPy), were used at feed compositions of 1mol% and 2mol%. The chemical composition and the success of hydrolysis have been assessed through infrared spectroscopy, while scanning electron microscopy verified that the spherical shape and the size (∼50–100nm) of the NPs are practically unaffected by the hydrolysis process. The pH-sensitive luminescence behavior of the NPs, arising from the protonation/deprotonation equilibrium of the quinoline groups, was investigated in aqueous dispersions or in solid state after incorporation of the NPs in a poly(lactic acid) (PLA) matrix. Depending on the system, either two distinct bands at ∼420nm and ∼480nm, corresponding to the unprotonated and the protonated form of the quinoline derivative, or a gradual shift from ∼420nm to ∼480nm were observed upon decreasing pH. The photoluminescence inspection of the surrounding aqueous environment confirmed that the leaching of the NPs from the PLA matrix is very limited or negligible. Moreover, our initial studies suggest that the photoluminescence response of the solid systems is quite fast (a few minutes), indicating that they are promising for the design of adequate solid pH-responsive luminescent sensors.

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 (Tg) 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 Tg 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

Semi-continuous emulsion copolymerization of vinyl acetate and butyl acrylate in presence of AMPS

The emulsifier-free emulsion polymerization of vinyl acetate (VAc) and butyl acrylate (BA) in the presence of 2-acrylamido-2-methylpropane sulfonic acid (AMPS) was carried out by a semi-continuous process. AMPS was a reactive surfactant in the aqueous emulsion, due to its amphiphilic structure and the unsaturated double bonds. Potassium persulfate (KPS) was used as initiator. The following factors were mainly examined: quantity of AMPS, BA and KPS concentrations, which could significantly affect the particle size and its distribution, conversion, gel content, minimum film-forming temperature, etc. The particle size and its distribution were characterized by dynamic laser particle size analyzer, and morphology of the latex particles was characterized by transmission electron microscopy (TEM). Fourier transform infrared spectroscopy was used to characterize chemical structure of copolymers. The results indicated that AMPS was successfully reacted onto the resulted copolymer of vinyl acetate and butyl acrylate. A hydrophilic sulfonic acid group in the molecular structure of AMPS tended to be distributed in particles surface after polymerization. As a result, an electrostatic repulsion between the particles was produced in order to maintain stability of the system. Thermogravimetric analysis curves suggested that as BA content increased, thermal stability of the polymer increased accordingly. The conversion-time plots with varying AMPS and initiator contents were obtained, which illustrated that the initiator concentration could greatly influence the polymerization rate and the final conversion. The TEM micrographs of the final emulsifier-free latex particles for P(VAc/BA/AMPS) system revealed small particle size in monodisperse polymer latex. The particles of the latex were measured as about 150 nm.

Semicontinuous Emulsion Co-polymerization of Vinyl Acetate and VeoVa10

The high solids semicontinuous emulsion polymerization of VAc and VeoVa10 using poly(vinyl alcohol) (PVOH) as polymeric stabilizer is investigated. It is shown that (i) PVOH strongly affects the kinetics of the process and (ii) the formation of PVOH-graft-poly(VAc–co-VeoVa10) leads to an overestimation of the gel content and an underestimation of the sol molecular weight when the standard characterization techniques are directly applied. A new method to properly characterize the MWD of these copolymers is presented. A mathematical model is used to analyze the effects of surfactant and initiator on the kinetics and polymer microstructure.

Improvement of film properties of vinyl acetate based emulsion polymers by using different types of maleic acid diesters

Two types of maleic acid diesters, dibutyl maleate (DBM) and dioctyl maleate (DOM) were used as comonomers in semicontinuous emulsion copolymerization of vinyl acetate (VAc) in order to improve the film properties of poly(vinyl acetate), PVAc emulsion polymer. The effects of the comonomer type and comonomer ratio on minimum film forming temperature (MFFT), glass transition temperature (Tg), polymer structure, molecular weights, water contact angle and water resistance of PVAc latex films were examined. It was found that MFFT and Tg of the PVAc emulsion polymer decreased by the presence of the maleic acid disters in copolymer composition. This decrease was more affected by the increasing content and alkyl chain length of the comonomers. The molecular weights of the emulsion polymers were also affected by the comonomers and their ratios. Moreover, hydrophobicity and water resistance of the PVAc latex films were increased by using DBM and DOM as comonomer.

In Line Monitoring of VAc‐BuA Emulsion Polymerization Reaction in a Continuous Pulsed Sieve Plate Reactor using NIR Spectroscopy

AbstractSummary: This work deals with the in line and in situ monitoring of the changes in residual monomer concentrations and polymer particle size in the process of emulsion copolymerization of vinyl acetate (VAc) and butyl acrylate (BuA) over the sections of a novel tubular reactor (pulsed sieve plate continuous reactor, PSPC) using NIR spectroscopy. Off‐line measurements (gas chromatographic, gravimetric and dynamic light scattering) were used as reference for the development of the multivariate PLS calibration model. All NIR spectra were on‐line collected with an IFS 28/N Bruker spectrometer using a probe (transflectance mode) immersed into the reaction medium. The calibration model and validation data were analyzed using the OPUS/QUANT software. The results indicated that there exists a good agreement between values from the NIR calibration models and the off‐line reference measured experimental data. Moreover, the on‐line NIR can detect efficiently the occurrence of disturbances during the polymerization reaction, a useful tool for the improving the process safety.

Emulsifier‐Free Emulsion Copolymerization of Vinyl Acetate and 3‐Dimethyl(methacryloyloxyethyl)ammonium Propanesulfonate and Swelling Behavior of their Copolymer Matrices

AbstractStable poly{(vinyl acetate)‐co‐[3‐dimethyl(methacryloyloxyethyl)ammonium propanesulfonate]} latexes with different compositions were synthesized by emulsifier‐free emulsion copolymerization. An unusual “overshooting” behavior of the copolymer tablets is explained based on the formation of specific clusters of oppositely oriented dipoles. The variation of their concentration with the zwitterionic monomer unit fraction, ionic strength and temperature is responsible for the differences in the swelling kinetics established. The results show that these parameters can be used to control swelling degree of copolymer matrices and their sustained drug delivery.magnified image

Investigation of Stabilization and Kinetics in the Semi‐Continuous Emulsion Copolymerization of Vinyl Acetate and Butyl Acrylate using Carboxylic Monomers

AbstractThis work investigates the influence of carboxylic monomers such as acrylic acid (AA) and methacrylic acid (MAA) on the reaction rate and the colloidal stability during semicontinuous vinyl acetate (VA) and butyl acrylate (BA) emulsion copolymerizations. A number of copolymerization runs was carried out under different reaction temperatures and concentrations of AA and MAA. Samples were collected for off‐line analysis of particle size and conversion, allowing calculations of particle number values giving an indication of the particle stability. Additionally, partitioning analysis using conductometric and potentiometric titrations were performed in order to assess the distribution of carboxylic monomers among the main phases of the latex. Results showed that for both carboxylic monomers the increasing of the reaction temperature produces an increase in the coalescence rate and that the increasing of the concentration of these monomers leads to the increase in the amount of adsorbed COOH groups on the particle surface, which enhances latex stability. Nevertheless, when the concentration of methacrylic acid was increased a strong reduction of the polymerization rate was observed with a greater incorporation of acid groups buried in the particles.

Semi‐continuous emulsion copolymerization of vinyl acetate and butyl acrylate using a new protective colloid. Part 1. Effect of different emulsifiers

AbstractVinyl acetate and butyl acrylate copolymers were synthesized in the presence of ammonium persulfate initiator, emulsifiers having different character such as non‐ionic and anionic+non‐ionic emulsifiers, and N‐methylol acrylamide as a new protective colloid in a classical glass reactor. The monomer ratio was chosen 85:15. In the case of mixture emulsifiers, the series of non‐ionic emulsifiers which have 10 to 40 moles ethoxylated nonyl phenol except 20 moles were combined with sodium dodecyl benzene sulfonate. The effects of the new colloidal stabilization agent, and different emulsifiers on the physicochemical properties of the copolymers were investigated at a constant temperature of 70°C by measuring conversion, viscosity, molecular weights, and molecular weight distribution, respectively, by using gravimetric method, Brookfield viscometer, viscometric method, and gel permeation chromatograpy. It was determined that the original copolymer latexes viscosities increased with the increased chain length for the two types of emulsifiers, in general. Similar changes were also found in viscosity average, number average and weight average molecular weights of the copolymers for the different types of emulsifiers. Copyright © 2006 John Wiley & Sons, Ltd.

Semi‐continuous emulsion copolymerization of vinyl acetate and butyl acrylate using a new protective colloid. Part 2. Effects of monomer ratio and initiator

AbstractPoly(vinyl acetate‐co‐butyl acrylate) latexes with N‐methylol acrylamide were prepared by semi‐continuous emulsion polymerization. The influence of the different initiators and various monomer ratios was studied to relate its physicochemical and colloidal properties. The changes in the copolymer latexes with the use of ammonium persulfate and potassium persulfate initiators were investigated by monitoring viscosity, molecular weights, molecular weight distribution and particle size. It was found that almost all physicochemical and colloidal properties of the latexes followed the same trends for both initiators. Potassium persulfate gave slightly higher results for number‐ and weight‐average molecular weights than ammonium persulfate. Copyright © 2006 John Wiley & Sons, Ltd.

The growth of latex particles during the Vac/BA copolymerization

The semi-continuous seeded emulsion copolymerization of vinyl acetate and butyl acrylate was carried out with hydroxyethyl cellulose as a colloid stabilizer. The morphology of the latex particle and the relationship between the reaction time and the average particle diameter and/or the conversion ratio during the polymerization were investigated. The experimental results show that the morphology of the latex particle possesses the stable steric construction. In the seeded polymerization, the average particle diameter of latex decreased while the conversion ratio increased. At the second term of the emulsion copolymerization (the growth stage of particle size), the latex particle average diameter increased with copolymerization continuously, but the instantaneous conversation ratio was not large, so it was very necessary to properly prolong the time during the holding temperature stage.

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

AbstractBatch 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

Semicontinuous Emulsion Copolymerization of Vinyl Acetate and Butyl Acrylate Using Different Initiators and Different Chain Length Emulsifiers

AbstractThe semicontinuous emulsion copolymerization of vinyl acetate and butyl acrylate (VAc/BuA) (85:15) initiated by thermal initiators ammonium persulfate (APS) and potassium persulfate (PPS) at 70°C in the presence of nonylphenol ethoxylates of varying chain lengths (NP‐n) and acrylamide partially polymerized (Amol) was investigated. VAc‐BuA copolymer latexes were synthesized as two different series in the glass reactor, in the first serie was initiated by APS and PPS was used as initiator in the second serie. The influence of the counterions or initiators and chain lenghts of non‐ionic emulsifier on the properties of VAc‐BuA copolymer latexes were determined by measuring Brookfield viscosities, weight average molecular weights (M̄w), number average molecular weights (M̄w), molecular weight distribution and surface tension of latexes to air. The results of copolymer latexes indicated that their physicochemical properties increased with the increasing chain length of nonionic emulsifier for two initiators.