Polymerization Of Vinyl Acetate Research Articles

Molecular Dynamics Simulation of the Viscosity Enhancement Mechanism of P-n Series Vinyl Acetate Polymer–CO2

Carbon dioxide (CO2) drive is one of the effective methods to develop old oil fields with high water content for tertiary oil recovery and to improve the recovery rate. However, due to the low viscosity of pure CO2, it is not conducive to expanding the wave volume of the mixed phase, which leads to difficulty utilizing the residual oil in vertical distribution and a low degree of recovery in the reservoir. By introducing viscosity enhancers, it is possible to reduce the two-phase fluidity ratio, expanding the degree of longitudinal rippling and oil recovery efficiency. It has been proven that the acetate scCO2 tackifier PVE can effectively tackify CO2 systems. However, little research has been reported on the microscopic viscosity enhancement mechanism of scCO2 viscosity enhancers. To investigate the influence of a vinyl acetate (VAc) functional unit on the viscosity enhancement effect of the CO2 system, PVE (Polymer–Viscosity–Enhance, P-3) was used as the parent, the proportion of VAc was changed, and the molecules P-1 and P-2 were designed to establish a molecular dynamics simulation model for the P-n-CO2 system. The molecules in the system under the conditions of 70 °C-10 MPa, 80 °C-10 MPa, and 70 °C-20 MPa were simulated; the viscosity of the system was calculated; and the error between the theoretical and simulated values of the viscosity in the CO2 system was relatively small. The difference between P-n molecular structure and system viscosity was analyzed at multiple scales through polymer molecular dynamics simulations and used the molecular radial distribution function, system density, accessible surface area, radius of gyration, minimum intermolecular distance, and minimum number of intermolecular contacts as indicators. This study aimed to elucidate the viscosity enhancement mechanism, and the results showed that the higher the proportion of VAc introduced into the molecules of P-n-scCO2 viscosities, the larger the molecular amplitude, the larger the effective contact area, and the greater the viscosity of the system. Improvement in the contact efficiency between the ester group on the P-n molecule and CO2 promotes the onset of solvation behavior. This study on the microscopic mechanism of scCO2 tackifiers provides a theoretical approach for the design of new CO2 tackifiers.

Synthesis of Well-Defined Poly(vinyl alcohol-co-vinyl acetate) Copolymers by Alcoholysis of Poly(vinyl acetate) Synthesized by Macromolecular Design via Interchange of Xanthate Polymerization, and Their Use as a Stabilizer in Emulsion (Co)polymerization of Vinyl Acetate.

This work aims at synthesizing tailor-made poly(vinyl alcohol-co-vinyl acetate) (PVA) amphiphilic copolymers, obtained by alcoholysis of poly(vinyl acetate) (PVAc) that could display improved properties as stabilizers compared to commercially available PVAs. Well-defined PVAs with different alcoholysis degrees were produced from a library of PVAc homopolymers synthesized by macromolecular design via interchange of xanthate polymerization and exhibiting different degrees of polymerization degrees. Subsequently, these PVAs were evaluated as stabilizers in the emulsion copolymerization of VAc and vinyl neodecanoate (VERSA 10, referred to as V10) and compared to a commercially available reference PVA obtained by alcoholysis of PVAc formed by conventional radical polymerization. In all cases, stable latexes were obtained and compared in terms of their colloidal characteristics. To identify the best stabilizer candidate, the amount of PVA remaining in water and not participating to the particle stabilization was evaluated in each case.

Thermal, rheological, and aging characterization of ethylene vinyl acetate polymer modified asphalt binder

Thermal, rheological, and aging characterization of ethylene vinyl acetate polymer modified asphalt binder

Enhancement of porous asphalt mixtures modified with various fibers and ethylene–vinyl acetate polymer

Porous asphalt mixture is conventional hot mix asphalt (HMA) with substantially decreased fines, which produces an open-graded mixture that enables the water to flow through an interconnected void space. Porous asphalt is a permeable system that has a lot of benefits. However, because of its open structure, the durability of this mixture decreases, and both its stability and resilient modulus are much lower compared to the dense conventional asphalt mixtures. Also, the high void percentage may lead to an increase in the draindown proportion. Fibers (cellulose or mineral) and polymer-modified binders are recommended for porous asphalt mixtures, especially in hot and moderate climates. The objective of this study is to improve the porous asphalt mixture's performance by using ethylene–vinyl acetate (EVA) polymer-modified bitumen. Two types of fibers (cellulose fibers and glass wool fibers) were used, separately to determine the control mixture. Four different proportions of EVA polymer were added to the bitumen (1%, 2%, 3%, and 4%) and Scanning Electron Microscopy (SEM) was used for better investigating of the bitumen microstructure, then The Marshall mix design was used to determine the optimum EVA content (OEC) for the porous asphalt mixture. Several performance tests were conducted to investigate the characteristics of the porous asphalt mixture, such as the infiltration rate, binder draindown, the wheel track and the cantabro abrasion tests. The findings of the study conclude that the addition of EVA polymer to the porous asphalt mixtures enhances the performance as it increases stability by 20.8% and the infiltration rate by 20.6%. It decreases binder draindown proportion by 33.3%, cantabro abrasion loss by 25.1% and the rut depth at 5,000 cycles and 10,000 cycles by 29.8% and 19.7%, respectively.

Synthesis and self-assembly of poly(4-vinylphenol)-b-poly(vinyl alcohol) diblock copolymer for invertible core-shell nanoparticles

We report the synthesis of the amphiphilic diblock copolymer, poly (vinyl phenol)-block-poly (vinyl alcohol), and its reversible formation of invertible core-shell nanoparticles. The diblock copolymer composed of poly (4-vinylphenol) (P4VPh) and poly (vinyl alcohol) (PVA) was prepared by the switchable reversible addition-fragmentation chain transfer polymerization (switchable-RAFT) of 4-acetoxystyrene and vinyl acetate and subsequent acetyl deprotection. The diblock copolymer was soluble in dimethyl sulfoxide (DMSO) but self-assembled into core-shell nanoparticles with the addition of H2O or tetrahydrofuran (THF). The formation and transition of the invertible core-shell system in response to solvent composition was characterized by 1H NMR, dynamic light scattering, and transmission electron microscopy. Interestingly, the fluorescent behavior of the P4VPh block was changed according to the morphological change of core-shell nanoparticle induced by solvent composition. With increasing the H2O content, the P4VPh chains in the DMSO solution collapsed and the diblock copolymers self-assembled to core-shell type micelles. Aggregation of P4VPh chains increased the local concentration of the phenolic group, resulting in fluorescence quenching. However, with the addition of THF to the DMSO solution, the inverted core-shell nanoparticles were formed where segregated P4VPh chains showed fluorescence.

Biodegradable Alkali-Swellable Emulsion Polymers: Industrial and Commercial Thickeners.

Sustainability and circularity are key issues facing the global polymer industry. The search for biodegradable and environmentally-friendly polymers that can replace conventional materials is a difficult challenge that has been met with limited success. Alternatives must be cost-effective, scalable, and provide equivalent performance. We report that latexes made by the conventional emulsion polymerization of vinyl acetate and functional vinyl ester monomers are efficient thickeners for consumer products and biodegrade in wastewater. This approach uses readily-available starting materials and polymerization is carried out in water at room temperature, in one pot, and generates negligible waste. Moreover, the knowledge that poly(vinyl ester)s are biodegradable will lead to the design of new green polymer materials.

Effect of sodium 2‐acrylamido‐2‐methylpropanesulfonate on the structure and properties of thermoplastic polyvinyl alcohol copolymers

AbstractThermoplastic poly(vinyl alcohol) (PVA) with water‐soluble behavior has received great attention. In this work, a thermoplastic PVA was prepared via solution radical polymerization of vinyl acetate, vinyl pivalate and sodium 2‐acrylamido‐2‐methyl propane sulfonate (SAMPS). The effects of SAMPS content on the structure and properties of modified poly(vinyl alcohol) (MPVA) were investigated. On increasing the proportion of SAMPS, the characteristic band of –OH moved to a larger wavenumber. Compared to PVA, the melting temperature (Tm) of MPVA decreased from 223.1 to 161.5 °C at 0.03 mol of SAMPS, and the initial thermal decomposition temperature (Td) of MPVA increased from 244.3 to 262.2 °C at 0.05 mol of SAMPS. The crystallinity of the resin reduced from 51.46% to 10.21%. The enlarged difference between Td and Tm ensured the preparation of MPVA by thermal processing. The maximum tensile strength and elastic modulus of the obtained sheets were 137.56 and 2639.32 MPa, respectively. The introduction of SAMPS reduced the alcoholysis degree from 99.03% to 95.80%. The high alcoholysis degree of MPVA meant that it could be dissolved in water at 60 °C. This type of thermoplastic PVA shows a promising application on film and textiles that require water solubility. © 2024 Society of Chemical Industry.

Modeling of suspension polymerizations in continuous oscillatory baffled reactors (COBR) - Part I: Vinyl acetate polymerization

In this work, a phenomenological model to represent suspension polymerizations in a continuous oscillatory baffled reactor is presented for the first time. The reactor is described as a series of tanks of equal volume connected. Additionally, a backflow stream is also included to simulate a backmixing mechanism. The proposed model considers mass, energy, statistical moments balances and regulatory control loops. Furthermore, the heat transfer coefficient is modeled as a function of the oscillatory conditions and the properties of the suspension. The model predictions are compared with available experimental data and good agreement is observed. The effects of key model parameters on model responses are also investigated. It is shown that initiator type and injection points must be carefully planned to avoid excessive temperature gradients along the reactor length. Given the thorough description of kinetic and heat transfer phenomena, the model can be used for reactor design and process scale up.

Formulation of Emulsion Paint Derived from Waste Expanded Polystyrene as a Binder

Emulsion paint, also known as water-based paint, is a type of paint that consists of small water droplets suspended in a binder. The binder, typically made of acrylic or vinyl acetate polymers, acts as a film-forming agent that holds the pigments and other additives together. Emulsion paint was formulated from waste expanded polystyrene as a binder. The formulated emulsion paint which underwent a three-staged process had a pH of 7.82, density of 1.31 g/cm3, the drying time was 15-20 and 85-90 minutes for the set to touch and set to hard drying times respectively, viscosity of 10.4 Cp. The formulated paint exhibited good adhesion, tackiness, opacity, flexibility and stability properties. The paint also possessed good resistance to blistering; which indicates that it has good external exposure resistance and thus; can perform well when exposed to environmental conditions such as rain and sun. Effects of concentration on viscosity, density, melting point, refractive index, moisture uptake, turbidity, elongation at break and water solubility were studied for the polystyrene binder to ascertain for its suitability. Fourier transform infrared spectrophotometer was employed to characterized the binder. This investigation revealed favourable properties of a conventional emulsion paint inherent in the formulated polystyrene binder derived emulsion paint such as, drying time, moisture uptake, water solubility.

Revealing the mechanism of polymer inhibition of 2,4-dichlorophenoxyacetic acid Polymorphs phase transition by experimental and molecular dynamics simulation

It is well-established that the occurrence of solution-mediated phase transformation makes the precise preparation of pure metastable forms of drugs by solution crystallization methods extremely challenging. This paper demonstrates that the polyvinylpyrrolidone (PVP) and N-vinyl-2-pyrrolidone and vinylacetate (PVPVA) polymers can effectively prevent crystal form transformation of the 2,4-dichlorophenoxyacetic acid (2,4-D) in the solution. We performed the induction time and crystal growth rate experiments at different supersaturation levels. The results showed that the polymer additives can significantly prolong the induction time and have an inhibition effect on crystal nucleation. The PVP and PVPVA almost completely inhibited the crystal growth in both the length and width directions. Molecular dynamics simulations reveal that the interaction energy between the polymer and crystal face determines the magnitude of the inhibition effect on the crystal growth of stable polymorph Form I. These results suggest that polymorph control during the solution crystallization process can be achieved by adding polymer additives.

Investigating the potential of degradable poly(vinyl acetate) copolymer microparticles for encapsulation and in vitro release studies

Poly(vinyl acetate) is a well-known polymer synthesized through the free radical polymerization of vinyl acetate (VAc) monomer. However, enhancing the degradability of this polymer is best achieved by copolymerizing cyclic ketene acetal (CKA) with VAc. Despite their potential, the practical use of these degradable polymers remains limited. Therefore, our study aimed to develop a sustainable technology encompassing the synthesis and application of poly(VAc-co-MDO), and environmental biodegradability of poly(vinyl alcohol (VA)). To achieve this, we synthesized a series of degradable copolymers, namely poly(VAc-co-MDO), via free radical ring-opening polymerization (rROP) of 2-methylene-1,3-dioxepane (MDO) with VAc. The number of degradable ester units in the polymer backbone was systematically controlled by varying the initial monomer feed compositions, resulting in a range of 8–85 mol%. To compare their properties, we also synthesized homopolymers, namely poly(VAc) and poly(MDO). Subsequently, we formulated the homo and copolymers into microparticles using the co-solvent evaporation method, which yielded spherical particles with a particle size distribution ranging from 5 to 10 µm. Furthermore, we demonstrated the applicability of these degradable copolymers, exemplified by a poly[VAc(0.92)-co-MDO(0.08)] with 8 mol% MDO in the polymer backbone, in an encapsulation modeling study using curcumin as the active molecule. Successful encapsulation of curcumin into degradable polymer particles was confirmed and quantified via HPLC analysis. The degradability of the copolymers was evaluated through accelerated alkali hydrolysis, resulting in the formation of oligomeric degradation products. Additionally, we investigated the environmental biodegradability of poly(VA-co-MDO) as a proof of concept, revealing a biodegradability of 89% within 28 days for this polymer consisting of 88 mol% poly(VA) and 12 mol% poly(MDO) in the backbone. Preparing stable formulation for applications and performing biodegradability tests for the copolymers or microparticles derived from random poly(VAc-co-MDO) was challenging due to the insolubility of the polymer or instability in the form of sedimentation of the microparticles in the inoculum. Hence, in order to achieve stable formulation, we synthesized random poly(VA-co-MDO) through the selective cleavage of chloroacetyl group (ClAc) from its precursor, poly(VClAc-co-MDO). This method was preferred because obtaining poly(VA-co-MDO) directly from poly(VAc-co-MDO) was hindered by significant ester backbone cleavage, even under mild conditions. Our research assumes significance in light of recent restrictions imposed by various chemical agencies on the use of non-degradable polymers and microparticles in formulations.

Monitoring Polymeric Fouling in a Continuous Reactor by Electrochemical Impedance Spectroscopy

AbstractMonitoring early stages of polymeric deposit formation and its prevention were studied by in‐situ electrochemical impedance spectroscopy (EIS) in a continuously operating reactor employed for polymer production. An EIS flow cell was designed and employed during the emulsion polymerization of vinyl acetate. The electrochemical analysis of the complex impedance at the solution/reactor interface allows the time‐resolved detection of film formation processes. In comparison to oxide‐covered stainless steel, an anti‐adhesive sol‐gel coated alloy showed a significant inhibition of poly(vinyl acetate) fouling. The EIS‐based approach proved to be a valuable tool for monitoring both thin barrier film performance and fouling processes under harsh process conditions.

Experimental analysis of tribological performance of base ficus carica vegetable oil with different polymers as additives using four ball tribometer

The need to use vegetable lubricants has been driven by the widespread concern for environmental issues, especially in industries that overuse petroleum lubricants. This research examined the tribological characteristics of vegetable-based lubricants by adding additives such as ethylene–vinyl acetate (EVA) and Eichhornia crassipes carboxymethyl cellulose (EC-CMC) polymers to study the viscometric response of the lubricants. The test was conducted using four ball-tester, and analyzed in terms of coefficient of friction (COF), wear scar diameter (WSD), and wear scar rate, respectively. The results showed that with the addition of each additive enhanced the tribological properties significantly but yielded poor results with 0.5% additives for both samples. The characterization investigation showed that ficus carica (Fig) oil responded effectively to the addition of various additives when conducted thermogravimetric analysis (TGA) and Fourier transform infrared (FT-IR) spectroscopy. Under 100 kg load and speed of 1200 rpm, base Fig lubricant yielded a higher COF of 0.193, while blended EVA and EC-CMC gave lower COF of 0.161 and 0.171, while the lowest wear scar diameter was with 1.5 wt% EVA (0.39 mm) and 1 wt% EVA (0.41 mm), respectively. Comparing all the lubricants under 1500 rpm, the base Fig lubricant yielded 0.317, while 1.5 wt% EVA, 1.5 wt% EC-CMC, SEA 5W 30 gives COF of 0.287, 0.263, and 0.239, respectively. The study revealed that the reduction in the COF and wear scar diameter was due to the formation of the film by the included additive.

Hybrid electrochromic device with transparent electrolyte

Hybrid electrochromic (EC) devices present an interesting configuration in which the advantage of both solid-state and liquid-based devices can be combined in order to optimize the device performances. In this configuration, a solid-state EC material is combined with a redox couple dissolved in the electrolyte. The redox electrolyte offers an unlimited charge capacity, thus allowing to fully exploit the electrochromic properties of the EC material. Here, we present a thiolate/disulphide (T−/T2) redox couple as a new redox shuttle for EC devices. In order to transfer the advantages of the redox couple to a solid state device, it was combined with a fully transparent thermally curable vinyl-acetate polymer. The obtained EC device was compared with that based on I−/I3− showing higher transparency in the visible region of the solar spectrum and higher coloration efficiency. Most interestingly, the device based on T−/T2 shows a slower self-bleaching process and it only loses 30% of its coloration after 1 h at open circuit. Such characteristic represents a great advantage for smart windows applications since it is not necessary to apply potential to maintain the device coloration, thus allowing a great energy saving.

Nano-clays as rheology modifiers in intumescent coatings for steel building structures

The study focuses on evaluating the influence of bentonite nano-clays on the rheological profile of intumescent fire-retardant compositions and determining optimal structures and quantities of clay thixotropic additives to increase the single-layer thickness of intumescent paint during application.The influence of hydrophobic organomodified, and hydrophilic activated, nano-clays on the rheology of intumescent fire-retardant systems was investigated by determining dynamic viscosity using a Brookfield viscometer at shear rates 2.09 s-1 to 52.25 s-1 followed by mathematical modeling using Casson equation. Addition of hydrophobic organomodified bentonites with intercalated quaternary ammonium cations at 1 wt.% increases thixotropy of both solvent-based and water-based systems by 5–12 times. Hydrophilic clays positively effects the rheology of water-based systems (4–6 times increase in thixotropic effects) and have no effect on solvent-based systems (0,8–1,5 times). Based on extensive experimental data and theoretical calculations, the optimal approximate dynamic viscosity was determined for solvent-based systems (10–7 Pa × s, spindle N6, 20–50 rpm, 20 °С), and water-based systems (17–8 Pa × s, spindle N7, 20–50 rpm, 20 °С). They can be used as markers for industrially produced intumescent paints, to ensure the absence of sedimentation and provide adequate sag resistance when the paint is applied with 1.5 mm single-layer thickness.Laboratory fire tests, and the assessment of thermal expansion of intumescent systems with and without nano-clays, demonstrate that vinyl acetate polymers in intumescent coatings are more suitable for providing higher (60 min or more) levels of fire resistance to steel structures than styrene acrylates. When developing formulations of water-based fire-retardant coatings, capable of providing fire resistance of R120 and higher, the addition of 2–3 wt.% of nano-clays can ensure the formation of a strong and durable thermo-insulating charred layer.

Thermal behaviors of ethylene vinyl acetate encapsulants in fielded silicon photovoltaic modules

AbstractAging of silicon photovoltaic (PV) module packaging is one of the greatest limiters of PV module service lifetimes. Module characterization typically focuses on power degradation metrics, which do not convey the complexities of often simultaneous degradation mechanisms. In this work, PV modules with pristine references and known fielding histories were investigated by non‐destructive and destructive methods. Modules from Canadian Solar, Mission Solar, and Hanwha Q‐Cells were fielded for up to three years; select modules were removed from fielding each year for coring to allow for characterization of the encapsulant. Modules are commonly encapsulated with two protective layers of partially‐crystalline ethylene vinyl acetate (EVA) polymer that must undergo a crosslinking reaction to achieve desired properties. The extent of crystallinity of the encapsulants as studied by differential scanning calorimetry showed differences between manufacturers and over time. Some encapsulants showed different magnitudes of crystal sizes which changed after fielding; encapsulants with the monodisperse crystal sizes did not change with fielding. This is due to differences in thermal history. These results have implications for stress development during module aging, since EVA crystal melting and crosslinking reactions can result in encapsulant density changes.

EVA/PZT‐Composite‐Based Triboelectric Nanogenerator for Energy Harvesting

The development of triboelectric nanogenerators (TENGs) has experienced rapid advancement in the past decade. In the present study, ethylene vinyl acetate (EVA) polymer and lead zirconium titanate (PZT) are taken as the host materials. The EVA–PZT elastomer composites are fabricated using different weight percentages (2.5%, 5.0%, 7.5%, and 10.0%) of PZT in EVA by solvent casting. The X‐ray diffraction investigation of these films reveals the presence of the PZT material and the formation of composites. TENGs have the potential to revolutionize energy harvesting and provide a sustainable energy source for a variety of applications. The electrical output performance of the single‐electrode‐mode‐based TENG is examined. The maximum output of 60 V and 165 nA is produced by the EVA–PZT 7.5 wt%/Al‐based TENG device. Further, TENG is used to power devices and gather biomechanical energy.

PENGARUH SUDUT PAHAT PADA PENGGURDIAN KOMPOSIT SERAT DAUN NANAS / TERMOPLASTIK PADA PEMBENTUKAN DELAMINASI

This study aims to determine the effect of the Gurdi tool angle on delamination in composite laminates in the formation of delaminations. The spacing of the selected reinforcing fibers was 2.4 and 6 mm in a composite laminate of ethylene vinyl acetate (EVA) polymer matrix with reinforcing fibers from pineapple leaves. The method used in composite fabrication is hand lay-up, namely by direct casting on three layers of fiber that has been woven and tied to the sides of the mold. For cutting speed, Vf 72 mm / min, using a chisel with a diameter of 8 mm with a tool angle of 70o and 118o. Delamination was determined using the Feda method. The delamination sections were observed using a digital microscope and then processed using AutoCAD to measure Dmax and Ad. The delamination ratio in the top hole for the tool diameter of 8mm with a 70° angle at the variation of the distance of 2 mm, 4 mm and 6 mm were 1.268, 1.224 and 1.192 for the bottom hole were 1.078, 1.042 and 1.029, respectively. Meanwhile, the ratio of delamination in the upper hole for a tool diameter of 8mm with an angle of 118° at a distance variation of 2mm, 4mm and 6mm were 1.194, 1.194, 1.158 for the bottom hole, respectively, 1.046, 1.042 and 1.038.

Formulation and process determined fouling prediction for the continuous emulsion co polymerisation of vinyl acetate

Fouling is challenging for the industrial implementation of continuous emulsion polymerisations. A requirement for the development of successful anti-fouling concepts is an in-depth understanding of the processes involved in fouling and the knowledge of the main influencing factors. In this work, an experiment-based strategy was developed for the quantification of fouling trends and in order to calculate the expected fouling intensities during the continuous emulsion polymerisation of vinyl acetate copolymers. These, then, can be correlated with the direct process parameters temperature, initiator and emulsifier content and comonomer ratio. The expected fouling tendency for formulations could be determined in the investigated range with an accuracy of ± 15% referred to experimental validations.

Vinyl acetate polymers modified by siloxane for improving reinforced concrete: Water proofness and anticorrosion

Concrete, which is commonly destroyed by erosion in adverse environments, cannot satisfy the demands of foundation construction engineering applications. The optimal wayto ensure concrete's durability is to cover its surface with a barrier coating that prevents potentially harmful particles from penetrating the inside. Vinyl acetate polymers were applied as coatings owing to excellent flexibility and strong adhesion to the substrate. However, their hydrophilicity and low hardness will inevitably limit the usage in various areas, in particular the construction materials field. In this study, a method of modifying vinyl acetate polymers (PVAc) by vinyl triethoxysilane (VTES) and vinyl neononanoate (VeoVa-9), vinyl neodecanoate (VeoVa-10) in tertiary vinyl carbonates was reported to enhance the anticorrosion of concrete, where the former VTES could act a coupling agent, while the latter tertiary vinyl carbonates provide shielding against invasion through steric effect. Following modification, the hydrophilic PVAc becomes a hydrophobic coating with a contact angle as high as 98°; the coating's water absorption rate in one week is merely 1.25%; higher hardness and modulus were validated by nanoindentation measurements, while sandpaper friction and lap-shear trial indicated an enhancement in wear resistance and adhesion; three-electrode electrochemical analysis revealed that the modified coating has a 98% anti-corrosion efficacy, and its excellent anticorrosion performance is further confirmed by 480-hour salt spray test on reinforced concrete models.