Showing papers on "Vinyl acetate published in 2023"

Detection of microplastics in human saphenous vein tissue using μFTIR: A pilot study

Abstract: Microplastics (MPs) are ubiquitous in the environment, in the human food chain, and have been recently detected in blood and lung tissues. To undertake a pilot analysis of MP contamination in human vein tissue samples with respect to their presence (if any), levels, and characteristics of any particles identified. This study analysed digested human saphenous vein tissue samples (n = 5) using μFTIR spectroscopy (size limitation of 5 μm) to detect and characterise any MPs present. In total, 20 MP particles consisting of five MP polymer types were identified within 4 of the 5 vein tissue samples with an unadjusted average of 29.28 ± 34.88 MP/g of tissue (expressed as 14.99 ± 17.18 MP/g after background subtraction adjustments). Of the MPs detected in vein samples, five polymer types were identified, of irregular shape (90%), with alkyd resin (45%), poly (vinyl propionate/acetate, PVAc (20%) and nylon-ethylene-vinyl acetate, nylon-EVA, tie layer (20%) the most abundant. While the MP levels within tissue samples were not significantly different than those identified within procedural blanks (which represent airborne contamination at time of sampling), they were comprised of different plastic polymer types. The blanks comprised n = 13 MP particles of four MP polymer types with the most abundant being polytetrafluoroethylene (PTFE), then polypropylene (PP), polyethylene terephthalate (PET) and polyfumaronitrile:styrene (FNS), with a mean ± SD of 10.4 ± 9.21, p = 0.293. This study reports the highest level of contamination control and reports unadjusted values alongside different contamination adjustment techniques. This is the first evidence of MP contamination of human vascular tissues. These results support the phenomenon of transport of MPs within human tissues, specifically blood vessels, and this characterisation of types and levels can now inform realistic conditions for laboratory exposure experiments, with the aim of determining vascular health impacts.

Competition between Hydrolysis and Radical Ring-Opening Polymerization of MDO in Water. Who Makes the Race?

Abstract: A major challenge in modern society is the reduction of microplastics created by polymers having stable C–C backbones. The chemistry of radical ring-opening copolymerization of cyclic ketene acetals (CKAs) with vinyl monomers in introducing degradable ester units into the C–C backbone is highly promising. Although the corresponding reaction in an aqueous medium should provide biodegradable primary dispersions, the bottleneck is the hydrolytic instability of CKAs. Therefore, in-depth hydrolysis kinetics of CKA (2-methylene-1,3-dioxepane, MDO) at different pH values and temperatures under homogenous and heterogenous conditions are studied to get a “sweet spot” under which emulsion polymerization of MDO might be possible. Depending on the pH, the hydrolysis of MDO undergoes three different mechanisms with slowed hydrolysis kinetics under alkaline conditions. Besides 4-hydroxy-1-butylacetate (4-HBA), other co-hydrolysis products were detected, leading to the autocatalysis effect. The fast MDO hydrolysis during emulsion copolymerization with vinyl acetate led to the formation of polymers with extremely less incorporation of ring-opened MDO units. Degradation tests of the corresponding emulsion copolymers compared with copolymers prepared in solution confirmed the low incorporation ratio of MDO. The results and discussion presented in this work will be a strong guideline for future emulsion copolymerizations of CKAs.

Direct Radical Copolymerizations of Thioamides To Generate Vinyl Polymers with Degradable Thioether Bonds in the Backbones

Abstract: Direct radical addition reactions of thiocarbonyl (C=S) groups unaccompanied by β-scission have rarely been reported despite their potential for constructing various sulfur-containing compounds. Herein, we report direct radical copolymerizations of the C=S double bonds of simple thioamide derivatives and the C=C double bonds of common vinyl monomers to produce novel degradable vinyl polymers that contain thioether units in the backbones. In particular, N-acylated thioformamides copolymerized smoothly with various vinyl monomers, such as methyl acrylate, vinyl acetate, N,N-dimethylacrylamide, and styrene. RAFT copolymerization was also successfully mediated. The resultant copolymers had high glass transition temperatures and were readily degradable under ambient conditions. This work will expand the potential for use of thiocarbonyl compounds in radical reactions and develop novel poly(thioether)-vinyl polymer hybrid materials with unusual properties.

CO2 solubility and diffusivity in poly(vinyl acetate) studied using the PC-SAFT and free volume theory

Abstract: Poly (vinyl acetate) (PVAc) is a polymer used in various industrial applications, and the quantitative determination of CO2 solubility and diffusion coefficient is important for designing foaming processes involving supercritical CO2. In this study, these two physical properties were obtained experimentally and theoretically using the perturbed chain–statistical associating fluid theory (PC–SAFT) and free volume theory at temperatures between 353 K and 473 K and pressures up to 20 MPa. CO2 solubility increased almost linearly with pressure and could be correlated with the PC–SAFT equation of state and binary interaction parameter kij within the average relative deviation of 2.1%. Furthermore, the fitted plot of kij versus temperature can be used to predict CO2 solubility at lower temperatures. The diffusion coefficient of CO2 in PVAc was experimentally determined from CO2 sorption curves. Its value increased with increasing CO2 solubility and temperature, which was consistent with the free volume theory.

Cp*Co(III)-Catalyzed Regioselective [4 + 2]-Annulation of N-Chlorobenzamides with Vinyl Acetate/Vinyl Ketones.

Abstract: An efficient and straightforward strategy for the synthesis of isoquinolones through [4 + 2]-annulation of N-chlorobenzamides with vinyl acetate in the presence of CoCp*(III) catalyst in a regioselective manner is described. Furthermore, the annulation reaction was diversified by using vinyl ketones. By utilizing this strategy, biologically valuable isoquinolone derivatives were prepared in good yields. Subsequently, isoquinolone derivatives were further transformed into 1-chloroisoquinolines in the presence of POCl3. Furthermore, mechanistic investigations such as deuterium labeling study and competition experiment were performed to support the proposed reaction mechanism.

Formulation of emulsion paint using benign HGSO/PVAc copolymer as a binder

Abstract: This study focused on developing a new copolymer binder from Polyvinyl acetate (PVAc) and Guna seed oil, in which the copolymer binder was used to formulate an emulsion paint. The emulsion paint formulated from the novel copolymer binder of polyvinyl acetate- hydroxylated guna seed oil (PVAc/HGSO) was characterised and compared with paint made from conventional polyvinyl acetate (PVAc) binder. Seed oil from guna was extracted mechanically using cold press method, and the extracted guna seed oil were successively subjected to epoxidation and hydroxylation reaction processes. The hydroxylated guna seed oil (HGSO) was copolymerised with conventional polyvinyl acetate in different ratio of 10 to 70% of hydroxylated oil, to formulate a novel PVAc/HGSO copolymer binder. The physico-chemical properties of the formulated copolymer binder were compared with the standard value acceptable in coating industry inorder to ascertain the better blend ratio that will be suitable for paint production. The better blend copolymer binder was used in production of an emulsion paint. The physico-chemical parameters on the formulated emulsion paint were compared with paint formulated using only PVAc as a binder and acceptable value in the coating industry. The novel formulated emulsion paint found to be increased in gloss, adhesion and flexibility, which are major setback in paint produced using conventional PVAc only as a binder. Therefore, the novel PVAc/HGSO can be used to produce an emulsion paint.

New Functional Polymer Materials via Click Chemistry-Based Modification of Cellulose Acetate

Abstract: Cellulose acetate (CA) was partially acrylated, and the resulting cellulose acetate acrylate (acryl-substitution degree of 0.2) underwent quantitative thio-Michael click reactions with various thiols. A toolbox of functional CA polymers was obtained in this way, and their properties were studied. The modification with fatty alkyl thiols led to hydrophobic materials with large water drop contact angles. Octadecylthio-, butoxycarbonylpropylthio-, and furanylthio-modifications formed highly transparent materials. The new derivative CAASFur disintegrated completely under industrial composting conditions. Films of modified CA polymers were cast and investigated in terms of barrier properties. The nanocomposite of CAAS18 compounded with a synthetic layered silicate (hectorite) of a large aspect ratio showed permeabilities as low as 0.09 g mm m–2 day–1 for water vapor and 0.16 cm3 mm m–2 day–1 atm–1 for oxygen. This portfolio of functional CA polymers opens the door to new applications.

The Application of Two-Phase Catalytic System in Enantioselective Separation of Racemic (R,S)-1-Phenylethanol

Abstract: Kinetic resolution is one of the methods which allows obtaining enantiomerically pure compounds. In the study presented herein, enantioselective biotransformations of (R,S)-1-phenylethanol were performed with the use of various catalytic systems containing ionic liquids and n-heptane or toluene as a reaction medium, vinyl acetate or isopropenyl acetate as an acetylating agent, and lipases from Burkholderia cepacia or Candida rugosa. The conducted studies proved that the use of Burkholderia cepacia lipase, vinyl acetate, and n-heptane with [EMIM][BF4] allows obtaining enantiomerically pure 1-phenylethyl acetate, with the enantiomeric excess of products eep = 98.9%, conversion c = 40.1%, and high value of enantioselectivity E > 200. Additionally, the use of ionic liquids allowed us to reuse enzyme in 5 reaction cycles, ensuring the high operational stability of the protein.

Thermal runaway evaluation on batch polyvinyl acetate emulsion polymerization from calorimetric measurement

Abstract: Emulsion polymerization is the most applied method in the vinyl acetate monomer (VAM)–polyvinyl acetate (PVAc) process. However, the flammable property and unexpected bulk polymerization for the reactant and product may occur in the batch reactor or storage tank. VAM is reactive enough to decompose readily into free radicals and then, initiate the polymerization, which may contribute to heat accumulation due to the monomer, initiator, and solvent mixtures. This study attempts to analyze the exothermic reaction and compare the thermal runaway potential for various VAM solutions during PVAc polymerizations. Summarily, 50%, 70%, and 100% of VAM solutions reacting with 2,2’–azobis(2-methylpropionitrile) readily increase the self-heating rate with their concentration from adiabatic calorimetric tests. Furthermore, kinetic parameters of 50, 70, and 100 mass% VAM solutions were evaluated to elucidate the self-heating model associated with thermal analysis and to determine heat production mechanisms that are practical to proactive safety protocol for the PVAc emulsion process.

Microwave Foaming of Ethylene Vinyl Acetate Copolymer: Foam Cell Characterization and Acoustic Properties Evaluation

Abstract: This study aimed to characterize cell morphology and sound absorption properties of ethylene vinyl acetate (EVA) foam produced by microwave heating. EVA was compounded with pre-determined amount of azodicarbonamide as the blowing agent, dicumyl peroxide used as the crosslinking agent and zinc oxide for the blowing agent activation. Foaming was done by microwave heating at different duration and by sequential heating with microwave heating was coupled with convection heating. The result revealed that foam cell size increased with heating time, but cell wall thickness did not record a linear reduction. All the foams produced with microwave heating only have sufficiently good sound absorption coefficient at low frequency range. Foam produced with sequential heating had the largest cell size and the thinnest cell wall which was transpired by having the highest sound absorption coefficient. This was due to the existence of higher open-cell structure resulted from the rupture of thin cell walls observed in the foam morphology. The variation in processing sequence was proven to be a significant factor in determining foam cell structure and subsequently their corresponding acoustic properties.

Preparation of guar gum-g-poly (vinyl acetate-co-hydroxyethyl methacrylate) anti-leakage material and its performance study

Abstract: Salinization of land and water scarcity is the global environmental issues, and their management in the early stages can help to prevent the loss of fertile soil and increasing desertification. Here a cost-effective emulsion with good water retention and salt isolation performance was prepared by free radical emulsion polymerization of vinyl acetate (VAc) and hydroxyethyl methacrylate (HEMA) onto guar gum (GG) substrate GG-g-P(VAc-co-HEMA). The emulsion was characterized using conventional methods and the reaction conditions were optimized for maximum viscosity. The performance (stability, water retention, anti-leakage and salt isolation) of the optimized emulsion was evaluated in lateritic soil. The results showed that, compared with the untreated soil, the antileakage and salt isolation performance of the emulsion treated laterite soil increased by ∼ 64.7 % and ∼ 22 % respectively. The GG-g-P(VAc-co-HEMA) emulsion has good prospects for water harvesting and water conservation in arid and semi-arid areas and water resource regulation, as well as saline-alkali soil improvement for sustainable agriculture.

Low Temperature, In Situ Polymerization of Vinyl Acetate in Silica Containing Emulsion Gels

Abstract: Vinyl acetate (VAc) was polymerized to about 90% conversion in 9 h at 40°C from the colloidal microstructure of the VAc/fumed silica/cetyltrimethylammonium bromide (CTAB) system. The glass transition ( $T_g$ ) of poly(vinyl acetate) (PVAc) polymerized in these emulsion gels with silica was higher ( $T_g={41}^{°}\text{C}$ ) than those of PVAc made from bulk polymerization at 60°C ( $T_g={31}^{°}\text{C}$ ) and the weight average molar mass ( $M_w$ ) was also larger ( $M_w$ about 300 kg/mol) than those from bulk polymerization ( $M_w=125\text{kg}/\text{mol}$ ). Increased $M_w$ , $T_g$ , and lowered processing temperature for these composites could facilitate new applications for PVAc.

Influence of solvent quality on the swelling and deswelling and the shear modulus of semi-dilute solution cross-linked poly(vinyl acetate) gels.

Abstract: We systematically examine the influence of varying temperature (T) over a large range in model poly(vinyl acetate) gels swollen in isopropyl alcohol. The theta temperature Θ, at which the second virial coefficient A2 vanishes, is found to be equal to within numerical uncertainty to the corresponding high molecular mass polymer solution value without cross-links, and we quantify the swelling and deswelling of our model gels relative to their size at T = Θ, as customary for individual flexible polymer chains in solutions. We also quantify the "solvent quality" dependence of the shear modulus G relative to G(T = Θ) and compare to the gel swelling factor, α. We find that all our network swelling and deswelling data can be reduced to a scaling equation of the same general form as derived from renormalization group theory for flexible linear polymer chains in solutions so that it is not necessary to invoke either the Flory-Huggins mean field theory or the Flory-Rehner hypothesis that the elastic and mixing contributions to the free energy of network swelling are separable to describe our data. We also find that changes of G relative to G(T = Θ) are directly related to α. At the same time, we find that classical rubber elasticity theory describes many aspects of these semi-dilute solution cross-linked networks, regardless of the solvent quality, although the prefactor clearly reflects the existence of network defects whose concentration depends on the initial polymer concentration of the polymer solution from which the networks were synthesized.

Liquid Foam-Ethyl Vinyl Acetate Adhesive Systems for Lining Process of Paintings: Prospects of a User-Friendly, Harmless Alternative to Conventional Products

Abstract: The lining of paintings is a process of conservation science and art restoration used to strengthen, flatten, or consolidate paintings on canvas by attaching by means of adhesives a second canvas to the back of the existing one. To this aim, the prospects of the use of ethyl vinyl acetate (EVA) resins in aqueous dispersion applied as an adhesive in a foam form have been investigated in the present study. The key physical properties of the foam have been investigated, with a deep focus on rheological behavior and the drying rate, comparing the results with those obtained using the liquid products that are commercially available. Dedicated mock-ups have been prepared to test the adhesive for the lining process, inspecting adhesion strength, colorimetric properties, and the influence on the possible chromatic and visual alteration of the surface, also looking at the chemical interaction with painting materials and the deterioration after an artificial ageing process. The results obtained clearly indicated that the proposed technology is very suitable for the targeted application, and an EVA water-based foamed dispersion can be used for paintings’ lining, in view of the ease of application, being an appropriate adhesion, no chemical interaction, nor the deterioration of the painting.

Preparation and Characterization of Cellulose Nanoparticles from Agricultural Wastes and Their Application in Polymer Composites

Abstract: , Page no - | ABSTRACT | PDF | FULL TEXT | e-PUB Background: The development of innovative eco-sustainable bio-nano-composites materials based on cellulose nanomaterials obtained from agricultural waste such as rapeseed plant straw and polymeric materials with improved properties. At first, cellulose was extracted from rapeseed plant straw and cellulosic and no cellulosic materials were estimated. It was found that the rapeseed plant straw contained about 43.48 wt.% cellulosic materials and 56.52 wt.% no cellulosic materials. It was also found that the rapeseed plant straw content about 34.84 wt.% α- cellulose. Then, nano-cellulose was prepared by acid hydrolysis of α -cellulose obtained from rapeseed plant straw. Poly vinyl acetate (PVAc) was prepared by soap free emulsion polymerization of vinyl monomer. Natural rubber (NR) collected as latex was oxidized by KMnO4. Blends of NR and oxidized NR with PVAc of different compositions such as NR60/PVAc40, NR40/PVAc60, ONR60/PVAc40, ONR40/PVAc60 were prepared by mixing NR latex and PVAc emulsion and followed by drying in an oven at 60°C. Composites of NR60/PVAc40 and ONR60/PVAc40 reinforced nano-cellulose (NC) were also prepared in similar way. The blends and composites were then characterized by FTIR, SEM, and Tensile test (TS). FTIR analysis confirmed the oxidation of NR and shown the variation of the functional groups in the blends and composites compared with the FTIR spectrum of NR, ONR and PVAc. SEM study exhibited that the nano-cellulose were dispersed within NR/PVAc and ONR/PVAc blends matrices with a little agglomeration. The tensile test results showed that the strength in composites was increased due to the reinforcing effect of nano-cellulose (NC). Objectives: The aim of this study is to assess the Preparation and characterization of binary blends of NR and oxidized NR with PVAc. Methods: This is an observational study. The study used to be carried out in the admitted patient’s Department of Applied Chemistry and Chemical Engineering, Islamic University, Kushtia-7003, Bangladesh. The duration of the period from Data was entered in MS Excel and Statistical analysis was done using SPSS trial version. Results: This study shows that the according to Constituent, Cellulose was 43.4822%, Alpha-Cellulose were 34.8427% and Cellulose were 8.6395%. And according to Source, Rice Straw were 32.15% %, Sugarcane were 41-43%, Rye Straw were 31.8-42.64%, Corn Stalks were 29.80% and Wheat Straw were 34-40%. Conclusion: Novel eco-friendly bio-nano-composites substances primarily based on renewable and sustainable assets namely natural rubber (NR) and nano-cellulose received from rapeseed plant straw as properly as poly vinyl acetate (PVAc) have been developed. In order to enhance the interfacial interactions amongst the composite factors such as NR, PVAc and NC, oxidation of the NR latex was once carried out by way of KMnO4 before blending mixing with PVAc emulsion and NC suspension.