Polyvinyl alcohol stability

Chem. Descrip. EVA copolymer emulsion, polyvinyl alcohol stabilized, non-crosslinking CAS24937-7 fl... 

Chem. Descrip. Ethylene/vinyl laurate/vinyl chloride terpolymer with polyvinyl alcohol stabilizer and mineral filler antiblocking agent Uses Binder, water repellent in conjunction with inorg. binders in plasters. Joint mortars, troweling compds., tile and construction adhesives, adhesives for external insulation and finishing systems sole binder in plasters, paints, adhesives modifier, adhesion promoter, plasticizer, impact resist, aid for gypsum and anhydrite Features Imparts hydrophobic props. enhances adhesion, flex, str., plasticity, abrasion resist., and workability contains no soivs., plasticizers, of film-forming aids... 

Free flow. Dobry and Finn [Chem. Eng. Prog., 54, 59 (1958)] used upward flow, stabilized by adding methyl cellulose, polyvinyl alcohol, or dextran to the background solution. Upward flow was also used in the electrode compartments, with cooling efficiency sufficient to keep the main solution within 1°C of entering temperature. 

Neoprene latex 115 contains a copolymer of chloroprene and methacrylic acid, stabilized with polyvinyl alcohol [15], With respect to other polychloroprene latices, this latex has two major advantages (1) excellent colloidal stability, which gives high resistance to shear and a broad tolerance to several materials ... 

Other components in PVAc-formulations are defoamers, stabilizers, filler dispersants, preservatives, thickeners (hydroxyethylcellulose, carboxymethylcellu-lose), polyvinyl alcohols, starch, wetting agents, tackifiers, solvents (alcoholes, ketone, esters), flame retardants and others. 

Individual components in the formulation of the aqueous phase all contribute to the successful production of a GPC/SEC gel. The stabilizer acts as a protective coating to prevent the agglomeration of the monomer droplets. Polyvinyl alcohol, gelatin, polyacrylic acids, methylcellulose, and hydroxypro-... 

In suspension polymerization, the monomer gets dispersed in a liquid, such as water. Mechanical agitation keeps the monomer dispersed. Initiators should be soluble in the monomer. Stabilizers, such as talc or polyvinyl alcohol, prevent polymer chains from adhering to each other and keep the monomer dispersed in the liquid medium. The final polymer appears in a granular form. 

Gratzel and co-workersfound that the 600 nm absorption of MV is built up after the laser flash. The colloid was stabilized by polyvinyl alcohol. The laser flash produced a large number of electrons in each colloidal particle. The build-up followed a first order rate law, the rate constant being proportional to the MV concentration, and the final amount of MV formed also increased with the MV concentration. Figure 23 shows the final MV concentration as a function of the pH of the solution. Below pH = 2, MV is not reduced. The electron transfer from the colloidal particles proceeds until electrochemical equilibrium is reached between the Ti02 particles and the MV /MV system in solution. At low pH values thisequilib-... 

With increasing pH the reaction became less complete as the reverse reaction + TiOj MV + Ti02 became more important. A potential of the conduction band of the TiOj particles of —0.1 to —0.2 V (pH = 0) was derived from these measurements. Stabilization of the particles by polyvinyl alcohol did not change this potential. Particles of 80 nm diameter had the same potential as particles of 7 nm. 

Colloids of a-FejOj are made by hydrolysis of FeClj and subsequent dialysis of the sol. Polyvinyl alcohol is often used as a stabilizing agent. The band gap in Fe203 is 2.2 eV. In some of the studies on colloidal Fc203 free radicals were generated by ionizing radiation and electron transfer reactions with the colloidal particles investigated. Buxton et al. observed a cathodic dissolution of a-FCjOj in acidic... 

Radiation chemical studies were carried out with an acidic WO3 H O sol stabilized by polyvinyl alcohol It was found that (CH3)2COH radicals inject electrons into the colloidal particles. A long-lived blue color arose and the absorption spectrum showed a rising absorption above 700 nm. This absorption could have been produced by free electrons, although it could not be ruled out that the electrons reduced ions... 

Polymer adsorption is important in the flocculation and stabilization of colloidal sols and has been reviewed by Vincent et al. (1) and Tadros (2). Polyvinyl alcohol (PVA) has been used in these studies because of its practical application in textiles, adhesives, and coatings. The adsorption of PVA has been studied on silver iodide by Fleer (3) and Koopal (4), and on polystyrene (PS) latex particles by Garvey (5). The adsorption isotherms reported by these workers extend up to 600 ppm PVA. The adsorption at... 

Polyvinyl alcohol (PVA), which is a water soluble polyhidroxy polymer, is one of the widely used synthetic polymers for a variety of medical applications [197] because of easy preparation, excellent chemical resistance, and physical properties. [198] But it has poor stability in water because of its highly hydrophilic character. Therefore, to overcome this problem PVA should be insolubilized by copolymerization [43], grafting [199], crosslinking [200], and blending [201], These processes may lead a decrease in the hydrophilic character of PVA. Because of this reason these processes should be carried out in the presence of hydrophilic polymers. Polyfyinyl pyrrolidone), PVP, is one of the hydrophilic, biocompatible polymer and it is used in many biomedical applications [202] and separation processes to increase the hydrophilic character of the blended polymeric materials [203,204], An important factor in the development of new materials based on polymeric blends is the miscibility between the polymers in the mixture, because the degree of miscibility is directly related to the final properties of polymeric blends [205],... 

In the homogenous mixture of Starch and Polyvinyl alcohol (PVA), 30 % of plasticizer was mixed to make Pure blend. Then 10 % cellulose was mixed into above mixture followed by removal of extra water gave Cellulose-Reinforced starch-PVA blends. The different proportions of Fly ash were mixed into mixture of Cellulose-Reinforced starch-PVA blends to get various fly ash inserted Cellulose-Reinforced starch-PVA blends. Solubility, swelling behaviour and water absorption studies of Fly ash blends were measured at different time intervals at relative humidity of 50-55%. The insertion of Cellulose into starch-PVA blend decreases the solubility of blends due to the hydrophobicity of cellulose, but the solubility further increases by insertion of Fly ash into starch-PVA matrix that indicating the mechanical stability enhancement of blends. The water absorption behaviour of fly ash blends increases rapidly upto 150 min and then no change. The optimum concentration of Fly ash into Cellulose-Reinforced starch-PVA blend was 4%. 

Stabilization in water (surface tension 72 mN/m) can be achieved through the use of surfactants [77] such as SDBS [78] or sodium cholate [79], or long chain polymers such as polyvinyl alcohol. While this allows a non-toxic and easily removed solvent to be used, the presence of the surfactant or polymer molecules can be detrimental to the subsequent applications [80]. 

The stabilizing of aqueous latexes succeeded by using emulsifiers (anionic, nonionic) and/or their mixture, steric stabilizators (polyvinyl alcohol (PVOH), hydroxyethyl cellulose, polyethylene glycol, new protective colloids etc.), and polymerizable surfaces active agents, in general. Vinyl acetate (VAc) emulsion homopolymers and copolymers (latexes) are widely used as binders in water-based interior and exterior architectural paints, coatings, and adhesives, since they have higher mechanical and water resistance properties than the homopolymers of both monomers [2, 4, 7]. 

In the suspension polymerization process, the autoclave reactor is filled with water. PVA, polyvinyl alcohol is the dispersing agent that helps stabilize the suspension. Lauroyl peroxide is the free radical catalyst that starts it all off. The reaction temperature is around 130°F, and the process takes 10—12 hours per batch, with 95% conversion. 

---