Polyvinyl acetate structure

It is prepared by the alkaline hydrolysis (saponification) or alcoholysis (ester interchange) of polyvinyl acetate [Structure (5.2)] as shown in Scheme 5.1. 

Ferguson et al. [27] explored how to prepare latex particles with a core/ shell (polystyrene/polyvinyl acetate) structure. A variety of initiators including potassium persulfate, ammonium persulfate, 2,2 -azobisisobutyronitrile,... 

Prepared generally by ester interchange from polyvinylacelate (ethanoate) using methanol and base also formed by hydrolysis of the acetate by NaOH and water. The properties of the poly(vinyl alcohol) depend upon the structure of the original polyvinyl acetate. Forms copolymers. Used as a size in the textile industry, in aqueous adhesives, in the production of polyvinyl acetates (e.g. butynal) for safety glasses. U.S. production 1980... 

A cobalt(II)-chitosan chelate has been prepared by soaking a chitosan film in C0CI2 aqueous solution. The chitosan chelated Co(II) through both oxygen and nitrogen atoms in the chitosan chain. The tetracoordinated, high-spin Co(II)-chitosan chelate could be used as a catalyst, and the polymerization of vinyl acetate was carried out in the presence of Na2S03 and water at pH 7 and normal temperature. The polyvinyl acetate possessed a random structure [114,115]. 

The MWBD method also requires an independent measure of the branching structure factor e. For our analysfs of polyvinyl acetate, it was obtained by comparing M and Bf values calculated from SEC data, analyz d using the MWBD method and various epsilons, and the Mfj and Bj values predicted by Graessley s (21) kinetic model. An epsilon value of 1.0 was found to fit best. 

To illustrate the utility of the MWBD method, a series of commercial polyvinyl acetates and low density polyethylenes are analyzed. Either kinetic models or 13c nuclear magnetic resonance results are used to estimate the branching structural parameter. 

This is just the first example of how the ADMET reaction can be used to model branching behavior and precisely control the structure in olefin-based polymer backbones. Other polymers under study include polyalcohols, polyvinyl acetates, and ethylene-styrene copolymers. The ultimate goal of this research is to be able to define, or even predict, crystallization limits and behavior for many polymers, some of which have not yet been prepared in a crystallized form. 

The effect of structural regularity on properties of polymers may be illustrated by the hydrolytic products of polyvinyl acetate (PVAc). PVAc is insoluble in water, but because of the presence of polar hydroxyl groups, partially hydrolyzed PVAc is soluble in water. 

Tager and co-workers (51) have invoked bundle structures to explain correlations between the viscosities of concentrated polymer solutions and the thermodynamic interactions between polymer and solvent. They note, for example, that solutions of polystyrene in decalin (a poor solvent) have higher viscosities than in ethyl benzene (a good solvent) at the same concentration, and quote a number of other examples. Such results are attributed to the ability of good solvents to break up the bundle structure the bundles presumably persist in poor solvents and give rise to a higher viscosity. It seems possible that such behavior could also be explained, at least in part, by the effects of solvent on free volume (see Section 5). Berry and Fox have found, for example, that concentrated solution data on polyvinyl acetate in solvents erf quite different thermodynamic interaction could be reduced satisfactorily by free volume considerations alone (16). Differences due to solvent which remain after correction for free volume... 

While unaffected by water, styrofoam is dissolved by many organic solvents and is unsuitable for high-temperature applications because its heat-distortion temperature is around 77°C. Molded styrofoam objects are produced commercially from expandable polystyrene beads, but this process does not appear attractive for laboratory applications because polyurethane foams are much easier to foam in place. However, extruded polystyrene foam is available in slabs and boards which may be sawed, carved, or sanded into desired shapes and may be cemented. It is generally undesirable to join expanded polystyrene parts with cements that contain solvents which will dissolve the plastic and thus cause collapse of the cellular structure. This excludes from use a large number of cements which contain volatile aromatic hydrocarbons, ketones, or esters. Some suitable cements are room-temperature-vulcanizing silicone rubber (see below) and solvent-free epoxy cements. When a strong bond is not necessary, polyvinyl-acetate emulsion (Elmer s Glue-All) will work. 

Recent investigations have shown that the behavior and interactions of surfactants in a polyvinyl acetate latex are quite different and complex compared to that in a polystyrene latex (1, 2). Surfactant adsorption at the fairly polar vinyl acetate latex surface is generally weak (3,4) and at times shows a complex adsorption isotherm (2). Earlier work (5,6) has also shown that anionic surfactants adsorb on polyvinyl acetate, then slowly penetrate into the particle leading to the formation of a poly-electroyte type solubilized polymer-surfactant complex. Such a solubilization process is generally accompanied by an increase in viscosity. The first objective of this work is to better under-stand the effects of type and structure of surfactants on the solubilization phenomena in vinyl acetate and vinyl acetate-butyl acrylate copolymer latexes. 

Chemical modification of polymers continues to be an active field of research [1-5]. It is a common means of changing and optimising the physical, mechanical and technological properties of polymers [5-7]. It is also a unique route to produce polymers with unusual chemical structure and composition that are otherwise inaccessible or very difficult to prepare by conventional polymerisation methods. For example, hydrogenated nitrile rubber (HNBR) which has a structure which resembles that of the copolymer ethylene and acrylonitrile, is very difficult to prepare by conventional copolymerisation of the monomers. Polyvinyl alcohol can only be prepared by hydrolysis of polyvinyl acetate. Most of the rubbers or rubbery materials have unsaturation in their main chain and/or in their pendent groups. So these materials are very susceptible towards chemical reactions compared to their saturated counterparts. 

Figure 9 shows another example (39, 40). It is a polyvinyl acetate gel. The important fact with respect to polymeric supports is that the copolymers of the right-hand side of the maximum have the wrong structure. Microscopic investigations sometimes show particles shaped like a squeezed lemon in contact with a solvent they jump up to spherical particles. Thin sections sometimes show hollow... 

Vinyl acetate, the structure of which is shown below, undergoes addition polymerization to form polyvinyl acetate (PVA), used in paints and adhesives ... 

Casein adhesives experienced similar problems. Once the industry recognized that they were not waterproof, as was originally believed, they were rapidly replaced by resorcinols in most structural, cold-set applications where pressure was easily applied. Crosslinking polyvinyl acetates became preferable in some nonstructural, cold-set applications. Cheaper PF resins took over those exterior applications that allowed the use of heat and pressure. UF resins took over many interior applications on the basis of superior costs and mold resistance. Although the basic raw material cost is not a complete picture of the costs of its adhesive derivatives, it is a fairly good index. Table III shows how casein and blood compare with their competition at the present time. Although the exact prices of these materials fluctuate considerably, the approximate order of their costs has not changed much in the last 15 years. The materials are listed in order of cost. 

Polyvinyl alcohol (PVA) is a water-soluble polymer with a glass transition temperature, T, of 80 °C. Although its name implies a homopolymer stmcture, the structure of commercial PVA is a copolymer of vinyl alcohol and vinyl acetate as seen in Fig. 4.2. PVA is made by the incomplete hydrolysis of polyvinyl acetate... 

Early fundamental studies of gas transport in polymers were almost entirely confined to hydrocarbon materials above their glass transition temperatures. The essentially nonpolar structures of the elastomers led to a number of reasonably successful attempts to correlate gas transport parameters with various physical characteristics of the gases and the polymers. These have been summarized and discussed in a number of papers In addition to studies with hydrocarbon elastomers a few studies of other amorphous polymers above their glass transition temperatures have dealt with polyvinyl acetate silicones and fluorocarbon polymers Recent studies have also dealt with poly(methyl aciylate) poly-(vinyl methyl ether) and poly(vinyl methyl ketone) With these more... 

Fig. 1 Structures of some common synthetic hydrophilic polymers (A) poly aery lie acid, (B) polymethacrylic acid, (C) polyhydroxyethyl methacrylate, (D) polyvinyl alcohol, (E) polyvinyl acetate, (F) PEG/PEO, (G) polyacrylamide, (H) polyvinylpyrrolidinone, (I) Nylon 6, and (J) a simple polyurethane.

This alteration in chemical structure makes the product insoluble in water. Vinyl acetate (CH ,COOCH CH.) is ilissolved in methanol anil converted into polyvinyl acetate, usinfj a peroxide as a catalyst. Caustic soda is then added to the solution in methanol when the acetate groups are converted to hydroxyl leaving polyvinyl alcohol as the end product. 

For the investigations reported here polyvinyl alcohol (PVA) and its derivatives such as polyvinyl acetate, polyvinyl ether etc. were used as the basic polymeric materials. These compounds can easily be converted into polymeric analogues [1]. It was shown in an earlier work [2] that PVA-membranes with an asymmetrical structure can be obtained by phase-inverted precipitation similar to the method of Loeb and Sourirajan [3]. These membranes can also be rendered inso].uble in water by... 

The role of phenolic compounds as stabilizers and antioxidants has been studied very extensively in polymers and copolymers (refs. 18, 19). Many papers are devoted to this problem. Studies have been made on the optimization of phenolic structure based on hydroquinone (ref. 20) or catechol (ref. 21) as an antioxidant in polypropylene for example. Others have dealt with the influence of the polarity or stearic effect for different phenolic compounds or substituted phenols on the kinetics of antioxidation reactions - for example in polyvinyl acetate (ref. 22). Lastly, many papers have discussed on kinetic effects. 

If a thermal transition does cause a change in the distribution of various conformations or structures in the system, then the IR spectrum will reflect these concentration changes. Anton measured the IR absorptions sensitive to helix regularity, usually in the 900-1100 m" region, for several polymers as a function of temperature (25). Intensity decreases of these bands were observed above Tg. This change was attributed to a randomization of the chain structure. Anton illustrated this method of determining Tg for PET, polyvinyl acetate, PS, and several nylons. Other phenomena were observed at T Tg such as crystallization of PET and a crystal-crystal transformation of nylon 66. 

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