Polyvinyl alcohol PVAL

Other vinyl polymers 4.9.1 Polyvinyl alcohol (PVAL or PVOH)... 

Polyvinyl alcohols (PVAl) are manufactured by saponification of vinyl acetate polymers (PVAc). Properties of PVC using PVAl as a protective colloid are influenced by the solution viscosity of the PVAl, i.e. the degree of polymerization of the PVAc and the degree of saponification. Polyvinyl alcohols of 75-90% hydrolysis are primary suspension agents for S-PVC, whereas polyvinyl alcohols of 25-40% hydrolysis are secondary suspension agents, which control the agglomeration of the primary particles. Partially hydrolyzed PVAc can be block or random polymers. 

The ESD behavior can be provided by blending in a flexible-chain polymer with an active -OH or -SH group, viz. polyvinyl alcohol (PVAl), ethylene-vinylacetate (EVAc), polyvinylphenol (PVPh), a copolymer of ethylene oxide and epi-chlorohydrin (EO-CHR), maleated copolymer, aliphatic polysulfides, etc. These low performance resins have been incorporated into a variety of alloys and blends (see Table 1.79). 

Polyvinyl chloride (PVC), which belongs to the family of vinyl polymers, and its copolymers vjith vinylidene chloride (PVDC), polystyrene (PS) and its copolymers, polyvinyl acetate (PVA), polyvinyl alcohol (PVAL), ethylene copolymers with vinyl alcohol (CEVA) are also employed in anticorrosion films [3,18,20,22-24]. 

PVA is not suitable as the base of packaging materials since its physical and mechanical properties are impaired abruptly above the glass-transition temperature (28°C). It is used, nevertheless, along with polyvinyl butyral (PVB), polyvinyl alcohol (PVAL), alcohol-soluble polyamides and polyacrylates as a layer-carrier of Cl in multilayered films. The layer is formed via application of emulsions, suspensions or solutions of named polymers containing Cl onto the base film [23-26]. 

Elastomers (thermoplast-like) polyvinyl chloride (PVC) polyvinyl alcohol (PVAL) polyethylene (PE)... 

Monomers act as plasticizers. They diffuse much more slowly than water molecules. A similar plasticizing effect of water is also observed with polyvinyl alcohol (PVAL) and linear polyurethane (TPU). This applies in general to swelling of plastics in solvents. 

Figure 4.4 Effect of sodium chloride (NaCl) in the polyvinyl alcohol (PVAL) solution on fibre morphology (voltage = 5kV, tip-target distance = 10 cm flow rate = 0.2 ml/h). Concentration of NaCl solution in water (a) 0.05 vol% (b) 0.10 vol% (c) 0.15 vol% and (d) 0.20 vol%...

Vinyl acetate monomer (VAM) is broadly used for the manufacture of polyvinyl acetate (PVAc), polyvinyl alcohol (PVAl) and ethylene-vinyl acetate (EVA)-, vinyl acetate-acrylic-, vinyl chloride-vinyl acetate (VC/VAc)-, and vinyl pyrroHdone-vinyl acetate (V p/VAc)-copolymers, oxidation to yield ethylene oxide (EO) ... 

Water as diluent has obvious advantages and has been developed for many free-radical polymerizations. Thus suspension polymerization involves the dispersion of the non-miscible monomer in water as droplets (0.1-5 mm diameter) by means of agitation and protective colloids or dispersing agents (e.g. polyvinyl alcohol, PVAL), and adding a monomer-soluble initiator. The polymer ends up approximately the same size as the original droplets and the system can be viewed as many small bulk polymerizations. As water is the continuous phase the viscosity remains constant and good heat transfer occurs. This process is used for PVC. 

The combination of starch with a soluble polymer such as polyvinyl alcohol (PVAl) and/or polyalkylene glycols was widely considered since 1970. In the last years the system thermoplastic starch/PVAl has been used for production of starch-based loose fillers as a replacement for expanded polystyrene (Fig. 5). 

Vinyl acetate (CH2=CH(OCOCH3)) is polymerized to polyvinyl acetate (PVAc) which is used in adhesives and lacquers. Its major use, however, is in the preparation of polyvinyl alcohol (PVAl) which cannot be prepared from vinyl alcohol (CH2=CHOH) which isomerizes into acetaldehyde (CH3CHO). 

Butyl rubber Natural rubber Neoprene rubber Nitrile rubber Polyvinyl alcohol - PVAL Polyvinyl chloride - PVC Viton (Fluoroelastomer)... 

PVMQ Silicone rubber with vinyl, methyl, and phenyl substituents PVOH Polyvinyl alcohol (PVAl)... 

While polyvinyl alcohol (PVAL), obtained from the hy(frolysis of polyvinyl acetate (PVAC), is insoluble in organic solvents, the acetal produced from the eondensation of butyraldehyde and PVAL is soluble and used as a base for wash primers or metal conditioners. 

Table 1.6 lists some crystalline and amorphous polymers, and some borderline ones. The borderline cases, which are normally amorphous, may aystallize under high mechanical strain rates. Such is the case for NR, polyisobutylene (PIB), butyl (OR), and polyvinyl alcohol (PVAL), silicone rubber (MQ), and chloroprene rubber (CR). 

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