Polyvinyl acetate molecular weight

Polyvinyl chloride/Polyvinyl acetate Good prevent yellowing. High-molecular-weight organotin stabilizers improve radiation stability color-corrected radiation formulations are available. Less resistant than PVC. 

The method outlined above for characterizing branched polymers will hereafter be referred to as the molecular weight and branching distribution (MWBD) method. In the following sections, its application to the long chain branching in polyvinyl acetate and high pressure low density polyethylene will be demonstrated. 

When vinyl flouride is polymerized, a certain percentage of the flourine atoms are found on adjacent carbon atoms. When polyvinyl alcohol made by hydrolyzing polyvinyl acetate was treated with periodic acid by Flory, he found that the molecular weight was greatly reduced, indicating that there were 1,2-glycol units in the chain. But most of the polymers were regular head-to-tail polymers. 

Intractable polymers, such as polyvinyl chloride (PVC), may be flexibilized, to some extent, by the formation of copolymers, such as the copolymers of vinyl chloride and vinyl acetate or octyl acrylate, or by the addition of nonvolatile low-molecular-weight compounds (plasticizers) having solubility parameters similar to those of the polymer. Thus PVC is plasticized by the addition of dioctyl phthalate. The flexibility of these products is proportional to the amount of plasticizer added. Copolymers, such as the vinyl chloride-vinyl acetate copolymer, require less plasticizer to obtain the same degree of flexibility. 

Heat-setting resins cannot be plasticized by low molecular weight plasticizers. Polyvinyl acetals have been claimed for these products. American Cyanamid Co. has suggested polyvinyl acetals or butyrals in an amount of 10 to 25% of the resin for urea and melamine resins. For varnishes and adhesives, combinations of phenolic resins and polyvinyl formal are recommended. Polyvinyl acetals with higher alkyl radicals are suitable for cellulose esters and improve elasticity as well as resistance against water. 

Polyvinyl acetate polymers synthesized by emulsion polymerization168, show strikingly different behavior188,189). Figure 41 shows Dz as a function of Mw. For the low molecular weights, D2 decreases as expected but from Mw = 14 106 onwards Dz remains constant. The measured samples were products obtained at different extents of monomer conversion. The soap surrounding the latex particles was removed and the samples were dissolved in methanol and measured. The behavior of Dz in this system is understood by recalling that... 

Exercise 29-17 Polyvinyl alcohol prepared by hydrolysis of polyethenyl ethanoate (polyvinyl acetate Table 29-1) does not react with measurable amounts of periodic acid or lead tetraethanoate (Sections 16-9A and 20-4A). However, periodic acid or lead tetraethanoate treatment of the polymer does decrease the number-average molecular weight, for a typical sample from 25,000 to 5000. Explain what these results mean in terms of the polymerstructures and the mechanism of the polymerization. 

In the case of styrene the polymer contains at both ends a carboxyl group (chain termination by coupling), while polymers characterized by a termination reaction by disproportionation (polyvinyl acetate, polymethyl methacrylate) contain only one carboxyl end group. The carboxyl groups in these polymers were transformed to acid chlorides and coupled with a diol, e.g. 1,6-hexanediol. The comparison of the molecular weight of the polymers before and after condensation permits to elucidate the... 

Wagner, R. H. Intrinsic viscosities and molecular weights of polyvinyl acetates. J. Polymer Sci. 2, 21 (1947). 

PC PE PES PET PF PFA PI PMMA PP PPO PS PSO PTFE PTMT PU PVA PVAC PVC PVDC PVDF PVF TFE SAN SI TP TPX UF UHMWPE UPVC Polycarbonate Polyethylene Polyether sulfone Polyethylene terephthalate Phenol-formaldehyde Polyfluoro alkoxy Polyimide Polymethyl methacrylate Polypropylene Polyphenylene oxide Polystyrene Polysulfone Polytetrafluoroethylene Polytetramethylene terephthalate (thermoplastic polyester) Polyurethane Polyvinyl alcohol Polyvinyl acetate Polyvinyl chloride Polyvinyl idene chloride Polyvinylidene fluoride Polyvinyl fluoride Polytelrafluoroethylene Styrene-acrylonitrile Silicone Thermoplastic Elastomers Polymethylpentene Urea formaldehyde Ultrahigh-molecular-weight polyethylene Unplasticized polyvinyl chloride... 

Poly(vinyl acetate vinyl alcohol) - A water plasticized polyvinyl acetate with minor hydrolysis to form vinyl alcohol sites to a molecular weight of -50,000 g/ mole plasticized with mono/diethylene glycol dibenzoate. This material was dissolved in ethanol for application purposes. 

Viscometry The specific viscosity of each polymer from the bulk polymerization was measured in acetone at 30°C using an Ubbelohde dilution viscometer. Five concentrations in the range of 1.120 to 0.242 g/d poly(vinyl acetate) and polyvinyl trideuteroacetate) and 0.385 to 0.084 g/dl (poly(trideu-terovinyl acetate)) were run. Intrinsic viscosity was calculated by extrapolation of the Tlsp/c versus c plot to zero concentration. Number average molecular weights were calculated using the equation(20) [q] =1,0 x 10 1 [Mn] 0 72 which is in the mid range of the equations listed. 

Molecular Weight. Molecular weight values were obtained with a GPC unit. This unit was standardized for polystyrene, so the polyvinyl acetate values are not quantitative. The weight average molecular weights were between 500, 000 and 900, 000. No trends of molecular weight average or distribution could be deduced. 

PVA is further modified to obtain polyvinylacetatephthalate (PVAcP), which is used in enteric coatings. PVAcP is prepared from the reaction of partially hydrolyzed polyvinyl alcohol, sodium acetate and phthalic anhydride. It consists of 55 to 62% of phthalyl groups. The PVA used is a low molecular weight grade with 87 to 89 mole% hydrolyzed. Since only vinyl alcohol portions of the partially hydrolyzed PVA are phthalated, the acetyl content remains constant before and after the reaction. 

C 14-------and D. M. Levi Molecular weight of polyvinyl acetate by light... 

Polyvinyl acetate (PVAc) in the pure and solid form is colorless and transparent. It is somewhat brittle unless the degree of polymerization is low. Its softening temperature is between 40 and 90F (4 and 32C), depending on the molecular weight. It shows the phenomenon of cold flow. 

Plot the reduced viscosity of each solution against concentration, and extrapolate to zero concentration to obtain the intrinsic viscosity, [t ]. Finally, calculate the molecular weight of the polyvinyl acetate by the formula... 

Effect of Acetyl Content of Polyvinyl Alcohol. Fig. 3 shows the effect of a low concentration (0.10% w/v) of Gohsenol samples which have similar molecular weights but varying acetyl contents on the rate of polymerisation of vinyl acetate solutions. Increase of acetyl content decreases the rate of polymerisation. However this effect cannot account for the difference between the samples shown in Fig. 2 because these differ by only 0.1% in acetyl content. On the other hand any effect of acetyl content in the Vlnol series was small rates of 5.8, 5.9, and 5.4 %/min were observed using Vlnol 325, 425, and 523 which have similar molecular weights and acetyl contents of 1.8, 4.0, and 12 mole % respectively. 

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