Vinyl content, residual

Ethylene has also been copolymerised with a number of non-olefinic monomers and of the copolymers produced those with vinyl acetate have so far proved the most significant commercially . The presence of vinyl acetate residues in the chain reduces the polymer regularity and hence by the vinyl acetate content the amount of crystallinity may be controlled. Copolymers based on 45% vinyl acetate are rubbery and may be vulcanised with peroxides. They are commercially available (Levapren). Copolymers with about 30% vinyl acetate residues (Elvax-Du Pont) are flexible resins soluble in toluene and benezene at room temperature and with a tensile strength of about lOOOlbf/in (6.9 MPa) and a density of about 0.95 g/cm. Their main uses are as wax additives and as adhesive ingredients. 

Bauer et al. describe the use of a noncontact probe coupled by fiber optics to an FT-Raman system to measure the percentage of dry extractibles and styrene monomer in a styrene/butadiene latex emulsion polymerization reaction using PLS models [201]. Elizalde et al. have examined the use of Raman spectroscopy to monitor the emulsion polymerization of n-butyl acrylate with methyl methacrylate under starved, or low monomer [202], and with high soUds-content [203] conditions. In both cases, models could be built to predict multiple properties, including solids content, residual monomer, and cumulative copolymer composition. Another study compared reaction calorimetry and Raman spectroscopy for monitoring n-butyl acrylate/methyl methacrylate and for vinyl acetate/butyl acrylate, under conditions of normal and instantaneous conversion [204], Both techniques performed well for normal conversion conditions and for overall conversion estimate, but Raman spectroscopy was better at estimating free monomer concentration and instantaneous conversion rate. However, the authors also point out that in certain situations, alternative techniques such as calorimetry can be cheaper, faster, and often easier to maintain accurate models for than Raman spectroscopy, hi a subsequent article, Elizalde et al. found that updating calibration models after... 

Films stabilized with HD-2, HD-3 or HALS-1 were also examined for residual vinyl unsaturation after cure. All the stabilized films had non-tacky surfaces and had essentially equivalent vinyl content to the unstabilized film indicating that the stabilizers have a minimal effect upon cure reactions. 

Figure 1. Calibration plot for residual vinyl content in cyclized 12-polybutadiene. Values calculated for Polymers B, C, EB, FI, and DI with different initial vinyl contents are represented by...

Figure 3 presents a superposition of kinetic data for the radiation-induced loss of 1,2 unsaturation in VB, the data having been normalized for the different initial vinyl contents in the various polymers. The residual unsaturation-dose data for Polymer A were plotted directly, yielding the solid line shown data for Polymers B, C and 6 were arbitrarily plotted at doses greater than the actual doses by amounts equal to shift factors of 2.0, 2.7 and 3.0 Mrad, respectively. These shift factors correspond to the doses required to decrease the 1,2 unsaturation of Polymer A from 98.5% initially to 90.1, 86.0 and 85.0% (the initial vinyl contents of Polymers B, C and 6), respectively. By this normalization procedure, the data for the three VB polymers used in this work (A, B and C) and the single data point available from the literature (Polymer 6) could be fitted to a common kinetic plot. From the initial slope to the solid line in Figure 3, Gg(-1,2) was found to have the rather high value of t SSO. Taking the tangent to the line at 85% 1,2, we obtain G3.q(-1,2) 270, which compares...

The present pyrolysis-IR study under our conditions produced similar results see Table III). An examination of the product yields, as the fraction of vinyl linkages increased over the range from 10 to 94.5%, showed an increase of ethylene relative to 1,3-butadiene. All of the data for Table III were collected under identical experimental conditions— 600°C and 45 sec firing time. Essentially all polymer was completely vaporized under these conditions leaving virtually no residue. The ratio values were calculated from absorbance values of the peaks assigned to ethylene and butadiene, respectively. In addition, it was noted that the relative amount of methane also increased with increasing vinyl content of the polybutadiene. 

Another aspect that needs stressing is that the differences among high cis polybutadienes cannot be accounted for by their different hysteresis. In fact, even by assuming an influence of the residual vinyl content, if any, its influence on hysteresis should go exactly in the opposite direction. 

A common procedure for the preparation of vinylated alkyds is as foUows. A base alkyd resin is brought to the desired endpoint. The resin is then cooled to about 160°C and often diluted with aromatic thinner. The desired monomer is added, usually at about 20 —60% based on the final product, foUowed by an appropriate amount of a free radical initiator. Alternatively, a premix of the monomer and the initiator is added at a controUed rate over most of the reaction. The reaction is brought to monomer reflux, until the residual monomer content has fallen below a specified level. Residual monomer, if any, is stripped away before the product is diluted in a solvent, filtered, and packaged. 

Commercial polyfvinyl alcohol) (e.g. Gelvatol, Elvanol, Mowiol and Rhodo-viol) is available in a number of grades which differ in molecular weight and in the residual acetate content. Because alcoholysis will cause scission of branched polymers at the points where branching has proceeded via the acetate group, polyfvinyl alcohol) polymer will have a lower molecular weight than the poly (vinyl acetate) from which it is made. 

A number of grades of poly(vinyl formal) are commercially available (Formvar, Mowital) which vary in degree of polymerisation, hydroxyl content and residual acetate content. 

Table I4.P shows the influence of these variables on some properties. The residual hydroxyl content is expressed in terms of poly(vinyl alcohol) content and residual acetate in terms of poly(vinyl acetate) content.

When dopa was oxidized using the PIPo-Cu catalyst, the distinguished acceleration was observed as compared with the PVIm-Cu or imidazole-Cu catalysts (Fig. 6). An increase in content of the N-vinylpyrrolidone residue in the PIPo copolymer caused higher activity of the Cu complex for the dopa oxidation. The similar acceleration was also produced when N-methyl-pyrrolidone was added to the system of PVIm-Cu. However, nearly 103 fold concentration of the pyrrolidone residue was necessary as compared with the PIPo copolymer. Addition of homopolymer of N-vinyl-pyrrolidone to PVIm-Cu caused no acceleration. 

Vinyl chloride monomer (VCM) is the main substrate for the manufacture of polymers used as packaging materials for food. Since VCM is considered by lARC to be a human carcinogen, monomer levels in PVC food packaging materials are strictly controlled. To ensure a safe product, the residual content of VCM in the finished material or article is limited to one mg per kg in the final product (Council Directive 78/142/EEC). Furthermore, VCM should not be detectable in foodstuflfs. Commission Directives 80/766/EEC and 81/432/ EEC give the method of analysis for official control of the VCM level in food packaging materials and in foods - gas-phase chromatography using the headspace method, after dissolution or suspension of samples in N,N-dimethylacetamide. Both residual monomer content of the polymer and... 

Fig. 1 shows the increase of nitrite band near 780 cm- for various alcohol contents in ethylene-vinyl alcohol copolymers. The analysis of the hydroxyl region of the IR spectra (not shown) indicated that the reaction was not quantitative (residual OH band). The precise analysis of this band ( 34(X) 70 I / mol. cm) as w ell as the nitrite band (e780 639 I / mol. cm) allows to evaluate the reaction yield considering the total film thickness (Transmission 1R). The values decrease when the OH content increases (0.75 0.62 0.59 ans 0.59 for vinyl alcohol contents 2.6,4.9, 7.7 and 10.1% respectively). Complementary analysis by reflexion IR (HATR) showed that the first 5-8 pm (Germanium crystal) were fully transformed while the analysis of the first 20-25 pm (Zinc Selenide crystal) revealed a decrease of the yield from 1 to 0.5 when the alcohol content was increasing. Then, this treatment can be helpfull for surface modification of membranes. 

Low vacuums are required for effective degassing of residual contents of vinyl acetate (< 50 mbar). The use of stripping agents considerably reduces the proportion of residual volatile components. 

The chlorine content of Polymer Fractions I, II, and III was determined by gravimetric analysis and found in all cases to be within 1% of the value for undegraded poly (vinyl chloride). (Since it was difficult to remove the last traces of solvent, the actual chlorine content of the polymers was probably even closer to the theoretical value.) The chlorine content of the insoluble residue was much lower. Thus, the insoluble residue of samples obtained from the experiments illustrated by Table III contained typically only 46-49% Cl. 

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