Water, volatiles, monomers and chlorohydrocarbons

Water and Volatiles (Monomers, Chlorohydrocarbons) in Vinyls and Acrylics 

The difference between Method 1 for the determination of water and volatiles in polyalkenes and that described below for the determination of water and volatiles in vinyls and acrylics, is that in the latter method, the polymer is heated in the presence of the residual air in the sample tube, and in the first method (polyalkenes) the residual air in the sample tube is replaced with inert carrier gas, helium, before the sample is heated. With the non-olefinic polymers the same results for water content are obtained by both methods, ie. it is not necessary to replace the air with inert gas. Polyalkenes, however, are oxidized if heated in the presence of air, thus producing additional amounts of water. Jeffs recommends that before carrying out any quantitative work on the volatile constituents obtained from a polymer powder, a preliminary gas-chromatographic investigation should be carried out, of their complexity. For example, one polymer showed nine components other than air, water and the original monomer. These 

The major volatile constituents in vinyl chloride - vinyl acetate copolymers is unpolymerised vinyl acetate, and this monomer is difficult to eliminate from the polymer by ordinary drying methods. The plot of volatile constituents (water, vinyl chloride monomer and vinyl acetate) against the sample temperature shows that the maximum amount of vinyl acetate is eliminated from the sample under the test conditions, only in the temperature range 130 to 145 C. Above this temperature the amount of vinyl acetate detected starts to decrease. A similar effect is found for water. At the same time, another peak begins to appear in the chromatogram. This peak corresponds, in retention time, to acetaldehyde. This is consistent with the hydrolysis of the vinyl acetate monomer by water at the elevated temperatures, to give the unstable vinyl alcohol and, hence, acetaldehyde. A heater temperature of 135 C is recommended for these copolymers. 

A method involving head space analysis gas chromatography has been described for the determination of monomers and volatiles in PVC.  

Residual vinylchloride monomer from 0.02 to 0.1 ppm in PVC has been determined by gas chromatographic - mass spectrometric monitoring.  

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