Styrene monomer emission

Although most boats are produced via the open mold spray-up process, environmental pressures are mounting due to the high styrene monomer emissions that are inherent in open molding techniques. Closed molded techniques are beginning to be commercially practiced, and it is anticipated that these processes will replace the open mold process. 

Styrene monomer emissions sometimes cause occupational and environmental health concerns. Evaporation of styrene can be reduced by adding wax to the formulation it is immiscible and comes to the surface, forming a barrier layer. Another method of reducing volatilization is to use a less volatile monomer such as methyl styrene. 

Fig. 22. Fluorescence decay curves for (a) poly(styrene). in CH2Q2 solution. Number denotes emission wavelength monitored short wavelength corresponds to monomer emission, long wavelength to exdmer emission...

The most frequently encountered emissions in plastics processing are probably solvents (from adhesives and paints) and styrene monomer (from polyester/glass lamination). There may be a health hazard from curing agents aliphatic amine-types can cause serious irritation (even burns) and there is also a serious rash/ asthmatic-type response. Liquid organic peroxides, such as MEKP, should be treated with extreme caution. They are sensitive to heat, are themselves combustible and will promote combustion. 

The existence of three kinetically distinct species according to the triad distribution would be consistent with the necessity for triple exponential fitting to the data obtained in the monomer emission region of styrene copolymers [72]. However it has been claimed [73,75] that such a model is inconsistent with observations regarding excimer dissociation in time resolved spectroscopy [72], decay data for styrene... 

It is of interest to note that within the limit of acoiracy of these experiments, monomer decay curves (Fig. 22) were single exponential, whereas Sdieme 1 predicts dual exponentiality (Eq. 65). The results thus imply that in pdyslyrene reverse dissociation ( feedback ) of the excimer is not of importance. This point is amplified by time-resolved fluorescence spectra which show that late- ted >ecti a (see experimental section) are composed exclusively of excimer emission (Fig. 23). The same is true in poly(a-methylstyrene) In view of more recent work mi other vinyl aromatic ptdymers, it would be of interest to study pdy(styrene) further with more sophisticated techniques. 

Monomers Not Polymerizable by Plasma Initiation. When styrene and a-methy1styrene were subjected to plasma treatment, the monomers became yellowish and only trace amounts of insoluble films were formed. The discoloration was intensified and extensive formation of dark films were observed if carbon tetrachloride was added as the solvent. No post-polymerization was detectable for these monomers. Generally styrene and a-methylstyrene readily undergo thermal polymerization. However, no thermal polymerization was possible for these monomers after having been subjected to plasma treatment for one minute or less. It has been demonstrated from the emission spectra of glow discharge plasma of benzene (6) and its derivatives (7 ) that most of the reaction intermediates are phenyl or benzyl radicals which subsequently form a variety of compounds such as acetylene, methylacetylene, allene, fulvene, biphenyl, poly(p-phenylenes) and so forth. It is possible that styrene and a-methylstyrene also behave similarly, so that species from the monomer plasma are poor initiators for polymerization. 

During the manufacturing process of styrene-butadiene rubber the polymerisation is stopped at a conversion rate of less than 90%. The residual monomers styrene and butadiene are removed by distillation. The odour-in-tensive compounds 4-phenylcyclohexene (from styrene and cis-butadiene) and 4-vinyl cyclohexene (from cis-butadiene and trans-butadiene) can be formed from the remaining monomers under the conditions of a thermally permitted Ti2s-t- 4s Diels-Alder cyclic addition. During indoor air measurements, carried out in six different office rooms in each case 3 days after new carpets had been laid, concentrations of 4-phenylcyclohexene of 29-45 pg m could be ascertained. It is suspected that the emission of the trimer of 2-methyl-l-propene from a glued carpet is also caused by chemical reaction. 

The cyclopolymerization of the title compound (St-Cj-St), C3 cyclopolymerization, is reviewed. The polymerization has the similar behavior to the fluorescence emission of 1,3-diphenylpropane and its derivatives (n=3 rule or C3 rule). The monomer and its derivatives were prepared by the convenient method from the corresponding a-phenethylalcohol derivatives, using dimethyl sulfoxide-ZnCl2 CCl3COOH system. St-C3 St gave a cyclopolymer only by cationic initiators, and the presence of cyclized units in the main chain was elucidated by several spectroscopic analyses and also by the isolation of cyclocodimers obtained from the reaction of the monomer with styrene in the presence of the catalytic amount of CF3SO3H. 

The monomer and exclmer decay time quoted in Table 3 were measured using filters to Isolate emission wavelengths. Greater accuracy is possible using full spectral and time resolution however, and such experiments have recently been carried out on poly(styrene) (42). For photostationary conditions, the following relationships hold ... 

When polymerization is used as the hardening principle, reactive components combine to form the binder, e.g., unsaturated polyesters with styrene or acrylate monomers. Here, one component often behaves as a reactive solvent for the other, and low-emission coating systems are the result. Cross-linking can be carried out at room temperature (cold curing) or by radiation curing. 

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