5: POLY(PHENYLENE SULFIDE) 139
The optical transmittance of the polymer at 400 nm is
higher than 80%. Thus, the triazine unit effects a high
refractive index of 1.7492 at 633 nm [73].
5.5.5 Solubility
The polymer has a broad compatibility with chemi-
cals and solvents, offering a better chemical resistance
than stainless steel. No solvent for PPS is known below
200
◦
C. Above this temperature, 1-chloronaphthalene
is a suitable solvent. Molecular mass, characteriza-
tion e.g., by size-exclusion chromatography at mod-
erate temperatures can be done only when derivatives
are formed prior to analysis in order to enhance the
solubility [74]. The sulfide groups are oxidized, by a
mixture of nitric acid and methanesulfonic acid result-
ing in a poly(p-phenylene