Poly(phenylsilsesquioxane)

Poly(phenylsilsesquioxane) (CAS 70131-69-0) is a phenyl-substituted silsesquioxane ladder or cage polymer. It is used at low concentrations (0.1–0.5%) in automotive spray sealants and coatings as a film-forming resin that improves hardness and gloss relative to pure polydimethylsiloxane (PDMS) formulations.

Health note — H330 is ingredient-level only at consumer concentrations: At the pure substance level, poly(phenylsilsesquioxane) carries an H330 (fatal if inhaled, Cat 1) classification in some SDS. However, at the concentrations used in consumer spray sealants (0.1–0.5%), this H-code does not meet the GHS concentration cutoffs required to propagate to the finished-product mixture classification. Product SDSs that list this ingredient at <0.5% typically show no H330 at the mixture level in Section 2. Always use Section 2 mixture-level codes for product scoring — ingredient-level H330 at trace concentrations is not authoritative for the finished product.

Environmental: Low bioaccumulation concern (high molecular weight resin). No aquatic toxicity classifications assigned. Persistent in the environment due to silicone network stability, but environmental impact at the trace concentrations used in consumer products is minimal.