D5

D5 is the shorthand name for Cyclopentasiloxane — a cyclic silicone with five siloxane units, CAS 541-02-6. Widely used as a volatile carrier fluid in personal care formulations. SVHC-listed under EU REACH; restricted in wash-off cosmetics in the EU and UK above 0.1% since 2020. For EU/UK-compliant formulations, NISH PT103 (Propyl Trisiloxane) is the recommended non-cyclic alternative.