Secondary coating compositions for glass fibers, glass fibers coated with the same and composites reinforced therewith

A glass fiber strand having thereon the dried residue of an aqueous secondary coating composition, the glass fiber strand comprising a plurality of glass fibers having thereon a primary coating of a dried residue of an aqueous sizing composition, the aqueous secondary coating composition comprising:

• (a) a polysiloxane having:
• (1) an alkyl substituent attached through a carbon atom directly to a silicon atom of the polysiloxane;
• (2) an alkoxy substituent attached through a carbon atom of an alkyl group directly to a silicon atom of the polysiloxane, the alkoxy substituent comprising the alkyl group, an alkyl ether group and a terminal group selected from the group consisting of hydrogen and an alkoxy group having about 1 to about 8 carbon atoms, the alkyl ether group having the formula (C.sub.n H.sub.2n O).sub.q where n has an average value of about 2 to about 6 and q has an average value of about 1 about 100 inclusive;
• and
• (3) endblocking groups independently selected from the group consisting of a phenyl group, an alkyl group having about 1 to about 20 carbon atoms and combinations thereof,
• wherein the polysiloxane is essentially free of silicon-bonded hydroxy groups and alkoxy groups attached through an oxygen atom directly to a silicon atom of the polysiloxane, and
• (b) zero to less than about 50 weight percent on a total solids basis of a film-forming material capable of forming a uniform continuous coating on the glass fibers.