Starch-containing treating composition for glass fibers and treated glass fibers and strands

An aqueous bulking sizing composition for treating glass fibers during their formation to protect the fibers against interfilament abrasion when fibers are gathered into strands, to allow for facile removal of the strand or strands from supply packages to a bulking operation and to allow the fibers within the strand to become separated to a degree, when the strand or strands are subjected to the separating force of the bulking operation, comprising:

• a. starch having Brabender values equivalent to gel temperature in the range of about 65.degree. C. to about 90.degree. C. and maximum viscosity in the range of about 500 B.U. to about 1200 B.U. at a 9.5 dry solids percent concentration in an amount in the range of about 30 to about 60 weight percent of the nonaqueous components of the composition;
• b. hydrogenated nonionic lubricant in the amount in the range of about 15 to about 36 weight percent of the nonaqueous components;
• c. one or more waxes in an amount of about 3 to about 6 weight percent of the nonaqueous components,
• d. one or more nonionic emulsifiers giving a total HLB in the range of about 8 to about 12 for emulsification of the nonionic lubricant;
• e. a starch plasticizer in the amount of about 3 to about 6 weight percent of the nonaqueous components;
• f. a cationic lubricant in the amount of about 7 to about 14 weight percent of the nonaqueous components;
• g. one or more ester modified amino silane coupling agents in an amount of about 7 to about 15 weight percent of the nonaqueous components, and
• h. an amount of water sufficient to yield a total solids for the composition in the range of about 1.5 to about 4 weight percent of the aqueous composition.