Method of sizing strands

A method of sizing a filament which comprises the steps of

• A. Immersing a mat of continuous strand filament wound into the form of a roll in a liquid ketone solvent solution containing less than a saturation amount of unsaturated epoxy resin and polyamine cross-linking curative therefor in a container with a vapor space above said solution, where said ketone chemically blocks said polyamine from crosslinking said epoxy resin.
• B. Soaking the immersed filament roll in said solution at substantially atmospheric pressure until the said roll is substantially saturated with said solution.
• C. Applying a vacuum to said vapor space, to remove residual air and thereby more completely saturate said roll with said solution.
• D. Removing the vacuum separating said roll from said solution, and placing said roll in a suitable container.
• E. Applying a vacuum to said suitable container to remove residual ketone solvent from the roll, thereby unblocking said polyamine curative and allowing the curative to partially cross-link said epoxy on said filament to a "B" stage cure.
• F. Removing said vacuum and recovering the roll of sized strand filaments having a partially crosslinked epoxy coating thereon in an amount of about 0.5 to about 15 weight percent of the filament and
• G. Cooling said roll of sized filament to at least 10.degree. C. to stop the crosslinking reaction.