Wetting of fibers

Miller, B. The wetting of fibers, in Sdiidc, M. J. (ed.) Surface characteristics of fibers and textiles, Part. II. New York Marcel Ddcker 1977... 

Many defects in molded sheet can be related to fillers. Blistering may be caused by moisture but also by insufficient wetting of fibers and entrapped air pockets. Inconsistent cure and thickening is caused by the presence of moisture. Improper fiber orientation may initiate Ifacture cracks. Flow marks, streaks, warpage, and protruding fibers are also caused by improper fiber orientation. 

The elaboration of a model to describe cotton wicking is very complicated, although the effect of quaternaries on the wetting of fibers is easily seen the softener enhances the interfacial tension strongly. Since the fiber surface energy and the surface tension of water are not affected, the spreading coefficient is decreased, and so is the wetting of the fiber surface. 

Blisters Usually indicates delamination/trapped air or solvent over large area can also indicate undercured resin [and may take six months after molding to show). Can also form when subjected to excessive radiant heat during cure. Often caused by using liquid rather than paste catalyst. Below-surface blister probably due to imperfect wetting of fiber from allowing insufficient time for mat to absorb resin (can usually be detected by inspection on demolding). 

Fluorinated surfactants improve wetting of fibers or fillers in composite resins and speed the escape of bubbles trapped in the viscous resin. 

Wetting of fibers is a displacement of a fiber-air (vapor) interface with a fiber-liquid interface. Wetting of a fibrous assembly, such as a fabric, is a complex process. Various wetting mechanisms, such as spreading, immersion, adhesion, and capillary penetration, may operate simultaneously. 

The first defense line against staining is the fluoiinated soil retardant (see Chapter 13) which reduces soiling with particulate soil and hinders wetting of fibers. When a liquid is spilled on the carpet, the fluorinated repellent provides time for the removal of the liquid by blotting before the liquid wicks into the carpet. However, if the liquid is allowed to wick into the carpet, a stain-resist agent in the fiber surface or inside the fibers must prevent staining. 

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