SURFACE VEIL

Table 2.18 Characteristics and applications of nonwoven surfacing veils...

Surfacing mats Decorative overlay surfacing veils Monofilaments Generally less than 1.oz./sq. ft 0.010 to 0.030" thick 5-6 Reinforcements of gel coats Special surface effects in laminates... 

The Nexus surfacing veil exhibits excellent resistance to alcohols, bleaching agents, water, hydrocarbons, and aqueous solutions of most weak acids at boiling. Being a polyester derivative, it is not resistant to strong acids such as 93% sulfuric. 

Processors fabricate underground fuel storage tank by combining isopolyester resin with fiberglass and surfacing veils on a cylindrical mandrel. Since 1964, almost 350000 isophthalic polyester tanks have been buried under service stations around the United States, according to the Fiberglass Petroleum Tank and Pipe Institute. 

A final layer consisting of one or two light surface veils is normally applied. The resin used for this outer layer may typically contain up to 0.5 wt% of paraffin wax and possibly a UV stabilizer. It main function is aesthetic but it also fulfils other purposes. The paraffin wax will bloom to the surface of the uncured resin. This will seal the surface and prevent air contact, thus avoiding any difficulties which may arise due to oxygen inhibition of the resin curing process. The wax also acts as a UV stabilizer and protects the vessel from attack by the sun in climates where this is an issue. 

For more corrosive environments, epoxy vinyl esters and phenolic laminating resins [10] are used quite successfully as well, particularly where fire retardancy is an issue, such as in the oil industry. The glass is normally E-glass roving, but some mats are used for more complicated shapes and an external surface veil is incorporated to produce an acceptable degree of outer smoothness. 

Frequently, to provide resistance to weathering, erosion, or chemical attack, a resin-rich surface coat (gel coat) is added. This surface layer is applied first and then allowed to stiffen into a tough layer (not cured) before additional layers are applied. It usually is reinforced with a surface veil using C-glass (rather than the usual E-glass) if chemical resistance is required, or a synthetic fiber veil may be used for resistance to weather, particularly sunlight. The resin may be a special formulation that includes TP to improve the surface appearance. Subsequent layers of mat, fabric, or combinations are then applied. 

P(l) Surfacing veils should be considered where their inclusion is beneficial to improving the appearance and properties of surface layers and coatings. They should be used where high resistance to chemical environments is required. C-glass materials are commonly used. 

P(2) Surface veils should not be used on surfaces to be joined by bonding. If they are present, the whole layer thickness shall be removed by grinding over the area required for bonding. 

Surface veils are lightweight thin surfacing materials usually constructed from swirl mats either in glass or from a synthetic fibre. Their main use is to act as a decorative surface, shielding from view the texture of the underlying structural reinforcement. But they also may be used in conjunction with gel coats for added support. C-glass surface veils are... 

The systems can include many options surface veil, chopped liners, sprayed resin systems, hoop winding strands, helical winding strands, resin bath, unidirectional tape, woven roving tape, pigmented resin surfaces, wax-resin surfaces, gel coats, BPO catalyst, epoxy resins, vinyl ester resins, filled resin systems, abrasive resin systems, polyester foam, syntactic foam, and charting film. 

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