SunPregs - Light Curable Prepregs

This novel material is a glass fiber reinforced laminate made from a thickened and light curable unsaturated resin. The material, free from air bubbles, is produced between two films on a continuous line. During manufacture, the SunPreg thickens and acquires a leathery consistency, which is easily handled and can be stored at ambient temperatures for months in the absence of light. The content and type of reinforcing material, preferably glass fibers, can be varied within a wide range. The type of resin used to make the photo-curing prepreg can also be varied in order to generate specific desirable attributes.

SunPreg is particularly advantageous where the use of liquid resins presents problems, because of production techniques involved and/or because of nuisance odor from styrene. This is the case, for example, where work is carried out in areas with poor ventilation, in coating work, in applying an extra laminate layer to vessels, in refurbishing of tanks, etc. Moreover, the use of SunPreg in combination with liquid light curable resins can offer considerable advantages in the production of articles of large surface area, since it saves time and improves quality.

SunPreg and photo-curable surface fillers have simplified work in the entire repair sector. The ability of SunPreg to completely cure in a controlled manner no matter what the ambient temperature, to form a strong bond to a variety of prepped composite and metallic surfaces, makes this an ideal material for patching, repairing, and rehabilitating surfaces. It has a proven history in repairing cars, trucks, boats, HMMWVs, pipelines, shelters, etc. In a pinch it can even be used to patch up an A10.

High Quality, Versatile, Economical, Environmentally Safe

Using light cured SunPreg and novel processes, it has been possible to fabricate many glass fiber reinforced unsaturated polyester articles, more economically, with higher quality, and less styrene emissions, than those typically manufactured by conventional methods, such as hand lay-up, fiber spraying (chop), press molding and resin infusion (VARTM). SUNREZ SunPreg® can be processed on thermoforming or deep drawing equipment, comparable to those required for a thermoplastic. The difference in method is merely that, after forming, the cooling stage for the thermoplastics is replaced by a short duration photo-curing exposure using UV-A lamps.

For a fiberglass reinforced unsaturated polyester article of about 4 mm thickness, an irradiation time of 30 to 40 seconds suffices. After this period, the article is sufficiently hard for it to be taken out of the mold without fear of distortion. Curing is completed outside the deep drawing machine; either in an irradiation zone or in a heating tunnel, without using a supporting mold, and requires only a few minutes.

Thus, an old dream becomes a reality: glass fiber reinforced unsaturated polyester resin; a thermoset with superior mechanical and thermal properties to those of thermoplastics can now be processed very economically by deep drawing or thermoforming, without pollution of the environment. Light curable SunPreg® is of particular interest for applications where the properties of thermoplastics impose limitations.

Additional examples of uses for light curable SunPreg are its combination with thermoplastics (e.g. PVC), or with other moldable materials (e.g. carpet backing) which bond together and provide a very convenient method of forming the combined material. This permits production of a composite with integrally decorative surface in a single pass and dispenses with the need to subsequently paint the surface.

Using SunPreg (Light Curing Prepregs)

SunPregs are used in a variety of ways. Vacuum forming alone or with a rigid or soft thermoplastic face sheet. The composite reinforcement material (mat or fabric) is impregnated with a resin and a SunThik thickening agent, on a machine similar to an APT or Venus impregnator (Wagner “Power Rollers” for paint have been used). The laminate is wet out between PVA films or a PVA film and a thermoplastic sheet. The material is then allowed to thicken to the proper consistency and stored until it is needed (shelf life of the prepreg is the same as for the resin). To use the prepreg it is brought from storage and clamped in a vacuum forming mold, heated if necessary and vacuum formed to the mold. Lights are then turned on and the part cured.

The whole operation can take as little as 5 minutes. For high production rates, parts can he demolded in as little as 30 seconds after exposure to UV-A light. The films are left on the product to protect the surface from contamination. The advantages of light cured vacuum forming are that both sides of the laminate are smooth and free of contamination. If the part requires painting the film is stripped off and the part is ready for paint.