Stock material or miscellaneous articles – Structurally defined web or sheet – Continuous and nonuniform or irregular surface on layer or...
Patent
1997-04-21
1999-01-12
Hess, Bruce H.
Stock material or miscellaneous articles
Structurally defined web or sheet
Continuous and nonuniform or irregular surface on layer or...
428 92, 428141, 428144, 428143, 428220, 428327, 428407, 264 80, 264134, 264309, 264510, 156 622, 156279, 156280, B32B 900
Patent
active
058585087
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
This invention relates to a method for imparting antislip properties to thermoformed plastic surfaces and products. The invention is particularly useful for increasing the friction on load bearing and cargo carrying surfaces such as those of thermoformed pickup truck bed liners. The invention selectively increases frictional effect primarily through enhanced three dimensional macroscopic surface relief and roughness so that it is effective even when the surface is wet. Composition of the surface is also a factor contributing to the increased friction. The invention is useful for a variety of other practical and industrial applications as well as for games and recreational products. The invention provides a hard and tough antislip surface preferably with an elastomeric component and with a hardness that is not brittle or sharp. It is suitable, for example, for bare feet applications such as swimming pool surfaces, showers, bathtubs, walks, and stairs.
BACKGROUND INFORMATION
Essentially all truck bed liners are thermoformed from high density polyethylene (HDPE) sheets. Other materials such as ABS, synthetic rubber plastic, and other thermoplastic polymers are sometimes used. The thermoplastic sheets are heated to a thermoforming temperature in a thermoforming oven and are deformed by ambient air pressure after application of vacuum on one side in a thermoforming mold to produce the desired product. Many other products are also manufactured by this process. A disadvantage of the HDPE material however is its low coefficient of friction. HDPE surfaces become even more slippery when wet.
U.S. Pat. No. 4,693,507 (Dresen et al.) describes a truck bed liner with antislip surface properties. Increased coefficient of friction on the liner surface is achieved by applying a continuous film or layer of elastomeric material over the HDPE sheet. The thickness of the integral elastomeric layer or film is typically in the range of 25 mils-30 mils (625.mu.-750.mu.). The elastomeric film is preferably coextruded over the HDPE sheet which is typically 180 mils-250 mils (4.5 mm-6.2 mm) in thickness. However, Dresen et al. state that the elastomeric film layer can alternatively be applied to the HDPE sheet by lamination, by adhesive, or by heat application.
An increased frictional force is therefore achieved primarily by the "plowing effect" or embedding effect of harder cargo pieces pressing into the softer continuous elastomer layer. A disadvantage of the Dresen et al. scheme however, is that the frictional force attributable to the integral elastomeric layer is reduced when the elastomer film is wet. Another disadvantage of the Dresen et al. method is the increase in cost of adding and applying the integral and continuous layer of elastomeric material by coextrusion, lamination, adhesion, or heat application. The elastomer film of Dresen et al. generally extends across the entire substrate plastic sheet.
OBJECTS OF INVENTION
It is therefore an object of the present invention to provide a new method of imparting antislip properties to thermoformed plastic surfaces, which increases frictional forces and the coefficient of friction for wet as well as dry surfaces. An advantage of the invention is that it imparts a practical coefficient of friction substantially twice that of the closest prior art antislip surface for both wet and dry surfaces.
Another object of the invention is to increase the practical coefficient of friction and frictional force on thermoformed plastic surfaces by means of increased three dimensional macroscopic surface relief, asperities, and roughness. This is to be accomplished with hard and tough materials preferably with viscoelastic or elastomeric properties and with a hardness that is not brittle or sharp. The new antislip surface imparted by the invention is suitable for bare feet and can be applied in both dry and wet environments such as swimming pools and swimming pool areas, bathtubs, showers, and bathrooms.
A further object of the invention is to impart antislip propertie
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Cullivan Edward E.
Sturtevant Thomas M.
Bahta Abraham
Custom Plastics Molding, Inc.
Fasse W. F.
Fasse W. G.
Hess Bruce H.
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