Strength loss indicator for synthetic yarns

Abstract

A webbing formed of synthetic yarns having an indicator for indicating exposure to ultraviolet light which results in strength loss of said synthetic yarns. The strength loss indicator comprises a strip extending along at least a portion of the webbing. The strip includes a phosphorescent material that produces a glow when exposed to ultraviolet light. The phosphorescent material is adapted to lose its ability to produce a glow over time exposure to ultraviolet light. Advantageously, the ability to glow fades at a rate correlated to the rate of loss of tensile strength of said synthetic yarns due to ultraviolet light exposure to indicate the condition of the webbing.

1 . A webbing formed of synthetic yarns which lose strength due to exposure to ultraviolet light, said webbing including an indicator comprising: 
 a strip extending along at least a portion of said webbing;    said strip including phosphorescent material which produces a glow when exposed to ultraviolet light, said phosphorescent material losing its ability to produce a glow over time exposure to said ultraviolet light; whereby,    said loss of glow of said strip is correlated with a pre-determined loss of strength of said synthetic yarns.    
     
     
         2 . The webbing of  claim 1  wherein said webbing comprises one of woven, knitted, and non-woven synthetic yarns.  
     
     
         3 . The webbing of  claim 1  wherein said synthetic yarns are comprised of a thermoplastic polymer.  
     
     
         4 . The webbing of  claim 3  wherein said thermoplastic polymer is selected from the group consisting of polyamides, polyesters, polypropylene, polyethylene, polyacrylates, polycarbonates, polycyanoethylenes, polyacrylonitrides, polyvinyl chloride, polymethacrylics, polystyrene, polyurethane, acrylate resins, halogenated polymers, and mixtures and blends thereof.  
     
     
         5 . The webbing of  claim 1  wherein said webbing comprises one of a safety harness, a tie-down, and a sling web.  
     
     
         6 . The webbing of  claim 1  wherein said strip comprises at least one synthetic yarn which includes said phosphorescent material.  
     
     
         7 . The webbing of  claim 1  wherein said strip includes at least one polyester yarn coated with said phosphorescent material.  
     
     
         8 . The webbing of  claim 1  wherein said strip comprises a coating including said phosphorescent material on to at least one surface said webbing.  
     
     
         9 . The webbing of  claim 1  wherein said phosphorescent material includes a luminescent phosphor.  
     
     
         10 . A method of forming a webbing formed of synthetic yarns which incur strength loss over time due to exposure to ultraviolet rays with an indicator for determining the degree of said strength of said yarns over time, said method comprising: 
 fabricating said synthetic yarns into said webbing;    providing a phosphorescent which interacts for a selected time with ultraviolet rays to produce a glow;    correlating said selected time of said phosphorescent with said strength loss time of said yarns and incorporating said phosphorescent with said webbing in the form of a strip; whereby,    diminished glow of said phosphorescent containing strip represents diminished strength of said yarns.    
     
     
         11 . The method of  claim 10  providing said strip comprise at least one length wise yarn of said yarns coated with said phosphorescent.  
     
     
         12 . The method of  claim 10  providing said strip comprise a phosphorescent coating along at least one surface of said webbing.