Plenty of TPEs can bond to standard nylon 6 and 66 nowadays. "But modified nylons are a different story," notes Malar Shetty, applications group leader for GLS Corp. That's why, two years ago, GLS rolled out new SEBS-based elastomers that not only worked with unmodified nylons but also with those that contained high glass loadings and modifiers to improve impact and temperature resistance. "We came up with one type of TPE that addressed the many different types of nylons," says Shetty. Bond strengths between the elastomer and nylon substrates typically ranged from about 18 to 23 pli, which are far higher values than many applications require. And these Versaflex 6100 materials worked both with overmolding and insert molding processes, with the latter posing an extra degree of difficulty since the rigid insert part cools before the elastomer is shot over it. Earlier this year, GLS has commercialized its next-generation nylon bonding TPEs. These Versaflex 6200 materials offer two key improvements over the first generation: One is that the new grades, available in 60 and 75 Shore A versions, address even more modified nylons, particularly lubricated grades. The other is that the materials flow has been optimized to make molding a bit easier. As Shetty points out, the first generation was very high-flowing, so flash could be a problem in tools that weren't immaculately constructed or maintained. "The new materials have just enough flow to make molding easy but now so much that flash becomes a problem."
For more information on properties of the 60 Shore A grade, go to http://rbi.ims.ca/4933-536.