By Liz White, UT staffLeverkusen, Germany-Bonding between metals and plastics has been improved as a result of the development of thermoactivated adhesives using innovative raw materials by Bayer MaterialScience AG. The technique allows bonding to be delayed after an adhesive layer has been applied, and BMS foresees broader use, perhaps in bonding textiles to other materials in the automotive sector. The adhesive can be formulated for an extended range of applications and "join metal and plastic better than ever before thanks to a waterborne dispersion layer," claimed the materials company, in a 6 March announcement.A new latent-reactive precoating for metals or other substrates has allowed BMS's Coatings, Adhesives, Sealants Business Unit to succeed "for the first time in creating a force transmitting adhesive bond to plastic melts," the group continued. Central to this achievement are thermoactivated adhesives formulated with BMS's Dispercoll U line of polyurethane-based products. Disparate materials such as metals and plastics can be joined more effectively in future, claims BMS. Thermoctivated adhesives offer numerous advantages over conventional joining methods. Previously, coated or uncoated metal and thermoplastics, for example, could only be bonded by "a positive connection between the components brought about by an injection moulding process."Now a layer of the waterborne, latent-reactive PU dispersion less than 100 um thick can be applied to an insert and dried some time before the bonding. This layer remains stable and block-free at room temperature, says BMS. Later, during injection moulding or extrusion, the hot plastic melt of the hybrid partner initiates the bonding. One useful result of this new method is that component makers can apply the adhesive but defer production of the adhesive bond until later, or even carry it out at another location, said BMS. Bayer MaterialScience said it can "also imagine the use of textiles or films applied via back injection, for example in the automobile industry." "The development of this novel bonding technique has positioned us as a source of ideas for the relevant industrial sectors," said Dr Horst Stepanski of the CAS Business Development department. "We are now very interested in seeing how much of this sticks with our contacts following this initial step."
