One current application which illustrates the benefits available from the new photocuring technology is the bonding of a lens to the reflector of a fog lamp used on several well known sport utility vehicles and light pick up trucks. A supplier to a major US automotive manufacturer was using a 2 part silicone for bonding the lens to the reflector. Before parts could be QC tested, they needed to sit for 24hr to cure completely resulting in a substantial `risk cost’ before those parts could be verified as effectively bonded and sealed.
Besides a 10% reject rate due to `leakers’ and/or a wavy, inconsistent and aesthetically unacceptable bond line, the silicone adhesive required daily purging of the feed lines to prevent clogging. Variable cure time presented an inconvenient inconsistency and solvent removal and disposal due to the daily line purging simply added to the hidden costs of using the silicone.
A UV/visible curing process provided by Dymax solved all of the above, and more importantly, led to the development of a better fog lamp. Because of the structural strength of the UV adhesive, less material is needed to meet the strength and durability requirements of the assembly. The engineers redesigned a smaller adhesive channel and increased the reflector area. The increase in reflective area led to a brighter lamp.
Because of the reology of the UV/visible adhesive, dispensing, flowing and wetting of the polycarbonate channel occurred easily and the resulting bond and seal virtually eliminated `leakers’. Bond line appearance was aesthetically acceptable because the adhesive was virtually invisible. Because of the instant UV/visible cure, 100% in-line quality testing could be done immediately resulting in zero untested work in process. No cleaning of the lines from day to day is required as the single component UV adhesive is neither affected by atmospheric moisture, nor oxygen, nor does it have a measurable pot life.