Dry structural adhesive films: a new bonding solution

摘要

In the transportation industry, emission reduction requirements are leading to a general rethink of body construction in order to optimize vehicle weight. Today, modern vehicle bodies are using multi-material body construction optimizing material properties for targeted functions. These materials are often difficult to weld, while assembly cycle time needs to be as short as possible. One solution to this challenge is the development of high-performance structural adhesives. In addition, structural adhesives distribute loads continuously along the bond line, reduce fatigue issues, can be applied directly to oily surfaces, and combine sealing and bonding in one product. Today, liquid or paste adhesives are most commonly used in these applications. L&L Products has recently developed heat-activated structural adhesives in dry film and tacky tape form (cf. Fig. 1). Structural adhesive films combine the advantages of liquid heat-activated structural adhesives and a physical form that allows perfect control of the quantity and placement of the adhesive. L&L Products' adhesive films are applied before final assembly, and can be used to bond large surfaces as in the case of composite reinforcements. The curing kinetics (cf. Fig. 2) of the film adhesives are optimized for e-coat oven bake temperatures, but adhesive films can be also activated and cured with external heat sources such as infra-red spot lights, hot stamp or induction. At temperatures higher than 190°C the adhesive film can be fully cured in less than one minute, permitting very fast assembly times. Significantly, due to their latent curing system, the films do not need to be stored in a refrigerated environment, offering a minimum shelf life of 6 months at room temperature.