A NEW TAILORED UV BASED SURFACE ACTIVATION METHOD FOR BONDING TO THERMOPLASTICS

摘要

The constant trend to optimize the costs of raw materials and related processing costs has accelerated the use of thermoplastic composites as alternatives to traditional thermoset composites in the Aerospace Industry. While thermoplastics can be easily fused together above their melting temperatures, it is difficult to bond them to dissimilar substrates, including thermosets and aluminum. The high melting temperatures of engineered thermoplastics like Polyarylether Ketone family (350 – 430 °C) limit their process. Therefore, lower temperature bonding systems would be desirable.This paper discusses the development of a new, rapid UV pretreatment method that is especially tailored for thermoplastic composite materials out of the PAEK family allowing improved bonding to dissimilar substrates. Surface analysis was done by XPS, TOF-SIMS, and contact angle measurement. To evaluate the bond strength, fracture toughness (G1C) and flatwise tension tests were conducted in a side by side comparison with a standard plasma activation method.XPS analysis after 10-20 seconds of pretreatment with the PAEK specific tailored method showed a significant increase of oxygen content by about 10%, TOF-SIMS analysis revealed a large number of new oxygen containing functional groups which increase polarity and wettability of the thermoplastic surface. This new surface treatment method led to a significant improvement in bonding of PAEK thermoplastic composite substrates verified by mechanical test results. This method offers new opportunities for fast and safe bonding to the thermoplastic materials resulting in excellent bond strength comparable with plasma pretreatment.