TWI Industrial Member Report Summary 956/2010
by T Colombier
Dissimilar materials joining in the medical industry has been a common practice for a few years. Although traditional biocompatible metals such as titanium and cobalt chrome alloys are still used in many medical applications, the industry is manifesting a lot of interest for biocompatible polymers. New biocompatible materials such as the thermoplastic PEEK-OPTIMA® have emerged and they have been demonstrating valuable properties for orthopaedic medical implants. PEEK-OPTIMA is manufactured and supplied by Invibio Ltd, a Member company of TWI. In the past few years TWI and Invibio Ltd have worked together on projects involving the joining of PEEK-OPTIMA.
In the medical industry, the joining of PEEK-OPTIMA to itself or to implantable grades metals is usually achieved by adhesive bonding. Adhesives meeting medical regulatory requirements (eg USP Class IV) have been developed for these specific applications and Loctite® 4061 is one of them.
A previous study between Invibio Ltd and TWI (Report in Appendix A) investigated the influence of various surface treatments on the mechanical properties of the dissimilar joints adhesively bonded with different types of medical grade adhesives. Loctite® 4061 was selected as the adhesive giving the best lap shear strength (LSS) of the joints. The metal-polymer joints were titanium-PEEK-OPTIMA and cobalt chrome-PEEK-OPTIMA. Following this study, it was suggested that the next stage of the analysis would be to investigate the effect of the sterilisation on the strength of the joints. The sterilisation process being a necessary operation to decontaminate medical devices, it was seen to be essential to identify whether the mechanical properties and performance of the joint could be affected by this operation. The work presented in this report summarises this investigation.
Evaluate the effect of the gamma sterilisation process on PEEK-OPTIMA to titanium and PEEK-OPTIMA to cobalt chrome alloy joints bonded with Loctite® 4061 adhesive.