“How can I reverse adhesive crystallization? Will the adhesive be compromised in any way?”
Only a very small number of adhesives are susceptible to crystallization and the likelihood of this phenomenon actually occurring is slight. If you do experience crystallization, heat will reverse the process and restore the adhesive to its liquid state with no loss in performance. There is no effect on strength, viscosity, or any other adhesives property. Tests performed at Dymax indicate that heating the original container of crystallized adhesive (in an oven or in a warm-water bath) to 100°F (adhesive temperature) will return the adhesive to its uncrystallized, liquid state. The adhesive will reach 100°F in approximately 2 to 3 hours depending on container size. For consistent dispensing, the adhesive should be allowed to return to room temperature. We would also recommend that you purge any dispensing reservoirs, lines, valves, and needles before any prolonged periods of production shutdown (i.e., weekends, shutdowns, etc.). This will help prevent adhesive crystallization.
“We are looking for a good adhesive to pot Nitinol or Titanium wire into a hole in a Noryl device. The hole is 0.156″, while the wire is 0.125″. We are looking for an adhesive that can stand up to re-sterilization using various methods of sterilization including autoclave and EtO, and that will also fill the gaps well. Can you recommend an adhesive?”
If the number of sterilization cycles is limited to a few you may be able to utilize a light-curable adhesive for your application. Dymax 1128A-M is a medical-grade adhesive that cures with UV and visible light, and exhibits good adhesion to a variety of metals. Adhesion to the Noryl will have to be tested.
If more than 10 cycles of autoclave sterilization are required then the best choice of adhesive will be either a heat-curable or two-part epoxy. Masterbond and Epotec offers a variety of materials that are medical grade and suitable for repeatable sterilization.
“Can you suggest a medium-viscosity adhesive that is well suited for metal-to-metal bonding?”
“We are currently using Dymax 1184-M, M-B, and V for most applications. However, we’ve found out that they are not well suited for bonding metal to metal, partly because the cured hardness is too high and partly because the UV light cannot penetrate through metal seams.”
For metal-to-metal joints I would suggest looking at traditional epoxies rather than light-curable acrylates.
Epotec and Master Bond Inc. offer epoxies in medical-grade versions. There is an old article that describes the impact of Sterrad low-temperature hydrogen-peroxide-gas plasma on several adhesives. The article, along with the results, can be viewed at: http://www.mddionline.com/article/compatibility-medical-devices-and-materials-low-temperature-hydrogen-peroxide-gas-plasma.
According to the results in the article, some two-part epoxies from Epotec have a moderate compatibility with Sterrad.