“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.
“I need to bond a plastic cap to an alloy/some type of metal shaft. The application is really similar to the two bottom joysticks of a playstation controller where you have the plastic cap that bonds on the resistive joysticks made of an alloy/some type of metal shaft. Any ideas about what adhesive might work best?”
Without knowing what the plastic is, the size and what type of environment this will be exposed to, it is difficult to make an accurate recommendation. However, based on what you provided we would recommend looking at a cyanoacrylate (instant adhesive).
“I am trying to bond 304 stainless steel to 304 stainless steel without welding. A strip of stainless steel is put into place once the device is completely assembled and welding would damage sensitive electronic components. The strip of stainless steel is currently held in place with high bond-strength double-sided tape with foam between the adhesive layers. The foam helps the strip to take its shape over slight surface variations in the welded cabinet it is being affixed to. The problem is that the foam can be shifted over allowing access to what is behind the strip. Pry bars have then been used to gain access into the device. It has been difficult to find an adhesive that can allow for surface irregularities. The adhesive must be able to withstand outdoor temperature extremes, moisture, and UV since this device can be permanently installed anywhere. The adhesive must also have other special properties because the strip is installed vertically to the cabinet and it is done on a shop floor where there are a lot of people around. Any ideas?”
For such extreme environment requirements and gap configuration, a 2-part epoxy could possibly be the best solutions for this application.
“We are using UV light-curable adhesive to bond a polycarbonate hub to the passivated stainless steel hypotube. We encountered a leakage issue during our in-process air-leak test. Confirmation of the leak happened at the interface between the adhesive and the hypotube when injected with a colored dye. Prior to dye injection, “delamination” could be seen between the adhesive and hypotube. We tried appying primer on the hypotube, wiping the hypotube with IPA, and using a longer curing time, but none of these steps helped to eliminate the “delamination” issue.
What do you think is the cause of this problem and the solution?”
If contamination has been ruled out, delamination is most likely related to uneven stresses within the adhesive joint. I suggest looking at the adhesive, viscosity, bond gap, and curing process.
Are the adhesive and the viscosity appropriate for this application and given bond gap? UV light-curable adhesives shrink during the curing process and may pull away from the surface they have less adhesion to. The larger the bond gap, the more likely we will see air bubbles or delamination. In such a case I would try an adhesive with lower shrinkage or a filled, higher viscosity adhesive. Suitable products from DYMAX are 1180-M and 1180-M-T-UR, which are the higher viscosity versions for larger bond gaps.
You mentioned you tried a longer curing time; did you also explore curing with different intensities? I would recommend trying a shorter light exposure at a higher intensity and a longer exposure at a lower intensity.
Do you cure the adhesive from the top or from the side? If you cure from the side and use a UV spot lamp equipped with one or two lightguides, there is a risk of introducing uneven stress due to the shrinkage of the adhesive. The areas not directly exposed to the light often exhibit delamination or airbubbles in the bond joint. In such a case I would recommend using a 3- or 4-pole lightguide instead.
“What type of adhesive would I use to bond latex and latex-free rubber to brass?”
Latex rubber can usually be bonded with cyanoacrylate, commonly referred to as super glue. In most cases cyanoacrylates have excellent adhesion to brass. Latex-free rubber can include any number of types of rubber, from synthetic rubber, butyl rubbers, and isoprene, to even silicone, so I can not make a recommendation right now. However, cyanoacrylates would be a good starting place. Cyanoacrylates come in different viscosities such as low water-like viscosities of 20 or 50 cP, higher viscosity materials like 500 cP or 1,000 cP, and all the way up to GEL viscosities. Cyanoacrylates also come in different grades like low odor, low bloom, surface insensitive, and rubber toughened for better impact resistance. DYMAX 222/100, which is a low odor/low bloom cyanoacrylate, might be a good place to start, and then you can refine the adhesive selection from there.