"Hello, I am using DYMAX 140-M to bond ABS to stainless steel. The product will be sold sterile in a Tyvek and LDPE/PET laminate pouch. Is there any data that shows the adhesive will not interact with the packaging in a way that could compromise the sterile barrier as the product sits on the shelf?"
Unfortunately we do not have data as specific as this. With so many applications around the world, and with so many substrates and packaging options being used, we have not attempted to determine the effects of cured adhesive in contact with the device packaging. The medical adhesives are usually tested for contact with blood, skin, muscular implant, etc., per ISO 10993/USP Class VI procedures, all with good results. If the material is cured properly, then after cure it is considered a solid plastic (urethane/acrylic type). We do not use any type of plasticizers or migrating materials that could compromise the integrity of the sterile barrier.
"We use a lot of RTV adhesives. Every lot is tested by QA. Last week we found out that in one of our components the adhesive did not cure at all. The RTV is one component and it adheres metal to ceramic. It has holes for air to penetrate. Even after opening the bond and exposing it for one week it still did not cure. What could be the reason for not curing?"
RTV silicone adhesives rely on moisture and humidity in the air to cure properly. Generally the conditions have to be 40-60% RH, but can extend down to 20%, and up to 70% in certain cases. The moisture in the air reacts with the stabilizer in the RTV, and once the stabilizer is removed, the adhesive can cure fully. In a very high-humidity environment, the humidity in the air can saturate the surface of the RTV, and effectively seal it off, limiting the penetration of the humidity to deeper levels. If you have a thick bond line or cross section of material, it may take longer than one week to cure fully. The silicone manufacturers generally set a 5-7 day cure schedule for RTV’s before they can test the physical properties in a thick slab of material, and that’s with the condition of 40-60%. If you have a 70% RH condition during the summer time, it may take longer, or disrupt the cure enough to appear gummy or semi-cured. Acidic surfaces may also cause problems with the cure mechanism.
Another avenue to explore: Was this failure linked to just one lot of material? And was it 100% failure for this lot, or 1% failure of one tube within the lot? These answers can lead the manufacture of the RTV to help determine the root cause of the failure.