“Is there a UV-curable, medical-grade (safe to use in the body) biodegradable adhesive of any kind on the market right now? If not, would it be possible to formulate the adhesive?”
Dymax does not presently pursue implantable applications for our adhesives, and we are unaware of any adhesive on the market that would be biodegradable. Consequently, we cannot comment on the feasibility of such a product.
“Guidelines for Protecting Light-Sensitive Adhesives from Curing in Dispensing Equipment in Manufacturing Environments”
Unfortunately, manufacturing facilities that use standard fluorescent lighting sometimes have a problem with the polymerization of UV/Visible light-curable adhesives in dispenser tips and lines. The chemistry of these products make them extra sensitive to light, so extra measures must be taken to insure that unwanted polymerization does not occur.
To prevent this problem, manufacturers should shield needle tips and lines from light exposure. Incorporating lines that are black, opaque, polyethylene plastic will completely block light from the adhesive and eliminate the chances of unwanted polymerization. Dymax provides light-blocking materials for syringe needle tips. If these measures are insufficient and a process can’t be shielded through use of light-blocking materials, the fluorescent lamps in the facility could be retrofitted for existing incandescent and fluorescent fixtures.
“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.
“One of the materials I’m using has exhibited syneresis. What is the best way to reverse the syneresis?”
A few thickened adhesives (VT and GEL grades) occasionally exhibit syneresis. Syneresis appears as a thin film or puddles of low-viscosity adhesive on top of the thicker adhesive. Sour cream and yogurt are familiar products that also exhibit syneresis. The composition of the low-viscosity syneresis liquid is chemically identical to the thickened material. It has the same chemical and bonding properties but the viscosity is much lower.
Time and colder temperatures can promote syneresis. We would recommend using a First In, First Out (FIFO) inventory control. FIFO inventory control can help control the amount of time a product is stored before use. We would also suggest that syneresis-prone materials are not refrigerated. In fact, mild heating can reverse the syneresis in some products.
Once syneresis has occurred, mixing is the most common method of returning the mixture to a homogeneous state. Mixing can be accomplished with a traditional paddle or spatula (being careful to minimize air entrapment) or mixing can be accomplished through the use of a static mixer.
“I would like to attach 72D Pebax extruded tubing into the ID of a Polycarbonate tube. What is the appropriate gap-per-side if I want to use DYMAX 204-CTH UV- curable adhesive?”
The optimum gap size for UV bonding applications (in general) is 0.002-0.006 inches, or 0.05-0.15 mm. In catheter bonding applications, where a Pebax tube is being bonded into a Polycarbonate Y-connector, we often see bond gaps around 0.1 mm per side. The DYMAX 204-CTH-F family is a very good choice of products to use for this type of application and substrate combination. Another product to consider is 208-CTH-F.
“Can you recommend the most appropriate UV-curable adhesive to bond ABS connectors to polyurethane tubing in a medical device application? It is a polyether aromatic polyurethane tube to a transparent ABS connector.”
For this type of application I suggest trying DYMAX 1161-M. This adhesive cures with UV and visible light and exhibits good adhesion to ABS and PUR. It also fluoresces blue for quality purposes. If you are interested in See-Cure patented color-change technology, I would recommend DYMAX See-Cure 1201-M-SC. This product is blue and helps verify that enough adhesive has been dispensed. Upon exposure to UV/visible light, the adhesive turns clear to confirm complete cure.
“We need to glue an epoxy-coated magnet to a copper-clad FR4 PC board. The UV-cure glue needs to resist mechanical shock without cracking. Any Ideas?”
DYMAX offers 6-625-SV01-Rev-A, a flexible light-curable adhesive with secondary heat cure and activator cure capabilities for shadowed areas. Its high viscosity of 10,000 cps also enables it to be dispensed from the outside and act as an edge-bonding material.
“Can oxygen inhibition be removed from cured parts without damage to the fully-cured substrate area? We are looking to change our process to include a nitrogen blanket, but have many components that cannot be completed due to the tackiness on the outer surface.
We tried CRC Brakleen which effected the cured surface area as well as the tacky coating.”
First of all, I would like to refer to an older reply made regarding the inhibition of cure: http://mpmn.canon-experts.com/2009/03/
CRC Brakleen is a very strong cleaning agent that contains tetrachloroethylene and dichloromethane or ketone (depending on the packaging used). As you already noticed, these are chemicals that easily remove the tacky layer, but also dissolve the cured adhesive. If oxygen inhibition cannot be avoided, the tacky layer should be removed with an isopropyl alcohol (IPA) wipe. IPA is less aggressive and is commonly used for this purpose. We would always recommend a wipe rather than a soak.
“In our application we are looking for a light-curable silicone adhesive that cures within seconds, is not acidic, and does not outgas too much. Do you have suggestions? “
There are a few light-curable silicones on the market that are non-acidic. The tensile strength, and cohesion strength of most UV silicones on the market, is very low and although they may stick well to substrates, a bonded joint can usually be taken apart easily. The larger the surface area, the more suitable these products are for bonding or lamination applications.
“We are currently using your DYMAX 1-20323-W UV-curable epoxy on a piece of PVC Tubing. Is there a way to dissolve this epoxy without damaging the PVC? We want to remove this epoxy for re-work reasons.”
Fully cured UV-adhesives such as 1-20323-W are cross-linked, thermoset resins, which do not melt and may be difficult to remove from a substrate, especially if they stick very well to it.
For your removal purposes, I would recommend heat or chemical exposure to weaken and then remove adhesive bonds or coatings. It may be very difficult since PVC and the cured adhesive have similar limitations in terms of temperature and chemical resistance.
I suggest placing a part in an oven at 60°C (140°F) for 10 minutes and immediately apply a peel or cleavage force to the bond or coating. Next you can try to increase the temperature up to where the part will not be adversely affected.
There are several chemicals that will dissolve or swell 1-20323-W, such as Dichloromethane, MEK, and Acetone; however, these will also damage the PVC and may not be suitable for your specific needs. Using isopropyl alcohol (IPA) may be the only option in this particular case. A long soak in warm IPA with the help of an ultra sonic cleaner could be the last option if previously mentioned options did not provide desired results.