“I want to find an epoxy that can bond two pieces of polycarbonate materials and be sterilized using autoclave. We tried using epoxy 353ND from Epoxy Technology but it is very difficult to cure completely, and after the sterilization process, the epoxy failed.”

Similar to light-curable adhesives, polycarbonate is usually not suitable for repeated autoclaving cycles. If a strong bond between the two pieces of polycarbonate is achieved, 1-5 cycles may be possible without damaging the adhesive and the polycarbonate.

There are several light-curable adhesives for polycarbonate available that are also approved for medical applications. One example is Dymax 1161-M, which I recommend for further testing with your application.

Adhesives, Medical autoclave-resistant adhesive, bond PC, bond polycarbonate, epoxy, plastic bonder, Plastic Bonding

“I am interested in a low-viscosity epoxy (<100 cp) with good adhesion to ceramics and stainless steel. The objective is to seal a small metal sensor inside a ceramic casing at room temperature. There is no contact with the patient. What type of epoxy do you recommend?"

Based on the substrates, ceramic and stainless steel, and the room-temperature requirements, I would recommend looking at a cyanoacrylate (instant adhesive) or a two-part epoxy.

Cyanoacrylates are available in very low viscosities. You may want to evaluate the DYMAX 222 Series which offers cyanoacrylates in a variety of viscosities. Low-viscosity epoxies are rare. One option could be two-part epoxy 301 from EPO-TEK, which is 100-200 cP.

Adhesives adhere metal to ceramic, bond ceramic, bond metal, Cyanoacrylates, epoxy, low viscosity adhesive, stainless steel

“We use two-part epoxies and UV-curable cements to seal Viton- or PVC-bending rubber onto the distal end of flexible endoscopes. Our current epoxy works well when it is sterilized using Steris or glutaraldehyde solutions. With the introduction of Sterrad H2O2 plasma processes, the epoxy fails after 20 to 30 cycles. What do you recommend that will hold up to more than 100 cycles?”

When ASP introduced Sterrad low-temperature hydrogen peroxide gas plasma, they tested many UV-curable adhesives and epoxies from different suppliers. The results showed that many adhesives were compatible and did not exhibit any material damage after 200 cycles. But some products were not compatible with this sterilization method. The article with the results can be viewed here: http://www.mddionline.com/article/compatibility-medical-devices-and-materials-low-temperature-hydrogen-peroxide-gas-plasma.

Since this article is more than 10 years old, some products may not be available anymore, but it is a helpful guide to identifying the most suitable product.

Adhesives Adhesives, bond failure, bonding rubber, epoxy, light-curable adhesives, PVC-bending rubber, Sterrad H202 plasma processes, uv-curable adhesive, Viton-bending rubber

“Do you have a list or can you point me to a list of adhesives and epoxies that are compatible with mineral oil? These would be ones that do not break down or release their adhesiveness when mineral oil passes over the adhesive/epoxy. Along those lines, which materials are better/best for tubing carrying mineral oil?”

The table below was provided courtesy of Cole Parmer. There may be other chemical compatibility charts available. You can rank various adhesives into different chemical categories, such as urethane, epoxy, or silicone, and should follow the basic trends listed below. For Example: DYMAX 1187-M light-curable adhesive is classified as a Urethane Acrylate adhesive family of chemicals. Evaluation of specific adhesives for a given set of substrates should be evaluated fully.

Explanation of footnotes
1. Satisfactory to 72°F (22°C)
2. Satisfactory to 120°F (48°C)

Ratings - Chemical Effect
• A = Excellent
• B = Good - Minor effect, slight corrosion or discoloration
• C = Fair - Moderate effect, not recommended for continuous use. Softening, loss of strength, swelling may occur
• D = Severe effect - Not recommended for ANY use
• N/A = Information not available

Adhesives Adhesives, Epoxies, epoxy, mineral oil compatibility, UV Light Curing Adhesive

"In my application I have a process where I apply UV adhesive between two pieces of plastic and I am seeing a short contraction period followed by a longer expansion period. Is it possible for UV adhesive to behave this way? How much does UV adhesive shrink during cure? Could this cause a pulling force between two plastic materials? If under an opposite force could the UV adhesive relax and expand somewhat?"

When light-curable adhesives cure, whether curing with UV light or visible light, crosslinks are forming between polymer chains. This pulls the chemical chains closer to each other very rapidly. We typically see a 1-2% linear shrinkage, which could translate into a 2-5% volumetric shrinkage. This may stress some plastics or optical components. There is a relaxation effect, usually over the next few hours or overnight, where the chains relax slightly as they rotate into an optimum alignment. In the spirit of valentine’s day – polymer chains like to spoon together and snuggle. If they are at odd angles to each other, they are still touching, but want to find that alignment where they are in the same direction and bending the same way. Chemical bonds can stretch and spin around their axes and allow for this relaxation. Also good to note, a product with a low modulus will stretch easier under stress, and a product with a very high modulus will not stretch much at all. A silicone (on one extreme) can have a modulus as low as 300 psi, whereas an epoxy can have a modulus as high as 2,000,000 psi. Many UV-curable adhesives are urethane acrylates and can vary in their modulus’ over a very wide range. The product data sheet should list this value.

Adhesives, Medical, Structural bonds, chemical chains, contraction, crosslinks, cure with visible light, curing with uv light, epoxy, expand, expansion, high modulus, Light Curable Adhesive, light cure adhesive, linear shrinkage, low modulus, mechanical properties, opposite force, optimum alignment, polymer chains, pulling force, relax, shrink curing cure, shrinkage, silicone, stress, urethane acrylates, uv adhesive, uv adhesives, uv-curable adhesives, visible light curing, volumetric shrinkage

"I need an epoxy to join two BK7 glass parts together. Gap is around 0.2mm. Light will cross the interface. Reasonable index match to the glass required. Low stress/shrinkage so it doesn’t distort the parts please. Viscosity not too runny, as we want it to stay in place prior to cure."

Optical glass-bonding adhesives are available that have good adhesion to BK7 Glass, a close refractive-index match to the glass, low shrinkage (low modulus), and moderate viscosity to avoid running. Light-curable adhesives like OP-29, which is a one-part adhesive from DYMAX, are available exclusively through Fiber Optic Center. FOC also carries various 2 two-part epoxies or 1 one-part frozen epoxies which should meet your requirements. An alternative source would be to visit the Edmund Scientific website and review their adhesive selections. Epotek 353-ND and 353-T epoxy are also widely used in the glass-bonding/optical adhesives market.

Adhesives, Structural BK7 glass, Edmund Scientific, Epotek, epoxy, Fiber Optic Center, gap fill, gap filling, glass bonding, glass-bonding optical adhesives, Light Curable Adhesive, light-curable adhesives, low modulus, low shrinkage, low stress, moderate viscosity, one-part adhesive, one-part frozen epoxies, optical adhesive, Optical Bonding, optical glass bonding adhesive, refractive index, two-part epoxies

"I have an application where we would like to cover the edge of a silicon die (that has been first tacked in place with epoxy that has been cured to a Valox/PBT base) with an uncured epoxy. Then add additional epoxy to a second bond location that ultimately bonds the Valox base to a Valox cover that has a slight press fit, covering the silicon die. After the press fit assembly, I would like to light or UV cure through the cover plate, causing both applications to cure. By both applications I am referring the bond line between the Valox cover plate & Valox base as well as the edge coating around the periphery of the silicon die, bonding it to the Valox base.

Are there any polymers that can transmit UV or light sufficiently to allow these types of cures? Is there a special light source required? Can the polymer be anything other then clear? Lastly, is there a medical-grade polymer that can achieve this?"

There are a couple of ways to handle this application.

There are a number of polymers that can be used for a cover plate that will let light through, whether UV or visible light. One way is to use a tinted plastic like polycarbonate or acrylic. Tinting the plastic with a dark blue dye will create the "illusion" of being opaque, but will let the proper wavelengths through the plastic to allow it to cure. Finding the right balance of dye will be critical. One way to judge the impact of the dye in the plastic, or the transmission through the plastic, is to measure the intensity of light coming through the plastic from the light source. You can calculate a % loss of transmission through the plastic in both the UV and visible regions. Most adhesives want to see a minimum of 200 mW/cm², and some of the light sources on the market are emitting light of 20,000 mW/cm². Even if the plastic blocks off 90% UV light, and 70% visible light, this might be enough to allow it to cure. If the plastic compounder uses a pigment to augment the tint, make sure the level of pigment is low, and they use a white pigment like Titanium Dioxide. A good field test – if you hold the plastic up to the light and can see a shadow as you wave your hand behind it – you might have enough light coming through to cure the adhesives. Stay away from yellow-orange-red colors. Whites, blues, and greens are better. There are a number of medical grade adhesives that can be used for this application, and various curing lamps. I might recommend contacting DYMAX Application Engineering to arrange for some free samples and to discuss our Trial Rental/Lease Equipment program. www.dymax.com.

Adhesives, Medical Acrylic, curing lamps, epoxy, light cure, light cure lamp, light curing, light curing lamp, light transmitting polymer, medical grade adhesives, medical grade polymer, Medical-Grade Adhesive, pbt, plastic, Polycarbonate, polymers, silicone die, uv cure lamp, uv curing lamps, uv light cure, uv light curing, valox