“We are looking for a medical-grade adhesive for bonding PEBAX (72D MED) tubing to latex nature rubber. We need shore hardness of a UV adhesive below 50D after cured. What is the best adhesive for this application? Also, which pre-surface treatment is suitable for PEBAX?

We also need a medical-grade adhesive for bonding PEBAX (72D MED) tubing to a colored ABS hub. Which fast setting adhesive is suitable for this?”

Latex nature rubber can typically be bonded with cyanoacrylates, also referred to as Super Glue. The Dymax medical grade 222 series cyanoacrylates might be a good place to start.

For bonding PEBAX I would suggest looking at Dymax 208-CTH-F, which is a medical grade, light-curable adhesive with shore D55. To combine PEBAX with latex or colored ABS, light-curable adhesives might not be suitable due to low adhesion to latex and problems with light curing through the colored ABS hub. Therefore, a cyanoacrylate is most likely the adhesive of choice.

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“I am trying to adhere a Polyethylene (PE) foam material onto a Polyethylene (PE) rigid, smooth plastic material. I prep both surfaces with a primer (Loctite 7701) before dispensing the adhesive, which is Loctite’s 4011 cyanoacrylate medical-grade adhesive. The adhesive is anchoring or sticking really well to the PE foam, but not the rigid plastic. They are both PE materials and I am not sure why it would adhere to one and not the other.

Are there different primers that vary in performance?”

One reason why the adhesive might stick better to the foamed Polyethylene (PE) is its larger surface. Due to the holes and grooves, adhesives in general can hold on better and achieve a mechanical lock.

According to the suppliers web site, the primer you are using is recommended for PE. If it is not providing the desired results, you may want to look into another surface treatment method such as plasma or corona, which adds polar groups to the surface and usually results in higher bond strengths.

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“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).

Adhesives adhere plastic to metal, Cyanoacrylates, Dissimilar Substrates, metal bonding, 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.

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“Which type of cyanoacrylate can be used for bonding skin/tissue together instead of suturing small wounds or incisions? Does DYMAX supply such a material? “

There are four types of cyanoacrylates. Two of them can be used for closing wounds and are available from different suppliers:

1. Butyl cyanoacrylate is used to bond skin and close wounds and is available from Henkel (Indermil), Advanced Medical Solutions Group (LiquiBand), and B. Braun (Histoacryl). All versions are FDA approved.
2. Octyl cyanoacrylate is a newer-generation cyanoacrylate for bonding skin and closing wounds. It is supposed to provide higher breaking strength and be less irritating to skin than the butyl-type adhesive. This type of cyanoacrylate is available from Adhezion Biomedical (SurgiSeal), Ethicon (Dermabond), and Chemence Medical Products (derma+flex QS). All products are FDA approved.
3. Ethyl cyanoacrylate is the most commonly used adhesive for assembly purposes and the type of cyanoacrylate supplied by DYMAX.
4. Methyl cyanoacrylate is used for assembly purposes.

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“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.

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"I have an application bonding opaque parts with a Cyanoacrylate (Super Glue Type). There is much surface area and I have a very good bond. Will Gamma Sterilization effect my bond strength?"

Most cyanoacrylates will survive 1x, 2x, and sometimes even 3x gamma sterilization without a significant impact on bond strength. Repeated Gamma sterilization will start to add additional crosslinking, which will start to reduce elongation. As most cyanoacrylates are already brittle materials (depending on the grade), the adhesive may become even more brittle. Drop tests, impact testing, or tensile testing may be a good indicator of the final impact on your bond strength.

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“I need a medical-grade adhesive to bond Ultem material to stainless steel (SS). This product will be a reusable medical product that will be autoclaved for 30 minutes @ 250° F”

To bond materials like Ultem and stainless steel, for a reusable device that will see autoclave conditions, the right choice in adhesives is important. As a general category, acrylates, urethanes, and cyanoacrylates will survive only limited autoclaving. Epoxies and silicones will have better success. Ultem is a difficult material, but with proper evaluation you might find a successful candidate. Silicone materials are available from companies like Dow Corning, Momentive, NuSil, and Wacker. Epoxy materials can be obtained from Epoxy Technology, Henkel/Loctite, and numerous others. Silicones will be softer and flex with the thermal stresses, while epoxies will be more rigid. It will ultimately depend on the part design and the number of autoclaving cycles the part will see.

Adhesives, Medical autoclave, CA's, Cyanoacrylates, Epoxies, Medical-Grade, silicones, stainless steel, ultem, urethanes

“Our application requires a watertight seal between FEP tubing (0.8 mm OD, 0.2 mm ID) and a borosilicate glass capillary (0.17 mm OD, 0.10 mm ID) with an overlap of 1-3 mm. This is part of a one-time use, disposable cartridge. We are currently using a 5 minute epoxy because the zero shrinkage is advantageous. The cure time, however, is not. We have tried UV-cure epoxy in the past for this joint but found that the epoxy did not cure inside the FEP tubing. Any suggestions?”

UV light-curable epoxies typically cure with the UV spectrum from 300-390 nm and do not make use of visible light to cure. With the semi-hidden bond described in the application above, switching to a visible-light-curable, acrylated-urethane adhesive would be worth trying. A visible-light-curable adhesive will allow more of the available light to hit the adhesive and cure deep within the FEP tubing.

An important issue with this application is that the borosilicate glass capillary will act like a light fiber.  It will take the light, carry it like a fiber-optic cable, not allow it to get to the adhesive (as it is bouncing the light internally within the glass), and move it past the bond area. The visible-light-curable adhesive should be exposed with high-intensity light. The adhesive should allow the light to penetrate into the gap.

One alternative to a visible-light-curable adhesive is a cyanoacrylate adhesive that could cure deep within the FEP tubing without light.  Due to the deep overlap area in this application, only the top surface would be exposed to water and could provide enough protection to create a water-tight seal.  Another alternative is a new product, DYMAX 9440 A/B, which is a light-curable silicone adhesive.  This material is unique in that you can expose the adhesive to light during dispensing and assembly and still have enough time to assemble the part before the material starts to set up.  DYMAX Applications Engineers can work with you one-on-one to discuss exact options and materials.

Medical, Structural Adhesives, CA's, Cyanoacrylates, Epoxies, FEP Tubing

Help needed:

“We are trying to glue a stack of coin cells to a .003 inch polyester substrate that has been printed with silver ink.  The bond must be electrically conductive. We’ve tried Loctite 401, 3M CA4, and 3M CA8.  Our problem is that the glue does not adhere consistently to the stainless steel can of the battery even when fixtured for 50 seconds. Roughing the surface of the battery has not helped.”

Recommendation:

A chemical primer on the surface of the stainless steel might help with the consistency. Cyanoacrylates generally cure with moisture in the air and on the surface. Controlling the environment goes a long way towards making a consistent process and getting consistent bond strength. Now we have to look at the level of moisture sitting on the surface of the stainless steel battery surface. Putting a primer onto the surface helps by putting a uniform concentration of -OH hydroxy groups on the surface. Be careful of how the operator is impacting your bonding process. Amazingly, an operator’s breath can apply a thin layer of moisture and help or hinder cure and adhesion. Plasma treatment systems can also be helpful in making a uniform bond line as it make a homogenous uniform surface each time. Cyanoacrylates are susceptible to these kinds of variations in the environment. If another alternative is required, two-part epoxies or one-part light curable acrylated urethanes or two-part acrylated urethanes (light and/or activator) are usually more consistent as they do not rely on environmental conditions for cure.

Structural Adhesives, CA's, Cyanoacrylates, Primer