“I understand DYMAX has a masking material that is biocompatible or had biocompatible testing done on it?”

DYMAX provides a selection of adhesives (http://www.dymax.com/products/medical/index.php) that have been tested according to ISO 10993 and are biocompatible in the cured stage.

A medical-grade material is typically not needed for temporary masking applications where the light-curable resin acts as a manufacturing aid only and is being removed before the end product is finalized.

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“Do you have an FDA-approved adhesive for artificial hearts (structural and non-structural adhesive)? Which standard is more relevant and which standard applies - ISO 10993, USP Class VI, or another standard?”

If you are referring to implantable artificial hearts, we have to pass. DYMAX adhesives have not been tested for prolonged or permanent implantation and are only intended for use in short-term (<29 days) or single-use disposable device applications. DYMAX does not authorize their use in long-term implant applications.

Polymerized DYMAX MD^® Medical Device adhesives are biocompatibility tested in accordance with ISO 10993 and/or USP Class VI. ISO 10993 is a newer, internationally accepted standard. The current DYMAX test protocol for medical adhesives contains the following studies:

• ISO 10993-4 Hemolysis
• ISO 10993-5 Cytotoxicity
• ISO 10993-6 Implantation 14 Days
• ISO 10993-10 Intracutaneous
• ISO 10993-11 Systemic Toxicity

Older DYMAX adhesives have been tested in accordance with USP Class VI, which consists of Systemic Toxicity, Intracutaneous and a 7-days Implantation Test. When comparing both standards, USP Class VI is included in and covered by ISO 10993.

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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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"Can you cure DYMAX Ultra Light-Weld^® 1161-M adhesive with just heat or does the adhesive need to be exposed to UV/Visible light?"

Unfortunately, products like Ultra Light-Weld^® 1161-M are designed to cure with UV and visible wavelengths of light only, and heat will not cause this material to cure. There are families of DYMAX products that are considered Multi-Cure^®, which have both UV/Visible light-curing capability as well as thermal-cure capability. I would recommend calling a DYMAX Applications Engineer to discuss the specifics of your application, so that we can recommend the right Multi-Cure^® adhesive for your application.

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"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.

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"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.

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"I have a lead wire containing a polyimide jacket. I need to bond the polyimide jacket to a titanium housing. The bond needs to provide a strain relief, and more importantly a fluid-tight seal. The adhesive needs to be rated for long-term implant use. Can you make an adhesive recommendation for this application?"

There are relatively few long-term implant adhesives on the market. NuSil Technology offers MED-2000, which is a one-component silicone RTV adhesive, and MED1-4213 is a two-component addition-cure silicone adhesive. Applied Silicone also offers long-term implant adhesives, such as P/N 40064. Since both companies offer other alternatives besides these, I would recommend contacting their respective sales/technical departments to discuss further.

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"I need inert and non-water absorbent adhesive film, with good sealing properties, to cover a surface (ceramic) already covered with a suspension of bacteria (dried). This set will be placed in a stomacher bag that contains culture media and the bacteria should be able to pass from the adhesive film to the media. It must be sterile or be able to be sterilized."

There are a few different options, depending on whether you want it to be sticky or non-sticky, or somewhere in between. Various silicone manufacturers or converters may offer cured silicone sheet in various durometers that would be inert and non-water absorbant. The lower the durometer (A-5 to A30), the better it will seal, but will be soft and “grabby” to the touch. Higher durometer silicone will be slightly easier to handle, but will not be as sticky or grabby as the lower durometer materials. You can go with an even lower durometer with silicone gels for better adhesion, but these need to be on a backing (similar to the tacky gel woundcare dressings or ouchless bandaids). Thin film PTFE or PTFE tape may also be an option. Many of these options will be sterilizable.

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"We have a segment of uncured adhesive inside a tube encapsulated with the adhesive DYMAX 204-CTH-F-VLV due to UV-opacity of the said tube’s segment. Does contact with uncured adhesive deteriorate properties of cured adhesive?"

Unfortunately, yes. Uncured adhesive will attack the bond line and the cured adhesive. The extent of deterioration is dependent on the area and volumes in contact with each other, and the duration of how long they are in contact. We would recommend sealing the tube, or removing the uncured adhesive if possible.

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"Is there a UV-curable adhesive that when cured conforms to USP Class VI and passes ISO 10993 requirements for permanent implant?"

Unfortunately, not that I am aware of. Technically, most light-curable adhesives are acrylated urethanes or epoxy-based systems, and would not survive permanent implantation. There are other hybrid light-curable technologies, but as far as I know none have been released technically for long-term implantation. In addition, the legal liability is too high for most applications. Perhaps something from the dental cement industry might be a suitable option.

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