“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.
“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.
"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.
"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.
"I need a recommendation of a medical grade non-cytotoxic UV adhesive for bonding together clear polystyrene moldings. What adhesive would you recommend? What is a simple but effective method to monitor if the curing reaction has gone to completion? Is there any dosimeter available to accurately measure the UV exposure? Would a post bake after UV curing help? Does anything "outgas" from the UV medical-grade acrylates during curing?"
Two options come to mind when looking for a medical-grade light-curable adhesive for polystyrene – 1201-M-SC and 1120-M-UR from DYMAX Corporation. These materials exhibit excellent adhesion to polystyrene, and are both ISO10993/USP Class VI tested. Product data sheets are available at www.dymax.com. One simple but effective method to monitor if the curing has gone to completion is incorporated into the 1201-M-SC product. This material uses a technology called "See-Cure", where the material starts off with a brilliant blue color, and as it cures changes to clear. This is an excellent visual indicator that complete cure has been achieved in all parts of the bond line. Other methods to determine state of cure include destructive testing of the components to measure tensile force, or a drop of adhesive at the bond-line surface and using this droplet to measure for tack/semi-cure (a go/no-go measurement observed by the presence or absence of adhesive transfer onto a gloved finger). More complex methods include microscope FTIR analysis of the adhesive to identify the presence of the double-bonds peak (on the spectrum) before cure, and the removal of the double-bond peak after cure.
Dosimeters are necessary to accurately measure light exposure, and there are different versions, with different sensors, that measure different parts of the UV and visible light spectrum. While most light-curable adhesives cure with a combination of UV-A, UV-B, UV-C, and visible light, it is often convenient to reference the UV-A light spectrum coming from the light source. UV-A is commonly referred to as 365 nm, but actually covers a range of approximately 320-395 nm. This can be measured with an ACCU-CAL™ 50. If the polystyrene is UV blocking, then you would have to rely on the visible light spectrum of the lamp. The ACCU-CAL™ 50V measures 395-465 nm. Both units can give you average intensity (mW/cm2), peak intensity, and total energy (Joules/cm2). Other options are available like the ACCU-CAL™ 50 LED, which was developed for special lamps (such as LED lights which only emit a single wavelength at either 385 nm or 405 nm) to integrate around the center of the lamp spectrum.
A post bake is not necessary on most adhesives, but there are a few adhesives with a peroxide thermal initiator, which can use heat to cure areas not able to see light.
In regard to the question on outgassing of UV light-curable adhesives during cure, it is sometimes observed that a small amount of smoke comes up from the adhesive surface during the cure step. This is typical, as the adhesive may emit trace amounts of some of the ingredients (or fractions of the ingredients) contained in the formulation while light is shining on the adhesive and cure is taking place. Sometimes this can be overcome by varying the intensity and duration of cure, as well as adhesive choice and light source. This does not happen when the adhesive is used between two surfaces. Proper ventilation can help remove this smoke. If the smoke deposits onto a spot or flood lamp, then periodic cleaning of the end of the lightguide or lamp housing should be done to remove the film that may form there, as this thin film can reduce the intensity at the bond line.