Disposable medical device assemblies require adhesives with strong, reliable, biocompatible medical liquid and sterilization-resistant properties. Adhesives for any application should be chosen with care, but medical adhesives should be selected with the utmost care. The variety of adhesives available can be bewildering. Adhesives come in such a wide variety of mechanical and handling properties that you may need to look high and low to find the best one for your application.
From our experience in the market, light-cure and cyanoacrylate adhesives (CA) are the most popular materials in medical bonding. You can also consider some epoxies and polyurethanes with specific applications.
Types of Medical Adhesives – Disposable device
- Light cure adhesives (UV and LED cure)
The most used adhesives in the medical industry are light-curing materials, including acrylics, silicones, and polyurethane.
The joint must be exposed to light for the light-cure materials to work. As a result, light-cure adhesives are generally used on devices made of clear plastics like polycarbonate or acrylic. Light-cure adhesives cure in under 30 seconds and stick well to metals, glass, and plastic. They also work well with automatic dispensing equipment.
Fluid monitoring and collection devices, needle assemblies, anesthesia masks, and tube sets are the most common devices assembled with light-cure adhesives.
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- Fast bonding- Cyanoacrylate adhesive
Moisture-curing cyanoacrylate is the second most popular adhesive for disposable medical devices. Cyanoacrylates (CA or super glue) are high-performance materials with high bond strength, quick cure time and highly resistant to a wide range of chemicals and solvents. They cure in the condition with no light and at room temperature. They cure through the reaction with moisture on the substrates. CA are compatible with automatic dispensers and can bond polyolefins and other difficult-to-bond substrates. They are one-component materials with viscosities ranging from a thin fluid to a thick gel.
However, cyanoacrylates have some drawbacks. They are naturally brittle, and moisture can lead to bond delamination and degradation. Like light-cure adhesives, they can be used to assemble the same types of devices. They are frequently used in catheter assembly.
- Epoxy adhesives
In medical assemblies, both one and two-component types are well employed. The ability of to withstand extremely high temperatures, including most sterilization techniques, is one of their most significant advantages. Epoxies adhere well to a wide range of substrates, including metals, glass, plastics, and other surfaces. The most common use of epoxies is in needle bonding. Besides, they are useful in potting applications where a larger volume of material is required.
- Polyurethane adhesives
Polyurethane adhesives are frequently used for structural bonding medical devices due to their high strength and flexibility. This is since medical polyurethane resin has excellent mechanical properties, making it an excellent choice for a wide range of medical device applications.
Furthermore, polyurethane adhesives are used in medical devices in potting applications because they have the desired properties for such applications, such as low shrinkage, low exotherm cure, and excellent adhesion to a wide range of substrates.
How to apply adhesives with suitable applications
- Needles and Syringes
Medical device adhesives are popular in needle assemblies in order to bond cannulas to hubs. To prevent fluids such as blood or medicine from leaking, it is critical that the cannula remains fixed and that this joint is well sealed.
Light Cure Acrylics (both UV cure and LED cure), One-Component Heat Cure Epoxies, and Light Cure Cyanoacrylates are the three most commonly used adhesive chemistries for needle bonding and manufacturing.
- Catheters
PVC, polyurethane, polycarbonate, and stainless steel are examples of medical device adhesives used to bond typical catheter materials. They are used in the most difficult applications, such as balloon to multi-lumen tubing, strain relief or balloon-to-tube transition, drug-eluting stents, and marker band bonding.
Light Cure Acrylics (UV and LED light cure), Cyanoacrylates, and Light Cure Silicones are the three most commonly used adhesive chemistries for catheter assembly.
- Tubes and Connectors
For the manufacture of tubes and connectors, light cure adhesives provide a performance combination of fast cure, proper adhesion, high strength, and adapted flexibility. Tubing is joined to fittings, connectors, adaptors, IV sets, blood collection sets, drug infusion sets, and feeding tubes using adhesives.
The main adhesives used for this application are Light Cure Acrylics, Light Cure Cyanoacrylates, and Light Cure Silicones.
- Blood Filtration
Polyurethanes, light cure acrylics, and epoxies are used in medical filtration applications such as oxygenators, dialyzers, and filters to bond and increase capacity.
This application has a wide range of requirements, including low viscosity for optimal fiber bundle penetration, high adhesion to plastic housings, controlled exotherm for low shrinkage, and process optimization recommendations (centrifuge and trim times).
Compulsory requirements for medical adhesives
Before releasing a product to the public, medical device manufacturers conduct extensive testing on the various materials that will comprise the device. This is done to determine whether the materials are safe. That’s why besides being sterilization resistant, solvent-free, and nontoxic after cure, adhesives must go through certain tests to be qualified for medical usage: biocompatibility testing and formulas testing (also known as lock-down policies).
- Biocompatibility test
Most suppliers have switched from the United States Pharmacopoeia (USP) Class VI standard to ISO-10993 for biocompatibility testing, which includes the following:
– Intracutaneous injection tests to assess the material’s irritability.
– Acute systemic injection tests to assess the material’s potential toxicity following a single-dose systemic injection.
– Cytotoxicity tests to determine the material’s biological reactivity to monolayer cell cultures.
– Hemocompatibility tests to determine the material’s hemolytic potential in the presence of rabbit blood. In vitro, hemocompatibility tests ensure that the extract of the test material does not harm the cellular components of blood.
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- Formulas test
The last thing a medical device manufacturer wants is for its adhesive formulation to be changed after launching on the market after the testing process. A significant change, such as a new raw material or manufacturing process, may necessitate resubmitting the product for approval.
To avoid this, suppliers must ensure that the formulation of adhesives will not change without notice by the formulas test. Similar to biocompatibility testing, this test differs from supplier to supplier. Customers should be notified if formulations may change so that they can take the necessary steps to ensure that the material continues to meet their needs.
