From orthodontic bonding agents to wound closures, to gels for medical sensor pads, the term medical adhesive can refer to any product that is used to adhere or bond in a medical application. Medical adhesives can be categorized by application and adhesion method. Common applications include bandages, dental appliances, dental composites, wound closure, tissue repair, securing bone pins/screws, prosthetic assemblies and attachments, implants joints and connectors, medicinal patches, and medical sensor pads. The adhesion method refers to the way in which the adhesive is applied and the bond is activated. For example, pressure sensitive tapes (e.g. bandages) are bonded to the skin by applying pressure. Other medical adhesives, such as those used in dental applications, are activated by heat or UV light.
Medical adhesives can be tested for structural strength, adhesion properties, and environmental/chemical resistance. Structural strength tests include measurements in tension/compression and elongation. Examples of these tests in the medical field are the compressive load resistance of a plastic adhesive applied to a substrate (skin, ligament, muscle) or the elongation of self-adhering bandage wrap applied to a joint area.
Adhesion property tests include peel strength, bond strength, lap shear, tack strength, friction, and adhesive reusability. These tests are the most common and are relevant to almost every medical application. These tests determine how hard the adhesive is to apply and remove, how well it attaches to the substrate (skin, tissue, bone, implants, prosthetic devices, etc), and how long the product is able to maintain its adhesive properties (e.g. the reusability of a bandage).
Environmental/chemical resistance tests are used to measure the structural and adhesion properties of adhesives in different temperature, moisture, and chemical conditions. In medical applications, this normally refers to the human body. Through the use of temperature chambers and environmental baths, medical adhesive performance inside the human body can be simulated in vitro.
There are several ASTM and ISO testing standards that are relevant to medical adhesives. These include:
- ASTM D903 Peel or Stripping Strength of Adhesive Bonds
- ASTM D3330 Peel Adhesion of Pressure Sensitive Tape
- ASTM D1876 T-Peel Test
- ASTM D1002 Adhesive Lap Joint Shear Strength Test
- ASTM D6195 Adhesive Loop Tack Strength Test
- ASTM F2258 Tensile Strength of Tissue Adhesives
- ASTM F2458 Wound Closure Strength of Tissue Adhesives
- ASTM F2256 Strength Properties of Tissue Adhesive by T-Peel Loading
The equipment required to test medical adhesives will change depending on the test being performed. However, most medical adhesive tests will require:
- A servo-controlled (constant rate of motion) universal testing machine capable of tension/compression.
- A peel testing fixture (if performing an angled peel test).
- Grips and/or plates to secure the specimen (specimen defined as an adhesive and a substrate).
- A testing controller (software based or standalone) to control the testing machine actuator at the required rate and record/process test data (perform calculations and create testing reports).
- An environmental chamber or bath (optional).
ADMET has provided adhesive testing systems to leading medical device manufactures, universities and research laboratories. We offer a full range of adhesive testing systems featuring constant-rate-of-extension (CRE) and constant-rate-of-load (CRL) control, allowing you to perform a wide variety of adhesive tests to ASTM or ISO standards. ADMET systems will automatically perform and report all required calculations. Our wide range of fixtures, grips, and environmental chambers will accommodate nearly any application. Modifications to systems as well as custom fixtures can be designed for special applications.