Adhesives Frequently Asked Questions and Answers

What is a cyanoacrylate adhesive?

Cyanoacrylate is a clear, strong-bonding adhesive that dries very quickly. When a cyanoacrylate is in its uncured form, it is known as a monomer. After it is cured, it is known as a polymer (or plastic) resin. It is more commonly known as “super glue,” but the H.B. Fuller medical cyanoacrylate products offer customers a number of distinct features. The H.B. Fuller technical data sheets provide greater detail of technical specifications and product features.

Are there different types of cyanoacrylates?

Yes, the 4 major types of cyanoacrylate are:

  • 1. methyl 2-cyanoacrylate
  • 2. ethyl-2-cyanoacrylate (generically known as superglue)
  • 3. H.B. Fuller offers n-butyl cyanoacrylate (used in medical applications)
  • 4. H.B. Fuller offers 2-octyl cyanoacrylate (also used in medical applications)

How should I prepare the materials (or substrates) to be bonded before applying H.B. Fuller cyanoacrylates?

Substrate surfaces should be clean and dry before applying H.B. Fuller cyanoacrylates. All dirt, dust, oil, etc. should be removed.

What does “curing” mean for cyanoacrylate adhesives?

Curing for cyanoacrylates is the process where a chemical reaction takes place to form a harder and tougher linkage, creating a stronger adhesive backbone. H.B. Fuller medical cyanoacrylates offer two types of curing options:

  • 1. Air curing - curing process with the presence of moisture in the air
  • 2. UV light curing - curing using a UV light at designated wavelengths

What is the difference between “fixture time” and “cure time”?

Fixture time means the time before handling an application is possible. Partial strength cure means light handling can be done. And full cure is the time when the bond reaches full strength. H.B. Fuller medical cyanoacrylate adhesives gain most of their strength very quickly. Remaining strength takes a bit longer time. In scientific terms, fixture time is the ability of an adhesive to handle a 3kg shear load.

What is the average cure time of H.B. Fuller medical cyanoacrylates?

Cure times can vary depending on the type of cyanoacrylate used, from a few seconds to roughly 90 seconds for fixture, and from 8 to 24 hours for full curing. Cure times also depend on the substrates and their moisture absorption properties.

Can H.B. Fuller medical cyanoacrylates be used on flexible surfaces like medical tubing or hoses?

Yes, H.B. Fuller offers special cyanoacrylates that are rubber-toughened (M2240-05) for medical applications where movement is needed.

What is the benefit of H.B. Fuller rubber-toughened medical cyanoacrylate (M2240-05)?

H.B. Fuller rubber-toughened medical cyanoacrylate is strengthened by adding rubber to increase shear strength. Adding toughening agents with elastomeric properties, like rubber, help toughen the cyanoacrylate for higher strength applications, particularly for improved shear strength. H.B. Fuller rubber-toughened medical cyanoacrylate (M2240-05) takes slightly longer to cure.

What is the shelf life of H.B. Fuller medical cyanoacrylate products?

If properly stored and unopened, H.B. Fuller medical cyanoacrylate products can have a maximum shelf life of 12 months. If opened, and then closed properly and stored cleanly, H.B. Fuller cyanoacrylate products can last approximately 4 to 8 weeks. However, this can vary by product type, manufacturing process and storage environments.

How should H.B. Fuller medical cyanoacrylate products be stored?

H.B. Fuller medical cyanoacrylate products should be kept at room temperature (around 50-70 degrees Fahrenheit) and securely capped. They should also be kept out of direct sunlight to avoid excess heat.

How can the shelf life of H.B. Fuller medical cyanoacrylate products be maximized once opened?

To prolong the shelf life of opened bottles, make sure the cap is clean and securely sealed. Storing in an air-tight outer container that can prevent any internal moisture will also prolong shelf life.

How should H.B. Fuller medical cyanoacrylates be removed from substrates?

Care should be taken when applying H.B. Fuller medical cyanoacrylates, as removal can be difficult. To remove H.B. Fuller medical cyanoacrylates from substrates, use a special remover like acetone. Care should be taken when applying to plastic as well, as the remover can eat away at the base material in the same way it removes the glue.

Are there some substrates that are difficult to adhere?

For substrates that customers find difficult to bond, H.B. Fuller’s Adhesion Promoting Primer 6070 can enhance adhesion.

What is viscosity? Why is it important for H.B. Fuller medical cyanoacrylates?

Viscosity is the degree of fluidity of the adhesive in its non-cured state. A highly viscous cyanoacrylate will not run (like molasses or whipped cream). A low viscosity fluid is very liquid (like oil lubricants or water). Most cyanoacrylates are very fluid (low viscosity).

What is blooming?

Bloom or blooming is a whitish or rainbow-colored residue left after bonding. Blooming occurs when un-reacted cyanoacrylate particles (monomers) evaporate, then once airborne, react with surrounding moisture and return to the bond surface. This leaves a whitish residue, which is not aesthetically pleasing, but it does not affect the bond in any significant way. In applications where blooming is considered detrimental, H.B. Fuller medical low bloom cyanoacrylates should be used (M5005, M5008, M5100).

What is flash cure or UV curing?

Sometimes customers require quicker curing options. H.B. Fuller medical UV-curing acrylics (U304, U305, U307) cure at extremely fast rates, within seconds, when exposed to UV light.

Are H.B. Fuller medical cyanoacrylates tested for skin irritation and skin sensitivity?

Yes, H.B. Fuller medical cyanoacrylate products follow stringent ISO-10993-5 test methods. Testing is done using independent labs and supporting documentation is provided upon request.

Are H.B. Fuller medical cyanoacrylates tested for systemic toxicity?

Yes, H.B. Fuller medical cyanoacrylate products follow stringent ISO-10993-5 test methods. Testing is done using independent labs and supporting documentation is provided upon request.

Are H.B. Fuller adhesives REACH and RoHS-3 compliant?

Yes, documents are provided upon request.

Are there any real-time aging studies available for H.B. Fuller medical cyanoacrylates?

Yes. However, these studies are held confidential under the terms agreed to with our other customers.

What methods of sterilization can be tested with H.B. Fuller adhesives (e.g., EtO, gamma, autoclave)?

There are many variables to this question. The customer can test for all these methods of sterilization, and the results can vary greatly depending on the adhesive, substrates, application, etc.

What studies have been completed to determine the impact of sterilization or autoclaving?

These studies are held confidential under the terms agreed to with our other customers. Because of the wide variety of substrates, joint design and environmental conditions, customers should perform their own studies to determine device functionality as it relates to the performance of the adhesive post sterilization.