Choosing a Medical Device Adhesive

Medical device adhesives are ‘adhesives that are marketed to medical device manufacturers’. Unlike food grade adhesives, medical device adhesives contain no special approval from the FDA. Often, bio-compatibility testing is performed on the adhesive as a marketing tool to increase the buyer’s trust in the product. Types of bio-compatibility testing include cyto-toxicity, USP Class VI, and IS010993. Even then, the assessment does not replace the testing required of the device manufacturer by the FDA. Device manufacturers are required to prove that the device they manufacture is bio-compatible and effective.

The logical path is:
• Adhesives are tested for bio-compatibility after they are cured;
• Lack of proper curing can affect bio-compatibility;
• Curing occurs within the device manufacturer’s assembly process.

Therefore:
• Bio-compatibility can only be determined on the finished medical device.

Generally, the term ‘medical device adhesives’ refers to those adhesives used on medical devices that come into contact with the body, body fluids or delivery systems. As such, the adhesives are designed to bond the plastics and other materials common to the industry. So a UV curable adhesive used to bond an oxygen mask together is likely considered a medical device adhesive. But the epoxy, threadlockers and, structural acrylics used in the manufacture of an x-ray machine are not considered medical device adhesive. However, if you use the same epoxy used in the x-ray machine to bond a needle into the hub of a hypodermic needle…well, now there is a medical device adhesive!

So, choose the adhesive that meets your requirements, regardless of whether it is termed a medical device adhesive or not.

Adhesive Applications on Filter Assembly

Adhesive applications on filters are as diverse as the materials they filter. Here we have selected a few common applications:

Automotive Filters

> Seam Sealing
> Bonding Rubber Gaskets
> Bonding Filter Assembly to End Plates

Process Filters

> Sealing

AUTOMOTIVE FILTERS
Seam Sealing: Rolled seams are found in oil filters, fuel filers, and air filters. They are formed by cold rolling the edges of two metal flanges like the lid of a tin can. Generally the "can" is rotated while a stationary set of rollers moves in to crimp the can closed.

Anaerobic adhesives / sealants are prefered since they are more environmentally friendly, non flammable, 100% solids and lend themselves to automation. Anaerobics cure in the absence of oxygen and the presence of metal at room temperature.

Bonding Rubber Gaskets: Rubber gaskets are found on the base plates of most filters. Choosing an adhesive to attach these gaskets is largely dependent on the temperature and chemical resistance required of the filter. Both cyanoacrylates and epoxies are commonly used.

In automotive filters, cyanoacrylate adhesives are generally used to bond the gasket to the outside of the base plate as they resist upwards of the 200F requirement, and are oil and gasoline resistant. This gasket helps to properly seat the oil filter when it is installed on the engine.

Bonding Filter Assembly to End Plates: Single part epoxies are prefered to bond the filter assembly. This is because they offer a simpler process which does not damage the media as welding can and also provides additional assurance of seal because the epoxy is used as a potting compound and a bonding agent.

PROCESS FILTERS
Sealing: Process industry filters made of metal housing and metal mesh media can be welded or sealed with an anaerobic or epoxy depending on the end use requirements.

Again the temperature and resistance requirements dictate the type of adhesive used but generally ultraviolet & visible light curable adhesives exceed the bond strength of epoxies on plastics and exceed the fluid resistance of cyanoacrylates.

Anaerobic Adhesives - An Update

Commonly used as thread lockers, thread sealants, and retaining or gasketing materials, anaerobic adhesives can help manufacturers and maintenance personnel to decrease total manufacturing or operating costs and enhance equipment reliability. These liquid adhesives cure or solidify when restricted from oxygen in the presence of metal ions. As these adhesives contain no volatile solvents that evaporate out of the threads over time, they will not shrink and affect the long-term performance of the sealed joint.

New Technology
New generation anaerobic adhesives have been formulated to withstand temperatures up to 650ºF without degrading. New high temperature/high strength anaerobics thrive in demanding applications and environments including industrial ovens and boiler rooms, as well as heat treating operations in refineries, paper mills, metal fabrication plants, and glass manufacturing facilities. Despite their high heat resistance, these new thread lockers can be removed with standard hand tools after the fastener is heated to 700-750oF for about five minutes.

All anaerobic adhesives facilitate fastener assembly by providing lubrication as the fastener is tightened. This lubrication allows applied torque to be converted into high clamp load instead of dissipating as friction or heat. On bolts that are 7/8-inch in diameter or larger, friction between the threads plays a great role in reducing potential clamp load. Recently developed high lubricity thread lockers more effectively control friction and reliably convert torque energy into clamp load.

Further, new anaerobic products are available with greatly reduced odor, allowing users to work in close proximity to the liquid with less exposure to chemical fumes.

Why do we NEED Anaerobic Adhesives?

Anaerobic adhesives are single part and have two basic requirements to cure.

1) Presence of 2 metal parts.
2) Absence of air – unlike many other adhesives which cure in the presence of air.

There are many types of anaerobic adhesives for a variety of applications; a few major ones are explained below:

Threadlockers are SUPERIOR to conventional lock washers, nylon inserts, and other mechanical devices because they SECURE the entire fastener assembly against loosening from shock and vibration so fastener clamping forces are maintained. Threadlockers also SEAL the threads against leakage and PREVENT rust and corrosion.

Available in a variety of strengths and temperature ratings, Threadlockers remain the most reliable way to lock and seal threaded fasteners of all shapes and sizes, either before or after assembly.

Retaining Compounds are designed to BOND non-threaded, cylindrical metal assemblies by filling the voids between close-fitting metal parts, Retaining Compounds HARDEN to create a solid, one-piece assembly. Retaining Compounds can be used to lock keyways, SECURE splines, augment press fits, and strengthen interference fits. Use them to prevent wear on new components, or RESTORE the fit to worn or out-of-tolerance parts. Retaining Compounds SEAL joints against leakage and PREVENT fretting and corrosion.

Formulated in a variety of viscosities, strength characteristics, gap-filling abilities, and temperature ratings, Retaining Compounds can solve even the most difficult retaining applications.

Thread Sealants seal and SECURE metal pipes and fittings. By filling the space BETWEEN threaded metal parts, Thread Sealants PREVENT leakage caused by vibration loosening, tape shredding, solvent evaporation, damaged threads, and temperature cycling. Designed for low and high-pressure applications, Thread Sealants SEAL instantly for on-line low pressure testing.

When fully cured, they seal to the burst strength of most piping systems. The high lubricating properties of Thread Sealants EASE assembly and prevent galling of the threads. For system repairs, parts may be disassembled with basic hand tools.

Gaskets are used to prevent fluid or gas leaks by forming impervious barriers. For successful gasketing, the seal must remain intact and leak-free over a prolonged period of time. Therefore, the gasket must resist the fluid and/or gaseous medium being sealed or excluded, and withstand the operating temperatures and pressures to which it is subjected.

For more information, please feel free to contact us:

TECHSOLUTE Chemicals (India) Pvt. Ltd.

678, IA, Phase-II, Chandigarh – 160 002

Tel: 0172.2654548, 2652499 Email: info@techsolute.com www.techsolute.com

Techsolute Chemicals India Pvt. Ltd. (formerly Techno-Commercial Linkers) is a more than 15 year old enterprise managed by technocrats with expertise in the field of specialty industrial chemicals.