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.

New Products at TECHSOLUTE

Techsolute has tied up with some global leaders to market their products:

• COX, UK: PC Cox is the world's largest, most progressive and successful manufacturer of hand-held sealant applicators, with a range of over 90 models, manual, battery and pneumatic, for single and dual-component materials, and capable of dispensing cartridges, sachets or bulk material. visit http://www.pccox.co.uk

• GE-Momentive: Momentive Performance Materials Inc, formerly referred to in the construction industry as GE Silicones (or GE Toshiba Silicones in Asia and GE Bayer Silicones in Europe), has been a world leader in silicone sealants and adhesives for more then 40 years. Supplying a broad range of GE brand sealants and adhesives globally for diverse markets and applications.
  

Choosing the right lubricant - Prevent micropitting

All gears are susceptible to micropitting, a condition that can damage gear tooth
accuracy and even cause catastrophic equipment failure if left unchecked.

Micropitting damages gear surfaces beginning at the contact points and spreads
through gear surface cracks. The main crack undermines the surface by growing
deeper and spreading in a fan shape, including external, internal, spur helical and
level gears. Although micropitting is not easy to detect, the selection of the correct lubricant can greatly help mitigate its costly effects.

Here are measures to guard against micropitting:

• Increase oil film thickness – Use the highest practical oil viscosity, run gears at high speeds, cool gear teeth, and use synthetic oils above -80° C.

• Reduce surface roughness – Coat teeth and run-in with special lubricant,
pre-filter lubricant, keep oil cool during run-in, drain lubricant and flush
gearbox after run-in, and change filter frequently.

• Optimize lubricant – Select oil with high micropitting resistance, low traction coefficient, and high pressure viscosity coefficient. Avoid oils with aggressive EP additives, and keep oils cool, dry and clean of solid contaminants

By carefully selecting the correct lubricant, industrial maintenance professionals can reduce incidences of micropitting, increasing efficiency and reducing costs by helping safeguard against equipment failure.

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.