Pressure-Sensitive Adhesives (PSA) & Coatings :
Medical Device Applications
 

By : Dr. Ranjit Malik, Group Leader, Adhesives Research Inc., U.S.A.

About Adhesives Research Incorporation The company was founded in the year 1961. The company is having 525 associates worldwide. The company is having manufacturing and R&D facilities in Glen Rock, PA, USA, Limerick, Ireland & in Medellín, Colombia. The sales office is situated in U.S.A and Shanghai. The company is into manufacturing of components, adhesives to assemble the devices and special coatings for these devices.

Manufacturing Facilities :

• Polymer Synthesis (2 1/2 Gallon to 600 Gallon Reactors)
• Adhesive Coating and Laminating ( 21 Coating Lines)
• Silicone Release Coating (Multiple Lines)
• Film Casting
• Slitting and Sheeting

What is Pressure Sensitive Adhesives (PSA)

Liquid adhesives which are liquid in the state they to start out with and then its applied in some way to the parts and some kind of energy in terms of U.V. & thermal is applied to make it convert from liquid state to solid state.

Unlike Liquid Adhesives, Pressure-sensitive adhesive (PSA) is tacky in dry form at room temperature and adheres to substrates with very little pressure to form a bond requiring no activation process such as heat and curing.

Pressure Sensitive Tape: Construction

The pressure sensitive tape can be constructed as follows :

1) Transfer Film : As shown in fig-1 , there is an active layer of adhesive, which is coated on Release Liner. The release Liner is thrown away after the work is over. This form is called Transfer Film because at the end the release liner gets thrown away and it doesn’t become the integral part of device.

Fig. 1: Transfer Film

2) Single - Sided Film

There is a supporting film on one side of adhesive and then there is a release liner. So what you do is pull the release liner back and you have combine support of adhesive and supporting film.

Fig. 2: Single - Sided Film

3) Double - Sided Film

In double-sided there is a adhesive on each side of supporting film and then there is a release liner. Again the release liner gets thrown away.

The Release Liner forms a very important part of total construction because when being used in an automated process the value of release level (the force at which the release liner) gets pull off is very important.

Fig. 3: Double - Sided Film

 

Why Adhesive Tapes? Has functionality - can determine overall product performance Available in flexible format for customization - can tailor properties to suit individual need Converted easily by using laser, rotary and flat bed die-cutting processes Ease of application in automated production

Advantages of PSA Tapes

Formulation Flexibility Chemistry options offer a wide range of properties Property modifications (tack, adhesion, permanent/removable) Variety of substrate, adhesive and liner combinations

Assembly and Process Benefits Instant bonding to most surfaces; easily automated Minimal waste, ease of clean up Non mechanical: fewer parts, no holes, no rust, balanced load

• Considerations of PSA Tapes

For Device manufacturers the considerations are :

• Clean, no solvents (in tape form), skin friendly
• Its is pre applied to the part or die cut prior to assembly so it meets the shape
• Thin precise bond line; controllable thickness

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