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Medical Device Adhesives: Adhesives Selection
There are two characteristics that has to be kept in
mind during the selection of adhesive and they are :
1) Processing :
a) Uncured Properties
b) Curing Properties
2) Performance : Cured Properties
1) Processing
In processing consideration, a
manufacturer has to keep in mind that how many parts
am I going to manufacture what is cycle time and hence
what is the fixture time that is required.
Whether is it possible to automate
the process and increase the production efficiency?.
By doing this one can easily think
of reducing the labour, floor space and capital
equipment costs required.
Among the selection of adhesives
the uncured properties plays the major role . The
property includes Viscosity, Extrusion Rate, Thixo
Ratio & Sag. Viscosity ensures that there is even gap
filling to give sufficient sealing of the device.
Thixo ratio property ensures that adhesive does not
flow into different areas and bond unnecessary part.
The curing properties gives idea
about the fixture time that is required? Like Tack
Free Time, Working Life, Gel Time & Pot Life.
Fixture Time :
Measure of how quickly an adhesive
develops enough strength to bear a load. To compare
values, we need to know: Substrates , Bond area , Bond
gap, Fixture weight, Time weight was supported |
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Tack Free time : Typically
for moisture cure adhesives. Measurement of how long
it takes for the adhesive to develop a tack free
surface. Difficult to measure quantitatively.
Important that temperature, relative humidity and any
other environmental inputs that may affect cure are
constant
Work Life :
Once a two-part adhesive is mixed
with a catalyst, its viscosity will begin to rise. The
amount of time that the adhesive is still low enough
in viscosity to be used is known as the work life.
Some manufacturers measure the time for viscosity to
double.
Gel Time / Pot Life :
The amount of time it takes for an
adhesive to cure sufficiently to form a lightly
crosslinked, gelatinous mass. Generally applies to two
part adhesive systems. With exothermic systems, size
of vessel holding the adhesive will have a large
effect on pot life.
2) Performance
The performance characteristics
includes how well the adhesive stick today? and how
well the adhesive will stick after exposure to various
conditions like heat, humidity cold, chemical
exposure, thermal cycling, cyclic loading, shock,
impact & flexing.
The Adhesives
Henkel Adhesives Technologies India
Pvt. Ltd have more than 50 medical device
adhesives/sealants representing six technologies like
light cure acrylics, light cure silicones*,
cyanoacrylates, light cure cyanoacrylates*, epoxies &
polyurethanes. The medical device adhesives offered by
Henkel Adhesives Technologies India Pvt. Ltd covers a
variety of chemistries, providing the manufacturer
with a wide range of choices and assembly solutions
because one product won’t fit every design, and that’s
why there is a need to create and add new products
continuously, new chemistries, and even new
technologies. |
