The MCT 300 can measure hot melt adhesives
on paper, board and textiles. Hot melt adhesives are typically
solvent free thermoplastics, they melt or decrease in viscosity
at temperatures in excess of 180o F, then rapidly set upon
cooling. They can be repeatedly softened by heating, and hardened
by cooling, this property makes them very useful in discontinuous
manufacturing processes where one of the 2 substrates may
be applied in a separate location. Different polymer systems
are used to form hot melts depending upon the application:
Acrylates (hot melt PSA)
are used in packaging and construction
Styrenes (SIS and SBS) are
used in pressure sensitive applications
Polyamides are used in high
strength hot melt adhesive systems
Polyethylene (PE), Polypropylene,
and other olefins are used for a variety of applications
Polyurethane (PU) adhesives
are used in applications where excellent flexibility and durability
are required.
Measurement of coat weight is
important for 2 main reasons: lf wound:
1. Adhesive coating needs to be uniform to provide a high
coefficient of adhesion between the two substrates.
2. For cost effectiveness, the aim is to apply the minimum
quantity of coat weight in order to achieve adhesion.
Manufacturing Process
Polymer granules are apportioned into an extruder whereupon
they are melted, and applied with a doctor blade into the
engravings of an engraved roller through a slit die, before
being applied to the substrate. Alternatively the molten adhesive
is extruded through a slit die onto the substrate at the nip
between a pressure roll and a metal chill roller.
Measurement Locations
Measurement is made immediately after the chill roller, on
the set adhesive. The gauge should be mounted approximately
8 inches from the surface of the web. |
