Rovema CMK Operator’s Manual
Section 3: Functional Descriptions
200246 CMK Operators Manual (02/06/2006) 3-12
Gluing Considerations
Properties
Hot melts are thermoplastic adhesives that are processed in their molten state.
When hardening, the glued joints may be dry after a few seconds. Depending on
the type of glue, hot melts are usually waterproof and may be freeze-proof or heat-
proof. Movement of the glued joint prior to hot melt hardening may create an
improper seal.
Processing Temperature
Ensure that the hot melt processing temperature in the nozzle is in conformity with
the temperature given in the supplier’s manufacturing data.
Open Time
"Open time" refers to the period where the conglutination must take place. It is
influenced by the glue temperature, the applied glue quantity, the room
temperature (ambient temperature), as well as the properties of the material to
be glued. If the period between the glue application and the pressure is longer
than the indicated open time, then the hot melt will be entirely or partially
hardened so that no reliable conglutination would be achieved.
Relationship Between Temperature and Viscosity
Varying the processing temperature can influence viscosity and flow properties:
• An increase of the processing temperature, lowers the viscosity, but
shortens also the open time.
• A decrease of the temperature provokes an increase in the viscosity, and
shortens the open time.
If the processing temperature remains considerably under the recommended
temperature, the flowing properties and the use will be bad so that the glued joint
would not reach 100% firmness.
A temperature decrease of 10 - 20 % may provoke a viscosity increase of 20 -
50%!
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