Revision 1. 6
1.16
General
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Processing Epoxy Resins
Process cold-curing epoxy resin systems at room temperature (20-25°C [68-77°F]).
By choosing the right temperature you can decisively influence both the processing properties of the
resin as well as the properties of the cured molded materials. In general, changes in processing
temperature have the following effects:
Increasing the temperature:
ð
reduces the viscosity (the resin flows more freely),
ð
improves the wetting of the fibers, and
ð
shortens the processing time.
Conversely, decreasing the temperature leads to higher viscosity and poorer wetting of the fibers. On
the other hand, lower temperatures can increase the processing time. Please note, however, that at
temperatures below 15°C (59°F) the curing process slows down considerably, so that thin-walled
laminates may still not be cured after several days, if the temperatures are too low.
Advantages of a Slightly Higher Processing Temperature
A very low viscosity is particularly favorable for manual lamination, because low-viscosity resins can
impregnate fibers and fabrics much better. However, reducing the viscosity by adding thinners or
solvents is only possible to a limited extent and can cause the molecular chains to break. On the
other hand, by raising the temperature by only 5°C (9°F) you can reduce the viscosity by almost 50%
without affecting cross-linking properties.
For optimum working, slightly warm the resin and the forms.
Resins should have a minimum temperature of 25°C (77°F) for processing. To achieve this, you can
heat the container, e.g. in a water bath, before use. By raising the temperature to a maximum of 35°C
(95°F) you can lower the viscosity even further.
However, keep in mind that a temperature increase of 10°C (18°F) reduces the processing time by
50%. Mix small quantities of heated resin and process them quickly.
Curing Epoxy Resins
When epoxy resins cure, they undergo a chemical process, in which the molecules of the individual
components react with one another to form long, cross-linked molecular chains. Epoxy resins cure
by the process of polyaddition, i.e., for each element in the resin there must be a certain number of
elements from the hardener component. If the mixing ratio is not precisely observed, unlinked
elements will be left behind in one of the components. This incomplete cross-linking can result in
reduced strength of the molded materials.
