SOLID AND LIQUID SILICONE RUBBER ... - Wacker Chemie

1.4
CURING
PLATINUM-CATALYZED
ADDITION CURING
Addition Curing
Addition of H-siloxanes
to C=C double bonds
During platinum-catalyzed addition
curing, the crosslinker's Si-H groups
react with the vinyl groups of the
polymer to form a three-dimensional
network. WACKER offers silicone
rubber grades which already contain
the platinum catalyst as well as grades
to which the catalyst must be added
prior to use.
120 – 200°C
Pt-catalyzed
hydrosilylation
Uncured state Elastic state
Advantages
Unlike peroxide-curing, platinumcatalyzed
addition reactions do not
produce odor- or flavor-impairing byproducts.
This is a major advantage
for food-contact applications. A further
benefit is that colors are not affected
by thermal post-curing. Curing is fast,
and the curing speed can be controlled
via the temperature. The cured
rubber demolds very easily and has
a dry surface, thus facilitating further
processing and reducing production
cycle times.
Processing Information
Even small amounts of catalyst
poisons in the ambient air can inhibit
the catalyst, especially amine- and
sulfur-containing compounds of the
kind encountered during processing of
organic rubber grades. For this reason,
platinum-catalyzed systems must be
stored and processed in a separate
room, well away from organic rubber.
Roll mills and processing machinery
must always be scrupulously
cleaned in order to prevent crosscontamination.
You will find additional processing
information in section 5, page 39.
13
Basic Principles