Chemistry Reference
In-Depth Information
The process of catalytic hydrolyzes of the alcoxylene groups of the
grafted silane to the silane groups and, then, the catalytic condensation of
the silane groups leads to production of the cross-linked structure through
the siloxane groups. The hydrolyze and the condensation take place in
an increased temperature with presence of the catalyst and water. Dibutyl
tin dilaurate (DBTL) is most often used as a catalyst of the reaction. The
catalyst may be added either to the polymeric blend (it constitutes an in-
creased risk of the premature cross-linking), or in the form of a premixed
reagent during the processing. The mechanism of action of DBTL, as a
cross-linking catalyst, is complex and has not been sufficiently explained.
As a result of cross-linking the polyolefins with silanes the Si-O-Si
bonds are produced, which are more elastic than the rigid bonds C-C cre-
ated as a result of cross-linking of polymers induced by radiation and per-
oxides (Fig. 8.2). Use of silanes gives more elastic products and the cross-
linking process is more cost-effective.
FIGURE 8.2
Structure of polyolefin's cross-linked with a (a) peroxide or radiation (b)
with a silane.
