Silan Si-69 und Silica-Verbindungen: Die richtige Kopplung

Silica without a coupling agent behaves largely as a non-reinforcing filler. The silane is what bonds the silica surface to the polymer, and that reaction has specific requirements in the mixer.

What the reaction needs

• •Temperature window — silanisation generally needs the compound to reach roughly 140–155 °C during mixing, and to stay in that window long enough for the reaction to complete. Too cool and the ethanol by-product is not driven off; too hot and the silane degrades.
• •Mixing time — silica compounds usually need multiple stages with a holding step. A single-stage mix to the usual dump temperature commonly leaves the reaction unfinished.
• •Moisture control — high surface moisture on the silica consumes silane without producing coupling.

Symptoms of incomplete silanisation

Poor abrasion resistance, high compound viscosity that does not drop with further mixing, high hysteresis and heat build-up, and a Payne effect much larger than expected. These are frequently misdiagnosed as a filler dispersion problem, which leads mills to add mixing energy instead of fixing the temperature profile.

Buyer checklist

Confirm the silica surface area, the silane grade and loading, and the number of mixing stages your supplier intends to use. Ask for the rheometer curve and the dynamic properties, not just tensile data — the dynamic figures are what reveal silanisation quality. ## Need the documents or today's price? Send us the grade, quantity and destination port — we return a quotation with COA and MSDS attached. Email manager@fipolymer.com or use the inquiry form on this site.