Name: Methylhydrosiloxane Crosslinker for Addition Cure HCA-100
Brand: Coatingsink
SKU: hydride-crosslinker-addition-cure
Availability: InStock

Question 1

How do I calculate the stoichiometric loading of HCA-100 relative to a vinyl PDMS base?

Accepted Answer

Determine milliequivalents of Si-H in HCA-100 and vinyl groups in the base polymer per 100 g of total system. Target a Si-H:vinyl molar ratio of 1.2–1.5:1 for optimal cure completeness. Higher ratios accelerate cure but excess Si-H reacting with trace moisture can generate hydrogen gas and micro-voids in the elastomer.

Question 2

What symptoms indicate an under-crosslinked network from insufficient HCA-100?

Accepted Answer

A Si-H:vinyl ratio below 1.0:1 leaves unreacted vinyl groups, producing a tacky surface, low tensile strength, and poor compression set. Verify the Si-H content of each production lot by iodometric titration before formulating and adjust crosslinker addition accordingly.

Question 3

Is HCA-100 compatible with condensation-cure (tin-catalyzed) silicone systems?

Accepted Answer

No. Poly(methylhydrosiloxane) functions exclusively as a crosslinker in Pt-catalyzed addition-cure chemistry. In condensation-cure systems it does not participate in the network-forming reaction and may generate hydrogen gas through hydrolysis, creating foam defects and reduced mechanical performance in the cured sealant.

Si-H Content	7.0–8.0 mmol/g
Active Hydrogen	0.15–0.17 wt%
Density (25°C)	1.00–1.01 g/mL
Viscosity (25°C)	20–30 mPa·s
Recommended Loading	5–15 phr on vinyl polymer

Methylhydrosiloxane Crosslinker for Addition Cure HCA-100

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