Material selection
How a material brief is built from the duty condition: temperature, media, sealing force, appearance and compliance, and how each item narrows the compound family.
Silicone materials: where a grade decision comes from
Compound family, filler system, hardness, colour and primer are not independent choices. This column collects the material side of the work: what each decision changes on the part, and where it shows up on the production floor.
Material reference pages
Three pages that cover the selection logic in full.
Properties library
Silicone properties by group — material system, mechanics, environment, function, cleanliness, hardness and substrate matching — so selection starts from the few properties that decide the part.
Material and primer matrix
Which silicone bonds to which substrate, and whether the route is a primer, plasma activation or self-bonding LSR. This is where material choice and process route meet.
Notes from production
4 articles, newest first.
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Optical-grade LSR: AR glasses and headlamp lenses
Where optical silicone is genuinely optical, which product families are ramping, and when glass or resin stays the answer.
Read more -
Platinum poisoning: when samples pass and batches stay tacky
Sulphur, tin, amines and flux residue occupy the catalyst: the poison list, six management rules and how to rule out mould temperature.
Read more -
Self-lubricating LSR vs sprayed silicone oil
Replacing an operator-dependent spray with controlled release: the window, four applications, four cases to avoid and six validation items.
Read more -
Can you drop the primer? Self-bonding LSR
What self-bonding LSR actually bonds to, where a primer still earns its place, and how the bond is verified before tooling.
Read more
Common questions
Material questions that come up first
Which silicone compounds do you mould?
Solid silicone (HCR) and liquid silicone (LSR), including food-contact and medical-grade routes, flame-retardant and self-lubricating systems, and colour or dual-durometer combinations. A grade is picked per project from the drawing, the duty condition and the target market rather than from a catalogue list.
Silicone or TPE for a soft grip?
It depends on how the soft part is fixed, the feel wanted, the cleaning agents it meets and the volume. TPE bonds to polypropylene or ABS by melting into the substrate, which suits a simple snap-on or two-shot part. Silicone needs a primer or a platinum bonding route, but it takes heat, UV and repeated cleaning that TPE does not.
What decides the hardness?
Sealing force, assembly method, hand feel and compression set. Hardness alone does not settle a seal: a 50 Shore A part with the wrong compression ratio leaks just as readily as a 30 Shore A part, so section and squeeze are fixed together with the compound.
Why does curing fail on some inserts?
Platinum-cured silicone is poisoned by sulphur, tin, amines and flux residue on the substrate, which shows up as tacky surfaces or a bond that never develops. The fix is substrate control and incoming inspection, not more catalyst; the failure modes are set out in the platinum poisoning note below.
Where do material and process decisions meet?
At the interface. The same compound can bond reliably to one substrate and not at all to another, which is why material choice, primer selection and surface activation are decided together. The primer matrix page lists the pairings we work with.
Not sure which compound the part needs?
Send the drawing, the media it meets and the temperature range. The compound family and the bonding route are proposed together, before tooling.