Elastomers, treated as an engineering material
Elastomers are specified more loosely than any other structural material in a typical assembly. A metal part gets a grade, a heat treatment and a tolerance; the seal next to it gets a colour and a hardness number. These essays take the other approach — what distinguishes the polymer families, why compression set rather than rupture ends most seals, how hardness trades against sealing force and wear, and why ageing, not load, sets the service life of the majority of rubber parts.
All essays
- Ageing sets the service life, not load
Ozone, ultraviolet light, heat and chemical attack change the polymer network itself. For most rubber parts the end of life is a chemistry problem, and accelerated testing can be both faster and wrong.
- The triangle: hardness, sealing force and wear
Hardness is a purchasing control that gets used as a design variable. What actually trades against sealing force and wear is modulus, conformity and hysteresis — and they cannot all be improved together.
- Compression set, and why seals fail slowly
A seal holds because stored elastic energy presses it against two surfaces. That force decays continuously, so leakage begins as a threshold crossing rather than an event.
- Why the operating environment picks the polymer
Natural and synthetic elastomer families differ by backbone chemistry, and that chemistry — not strength — decides which fluids, temperatures and weather a part survives.