Seals that cure predictably, cabins that stay breathable

Automotive compounds ask three things at once: heat ageing resistance, tight control of the cure, and low smoke toxicity in an enclosed space. Magnesium chemistry is the industry default in all three — under the bonnet, in the door seal, and inside the wiring harness.

01Seals, hoses and vibration parts

Neoprene (CR) is still the material of choice for door seals, coolant hoses and anti-vibration mounts, because it balances oil resistance, weathering and flexibility. Every one of those compounds relies on MgO as the acid acceptor: it neutralises the HCl released during vulcanization, prevents the cure from running away, and protects the polymer during heat ageing.

The standard package is 4 phr MgO with 5 phr ZnO. Get the MgO activity wrong, and the symptom shows up as scorch in the mixer, mould fouling, or a cure time that drifts between batches.

02Under-hood high-temperature plastics

Parts near the engine see continuous temperatures that rule out aluminium hydroxide — it would start decomposing during processing. Mg(OH)₂, with its 300–320 °C decomposition window, survives compounding in PA and PBT and still delivers halogen-free flame retardancy when the part is exposed to fire.

• Low smoke, zero halogen — no acid gas to corrode connectors or electronics.

• Smoke suppressant synergy — cuts peak smoke density for enclosed-cabin requirements.

• Process stability — surface-treated grades keep melt flow and mechanicals workable at high loading.

03Wiring harness and interior trim

A modern car carries kilometres of cable. Halogen-free Mg(OH)₂ compounds are increasingly specified for harness insulation and sheathing, and for interior trim parts where smoke toxicity in a fire is a design criterion rather than a nice-to-have.

04Recommended grades