Material temperature directly affects viscosity and ratio, and moisture affects isocyanate quality. The most common cause of faulty parts when the seasons change.
If the same machine, recipe and mould made good parts yesterday but bad parts today, one of the first things to check is material temperature and moisture. Especially when the seasons change, these two factors cause a large share of the problems.
What does temperature change?
- Viscosity: Cold material thickens; pump flow and injector pressure change and the ratio drifts.
- Reaction speed: Higher temperatures speed up the reaction; cream and gel times shorten and the foam can set before the mould is full.
- Density: The same shot weight gives a different volume and hardness.
The correct working temperature is stated in your material supplier’s technical data sheet. Tanks with controlled heating and cooling and continuous temperature monitoring are the most reliable way to stay within that range.
Why is moisture dangerous?
Isocyanate reacts with moisture in the air. The result is crusting and crystal formation in the tank, clogged filters and injector wear; the product may show unexpected foaming and bubbles.
- Use desiccant cartridges on tank vents and check their colour regularly.
- Do not leave drums open; transfer material through a closed system.
- Keep the material in a closed circuit before long stoppages.
Measures on the machine
Flowmeter-based metering control shows temperature-related ratio drift instantly. On Polymix machines material levels are shown on screen in kilograms and the ratio in grams per second, so the operator can intervene without stopping production.
Frequently asked questions
Why do my parts get harder or underfill in winter? Cold material raises viscosity and changes the ratio and reaction speed. Check the tank temperature and verify the ratio with the flowmeter.
What should I do if crystals form in the isocyanate tank? Check the desiccant cartridges and tank sealing, and clean the filters. If the problem continues, get service support.
