Recent content by Metten

Contact discoloration is a possible issue for rubber. The plasticizer in EPDM can cause it. Unless you can alter the formulation by using less and/or other types of oil, I have no solution for you.

Compounds for compression aren't necessarily good for injection too. Viscosity should be low enough to ensure short injection times without scorching the rubber. Ts2 value should be high enough to have a safe window to inject the rubber and completely fill the mould. I would propose to check...

You could measure the density to rule out a few options. I still think the supplier should be able to answer your question. They should know what they sell, certainly for a medical device. I regularly get questions about the temperature range our products can be used at, which cleaning solvents...

Ask the supplier? You could ask for a safety data sheet.

We use small amounts of platinum cured silicones, but do not see the same phenomenon. Store it cool and away from contamination (sulphur and other vapours).

We use an NR/SBR blend. NBR wouldn't be my first choice, but odour isn't the reason for that.

The colour of the rubber has little influence on the chemical resistance. I would advice against (black) (poly)urethane rubber if you use aceton (+ other solvents).

Post cure in oven with air circulation to reduce the amount of volatiles.

EPDM peroxide: often distinct smell (not burnt!), soft dry ashes EPDM sulphur: smoke has a certain smell, soft dry ashes SBR: no special mention of the smell after burning, hard dry ashes NBR: hard and dry ashes, asphyxiating smell CR: hard and dry ashes, HCl smell (when burning with flame...

Just cut a very small strip: few centimeters long, few millimeters thick. Burn that for 1-2 seconds and extinguish. You should have enough ashes to drop on a paper without the paper catching fire. By the time someone alerts your safety personel, you can get rid of the paper and open a window...

Burn a small sample. If the try to smear the ashes and they are very smooth, it probably is EPDM. If the ashes are dry and hard you might have SBR (or other types of rubber). Properly formulated EPDM with peroxide cure should be able to withstand 130°C. If there is contact with glass, you...

Give the rubber molder a specification to which the rubber needs to comply and request a small vulcanised sample of the type they offer (test slab, not your required shape). example spec: NR or Latex based (the exact name really doesn't matter, if it works, it works) 30-40ShA density <1 or >1...

Have you tried two stage mixing? First stage up to 150°C fe and second stage with accelerators up to 100°C one day later?

1. A higher temperature will melt more ingredients, making the dispersion much easier. Too high temperatures will break down your elastomers or cause side reactions. The type of rubber (and formulation) will determine your dump temperatures. CR rubbers have low dump temperatures, very soft EPDM...

FKM normally has a higher density: 1.7 to 2.2 kg/L; NBR (Buna N) varies between 1 and 1.4 kg/L. So the weight per sheet should tell you the type.