Color change when using Sulfur cure vs peroxide cure
Color change when using Sulfur cure vs peroxide cure
(OP)
We produce a light colored EPDM / SBR copolymer that is usually cured with peroxide. If we attempt to use a sulfur cure system, there is a serious shift in the materials color, becoming much yellower...and even has signs of scorched places (a golden brown). Is it possible to overcome this? Or should we just stick with the peroxide cure system?





RE: Color change when using Sulfur cure vs peroxide cure
RE: Color change when using Sulfur cure vs peroxide cure
RE: Color change when using Sulfur cure vs peroxide cure
If you are using Crystex OT20 or other insoluble sulphur keep your final mix temperature below 105°C and cool the batch as quickly as possible after dumping otherwise you will convert the sulphur to the soluble form and that will produce a creamy-white colouration and/or bloom on the surface of the rubber.
Other ingredients that will cause discolouration are PPD-type antioxidants - use BHT or similar hindered phenol - and TMQ, although with EPDM in the compound you do not need these protective agents.
RE: Color change when using Sulfur cure vs peroxide cure
Tom Jablonowski, TSE Industries, Inc.
www.tse-industries.com
RE: Color change when using Sulfur cure vs peroxide cure
RE: Color change when using Sulfur cure vs peroxide cure
If you're using a neat peroxide, you might consider one that's absorbed on a filler, such as DiCup 40C or Varox DBPH-50.
Tom Jablonowski, TSE Industries, Inc.
www.tse-industries.com
RE: Color change when using Sulfur cure vs peroxide cure
RE: Color change when using Sulfur cure vs peroxide cure
Some types of rubber, and different rubber compounds (probably those that are more resistant to abrasion), can build up more heat than others during grinding. I hadn't heard that this phenomenon is related to a type of cure system, seemingly mostly related to grinding technique/speed.
Hope this helps.
Tom Jablonowski, TSE Industries, Inc.
www.tse-industries.com
RE: Color change when using Sulfur cure vs peroxide cure