Need advice for vulcanizing shore A-70 rubber. 1

[janeriksen]

I need to know how much I shall use of each part of natural rubber and sulphur in order to make vulcanized rubber with a hardness of A-70. Also interested in which temperature and heating time.

Are there any good online stores where I can buy natural rubber and sulphur in small amounts for testing it out?

 

[stancom]

A typical sulfur level will be between 2 and 3 parts per hundred parts of raw rubber, aided by an accelerator, but that will only give you a vulcanisate hardness of ca 35 t0 40 Shore A. You'll appreciate the need for a loading of filler and the choice will depend on the properties you need. A higher than normal sulfur level will certainly raise hardness but at 70 A the properties will be awful, ie in the dip between vulcanised rubber and ebonite.
For samples I suggest you contact a friendly rubber company nearby, as you were advised to do in answers to your earlier 2011 enquiry.

 

[tom1953]

LMGTFY
One reference on the Internet that has some typical formulas and compounding info is:

http://www.rubber-foundation.org/docu/Natuurrubber_38.pdf

Good Luck!