Factice
Factice is vulcanized unsaturated vegetable or animal oil, used as a processing aid and property modifier in rubber.
Longer chain fatty-acid containing oils such as rapeseed or meadowfoam produce a harder, more desirable factice. Soybean oil produces lower quality factice, though it can be mixed with longer-chain oils to yield factice nearly as good as that made from long chain oils alone.{{cite journal|last=Erhan|first=Selim M.|author2=Kleiman, Robert|title=Factice from oil mixtures|journal=Journal of the American Oil Chemists' Society|date=March 1973|volume=70|issue=3|pages=309–311|doi=10.1007/bf02545313|s2cid=95493744|url=http://naldc.nal.usda.gov/download/24579/PDF|accessdate=March 16, 2012|archive-date=April 12, 2013|archive-url=https://web.archive.org/web/20130412220011/http://naldc.nal.usda.gov/download/24579/PDF|url-status=dead}} Oil-resistant factice is made with castor oil.{{cite book|editor-last=Simpson|editor-first=Richard B. |title=Rubber Basics|url=https://archive.org/details/rubberbasics00simp|url-access=limited|year=2002|publisher=Rapra Technology Ltd.|isbn=1-85957-307-X|pages=[https://archive.org/details/rubberbasics00simp/page/n140 133]}}
Cross-linking the fatty-acid chains with sulfur (brown factice) or S2Cl2 (white factice) yields a rubbery material that improves the processing characteristics and ozone resistance of rubber. Varying the amount of factice changes the physical properties of the rubber; molded items might be 5–10% factice, extrusions 15–30%. Rubber erasers can have as much as 4 times as much factice as rubber in their composition.