While I was trying to find another use for zinc. I found out that Zinc (oxide) is commonly used in the manufacturing of rubber. So I decided to make a manufacture rubber reaction.

Well, it turns out rubber is quite complicated to create. You need a resin + coal tar + sulfur + zinc + fuel.

Coal Tar is a result from burning coal. Other uses for Coal Tar include :
Paints / synthetic dye
+ alcohol = soap (used in anti-dandruff and kills head lice probably won't require alcohol as there's a bug where it will use the entire stack of alcohol)
Asphalt Blocks
Fuel

It also requires a 'plasticizer' but I wasn't able to find a definitive answer of what a plasticizer is without having to go ask my chemistry teacher. So I skipped that step.

I was thinking 20 tires was enough to make the procedure worth it. That will equip an entire squad with tire armor.

While we're on the subject, perhaps other items could be made of rubber. Gloves and boots being my primary concern. I think there's a bug with gloves, I'll have to do a quick search on the forums.

Of course the entire process seems very tedious, 'would anyone actually use this?' remains at the forefront of my mind. After all, it's so much easier to just build a forge and get metal armor yourself. I suppose I could make tires just tough leather x2, but still, the effort required is questionable. However, since rubber would be x2 leather, and Coal Tar would be a natural by product of coal smelting. I can see players saying "Well I have all the items, might as well." rather than going out of their way to actually create the thing.

Second issue is materials, you need Coal, Gypsum, and Zinc on the same embark site, and have access to them. This seems like a very specific embark site. Something that I try to avoid is embark specific items as it blocks off a game feature. Furthermore, considering that gypsum, and zinc are both located farther below than most ores doesn't help. By the time you reach them, no doubt you will already have plenty of tire armor just by gathering from the surface.

Coal Tar seems extremely useful though, and I am seriously considering adding it.