Which Rubber Material is Best Suited? 1

[sethro5hc]

Hey guys, I work almost exclusively with steel and a little with plastics, but now a product of mine needs a rubber part. The part will be used outdoors so it needs to be UV resistant and weather resistant. It also will need to be colored so it needs good color fastness. It needs to be fairly rigid and hold its shape, yet malleable under relatively small loads. It's function will be to hold bicylces (the frame is steel, this is just what the bikes sit on and get strapped too), so that could give you an idea of the ideal properties. Currently, we're using thermoplastic rubber, but the kind we have is nowhere near rigid enough and is succeptible to ripping and tearing. Any suggestions for other rubber types that may be suitable, and hopefully a little more rigid? It can be as rigid as necesarry as long as it wouldn't scratch the paint off of a bike frame.

Any suggestions would be appreciated, I'm new to working with rubber.

 

[btrueblood]

EPDM. About 70 or 80 durometer. Black is common, colors are possible.

 

[GrahamBennett]

I agree with btrueblood EPDM will be fine for your job in hand. Before you obtain moulding though I would suggest you visit a local vehicle breakers yard or repair shop and get a couple of scrap coolant hoses and try those - these hoses are usually made from textile reinforced EPDM compounds.

 

[btrueblood]

Graham's got it right, but make sure you don't get the silicone hoses sold as aftermarket coolant hose - they are usually in bright colors. EPDM coolant hoses are almost uniformly black. If you really want to be sure, you can also buy hose and/or sheet EPDM material from various suppliers, e.g. McMaster-Carr

 

[sethro5hc]

Thanks for the suggestion. What about SBS, I've seen it used in applications where I'd think the same properties are desirable.

 

[btrueblood]

Do you mean SBR (styrene-butadiene rubber)? You would have to make sure the right additives are in the stock you buy, in order to get reasonable UV and weathering resistance. You might also find it tends to leave marks on some painted surfaces.

 

[sethro5hc]

SBS as in poly(styrene-butadiene-styrene). I was a little worried about it leaving marks though, since this same rubber is used in tires and in the soles of shoes. But that is the same type of hardness I'm looking for. Something that doesn't noticeably deform when you press it with your hands, but gives enough to not dent or damage a metal bike frame.

 

[btrueblood]

Dunno much about SBS, but would expect poor UV resistance there as well, unless proper additives are put in it.

 

[Compositepro]

How about PVC plastisol? It seems to be commonly used for this type of application using a simple dip coating process. It is also inexpensive.

 

[GrahamBennett]

Sethro5hc - SBS is an engineering plastic as far as I'm aware. It is styrene-butadiene RUBBER (SBR) that is used in passenger tyre treads.

 

[tom1953]

SBS is a thermoplastic rubber most commonly known as Kraton (

http://www.kraton.com).

There are different types, the most common (I believe) is the SBS (Kraton D). They also make the more UV-resistant, similar material SEBS (Kraton G). As Graham noted, it's SBR (blended with NR and BR usually) that's used in tire treads.

Carbon black reinforced EPDM would be my first choice for this application based upon the requirements noted.

tom

 

[GrahamBennett]

Thanks Tom for the infor re SBS.