polyurthene vs fiberglass

[pyroracing85]

I was reading in a summit catolog and came across polyurthene body kits for cars. I thought they were made out of fiberglass. But it simply put that the fiberglass doesn't have the UV protection like the polyurthene. Is this through?

[ger21]

Most fiberglass and epoxies break down from UV exposure. But once you paint them, it shouldn't be a problem.

[pyroracing85]

ahh soo the painting actually protects as a uv protection?

I am not sure what polyurthene looks like. Do you know of any examples?

[Heavy D]

polyurthene can come in many forms like bushings that would replace rubber ones. it's more durable. For body kits, fiberglass is very strong and rigid. It is not flexible like the stock bumpers on cars these days so if you hit something, it will crack. polyurthene is flexible and will just go back to shape when it takes a small hit... this is much more favorable for body kits and a quality body kit is made with urethane rather then glass

[pyroracing85]

Originally Posted by Heavy D polyurthene can come in many forms like bushings that would replace rubber ones. it's more durable. For body kits, fiberglass is very strong and rigid. It is not flexible like the stock bumpers on cars these days so if you hit something, it will crack. polyurthene is flexible and will just go back to shape when it takes a small hit... this is much more favorable for body kits and a quality body kit is made with urethane rather then glass

I got ya. yea bushings. So polyurthene is a type of plastic? Which would be injection molding?

[ViperTX]

Fiberglass is generally laid or shot. Polyurethance is cast in a mold using different techniques.

[turmite]

I am by no means an expert but I think that large parts made from poly are vacuum formed where you take a sheet of the material place it in a fixture that is held in place above a mold. The material is heated till it begins to soften and then the fixture lowers to the mold lip and vacuum is applied to the mold shaping the part. I watched this process for hot tubs, shower stalls etc. and it was really neat to see. I will say that the material they used was sheet acrylic but I think the poly is done the same way.

Mike

[skippy]

As ViperTX said, polyurethane is generally cast by mixing the two components, heating it and then pouring it into a mould to make things like car suspension bushes. There may be other ways to use it such as (a) spraying it into an open mould or (b) rotary or rotating moulding, to obtain a thin wall product such as a model car body but I haven't seen these used. I doubt that PU can be vacuum formed as it's generally impervious to heat. It's more likely that it was polycarbonate that was used as it's very tough and doesn't crack. To vac form something it must start off in sheet form. Suitable plastics for vac forming include polycarbonate, acrylic (plexy or perpex, etc.), ABS, polypropylene, polystyrene and the list goes on. Shower trays, etc. are made using sanitary grade acrylics which are generally very shiny, have good resistance to chipping or cracks, and above all, inhibit the growth of mold (as in funghi) and bacteria growth due to their minimal surface porousity. i.e. there aren't surface pores for germs/bacteria to develop in.
Skippy