Fibreglass Resin

[Burdekin]

Hi guys,

I'm going to be modifying a plastic car air box with fibreglass. How well will polyester resin bond and last, considering it will be used in an engine bay or am I better off using epoxy? I have polyester in the shed, hence the question.

Cheers.

 

[Hitch]

Ive not messed with much fibreglass, but plastics I will have a fiddle with now and then...

See if you can find a moulding mark on the bits to determine what type of plastic it is is a good starting point.
Some like ABS, Polyethylene, are quite difficult to stick together with 'standard' epoxy.

 

[gaz1]

whats the application for in usage ?

as ive used that grp stuff for roofs ok but still needed a baseboard to fasten to or use preformed units

 

[Wedg1e]

Worst case scenario if the modified bits won't stick to the 'parent' plastic, just wrap the whole thing in GRP, slit it, pull the original out and bond back together. If appearances are important you could use the bastardised version as a mould to make a complete new one.

 

[Chris Stevens]

I would guess plastic is either HDPE or ABS, neither poly or epoxy will bond to either particularly well. Way to go is a cheap plastic welding kit from Ebay................

 

[Burdekin]

Thanks. Will ask the fibreglass supplier what they reckon as well.

 

[Chris Stevens]

Thanks. Will ask the fibreglass supplier what they reckon as well.

If they reckon either poly or epoxy will bond to plastic they are not telling the truth. Only thing which might work is some sort of bumper repair adhesive (avoid the very cheap ones though, as not likely to work).

 

[Shox Dr]

As said Bumper repair adhesive, may well do the job.

I'd tell you want It was, but I binned the empty tube a few weeks ago.

 

[pedrobedro]

Tiger seal will stick it together. I've used fibreglass and polyester resin to modify a bike airbox and it stuck that together alright. You could use thin metal plate and rivets and glass over it for looks. A bit of satin black paint does wonders.

 

[Burdekin]

It seems most likely that it would be polypropylene from my googling. And further googling it appears 3M Specialized Hot Melt Glue is the best choice but also super glue is another good choice.

The fibreglass man got back to me (I didn’t say what type of plastic) and said:

Fibreglassing plastic and getting a good bond is not easy. Hards plastics such as PVC, ABS, PE and PP have a surface that resins cannot grip well so you are relying on mechanical key only. There are specialist epoxies that can get a better bond through to being both extremely hard and flexible to avoid shock releasing but these are quite expensive compared to polyesters.

If using polyester resin then I can only advise extreme abrasion of the plastic surface then drill 1mm holes in the plastic for the resin to soak into to achieve sort of resin 'rivets'. If the unit is not under too much stress the bond should hold fine enough.

There are some primers for certain plastics such as PVC primer "Microseal T20" but for such a small project it may be not cost effective and you'll need to know, for sure, what plastic you are dealing with.”

 

[Burdekin]

This superglue is supposed to be the dogs for PP plastic: 3M Scotch-Weld SF-100. So ordered some from ebay and will give it a try.

Thanks.

 

[Chris Stevens]

Loctite 480 is very effective for plastic, and will also stick rubber even. Not as good as 2 pack systems for bumper repair though, which remain flexible and will work better than any rigid set superglue type products.

 

[Burdekin]

Loctite 480 is very effective for plastic, and will also stick rubber even. Not as good as 2 pack systems for bumper repair though, which remain flexible and will work better than any rigid set superglue type products.

Thanks.

Didn't go with the bumper glue as the couple I looked at said they don't stick polypropylene.

 

[Chris Stevens]

Superglue is good for bonding something like a tube within a tube, but doesnt work that well on most joints as its very rigid, and the plastic flexes. Leads to early failure. If you know for sure what plastic you have and no bumper glue available, if it were me I would either plastic weld, or make add on part out of aluminium and pop rivet in place.

 

[ajlelectronics]

West Systems make a plastic bumper repair kit which professional bodyshops use. It is an Epoxy resin fibreglass kit.

 

[Chris Stevens]

Have a look at this for helpful info on plastics:http://www.weldguru.com/plasticrepair.html

 

[Burdekin]

Not got a fixed plan of attack as yet as I haven't got the air box yet. I have a few ideas now and a bit more knowledge so that's a good starting point.

 

[Chris Stevens]

Most OE air boxes are pretty restrictive, and one which flows more air will improve performance (but generally more noise).

 

[Burdekin]

It's a Mercedes C 270 cdi (6120900301) air box. Hopefully should do the trick but it's just a suck it and see at this stage.