Fixing Plastic Cracks

[Tristin]

Ive got some plastic trim that has cracked... Im tired of dealing with it and would like to fix it. What are people experiences with fixing something like this? I know there is some epoxy I can use to fill in the cracks and then sand it flat. Ive also seen some plastic welders. 

 

 

Real world experience?

 

 

 

 

[TENDRIL]

pics by chance? 

[Tristin]

pics by chance? 

 

Original post updated. 

[flatcat19]

Plastic welder is fun as shit to use.

 

Takes a little practice though.

Much like regular welding does.

 

 

Harbor Freight's plastic welder is actually pretty decent.

Buy that, practice with an unused piece.

 

If it is a clean, fresh-ish break, you can barely tell if done well.

I have fixed lots of other peoples "mistakes".

 

I don't like epoxy. It gets harder than the plastic.

It also gets brittle and falls from the plastic with pressure.

Too much work and wishing to rely on an epoxied repair.

[thisismatt]

Epoxy doesn't really bond plastic that great in my experience.  I haven't had a plastic where I couldn't pop the epoxy off after cure, unless for some reason the plastic was fairly porous and the epoxy was able to hold to a bit of tooth.  If the plastic is PVC or ABS you could try the appropriate cement which should do the trick.

[athoose]

A buddy taught me a trick with cracked plastic radiators.  Heat it with a mini torch trying to overlap/blend the crack.  Then score/gouge the surface giving it a rough texture for the JB weld to adhere to.  He then slathered a 1/8 or thicker layer of JB weld an inch or more beyond the crack in any direction.  I sold the car 5 years later and it was still holding. 

 

I've been meaning to try this with trim or at least applying some of the principles.  Certainly it may not work in regards to appearance but you could use it on the backside of the trim.

[Ratwagon1600]

Real world experience I hear you say, I'm glad you asked.

 

Flatcat pretty much nailed it, and from my own experience.

 

First, my plastic welder and a sample of the three types of plastic weld rods.

 

 

 

Theres a number of different plastic types and I can't find the chart I have which explains which rod is for which type of plastic but I primarily use the grey rods on automotive plastics.

 

I've done a fair few repairs on plastic bumper bars and plastic grilles. It's a bit of a dark art and as stated previously, needs a bit of practice to get it right. My preference on lighter gauge stuff like you want to fix is to do something similar to what athoose has recommended. You can plastic weld light gauge stuff but it takes a bit of practice to get it right.

 

Sometimes I also use fibreglass matting and resin on the underside to help bind everything together. Light sand and paint and unless you look rrreeeeeaaaalllly close, generally you can't tell it's been repaired.

[Tristin]

Thanks all... Id like to keep it as clean as possible since there is a bit of pattern on the exterior of the part. Ill come up with something...

 

 

Appreciate all the responses so far. 

[MikeRL411]

JCWhitney catalogs both a soft and a hard plastic dsah repair kit.  If you use a very small drill bit and "stop crack" the spreading crack, and wait to be sure it really worked you can proceed,  The kit includes a heating iron [think solder iron with a flat tip] and graining papers that can match almost any original dash graining patterns.  Worth a look.