anybody who has a piece of broken plastic with which to deal on your car (or, i learned from continually getting off my motorcycles before they were stopped.) the best way to deal with plastic is to use baking soda and super thin super-glue. fill crack or chips with baking soda and apply glue. the preferred applicator here is a piece of tube filament. i get mine from a local hobby shop who makes their own super-glue but fly tie supply places have it. you can build up (in thin coats of baking soda) to 1/4" thick or more. i have made full loops with this method for the cowling of a motorcycle, dropped the bike again and the loop survived while the rest of the piece suffered severe trauma. one of the advantages to using this method... makes no difference what type of plastic it is. super glue does not discriminate.

Interesting. Do you sprinkle the baking soda on the crack and dab the super glue on top of that or do you make a slurry of the combination? Pictures?

Actually - the "best way" is to do what's called "Plastic Welding".

- wherein you get the proper solvent for the particular type of plastic of which the broken part is made, some scrap pieces of that plastic in the same color & use the solvent to melt the scraps & use that to "weld" the broken bits together, which is about 90% of the original unbroken part's strength, & nearly undetectable - if not completely.

Think of the old Testors clear liquid polystyrene glue on plastic kit models.

Auto Restorer magazine did a "how to" article on it a few months back.

The Super Glue with or without baking soda (a "filler") will eventually break, because it doesn't realign the plastic molecules when soft then they re-harden into a new crystalline net, like the proper solvent will.

actually "the best" way IS NOT plastic weld but i appreciate your critique. i ve plastic welded, epoxied and super-glued. no comparison and you don t have to worry about what kind of plastic with which you are dealing and you can just go to a hobby store and get the supplies. the combination of baking soda (which actually catalyzes the super-glue) and super glue is actually stronger than most plastics and it is sandable. yes it doesn t look like most plastics. in some cases (ducati track bike) i let the scars show. in some cases (67 Norton P11 special) i sanded and painted and on the ninja that refused to stay upright, i sprayed the entire thing a different color from the original. hated that green. i have yet to work with a plastic in a car or bike application that is as strong as the baking soda- supe glue combination. as i ve said, i ve seen the plastic around the mend fail but never the actual seam. apply the baking soda, soak with supe glue. supe glue penetrates very quickly so you don t need much. again, use the thin stuff. this stuff is used regularly in knife making and fly tieing. in each case it fully penetrates the wood or the hair or thread strands or whatever. i, eastbay851, guarantee that the rest of the relay board cover will fail before the repairs. of course i do all the repairs on the rear of a surface if i can. and never, never work with supe glue naked.

i always wonder about critiques on various forums. i don t offer anything unless I VE DONE IT. i don t opine. i observe. i lived in socal for quite awhile. implied expertise is contagious down there.

eastbay851 e.l.e.

No hobby shop "makes" there own CA. They buy a generic bottle from a supplier that prints the labels for them. CA- or superglue - reacts with the baking soda, we call it a kicker. The problem with the baking soda is it will leave a white residue with the CA. There is an off the shelf kicker that is in a bottle that will help it stay clear. If you look at the rest of the glues at the hobby shop, they sell a "canopy" glue that is made for plastic and works well. I usually use pipe cement for all my plastic gluing jobs.

come on guys, please, there be no best method to bond or repair "plastics" .....the best method to pick to use depends on many factors.... first of which is what type of plastic is to be repaired. super glue wont stick to all plastics, nor can all be welded, nor epoxy glued. Additional reinforcement maybe needed in some repairs, even screws or pins can be warrented, or fillets of material, cosmetic considerations are another factor in picking the 'best method" for a particular job.

at anyrate an in tersting idea on teh baking soda. would the thickned super glue sold be any different in properties than the home brewed thin glue with the soda?

I have a plastic welding iron with various types of plastics (abs, pvs, etc etc) that I've used on different repairs. The military uses the same brand I have to repair plastic fuel tanks on some vehicles. I'll have to look to see what brand I have since I haven't used it in awhile. To be continued.....

Hobby shop super glue is not as diluted down as the grocery store stuff. There are usually 5 types available, super thin, thin, medium, and thick or gap filling. Then there is foam safe stuff. Super thin is a PIA, it will wick right through whatever you are gluing and bond your fingers to the work. Thin is used for wicking, put two pieces together and then glue, med will do the same thing but fill small gaps, thick you put the glue on then stick the pieces together. Usually kicker is used on the gap filling stuff, since it takes a while to dry. For those that build airplanes, Anchor Bond makes the best of the CA glues, and the nicest Marcaptain free Epoxies. ( non stinky)

Model airplane building and CA brings up memories. The smell of glow fuel and balsa dust ( hopefully not at the same time, i.e. crashing)

Re: plastic repair, i like fiberglassing the back side and using epoxy, the hobby grade stuff. Poly resin makes for no fun and no safe. MEK and all that badness.

When fiberglass isn't an option I would like to learn plastic weld and still need to try that old model airplane cement that was acetone based. Similar to dissolving toothbrushes in solvent, I remember seeing or reading of that somewhere. I couldn't tell you where though.

on old iron and or even a candle and on old knife can be used to weld thermoplastics some times you can 'harvest" filler material for your weld by scraping excess plastic off of on other area of the same part, thus assuring same type/ color of plastic for the repair

ok ok. i was wrong and i ve never plastic welded, epoxied or even super glued. but in the future.... i m super gluing everything plastic in a car or motorcycle cause i ve never done it before and it has never worked on the track, in the garage or in my bathroom for that matter. but i ll bet.... next time any of you have to fill a crack you re going to go out and buy my acme marine and navy plastic welder to take care of that battery cover.... hit me back the minute you do. or hit me back the minute you decide to use a bottle of supe glue and baking soda for under 10 bucks. you guys crack me up. have any of you ever really spent some time on a track? i love a new forum. if you haven t figured it out yet, and not that you care but.... i m new to the 914 experience and the "porsche club" talkies but no walkies. by the way i don t exactly have a porsche engine in my "porsche" but the porshies all like to talk to me about their "vast" experience and then say "hey there, i m not sure i ve seen that porsche engine before. is that the 4 cammer? i ve always wanted to see one. look mayble a four cammer...." awwww porsche owners.... i was warned to stay away from the forum.... so if i give out b.s. advice do i become an "advanced member?" oh boy. oh boy.

I've been doing that for years.
Even my dash-board got the soda+superglue treatment.

Two remarks: it seems that thicker superglue is better, like the gel one. And never drop superglue on uncured soda - it will form a bubble.

Jeeze, somebody needs to take a chill pill ...

This was what, your third post here and low and behold someone dared to disagree with you and now the whole "world" is out to get you?

Wow, just wow ... Some people ...

not sure what you are saying here with "thicker is better." i haven t been able to get the wicking to work with the thicker stuff. as you said... hits the outside layer and bubbles. am i misunderstanding something here.

does it really matter how many posts i have here? i guess to the senior members. look b.s. is b.s. you could tell by the jargon and the topic really. this topic has nothing to do with real driving or wrenching so it attracted a couple of those boys who go out to the internet, find some words that make em sound like they know what they are talking about and post to see themselves post. you all may carry on now. thank god we solved the plastic repair issue. very big deal that. (i ll bet all of you try the supe glue solution before the others.... he he, he he, he he. (my attempt at beavis and butthead.))

Hey, i wasn't knocking your idea at all. Whatever works in your situation is great by me. I've been using CA before it was available to the general public- Eastman 910 anyone? I was just trying to clear up some of the superglue questions and add that a kicker (does the same thing as baking soda) is available in a clear liquid.

You said it yourself. BS is BS.

Have a nice day!

Most of the time I like hearing about ANY way to fix plastic. I've been smearing glycerin on mine for years. But about spirited posting...

I have a few rules I like to follow.
1. I assume that whoever lurks here wants to both learn and share the things that have worked and failed. Sometimes that includes speculation. In that case it should be clearly marked speculation.

2. If I've had a bad day or too much coffee I only READ posts until I feel better, unless I respond with the facts and only the facts. I don't dissect why someone answered the way they did unless it's positive and playful. In that case I enjoy responding in kind.

3. I ignore angry folks completely. They spread poo everywhere and are reluctant to clean it up.

4. If I think someone has posted something incorrectly I ask them about it respectfully. They may know something I don't or were simply wrong. I'm ok with both. We get to the answers in a friendly way with that method. Then I don't mind sharing a scotch (or coffee) with that person when I meet them at an event!

Anyone here that has followed my posts has noticed that I can be wrong now and then (darnit). I'm good with when friend corrects me but does it with respect. Anyone else can check out the mistletoe on my coattails.

Good luck!

There's another thread in the sandbox about sugru... We're waiting for the shipment to show up at the thread author's place so he can tell us about using it. It looks like it will be fun to try out as well.


On the BS and SG idea:

Does it cure to hardened state, or a soft state? someone mentioned dash repair with it...

It cures hard, but not quite as hard as pure cyanoacrylate. It's a bit more sandable.

Have you ever tried Micro Balloons?

micro balloons link

I used to use this stuff back in the day fixing RC helicopter canopies and RC airplane fuselages. It is mainly used with epoxy, since it is coarser than baking soda, but is pretty handy stuff. Sands down to a very smooth finish.

I have, they are pretty cool. Used to fill my solid wings with them to sand out blemishes, but i used it with white glue usually, the epoxy or CA with them was to hard to sand around the balsa.

this may have something to do with your method. i have always finger trowelled the baking soda into the crack and "soaked" this with very thin supe glue. i know others who swear by the use of the more viscous stuff and adding the baking soda after. since i ve never tried the latter....