painting plastic mudguards/fenders ?

[NBC]

hi all,

i had a search on here, and i've seen a fair few bikes with painted honjo / berthoud etc metal mudguards, though very few with SKS chromoplastics or similar

i was wondering if any of you had any experience with painting plastics, and could give me some advice or tips ?

i don't spray myself, but don't want to waste time / money with professionals if it's not a good idea

any help is greatly appreciated

thanks

NBC

[Nooch]

i don't know much about it, but i'd figure you'd want to have a flex agent added to the paint -- if it was a single color i'd go to an autobody shop, and have em paint em like front bumper..

[one60]

a few years back Ventus Custom showed a blue road bike at NAHBS with painted to match (plastic) roadracer MK2. (sorry, can't get links to work)

I painted a set myself using a krylon spray paint formulated for plastics with good results...nothing show quality but good enough for the rain bike.

[Rody]

Yes, you can consistently paint plastics.

The hurdle that comes with most poly plastics is that a release agent is built into the formula.

To prep plastics for paint, you must first provide a mechanical tooth by roughing up the base with a maroon scotchbrite pad, then wash the parts with a mild detergent and rinse with clean water.

Then, take a butane torch and lightly go over the part, heating it until you begin to see a "wet" film or change of color occur. This is the release agent being drawn out of the surface. From the time this transition begins, you have about 30 seconds to spray it with concentrated alcohol and wipe clean.

Continue over the entire part with the torch and subsequent alcohol wipe until all exposed surface area is completed.

Shoot with an etching primer and paint as desired.

rody

[Mark Kelly]

Rody

Your method works but not for the reasons you suppose; Corona treatment would work just as well and that doesn't remove any "release agent".

What you are actually doing is raising the surface energy of the polymer itself by flame treatment, which explains why it's most effective on low surface energy materials like polyolefins (polypropylene etc). There's a good review in the journal Polymer.

[Rody]

What you are actually doing is raising the surface energy of the polymer itself by flame treatment, which explains why it's most effective on low surface energy materials like polyolefins (polypropylene etc). There's a good review in the journal Polymer.

Dude, glad you understand that shit, I'm running on the simple hillbilly mentality...don't know what to do? Hit it with fire, that'll fix it!

:)

Thanks for the insight, very interesting read.

rody

[afwalker]

who is one 60? please update your name/signature else be relegated.
Whoa, that was a heck of a scientific read:) loved it
cheers
andy

[Mark Kelly]

Dude, glad you understand that shit, I'm running on the simple hillbilly mentality...don't know what to do? Hit it with fire, that'll fix it!

Surprising how often that works.

If I can summarise the relevant parts of the article:

Flame treatment of the plastic surface modifies some of the molecules at the surface so they are more reactive and will thus give a better bond with adhesive / paint / ink.

At the same time the heat can also concentrate any additives at the surface which can foul the process.

Your process thus has two halves: the flame treatment improves the bond strength and the the immediate solvent extraction of the additives prevents the fouling.

Some of you hillbillies are pretty bloody clever.

[blasdelf]

PROTIP: using green scotchbrite to knock the gloss off looks terrific even when filthy



works really well on SKS and in my case Planet Bike, use water on the second pass

next time I'm gonna try it with an orbital sander

[duanedr]

PROTIP: using green scotchbrite to knock the gloss off looks terrific even when filthy

is that a bike carrier attachment for dragging a bike behind a bike? 10-15 years ago, riding along the bike path between Marymoor and Seattle, I ran across a guy dragging his track bike from Seattle out to the track for Friday night racing. he hose clamped a front hub to the back of a rack on a touring bike and then attached the fork of his track bike to the hub. he had his front wheel attached to the side or something (I forget now...) so rad... It was one of those moments that expanded my understanding of what a bike was capable of doing. Nice bike by the way! looks like a great seattle rain bike!