We are a group of university students working on a project where we need to paint on polypropylene-based bags. However, we have found out that most paints do not stick on to this material and can even crack.
Does anyone have ideas on what paint we can use that will stick to the bag and will not come off for a long time to come? We are painting different designs so we will be using different colours on the material. Please advice.
Unfortunately you just can't paint polypropylene. It is a very waxy polymer, and as such very difficult to bond to.
nothing
find something sensible to do, the other chap was right.
NT
As you have found, paints don't stick to it. You need to get something that will bond into the surface of the plastic, perhaps a dye or some type of thermal printing.
Colin Bignell
In message , snipped-for-privacy@gmail.com writes
How long did that take to work out?
Best advice, find a different base material as polypropylene is a right bugger to paint. Nigh on impossible to adhere to and I don't think I'd want to be in the proximity of anything that could actually 'cement' itself to it without some heavy duty respiratory protection stuff.
You may want to speak to someone like European Colours or Clariant Masterbatch, they both supply products to colour plastics (European Colours supply dyes and pigments for use in printing processes IIRC and Clariant supply colour 'fillers' which are mixed into the raw plastic granules to colour the resulting product.)
Once the paint is applied it is a permanet DIY redo. But that goes for most plastics of the plastic variety. By definition it is plastic. That is, it deforms and reforms. That's what Thames Water have been finding out since Margarat Thatcher made them our megalomaniacs.
Those miles of yellow polythinorthick tubes will bend out of shape and if the road bed doesn't collapse on it as any road bed will, it will reform. Not only will this remove any paint not similarly inclined to stretch and rebound, it will form bottle necks that the water company will consider fair wear and tear.
Then they will apply for permission to rip up the road, the civil engineers will put it all back together again and after a few cars have driven over it, a new process of deformation will begin as a slice of road resection slumps beneath the waves.
So that's why they don't paint water pipes I presume. Mind you I can remember the good old days when you painted something to keep the water off. Nowadays these kids use high teckincal things like warm glow-balls and watermeters.
It will all end in tears no doubt.
But to answer the question, a car spray paint might do the job as the cellulose will disolve the top layer of the plastic and bond with it. I'm not sure how effective that will be though.
It is certainly nice and expensive. And I gather that is the general intention to make it look good. What other reason would one have to paint plastic I wonder.
Ah well, time for my horlicks. The home help will be here soon to apply them.
I can't wait.
You MIGHT try an etch primer with some success..
Find a GOOD model shop and ask for 'prymol'
This is a solvent that slightly attacks the surface of MOST plastics, and leaves a paintable deposit behind.
Car spray shops have similar sorts of stuff for spraying plastic bumpers etc.
Try priming it with a thin coat of superglue or plastic primer (from Halfords), then using thinned acrylic paint or fabric paint.
cheers, Pete.
Whats the brand name on the plastic primer stuff? Is it spray? Always looking for better ways to paint plastics...
You can etch using potassium dichromate first then should take a flexible paint, but dichromate is not nice stuff and rather specialist. I used to get plastic equipment front panels made and that is how they made the paint stick.
IIRC it's Halfords own brand, in grey or white. Probably not the best plastic primer available, but the best place to get it on the high street.
cheers, Pete.
Ta m8
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