qn30jEkPz7 Posted July 9, 2020 Share Posted July 9, 2020 (edited) 39 minutes ago, Roger Holden said: As far as I understand it, the yellowing variety were made from cheap PVC like industrial packing. But Falcon and others use better quality PETG which contains some anti-UV agents. Behaviour of PVC like that is a lot down to the plasticiser. Bisphenol-A and similar plasticisers added to it will oxidise with time to turn yellow and not-plasticise as well so the PVC becomes more brittle. Might be able to get it clear again but trimming would be a sod to do as the chances of splitting would rocket 15 minutes ago, Black Knight said: I use PETG plastic, usually re-cycled vac formed packaging for my vac canopies Just two weeks ago I went through my box of spare clear plastic and threw out about half of it as that amount had yellowed. In a closed card box stored in my flat, it went yellow. Probably for the best. Even if you were able to UV bleach them to break down the colour there is already oxygen damage done to break down some of the polymer chains so it’d have be less formable and more likely turn yellow again after heating Edited July 9, 2020 by LostCosmonauts Link to comment Share on other sites More sharing options...
Scott Hemsley Posted July 10, 2020 Author Share Posted July 10, 2020 Thanks again gentlemen. This has turned out to be an interesting thread, but after all is said and done, it looks like I'll be getting some proper materials to make a master and vac a new one. Scott 2 Link to comment Share on other sites More sharing options...
303sqn Posted July 10, 2020 Share Posted July 10, 2020 Biphenol-A is not a plasticiser, it is used to manufacture hard plactics such as polycarbonate. http://www.rheothing.com/2016/06/bpa-is-not-plasticizer.html 1 Link to comment Share on other sites More sharing options...
qn30jEkPz7 Posted July 10, 2020 Share Posted July 10, 2020 8 minutes ago, 303sqn said: Biphenol-A is not a plasticiser, it is used to manufacture hard plactics such as polycarbonate. http://www.rheothing.com/2016/06/bpa-is-not-plasticizer.html True, I was trying to tie back to a chemistry that most modellers know and trying to say that the plasticisers in PVC (probably a phthalate ester) will age and yellow similarly to an epoxy. I worded the comparison clumsily and agree Bis-A and F are indeed mainly used as the diglycidyl esters to make polycarbonates, epoxies and in hybrid resins with polyesters and polyurethanes. 2 Link to comment Share on other sites More sharing options...
Rick Brown Posted July 11, 2020 Share Posted July 11, 2020 Jeez, you lot lost me days ago! Run it by me again. 😁 Rick. 1 Link to comment Share on other sites More sharing options...
Luka Posted July 11, 2020 Share Posted July 11, 2020 Got a lovely CMK Attacker in the stash with the canopies still sealed in plastic, but they have severely yellowed nonetheless. Luckily I have nice and clear replacement canopies, but I'm going to try the sunlight trick on the originals just as an experiment. I did some vacforming with acetate sheet, and noticed that my home-made canopies come out way thinner than any aftermarket ones. So thin in fact that I could use the original canopy (polished up and all) as a master. Link to comment Share on other sites More sharing options...
Roger Holden Posted July 11, 2020 Share Posted July 11, 2020 I just read 2 VERY interesting methods for treating yellowed clear vacforms on a 1/43 car model FB page. One is to soak the part in a 50/50 mix of water and bleach for a few days. The other is to soak it in hydrogen peroxide. There are several people saying they've had good results.... 1 Link to comment Share on other sites More sharing options...
cngaero Posted July 12, 2020 Share Posted July 12, 2020 On 7/9/2020 at 5:30 PM, Rick Brown said: Still, my nails now look beautiful. Anything you'd like share with the group Rick? 1 Link to comment Share on other sites More sharing options...
busnproplinerfan Posted July 12, 2020 Share Posted July 12, 2020 7 hours ago, Roger Holden said: I just read 2 VERY interesting methods for treating yellowed clear vacforms on a 1/43 car model FB page. One is to soak the part in a 50/50 mix of water and bleach for a few days. The other is to soak it in hydrogen peroxide. There are several people saying they've had good results.... How long would it stay in the hydrogen peroxide? Link to comment Share on other sites More sharing options...
Roger Holden Posted July 12, 2020 Share Posted July 12, 2020 15 hours ago, busnproplinerfan said: How long would it stay in the hydrogen peroxide? Not sure; a while I think. It was a method being advocated by some French guys. Link to comment Share on other sites More sharing options...
busnproplinerfan Posted July 13, 2020 Share Posted July 13, 2020 4 hours ago, Roger Holden said: Not sure; a while I think. It was a method being advocated by some French guys. I'll have to give both a try, but I did read somewhere that they can't be cleaned and to make new ones. Just have to try I guess. Link to comment Share on other sites More sharing options...
lasermonkey Posted July 13, 2020 Share Posted July 13, 2020 I tried both Hydrogen Peroxide and bleach (and Ammonia on a separate occasion) on yellowed canopies some time ago with no effect. It may be that the peroxide concentration I had (medical use from a pharmacy) wasn't strong enough, but that's all I had access to. I think that once they've gone, that's it. It's a shame, as I have a lot of old, unusable canopies knocking about. Cheers, Mark, Link to comment Share on other sites More sharing options...
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