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help with cracked plastic
  
 
jaredcolletti
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p.1 #1 · help with cracked plastic


Years ago my Sigma 70-200 lens rolled off a shelf and landed, front element first on a 45 degree angle on the seam of these tiles. In short it hosed the threads and dented the plastic. It has now progressed to a crack that runs just barley above the front elements and its about 1.5 inches parralel to it.. The lens still functions fine but if this crack progresses it will cause the element to fall out.I used taped then super glued it down but it didn't last long.


Question: What can I use to fuse these peices of plastic back together that will hold (like an epoxy, model cement or something)? I need to pin the plastic down in place. I worry that when I pull it out of my bag or catch it on something it's going to be ruined. Any advice?

thanks guys,
Jared

I have no way to post a pic right now as I am at work.



Apr 20, 2014 at 06:41 AM
Paul Mo
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p.1 #2 · help with cracked plastic


If you are intent on glueing it you could try a small amount of PVC cement, or perhaps better still model glue.




Apr 20, 2014 at 08:42 AM
jaredcolletti
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p.1 #3 · help with cracked plastic


Thanks Paul Mo, its not that I'm intenet on glue per se but I'm trying to avoid multiple
appempts that might gunk it up. PVC is a good idea. I've never used modeling glue so
I'm not sure of the cosistency but its probably a good idea to mask off the element in case it bleeds through a bit.

any other ideas?



Apr 20, 2014 at 09:30 AM
jaredcolletti
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p.1 #4 · help with cracked plastic


Found this article:
http://info.craftechind.com/blog/bid/323475/Stick-to-it-A-Guide-to-the-Best-Glue-for-Plastic

"The Best Glue for Plastic: JB Weld PlasticWeld- This glue bonded nearly every material perfectly, with the exception of Teflon to itself (not surprising given the materialís use for its non-stick properties).
It spread to create a gap-free bond, filling in all the available space for strong adhesion that just wouldnít quit, even after we tried desperately to separate the parts. The only downside of PlasticWeld is that itís a two-part epoxy which must be mixed in equal amounts to form the adhesive, which can get messy. It also sets quite quickly, which can be either a pro or con depending on your project"



Apr 20, 2014 at 09:40 AM
xnavyguy
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p.1 #5 · help with cracked plastic


You might want to try a plastic adhesive called Weld-on #4 this will fuse the plastic back together quickly and the bond is amazingly strong. Just a few drops will do the trick.


Apr 20, 2014 at 10:51 AM
 

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jaredcolletti
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p.1 #6 · help with cracked plastic


thanks xnavyguy, where might one procure such an item? Lowes, Walmart?
thanks again
jared



Apr 20, 2014 at 02:29 PM
xnavyguy
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p.1 #7 · help with cracked plastic


It's not normally carried at the big box stores....Weld-on does sell PVC adhesive at those stores but it's NOT the same stuff and won't work for your lens.

Check out your yellow pages for acrylic, plastics or plexiglass companies in your area...they'll carry it. If you can't find it locally you can find it on amazon or other distributers online.




Apr 20, 2014 at 02:52 PM
Danheman
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p.1 #8 · help with cracked plastic


+1 on JB Weld. Be careful to not put too much though. I have some plastic pieces holding now for 2 years with it.


Apr 22, 2014 at 05:41 AM
Erikgn
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p.1 #9 · help with cracked plastic


If it's possible to place a thin piece of plastic over the crack and glue that down to the lens, instead of putting glue/cement on the crack itself the bond will be much stronger, but maybe that's impossible given the crack's location. With any type of glue, surface area is your friend -- the more surface that is covered by clue the stronger the bond, regardless of the type of glue.

I'd second using a plastic epoxy (like JB weld) and would shy away from PVC cement since that's meant to bond a specific type of plastic (pvc) and does so by dissolving some of the plastic - and I don't think the lens is pvc.



Apr 25, 2014 at 02:42 PM





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