I have read some posts on Pinside on how to repair cracked and broken plastics. I never thought an of the posts offered a final resolution. But I think I have the solution many are looking for. HINT: It is not superglue.
After trying a superglue repair that did not work, I went to my local plastics supplier and asked what would be needed to repair cracked and broken PETG plastics. What she sold me was a product called Scigrip 3; She also sold me a syringe and needle to use for application.
This stuff works !! You probably can't tell it in the picture but that is not an industrial needle. That is a sharp needle like a doctor or junkie would use. This is all you need. Just push the plunger ever so slightly and watch the fluid flow.
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Here is a screen shot of the website. What you are looking for is Scigrip 3.
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What is neat about is product is that (in my limited experience---I have repaired two plastics, so far) that it flows like water and it does not eat the inks on the plastic parts. This is the backside of a plastic I just put back together. There are several cracks and one chuck was completely broken out. I did not do anything special; I was lazy and did not bother cleaning the cracked and broken areas before I started slopping on the adhesive.
This is the front side after the bonding repair. Trust me, the repair is solid.
After I made the bond, I sanded off the excess adhesive and smoothed the repair area. I did some experimentation and found that PETG plastics can be buffed and polished on a buffing wheel without melting. I still need to sand this area and polish a little bit more, but I now have a solid and serviceable part. It won't look perfect, but under glass it won't look bad.
For plastics repair, my opinion is that this is the way to go.