Plastic eyeglass frames become friable with time going on.If it is broken,use the super glue and it works fine,but donÃ¢â‚¬â„¢t put too much on or it wonÃ¢â‚¬â„¢t glue together.Then let it dry.Finally use acetone and a cue tip to smooth it.
I have never broken the frame of my glasses. So I don't know which kind of glue works best on fixing it. But my roommate broke the arm of her glasses. She tries to fix them by some kind of glue. But it doesn't work. Later, she took her glasses with her to see an optician. The optician told her that there wasn't a way to fix her broken glasses. So she bought a pair of new glasses.
You can use superglue to fix your glasses. I found this for you. You can have a look at https://www.instructables.com/id/Repair-plastic-eyeglass-frame-with-thread-and-supe/. There are detailed procedures for you to follow. You may need to prepare some tools and articles first. Hope this helped!
You can use some construction adhesive such as liquid nails to glue a plate across the break on the inside. Then you can take a piece of metal or even plastic to glue it across the break. Remember to support the glasses. You can put some sand in a bowl to support the glasses if it is needed. And you must avoid putting some sand on your glasses. I suggest you to put a piece of plastic wrap on the top of the sand. Hope this helped!
I used super glue and it works fine. I put to much on and it dried on the plastic lens and i just use acetone ( not nail polish remover ) and a cue tip to remove the super glue. That was about 6 months ago and still no problems. Hope this helps.