Need Help acrylic cracking after applying vinyl.

Solvent adhesive likely. Try a water based adhesive vinyl. Which clear did you print on?

 

Is your acrylic cast or extruded?

 

I'm going with a combination of the print (if it's solvent or eco solvent, it's still alcohol based) and solvent adhesive. Fumes will crack plastic just as easily as liquid in the right conditions.

 

I see that it appears to be cracking at the bend. I would hazard a guess that it has to do with a reaction between the ink or adhesive, AND the residual stress that is still in the acrylic from bending. Typically, slow cooling prevents this...it's very similar to the tempering process used in metal.

Not sure if you have this resource, but I thought I'd throw it out there anyway:

https://www.plexiglas.com/export/si...loads/sheet-docs/plexiglas-forming-manual.pdf

 

Is it possible that they were cracked before you applied the vinyl and couldn't see the cracks without color behind the acrylic?
The only thing I have ever heard of cracking acrylic is acetone.

 

its the flame polishing, I always use a buffing wheel with solid compound to polish edges and have never had cracks.

 

Alcohol will crack extruded, and it's less likely with cast.

How much of a bend does your acrylic have? Have you tried cast if it's less than 45 degrees?

 

any solvents on cnc cut & flame polished acrylic will crack plexi
there's a thread somewhere here discussing it, youtube vids explaining it as well, but apparently the flame polishing creates tiny pores of stressed acrylic and the solvent glides up into, expands, and cracks.

 

If you cut the extruded with a blade that makes minor chips and then flame polish like Mike Pro mentioned it will crack all over with any chemical like Windex which has ammonia. When you flame polish your just melting the edge, polishing the edge smooths out and cracks or chips. Or you got some crap acrylic, I always use cast but have use extruded in the past with no problem. People like the flame polish because it is faster but on thick pieces it does not work as well as polishing with wheel and compound.

 

How long after printing did you apply the white vinyl? If you trap the solvents from the ink by laminating too soon, you can force the solvents to out gas through the clear and adhesive.

 

Flame polished + Wet Ap = cracked acrylic