Which offers stronger ABS-to-ABS bonding, ultrasonic welding or use of solvent (acetone)?

[TheRingSmith]

Hello,
I have an ABS part with a standard energy director profile (per ultrasonic welding equipment maker Dukane's recommendation) that the plastic injection molder indicated that they cannot produce. The profile is a right triangle, where the base is 0.5mm and the height from center of base to apex is 0.25mm. The molder suggested that due to machining limitation, that the height be 0.5mm, creating an equilateral triangle profile instead. This would deviate from Dukane's suggested profile.

Would this taller energy director make it more or less optimal for sonic welding? I'm contemplating using acetone to bond the parts if sonic welding would not be possible if I use the molder's recommendation. The solvent would melt the ABS plastic together, similar to what sonic welding would do, but I'm not certain whether this bonding method would produce a weaker bond or not. Any advise? Thanks in advance.

Howard

 

[Demon3]

ABS is sensitive to solvents (via environmental stress cracking). They cause failure so I would recommend the ultrasonic welding instead.

Chris DeArmitt PhD
President - Phantom Plastics LLC

Consulting, ideas and training on plastic materials

http://www.phantomplastics.com

 

[CoryPad]

The solvent does not melt the plastic. The solvent dissolves the plastic. The idea is that the solvated plastic has some mobility and will bond after the solvent is removed via evaporation, diffusion, etc.

 

[D2S]

ABS pipe solvents contain ABS. The solvent penetrates the ABS at the surface and the polymers tangle on both parts and the solvent. Then the solvent (MEK, I believe) evaporates and you get a great bond. Your homes sewer lines are all ABS that are solvent bonded.

You could use laser welding if the design doesn't suit US welding.

I can't say which is stronger but I'm not sure I'd use the solvent bonding unless you had a male/female type connection to ensure good contact during bonding.

BTW, ABS works great with adhesives.

 

[Pud]

BTW, ABS works great with adhesives

It does indeed. Cyanoacrylates work a treat. If fact, apart from skin, ABS is about the only stuff I've found which bonds well with cyanoacrylates.

I would not use MEK for H&S reasons - liver damage I believe.

H

www.tynevalleyplastics.co.uk

It's ok to soar like an eagle, but weasels don't get sucked into jet engines.

 

[hendersdc]

I have run into the same pushback from a molder before related to the chisel profile on an energy director. An equilateral triangle works just as well, all that really matters is that you have a line contact between parts as opposed to a surface to surface contact to focus the energy and initiate the weld. Just make sure you have somewhere for the extra plastic to go since they also want to increase the height of your energy director feature and count on an increase in the weld thickness.