A year later

[xiphmont]

Continuing the long-term obsession with adhesives and chemical bonding in general...

Folks might remember the printer ink project from a year ago. The biggest concern, all around, was that the composition of the inks was and is generally a trade secret. Ink usually has some alcohol component but you can never be sure which one, so choosing a plastic and an adhesive can be tricky. What is perfectly good for containing ethanol often won't work with methanol, or isopropyl. etc.

What I didn't expect was chemical welds to be susceptible:

Polycarb is rated for most alcohols and the tubes generally withstood the ink. However, all the chemical welds (IPS #40, indicated for polycarb) crazed badly and two tubes cracked all the way through at the point of the weld. I suppose several problems could be at play... The MMA content of the weld, surface stresses that chemical welding invariably causes, etc. To add insult to injury, the failsafe marine epoxy was also thoroughly undermined. It turns out that most consumer-grade marine epoxy... isn't rated for continuous immersion. Uhhh... what?

So, I've rebuilt things with industrial B45 epoxy, which is supposedly rated for Hell, High Water, and Alcohol:

Shortly after making the B45 versions I discovered by accident that despite claims otherwise all over the web, aquarium-grade silicone will bond to polycarbonate just fine (it does not adhere to many other plastics. Polycarb is not one of them). The bond isn't any more structural than silicone ever is, but the adhesion is very good. Silicone will absolutely stand up to anything in the ink. If the B45-bonded tubes fail, silicone versions will have to be next.

Another update in a year I suppose...