Page 4 of 4

Posted: Fri Jul 29, 2011 10:02 am
by saefroch
In my experience, epoxy will ignore grease. It sort of pushes it out of the way. The only things I've found that it won't adhere to are polyolefins, commonly used to make heat-shrink tubing.

Posted: Fri Jul 29, 2011 11:47 am
by aEx155
saefroch wrote:In my experience, epoxy will ignore grease. It sort of pushes it out of the way. The only things I've found that it won't adhere to are polyolefins, commonly used to make heat-shrink tubing.
If that's the case, how do people cast epoxy pistons if grease doesn't work?

I know that epoxy has a hard time adhering to PET (the plastic that soda bottles are made from), so I'm not sure if I want to glue a PVC fitting onto the bottle or cast threads with it.

Posted: Fri Jul 29, 2011 11:53 am
by jackssmirkingrevenge
aEx155 wrote:The greased bottle would be inside the fitting, and I would pour epoxy between the bottle and the fitting. That way I would have a bottle-PVC adapter instantly.
Just make sure the bottle doesn't have an interrupted thread, otherwise you're not going to be able to get it out.

Image

Posted: Fri Jul 29, 2011 11:54 am
by Gun Freak
I know that epoxy has a hard time adhering to PET (the plastic that soda bottles are made from)
Really? I was gonna cast some epoxy around a bottle for part of my stirling engine... :?

Posted: Fri Jul 29, 2011 11:59 am
by jackssmirkingrevenge
PET is flexible and can't really be abraded, not a good candidate for epoxy adhesion.

About threads though, I've cast them in epoxy before to fit a suppressor I made on my Yunker:

Image

Image

For my ghetto BBMG, I had epoxied a bottle cap in a larger plastic cap as the female thread:

Image

Posted: Fri Jul 29, 2011 12:03 pm
by Gun Freak
Thanks for the info on PET, I'll have to find a different cylinder material. Suggestions for ~3" diameter clear pipe?

Posted: Fri Jul 29, 2011 12:45 pm
by jackssmirkingrevenge
Gun Freak wrote:Suggestions for ~3" diameter clear pipe?
the dessicant cartridge on our FT-IR spectrophotometer at work?

Posted: Fri Jul 29, 2011 1:56 pm
by Gun Freak
Yeah I'll go dig one out of my closet :lol:

Posted: Fri Jul 29, 2011 7:15 pm
by aEx155
Gun Freak wrote:Yeah I'll go dig one out of my closet :lol:
If you don't use epoxy you can still use a plastic bottle. Polyurethane-based adhesives do a better job of adhering to the plastic, and one of the most commonly used ones (in water rocketry, for gluing bottles together for longer pressure vessels) is PL Premium Construction adhesive. It does foam a bit, but if that isn't a problem, it's something you can use. Another, slightly weaker (but non-foaming) alternative is Sikaflex 11FC.

Posted: Fri Jul 29, 2011 11:33 pm
by Gun Freak
I'm gonna put a bit on a bottle and see how well it adheres. It might be good enough for my purposes.

Posted: Tue Jun 25, 2013 10:36 pm
by dart guy
i have an idea
do you think that if you fiberglass a thin pvc pipe it would make it hold more psi ? if so i think i would try that for my l96 plans under "want to build but plans suck" in the pematics fourum
_________________
i feel so usless on spudfiles (ha ha fake sig)