[Beowulf] materials for air shroud?

[David N. Lombard]

On Tue, Sep 13, 2011 at 02:05:30PM -0600, mathog wrote:
> FYI,
> 
> Finally, I tried gluing two pieces at right angles using a high melt 
> hot glue.  The hot glue gun
> claims to run at 395F, and the glue stick was nothing special, just 
> generic high temperature
> hot melt.  Mixed results.  After it cooled and was allowed to set 
> overnight I tried to
> tear the two pieces apart by hand, pulling in opposite directions, and 
> they held together.
> However, I was able to snap the pieces apart by folding it at the 
> junction.  (Applying quite
> a lot of torque to the junction.)  The glue completely let go of the 
> top of the "T", all of it
> stayed on the vertical part.  At this point it was easy to peel the 
> rest of the glue off.
> Seems like the bonding was good perpendicular to the surface, but 
> pretty weak
> parallel to it. If the piece wasn't physically abused it would likely 
> hold together in an
> air shroud.  I had read somewhere that the hot glue melts the 
> polypropylene so that it was
> effectively a weld, but that is not how it turned out with this glue.  
> Neither piece of plastic
> was distorted where the glue had been, so clearly not melted.  There 
> are specialty hot melts made
> of polyethylene or polypropylene, and those may actually weld this 
> material.

This is my expectation with /consumer/ hot glues--they're good for
temporary work, but are not a long-term adhesive.  

Did you try some of the hobby plastic adhesives?  Plastruct has a "Plastic Weld"
solvent cement. They list ABS, Butyrate, Styrene, Acrylic, and "more".
Perhaps "more" includes your propylne.  Another brand is "Tenax 7R". The
former is MEK and the latter MC; both need careful handling.

Finally, you could try the PVC Priming Fluid or even PVC Pipe Adhesives.

These are all solvent glues and will weld the materials.

-- 
David N. Lombard, Intel, Irvine, CA
I do not speak for Intel Corporation; all comments are strictly my own.