I sounds rather mundane, but you should it at least try some of the various forms of glue sold by the name of GOOP, available at Walmart's, K-Marts, etc.   Goes for about $ 3.50 a tube.  It does take about 2 - 4 hours to setup to full strength, which is perhaps a problem for your app.  But it is surprisingly strong, and not brittle.  It will stretch or twist before it will let go, and the bond to different material is often stronger than the glue itself. Although stubborn to "undo", it can be removed; a hot knife seems to work best.

How much stress is applied to the bond line in this case?

There is a "blue tape" that's used to hold semiconductor wafers during dicing operations that might work.  It's not really an adhesive, so there's no residue.  More like the stickers the tune-up places put on your windshield to remind you about the next service.

TTFN

Polyprop  is a plastic that can not be glued, it can only be. joined by welding.  Cheers DW

Thanks all for your input.  Since this is not structural, maybe the double sided tape will work.  we will try it.

Jesus is THE life,
Leonard

metman
You should also try hot melt glue. It will stick reasonably well to PP. Stick one corner of your sheet at a time. I am assuming there is enough flex in the sheet.
Buy one of those elcheapo hot melt glue guns from one of the K Mart or hardware type stores

Hot melt glue quite often is polypropylene as well, hence the reason it sticks well to polypropylene parts.  Essentially it is being welded to itself as brought up by corrosionman.  To get the polypropylene or hot glue shot (or both) to bond to the machine piece, the piece needs to have a rougher (pitted) texture to allow mechanical bonding.

ChemE, M.E. EIT
"The only constant in life is change." -Bruce Lee

Thanks folks.  Interesting thought.  I will pass it on as a possibility.

Jesus is THE life,
Leonard

Just a little feedback:
We use MDF (medium density fiberboard) on top of the platen.  The MDF is porous enough that the vacuum can pull through it to hold parts.  When we need to assist the vacuum with glue, we use 3M Hi-Strength Spray Adhesive.  As it turns out, this 3M glue states on the label:

Bonds laminates, kick plates, polyethylene, polypropylene , plastic lettering.

So I made a little test and came up with the following:

Shear strength:  3M Glue  7psi
                 3M Double Sided Tape 2.75psi

Jesus is THE life,
Leonard

What about drilling a grid of holes in the MDF, or simpler still, using peg board?

Take a look at this website.

http://www.fluoroseal.com/adhesion.html

Hot melt glue sticks are readily available, easy to apply, and should adhere reasonably well to your PP.  However, they may not remove as easily as you want.  BTW, HM glue sticks are almost never PP based.  PE and EVA are more common.

There are varieties of "palletizing adheisves" that are used to hold stacks of bags and boxes together in a pallet.  They are designed to resist lateral movement, but remove easily with some sharp impact.  Hot melt palletizing adheisves should adhere to PP well enough for our application.  Call any adhesive distributor and ask for a sample or box of hot melt palletizing adhesive.

There is a kind of labeling adhesive called "hot pick up" that is applied at about 250F.  It's very thin at this temperature and can be brushed on or drizzled on.  It's very brittle and can be easily removed.  Any adheisve distributor can get this for you too.

Double sided foam tape is an option, but it's expensive.

Tom Quinn
Adherent Laboratories

Thanks for clearing up what hot melt sticks are made of Tom.
Metman, to help the vacuum pull straight thru, do you seal the edges of the MDF ?

Metman....if the polypropylene sheets are flat and the cutting surface is flat, why not use something with high surface tension that can be wiped off, like high viscosity oil or Vaseline?  Will hold nicely if stresses are low and not much cleanup required.

Pressure Sensative Adhesive paper is often used in woodworking where you have to affix a block of wood to a rotating platen (such as for turning a bowl).  If you can't find it in a woodworking catalog, you could also try a metallographic preparation company (Struers, Buehler, etc.) for PSA paper for afixing paper to platens.