If one goes back to the mechanics, lap shear test is the "pure shear" test cited.
But is is not easy to make a good specemens.
I believe ASTM books talked about adhesive lap shear test.
I am trying to pour uncured polyurethane into a mold and cure it to make a lap shear specemen for tensile testing.
Right now my mold produces not so good specemens (some, or most often with bubbles). I am search for a better mold design to make more reliable specemen for testing.
yes, testing...
Thanks for the great advice. I will try the chemical.
No, the part is just sitting there with my coating on, then the pinholes showed, becasue my coating is clear. The pits shows as pink color with bubble.
snavelyz
I am pouring polyurethane onto adhesive-applied metal coupon (19mm width, 75mm long)t make lap-shear specemen for testing the adhesive.
I appreciate your experience in designing a mold to make coupons.
Are there published design for a mold for rubber or palstic or silicone or polyurethane?
Thanks
I have a part of electroless nickel-plated aluminum.
They looked good as received, two months after I applied coating, pinholes showed up.
Are there method to detect the pinholes or plaing uniformity?
Thanks
snavelyz
1) conductive carbon black is one way but one has to add enough to make the polymer conductive. Too much carcon balck is hard to process and handle and alter the polymer procerty too much to be of use in some cases. Metal powders have other chemical problems.
2) Ther are conductive agents one...
Polyurethane is made from polymerization of isocyantes and polyools.
Changing the polyol and/or changing the isocyante composition will change the hardness.
Depending on your jacket reuirement and how much decrease in hardness you desire, there are three variables to manuveur: polyol(s)...
