Greater variations in mechanical properties in neat polymer?

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#1

Hello all. New to the forum.

I had a general question. In my lab we make composite films with different fillers. Me and one of my lab mates noticed that we find the greatest variation in mechanical properties in neat polymer (she works with epoxy composites and I work with polyvinyl acetate composites) compared to the filled materials (i.e. the error bars are larger in neat polymer mechanical properties than filled). We both cast our films from solution.

I tried to find some references to see what the explanation for this might be, but I haven’t had any luck so I figured I would ask.

I figured something about the filler is making the properties throughout our materials more uniform, but I guess is was trying to find a more “scientific” answer. Any help is appreciated. Thanks.

#2

Depends on processing, mixing, and metering. If not mixed well, then a neat resin can have variations. Those variations can be highly different, just because only the resin is providing the data. Add a filler, and you can cause the filler to interact with everything else around it, and be stronger, even in a weak spot, leading to a more overall even number.
Bout as scientific as I can go :wink:

#3

Thanks for the response.

Yeah, I was thinking along those lines also. I am not sure why my neat polymer would not be as well mixed as the composite polymer solutions (I would think it would be harder to mix a composite solution just because of the additional component). And I use the same procedure for both.

#4

Often fillers with help the polymer mix better. Since you have the testing equipment you could perform test samples that have been mixed at various lengths of time and accuracy. If this reveals a trend then you may have discovered the reason. If the test results are still erratic then at least you know what isn’t the problem.

BTW, I always measure my test sample resins to within +/-.03 grams.