benzoyl peroxide with methyl methacrylate??

[martainthebox]

Hi,
I did this experiment a while ago as my work experience where I embedded bones into plastic so that bones could be analysed and can't remember why certain things happened so was wondering if anyone knows?
so...
I polymerised methyl methacrylate with benzoyl peroxide as an initiator for radical polymerisation. I also added dibutyl phthalate as a plastisicer which should have made the plastic flexible. However my plastic then set over a couple of days and became hard and I was wondering how the plastic could become hard if I added a plasticiser?

Thanks

[marquis]

How much plasticizer did you add?

I'm not familiar with methyl methacrylate.  With PVC, it is not uncommon to add up to 40%, by weight, of plasticizer.   Smaller amounts, say 20%, can leave a plastic stiff.