how to make a hard plastic baseball helmet or at least hard plastic?

[clemente h]

i need to no how 2 make a hard plastic helmet for a project or at least how to make hard plastic i doesn't really need 2 b a helmet but at least hard plastic since i need to c what materials absorb the most impact.....if off the top of ur head can u think of words that i can look up as research 4 a project lik dis for example like velocity or impact but in a way related 2 this project...thx