Based on the chemical structures and make-ups of polyurethane and ...

[jazziefee]

Based on the chemical structures and make-ups of polyurethane and polystyrene, how would the flame tests of these two materials differ? What would you expect to happen in the presence of a flame source? Describe flame color, smoke characteristics, and overall flammability.
 
  What will be an ideal response?

Question 2

How does high crystallinity in a resin affect the way the resin must be injection molded? Consider each of the stages in the process, i.e. from hopper to post-handling. What are the effects of narrowing molecular weight distributions?
 
  What will be an ideal response?

[yasmin]

Answer to Question 1

Polystyrene contains a benzene ring which helps determine the characteristics of this material. In a flame in will burn readily and have a yellow flame that is dark and gives off sooty smoke.
Polyurethane contains two monomers with at least two reactive groups. As a thermoset or elastomer it has a poor high temperature stability which leads to the

belief that it is flammable and would burn bright with less smoke or none, and would be black and sooty.

Answer to Question 2

The higher the crystallinity the higher the possibility for shrinkage, so the injection pressure would probably need to be increased and an increase in holding time.

[jazziefee]

Thank you!

[yasmin]

Always glad to help...