In your attempt to mold a part in shorter molding cycles, you ...

[cookcarl]

In your attempt to mold a part in shorter molding cycles, you have been lowering the temperature of the mold using chilled water. You find that the strength of the acetal part has decreased significantly under the cooler mold conditions. What is the cause of the problem?
 
  What will be an ideal response?

Question 2

You have been assigned to select a polymer for a wall plug. Your choices are PET and Polypropylene. Discuss what you would expect in electrical properties, what physical property requirements would be required, and which polymer might be the best choice.
 
  What will be an ideal response?

Question 3

Compare polycarbonate and polystyrene in the following properties and explain your answer on a molecular basis: tensile strength, impact toughness, melting point, abrasion resistance, clarity, solvent resistance, and cost. (Note: This question could be applied to any two polymers.)
 
  What will be an ideal response?

[qytan]

Answer to Question 1

The strength of an acetal part relies greatly on its crystallinity. The crystalline areas form as the part cools. While still warm the amorphous regions of the part have enough energy that they can move locally and form into crystalline areas. When the speed of cooling is increased, there is less time for these various crystalline areas to form. The parts will maintain an amorphous nature.

Answer to Question 2

You would expect the complexity of the PET chain to significantly decrease its conductivity compared to polypropylene. The crystallinity of polypropylene may also slightly increase the conductivity of the PP. The physical requirements would have to do with the forces that are applied on the wall plug. The main forces are

applied when an appliance is unplugged from the wall socket. These forces might include tensile, flexural and maybe even torsional forces, all of which would need to have greater cyclic strength than single instance, max load strength. PP would be the most logical choice for the wall plug for reasons such as resistance to stress cracking and lower costs as compared to the PET.

Answer to Question 3

PC is higher in tensile impact, melt point, abrasion and cost. Clarity and solvent resistance are closely comparable. Having the benzene in the backbone of the chain allows for forces to be more easily transmitted along the chain. Where the benzene ring is a pendant group those forces are not as easily transferred from one chain to another.

[cookcarl]

Both answers were spot on, thank you once again

[qytan]

Great! Please up vote