You have been asked to specify criteria for a plastic part that ...

[tth]

You have been asked to specify criteria for a plastic part that is to be used as a storage tank on a truck that does home lawn fertilizer treatments. What are the most important criteria and why?
 
  What will be an ideal response?

Question 2

Some blow molded parts are made by injection blow molding. Describe this process and discuss at least three advantages that it has over other blow molding processes.
 
  What will be an ideal response?

Question 3

Explain and illustrate addition polymerization in a step by step description. Include a description of the inputs to the process and final products.
 
  What will be an ideal response?

Question 4

Why must a part be redesigned when its production switches from aluminum to composites?
 
  What will be an ideal response?

[enass]

Answer to Question 1

Can hold the liquid (permeation), no chemical attack, toughness

Answer to Question 2

A preform is created through the injection molding process, it looks similar to a test tube with threads on the top. This preform is then taken to the blow-molding process where the mold clamps onto it and heats allowing the preform to droop.
Once sufficiently dropping a plunge assist bar is inserted into the preform helping the plastic stretch and gain crystallinity in the vertical direction, the plastic is blown at the same time stretching the plastic in the horizontal direction also giving it strength. Three advantages: there is just enough material for the process to be completed, allows for better definition of part

Answer to Question 3

 Introduce the monomer containing a carbon-carbon double bond into the reaction vessel.
 Inject an initiator into the reaction vessel so that it mixes with the monomer, usually this happens through the formation of a free radical. Peroxide molecules are common initiators because they break a part when heated creating free radicals.

 The pi bond in the carbon-carbon double bond interact with the free radicals
 The peroxide free radical extracts one of the two electrons in the pi bond, breaking the pi bond, joining one of the carbons with the peroxide. Leaving the remainder of the pi bond as a free radical

 This free radical will try and form a bond with another monomer and the process keeps going until it is ended by the conclusions of the free radicals.

 Inputs: monomer (lots) and peroxide

Answer to Question 4

More steps are required to make a composite part as compared to an aluminum part. Things like balance and symmetry become a large factor for strength. Also Composite parts are usually created by layers, so tight tolerances from the original design will be determined differently from the differences between the compaction of the different layers. Etc.