Author Question: Why is the temperature raised in order to achieve crystallization in PET? Is that temperature higher ... (Read 109 times)

evelyn o bentley

  • Hero Member
  • *****
  • Posts: 564
Why is the temperature raised in order to achieve crystallization in PET? Is that temperature higher or lower when the PET has been oriented?
 
  What will be an ideal response?

Question 2

Discuss the choice of materials for frying pan handles.
 
  What will be an ideal response?



kardosa007

  • Sr. Member
  • ****
  • Posts: 300
Answer to Question 1

In any material, especially one in which the polymer repeating unit is large, energy must be added to the system to allow sufficient molecular motion to align the molecules for crystallization. This is known as the thermodynamic limit of crystallization. If the polymer is oriented, some induced bonding has been created that gives the structure stability. Therefore, to rearrange into crystals, more energy must be added than if the polymer were amorphous. Therefore, the oriented polymers require higher temperatures to crystallize than the nonoriented polymers.

Answer to Question 2

Plastics or ceramics would be better than metals because the metals would conduct the heat and burn your hand. Ceramics are quite brittle, so plastics would be the first choice. Among the plastics, most are good thermal insulators, but the thermoplastics would likely soften or melt when the pan got hot. Therefore, thermosets are the likely group of plastics to consider. Within the thermosets, some properties that might be important are low flammability, low cost, and stiffness. Phenolics seem to be a good choice. The potential drawbacks of phenolics are color (the part will be dark) and filler



Related Topics

Need homework help now?

Ask unlimited questions for free

Ask a Question


 

Did you know?

The U.S. Pharmacopeia Medication Errors Reporting Program states that approximately 50% of all medication errors involve insulin.

Did you know?

The heart is located in the center of the chest, with part of it tipped slightly so that it taps against the left side of the chest.

Did you know?

The Romans did not use numerals to indicate fractions but instead used words to indicate parts of a whole.

Did you know?

GI conditions that will keep you out of the U.S. armed services include ulcers, varices, fistulas, esophagitis, gastritis, congenital abnormalities, inflammatory bowel disease, enteritis, colitis, proctitis, duodenal diverticula, malabsorption syndromes, hepatitis, cirrhosis, cysts, abscesses, pancreatitis, polyps, certain hemorrhoids, splenomegaly, hernias, recent abdominal surgery, GI bypass or stomach stapling, and artificial GI openings.

Did you know?

Amoebae are the simplest type of protozoans, and are characterized by a feeding and dividing trophozoite stage that moves by temporary extensions called pseudopodia or false feet.

For a complete list of videos, visit our video library