« previous next »

Author Question: What are the structural features in the melamine monomer that lead to the very high hardness of ... (Read 9 times)

penza

  • Hero Member
  • *****
  • Posts: 1,022
on: Aug 19, 2018
What are the structural features in the melamine monomer that lead to the very high hardness of cured melamine resins?
 
  What will be an ideal response?

Question 2

Compare the processing differences of resole and novolac resin. What is meant by one-stage and two-stage resins?
 
  What will be an ideal response?


Carliemb17

  • Sr. Member
  • ****
  • Posts: 325
Reply #1 on: Aug 19, 2018
Answer to Question 1

The melamine monomer has three amine groups attached to the ring, with each amine group containing a nitrogen and two hydrogens. Each of these nitrogens is capable of being a crosslinking site. Therefore, the hardness in melamine plastics comes from the very high crosslink density that is possible because of the multiple crosslink sites.

Answer to Question 2

Resole and novolac resins are both types of phenolics. The resole resins are linear polymers that are cured simply by heating, while the novolacs must have a hardener added to them and then heated to cure. The resoles are, therefore, one-stage polymers, meaning that only one step is needed to complete the crosslinking, whereas the novolacs are two-stage polymers.


Related Topics

Need homework help now?

Ask unlimited questions for free

Ask a Question
« previous next »
 

Did you know?

Certain rare plants containing cyanide include apricot pits and a type of potato called cassava. Fortunately, only chronic or massive ingestion of any of these plants can lead to serious poisoning.

Did you know?

In women, pharmacodynamic differences include increased sensitivity to (and increased effectiveness of) beta-blockers, opioids, selective serotonin reuptake inhibitors, and typical antipsychotics.

Did you know?

Many medications that are used to treat infertility are injected subcutaneously. This is easy to do using the anterior abdomen as the site of injection but avoiding the area directly around the belly button.

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?

As many as 20% of Americans have been infected by the fungus known as Histoplasmosis. While most people are asymptomatic or only have slight symptoms, infection can progress to a rapid and potentially fatal superinfection.

Structural similarities between antimetabolites and their natural counterparts Structural similarities between antimetabolites and their natural counterparts
Key Features of Australopithecus africanus. Key Features of Australopithecus africanus.
The world has been horrified recently at a U.S. Congress so polarized and paralyzed that it cannot p The world has been horrified recently at a U.S. Congress so polarized and paralyzed that it cannot p
Membership in this subculture is not easily awarded. Not only must high-steel ironworkers prove that ... Membership in this subculture is not easily awarded. Not only must high-steel ironworkers prove that ...
Anxiety rises as needs are not met. Without resolution, anxiety may lead to frustration, and then, ... Anxiety rises as needs are not met. Without resolution, anxiety may lead to frustration, and then, ...
The developing and emerging nations have high rates of population growth The developing and emerging nations have high rates of population growth
Video: Introduction to Macular Degeneration

For a complete list of videos, visit our video library