This topic contains a solution. Click here to go to the answer

Author Question: Describe a technique for forming a part with an outer coating and a different inner material using ... (Read 42 times)

@Brianna17

  • Hero Member
  • *****
  • Posts: 550
Describe a technique for forming a part with an outer coating and a different inner material using rotomolding.
 
  What will be an ideal response?

Question 2

Explain how polyethylene is crosslinked in a rotomolding operation.
 
  What will be an ideal response?



Related Topics

Need homework help now?

Ask unlimited questions for free

Ask a Question
Marked as best answer by a Subject Expert

raenoj

  • Sr. Member
  • ****
  • Posts: 340
Answer to Question 1

One method that will accomplish this formation of an outer shell is to mix two resins that have different melting points. During the rotomolding operation, the lower melting resin will become sticky first and coat the inside of the mold, thus forming the outer layer of the part. Later, the higher melting material will coat onto the shell and form the inner material. Another method is slush molding which one resin is put into the mold and poured out after a thin film has formed on the mold. A second material is then added to complete the part.

Answer to Question 2

Normally thermoplastics such as polyethylene cannot be crosslinked. However, if a peroxide or some other free-radical-forming material is added to the polyethylene and the temperature is raised, some hydrogens in the polyethylene can be removed and free radicals formed in their place. These free radicals can then react with crosslinking agents containing carbon-carbon double bonds which have also been added to the mixture. These crosslinking agents bond to the free radical locations on the polyethylene. Because the crosslink agents have at least two reactive carbon-carbon double bond sites, they can react with more than one free radical location and therefore tie together multiple polyethylene chains. Increased heat is needed to give the molecules the mobility to move together to form the crosslink bonds.




raenoj

  • Sr. Member
  • ****
  • Posts: 340

 

Did you know?

The word drug comes from the Dutch word droog (meaning "dry"). For centuries, most drugs came from dried plants, hence the name.

Did you know?

Asthma-like symptoms were first recorded about 3,500 years ago in Egypt. The first manuscript specifically written about asthma was in the year 1190, describing a condition characterized by sudden breathlessness. The treatments listed in this manuscript include chicken soup, herbs, and sexual abstinence.

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.

Did you know?

The most dangerous mercury compound, dimethyl mercury, is so toxic that even a few microliters spilled on the skin can cause death. Mercury has been shown to accumulate in higher amounts in the following types of fish than other types: swordfish, shark, mackerel, tilefish, crab, and tuna.

Did you know?

Adult head lice are gray, about ? inch long, and often have a tiny dot on their backs. A female can lay between 50 and 150 eggs within the several weeks that she is alive. They feed on human blood.

For a complete list of videos, visit our video library