MSE 4793 Homework 4 Exam Preparation Complete Study Guide with Solution 2025/ 2026 MSE 4793 Homework 4.pdf
Brie Heinsz
Composites
2/27/24
Homework 4
1. Why polymers (plastics) are most widely used as matrices in composites?
a. Polymers are used as matrices in composites due to their low cost, low density,
and high strength. Polymers also are resistant to corrosion and are fairly easy to
mass produce.
2. Draw the characteristic chemical groups for polyester and epoxy (draw as 2D
image, or like -CO-NH- )
3. Identify 2 or 3 significant advantages and disadvantages of polyester resins
versus epoxy in composites.
a. Polyester resins are lower cost and nontoxic, unlike epoxy resin before curing.
However epoxy resin is more heat resistant and more resistant to shrinkage than
polyester resins.
4. Describe the function of the initiator in polyester curing. If the concentration of
the initiator is 20% too low or too high (based on original dosage), what would
be the adverse effects? Would this significantly affect the end product
properties?
a. The initiator, usually a peroxide, catalyzes the crosslinking reaction by forming
free-radicals. This helps to transform liquid resin into cured polymers. An
initiator concentration of 20% is much too high, with the normal concentration
being closer to 1%. Too high of a concentration could cause premature
termination of the crosslinking reaction due to reaction with the unreacted
peroxide. Additionally, too high of a concentration causes too fast of a reaction
time. This can result in a rubbery finish, cracking, or brittleness for the cured
polyester.
This study source was downloaded by 1827175 from cliffsnotes.com on 01-08-2026 17:51:47 GMT -06:00
Page 1 of 3 MSE 4793 Homework 4 MSE 4793 Homework 4.pdf
https://www.cliffsnotes.com//study-notes/23828308
Brie Heinsz
Composites
2/27/24
Homework 4
1. Why polymers (plastics) are most widely used as matrices in composites?
a. Polymers are used as matrices in composites due to their low cost, low density,
and high strength. Polymers also are resistant to corrosion and are fairly easy to
mass produce.
2. Draw the characteristic chemical groups for polyester and epoxy (draw as 2D
image, or like -CO-NH- )
3. Identify 2 or 3 significant advantages and disadvantages of polyester resins
versus epoxy in composites.
a. Polyester resins are lower cost and nontoxic, unlike epoxy resin before curing.
However epoxy resin is more heat resistant and more resistant to shrinkage than
polyester resins.
4. Describe the function of the initiator in polyester curing. If the concentration of
the initiator is 20% too low or too high (based on original dosage), what would
be the adverse effects? Would this significantly affect the end product
properties?
a. The initiator, usually a peroxide, catalyzes the crosslinking reaction by forming
free-radicals. This helps to transform liquid resin into cured polymers. An
initiator concentration of 20% is much too high, with the normal concentration
being closer to 1%. Too high of a concentration could cause premature
termination of the crosslinking reaction due to reaction with the unreacted
peroxide. Additionally, too high of a concentration causes too fast of a reaction
time. This can result in a rubbery finish, cracking, or brittleness for the cured
polyester.
This study source was downloaded by 1827175 from cliffsnotes.com on 01-08-2026 17:51:47 GMT -06:00
Page 1 of 3 MSE 4793 Homework 4 MSE 4793 Homework 4.pdf
https://www.cliffsnotes.com//study-notes/23828308
