Materials scienceLesson 3 of 5 in the course Polymers

Thermoset Polymers: Curing, Properties, Composites, and Processing

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

This lesson introduces thermosetting polymers and explains how curing changes a workable resin into a permanently crosslinked material. Understanding the curing process helps explain why thermosets behave differently from thermoplastics.

A thermosetting polymer, or thermoset, begins as a soft solid or viscous liquid called a prepolymer or resin. Before curing, it is often malleable or liquid, so it can be placed in a mold, applied as an adhesive, or otherwise shaped.

All flashcards

What is a thermoset?
A polymer formed when a workable resin or prepolymer is irreversibly hardened by curing into a crosslinked network.
What does curing do to polymer chains?
Curing creates covalent connections called crosslinks between chains, producing an extensive three-dimensional network.
What are a hardener and a catalyst used for?
They help promote or enable curing reactions. A hardener commonly reacts with the resin, while a catalyst helps a reaction proceed.
How do epoxy resins commonly form a network?
They can polymerise with catalysts or react with multifunctional curing agents. Continued reaction forms larger, branched molecules and crosslinks.
How do thermosets differ from thermoplastics after shaping?
A conventional cured thermoset cannot be melted and reshaped because of its crosslinked network; thermoplastics can commonly be softened or melted for shaping.

Quiz questions

  1. What is a thermosetting polymer commonly called?Answer: A thermoset.
  2. What structural change occurs as a thermosetting resin cures?Answer: Covalent crosslinks form between chains, creating a three-dimensional network.
  3. Why can a conventional cured thermoset not be reshaped by melting?Answer: Its crosslinked network prevents it from flowing like a melt.
  4. Which statement about heat during thermoset curing is correct?Answer: Curing may use external heat, and the reaction can also generate heat.
  5. Which reactants form polyurethanes in thermosetting resin systems?Answer: Isocyanates and polyols.

Based on the Wikipedia article Thermosetting polymer, licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.

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