Materials scienceLesson 2 of 3 in the course Polymers

Thermoplastics: Properties, Material Grades, and Engineering Applications

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

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Summary

This lesson introduces what makes a plastic a thermoplastic, how heat changes its behavior, and how thermoplastics differ from thermosets. It also explores acrylic, ABS, nylon, and PLA as examples of materials chosen for distinct properties.

A thermoplastic, also called a thermosoftening plastic, is a polymer that becomes pliable or moldable when heated and solidifies again when cooled. Many thermoplastics consist of long, high-molecular-weight chains. Intermolecular forces hold the chains together, but these forces weaken as temperature rises. The chains can then move past one another, making the material viscous and reshapeable.

All flashcards

What is a thermoplastic?
A polymer that softens when heated and hardens when cooled, allowing it to be reshaped under suitable conditions.
How does a thermoset differ from a thermoplastic when reheated?
A cured thermoset has irreversible chemical bonds and typically decomposes rather than melting and flowing again.
What is the glass transition temperature (TgT_g)?
The temperature associated with a substantial change in the behavior of amorphous polymer regions, such as a shift from stiff to more flexible.
What is PMMA commonly used for?
PMMA is a clear, sturdy glass substitute used in products such as aquariums, visors, and lenses.
What is nylon?
A polyamide used in fibers, fabrics, ropes, and mechanical parts such as gears and screws.

Quiz questions

  1. Which polyethylene grade is especially tough and used for bearings, gears, and artificial joints?Answer: Ultra-high-molecular-weight polyethylene (UHMWPE)
  2. Which limitation is associated with polypropylene (PP)?Answer: Ultraviolet exposure can degrade it.
  3. Which property makes PTFE useful for bearings and supports for moving parts?Answer: It has an exceptionally low coefficient of friction among solids.
  4. Why is commercial Noryl made as a blend of PPO and high-impact polystyrene?Answer: The blend improves processability by lowering the processing temperature.
  5. In a thermoplastic composite, what role do reinforcing fibers such as carbon or glass serve?Answer: They contribute strength and stiffness to the composite.

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

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