IntermediateTopic 38 of 100Materials & Chemical
Polymers
Long-chain molecules classified as thermoplastics, thermosets and elastomers.
In depth
Polymers are long chains of repeating units (mers) with covalent backbones and weak secondary bonds. Properties depend on molecular weight, chain structure, crystallinity and additives. Light weight, corrosion resistance, insulation and ease of processing make them ubiquitous; weak to heat and creep.
Key points
- Degree of polymerisation
- Amorphous vs semi-crystalline
- Plasticisers and fillers
ExamplePE, PP, PVC, PET and nylon are common commodity and engineering polymers.
Polymers are light, easy to shape and cheap, which makes them the most widely used material class in consumer and many engineering products.
What is Polymers?
Long-chain molecules classified as thermoplastics, thermosets and elastomers.
Why is it important to understand polymers?
Polymers are light, easy to shape and cheap, which makes them the most widely used material class in consumer and many engineering products.
What distinguishes the three main polymer types?
Thermoplastics soften on heating, thermosets harden permanently through cross-linking, and elastomers stretch elastically with cross-links that allow large strain.
Why are polymers weaker than metals?
Their molecular bonds are weaker and their stiffness depends strongly on temperature and time, so they usually have lower strength and modulus.
How is Polymers used in practice?
Typical applications include choosing a polycarbonate for a safety shield, using polyethylene for water pipes and designing a nylon gear for a quiet drive.
What should I learn before Polymers?
Study "Advanced ceramics" first (topic 37 of 100 in Materials & Chemical). It covers the groundwork this topic builds on.
What are the key points of Polymers?
Degree of polymerisation. Amorphous vs semi-crystalline. Plasticisers and fillers.
Can you give an example of Polymers?
PE, PP, PVC, PET and nylon are common commodity and engineering polymers.
What comes after Polymers?
The next topic is "Polymerisation", which builds directly on this one.
How difficult is Polymers?
It is classed as Intermediate in Materials & Chemical (topic 38 of 100). It is an intermediate topic. Work through the beginner topics in Materials & Chemical first.