EMA lecture 1 Flashcards
uploading terms from notes (16 cards)
What are polymers?
Polymers are long macromolecules with some repeating units.
What are the differences between natural, semi-synthetic, and synthetic polymers?
Natural polymers are found in nature (e.g., cellulose), semi-synthetic polymers are modified natural polymers (e.g., nitrocellulose), and synthetic polymers are manufactured (e.g., polyethylene).
Why are polymers widely used in manufacturing and production?
Because they are lightweight, durable, cheap to make, and easy to process.
What was created in 1870?
Nitrocellulose.
What was created in 1907?
Bakelite.
What notable polymers were created in the 1920-30s?
Nylon (polyamide), PVC, polyester, acrylic, polystyrene, polyurethane.
What notable polymers were made in the 1940-50s?
Polyethylene, Teflon, epoxies, ABS, PET, and PC.
What is the significance of Bakelite in the history of synthetic polymers?
It was one of the first synthetic polymers, marking a significant milestone in polymer development.
What distinguishes thermoplastics from thermosets?
Thermoplastics can be reformed when heated; thermosets cannot be reheated and reformed.
What is the effect of cross-linking density on polymers?
It determines whether the polymer is an elastomer (low density) or a rigid thermoset (high density).
What is the glass transition temperature (Tg)?
The temperature at which polymer chains unlock and start to move.
What happens to a polymer below and above Tg?
Below Tg, it remains rigid and glassy; above Tg, it starts to flow.
How do amorphous and semi-crystalline polymers differ?
Amorphous polymers have random disordered arrangements, while semi-crystalline polymers have both ordered and disordered regions.
What are some advantages of polymers in industrial applications?
Polymers are versatile and can be mixed with different resins and chemicals.
How does the ability of polymers to flow or dissolve affect processing methods?
Polymers that flow are suited for injection molding; those that dissolve are better for specific applications.
What factors influence whether a polymer behaves as an elastomer, thermoset, or thermoplastic?
Cross-link density and the ability to flow and dissolve in solvents.
