2339 Week 3 Asyn_Generic polymer nomenclature and properties Flashcards
Properties of materials/ Polymers
What are thermoplastics
- large group of polymers, properties all defined by secondary forces
- no chemical forces between chains, allowing flow
- Despite all being thermoplastics, they all have very different properties (brittleness, strength)
How does the monomer influence the properties of the polymer
- the nature of the monomer and the functional group within it, can influence overall properties, type of bond within the polymer and between polymer chains (ie polar, hydrogen)
- affecting strength between chains
- size of monomer, how many sites of secondary forces influences bond strength between chains
- Sum of all bonds= close packing when bonds are strong, impacting strength. Loose polymer will be more flexible.
Monomer effect (how ring structures can impact stiffness and Tg)
- bulks up, decreases chain movement
- eg PET vs Polycarbonate has two rings, and higher Tg
-copolymerisation combines properties of different monomers eg. spandex
is both elastic and strong
How chain length of polymers effects melting/ boiling point
- increase in molecular weight increases tensile strength
- longer chains tangle together and restrict ability to flow
- ## ability of chains to tangle (entropy)
Diagrams showing increase in Tg and entanglement (entropy) in Alkanes
- PEG, the number refers to the average molecular weight, from a liquid, to sticky waxy polymer, to a solid
Diagram of crystallinity in polymers
How crystallinity effects properties of a polymer
- crystalline has good heat and chemical resistance, harder to separate
- amorphous less dense and more flexible
Describe what tacticity is, there are three groups
How side branching effects polymer density, and polymer properties
- reduces sites for secondary bonding, as reduces packing and lowers density, this lowers strength and melting point
- very long side branches, can be tougher due to entanglement
- bulky ring structures can make it stiffer
Network Polymers, or T______ Polymers, describe structure and bonding, and how this effects properties
- covalent bonds between polymer chains, once formed, cannot be reformed or shaped
- thermosetting
- polymer with lots of crosslinks is rigid, chemically brittle and low impact strength
How crosslinks are formed, V______, or F_____ R______ P________
- through introducing a cross linking agent, eg hardener in epoxy resin
- heat or high energy irridation
Describe the structure and properties of elastomers