Intro Flashcards
What are the 3 main polymer classes?
Thermoplastic - linear or branched that flow when heated
Thermoset - cross linked networks that cannot flow - stronger but brittle
Elastomer (rubber) - lightly cross linked with elastic properties
What is a homo and co polymer?
Homopolymer - repeating same monomers
Copolymer - two or more types of repeating monomers (can be random or in blocks)
What does polymer architecture refer to?
The type of network or linking/branching in a polymer
What is an oligomer?
Small chain lengths - just a few monomer units - likely liquid at room temp like oil
What’s the difference between a resin and a plastic?
Resin - polymer unshaped or moulded
Plastic - polymer after shaping or moulding
What is degree of polymerisation?
Average length of a linear polymer
What are the key differences between an organic vs a polymer molecule?
Polymers have a much higher molecular weight, are large molecules, have a higher boiling point, are non-reactive, and have repeating units.
What’s the difference between saturated and unsaturated hydrocarbons?
Saturated contain only carbon - carbon single bonds
Unsaturated contain carbon - carbon double or triple bonds (so more hydrogens could be added
What graph can we use to estimate cooling rate of a polymer being moulded?
Fourier graph - use temps to find horizontal line, then go down to get Fo which you can use to calculate time.
What are the two types of additive and some examples?
Modifying: carbon black (reinforcing), dyes (colouring), plasticisers (flexibility), blowing agents (to produce foam)
Protective: antioxidants, heat stabilisers, UV stabilisers, processing agents
What’s the difference between distribution and dispersion?
Distribution - ingredients are stirred together throughout mixture
Dispersion - ingredients are spread relative to each other but not throughout mixture
What factors affect shrinkage?
Nature of polymer
Crystallinity
Pressure
Wall temp
Addition of fillers
What are sprues?
Remains of the nozzle that form on a moulded item
What are some key process considerations for polymers?
Cooling
Sprues
Draft Angle
