HS2004_2339 Week 3 Asyn_Plasticisers and Tg (copy) (copy) Flashcards
What are plasticisers used for
They are everywhere! Used within a lot of common polymers, because if we didn’t a lot of polymers would be too stiff, have less longevity.
What are plasticisers
essentially a kind of solvent for polymers. large molecules. don’t dissolve into liquid, but when a polymer has strong side chains that make it stiff, a plasticiser is added, in order to get between the chains and disrupt some of the secondary bonding between chains.
- polymer becomes more flexible. increases in volume, and there is more specific volume, more space. it becomes easier for oxygen and water to access this space. Thalates are a common plasterciser.
What is an internal plasticiser
- When a co- polymer is added which has a plasticising effect. makes it more flexible eg has a long side chain or a ring.
- advantages, as the co- polymer is part of the structure, the polymer retains its qualities
- an interference with packing, but unlikely to migrate out of the material, unlike other plasticisers.
Disadvantage of added plasticisers
- although they have low volatility, they can migrate to the surface of the material and evaporate. this changes the properties of the plastic.
Glass Transition temperature is a s____ o____ transition state, because…..
Tg- point at which a polymer, according to temperate, absorbs energy, begins to vibrate as temp increases, and the polymer softens
- upon cooling, the polymer returns to original state.
- second order transition, as it doesn’t melt, and doesn’t release energy when it returns to its original state.
- polymer structure influences Tg. Highly crystalline polymers, have a high Tg and will often decompose before they soften.
Polymer Properties above and below Tg
How Tg is influenced by polymer chemistry
How the length of side chains on polymers impact Tg, with diagram
- Longer side chains, lower Tg
How Tg influences polymers in product design and conservation decision making
Paraloid B-72, how dust settles on surface, effect of continuous warm temperatures
Particle retention on the surface of paraloid B-72 at room temp vs heated
