thermo Flashcards
(19 cards)
3 states of amorphous
- glassy state
- rubber state
- liquid state
what is glass transition
Glass transition is the transition in amorphous materials from a hard and relatively brittle state into a molten or rubber-like state
what is denature
Denaturation is the structural change of biopolymers that involves the disruption and possible destruction of both the secondary and tertiary structures
what is decomposition
Decomposition is the process by which material is broken down into simpler forms of matter.
what is TGA
Sample weight change is measured as a function of temp,
3 process where mass does not change
melting, glass transition, denature
3 processes where mass is loss
boiling, sublimation, decomposition
1 process where mass will increase
oxidation
what is DTG
Used to simplify reading of weight vs temperature thermogram peak
4 applications of TG
water content of hydrates, decomposition kinetics of material, thermal stability of matrerials, estimated lifetime of a product
bellow glass transiiton and above and is it teh same for all
Below Glass transition temperature (Tg) polymers are hard and glassy
Above Glass transition temperature (Tg) polymers are soft and elastic
Glass transition temperature (Tg) of different polymers is different
plasticisation
Some small molecular weight additives can shift (e.g., decrease) glass transition temperature
4 practical aspects , 2 about tray, 1 weight, sample application
Small amounts of sample
Spread thinly over sample pan to aid heat transfer
Keep the sample pans clean
Normally made of aluminium so no react
what does DSC do
The DSC instrument keeps the sample and the inert reference material at the same temperature, whilst the sample is heated or cooled
The energy required to maintain T = 0 is measured & therefore gives calorimetric measurements directly
hwo to use DMS for crystalinity
sample value/pure amorphus value X 100
6 things DSC can identify
Melting point
Enthalpy
Glass transition temperature
Polymorphic forms
Purity
Miscibility
how to work out purity
can tell purify by comparing to records as unsure will have diff results
how to see decomposition, glass temp, oxidation, melting
melt is big endo and no mass change
glass is a small endo and no mass change
oxidations is exo and mass increase
decomposition is big endo and mass loss
how to tell if 2 polymers can mix
if combo should have 1 glass transition but if 2 then they do not mix
