Refer to the amount on the appropriate acute the calefaction accommodation as a action of temperature. In this context, Tg is the temperature agnate to point A on the curve. The beeline sections beneath and aloft Tg are black green. Tg is the temperature at the circle of the red corruption lines.12
Different operational definitions of the bottle alteration temperature Tg are in use, and several of them are accustomed as accustomed accurate standards. Nevertheless, all definitions are arbitrary, and all crop altered numeric results: at best, ethics of Tg for a accustomed actuality accede aural a few kelvins. One analogue refers to the viscosity, acclimation Tg at a amount of 1013 address (or 1012 Pa·s). As apparent experimentally, this amount is abutting to the annealing point of abounding glasses.13
In adverse to viscosity, the thermal expansion, calefaction capacity, and abounding added backdrop of asleep glasses appearance a almost abrupt change at the bottle alteration temperature. Any such footfall or coil can be acclimated to ascertain Tg. To accomplish this analogue reproducible, the cooling or heating amount have to be specified.
The a lot of frequently acclimated analogue of Tg uses the activity absolution on heating in cogwheel scanning calorimetry (DSC, see figure). Typically, the sample is aboriginal cooled with 10 K/min and again acrimonious with that aforementioned speed.
Yet addition analogue of Tg uses the coil in dilatometry. Here, heating ante of 3-5 K/min are common. Summarized beneath are Tg ethics appropriate of assertive classes of materials.
edit Polymers
Material Tg (°C)
Tyre elastic −7014
Polypropylene (atactic) −2015
Polypropylene (isotactic) 015
Poly-3-hydroxybutyrate (PHB) 1515
Poly(vinyl acetate) (PVAc) 3015
Polyethylene terephthalate (PET) 7015
Poly(vinyl chloride) (PVC) 8015
Poly(vinyl alcohol) (PVA) 8515
Polystyrene 9515
Poly(methylmethacrylate) (atactic) 10515
Poly(carbonate) 14515
Polynorbornene 21515
Nylon-6 Nylon has a bottle alteration temperature of 47 Celsius16. Whereas Polyethene has a bottle alteration ambit of -130 to -80 17 It have to be kept in apperception that the aloft are alone beggarly values, as the bottle alteration temperature depends on the cooling rate, atomic weight administration and could be afflicted by additives. Note aswell that for a semi-crystalline material, such as polyethene that is 60-80% apparent at allowance temperature, the quoted bottle alteration refers to what happens to the baggy allotment of the actual aloft cooling.
edit Silicates and added covalent arrangement glasses
Different operational definitions of the bottle alteration temperature Tg are in use, and several of them are accustomed as accustomed accurate standards. Nevertheless, all definitions are arbitrary, and all crop altered numeric results: at best, ethics of Tg for a accustomed actuality accede aural a few kelvins. One analogue refers to the viscosity, acclimation Tg at a amount of 1013 address (or 1012 Pa·s). As apparent experimentally, this amount is abutting to the annealing point of abounding glasses.13
In adverse to viscosity, the thermal expansion, calefaction capacity, and abounding added backdrop of asleep glasses appearance a almost abrupt change at the bottle alteration temperature. Any such footfall or coil can be acclimated to ascertain Tg. To accomplish this analogue reproducible, the cooling or heating amount have to be specified.
The a lot of frequently acclimated analogue of Tg uses the activity absolution on heating in cogwheel scanning calorimetry (DSC, see figure). Typically, the sample is aboriginal cooled with 10 K/min and again acrimonious with that aforementioned speed.
Yet addition analogue of Tg uses the coil in dilatometry. Here, heating ante of 3-5 K/min are common. Summarized beneath are Tg ethics appropriate of assertive classes of materials.
edit Polymers
Material Tg (°C)
Tyre elastic −7014
Polypropylene (atactic) −2015
Polypropylene (isotactic) 015
Poly-3-hydroxybutyrate (PHB) 1515
Poly(vinyl acetate) (PVAc) 3015
Polyethylene terephthalate (PET) 7015
Poly(vinyl chloride) (PVC) 8015
Poly(vinyl alcohol) (PVA) 8515
Polystyrene 9515
Poly(methylmethacrylate) (atactic) 10515
Poly(carbonate) 14515
Polynorbornene 21515
Nylon-6 Nylon has a bottle alteration temperature of 47 Celsius16. Whereas Polyethene has a bottle alteration ambit of -130 to -80 17 It have to be kept in apperception that the aloft are alone beggarly values, as the bottle alteration temperature depends on the cooling rate, atomic weight administration and could be afflicted by additives. Note aswell that for a semi-crystalline material, such as polyethene that is 60-80% apparent at allowance temperature, the quoted bottle alteration refers to what happens to the baggy allotment of the actual aloft cooling.
edit Silicates and added covalent arrangement glasses
No comments:
Post a Comment