Glass transition temperature - the temperature at which a substance that does not crystallize or does not have time to crystallize becomes solid, turning into a glassy state . It is usually designated - T g .
Content
General information
Since the transition is gradual, the specific value of the glass transition temperature depends on the cooling rate and the method for its determination. Usually it is defined as the temperature at which the viscosity of a solid becomes about 100-1000 GPa · s, and the elastic modulus exceeds 1 GPa [1] .
In addition, the glass transition temperature is determined by dilatometric (the dependence of volume on temperature), dielectric (position of the maximum dielectric loss), calorimetric (by the magnitude of thermal effects) and other methods [1] [2] .
Glass transition temperature of polymers
The glass transition temperature of polymers is determined by the chemical composition and structure of their chain and is not a strictly defined quantity, since the transition to the glassy state (see article vitrification ) usually occurs in a rather wide temperature range.
The glass transition temperature is also one of the main characteristics of polymers. Polymers at temperatures above the glass transition temperature are in the plastic state, and at temperatures below the glass transition temperature, they are in the solid and rather fragile state [3] .
For some polymers, the glass transition temperatures are as follows [4] :
| Polymer | T g , ° C |
|---|---|
| Polyethylene (depending on density) | -50 ..- 120 [5] |
| Isotactic Polypropylene | -ten |
| Polyisobutylene | -70 (-73) |
| Atactic polystyrene | 100 (105) |
| Isotactic polystyrene | 100 |
| Polymethyl acrylate | 3 (6) |
| Polyethyl acrylate | -24 |
| Polyzinc acrylate | 300 |
| Polymethylmethacrylate Syndiotactic | 115 (205) |
| Polymethylmethacrylate Isotactic | 45 (55) |
| Polymethylsiloxane | -128 |
| Polymethacrylate | 65 |
| Polyvinyl chloride | 87 (81) |
| Polycarbonate | 150 |
| Polyethylene terephthalate | 69 (70?) |
| Polyamide 6 ( polycaproamide ) | 50 (40) |
| Polyamide 6.6 ( polyhexamethylene adipamide ) | 50 (57) |
Related Literature
- I. I. Tugov, G. I. Kostrykina, Chemistry and Physics of Polymers
- Encyclopedia of Polymers , ed. V.A. Kabanova, vol. 3
Notes
- ↑ 1 2 A. Ya. Malkin - Glass transition temperature
- ↑ MI Ojovan. Viscosity and Glass Transition in Amorphous Oxides, Advances in Condensed Matter Physics, 2008, Article ID 817829, 23 pages (2008). http://www.hindawi.com/journals/acmp/2008/817829/
- ↑ Glass transition temperature
- ↑ L. Nielsen, Mechanical properties of polymers and polymer compositions, translation by P. G. Babaevsky, M. - Ed. Chemistry, 1978
- ↑ POLYETHYLENE - PE (petroten, alkatene, staflen unipole, carlon, HOSTALEN LD, LUPOLEN, MALEN-E)