What type of polymers have a glass transition?
Pure crystalline polymers do not have a glass transition temperature because the glass transition temperature is only applicable to amorphous polymers. Pure amorphous polymers do not have a melting temperature; they only have a glass transition temperature.
Does polyethylene have a glass transition temperature?
All polymers have a temperature by which the configuration changes from a rigid or glassy state to a rubbery or flexible state. The temperature at which it occurs is called the “glass transition” temperature. For instance, the glass transition temperature, or Tg, of low-density polyethylene is − 100°C.
Why propylene has higher glass transition temperature than polyethylene?
Bulky group attached to polymer backbone also reduces flexibility of chain backbone therefore polypropylene has higher Tg than polyethylene.
What is the glass transition temperature for a thermoplastic polymer?
between 170 K to 500 K.
The value of Tg depends on the mobility of the polymer chain, and for most synthetic polymers lies between 170 K to 500 K. The transition from the glass to the rubber-like state is an important feature of polymer behavior, marking a region of dramatic changes in the physical properties, such as hardness and elasticity.
Why do polymers undergo glass transition temperature?
Most polymers, on the other hand, do not behave the same and have a somewhat less defined change from solid to liquid. These “amorphous” polymers change from a more crystalline or glassy structure to a typically softer or rubbery structure at a temperature defined as the glass transition temperature.
Does plasticizer increase Tg?
Tg is the temperature at which the polymer chains begin to move, so, by addition of plasticizer the movement will occur at lower temperatures. when adding plasticizer to PVC, the crystalline decreased, so the Tg decrease.
What is the glass transition temperature of LDPE?
-125 oC
LDPE Properties:
| LDPE Physical Properties: | Value: |
|---|---|
| Max. Continued Use Temperature: | 65 oC (149 oF) |
| Melting Point: | 110 oC (230 oF) |
| Glass Transition Temperature: | -125 oC (-193 oF) |
| Density: | 0.910 – 0.940 g/cm3 |
What is the significance of glass transition temperature?
Glass transition temperature Tg is an important parameter used for identification of plastics. The Tg value is the temperature at which amorphous polymers change from hard to soft. The concentration of crystalline regions in amorphous (semicrystalline) polymers affects the rigidity of the polymer.
How can you reduce the Tg of a polymer?
if you increase the free space between the chains molecules by adding a bulky Groups during polymerization process or increase the chain lingth of the side Groups or modifying the crystalline nature may reduces the Tg.
What material type has a glass transition temperature?
amorphous materials
Glass transition temperature is represented by Tg and is a property of the amorphous materials or the amorphous portion of a semicrystalline materials.
What is the glass transition temperature of polymers?
When an amorphous polymer is heated, the temperature at which the polymer structure turns “viscous liquid or rubbery” is called the Glass Transition Temperature, Tg. The value of Tg depends on the mobility of the polymer chain, and for most synthetic polymers lies between 170 K to 500 K.
What is the effect of TG on the properties of polymers?
At Tg, changes in hardness, volume, percent elongation to break and Young’s modulus of solids are mainly seen. Some polymers are used below their Tg (in glassy state) like polystyrene, poly (methyl methacrylate) etc., which are hard and brittle.
What is the transition from glass to rubber-like state?
The transition from the glass to the rubber-like state is an important feature of polymer behavior, marking a region of dramatic changes in the physical properties, such as hardness and elasticity.
What is the glassy state of a polymer?
It is also defined as a temperature at which amorphous polymer takes on characteristic glassy-state properties like brittleness, stiffness and rigidity (upon cooling). This temperature (measured in °C or °F) depends on the chemical structure of the polymer and can therefore be used to identify polymers.