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How to Measure Glass Transition Temperature
This melting point is generally above that of the upper range of amorphous thermoplastics. These do not soften as the temperature rises, but rather have a defined and narrow melting point. PC, GPPS, PMMA, PVC, ABS.Ĭrystalline or Semi-crystalline polymers have a highly ordered molecular structure. Amorphous materials are more sensitive to stress failure due to the presence of hydrocarbons. Instead, amorphous material softens gradually as temperature rises. The structure of a polymer is defined in terms of crystallinity.Īmorphous polymers have a random molecular structure that does not have a sharp melting point. Polymers (plastics, elastomers or rubber) are made up of long chains of molecules and may be amorphous or crystalline. » Glass Transition Temperature Values Table of Several PlasticsĪmorphous Polymers and Crystalline Polymers » Key difference Between Tg and Melting Temperature » How to Determine Glass Transition Temperature » What are Amorphous and Crystalline Polymers Related Read: How to Get Started with Polymer CharacterizationĬheck out more on Glass Transition Temperature: Also, it is an important tool used to modify physical properties of polymer molecules.įurther, improvement in handling characters, solubility and reproducibility in dissolution of solids can be achieved by increasing the Tg of solids. Identifying the Tg of polymers is often used for quality control and research and development. They are soft and flexible in nature their Tgs are less than room temperature. Some polymers are used above their Tg (in rubbery state), for example, rubber elastomers like polyisoprene, polyisobutylene. Their Tgs are higher than room temperature. Some polymers are used below their Tg (in glassy state) like polystyrene, poly(methyl methacrylate) etc., which are hard and brittle. 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.Īt Tg, changes in hardness, volume, percent elongation to break and Young’s modulus of solids are mainly seen. The value of Tg depends on the mobility of the polymer chain, and for most synthetic polymers lies between 170 K to 500 K. Crystalline polymers exhibit a Tm (melt temperature) and typically a Tg since there is usually an amorphous portion as well (“semi”-crystalline).This temperature (measured in ☌ or ☏) depends on the chemical structure of the polymer and can therefore be used to identify polymers. It is also defined as a temperature at which amorphous polymer takes on characteristic glassy-state properties like brittleness, stiffness and rigidity (upon cooling). 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.
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