Glass transition temperature, heat distortion temperature, and Vicat softening point of polymers
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Is there any relationship between the glass transition temperature, heat distortion temperature and Vicat softening point of polymers? ? Which one is bigger and which one is smaller? What's the use of all these temperatures! ? 50322392
The glass flower temperature, microcardinal softening point, and heat distortion temperature increase in sequence. The glass flower temperature refers to the transition temperature of amorphous polymers (including the amorphous part of crystalline polymers) from the glassy state to the highly elastic state or from the latter to the former. It is the lowest temperature at which amorphous polymer macromolecular segments can move freely. The softening point refers to the temperature when a sample of polymers such as engineering plastics and general plastics is pressed into a depth of 1mm by a 1mm2 indenter in a liquid heat transfer medium under a certain load and a certain constant rate of temperature rise. It is suitable for controlling the quality of polymers and as an indicator for identifying the thermal properties of new varieties. It can compare the average molecular weight of resins. Through comparative analysis of the softening point and reactive functional group content of similar resins, the molecular weight distribution of the resin can also be roughly judged. It does not represent the service temperature of the material. Thermal deformation temperature refers to the corresponding temperature when a certain load is applied to a polymer material or polymer and the temperature rises at a certain speed when the specified deformation is reached. It is a measure of the heat resistance of polymer or polymer materials. Generally speaking, materials with high glass flower temperatures have high softening points and heat distortion temperatures.
Generally speaking, Tg is the maximum service temperature of amorphous polymers or low crystalline polymers, HDT is the maximum service temperature of crystalline polymers, short-term
1# hcbbsqiudr The glass transition temperature is only found in amorphous polymers but not in crystalline polymers. The glass transition temperature is greater than the Vicat heat resistance temperature, and the Vicat heat resistance temperature is greater than the heat distortion temperature.
Why is Zhengzhangfa different from what QXZ-1966 wrote? Which one is bigger and which one is smaller! ! ! I see that the Tg of linear low-density polyethylene is -78 degrees, while the heat distortion temperature is around 50 degrees. The Vicat softening point has not been reached. Do all polymers comply with the same size rules? ! ?
A friend upstairs needs to understand the concept of glass transition temperature. Whether it is an amorphous polymer or a crystalline polymer, they all have a glass transition temperature. QXZ-1966's answer is relatively professional. However, the glass transition temperature is mostly used in academic circles and is generally not used in actual production. Moreover, the glass transition temperature is not the thermodynamic transition temperature. The glass transition temperature obtained by the same sample and different testing methods, even the same testing method and different testing conditions (such as DMA using different frequencies), is very different.
What you said above is correct. Whether it is an amorphous polymer or a crystalline polymer, they all have a glass transition temperature.
Whether it is an amorphous polymer or a crystalline polymer, they all have a glass transition temperature. Crystalline polymers usually include two parts: a crystalline region and an amorphous region. Although the molecular motion in the amorphous region is affected by the existence of the crystalline region to varying degrees, it still has the above-mentioned molecular motion mechanism of amorphous polymers, and there are three mechanical states (glassy state, highly elastic state and viscous flow state). However, after the glass transition, only the chain segments in the amorphous region are in motion, and the chain segments in the crystalline region cannot move. Therefore, the highly elastic state of the polymer appears as a tough and hard leather-like state, which is usually called "leather state". This is the characteristic of the glass transition of crystalline polymers. “The polymer in the "leather state" behaves as a tough plastic with a certain degree of flexibility and rigidity. Polyethylene at room temperature is in this state.
Hello, how to measure the heat distortion temperature of plastic? Can it be measured by DSC?