Interpretation of several temperatures in the plastics industry

March 17, 2023

Interpretation of several temperatures in the plastics industry

plastic-machining-process

(1) Glass transition temperature Tg: refers to the transition temperature of an amorphous polymer (including the non-crystalline part of a crystalline polymer) from a glass state to a high elastic state or from the latter to the former. It is the lowest temperature at which the macromolecular chain segments of amorphous polymers can move freely, and it is also the upper limit of the working temperature of the product.

(2) Melting temperature Tm: For crystalline polymers, it refers to the temperature at which the three-dimensional long-range ordered state of the macromolecular chain structure transforms into a disordered viscous fluid state, also known as the melting point. It is the lower limit of the molding processing temperature of the crystalline polymer.

(3) Flow temperature Tf: refers to the temperature at which the amorphous polymer changes from a highly elastic state to a viscous fluid state. It is the lower limit of the processing temperature of amorphous plastics.

(4) No-flow temperature: the highest temperature at which no flow occurs under a certain pressure. It is to add a certain amount of plastic into the barrel at the upper end of the die of the capillary rheometer, heat it to a certain temperature, and then apply a constant pressure of 50MPA after constant temperature for 10 minutes. The high difficulty is 10 degrees. After holding the heat for 10 minutes, apply the same constant pressure. Continue until the melt flows out of the die. Subtract 10 degrees from this temperature to get the non-flow temperature of the material.

(5) Decomposition temperature Td: refers to the polymer in a viscous state. When the temperature is further increased, the degradation of the molecular chain will be intensified, and the temperature at which the polymer molecular chain is significantly degraded is the decomposition temperature.

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