How does polyester change at high temperatures?

Polyester has good thermoplastic properties and produces different changes at different temperatures. The change in the heat of the polyester is between the amorphous and crystalline polymer compounds. It is above the glass transition temperature, and only the segments with small interaction between the molecular chains in the amorphous region can move. The molecular segments with large interaction between the molecular chains are still difficult to move, and the molecular chains in the crystallization region cannot of course move. Therefore, the fiber only appears to be relatively flexible, but it does not necessarily have the same elasticity as the high elastic state.

When the heating is continued to 230-240 ° C, the softening point of the polyester is reached, the molecular chain movement of the amorphous polyester region is intensified, and the forces of the intermolecular interaction are disassembled. At this time, the viscous flow state is similar, and the chain in the crystallization zone The segment has not been dismantled, so the fiber only softens, not melts, but at this time, the use value of the fiber has been lost, so it is not allowed to exceed this temperature in the printing and dyeing process.

The transfer printing of polyester is achieved by the movement of heated molecular chains in the amorphous region. However, the temperature must be strictly controlled. If it exceeds the allowable range, the hand of the fabric becomes rough; when the polyester is subjected to a high temperature of 258-263 ° C, the molecular segment in the polyester crystal region starts to move, and the fiber melts. This temperature is polyester. The melting point.

When the polyester is heat-set, the microstructure of the fiber changes differently due to the different heat received. When the setting temperature is 170-180 °C, the absorption capacity of polyester for disperse dye in the dyeing process is very low. When it exceeds 180 °C, the absorption rate of polyester to dye is proportional to the increase of temperature, which is related to the crystallization property of polyester. Relatedly, since the crystallization speed of the polyester is fast at 170-180 ° C, the dye is less dyed due to the formation of more crystals, and the temperature is increased, which may cause a decrease in the degree of orientation of the macromolecule, so the absorption dye is increased.

Polyester is hydrolyzed under the action of high temperature steam for a long time, and the strength and dyeing properties of the fiber are reduced, but it can withstand a high temperature of 140 ° C in water and water-based dye bath.