Extrusion & Post
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Performance Degradation of Biaxially Oriented Polypropylene Film Material Caused by Thermal Degradation
Fenómeno del problema
The product undergoes thermal degradation during processing, with a decrease in molecular weight, a reduction in mechanical properties, and a change in color.
Análisis de la causa
(1) The barrel temperature is too high, exceeding the upper limit of 140-170(stretching)/230-260(extrusion)°C
(2) The material stays in the barrel for too long
(3) The screw speed is too fast, and excessive shear generates frictional heat
(4) Material accumulates at the nozzle or non-return ring and degrades under long-term high temperature
(5) The regrind is processed multiple times, and the molecular weight of the material gradually decreases
Solución
(1) Strictly control the barrel temperature within the range of 140-170(stretching)/230-260(extrusion)°C
(2) Lower the temperature or empty the material in the barrel when shutting down
(3) Appropriately reduce the screw speed
(4) Regularly clean the material accumulated at the nozzle and non-return ring
(5) Control the regrind ratio to not exceed 15-20%
Conclusión clave
Thermal degradation is the main risk in processing; controlling temperature and reducing residence time are the key.
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