On-line Testing Of Residence Time Distribution Of Single Screw Extruder

During the single-screw extrusion process,the time to leave the extruder is different when polymer entered into extruder at the same time due to the inverse mixing of fluid cells,uneven velocity distribution,improper extruder design and other factors,which forms residence time distribution(RTD).RTD is an important parameter in single-screw extruder,which can indicate the heat history of the material during extrusion.It is also often used to characterize macroscopic mixing of the screw extruder.Based on the principle of on-line fluorescence detection,a set of on-line fluorescence detector is designed by using the single-screw extrusion platform of a torque rheometer to study the residence time distribution of a single screw extruder.P(St-co-AMMA)is synthesized with St and AMMA as solute and BPO as initiator to be used as a macromolecular tracer to characterize the residence time distribution of single screw extruders.The distribution of residence time of PS in single screw extruder is studied.Effects of tracer content and screw rotation speed on the residence time distribution of PS in single screw extrusion were studied,choosing EN as the tracer.On the basis of characterizing the residence time distribution of PS,the residence time distribution of PET during single-screw extrusion and the effect of residence time in single screw on intrinsic viscosity,thermal stability and Rheological properties of PET is studied.The results show that:(1)The residence time distribution of PS in single screw extruder is obtained successfully by the on-line fluorescence detection.The results of the repetitive test indicate that the established Fluorescence on-line detection device has good stability.The amount of tracer has no effect on the residence time distribution of PS in the single-screw extruder,which indicates the amount of tracer has no effect on the axial mixing capacity of single screw extruder.And the residence time distribution of PS becomes narrower as the screw speed decreases,which shows that the macro-mixing capacity of a single screw extruder decreases with the increasing screw speed.(2)The spectrum of FT-IR and ~1H-NMR show that the obtained product is the target product P(St-co-AMMA).P(St-co-AMMA)can be used as a macromolecular tracer to characterize the PS residence time distribution,and the amount of P(St-co-AMMA)has no effect on the residence time distribution of PS.And the residence time distribution of PS decreases as screw speed increases.(3)During the single screw extrusion process,the amount and type of tracer do not affect the residence time distribution of PET.It shows that the type and amount of tracer has no effect on the axial mixing capacity of single screw extruder.During the process of single screw extrusion,the rotational speed of the screw has a significant effect on the residence time distribution of PET.The faster the screw speed and the narrower the residence time distribution,indicating that increasing the screw speed will reduce the axial mixing capacity of the single screw extruder.As the residence time of PET increases the intrinsic viscosity and decomposition temperature of PET would decrease.And the storage modulus and loss modulus and complex viscosity of PET also decrease.