Study On Improving Melt Strength And Intrinsic Viscosity Of PET Bottle Flakes Through Reactive Extrusion

Feasibility to measure the melt strength of PET by using the online melt strength meter was explored in this paper.By improving the extrusion formula and process conditions,the PET bottle flakes were used to prepare high melt strength PET.PE materials,PP materials,PET granules,and PET bottle flakes were used respectively to test the reaction conditiongs of the machine.It is found that the lack of raw materials in the screw will increase the fluctuation amplitude of melt strength of extrudate;vacuumizing the polycondensation zone of reaction extruder will not reduce the melt strength of the extrudate.The melt strength data of the extrudate are repeatable measured in this way.The online melt strength meter designed and manufactured by our lab has obtained National patent.With the improvement of the transmission roller and setting of measurement parameters of the machine,it could be used for the measurement of melt strength of PET.Under the optimal conditions of reactive extruder and online melt strength meter,the changes of melt strength and intrinsic viscosity([?])of PET bottle flakes were studied respectively under various processing conditions.Experiment results show that the melt strength data of extrudate have good repeatability under the same test condition,both the higher water content of PET bottle flakes and higher processing temperature could reduce the melt strength of extrudate,melt strength is remarkably improved by increasing vacuum degree of degassing section,increasing screw speed and adding PMDA into dry PET bottle flakes.The change rules of [?] are the same as melt strength.The optimal formulation and extrusion process conditions are: using dry PET bottle flakes with 0.3 % PMDA,extrusion temperature 240,250,250,250,230 ?,vacuum degree 0.08 MPa,screw speed 50-70 rpm.The melt strength is 7 times more than that of ordinary PET granules.In addition,a laboratory vertical mixer was designed and manufactured according to the experimental demand.Experiments proved that the stirring blades operate steadily with high rotation torque,stepless speed regulation,no abnormal dry tone and no dust flying when mixing materials.It is also convenient to load and unload materials,and easy to clean the surroungding environment.The test prototype is suitable for the initial mixing of different kinds of powder-powder,powder-grain,grain-grain materials with the weight between 100-1000 g.The vertical mixer meets all the design requirements.