| A on-line melt strength meter was designed and manufactured to measure the melt strength of the extruded product during the extrusion reaction to prepare high melt strength polypropylene.The use parameters of the melt strength meter were determined by a large number of detailed tests.The melt flow rate method and the fusing method used in the literature were tested and compared with the melt strength meter method.It was found that change trend of the melt force value measured by a on-line melt strength meter was consistent with the results measured by two kinds of measurement methods.Meanwhile,a large range of measured melt force value,the data is stable and reliable,the instrument is sensitive,the relative error is small,and we can directly read the results are the characteristics of the method,while the results of the traditional melt flow rate meter and the fusing method have the characteristics that the original measurement values are very small,the relative error is large and the measurement time is long.In order to cooperate with the extrusion reaction during the experiment to discharge volatile toxic and harmful gases,we designed and manufactured a portable exhaust fan,which meets the requirements through the commissioning and use of verification.The experiment of preparing high melt strength polypropylene by extrusion reaction was studied by using ordinary single screw extruder and reaction extruder respectively.The melt strength of extruded reaction product was measured with self-designed on-line melt strength meter.Meanwhile the extruded products were measured with the conventional melt flow rate indirect measurement method and the fusing method.Moreover,the experimental results were compared.Various extrusion reaction initiators such as dicumyl peroxide(DCP),dibenzoyl peroxide(BPO),azobisisobutyronitrile(AIBN),di-t-butyl peroxide(DTBP)and 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane(abbreviated as double 25)and two possible microcrosslinking auxiliaries divinylbenzene(DVB)and Pentaerythritol triacrylate(PETA)were used to prepare the experimental product.Through a large number of experimental studies found that DCP was the best initiator,DVB was the best micro-crosslinking agent of the extrusion reaction and the closed exhaust port was better than the open the exhaust port when we use the extrusion reaction.While the use of single-screw extruder was better than the reaction extruder.The optimum formulation was as follows: the dosage of DCP was 0.04% and the dosage of DVB was 0.5%.The optimum conditions were as follows: the processing temperature of the extruder is 160,180,190,190,180?,screw speed is 50 rpm,traction velocity is 5.8cm/s.Under these conditions,the melt strength of high melt strength polypropylene reached 10.5Kpa.s,and melt force value reached 180 g,these data were more than 5 times the raw material PP.The characterization of the results showd that the preparation product contains a small amount of gel produced by long chain branched crosslinking reaction,but it will not affect the processing performance of the product.The infrared spectrum analysis showd that the product did not change in nature with the raw material and DSC showed that the crystallinity and crystallization temperature of the product are improved.The Vicat softening point indicated that the heat-resistant temperature of the product was improved.The wide-angle X-ray diffraction analysis showed that the ?-crystalline PP was produced in the product.The mechanical properties,the tensile strength and impact strength of the product were higher than the raw material. |
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