Study On Polycarbonate Injection Molding Process And Thermo-oxidative Stability

In this paper, plastic injection molding machines and hot air aging oven were usedto study the performance of Polycarbonate used as food and packaging materials, therelationship between structural change and thermal-oxidative aging injection processand the thermal stability of PC.The mechanical property test of injection molding PC samples with differentinjection temperature was conducted. The results proved that at290°C, the flexuralproperty, tensile property and fracture property of samples were close to the highest.As a result,290°C temperature should be the most suitable for the injection molding ofPC. Analysis for the following reasons: long PC repeating units and the benzene ringstructure limit the flexibility of macromolecules, resulting in the PC and the meltingtemperature of the glass transition temperature are high. The polycarbonate in themolten state is close to a Newtonian fluid, the temperature dependence of meltviscosity is small, a suitable elevated temperature is effective to regulate the melt flowproperties conducive to forming.The mechanical property test of PC samples with different thermo-oxidativeaging degree. The results proved that in the initial stage of aging, the flexural strength,tensile strength, breaking strength of samples increased rapidly with the incrementaging time. After48h, the rising rate got slower and stable, but PC samples stillshowed strength and toughness. On the other hand, in the initial stage of aging,notched impact strength, breaking elongation of PC samples decreased with theincrement aging time. Samples showed high notch sensitivity. After48h, the rising rategot slower and stable. In a word, strong and tough PC changed into hard and fragile. TG tests under a nitrogen atmosphere show that: in the early aging, thetemperature of initial spot of the PC, temperature of biggest loss rate, temperature ofweightlessness half decrease with aging time after show an upward trend firstly. Underan air atmosphere, TG tests show that: for the same stage of degradation, thermaldegradation of PC activation of different aging time decrease firstly and then increasewith aging time decrease. This reflects that PC rise firstly after lower thermal stability,and finally stabilize in the thermal oxidative aging process.