Study On Recycled Polypropylene Thermal Aging Properties

Polypropylene(PP)is one of five general-purpose material,due to the presence of the tertiary carbon atoms in the molecular chain,so that PP macromolecules susceptible to degradation by heat,oxygen,etc.In the molding process,the PP will go through many heated and subjected to intense mechanical shearing,these factors will accelerate the heat oxygen aging,resulting in decreased performance of the product until it can not be used.Besides,PP material will absorption of oxygen in the air and oxidative degradation in storage.So the study of thermal aging stability and guidance related to PP application has a positive meaning.Different antioxidants and PP were melt-mixed by a single-screw extruder and through multiple extrusion and oven aging two ways by mechanical properties,melt flow index(MFI),a yellow index analysis(YI),differential calorimeter(DSC),and thermal gravimetric analysis(TG)and so on,comprehensive evaluation of the long-term stability and the stability of the PP with different antioxidant systems.The processing stability was studied by multi-extruded PP with different antioxidants.The results showed that antioxidants to improve processing stability of polypropylene achieved good results,with the addition of antioxidants 1010/618 and 1035/168 improving effect is better than others,after extruded several times its mechanical properties and a melt index remained relatively high rates.The tensile strength were maintained at 35.48 MPa and35.16 MPa,melt index of the rate of increase was 0.99 g / 10 min and 1.02 g / 10 min,both basically no difference.Differential calorimeter(DSC)analysis results showed that with the antioxidants 1010/618 added,the melting peak temperature decreased from 174.19 ℃ to167.28 ℃,crystallization peak temperature decreased from 118.57 ℃ to 113.57 ℃ after extruded several times.Thermal gravimetric analysis(TGA)showed that under a nitrogen atmosphere with the antioxidants 1010/618 and 1035/168 were added,the initial decomposition temperature and stop the degradation temperature relative to pure polypropylene are improved.The long-term stability was studied by aging PP with different antioxidants.The resultsshowed that antioxidant to improve heat aging properties of polypropylene achieved good results,with the addition of antioxidants 1010/618 improving effect is better than others,after400 h thermal aging treatment its tensile strength was maintained at 35.68 MPa,melt index of the rate of increase was 0.65 g / 10 min to 1.28 g / 10 min.Differential calorimeter(DSC)analysis results showed that with the antioxidants 1010/618 added,after 400 h thermal aging treatment the melting point and crystallinity of the best are 170.56 ℃ and 114.98 ℃.Thermal gravimetric analysis(TGA)showed that under a nitrogen atmosphere with the antioxidants 1010\618 were added,the initial decomposition temperature and stop the degradation temperature are improved.