Study On The Application Of Different Antioxidant Systems To The Oxidation Resistance Of Polypropylene

The unstable spiral conformation of polypropylene(PP)and the tertiary carbon atom in the structure are more sensitive to oxidation.From processing to use,it is easy to oxidize and degradation of hot oxygen and affect the service life of PP.In order to make PP material durable,it is necessary to treat PP with oxidation resistance.At present,the performance of synthetic antioxidants added in PP is excellent but there are hidden safety risks.With the increase in the use of PP in food-contact objects and medical products,the safety performance of PP materials is required to be higher..High safety,non-toxic natural antioxidants provide a new direction for polymer antioxidants.In this paper,different hindered phenolic antioxidants and natural antioxidants extracted from beverage plants and winery processing byproducts(pomegranate seeds,grape seeds,seabuckthorn seeds)were used as PP antioxidants and were melted with PP.Mix and explore the effects of molding,thermal properties,crystallization properties,OIT,mechanical properties,rheological properties,dispersibility and apparent morphology of PP matrix before and after PP thermal oxygen aging.The main results is as follows:1.Obstructed phenolic antioxidants can significantly increase the OIT value of PP samples;the order of the antioxidant capacity during PP molding processing is: Irganox 300> Irganox 1076> Irganox 1024> Irganox 3114> Irganox 1330> Irganox 1010;polyphenols with hydroxyl groups and high molecular weight hindered phenol antioxidants have the best long-term oxidation resistance;when Irganox 1076 and Chimassorb 944 were used together has a long-term antioxidant effect on PP,the elongation retention rates at break of PP after thermal oxidative aging of 72 h and 144 h were 75.9% and 52.8%,respectively.The retention rates of shear viscosity were 89.9% and 74.1 %,respectively,when the screw rotation rate was 1r/min.2.The extraction process of natural antioxidants was determined based on the polyphenol content.The best ultrasonic extraction process of PSE was as follows: ethanol volume fraction 20%,temperature 55°C,solid-liquid ratio 1:25,time 40 min,and polyphenol extraction amount 6.843±0.93mg/g;The optimum ultrasonic extraction process of grape seed extract(GSE)was as follows: ethanol volume fraction 60%,temperature 55°C,solid-liquid ratio 1:25,time 40 min,and polyphenol extraction amount 10.073±1.13 mg/g;The optimal ultrasonic extraction conditions for seabuckthorn seed extract(SSE)were: ethanol volume fraction 30%,temperature 45°C,solid-liquid ratio 1:25,time 60 min,and polyphenol extraction amount 9.606±0.32 mg/g.3.PSE,GSE,SSE have no effect on the melt temperature of PP sa mple,and have good compatibility with PP;GSE,SSE can increase the crystallization temperature of PP,accelerate the crystallization rate of PP;GSE,SSE will make PP sample appear The obvious ? crystal diffraction peaks have ? crystal nucleating agent function;PSE,GSE,SSE can increase the rheological torque and oxidation induction time of PP samples,and improve the stability of PP samples in hot oxygen environment.,delaying the oxidative degradation of PP specimens;PSE,GSE,SSE can effectively maintain the mechanical properties of PP and the torque value of PP specimens after thermal oxygen aging in the room;the antioxidant performance and added amount of PSE,GSE,SSE are not In proportion,the increase in the amount of addition will cause its agglomeration in the PP matrix,affecting the antioxidant efficiency.The antioxidant effect of PP was best when the addition amount of PSE was 0.5%(wt%),the addition amount of GSE was 0.7%(wt%),and the addition amount of SSE was 0.5%(wt%).Among the PSE,GSE and SSE,GSE had the best antioxidation performance against PP,and had the closest antioxidation effect with synthetic antioxidant 1010.