Applications Of Natural Polyphenols In The Modification Of Polyolefins

Natural polyphenols are natural hindered phenolic antioxidants,commonly used in our daily life.Because of their good anti-free radical,anti-oxidation and anti-aging properties,they are widely used in food additives,health products,natural dyes and organic materials and so on.In recent years,the applications of natural antioxidants in the field of polymers attracted much attention.Therefore,the antioxidant properties of natural polyphenols in the modification of polyolefins were studied in this thesis.Firstly,two natural and edible substances,lyceum chinense fruits and celery,were chosen.The phenolic compounds contained in these two substances were extracted with organic solvents.The obtained phenolic compounds were used as primary antioxidant,and tetrakis(2,4-di-tert-butylphenol)4,4'-biphenyl bisphosphite(P-EPQ)was used as secondary antioxidant in the modification of polypropylene(PP).Results showed that celery and lyceum chinense fruits could improve the antioxidant stability of PP.Secondly,the extract of bamboo leaf concentrate containing 40%bamboo leaf flavonoids(AOB)was purified by solvent extraction,and the components of the extracts were identified by liquid chromatograph/mass spectrometer(LC-MS).Then the extracts and P-EPQ were used into PP modification.Results showed that AOB coupled with P-EPQ could improve the thermo-oxidative and processing stability of PP;The effiency of AOB was comparable with that of Irganox 1010 in protecting PP.However,due to the deep yellow color of the AOB,the problem of discoloration of the polymer matrix has not been solved.Finally,puerarin and P-EPQ were compounded in the modification of polyethylene(PE).Results showed that puerarin could interact with P-EPQ,and such interaction was essential in improving the antioxidant property of PE.However,because puerarin makes the PE sample yellow,it could be used in the fields with color tolerance.On the other hand,puerarin could be used as a coloring agent.