Synthesis And Performance Study Of Diphenyl-bridged Hindered Phenol Antioxidants

In the process of processing and using polymer materials,chain degradation and cross-linking reactions occur,resulting in the loss of value of the material.And the addition of antioxidants can greatly delay the aging process of the material and extend the service life of the material.Among them,hindered phenolic antioxidants have gained widespread attention due to the advantages of low toxicity,high thermal stability,not easy to color,good compatibility,etc.,and become one of the most used main antioxidants in the field of polymer materials.However,the current industrial hindered phenol antioxidants are mostly small molecule antioxidants with poor migration resistance and thermal stability,which cannot meet the increasingly complex application systems.Therefore,the synthesis of new hindered phenolic antioxidants with high molecular mass and multiple phenolic hydroxyl groups by introducing special structures and functional groups has become one of the hot research topics in this field.A new series of diphenyl-bridged hindered phenolic antioxidants with two hindered phenolic units were synthesized by amidation condensation reaction usingβ-（3,5-ditert-butyl-4-hydroxyphenyl）propanoyl chloride as the antioxidant group,4,4’-diaminodiphenylmethane and 4,4’-diaminodiphenyl sulfone as the bridging groups,respectively,and triethylamine as the acid binding agent.The structures of the products were characterized by FT-IR,¹HNMR,¹³CNMR,ESI-MS and TG,and the results showed that the synthesized products were consistent with the theoretical design and also had good thermal stability.The radical scavenging ability of diphenyl-bridged hindered phenol antioxidants was evaluated by DPPH·and ROO·.The results showed that both diphenyl-bridged hindered phenols had good DPPH-scavenging ability,and the scavenging rate at steady-state 400 min was basically the same as that of antioxidant 1010 and much better than that of antioxidant1076.The DPPH-scavenging reaction of this series of hindered phenol antioxidants followed the primary reaction kinetics at the scavenging reaction time of 30 min.The diphenyl-bridged hindered phenol antioxidants could capture ROO·well,and the inhibition time increased significantly and the inhibition rate constant decreased with the increase of phenolic hydroxyl concentration.The results by DPPH·and ROO·showed that the two diphenyl-bridged hindered phenol antioxidants had good radical scavenging ability,which was better than that of antioxidant 1076 and comparable to that of antioxidant 1010.The application performance results show that the two diphenyl-bridged hindered phenol antioxidants can significantly improve the processing stability and thermal-oxidative stability of metallocene linear low-density polyethylene,and the improvement effect is greater than that of antioxidant 1076;the rigid structure of the bridging group in the high-pressure hydroxide system is not easy to hydrolysis reaction,so it can well inhibit the occurrence of long-term thermal-oxidative aging of the material,and the enhanced rigidity of the molecular chain can improve the mechanical parameters such as tensile strength and elastic modulus of the material,which is better than commercial antioxidants in improving mechanical properties and more suitable for aqueous systems.The microscopic results show that both diphenyl-bridged hindered phenols have good dispersion in the material and do not agglomerate;the migration in the ethanol system is greater than that in the distilled water system,and the higher the temperature of the system,the greater the migration of the antioxidant.Comparison of several antioxidants found that the two diphenyl-bridged hindered phenol antioxidant and antioxidant 1010 have shown good migration resistance,while antioxidant 1076 migration resistance is poor.