Synthesis Of Phenolic Antioxidants Based On Calixarene And Their Thermo-oxidative Aging Resistance For Natural Rubber

Natural rubber(NR) is a kind of natural polymer material with good comprehensive performance, which is widely used in health care, aerospace, tire industry and other fields. But due to NR containing a large number of unsaturated double bond and methine, it is easy to suffer from aging in the process of processing, storage and using, which lead to significant degradation of mechanical properties and final loss of use value. In order to inhibit or delay the aging process of NR and improve its service life, it is necessary to add the antioxidant. However, due to small molecule, traditional antioxidant tend to migrate and volatilize, leading to the loss of protective function.C-Methylcalix[4]resorcinarene(calix[4]arene) with suitable molecular weight contains eight phenolic hydroxyl groups, which has oxidative resistance, and its performance can be further improved through chemical reaction. In this issue, C-Methylcalix[4]resorcinarene, sulfonic lanthanum based on calix[4]arene, calix[4]arene derivative-1(calix[4]arene-1) and calix[4]arene derivative-2(calix[4]arene-2) were synthesized. The thermal-oxidative aging resistance of them for NR vulcanizates and their extraction resistance were investigated. The main research contents and results are as follows:Firstly, calix[4]arene and sulfonic lanthanum based on calix[4]arene were synthesized and characterized by FT-IR, ~1H-NMR, ~13C-NMR, elemental analysis, EDS, TGA and HRMS. Both of them had less effect on the mechanical properties of NR. Calix[4]arene could enhance the thermal-oxidative aging resistance of NR, when the amount was more than 0.5 phr, the effect of various amount of calix[4]arene on the thermal-oxidative aging resistance of NR was slightly different. Sulfonic lanthanum based on calix[4]arene could enhance the thermal-oxidative aging resistance of NR, with the increase of the amount of sulfonic lanthanum based on calix[4]arene, the thermal-oxidative aging resistance was improved.Secondly, the thermal stability in nitrogen of calix[4]arene was better than that of sulfonic lanthanum based on calix[4]arene, the thermal stability of BHT was the worst. The thermaloxidative aging resistance of calix[4]arene for NR was equivalent to that of BHT. Sulfonic lanthanum based on calix[4]arene showed better thermal-oxidative aging resistance for NR than calix[4]arene and BHT. After boiling methanol extraction for 48 h, then 100 oC thermal oxidative aging for 48 h, the retention rate of aging coefficient of NR with calix[4]arene, sulfonic lanthanum based on calix[4]arene and BHT were 86%, 78% and 82%, respectively. The extraction resistance of calix[4]arene in NR was better than that of BHT, the extraction resistance of BHT was better than that of sulfonic lanthanum based on calix[4]arene.Thirdly, calix[4]arene-1 containing side chain and calix[4]arene-2 containing sulfurated side chain were synthesized and characterized by FT-IR, ~1H-NMR, and HRMS. Calix[4]arene-1 had less effect on the mechanical properties of NR. Calix[4]arene-1 could enhance the thermal-oxidative aging resistance of NR, with the increase of the amount of calix[4]arene-1, the thermal-oxidative aging resistance was improved. The calix[4]arene-2 had slight effect on the mechanical properties of NR, with the increase of the amount of calix[4]arene-2, the elongation at break of NR increased slightly and the tensile strength of NR decreased slightly. Calix[4]arene-2 could enhance the thermal-oxidative aging resistance of NR, with the increase of the amount of calix[4]arene-2, the thermal-oxidative aging resistance was improved.Fourthly, the thermal stability in nitrogen of calix[4]arene-2 was better than that of 2246 S, both of them were better than that of calix[4]arene-1. The thermal-oxidative aging resistance of calix[4]arene-2 for NR was equivalent to that of 2246 S, both of them were better than that of calix[4]arene-1. After boiling methanol extraction for 48 h, then 100 oC thermal oxidative aging for 48 h, the retention rate of aging coefficient of NR with calix[4]arene-1, calix[4]arene-2 and 2246 S were 83%, 86% and 79%, respectively.The extraction resistance of calix[4]arene-2 in NR was better than that of calix[4]arene-1, the extraction resistance of calix[4]arene-1 in NR was better than that of 2246 S.