Abstract
p-tert-butylcalix[4]arene (C4), p-tert-butylcalix [6]arene (C6) and p-tert-butylcalix[8]arene (C8) were synthesized and explored as antioxidants for polypropylene (PP). The structures of these compounds were characterized by 1H-NMR and FTIR, and their antioxidation efficiencies for PP were evaluated by rheology analysis, differential scanning calorimetry (DSC), melt flow index analysis, and thermogravimetric analysis (TGA). The rheology results from a Haake Polydrive mixer revealed that calix[n]arenes had little effect in preventing PP from degradation during the processing, and the DSC analysis showed that the antioxidation performance of the calix[n]arenes for PP was in the order of C4 > C6> C8. The values of melt flow index indicated that calix[n]arenes, especially C4 and C6, could largely improve the thermal stability of PP, and the activation energies for degradation of PP with C4, C6 and C8 calculated with the data from TGA were 97.05, 84.60 and 53.69 kJ/mol, respectively.