Natural Rubber bound 4-Aminodiphenylamine Antioxidant for Rubber Formulation Improvement

This research work was aimed to prepare the natural rubber bound 4-aminodiphenylamine (NRbound-4-ADPA) for replacing typical antioxidant used in the conventional rubber formulation.Epoxidized natural rubber with 30 %mol epoxide (ENR-30) was first prepared by performicepoxidation using high ammonia concentrated latex (60% DRC), Teric N-10 stabilizer, HCOOH/H2O2at 50 oC for 6 hr and 15 min. Reaction of ENR-30 with 4-aminodiphenylamine (4-ADPA) was thencarried out in toluene solution at 80 oC for 3, 6, 12 and 12 hrs. The content of 4-ADPA bound tonatural rubber molecules was determined by using standard curve of ENR-30/4-ADPA physicalmixing method. It was found that the level of bound 4-ADPA was 1.0, 1.48, 2.61 and 3.95 phr,respectively. The molecular characteristics of ENR and NR-bound-4-ADPA were also investigated bymeans of IR spectroscopy. The absorption bands at 870 cm-1 and 1596 cm-1 corresponding to epoxidegroup and secondary amine in NR-bound-4-ADPA were observed, respectively. The antioxidantcapability of NR-bound-4-ADPA and conventional 4-ADPA antioxidant in natural rubbervulcanizates was then studied. Improvement of ageing resistance of NR-bound-4-ADPA wasobserved. That is the NR-bound-4-ADPA showed superior oxidation resistance than that of theconventional antioxidant.