Sistemas alternativos de ativadores de vulcanização em comparação ao sistema tradicionalmente utilizado em compostos elastoméricos de borracha natural

Abstract

This work evaluated the action of different vulcanization activators (phthalic and terephthalic acid) in comparison to stearic acid in the reaction with ZnO. In addition, sought to verify the possible reduction of the phr content of ZnO in NR-based elastomeric compounds since the release of Zn at different stages of the production process and elastomeric artifacts may cause toxicity to the aquatic environment. Elastomeric compounds were evaluated for rheometric, thermal, physicochemical and chemical properties, as well as mechanical properties after thermo-oxidative aging (7 and 14 days). The release of Zn in the leached extract was verified before and after the vulcanization and after the aging of 14 days. The formulations were developed by varying the phr contents of ZnO (0, 1, 3 and 5) maintaining other fixed components. The elastomeric compounds with different acids and phr contents of ZnO were evaluated by the rheometric, thermal (TG and DSC), morphological and mechanical properties, being these evaluated before and after the thermo-oxidative aging. Analysis of the Zn content of the leached extract was carried out before and after vulcanization and after the aging of the compounds for 14 days. As a result, in the rheometric properties, the compounds with terephthalic acid are shown to have lower t90 and ts1 results. The best results of mechanical properties were found in the compounds with stearic and terephthalic acid with ZnO. Phthalic and terephthalic acids are more reactive than stearic acid, requiring smaller amounts of acids to react with the contents of 1, 3 and 5 phr of ZnO added in the compounds. The compound containing 3 phr of ZnO and stearic acid presented the best combination of properties evaluated among the other compounds using this acid, besides showing an increase in the retention of density of crosslinks after the aging of 7 and 14 days, indicating, based on this study that it is possible to reduce the amount of this used in the elastomer industry. Finally, considering all the evaluated acids, the activation system that presented the best results, considering rheometric, mechanical, thermal and chemical properties, besides presenting the best behavior against thermo-oxidative aging, was with terephthalic acid and ZnO. [resumo fornecido pelo autor]