SbstractThis work aims at studying not only the rheological behavior of natural rubber-based compositions by making use of different contents of fluoromica or ME 100 synthetic mica in a natural rubber (NR) matrix, but also the different filler-filler and matrix-filler interactions before and after curing. The ME 100 content in NR varied from 0 to 10 phr (parts per hundred parts of resin) and the results enabled to conclude on the influence of the mineral filler on the curing parameters, as well as on the limit amount of ME 100 for the best performance resulting from the best filler distribution/interaction in the polymer matrix. All data were compared with those of the unfilled composition. Based on complex viscosity, curing parameters, dynamic modulus and Payne effect tests it was concluded that the mica content limit for the best performance was 7 phr.

No abstract

This work investigates natural rubber (NR) composites vulcanized with different combinations of accelerators in efficient cure systems. The NR compounds were characterized for cross-link density, hardness, tensile strength, and dynamical–mechanical properties, before and after aging. Among the cure systems used, that containing the highest amount of free sulfur presented the best mechanical performance, before and after aging; concerning dynamic properties after the aging, the composition with a lower number of cross-links was the best.

The effect of different crosslink structures was studied in nanocomposites obtained by co-precipitation of natural rubber (NR) latex and aqueous solution of cellulose xanthate for obtaining nanocellulose. Cure systems characterized as conventional (CV), semi-efficient (SEV), and efficient (EV) were used in compositions of NR and also in natural rubber/cellulose (NR/CEL) nanocompositions with 15 phr of cellulose. The characterization of the developed compositions was based on rheological, physical-mechanical, aging, and mechanical properties. The obtained results allowed the conclusion that cellulose is a reinforcing filler as it promoted a significant increase in all these properties, that were sensitive to the cure systems used and protects NR from accelerated aging. The experimental results are presented and discussed also by Payne effect, entropy (ΔS), and Gibbs free energy (ΔG) to enable an understanding on cellulose distribution throughout NR influenced by the different cure systems.

No abstract

Resumo: A técnica de caracterização por calorimetria diferencial de varredura (DSC) foi empregada para analisar a influência do teor de argila Cloisite 15A nas propriedades térmicas de compósitos de poli(tereftalato de etileno) (PET) reciclado. A avaliação das amostras por DSC mostrou que houve aumento na temperatura de transição vítrea para maiores teores de argila. A temperatura de cristalização foi deslocada para menores valores. Na temperatura de fusão houve pouca interferência, porém, os resultados das entalpias de fusão e cristalização demonstraram que a argila promoveu um efeito nucleante nos compósitos.

Resumo: Os compósitos de poli(tereftalato de etileno) (PET) e argila organofílica Cloisite 15A (C15A) com matriz reciclada foram obtidos por intercalação no estado fundido. A análise morfológica pela microscopia eletrônica de varredura mostrou que houve a intercalação da argila na matriz de PET reciclado, cujos resultados da ressonância magnética nuclear corroboraram com esta afirmação. A análise termogravimétrica também mostrou que maiores teores de argila aumentaram a estabilidade térmica dos materiais compósitos.

No abstract