The sulfur reversion process in natural rubber in terms of crosslink density and crosslink density distribution |
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| Institution: | 1. Department of Chemical Engineering, Engineering Faculty, University of Sumatera Utara, Medan, 20155, Sumatera Utara, Indonesia;2. School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia, Engineering Campus, Nibong Tebal, 14300, Penang, Malaysia;1. IFIMAT y CIFICEN (CONICET-UNCPBA), Pinto 399, B7000GHG Tandil, Argentina;2. Laboratorio de Polímeros y Materiales Compuestos, Departamento de Física, Universidad de Buenos Aires, Ciudad Universitaria, C1428EHA Buenos Aires, Argentina;3. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina;4. Comisión de Investigaciones Científicas de la Provincia de Buenos Aires (CICPBA), Argentina;1. Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy;2. CHEM. CO Consultant, Via J.F. Kennedy 2, 45030 Occhiobello, Rovigo, Italy |
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| Abstract: | Unfilled natural rubber compounds composed of conventional (CV), semi-efficient (SEV), efficient (EV) and sulfur donor (SD) vulcanization systems were heat aged to promote sulfur reversion. Rheometry, hardness, strain-strain characteristics including Mooney-Rivlin analysis, equilibrium solvent swell and Double Quantum (DQ) Nuclear Magnetic Resonance (NMR) were used to monitor crosslink density changes. A loss of crosslink density was observed by rheometry, C1, equilibrium swelling and by DQ NMR as a function of cure extent. No chain scission reactions were operating in the time/temperature conditions used. All crosslink distributions were unimodal and the network homogeneity followed the order of EV > SD > SEV > CV. The crosslink distribution narrowed during the curing process for the CV and SEV systems. Non-oxidative maturation reactions were advantageous in promoting a more random distribution of crosslinks in the polymer matrix. |
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| Keywords: | Conventional vulcanization Crosslink density Crosslink density distribution Efficient vulcanization Natural rubber Poly(isoprene) Semi-efficient vulcanization Sulfur donor |
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