The main objective of this work was to investigate influence of natural rubber (NR) types on mechanical, thermal, morphological, and curing properties together with relaxation behavior of geopolymer filled NR composites with and without bis(triethoxysilylpropyl) tetrasulfide (TESPT) silane coupling agent. Three alternative types of NR: unmodified NR, and epoxidized NR with 25 (ENR-25) or 50 mol % epoxide (ENR-50) were exploited. Rubber compounds filled with GP particles were prepared in an internal mixer at 60 C and 130-150 C for the ones with and without TESPT, respectively. It was found that incorporation of GP significantly affected cure characteristics and mechanical properties of the rubber composites. That is, decreasing cure time was observed from 11.6, 3.2, and 7.0 min in gum NR, ENR-25, and ENR-50 to 6.9, 2.1, and 5.0 min in NR/GP, ENR-25/GP, and ENR-50/GP compounds, respectively. Furthermore, the ENR-25/GP and ENR-50/GP composites showed finely dispersed GP particles which indicate high fillerrubber interactions. The in situ silanization with TESPT in rubber composites enhanced the mechanical properties of NR/GP and ENR-25/GP composites but no such enhancement was found in the ENR-50/GP composite. This matched the observations of Payne effect, maximum tan δ, and stress relaxation properties of the composites. We found that the ENR-25/GP composites exhibited the best overall properties.

The main objective of this study was to apply geopolymer (GP) particles as novelty fillers in natural rubber (NR) composites with various loadings (0, 10, 20, 30, and 40 phr). Influence of GP particles on cure characteristics, mechanical, dynamic, thermal, and morphological properties of the NR/geopolymer composites was investigated. It was found that incorporation of geopolymer particles significantly affected the cure characteristics and the mechanical properties. That is, faster curing was observed due to acceleration by metal oxide impurities. It was also found that 100% modulus and tensile strength increased with the addition of 10 phr GP. This is attributed to the physical interactions of GP particles with NR molecules. In addition, the Payne effect and improved thermal stability were also observed in the GP-filled NR composites. It was concluded that 10 phr of GP in NR composites might be suitable for some industrial applications. K E Y W O R D S composites, geopolymer, mechanical properties, natural rubber, thermal properties 2652 |

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