Fabrication of natural rubber/epoxidized natural rubber/nanosilica nanocomposites and their physical characteristics

Use of TBzTD as Noncarcinogenic Accelerator for ENR/SiO2 Nanocomposites: Cured Characteristics, Mechanical Properties, Thermal Behaviors, and Oil Resistance

“…Natural rubber (NR) is one of the most important natural biosynthesis polymers and renewable resources that possesses excellent mechanical properties owing to its ability to crystallize upon stretching (strain-induced crystallization), but its thermal, oxidation, and oil resistance cannot compete with some special purpose synthetic rubbers [1][2][3][4][5][6][7][8][9][10][11][12]. This is a normal consequence of its highly unsaturated hydrocarbon chain structure and nonpolar nature [2][3][4].…”

“…The first one included the "in situ" formed peracid generated from the endothermic reaction of hydrogen peroxide (H 2 O 2 ) and the acid, followed by the exothermic epoxidation reaction, leading to an increased polarity and a reduction in the C=C in the rubber chains [5,8,9,[12][13][14][15][16][17][18]. As a consequence, ENR would have oil and oxidation resistance comparable to some of the synthetic rubbers, depending on the extent of epoxidation (mol% epoxidation) [5,9,10,12]. It has been reported that ENR with 50 mol% epoxidation exhibits oil resistance similar to that of medium-acrylonitrile-content nitrile rubber and superior to that of chloroprene rubber [9,12,19].…”

“…As a consequence, ENR would have oil and oxidation resistance comparable to some of the synthetic rubbers, depending on the extent of epoxidation (mol% epoxidation) [5,9,10,12]. It has been reported that ENR with 50 mol% epoxidation exhibits oil resistance similar to that of medium-acrylonitrile-content nitrile rubber and superior to that of chloroprene rubber [9,12,19]. As the level of epoxidation increases more than 50 mol%, the ENR products become harder and of less resilience and elasticity at room temperature (RT), whereas the products of lower epoxide content are typical elastomers with less oil resistance [8,10,17].…”

“…With this respect, the TBzTD, a fast curing accelerator with no secondary amine, has been developed to replace the TMTD, resulting in the nitrosamine free cure. Recently, reinforcement of rubbers with inorganic nanoparticles, even at a very low loading, can significantly improve their mechanical and thermal properties [9,10,19,[21][22][23][24][25]. To achieve the desired properties, the nanofillers must sufficiently disperse in the rubber matrix, as poor dispersion leads to the obvious decrease in the performance properties of the nanocomposites.…”

“…Nanosilica (nSiO 2 ) is an inorganic filler with a large number of hydroxyl (-OH) groups on its surface and thus provides strong filler-filler interactions to generate nSiO 2 aggregates and agglomerates. However, the epoxide groups of ENR can effectively cause a specific interaction between nSiO 2 and ENR via hydrogen bonding, leading to a decrease in filler-filler interaction and an increase in compatibilization [9,[22][23][24]. With this respect, ENR nanocomposites can be directly prepared using nSiO 2 as a nonblack reinforcement without the aid of any coupling agents or pretreatments [9,12].…”