ORIGINAL PAPER Silica-graphene oxide nanohybrids as reinforcing filler for natural rubber Methus Charoenchai 1 & Siree Tangbunsuk 1 & Wirunya Keawwattana 1 # The Polymer Society, Taipei 2020 Abstracts Hybrid silica-graphene oxide (SiO 2 @GO) nanocomposites were fabricated by sol-gel method using tetraethylorthosilicate (TEOS) as silica (SiO 2 ) precursor. The prepared nanocomposites were characterized by various analytical techniques to prove that the SiO 2 were completely incorporated on the GO surface. Then, the SiO 2 @GO nanocomposites were introduced into natural rubber (NR) matrix followed by conventional vulcanization process, performed by two-roll mill, to obtain NR/SiO 2 @GO vulcanizate. The results showed that the presence of SiO 2 nanoparticles on the GO surface improved the distribution of GO in NR matrix, resulting in the increase in modulus and hardness. For comparison with neat NR, NR/SiO 2 , and NR/GO, the network parameters of vulcanizates were evaluated using swelling test and tube model theory contributed in stress-strain measurement. These exhibited that the SiO 2 @GO induced the chemical crosslink between NR chains, leading to the increment in crosslink density. It was because the well dispersion of SiO 2 @GO in NR matrix improved the volume fraction of rubber. Moreover, dynamic mechanical analysis was employed to determine the viscoelasticity behavior of the vulcanizates. The results showed that the presence of SiO 2 @GO in NR vulcanizate improved the storage modulus in all temperature range. That meant the elasticity of the vulcanizates was improved by the reduction of the viscous phase to stiff phase ratio of the material. However, the reinforce- ment of NR using SiO 2 @GO as filler was effective in lower deformation reflected from higher modulus at low strain. In addition, the modulus decreased in comparison with that of the neat NR under higher deformation until at break point. Thus, the tensile strength decreased while elongation at break increased. This phenomenon might be explained that the strain-induced crystalli- zation of NR occurred under higher strain was reduced because the rubber chains alignment which was obstructed by the filler penetration and high number of chemical crosslinks. Therefore, the covalent hybrid SiO 2 @GO nanocomposites had potential for use as filler in engineering rubber composites that were suitable for the compressive or abrasive applications. Keywords Graphene oxide . Silica . Natural rubber . Nanohybrids . Tube model Introduction In the rubber industry, the kind of the additives which is po- tentially powerful is such reinforcing fillers that used to im- prove the properties of rubber vulcanizate. Nevertheless, the rubber properly processed by vulcanization with various chemicals to obtain useful vulcanizate is a key to use rubber materials for desired applications. Carbon black (CB) and sil- ica (SiO 2 ) have been widely used as reinforcing fillers to en- hance the physical and mechanical properties of rubber vulca- nizates for long time. CB was the one of the long-established nanotechnology applications and nanomaterials used to mod- ify the mechanical, electrical, and other physical properties of polymers. [1, 2] Especially in green tire manufacturing, SiO 2 was potentially used to reduce the rolling resistance also in- creased the abrasion resistance and wet grip bringing a reduc- tion in fuel consumption and vehicle CO 2 emissions. [3] Technically, however, the high surface energy due to the hy- drophilic properties of silanol group and large surface area induced the aggregation leading to poor mechanical properties than expectation. Thus, the combination of silica and carbon black was more effective for some applications. [4] * Wirunya Keawwattana fsciwyk@ku.ac.th Methus Charoenchai methus.cha@gmail.com Siree Tangbunsuk siree.t@ku.ac.th 1 Department of Chemistry, faculty of science, Kasetsart University, Bangkok, Thailand Journal of Polymer Research (2020) 27:230 https://doi.org/10.1007/s10965-020-02209-y