Chemistry, Physics and Technology of Surface

ISSN 2518-1238 (Online), ISSN 2079-1704 (Print)

Fumed silica (FS) is widely used in numerous fields of application, the plastics industry being one of the most significance, where FS has proved to be successful as an efficient thickening, thixotropic, and anti-settling agent, as well as reinforcing filler. Chemical modification of silica surface enlarges its functional capabilities. In particular, silica with grafted silicon hydride groups was found to be active in the processes of hydrosilylation of alkene and alkyne bonds in monomers during their polymerization, resulting in the formation of reinforced polymeric composites. Recently, specific epoxy resins have gained significance, and FS was found to be useful, particularly as rheological additive. The aim of this study was to evaluate the efficiency of hydride-silylated FS (HFS) as a potentially active reinforcing component for epoxy-based polymers. The activation energy for hydrosilylation of olefins is higher than that for ring-opening polymerization of epoxides, therefore, one may expect the latter process with participation of ≡SiH groups to proceed more readily.

HFS was obtained via FS treatment with triethoxysilane. The presence of grafted silicon hydride groups was confirmed by means of IR spectroscopy, and their concentration measured by titrimetric and spectrophotometric analysis was found to be about 0.4 mmol/g. FS-epoxy and HFS-epoxy composites were prepared by the corresponding filler introduction (2 wt. % loading) into the mixture of epoxy monomer and amine hardener. The resulted materials after curing were subject to compression, bending, and adhesion tests.

Compression tests revealed that filling with FS and HFS reduced the compressive strength by 10%, however, HFS-epoxy composite was found to possess an increased by 20 % Young’s modulus for compression as compared to that for the unfilled epoxy polymer. Upon this, 2 wt. % loading with silicas keeps the ductility of the polymer. Also, silica-containing epoxy polymers showed an improved bending strength and bending modulus, the former being two times higher for HFS-epoxy composite than that for the unfilled polymer. The adhesion to steel was found to increase by more than 2 times upon filling with silicas, HFS-epoxy composite being also superior as compared to the          FS-epoxy one. Thus, preliminary results indicate that fumed silica with grafted silicon hydride groups shows promise as active reinforcing filler for epoxy polymers.

1. Barthel H., Rösch L., Weis J. Fumed Silica - Production, Properties, and Applications. In: Organosilicon Chemistry II: From Molecules to Materials. (Weinheim, New York, Basel, Cambridge, Tokyo: VCH, 1996).

2. Chuiko A.A. Medicinal chemistry and clinical use of silicon dioxide. (Kyiv: Naukova Dumka, 2003). [in Russian].

3. Technical Bulletin Fine Particles No. 27. AEROSIL® fumed silica for solvent-free epoxy resins. Evonik Industries AG.

4. Ivashchenko N.A., Katok K.V., Tertykh V.A., Yanishpolskii V.V., Khainakov S.A. Silica with grafted silicon hydride groups and its application for preparation of palladium nanoparticles. Int. J. Nanopart. 2011. 4(4): 350. https://doi.org/10.1504/IJNP.2011.043497

5. Kuzema P.O., Laguta I.V., Stavinskaya O.N., Tsyba N.N., Tertykh V.A. Fumed silica with grafted silicon-hydride groups as a redox-active component in the composite with caffeic acid. Dopov. Nac. akad. nauk Ukr. 2020. 5: 78. [in Ukrainian]. https://doi.org/10.15407/dopovidi2020.05.078

6. Bolbukh Yu.N., Mamunya Ye.P., Tertykh V.A. Thermomechanical properties of polymeric composites based on 2-hydroxyethylmethacrylate and fumed silicas. J. Therm. Anal. Calorim. 2005. 81(1): 15. https://doi.org/10.1007/s10973-005-0738-y

7. Sprenger S. The effects of silica nanoparticles in toughened epoxy resins and fiber-reinforced composites. (Munich: Hanser Publishers, 2016). https://doi.org/10.3139/9781569906286

8. Starokadomsky D.L. On the influence of non-modified nanodispersed silica of various specific surfaces on physicomechanical properties of epoxy-polymeric composites. Russ. J. Appl. Chem. 2008. 12: 2045. [in Russian].

9. Crivello J.V., Fan M. Novel platinum-containing initiators for ring-opening polymerizations. J. Polym. Sci. Pol. Chem. 1991. 29(13): 1853. https://doi.org/10.1002/pola.1991.080291303

10. Bereza-Kindzerska L.V., Yanishpolskii V.V., Tertykh V.A. Spectrophotometric determination of soluble forms of silica and of some surface compounds. Naukovi zapysky NaUKMA. Khimichni nauky ta tehnologii. 2007. 66: 53. [in Ukrainian].

11. Islam M.S., Masoodi R., Rostami H. The effect of nanoparticles percentage on mechanical behavior of silica-epoxy nanocomposites. J. Nanosci. 2013. 2013(2): 1. https://doi.org/10.1155/2013/275037

12. Braum M.V., Jacoby M.A.M. Kinetic behavior of the reaction between silica and epoxidized liquid rubber. Polimeros. 2016. 26(4): 291. https://doi.org/10.1590/0104-1428.2180