Interfacial Modification Of Filler Reinforced Rubbers With Ionic Liquids

An ionic liquid (IL), 1-butyl-3-methyl-imiazolium hexafluorophosphate BMIM.PF₆, was employed to modify carbon black (CB) under microwave (MW) irradiation. The modified CB (m-CB) was used to reinforce the nitrile rubber (NBR) and butadiene rubber (BR). The structure of m-CB, vulcanization characteristics of the NBR/m-CB compounds, mechanical properties of vulcanizates and possible reinforcement mechanism were studied.According to the surface area and pore analysis of the m-CB, it was showed that part of IL can be strongly absorbed onto the CB surface. The interaction between IL and CB was verified by Raman spectroscopy (Raman) and X-ray photoelectron spectroscopy (XPS). Part of IL was decomposed into HF under microwave irradiation. The vulcanization of the compound was retarded by m-CB. Compared with the unmodified CB, the elongation at break, tensile and tear strength of NBR/m-CB vulcanizates were obviously improved, though the modulus and hardness were decreased. In addition, similar results have been obtained in BR/m-CB composites. According to the results of crosslink density, DMA and the morphology observations, the possible mechanism of reinforcement was proposed.Then, BMIM.PF₆ was coated onto halloysite nanotubes (HNTs) in THF/water mixture. The IL layers on the HNTs were confirmed by thermogravimetric analysis (TGA), diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, determination of contact angle and porosity analysis. The interaction between IL and HNTs, proposed to be hydrogen bonding, was verified by various spectral results such as Raman spectroscopy, nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS). Due to their interaction, the crystallization behavior of IL in the presence of HNTs was found to be changed as indicated by the results of differential scanning calorimetry (DSC). The IL coated HNTs (m-HNTs) were used as reinforcement for styrene-butadiene rubber (SBR). Compared with the compounds with uncoated HNTs, the uncured compounds with m-HNTs showed faster curing and the resulting vulcanizates showed substantially higher tensile strength and much lower hardness. The unique changes in the compounds are correlated to the changes in filler dispersion and interaction between IL and HNTs.Finally, BMIM.PF₆ and VHIM.BF₄ was coated onto Silica by co-coagulation process with styrene-butadiene latex (SBRL). Similarly, the irreversible sorption of BMIM.PF₆ layers onto Silica was observed by TGA, determination of contact angle, specific surface area (BET) and etc. The interaction between BMIM.PF₆ and Silica was verified by Fourier transform infrared spectroscopy (FTIR), XPS, DSC and 1H NMR. Compared with the compounds of SBR/Silica, the uncured compounds with ionic liquid showed faster curing, the resulting vulcanizates showed higher tensile strength and better wear resisting property. The possible modification mechanism was dicussed. Compared with the composite modified by BMIM.PF₆, those with VHIM.BF₄ possessed higher mechanical properties and abrasion resistance.