Enhanced gas permeability of HyIIR/CB/OMMT composites constructed from hydroxyl groups and OMMT/CB with strong interactions

Abstract

Isobutylene-isoprene rubber (IIR) has excellent airtightness, damping, and aging resistance due to its dense side groups and highly saturated main chain. However, the low unsaturation of IIR makes it weak in interaction with fillers. Therefore, the modification of IIR to improve the interaction of IIR with fillers will be critical for the preparation of high performance IIR composites. The introduction of reactive polar groups into IIR was an excellent solution. In this study, a novel modified IIR-hydroxyl functionalized IIR (HyIIR) was prepared and compounded with organic montmorillonite (OMMT) and carbon black (CB) fillers. Due to the stronger interfacial interactions between the rubber and the filler, the dispersion of OMMT achieved nanoscale without adding any modifier, and the gas barrier property of the rubber composites was significantly improved as compared to those of IIR or brominated IIR (BIIR) composites. The HyIIR/CB/OMMT composites were prepared by mechanical blending and sulfur package was used to vulcanize HyIIR via the reaction with vinyl groups. The effects of the dosage of OMMT and sulfur on the processing and application properties of the rubber composites were investigated. X-ray photoelectron spectroscopy (XPS) results proved that hydroxyl groups on HyIIR were successfully reacted with the surface groups on OMMT. X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM) confirmed the significant increase of the spacing of OMMT layer and nanoscale disperses of OMMT in HyIIR matrix. Payne's effect and dynamic thermo-mechanical (DMA) results indicated that the OMMT and CB particles were more uniformly dispersed in HyIIR than in IIR and had stronger interfacial interactions with the rubber macromolecule. By adjusting the amount of S, the vulcanization time was shortened from 47 to 37 min after adding fillers (OMMT and CB) to the HyIIR matrix, and the tensile strength of HyIIR/CB/OMMT composites reached up to 13.9 MPa and the elongation at break was about 750%. More importantly, the air tightness of HyIIR/CB/OMMT composites was greatly improved. The gas permeability coefficient of HyIIR/CB/OMMT composites with only 1 phr OMMT was improved by 68% (61%) and 48% (44%) relative to IIR/CB (BIIR/CB) and IIR/CB/OMMT (BIIR/CB/OMMT) composites, respectively. The use of hydroxyl-functionalized IIR species compounding with OMMT provides a new and innovative approach for improvement of the airtightness of IIR composites, which was expected to be widely used in the field of tire air-sealing layers or inner tube with high demand for the airtightness.

Highlights

• An novel functionalized IIR-HyIIR was synthesized and compounded with fillers.
• The fillers showed nano-dispersion in HyIIR matrix.
• Strong interfacial interaction forces were formed between the filler and HyIIR.
• The airtightness of the composite was significantly improved.