Dispersion and vulcanization characteristics of nitrile rubber reinforced with N,N-dimethylacetamide/lithium chloride treated silica

N,N-Dimethylacetamide/lithium chloride (DMAc/LiCl) treated silica is used as a reinforcing filler in nitrile rubber (NBR). Effect of the treatment on aggregate morphology and dispersion of silica in the matrix is investigated using XPS, SEM, and AFM. Binding energy levels of O1s and Si2p electrons in DMAc/LiCl treated silica have shifted significantly from 532.49 to 530.98 eV and 103.19 to 101.33 eV respectively. SEM observations have revealed a reduction in the agglomerate size of silica-a desirable feature for realizing better processing properties of silica filled rubber compounds. Data from AFM observations have also shown better dispersion of DMAc/LiCl treated silica. Mooney viscosity of masterbatches, measured at 100 degrees C over a period of 7 days, has not exhibited any storage hardening which is an indication of easier processability. At 125 degrees C, Mooney data exhibited a reduction in scorch time as a function of DMAc/LiCl concentration. However, MDR data at 160 degrees C have not shown much changes in the scorch time while NBR with high nitrile content exhibited longer cure times. Higher crosslink density of vulcanizates indicate that DMAc/LiCl treatment of silica could effectively reduce filler-filler interactions and networking in silica filled rubber compounds thereby enabling mixing and processing operations energy efficient.

Automated summary

The study on DMAc/LiCl treated silica in NBR has shown improved dispersion and processing properties, as well as reduced filler-filler interactions. This treatment can effectively enhance energy efficiency in mixing and processing operations of silica filled rubber compounds.