Silica surfaces chemistry and thermooxidation of vulcanized styrene butadiene rubber compoundsAuthor(s): JiriMalac
Styrene butadiene rubber (SBR) is foremost synthetic rubber usedmainlyin combinationwith reinforcing fillers for automotive tire treads. Carbon black and silica are themost important reinforcing fillers and surface chemistryof both these fillers is different. OneSBRcompound filledwith carbon black (CB) only and one compound filedwithCBand silicawere prepared and vulcanized.The thermal oxidative stabilityof obtained SBR-CBand SBR-CB-Si sampleswas tested by differentmethods. The thermogravimetric curve fromthermal gravimetric analysis (TGA) shows main difference between both samples in ceramic yield athightemperatures.Thedifferential thermogravimetric curve shows two distinct peaks of diverse shape for samples with and without silica. One peak for compound SBR-CB and two peaks for compound SBROriginal CB-Siwere obtained bydifferential scanning calorimetry (DCS). Themost significant difference between samples SBR-CB and SBR-CB-Si shows ratio (loss factor) / (absolute value of complex tensilemodulus) in dependence on temperature, measured by dynamic mechanical analysis (DMA).Chemical differences between SBR-CB and SBR-CB-Si samples, caused by presence of silica and detectable by FTIR spectroscopy, endure prolonged heating ofmaterials and explain different thermal degradation course of both samples. Surface chemistryof fillers so influences not onlyinteractions filler-fillerandfiller-polymer(connected withmechanical properties ofmaterials) but also complex of chemical reactions connectedwith stability of polymers.