A Fourier Transform Infrared (FTIR) analysis using Fresnel Attenuated Total Reflectance (ATR) was performed on silica-filled cis-1,4-polyisoprene. Silica filler's detrimental effects on zinc-activated cure systems has been well documented. The silane coupling agent bis-(gamma-triethoxysilylpropyl) tetrasulfide (Si-69) and polyethylene glycol (PEG) are industry standards used to offset the interactions caused by reaction between silica and the zinc-activated cure system. By adding PEG, it was found that the interaction peaks at 1040 and 1017 cm(-1) caused by the adsorption of natural rubber (NR) onto the surface of the silica were not formed. Also, by monitoring the zinc stearate peak at 1540 cm(-1), both Si-69 and PEG were found to reduce the soluble zinc ion reaction with the silica surface. Supporting evidence from the rheometer curves also shows that the additives reduce the cure retardation effects of the silica filler.