The influence of nanosilica on styrene free radical polymerization kinetics

Abstract

A series of nanocomposites were prepared by in situ polymerization of styrene with different silica content (1, 3, and 5 wt%) with an average particle size of 7 nm. The influence of nanosilica content on the kinetics of styrene free radical bulk polymerization was studied by isothermal differential scanning calorimetry (DSC) at different temperatures (70, 80, and 908C). Using appropriate kinetic model, describing two reactions observed during styrene polymerization (the first-order reaction and autoacceleration), it was found that silica presence does not affect the apparent activation energies of both processes. The adsorption of styrene on the silica surface caused the formation of interfacial layer in the structure of hybrid materials. Using suggested equation, the thickness of the interfacial layer was determined to investigate its influence on the glass transition temperature of polystyrene (T g ), which was found not to be affected by silica addition. POLYM. COMPOS.,

The influence of oxide nanoparticles on the kinetics of free radical methyl methacrylate polymerization in bulk

“…The heat release after t 0 is most probably caused by the initiator decomposition and the formation of free radicals. In our previous research, the induction period during styrene polymerization was not observed . For the further investigation of polymerization kinetics, it is necessary to transform isothermal DSC data, in order to describe only the polymerization reaction without induction time.…”

“…Polymerizations were performed under isothermal conditions at 70°C. The amount of polymerized monomer (proportional to the heat released during the reaction) was calculated from the area between the isothermal DSC curve and the baseline using the method described in the literature . The amount of unreacted monomer was determined by prolonging the polymerization in the dynamic regime, from the temperature of isothermal polymerization to 220°C, at a heating rate of 10°C min −1 .…”

“…Free radical bulk polymerization of methyl methacrylate (MMA) can be explained by the classical theory up to certain monomer conversion, after which a sudden rise of the polymerization rate occurs, called autoacceleration . Several theories have been developed to study the autoacceleration phenomenon during the radical polymerization of styrene, methyl methacrylate, and other vinyl monomers, based on its origin and mechanism .…”

“…Several theories have been developed to study the autoacceleration phenomenon during the radical polymerization of styrene, methyl methacrylate, and other vinyl monomers, based on its origin and mechanism . MMA polymerization is described with the same characteristic points (the onset of acceleration, the maximum of the polymerization rate and the end of polymerization) as the polymerization of other lower alkyl methacrylates and styrene .…”

“…In order to enable a completely control of PMMA nanocomposites preparation in industrial conditions, it is necessary to investigate the influence of nanoparticles on the kinetics of free radical bulk polymerization. In this purpose, it is desirable to find a suitable kinetic model that can describe not only the polymerization of pure monomers, but to quantitatively monitor the changes of the kinetic parameters due to addition of different nanoparticles . It is also important to investigate the influence of the structure and mobility of formed interfacial layer on the end‐use properties of PMMA hybrid materials.…”