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Achieving clay dispersion and improving clay−polymer interactions are keys to producing superior nanocomposites. A supercritical CO2 (scCO2) processing method was utilized to prepare high molecular weight polystyrene (PS)/Cloisite 10A nanocomposites with significant dispersion and rheological enhancement. The effects of scCO2 processing, presence of cosolvent, and clay weight fraction on clay dispersion and polymer−clay interactions in nanocomposites were investigated. Rheology, WAXD, and TEM of the nanocomposites indicate that substantial improvements in the rheological properties of scCO2 nanocomposites are the result of increased dispersion and polymer−clay interactions. At low frequencies, the elastic plateau modulus of the scCO2-processing nanocomposites (5 wt % clay loading) is more than 40-fold higher than benchmark solution-blended samples. Our results suggest that the substantial contacting with scCO2, followed by rapid depressurization, produces a combination of disorder and dispersion of this “as-received” clay, and the presence of the cosolvent enables more intimate contact of the high molecular weight PS and clay.

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Thermal hazard assessments in process industries often require calorimetry and kinetic modeling. These techniques are illustrated using examples of inhibited 4-vinylbenzyl chloride (VBC) self-polymerization and di-4-methylbenzoyl peroxide (MeBPO) thermal stability. The polymerization kinetics of inhibited VBC were studied using isothermal and non-isothermal calorimetry. A thermokinetic model was developed using calorimetry data and this model was coupled with a heat balance to predict the consequence of a commonly encountered plant scenario, loss of active cooling to a storage tank. Isothermal differential scanning calorimetry (DSC) and microcalorimetry (using a TAM IV microcalorimeter) were also applied to analyze the thermal decomposition of MeBPO desensitized with silicone oil (50% w/w). The thermokinetic parameters and thermal stability were evaluated. MeBPO decomposes in two exothermic reactions, and the total heat of decomposition was determined to be 658.8 J/g of sample. The thermal decomposition of MeBPO was described by a model of two parallel reactions, the first leading to 4,4′dimethylbiphenyl and the second to p-methylbenzyl p-toluate. The results can be applied for emergency relief system design and for emergency rescue strategies during an upset or accident.

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