Empirical correlations for diffusivity and the partition coefficient for phthalates in PVC materials and modelling emissions of automotive sealants.

Polyvinylchloride (PVC) based sealants commonly contain phthalate plasticizers that are emitted into the air over time. The low volatility classifies them as Semi-Volatile Organic Compounds (SVOCs). Empirical relationships are determined for estimation of the diffusion and solid/air partition coefficients for phthalates in PVC materials using data compiled from studies of phthalates in other PVC materials, such as vinyl flooring. The relationships are functions of vapor pressure of the compounds, which are determined from a Clausius-Clapeyron equation. A test chamber was constructed to continuously sample the air and measure the air concentration based on a Solid Phase MicroExtraction (SPME) method. The partition coefficient was tested with dioctyl terephthalate (DOTP) in a PVC-based sealant, in which the results fell within the reasonable error of the value predicted from the empirical relationship. The model is applied to outdoor and manufacturing scenarios to evaluate the effect of temperature and mass transfer coefficient.

Reduced Graphene Oxide on Nickel Foam for Supercapacitor Electrodes.

The focus of this paper is the investigation of reduced graphene oxide (GO)/nickel foam (RGON) samples for use as supercapacitor electrodes. Nickel foam samples were soaked in a GO suspension and dried before being subjected to two different methods to remove oxygen. Atmospheric pressure annealed (APA) samples were treated with a varying number (10-18) of nitrogen plasma jet scans, where sample temperatures did not exceed 280 °C. Furnace annealed (FA) samples were processed in an atmosphere of hydrogen and argon, at temperatures ranging from 600 °C to 900 °C. Environmental Scanning Electron Microscope (ESEM) data indicated that the carbon to oxygen (C:O) ratio for APA samples was minimized at an intermediate number of plasma scans. Fourier Transform Infrared Spectroscopic (FTIR) and Raman spectroscopic data supported this finding. ESEM analysis from FA samples showed that with increasing temperatures of annealing, GO is transformed to reduced graphene oxide (RGO), with C:O ratios exceeding 35:1. X-ray Photoelectron Spectroscopy (XPS) and X-ray diffraction (XRD) data indicated the formation of RGO with an increasing annealing temperature until 800 °C, when oxygen reincorporation in the surface atomic layers becomes an issue. Supercapacitors, constructed using the FA samples, demonstrated performances that correlated with surface atomic layer optimization of the C:O ratio.