Phthalate migration and its effects on poly(vinyl chloride)-based footwear: pathways, influence of environmental conditions, and the possibility of human exposure

The study of phthalate migration in footwear is important from an environmental viewpoint and the consumer health perspective as it remains in direct contact with the user for a long time. In this research article, the migration of phthalate, specifically di-(2-ethylhexyl) phthalate (DEHP), from the poly(vinyl chloride) (PVC) shoe sole to the attached leather insole has been studied for six months under different environmental conditions. After one month, the DEHP concentration in the PVC sole decreased by 45-58%, and that in the leather insole increased from 0.35 mg g^-1 to 38-58 mg g^-1. After six months, about 90% of the DEHP has been lost from the PVC sole, and that in the leather insole reached close to its initial value (value before the experiment). The migration rate depends on the environmental conditions and the presence of phthalate soluble solvents in the sole-adhesive-insole system of the footwear. The influence of DEHP migration on the physicochemical characteristics of the PVC sole and leather insole has been studied by Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR), thermo-gravimetric analysis (TGA), and differential scanning calorimetry (DSC). The migration and emission pathways of DEHP, the influence of environmental conditions, and the possibility of human exposure to phthalate through footwear are discussed.

High-performance silica nanoparticle reinforced poly (vinyl alcohol) as templates for bioactive nanocomposites

Silica nanoparticle reinforced poly (vinyl alcohol) cast sheets 40 μm thick were tested for mechanical and biological properties. The films were characterized using X-ray diffraction, scanning electron microscopy, and infrared spectroscopy. The crystallinity decreased with increased silica content. Changes in the morphology and structure upon the addition of silica suggest the formation of cross-linking. The modulus increased from 300 MPa for PVA to 7.2 GPa for 120 wt.% silica nanoparticle in the blend and the tensile strength increased from 3.5 MPa to 35 MPa. The modulus estimated using dynamic tests, tensile tests, and nanoindentation was comparable and was predicted well using the Halpin-Tsai's equation. The nanocomposites were an order of magnitude tougher than the pure polymer. Silica based nanocomposite was also found to be an excellent template for the deposition of calcium hydroxyapatite when immersed in simulated body fluid. The modulus and tensile strength of apatite coated silica nanoparticle (120 wt.%)-PVA composite increased to 11 GPa and 65 MPa respectively, close to that of cortical bone. The results represent one of the largest increases in mechanical properties of nanocomposite mimicking the properties of human bone. The addition of silica can also aid in osseointegration.

Novel thermally stable poly(vinyl chloride) composites for sulfate removal

BaCO(3) dispersed PVC composites were prepared through a polymer re-precipitation method. The composites were tested for sulfate removal using rapid small scale column test (RSSCT) and found to significantly reduce sulfate concentration. The method was extended to synthesize barium carbonate-loaded silica aero-gels-polyvinyl chloride (PVC) polymer composites. The PVC composites were characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray mapping, X-ray diffraction (XRD), thermogravimetric analysis (TGA) and inductively coupled plasma mass spectrometry (ICP-MS) analysis. The method has advantages over conventional sulfate precipitation (sulfate removal process) using BaCO(3) wherein clogging of the filter can be avoided. The method is environmentally friendly and does not interfere with natural organic matter as the conventional resin does. Some of the composites were thermally more stable as compared with the pure PVC discussed in the literature.