Toxicological risk assessment of bisphenol a released from dialyzers under simulated-use and exaggerated extraction conditions.

Bisphenol A (BPA) belongs to a group of chemicals used in the production of polycarbonate, polysulfone, and polyethersulfone which are used, among other applications, in the manufacture of dialyzers. While exposure to BPA is widespread in the general population, dialysis patients represent a population with potentially chronic parenteral BPA exposures. To assess the potential risk of BPA exposure to dialysis patients through dialyzer use, exposure estimates were calculated based on BPA levels measured by ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry following extractions from dialyzers manufactured by Fresenius Medical Care. Extraction conditions included both simulated-use leaching and exaggerated extractions to evaluate possible leachable and extractable BPA, respectively, from the devices. The mean BPA concentrations were 3.6 and 108.9 ppb from simulated-use and exaggerated extractions, respectively, from polycarbonate-containing dialyzers. No BPA was detected from polypropylene-containing dialyzers. Margins of Safety (MOS) were calculated to evaluate the level of risk to patients from estimated BPA exposure from the dialyzers, and the resulting MOS were 229 and 45 for simulated-use and exaggerated extractions, respectively. The findings suggest that there is an acceptable level of toxicological risk to dialysis patients exposed to BPA from use of the dialyzers tested in the current study.

Microwave-assisted surface modification for the separation of polycarbonate from polymethylmethacrylate and polyvinyl chloride waste plastics by flotation.

Microwave-assisted potassium permanganate modification (MPPM) was used for the flotation separation of polycarbonate (PC) from polyvinyl chloride (PVC) and polymethylmethacrylate (PMMA) waste plastics. The separation process was optimized by investigating the potassium permanganate concentration, treatment time, flotation time and frother concentration. MPPM selectively reduced the flotation recovery of PC. The optimum conditions were determined to be: potassium permanganate concentration, 2 mM/L; treatment time, 1 min; frother concentration, 17.57 g/L; and flotation time, 1 min. PC was efficiently separated from PVC and PMMA under the optimum conditions. The purity of the separated PC was 97.71%. The purity and recovery of PVC and PMMA were both >95%. The modification mechanism was investigated using the water contact angles, Fourier transform infrared spectrometry and scanning electron microscopy. This work provides technical insights into the industrial recycling of waste plastics.

UHPLC-high-resolution mass spectrometry determination of bisphenol A and plastic additives released by polycarbonate tableware: influence of ageing and surface damage.

A new UHPLC-ESI-Orbitrap method for the identification and the quantitative determination of bisphenol A and some common additives employed in plastic manufacturing has been developed and validated. The method has been applied to evaluate the migration from 14 samples of tableware of different age and degree of surface damage, in both ethanol and isooctane (used as food simulants according to EU plastic regulation). Bisphenol A, three UV light absorbers, and one whitening agent were detected and quantified. Data were analyzed with the aim of exploring a possible correlation between bisphenol A and additives release, ageing, and surface integrity. A high correlation between age of samples, surface damage, and bisphenol A migration has been evaluated, while the release of additives was not correlated with other parameters. Obtained data showed for the first time that the release of bisphenol A seems to be more connected to ageing than to scratches and cracks occurrence. Graphical Abstract Bisphenol A and additives released by polycarbonate tableware: influence of ageing and surface damage.

Retrieval analysis of a polycarbonate-urethane acetabular cup: a case report.

An acetabular cup made of a compliant polycarbonate-urethane material has been introduced as an alternative bearing solution. This case study examines the use of this acetabular cup in a single patient at 12 months. The cup had minimal loss of thickness with the most being in the superior area (approximately 10%) and minimal loss of weight (2.4%). On the back side was evidence of abrasive macroscopic wear on one side of the implanted component in the area of directional loading from the head to the acetabulum. On the front side, the wear rate was determined to be minimal (less than 15 mm3 per year), meaning that most of the change in thickness and weight was caused on the back side. The retrieved synovial fluid appeared normal in color and volume at the time of revision. The histology of the tissue taken showed minimal wear particles and minimal reactivity, confirming that the patient did not have any signs of synovitis.The analysis of the cup confirms the preclinically determined low wear articulation and biocompatibility of polycarbonate-urethane as a weight-bearing material. In summary, the surgical findings, data reviewed, and images taken from this case report warrant further study.

Explantation and analysis of the first retrieved human acetabular cup made of polycarbonate urethane: a case report.

This report describes the first human retrieval of a polycarbonate-urethane (PCU) acetabular cup implanted for 10.5 months that was revised for pain of unknown origin. By using a micro-CT analysis, the articulating surface was determined to have a wear rate of less than 1.4 mm3 per year. An analysis of the synovial fluid retrieved at the time of revision found an average particle size of 1 mum diameter. Overall, the surgical findings and analysis were consistent with the results observed in laboratory and animal studies. The histology and synovial fluid analysis found sparse evidence of particulate debris and no synovitis, indicating the potential of this articulating material for use as a bearing surface.

Use of laser-induced breakdown spectroscopy for the determination of polycarbonate (PC) and acrylonitrile-butadiene-styrene (ABS) concentrations in PC/ABS plastics from e-waste.

Due to the continual increase in waste generated from electronic devices, the management of plastics, which represents between 10 and 30% by weight of waste electrical and electronic equipment (WEEE or e-waste), becomes indispensable in terms of environmental and economic impacts. Considering the importance of acrylonitrile-butadiene-styrene (ABS), polycarbonate (PC), and their blends in the electronics and other industries, this study presents a new application of laser-induced breakdown spectroscopy (LIBS) for the fast and direct determination of PC and ABS concentrations in blends of these plastics obtained from samples of e-waste. From the LIBS spectra acquired for the PC/ABS blend, multivariate calibration models were built using partial least squares (PLS) regression. In general, it was possible to infer that the relative errors between the theoretical or reference and predicted values for the spiked samples were lower than 10%.

Ammonia modification for flotation separation of polycarbonate and polystyrene waste plastics.

A promising method, ammonia modification, was developed for flotation separation of polycarbonate (PC) and polystyrene (PS) waste plastics. Ammonia modification has little effect on flotation behavior of PS, while it changes significantly that of PC. The PC recovery in the floated product drops from 100% to 3.17% when modification time is 13min and then rises to 100% after longer modification. The mechanism of ammonia modification was studied by contact angle, and Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) measurements. Contact angle of PC indicates the decline of PC recovery in the floated product is ascribed to an increase in surface wettability. FT-IR and XPS spectra suggest that ammonia modification causes chemical reactions occurred on PC surface. Flotation behavior of ammonia-modified PC and PS was investigated with respect to flotation time, frother concentration and particle sizes. Flotation separation of PC and PS waste plastics was conducted based on the flotation behavior of single plastic. PC and PS mixtures with different particle sizes are separated efficiently, implying that the technology possesses superior applicability to particle sizes of plastics. The purity of PS and PC is up to 99.53% and 98.21%, respectively, and the recovery of PS and PC is larger than 92.06%. A reliable, cheap and effective process is proposed for separation of PC and PS waste plastics.

Investigation on an innovative technology for wet separation of plastic wastes.

This paper presents an original device for the separation of plastic polymers from mixtures. Due to the combination of a characteristic flow pattern developing within the apparatus and density, shape and size differences among two or more polymers, this device allows their separation into two products, one collected within the instrument and the other one expelled through its outlet ducts. Experimental tests have been conducted to investigate the effectiveness of the apparatus, using two geometric arrangements, nine hydraulic configurations and three selections of polymers at three stages of a material life cycle. Tests with samples composed of a single typology of polymer have been used to understand the interaction between the particles and the carrying fluid within the apparatus in different hydraulic configurations and geometric arrangements. Multi-material tests are essential to simulate the real conditions in an industrial recycling plant. The separation results have been evaluated in terms of grade and recovery of a useful material. Under the proper hydraulic configurations, the experimentation showed that it is possible to produce an almost pure concentrate of Polyethylene Terephthalate (PET) from a mixture of 85% PET and 15% Polycarbonate (PC) (concentrate grade and recovery equal to 99.5% and 95.1%) and a mixture of 85% PET and 15% Polyvinyl Chloride (PVC) (concentrate grade and recovery equal to 97.9% and 100.0%). It is further demonstrated that almost pure concentrates of PVC and PC can be produced from a mixture of 85% PVC and 15% PC (PVC grade and recovery equal to 99.9% and 99.7%) and a mixture of 85% PC and 15% PVC (PC grade and recovery equal to 99.0% and 99.5%).

The human macrophage response during differentiation and biodegradation on polycarbonate-based polyurethanes: dependence on hard segment chemistry.

Human monocytes, isolated from whole blood, were seeded onto tissue culture grade polystyrene (PS) and three polycarbonate-based polyurethanes (PCNUs) (synthesized with either 1,6-hexane diisocyanate (HDI) or 4,4'-methylene bis-phenyl diisocyanate (MDI), poly(1,6-hexyl 1,2-ethyl carbonate) diol (PCN) and 1,4-butanediol (BD) in different stoichiometric ratios (HDI:PCN:BD 4:3:1 or 3:2:1 and MDI:PCN:BD 3:2:1) (referred to as HDI431, HDI321 and MDI321, respectively). Following their differentiation to monocyte-derived macrophages (MDMs) the cells were trypsinized and reseeded onto each of the PCNUs synthesized with either 14C-HDI or 14C-BD and degradation was measured by radiolabel release (RR). When the differentiation surface was MDI321, there was more RR from 14C-HDI431 than from any other surface (p < 0.0001) whereas the amount of esterase (identified by immunoblotting) as well as the esterase activity was the greatest in MDM differentiated on PS, reseeded on 14C-HDI431 (p < 0.0001). The effect of potential degradation products (methylene dianiline (MDA) and BD) from the PCNUs was carried out to determine possible links between products and substrate-induced activation of MDM. MDA was found to inhibit RR 60% from MDM seeded on 14C-MDI321B (p < 0.0001), approximately 20% from 14C-HDI431 (p = 0.002) and no effect from 14C-HDI321B. MDA inhibited esterase activity 30% from MDM only on 14C-MDI321B (p = 0.003), but no effect on esterase activity was observed for the other two polymers. BD had no inhibitory effect on RR from any PCNU, but did inhibit esterase activity in MDM on 14C-HDI431 (p = 0.025). This study indicates that the degradation of a specific material is a multi-factorial process, dictated by its susceptibility to hydrolysis, the effect of specific products generated during this course of action, and perhaps not as well appreciated, the material's inherent ability to influence enzyme synthesis and release.

[Simultaneous determination of total specific migration limit of seven benzene polycarbonic acids and their derivatives in food simulants by high performance liquid chromatography-ultraviolet detection].

A novel method for simultaneous determination of total specific migration limits (SML (T)) of trimellitic, isophthalic, terephthalic, phthalic acid and their derivatives (1, 2, 4-benzenetricarboxylic anhydride, isophthaloyl chloride and terephthaloyl chloride) in food simulants (10% (v/v) ethanol, 20% (v/v) ethanol, 50% (v/v) ethanol, 3% (w/v) acetic acid and olive oil) was developed by high performance liquid chromatography-ultraviolet detection (HPLC-UV). After the migration test, the soaking solution was cooled down and vortexed. After the extraction of olive oil food simulants with 0. 1% (w/v) ammonium acetate aqueous solution, the clear aqueous solution or other aqueous food simulants was filtered through a hydrophilic polytetrafluoroethylene filter with a disposable syringe before injection. The Synergi Polar-RP column (250 mm x 4.6 mm, 4 µm) and gradient elution mode were selected. The variable wavelength detector was set at 232 nm. The limits of quantification were 0.1-0.2 mg/kg; the linearity of the method was good with r2 > 0.999 91 over the range from 0.5 to 12 mg/L for aqueous food simulants or 0.5 to 12 mg/kg for olive oil food simulants. The recoveries of them were between 94. 3% and 105% with the relative standard deviations between 0.1% and 2.3% at the levels of 1.25, 2.50, 6.25 mg/kg. The method shows the low limits of detection, good recoveries and accuracies, and meets the requirement of ( EU) No 10/2011 regulation for the total specific migration limits of trimellitic, isophthalic, terephthalic, phthalic acids and their derivatives. The method has been applied to the analysis of food contact material samples.

Dental polyelectrolyte cements. I. Chemistry of the early stages of the setting reaction.

As part of an investigation of the setting of dental polyelectrolyte cements, the chemistry of a selection of glass ionomer and zinc polycarboxylate cements was studied by pH, conductivity and I.R. measurements. The zinc polycarboxylate cements were found to react at a greater rate than the glass ionomer cements. The effect of reducing the powder/liquid (P/L) ratio is to decrease the surface area available to attack and hence the reaction rate. The basic form of the kinetics appears to be unaffected except for low P/L ratios where there is a deficiency of available metal cations.

Dynamic mechanical thermal analysis of dental polymers. II. Bis-phenol A-related resins.

Dynamic mechanical analysis of bis-phenol A-related resins for dental usage provided loss tangent maxima at their transitions and an Arrhenius-type dependence of transition temperature and frequency. A constant maximum in the loss tangent curves, over the frequency range for the unfilled resins below their glass transition temperature, was thought to be caused by their high degree of unsaturation. The calculated activation energies showed the polycarbonate denture base resin required considerably greater energy for segmental motion than the other tested materials. In contrast, the ethylene imine-based temporary crown and bridge material exhibited the lowest activation energy.

Glass-ionomer cement formulations. II. The synthesis of novel polycarobxylic acids.

The synthesis of many polycarboxylic acids is reported. An account is given of their stability in aqueous solution and the properties of cements formed by their reaction with ion-leachable glasses. A copolymer of acrylic and itaconic acids was found to combine several favorable characteristics.

The hydration of dental cements.

A study was made of the hydration of dental cements, water being classified as "non-evaporable" and "evaporable". The ratio of these two types of water was found to vary greatly among different cement types, being lesser in zinc oxide and ionic polymer cements and greater in ion-leachable glass and phosphoric acid cements. The cement with the least "non-evaporable" water, i.e., showing least hydration (the zinc polycarboxylate cement), had the lowest strength and modulus and the greatest deformation at failure. A linear relationship was found to exist between strength and the degree of hydration of dental cements. All the cements were found to become more highly hydrated and stronger as they aged.

Dielectric properties of glass ionomer cements--further studies.

Two recent proprietary glass ionomer cements showed that in the early stages of set the changes in relative permittivity (dielectric constant) and resistivity were rapid. However, when set, measurements indicated that the cements were highly ionic and polar and behaved similarly to the glass ionomer cements previously reported.

Reinforced polycarboxylate cements.

Mechanical properties of polycarboxylate cements are greatly improved by incorporation of high modulus fibers such as potassium titanate into acrylic-itaconic acid and acrylic-itaconic-acronitic acid copolymers. Other desirable properties of the cements are not changed by the addition of fibers.

Confocal Raman microspectrometry: a vectorial electromagnetic treatment of the light focused and collected through a planar interface and its application to the study of a thin coating.

In-depth confocal Raman microspectrometry (CRM) studies through a planar interface between materials of mismatched refraction indices are known to be affected by a decrease of both the collected Raman intensity and the axial resolution as a function of the penetration depth. Following a previous model, which takes the refraction, diffraction, and spherical aberration effects into account when focusing a Gaussian incident laser beam with a high numerical aperture objective lens, a complete vectorial treatment of these phenomena is considered. It is demonstrated that off-axis refraction effects cannot be neglected and that the dimension of the confocal pinhole aperture plays a crucial role on the effective focal plane position and on the collection efficiency. We thus propose a more rigorous and complete approach to the problem, and we find a very good agreement between experimental and theoretical Raman intensity variations for a thick polyethylene sample as a function of the penetration depth. As compared with calculations where only refraction was considered, we confirm that the lengthening of the focus even for a large penetration depth is significantly reduced upon diffraction effects. As an illustrative example, the theoretical Raman responses for a thin coating of approximately 20 microns on a polymer substrate were investigated and compared to experimental results already published. Even though the interfacial region is spread over approximately 5-6 microns when using a 100x objective and a confocal pinhole of 200 microns diameter, it is definitively concluded that the apparent axial resolution is not drastically deteriorated with increasing depth and that the coating thickness may be directly estimated with a precision of approximately 1.0 micron (5%).

Oral sustained-release drug delivery systems using polycarbonate microspheres capable of floating on the gastric fluid.

Polycarbonate microspheres loaded with aspirin, griseofulvin and p-nitroaniline were prepared by a solvent evaporation technique. High drug loading (> 50%) was achieved by this process. Drug-loaded microspheres were found to float on simulated gastric fluid and intestinal fluid. Drug-release studies were carried out in these fluids at 37 degrees C. Increasing the drug to polymer ratio in the microspheres increased both their mean particle size and the release rate of the drugs. It was concluded that sustained delivery of drugs could be effected using this matrix.

Development of emission factors for polycarbonate processing.

Emission factors for selected volatile organic compounds (VOCs) and particulate emissions were developed while processing eight commercial grades of polycarbonate (PC) and one grade of a PC/acrylonitrile-butadiene-styrene (ABS) blend. A small commercial-type extruder was used, and the extrusion temperature was held constant at 304 degrees C. An emission factor was calculated for each substance measured and is reported as pounds released to the atmosphere/million pounds of polymer resin processed [ppm (wt/wt)]. Scaled to production volumes, these emission factors can be used by processors to estimate emission quantities from similar PC processing operations.

Cements for permanent luting: a summarizing review.

Three cement systems are favored for permanent luting of cast restorations. These include zinc phosphate, reinforced zinc oxide-eugenol, and polycarboxylate cements. Although others have been used in the past and new luting media are anticipated for the future, the status of currently used cement for luting is based mainly on the results of laboratory research and on clinical experience. Zinc phosphate cement, with an impressive 100-year history, currently holds the advantage. Future comprehensive clinical studies, correlated with results of physical and biological testing, may eventually direct the clinican's preference to another, newer material. It is hoped that properties and strength values that are clinically significant also will be identified, so that laboratory tests can be more predictive of clinical success.