Elevated occupational exposure to chlorinated phosphate esters at a construction materials manufacturing plant.

BACKGROUND: Numerous studies have documented that the general population is widely exposed to organophosphate esters (OPEs), yet studies on the emissions of OPEs in the industrial application processes and their occupational exposure are scarce. The aim of this study was to assess the exposure to OPEs for workers engaged in OPE-retarded construction material manufacturing plant in China. METHOD: Paired dust samples (12 samples each time) from an OPEs retarded building materials manufacturing plant during the plant uptime and downtime have been analyzed for tris(2-chloroethyl)-phosphate (TCEP), tris(2-chloroisopropyl) phosphate (TCPP), and other commonly used OPEs. Moreover, nine OPEs metabolites (mOPEs) in urine samples (n = 42) from fourteen workers who engaged in this plant were also measured. The daily exposure doses to OPEs were estimated from the measured urinary concentrations of corresponding mOPEs. RESULTS: Thirteen out of fourteen studied OPEs (except for tri-n-propyl phosphate, TnPP) were determined in all dust samples from the manufacturing plant, and TCEP and TCPP were the predominant compounds in dust collected from the plant uptime and downtime. Overall, the occupationally exposed population had significantly higher (p < 0.01) urinary levels of mOPE, especially for bis (2-chloroethyl) phosphate (BCEP), relative to the reference population. Workshop workers who directly involved in the production of OPEs treated products had higher OPEs exposure. Risk assessment revealed that cancer risk (1.5 × 10-6-8.5 × 10-4) for all workers was larger than 1 × 10-6 when levels of mOPEs in urine from workers were used for estimating OPEs exposure, revealing moderate to high potential cancer risk to workers from OPEs exposure. CONCLUSION: To our knowledge, this is the first study reporting emissions of OPEs in OPE-treated products manufacturing processes and the potential exposure of the occupationally exposed population. OPEs, especially for TCEP and TCPP, present at elevated levels and pose moderate to high potential health risks to the exposed workers, emphasizing the importance of strengthening occupational exposure prevention in similar industries.

Investigation of Flame Retardant Flexible Polyurethane Foams Containing DOPO Immobilized Titanium Dioxide Nanoparticles.

In this work, a multi-functional nanoparticle (TiO2-KH570-DOPO) has been successfully synthesized through the attachment of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-methacryloxy propyl trimethoxyl silane on the surface of titanium dioxide (TiO2). Supercritical carbon dioxide was used as the solvent in order to increase the grafting level. The chemical structure of TiO2-KH570-DOPO was fully characterized using Fourier transform infrared spectra, thermogravimetric analysis and transmission electron microscopy. The modified TiO2 was incorporated into flexible polyurethane foam (FPUF). The fire performance of FPUF blends was evaluated using microscale combustion calorimetry. Peak heat release rate and total heat release values were reduced from 657.0 W/g and 28.9 kJ/g for neat FPUF sample to 519.2 W/g and 26.8 kJ/g of FPUF specimen containing 10 wt % of TiO2-KH570-DOPO. Analysis of thermal stability and the observation of char formation suggests that TiO2-KH570-DOPO is active in the condensed phase.

A New Bioactive Polylactide-based Composite with High Mechanical Strength.

A new bioresorbable polylactide/calcium phosphate composite with improved mechanical strengths and a more basic filler, tetracalcium phosphate (TTCP), was prepared by melt compounding. N-(2-aminoethyl)-3-aminoproplytrimethoxysilane (AEAPS) and pyromellitic dianhydride (PMDA) were used to improve the interfacial adhesion between TTCP and polylactide (PLA). While AEAPS improved the dispersion of TTCP in the matrix, PMDA might react with the terminal hydroxyl group of PLA and the amino group on the surface of AEAPS modified TTCP, which could further enhance the interfacial strength. The tensile strength was improved to 68.4 MPa for the PLA/TTCP-AEAPS composite from 51.5 MPa for the PLA/TTCP composite (20 wt% of TTCP). Dynamic mechanical analysis suggested that there was a 51 % improvement in storage modulus compared to that of PLA alone, when PMDA (0.2 wt% of PMDA) was incorporated into the PLA/TTCP-AEAPS composite (5 wt% of TTCP). Using this new bioresorbable PLA composite incorporated with a more basic filler for biomedical application, the inflammation and allergic effect resulted from the degraded acidic product are expected to be reduced.

A Polycarbonate/Magnesium Oxide Nanocomposite with High Flame Retardancy.

A new flame retardant polycarbonate/magnesium oxide (PC/MgO) nanocomposite, with high flame retardancy was developed by melt compounding. The effect of MgO to the flame retardancy, thermal property, and thermal degradation kinetics were investigated. Limited oxygen index (LOI) test revealed that a little amount of MgO (2 wt %) led to significant enhancement (LOI = 36.8) in flame retardancy. Thermogravimetric analysis results demonstrated that the onset temperature of degradation and temperature of maximum degradation rate decreased in both air and N2 atmosphere. Apparent activation energy was estimated via Flynn-Wall-Ozawa method. Three steps in the thermal degradation kinetics were observed after incorporation of MgO into the matrix and the additive raised activation energies of the composite in the full range except the initial stage. It was interpreted that the flame retardancy of PC was influenced by MgO through the following two aspects: on the one hand, MgO catalyzed the thermal-oxidative degradation and accelerated a thermal protection/mass loss barrier at burning surface; on the other hand, the filler decreased activation energies in the initial step and improved thermal stability in the final period.

Improvement of thermal stability of polypropylene using DOPO-immobilized silica nanoparticles.

After the surface silylation with 3-methacryloxypropyltrimethoxysilane, silica nanoparticles were further modified by 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO). The immobilization of DOPO on silica nanoparticles was confirmed by Fourier transform infrared spectroscopy, UV-visible spectroscopy, magic angle spinning nuclear magnetic resonance, and thermogravimetric analysis. By incorporating the DOPO-immobilized silica nanoparticles (5 wt%) into polypropylene matrix, the thermal oxidative stability exhibited an improvement of 62 °C for the half weight loss temperature, while that was only 26 °C increment with incorporation of virgin silica nanoparticles (5 wt%). Apparent activation energies of the polymer nanocomposites were estimated via Flynn-Wall-Ozawa method. It was found that the incorporation of DOPO-immobilized silica nanoparticles improved activation energies of the degradation reaction. Based on the results, it was speculated that DOPO-immobilized silica nanoparticles could inhibit the degradation of polypropylene and catalyze the formation of carbonaceous char on the surface. Thus, thermal stability was significantly improved.

Improve the Strength of PLA/HA Composite Through the Use of Surface Initiated Polymerization and Phosphonic Acid Coupling Agent.

Bioresorbable composite made from degradable polymers, e.g., polylactide (PLA), and bioactive calcium phosphates, e.g., hydroxyapatite (HA), are clinically desirable for bone fixation, repair and tissue engineering because they do not need to be removed by surgery after the bone heals. However, preparation of PLA/HA composite from non-modified HA usually results in mechanical strength reductions due to a weak interface between PLA and HA. In this study, a calcium-phosphate/phosphonate hybrid shell was developed to introduce a greater amount of reactive hydroxyl groups onto the HA particles. Then, PLA was successfully grafted on HA by surface-initiated polymerization through the non-ionic surface hydroxyl groups. Thermogravimetric analysis indiated that the amount of grafted PLA on HA can be up to 7 %, which is about 50 % greater than that from the literature. PLA grafted HA shows significantly different pH dependent ζ-potential and particle size profiles from those of uncoated HA. By combining the phosphonic acid coupling agent and surface initiated polymerization, PLA could directly link to HA through covalent bond so that the interfacial interaction in the PLA/HA composite can be significantly improved. The diametral tensile strength of PLA/HA composite prepared from PLA-grafted HA was found to be over twice that of the composite prepared from the non-modified HA. Moreover, the tensile strength of the improved composite was 23 % higher than that of PLA alone. By varying additional variables, this approach has the potential to produce bioresorbable composites with improved mechanical properties that are in the range of natural bones, and can have wide applications for bone fixation and repair in load-bearing areas.