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Crystalline–amorphous diblock copolymers (BCPs) comprising crystalline blocks of isotactic polypropylene (iPP) or polyethylene (PE) linked to amorphous blocks of random ethylene–propylene copolymers (EPR) (iPP-b-EPR and PE-b-EPR) of different block lengths and ethylene concentrations in EPR blocks, and crystalline–crystalline BCPs composed by iPP and PE blocks (iPP-b-PE) have been synthesized with different living catalysts. The effects of the presence of a linked EPR rubbery block of varying composition on the crystallization behaviors and kinetics of PE and iPP, and of crystalline PE or iPP block on the crystallization kinetics of linked iPP or PE, respectively, have been analyzed. All samples have been isothermally crystallized from melting at different temperatures, and the crystallization kinetics have been analyzed. In iPP-b-PE BCPs, the PE block crystallizes first from the melt during nonisothermal cooling or isothermal crystallization. The iPP block crystallizes after PE and nucleates over the PE crystals. In both iPP-b-EPR and PE-b-EPR BCPs, the linked amorphous EPR block slows down the crystallization of iPP and PE blocks with respect to their respective homopolymers. Furthermore, in iPP-b-EPR samples, a higher concentration of propylene in the EPR phase results in a more significant slowdown of the crystallization kinetics of iPP due to a higher solubility between the blocks. Analogously, in PE-b-EPR copolymers, the increase in the length of the EPR block results in a more pronounced slowdown of the crystallization rate of PE with respect to the PE homopolymer due to the significant dilution exerted by the long EPR block. All samples of iPP-b-PE copolymers show crystallization rates lower than that of the PE homopolymer but faster than that of the iPP homopolymer. In isothermal crystallization experiments, the iPP blocks do not crystallize, not even at low crystallization temperatures, but crystallize upon successive cooling, nucleating over the PE crystals formed in the isothermal step. Therefore, the linked iPP, which remains in the melt during the isothermal crystallization, slows down the crystallization kinetics of PE, in contrast to what happens in a sample of iPP/PE blend, where the crystallization kinetics of PE is not affected by the presence of the phase-separated iPP.

The memory of crystals in the melt of stereodefective samples of isotactic polypropylene (iPP), characterized by different concentrations of rrstereodefects from 0.49 to 10.5 mol %, was analyzed. Experiments of self-nucleation and annealing have demonstrated that high contents of rrstereodefects, largely incorporated in the crystals of iPP, produce a significant memory of crystals in the melt that persists up to high temperatures well above the melting temperature. For low stereodefect concentrations (lower than 2–3 mol %), the memory of the crystals is erased at temperatures (Ts,DI-DII) only few degrees above the end of the melting endotherm (Tm,end), whereas for contents of rrdefects higher than 3–4 mol %, the memory of crystals persists even upon heating at temperatures much above the end of the endothermic signal. The width of the heterogeneous melt Domain II, in terms of range of temperatures in the melt in which the memory exists and self-nucleation takes place, and the difference between the temperature at which the isotropic melt begins Ts,DI-DIIand the end of the melting endotherm Tm,endincrease with the increase of defects concentration. The higher the amount of stereodefects and the lower the melting temperature of iPP, the higher the temperature at which the self-nuclei must be heated to cancel the memory of crystals. These results indicate that a significant memory of iPP crystals exists in the melt not only in copolymers of iPP with noncrystallizable comonomeric units but also for iPPs containing small defects largely incorporated in the crystals. During crystallization of these stereodefective iPPs, the selection of the crystallizable segments of suitable length, which has been considered responsible for the formation of the heterogeneous melt and self-nuclei, should be less demanding thanks to the incorporation of stereodefects in the crystallizable sequences. However, upon successive heating to melt at low temperatures these highly irregular produced crystals, the diffusion and homogenization of all long and short sequences is in any case not easy, also considering the low temperature, and portions of partitioned sequences are left in the melt acting as efficient self-nuclei upon cooling and crystallization from the melt. The melt-memory attributed to these self-nuclei and the process of self-nucleation induce crystallization of the γ form, while crystallization from the isotropic melt induces crystallization of the α form, also in the case of samples with high concentrations of stereodefects that should crystallize in the γ form.

Samples of block copolymers (BCP) constituted by semicrystalline blocks of linear low-density polyethylene (LLDPE) and isotactic polypropylene (iPP) of different block lengths (iPP-b-LLDPE) have been prepared by living polymerization using the hafnium-based catalyst that provides high steric control and isotactic propagation of propene units. The LLDPE blocks are random ethylene/1-octene copolymers with 1-octene concentrations between 1 and 3 mol %. The crystallization behavior and the morphologies in the melt and after the crystallization of iPP-b-LLDPE are presented. The iPP block melts at 135 °C, according to the moderate isotacticty, whereas the LLDPE blocks melt at lower temperatures, between 101 and 113 °C, depending on the 1-octene concentration. Both blocks crystallize from the melt and wide-angle diffraction and small-angle scattering profiles acquired with synchrotron radiation during cooling have demonstrated that the iPP block crystallizes first upon cooling, except for the sample with the lowest iPP molecular mass, for which PE and iPP crystallize almost simultaneously. The small-angle scattering recorded during cooling and crystallization of iPP and LLDPE blocks shows the emergence of a single broad scattering peak ascribed to the formation of stacks of crystalline lamellae of indistinguishable iPP and LLDPE with values of the long period of 13–14 nm. Electron microscopy (TEM) analysis allowed us to image the microphase-separated microdomain structure present in the melt and frozen or preserved at room temperature after crystallization. The TEM analysis has demonstrated that phase-separation of the dissimilar blocks occurs in the melt. The formed microdomain structure is preserved after crystallization of both blocks, and pass-through crystallization occurs with iPP and PE lamellae crossing through the different microdomains without overwhelming the microphase-separated structure.

Stereoselective propene polymerization mechanisms promoted by C1-symmetric transition metal (TM) catalysts with nonmetallocene and ansa-metallocene ligands have been revisited by density functional theory (DFT) calculations combined with a molecular descriptor for steric analysis (%VBur) and a state-of-the-art interpretative tool based on the Activation Strain Model (ASM) and a Natural Energy Decomposition Analysis (NEDA). While DFT results suggested a close similarity for mechanisms and stereoselectivities for these catalyst classes, the ASM-NEDA analysis unraveled that different stereoelectronic effects play the dominant role depending on the ligand framework. The insights achieved by such analysis on the “naked” cationic active species were also confirmed by adding the counterion in the calculations, thus allowing a better understanding of olefin polymerization mechanism(s) governed by TM catalysts.

A combined monitoring and dispersion modelling methodology was applied for assessing air quality at three different levels of proximity to the selected service station: (I) next to the fuel pumps, (II) in the surrounding environment, and (III) in the background. Continuous monitoring and passive sampling were used for achieving high temporal and spatial resolution, respectively. A Gaussian dispersion model (CALINE4) was used for assessing the road traffic contribution to the local concentrations under different meteorological conditions.

Abstract: There is a lack of data for health risk assessment of long term personal exposure to certain ubiquitous air pollutants present particularly in urban atmospheres. The relationship between ambient background concentrations and personal exposure is often unknown. A pilot campaign to measure indoor concentrations, outdoor concentrations and personal exposure to benzene, formaldehyde and acetaldehyde was conducted in a medium sized French town. A strong contribution to total personal exposure was observed from indoor sources, especially for formaldehyde and acetaldehyde, suggesting that indoor sources are dominant for these compounds. For benzene, the average personal exposure exceeded a 10 μgm−3 limit value, although this was not the case for the ambient background concentration. For formaldehyde, the limit level was also exceeded. Observations suggest that true personal exposure cannot be determined directly from measurements pertaining from fixed ambient background monitoring stations. It is hoped that this will be taken into consideration by the bodies responsible for monitoring air pollution and the future European Air Quality Directive.

Summary The exposure of workers to methylene chloride and phenol in an aeronautical workshop was measured during stripping of paint from a Boeing B 747. Methylene chloride exposure was measured during two work days by personal air sampling, while area sampling was used for phenol. During paint stripping operations, methylene chloride air concentrations ranged from 299.2 mg/m3 (83.1 ppm) to 1888.9 mg/m3 (524.7 ppm). The exposures to methylene chloride calculated for an 8-h work day ranged from 86 mg/m3 (23.9 ppm) to 1239.5 mg/m3 (344.3 ppm). In another aeronautical workshop, exposure to organic solvents, especially ethylene glycol monoethyl-ether acetate (EGEEA), was controlled during the painting of an Airbus A 320. The external exposure to solvents and EGEEA was measured by means of individual air sampling. The estimation of internal exposure to EGEEA was made by measuring its urinary metabolite, ethoxyacetic acid (EAA). Both measurements were made during the course of 3 days. The biological samples were taken pre-and post-shift. During painting operations, methyl ethyl ketone, ethyl acetate, n-butyl alcohol, methyl isobutyl ketone, toluene, n-butyl acetate, ethylbenzene, xylenes and EGEEA were detected in working atmospheres. For these solvents, air concentrations ranged from 0.1 ppm to 69.1 ppm. EGEEA concentrations ranged from 29.2 mg/m3 (5.4 ppm) to 150.1 mg/m3 (27.8 ppm). For biological samples, the average concentrations of EAA were 108.4 mg/g creatinine in pre-shift and 139.4 mg/g creatinine in post-shift samples. Despite the fact that workers wore protective respiratory equipment during paint spraying operations, EEA urinary concentrations are high and suggest that percutaneous uptake is the main route of exposure for EGEEA. The introduction of new paint stripping processes in the aeronautical industry could help to reduce future exposure to methylene chloride.

The health risk assessment paradigm is progressively being included in the French regulatory process. In this context, the French Ministry of Environment asked INERIS to assess the health risks incurred by populations living in the vicinity of industrial sites. This study gives the results of the risk assessment carried out on populations living nearby synthetic rubber's manufacturers which have among the most polluting activities concerning 1,3-butadiene and concomitant pollutants. To achieve this target, a bibliographical synthesis was first done to identify the different types of industrial sites releasing 1,3-butadiene. As a result, a national inventory was set up. The pollutants toxicity was also studied as well as the dose-response relationships for the most relevant effects (i.e. for butadiene: carcinogenic, reproduction and developmental effects) and the main way of exposure (inhalation). Preliminary exposure results focused on butadiene and gave an estimate of its concentrations in the air around synthetic rubber's manufacturers using factories production capacities as a proxy according to the European calculation methodology. Site specific studies, in partnership with industrial sites, were undergone to illustrate the predictive approach described before and demonstrate its (in)adequacy in exposure and risk assessment for populations living nearby local sources. Ambient air levels of butadiene gathered in these studies have generated original data in France, compatible with toxicity levels. In the theoretical approach, 1,3-butadiene exposure concentration and the risk calculation are computed using the probabilistic approach. Monte Carlo simulations show risks which were not negligible for population living in the vicinity of synthetic rubber's manufacturers. For carcinogenic effects, the order of magnitude of individual life-long cancer risk is 10–3 (P90 = 2,7.10–3) which leads to an health impact ranging from 2 (P10) to 114 (P90) cases of Feukemia in the target population (estimated to be 42 128 persons nationwide). These results are based on the unit risk derived recently by EPA (3.10–5 (µg/m3)-1) but they do not take into account several factors i.e. the fact that butadiene is not persistent in the atmosphere: as a result, contact with population is very limited in time and space. Measurements at 3 industrial sites borders show concentrations in ambient air ranging from 0.2 to 1 µg/m3 on average for butadiene (10 hours measurements using Restek SilicoCan canisters and US-EPA-TO 14 methodology) by comparison with estimations ranging from 100 to 200 µg/m3 for the same sites using the European methodology. Individual life-long cancer risk for 3 sites representative of the various types of industrial sites releasing 1,3-butadiene in France are 100 to 1000 less significant (ranging from 10–6 to 10–5) compared with the predictive EU approach. These results tend to show the inadequacy of the European local scenario methodology in 1,3-butadiene exposure and risk assessment. However, results are in adequacy with the regional scenario of the European evaluation and with results obtained in an urban context during this study. Comparable conclusions are reached for acrylonitrile. For styrene, site specific results are between the local and regional European scenarios.

The long-term effect of isocyanates on the respiratory system has been studied in 318 workers employed in factories using isocyanates for the production of plastics. The workers were investigated by means of a questionnaire and also by pulmonary function tests of vital capacity (VC), forced expiratory volume in one second (FEV1.0), flow volume loops, bronchial reactivity and carbon monoxide single breath transfer factor (Tco). There were no more clinical symptoms in the exposed group than in the unexposed group, but lower values of VC and of diffusion constant Kco, were observed in the exposed group, usually after long exposure. It is suggested that these workers might develop fibrosis.