Blends of bisphenol-A polycarbonate and acrylic polymers: II. PC/acrylic copolymers as a new route for compatibilization

An acrylic polymer containing acid and anhydride units, referred to as reactive polyglutarimide (RPGI), has been used to react with PC. The reaction has been previously determined as an acidolysis of the carbonate bond which breaks the PC chain in two parts. One of those two parts remains free while the other one is grafted on the acrylic backbone. We have found that the anhydride units could also react with the carbonate bonds. In this case the PC macromolecule would also be broken in two parts, which would, however, both be grafted on the acrylic backbone. The reaction has been performed in solution in order to keep good contact between the reacting units. The influence of temperature and concentration on the grafting ratio has been studied. The best experimental conditions were determined in order to obtain a grafted copolymer where the acrylic backbone only supports, on the average, one PC side chain through acid reaction or two PC chains through anhydride reaction. Indeed, these two types of reactions could not be isolated. The efficiency of this copolymer as emulsifier has been studied in solution cast blends as well as in melt mixed blends. The copolymer strongly affects the microstructure in solution cast blends where films containing 30 wt % of PC have become transparent. However, the dispersed phase size of solvent cast blends could be highly influenced by the casting conditions related to solvent trapping. In melt mixed samples, the copolymer also reduces significantly the dispersed phase size, but no transparent blends have been observed so far. These results were compared with those given in the literature describing the efficiency of a synthesized copolymer which has a more complicated structure. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 735–747, 1997     

Identification of the nitrate contamination sources of the Brusselian sands groundwater body (Belgium) using a dual-isotope approach

Isotopic fingerprinting is an advanced technique allowing the classification of the nitrate source pollution of groundwater, but needs further development and validation. In this study, we performed measurements of natural stable isotopic composition of nitrate ((15)N and (18)O) in the groundwater body of the Brussels sands (Belgium) and studied the spatial and temporal dynamics of the isotope signature of this aquifer. Potential nitrogen sources sampled in the region had isotopic signatures that fell within the corresponding typical ranges found in the literature. For a few monitoring stations, the isotopic data strongly suggest that the sources of nitrate are from mineral fertiliser origin, as used in agriculture and golf courses. Other stations suggest that manure leaching from unprotected stockpiles in farms, domestic gardening practices, septic tanks and probably cemeteries contribute to the nitrate pollution of this groundwater body. For most monitoring stations, nitrate originates from a mixing of several nitrogen sources. The isotopic signature of the groundwater body was poorly structured in space, but exhibited a clear temporal structure. This temporal structure could be explained by groundwater recharge dynamics and cycling process of nitrogen in the soil-nitrogen pool.     

Identification of the nitrate contamination sources of the Brusselian sands groundwater body (Belgium) using a dual-isotope approach

Isotopic fingerprinting is an advanced technique allowing the classification of the nitrate source pollution of groundwater, but needs further development and validation. In this study, we performed measurements of natural stable isotopic composition of nitrate (¹⁵N and ¹⁸O) in the groundwater body of the Brussels sands (Belgium) and studied the spatial and temporal dynamics of the isotope signature of this aquifer. Potential nitrogen sources sampled in the region had isotopic signatures that fell within the corresponding typical ranges found in the literature. For a few monitoring stations, the isotopic data strongly suggest that the sources of nitrate are from mineral fertiliser origin, as used in agriculture and golf courses. Other stations suggest that manure leaching from unprotected stockpiles in farms, domestic gardening practices, septic tanks and probably cemeteries contribute to the nitrate pollution of this groundwater body. For most monitoring stations, nitrate originates from a mixing of several nitrogen sources. The isotopic signature of the groundwater body was poorly structured in space, but exhibited a clear temporal structure. This temporal structure could be explained by groundwater recharge dynamics and cycling process of nitrogen in the soil-nitrogen pool.     

Sugar beet cellulose nanofibril-reinforced composites

Cellulose was isolated from sugar beet chips, a by-product of sugar production, by wet chemistry. Further processing of the cellulose with a high-pressure homogeniser led to the disruption of cell walls into nanofibrils. Cellulose sheets obtained by casting and slow evaporation of water showed higher strength and stiffness when homogenised cellulose was used compared to unhomogenised cellulose. These cellulose sheets showed significantly better mechanical performance than Kraft paper tested for reference. The addition of cellulose nanofibrils to a polyvinyl alcohol and a phenol-formaldehyde matrix, respectively, demonstrated excellent reinforcement properties. The best mechanical performance was achieved for a composite with a phenol-formaldehyde resin content of 10%, which showed a tensile strength of 127 MPa, a modulus of elasticity of 9.5 GPa, and an elongation at break of 2.9%.