Research Watch: Blending polymers - Environmental Science

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RESEARCH WATCH

GREEN CHEMISTRY Renewable carbon sources Natural, renewable carbon sources are expected to become increasingly important as replacements for petroleum derivatives. Lignin, which comprises 15% to 30% by weight of wood, is being investigated as a potential carbon source for materials. M-J. Chen and colleagues investigated the properties of graft copolymer of lignin and 1-ethenylbenzene. They found that the thermoplastic graft products formed stable emulsions, bonded adhesively to wood surfaces 3.11(1 were surface active. Bioconversion and degradation of the copolymers vvere confirmed with several analytical methods. Results supppst that copolymerization of

synthetic side chains onto naturally occurring polymer backbones could be a means to produce environmentally degradable materials (Macromolecules 1996 29(5) 1389-98)

Biodegradable polymers Biodegradable polymers are important for making the life cycles of products environmentally sound. Polyhydroxyalkanoates, a class of polymers being considered for biodegradable applications, are produced by a variety of bacteria as energy reserve materials. S. Y. Lee studied several aspects of bacterial polyhydroxyalkanoates, including biosynthesis, production, recovery, biodegradation, and applications. Lee found that development of this thermoplastic material in transgenic plants presents an economically feasible source of biodegradable plastic production. {Biotechnoll Bioens. 1996 49(1) 1-14)

Blending polymers The degradability of commercial polymers can be increased by blending them with degradable materials. A. M. Gajria and co-workers formed immiscible melt blends of poly(lactic

acid) and poly (vinyl acetate). Some blends showed greater tensile strength and elasticity than the original products. The authors attribute the improvements to interactions between the polymers in the blend. They found that surface tension effects of the blends in turn substantially affected the enzymatic degradability. Results suggest that the surface tension of the polymer film affects enzyme adhesion, thus 3.C" counting for the variability in enzymatic degradability. {Polymer 1996, 37(3) 437-44)

based on capillary electrophoresis (CE) that has a detection limit of 0.2 ppb and can separate enantiomeric components. In their procedure, phenoxy acid herbicides are derivatized with 7-aminoapthalene1,3-disulfonic acid prior to CE. The derivatization was quantitative and produced stable fluorescent derivatives without side products. The derivatives were detected after CE using laser-induced fluorescence. The addition of a cyclodextrin, particularly 2,3,6-tri-O-methyl-p-cyclodextrin, to the running electrolyte facilitated the enantiomeric separation. (Anal Chem 1996 68(10) 1771-77)

MEASUREMENTS

GC/MS analysis

POLICY

Unknown compounds in environmental samples are often identified through gas chromatography/mass spectrometry (GC/MS) analysis. However, complex samples can have many overlapping and coeluting gas chromatographic peaks, which cause problems for mass spectral search programs or with the interpretation of the mass spectra. N. R. Herron and colleagues developed software that reprocesses GC/MS data to enhance the quality of the spectra used to identify unknown compounds. The program converts raw GC/MS data to ASCII text which is incorporated into a spreadsheet. A spreadsheet macro selects only those ions that maximize within a selected number of scans and discards all other ions The resultant chromatogram shows much narrower and better resolved peaks each with enhanced sDectral qualitv (f Am Maw Spertmm 1996 7(61 598-604)

Does environmental protection cost jobs? E. Goodstein reviewed economic research on this question and found that very few jobs are lost because of the costs of environmental regulation. Even studies by labor unions suggest that only 1000-3000 layoffs per year, which account for 0.1% of all layoffs, are attributable to environmental regulation. Similarly, Goodstein found that relocation of jobs to other countries is driven far more by lower offshore labor costs than by decreased environmental costs. A review of environmental improvement as a mechanism for job creation determined that in economically depressed regions environmental improvement may accelerate job creation However this is not true for the U S economy as a whole Goodstein found (Environ Management 1996 20(3) 313-21)

Regulation versus jobs

Capillary electrophoresis Current methods for analyzing phenoxy acid herbicides are not highly sensitive and selective. New methods with improved sensitivity and selectivity need to be developed. Y. Mechref and Z. El Rassi and colleagues developed a new method

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RISK Weight of evidence C. Menzie and colleagues developed a weight-of-evidence evaluation procedure that integrates the results of

0013-936X/96/0930-374AS12.00/0 © 1996 American Chemical Society