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Alberto Modelli Barbara Calcagno Mariastella Scandola 《Journal of Polymers and the Environment》1999,7(2):109-116
The standard test method ASTM D 5988-96 for determining the degree and rate of aerobic biodegradation of plastic materials in contact with soil was applied to poly(3-hydroxybutyrate) and poly(-caprolactone). The method proved to be reliable and supplied reproducible measurements of CO2 production, provided potassium (instead of barium) hydroxide was used as a trapping solution. The trends of CO2 evolution, as a function of time, observed for the degradation of polymer powders in soil are similar to those predicted by simple first order kinetics in solution. The experimental data are described by a Michaelis–Menten type model, which accounts for the heterogeneity of the polymer-soil system. The kinetic equation deduced predicts the degradation rate to the proportional to the exposed polymer surface area. 相似文献
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D. F. Gilmore R. C. Fuller B. Schneider R. W. Lenz N. Lotti M. Scandola 《Journal of Polymers and the Environment》1994,2(1):49-57
Blends of the bacterially produced polyester poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) with cellulose acetate esters (CAE) further substituted with propionyl or butyryl groups (degree of substitution: 2.60 propionyl and 0.36 acetyl or 2.59 butyryl and 0.36 acetyl, respectively) were exposed for 4 months to activated sludge to determine their biodegradability. Samples of such blends made by solution-mixing and solvent-casting had complex morphologies in which both individual components as well as a miscible blend phase were present. Additionally, the two opposite surfaces of solvent-cast films showed both physical and chemical differences. After 2 months, samples of pure PHBV had degraded by more than 98% (15 mg/cm2 of surface area), whereas a pure CAE sample had degraded less than 1% (<0.2 mg/cm2). Samples containing 25% CAE lost less than 40% of their initial weights (6 mg/cm2) over the total 4-month period. Samples with 50% CAE lost up to 16% weight (2 mg/cm2), whereas those containing 75% CAE lost only slightly more weight than corresponding sterile control samples (1 mg/cm2). NMR results confirm that weight loss from samples containing 25% CAE resulted only from degradation of PHBV and that the surface of samples became enriched in CAE. Solvent-cast film samples containing equal amounts of PHBV and CAE degraded preferentially on the surface which formed at the polymer-air interface. Scanning electron microscopy and attenuated total reflectance infrared spectroscopy revealed this surface to have a rougher texture and a greater PHBV content. 相似文献
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M. R. Timmins D. F. Gilmore N. Lotti M. Scandola R. C. Fuller R. W. Lenz 《Journal of Polymers and the Environment》1997,5(1):1-15
An assay method has been developed for monitoring the enzymatic degradation of thin films of translucent polymers. The method
was based on the observation that when a solution-cast film of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was exposed
to a solution of a depolymerase fromPseudomonas lemoignei, the surface of the film roughened and the film became visibly turbid. This increase in turbidity could be measured spectrophotometrically
and was reproducible during the initial stage of degradation. Turbidity correlated very closely with film weight loss early
in the degradation but reached a maximum value before extensive degradation had taken place. For a given set of films, this
correlation was independent of the concentration of the enzyme used, although it did vary with the mode of enzyme exposure.
The turbidity was associated with the exposure of crystalline domains due to the removal of amorphous material from the film
surface. The increase in crystallinity at the surface was verified by attenuated total reflectance infrared spectroscopy (ATRIR).
In conjunction with SEM, weight loss, and ATRIR, the film turbidity assay provided much semiquantitative insight into the
mechanism of the enzymatic degradation reaction. This assay was used to study the enzymatic degradation of films of PHBV solution
blended with cellulose acetate esters (CAE). The presence of only 25% of CAE of degree of substitution 2.9 severely hampered
the enzymatic degradability of PHBV, a result which is consistent with the environmental degradation of these same samples
exposed to activated sludge. 相似文献
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