Robert Marshall Gardner

The influence of degree of substitution on blend miscibility and biodegradation of cellulose acetate blends

In this account, we report our findings on blends of cellulose acetate having a degree of substitution (DS) of 2.49 (CA2.5) with a cellulose acetate having a DS of 2.06 (CA2.0). This blend system was examined over the composition range of 0–100% CA2.0 employing both solvent casting of films (no plasticizer) and thermal processing (melt-compressed films and injection molding) using poly(ethylene glycol) as a common plasticizer. All thermally processed blends were optically clear and showed no loss in optical quality after storage for several months. Thermal analysis and measurement of physical properties indicate that blends in the middle composition range are partially miscible, while those at the ends of the composition range are miscible. We suggest that the miscibility of these cellulose acetate blends is influenced primarily by the monomer composition of the copolymers. Bench-scale simulated municipal composting confirmed the biodestructability of these blends and indicated that incorporation of a plasticizer accelerated the composting rates of the blends.In vitro aerobic biodegradation testing involving radiochemical labeling conclusively demonstrated that both the lower DS CA2.0 and the plasticizer significantly enhanced the biodegradation of the more highly substituted CA2.5.

Ergosterol determination in activated sludge and its application as a biochemical marker for monitoring fungal biomass

Abstract Establishment of a routine fungal biomass monitoring program in activated sludge wastewater treatment plants (ASWTP) is of the utmost importance because it provides the bility to predict fungal infestations before they affect clarifier performance (bulking sludge). Ergosterol, a major fungal steroid, has been successfully used to determine fungal biomass in many different environments; this study sought to determine its efficacy for ASWTP. Ergosterol analysis was performed by high performance liquid chromatography. Initially, pure cultures of Geotrichum candidum were used because this organism was implicated in past clarifier problems. During a 62-h batch culture, ergosterol concentrations were found to be in direct proportion with both optical density and dry weight measurements; correlation coefficients of r = 0.95 and r = 0.99 were obtained, respectively. A mean value of 2.2 ± 0.6 μg ergosterol/mg fungal dry weight was obtained. A more stringent test of ergosterols ability to predict fungal biomass changes was performed in a batch reactor which stimulated an ASWTP. Prior to an artificially induced fungal infestation, microscopic analysis revealed low fungal levels; ergosterol measured 86 ppb. Nine days later, extensive fungal growth was evident microscopically; ergosterol values increased 57-fold, to 4880 ppb. In contrast to viable plate counts, ergosterol determinations in activated sludge provided a superior method to measure fungal biomass. Furthermore, ergosterol determinations enhanced the information obtained by microscopic examination.

Biodegradation of Cellulose Esters: Composting of Cellulose Ester-Diluent Mixtures

Abstract A number of polymers such as polylactic acid (PLA), polycaprolactone (PCL), polyhydroxybutyrate (PHB), Matter-Bi, cellulose acetate (CA) with different degrees of substitution (DS), and cellulose ester–diluent mixtures have been evaluated in a static, bench-scale simulated municipal compost environment. Of the polymers evaluated, cellulose acetate (DS > 2.2), poly(hydroxybutyrate-co-valerate) (PHBV), and PCL exhibited the fastest composting rates, completely disappearing after 14 days. Optically clear resins were prepared from CA (DS = 2.06) and triethylcitrate (TEC) by thermal compounding, and the resins were converted to compression-molded film and injection-molded bars for composting studies. A series of miscible blends consisting of cellulose acetate propionate (CAP) and poly(ethylene glutarate) (PEG) or poly(-tetramethylene glutarate) (PTG) were also prepared and evaluated in composting. In addition to measured weight loss, samples were removed from the compost at different intervals and eva...

Composting of miscible cellulose acetate propionate-aliphatic polyester blends

A series of miscible blends consisting of cellulose acetate propionate (CAP) and poly(ethylene glutarate) (PEG) or poly(tetramethylene glutarate) (PTG) were evaluated in a static bench-scale simulated municipal compost environment. Samples were removed from the compost at different intervals, and the weight loss was determined before evaluation by gel permeation chromatography, scanning electron microscopy, and1H NMR. The type of polyester (PEG versus PTG) in the blend made no difference in composting rates. At fixed CAP degree of substitution (DS), when the content of polyester in the blend was increased, the rate of composting and the weight loss due to composting increased. When the CAP was highly substituted, little degradation was observed within 30 days and almost all of the weight loss was ascribed to loss of polyester. Although the polyester was still observed to degrade faster, when the CAP DS was below approximately 2.0, both components are observed to degrade. The data suggests that initial degradation of the polyester is by chemical hydrolysis and the rate of this hydrolysis is very dependent upon the temperature profile of the compost and upon the DS of the CAP.