BIODEGRADATION OF CELLULOSE ESTERS - COMPOSTING OF CELLULOSE ESTER DILUENT MIXTURES

A number of polymers such as polylactic acid (PLA), polycaprolactone ( PCL), polyhydroxybutyrate (PHB), Matter-Bi, cellulose acetate (CA) wit h different degrees of substitution (DS), and cellulose ester-diluent mixtures have been evaluated in a static, bench-scale simulated munici pal compost environment. Of the polymers evaluated; cellulose acetate (DS < 2.2), poly(hydroxybutyrate-co-valerate) (PHBV), and PCL exhibite d the fastest composting rates, completely disappearing after 14 days. Optically clear resins were prepared from CA (DS = 2.06) and triethyl citrate (TEC) by thermal compounding, and the resins were converted to compression-molded film and injection-molded bars for composting stud ies. A series of miscible blends consisting of cellulose acetate propi onate (CAP) and poly(ethylene glutarate) (PEG) or poly(tetramethylene glutarate) (PEG) were also prepared and evaluated in composting. In ad dition to measured weight loss, samples were removed from the compost at different intervals and evaluated by gel permeation chromatography and H-1 NMR. As expected, the CA/TEC films disappeared rapidly upon co mposting while the injection-molded bars exhibited weight losses of 10 -12%. For the CAP/polyester blends, the type of polyester (PEG versus PTG) in the blend made no difference in composting rates. In general, as the DS of the CAP decreased and the amount of polyester in the blen d increased, the rate of composting and the weight loss due to compost ing increased. When the CAP was highly substituted, almost all of the weight loss was ascribed to loss to polyester. When the DS of the CAP was below approximately 2.0, both components degraded.