Ra. Gross et al., LABORATORY-SCALE COMPOSTING TEST METHODS TO DETERMINE POLYMER BIODEGRADABILITY - MODEL STUDIES ON CELLULOSE-ACETATE, Journal of macromolecular science. Pure and applied chemistry, A32(4), 1995, pp. 613-628
Studies have been conducted to determine the time dependence of film n
ormalized weight loss using in-laboratory simulations of a compost env
ironment. The composting bioreactors contained a fresh synthetic waste
mixture formulation which was maintained at 53 degrees C and 60% mois
ture. An important result from these studies is that cellulose acetate
(CA) films (approximate film thickness of between 0.025 and 0.051 mm)
with degrees of substitution (DS) of 1.7 and 2.5 appeared completely
disintegrated after 7 and 18 day exposure periods, respectively. Littl
e weight loss of these films was noted under similar temperature and m
oisture conditions using abiotic controls. The testing protocol which
was developed provided repeatable results on normalized film weight lo
ss measurements. The dependence of the synthetic waste formulation use
d on polymer film weight loss was investigated using, primarily, CA DS
-1.7 as a substrate. It was found that the time dependence of CA DS-1.
7 film weight loss was virtually unchanged for five of the seven formu
lations investigated. However, two formulations studied resulted in re
latively slower CA DS-1.7 film weight loss. Decreasing moisture conten
ts of the compost from 60 to 50 and 40% resulted in dramatic changes i
n polymer degradation such that CA DS-1.7 polymer films showed an incr
ease of the time period for a complete disappearance from 6 to 16 and
30 days, respectively. Also, a respirometric test method is described
which utilizes predigested compost as a matrix material to support bio
logical activity. Using this method, conversions to greater than 70% o
f the theoretical recovered CO2 for CA (1.7 and 2.5 DS) substrates wer
e measured. Therefore, these results indicate high degrees of minerali
zation for CA with DS less than or equal to 2.5 under the appropriate
disposal conditions.