Infrared and nuclear magnetic resonance evidence of degradation in thermoplastics based on forest products

The degradation of lignin-(1-phenylethylene) graft copolymers (lignin-styrene graft copolymers) by white rot basidiomycete fungi was followed by monitoring aromatic absorption bands by Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy. The FTIR of the graft copolymers shows a series of characteristic absorbance peaks from multi-substituted aromatic rings and a strong poly(1-phenylethylene) (polystyrene) absorbance peak from monosubstituted aromatic rings. Subtraction of copolymer spectra taken before incubation from spectra taken after 50 days of incubation with the four tested fungi shows the loss of functional groups from the copolymer. NMR spectra also show reduction of aromatic ring resonances from the copolymer and incorporation of peaks from fungi as a result of incubation with fungi. The biodegradation tests were run on lignin-(1-phenylethylene) graft copolymers which contained 10.3, 32.2, and 50.4% of lignin. The polymer samples were incubated with the white rot fungiPleurotus ostreatus, Phanerochaete chrysosporium, andTrametes versicolor, and the brown rot fungusGleophyllum trabeum. White rot fungi degraded the plastic samples at a rate that increased with increasing lignin content in the copolymer sample. Both poly(1-phenylethylene) and lignin components of the copolymer were readily degraded. Observation by scanning electron microscopy of incubated copolymers showed a deterioration of the plastic surface. The brown rot fungus did not affect any of these plastics, nor did any of the fungi degrade pure poly(1-phenylethylene).Paper presented at the Bio/Environmentally Degradable Polymer Society—Second National Meeting, August 19–21, 1993, Chicago, Illinois.