The Graft Copolymerization Of HBS Lignin

As environmental pollution and resource crisis was more and more concerned by the world, the renewable and degradable natural polymer become more and more important to the human. Lignin is an amorphous, aromatic network polymer, next to cellulose and chitin in natural abundance. But most of lignin was not utilized efficiently, because of its special and complicated structure. To make full use of lignin, it was designed molecule's structure by graft copolymerization. The HBS lignin is a new type of lignin, which is released from woods, grasses and straws by using high boiling alcohol as a solvent. Graft copolymerization of HBS lignin with acrylamide, styrene, and polystyrene was studied in solution or by reactive extrusion. The graft copolymer was used as the compatibilizer in blend plastic and lignin. HBS lignin can be effectively copolymerized with acrylamide or styrene initiated with H₂O₂ and FeSO₄·7H₂O in dimethyl sulfoxide medium and the atmosphere of N₂. The influence of various factors to yield, graft rate and graft efficiency in the graft copolymerization was investigated. The optimum graft conditions were obtained. As for acrylamide, the suitable conditions include acrylamide: HBS lignin(quality ratio)=2-4, H₂O₂ 6-14%, FeSO₄·7H₂O 1-2%, temperature 40-50℃,reaction time 4h. The yield and graft efficiency were respectively obtained more than 90% and 80%. As for styrene, the suitable condition include styrene: HBS lignin=1, H2O230%, FeSO4 · 7H2O1%, temperature 35℃, reaction time 4h. The yield and graft rate were respectively obtained more than 72% and 32%. The graft copolymer was further checked by IR spectra. HBS lignin can be effectively copolymerized with styrene initiated with BPO in molten state by reactive extrusion technology. The graft copolymer was checked by IR spectra. The graft copolymerization condition was studied by three factors and three levels orthogonal experiment. The suitable conditions for graft copolymerization are: HBS lignin 100phr, styrene 10phr, BPO 0.5phr, temperature 120℃, reaction time 5min. The graft rate was obtained more than 3%. HBS lignin also can be copolymerized with polystyrene initiated with DCP in the process of reactive extrusion. The graft copolymer of HBS lignin and PS was checked by IR spectra. The recovery material of PC/ABS that added in HBS lignin or the graft copolymer of HBS lignin and acrylic acid from 2.5phr to 15phr can increase tensile strength and impact strength. The tensile strength of the recovery material of PC/ABS increased 1.7 times, the impact strength increased 2.2 times. The graft copolymer can improve the compatibility between HBS lignin and PC/ABS. The advantages of graft copolymerization by reactive extrusion are: continuous production, short periodicity, high efficiency, non-solvent and lower cost. The reactive extrusion is expected to be a new, important method of the graft modification of HBS lignin.