| Biomass liquefaction has attracted a lot of interests in the area of energy and wood products. The liquefied products derived by chemical-conversion method could be used in the production of resins, such as, replacing petroleum based phenol in the production of phenolic resins. In this work, the bamboo species selection were first studied through liquefaction in phenol according to their chemical compositions and structure. The Moso bamboo(Phyllostachys edulis) was found to be the best species for liquefaction. In order to obtain better liquefaction conditions of moso bamboo, the effect of catalysts, reaction temperatures, reaction times, and ratios of phenol to bamboo on moso bamboo liquefaction were investigated. And the difference before and after treatment of potassium carbonate were characterized with techniques of IR,13C-NMR, and 1H-NMR. This paper also studied the kinetics of bamboo liquefaction, the rheology of bamboo liquefied products, the mechanisms of bamboo liquefaction and resinification of bamboo liquefied products, curing characteristics and curing kinetics of bamboo-based phenolic resol resins, the combustion kinetics, combustion properties, and behavior of thermal decomposition of paper-plastic composites (PPC) prepared with bio-based phenolic resol resins. The results mentioned above are summarized as follows.1. Moso bamboo contained the highest amount of lignin compared to Phyllostachys praecox and Bambusa multiplex. Bambusa multiplex, and included the lowest content of lignin. According to the crystallinity of moso bamboo was the lowest among these three kinds of bamboo. Meanwhile, there was the lowest content of ash in moso bamboo, and Bambusa multiplex had the highest content of ash. The high content of ash in liquefied products could lead to the clustering phenomenon during the process of resin synthesis. The above results indicated that moso bamboo is most suitable for liquefaction.2. The moso bamboo could be liquefied completely with 5% of acid catalyst. Meanwhile, the results also showed that moso bamboo could be easily liquefied at temperature in the range of 115 to 125℃with weight ratio of phenol to bamboo between 2:1 and 1:1. And the liquefied liquid products presented good fluidity. 3. The IR profiles of liquefied products from the liquefaction of moso bamboo with catalyst of potassium carbonate presented a marked absorption peak at 2935 cm-1. Moreover, with temperature increasing, the absorption peak of methylene group became stronger and wider. These results suggested that the saturated bond increased during the process of liquefaction.4. The addition of potassium carbonate did not produce a significant effect on the chemical structure of liquefied products from different temperatures (100,120 and 150℃) according to their analyses of 13C-NMR and 1H-NMR. And the liquefaction temperature had a marked effect on bamboo liquefaction. High temperature could help the liquefaction of bamboo. However, there were more protons in the liquefied products from liquefaction under 100℃using potassium carbonate compared to that from liquefaction above 100℃without using potassium carbonate. These results showed that the addition of potassium carbonate could accelerate the liquefaction of bamboo.5. The liquefaction reaction of moso bamboo is one-order reaction. The temperature of curing peak (Tp) was transferred to higher temperature with heating flow increasing. The activation energies of liquefaction reaction using different catalysts (potassium carbonate, potassium chloride and blank reference) were 45.95,59.99, and 58.00 KJ/mol, respectively. The curing characteristic temperatures (Ti, Tp and Tf, at 0℃/min) which were calculated based on linear regression were 69.1,97.25 and 111.85℃, respectively.6. The effects of catalyst of potassium carbonate on the steady-state and dynamic rheology behavior of bamboo liquefaction under different temperatures with weight ratio of phenol to bamboo of 3:1 were also investigated. The results showed that the addition of potassium carbonate could help the depolymerization of bamboo and the forming of combined phenol. The amount of combined phenol would become saturated with liquefaction temperature increasing. The saturation state required the liquefaction temperature of 150℃without using any catalyst. However, the saturation temperature can be decreased to 130℃with catalyst. According to the analysis of dynamic rheology, the complex network of bamboo was decomposed gradually with temperature increasing. But the network structure could still be observed in liquefied products for all the liquefaction temperatures used in this research.7. The effects of weight ratio of phenol to moso bamboo, acid catalysts and liquefaction temperatures on bamboo liquefaction were also detected. The results displayed that the bamboo could be completely liquefied using 5 wt% of HC1 or BF3 with weight ratio of phenol to bamboo of 2～1:1 under 115℃. According to the IR profiles of LB (liquefied bamboo products), BLF (liquefied bamboo products formaldehyde adhesive) and PF (phenol formaldehyde resin), there was a large amount of hydroxyl groups and aryl-ether bonds in BL and BLF. It could be caused by the combination of phenol with the small fragments derived from the decomposition of lignin and cellulose in bamboo. The IR spectrum of BLF performed several similar characteristic peaks with that of PF resin.8. The BLFs were synthesized using LB and formaldehyde with molar ratio of phenol to formaldehyde betweenl:1.6～2.0. In accordance with the TG-DSC analyses of BLF and PF resins, BLF showed lower curing temperatures than those of PF resin. Moreover, BLF displayed similar IR profile with that of PF resin.9. The curing kinetics of BLFs was obtained according to the DSC analyses of BLFs. The results showed that the activation energy of curing reactions of BLFs decreased with the increasing of molar ratio of F/P (1.3:1,1.6:1, and 1.8:1). The activation energies of them were 64.60,58.36 and 57.12 kJ/mol, respectively. These results indicated that the energy for curing reaction of BLF decreased gradually with the increasing of molar ratio of F/P. Meanwhile, similarly, the characteristic curing temperatures (Ti, Tp and Tf) at heating flow of 0℃/min also decreased with the increasing of molar ratio of F/P.10. The combustion behavior of three kinds of paper-plastic composite materials MLBPF-PPC (Melamine modified bamboo Phenol Formaldehyde-Paper Plastic Composite), MPF-PPC (Melamine modified Phenol Formaldehyde-Paper Plastic Composite) and PF-PPC (Phenol Formaldehyde-Paper Plastic Composite) were studied by using a cone calorimeter. The single equation rate model of mass loss rate (0～60%) and time was simulated by using a chemical kinetic method (g(a)=[-ln(1-a)]1/2]). The average activation energy Ea calculated based on the above equation of MLBPF-PPC, MPF-PPC and PF-PPC were 14.18,27.1 and 26.47 kJ/mol, respectively. The Ea of MPF-PPC and PF-PPC were almost two times than that of MLBPF-PPC. The similar results were also obtained from the analyses of combustion properties under temperature of 733℃(radiation power of 50 kW-m-2), such as mass loss rate, total heat released, heat release rate, total smoke released and yields of CO and CO2. In summary, the flame-retardant properties of three kinds of materials were MLBPF-PPC< PF-PPC< MPF-PPC.11. According to the analyses of TG-DTG of MLBPF-PPC, MPF-PPC and PF-PPC, all PPCs represented two major thermal events. For the first thermal event, all PPCs showed similar thermal decomposition profiles. The second thermal event of all PPCs, however, wasmarkedly different. The possible reason could be that the addition of melamine into phenolic resins transferred the decomposition temperature of PPCs to higher temperature, and improved the combustion activation energy. Both of the decomposition temperatures and activation energies of MLBPF-PPC were the highest compared to those of MPF-PPC and PF-PPC. These results suggested that the utilization of MLBPF in PPC materials could improve the flame-retardant properties of PPC materials. |
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