The Extract Of Lignin And Its Used In Polyurethane

Lignin is a renewable aromatic compound in non-oil resources. Due to thecomplex structure, the heterogeneity of the physical and chemical properties, difficultisolation and easy condensation of lignin, it is not good use so far. Human pay anattention to the problems of environmental pollution and resource crisis, so the naturalpolymer with renewable, biodegradable characteristics is increasingly valued, whichplays an increasing role in polymer synthesis and applications.This dissertation is focus on the extraction, the utilization of alkali lignin and thecomprehensive utilization of rice husk. The methods of separating and utilizing ofthem were discussed as the following scheme shown:There are four steps in above mentioned scheme:Step1: Prapared lignin-polyurethane foam (PUF)In lignin-based polyurethane foam experiments, it was used one-step foamingprocess and successful synthesis of lignin-based polyurethane foam material. Then a series of lignin-based polyurethane foam experiments with modified lignin wereinvestigated influencing factors of foaming time and foaming multiple. Theexperimental results show that:(1) The micrographs of the lignin-based polyurethane foam pores with theincreasing addition of lignin were more smaller than PUF.(2) Meanwhile, the mechanical properties of the lignin-based PUF examined bytensile tests, showed the good tensile strength and the compressive strength.(3) FTIR analysis suggested that there were no major changes in the chemicalstructure of PUF in the presence of lignin, and the structure of the lignin-based PUFhad the same as PUF.(4) Thermal stability of lignin-based PUF measured by TGA was greatlyimproved with the addition of lignin. The decomposition temperature of thelignin-based PUF increased13°C than that of ordinary PUF before300°C, increased83°C after400°C.Step2: Prapared aqueous lignin-polyurethaneA series of lignin-based aqueous polyurethane composites have been successfullyprepared via in situ polymerization. Epichlorohydrin has greatly improved the surfacecharacteristics of lignin. PPG/lignin solution was prepared by ultrasonic andmechanical stirring, then got lignin-based APU composites with the content of0-2%lignin. The experimental results show that:(1) SEM photos showed that the lignin modified by epichlorohydrin welldispersed in the aqueous lignin-polyurethane.(2) FTIR analysis suggested there were no major changes in the chemical structureof the aqueous polyurethane in the presence of lignin.(3) Thermal stability of the aqueous lignin-polyurethane measured by TGA wasgreatly improved with the addition of lignin. The decomposition temperature oflignin-based aqueous polyurethane with2%lignin was improved13°C than that ofpure aqueous polyurethane.(4) The mechanical properties of the lignin-based aqueous polyurethane, examined by tensile tests, showed higher tensile strength than that of the pure aqueouspolyurethane. Mechanical test results showed that the tensile strength of the aqueouspolyurethane with the0.5%lignin added reached to11.144MPa, that of the lignincontent of0.5%aqueous polyurethane reached to12.967MPa, followed by1.5%and2%of the amount of lignin were5.483MPa and2.160Mpa, respectively.Step3: Prapared ligin/silica hybrids from rice huskIn the use of rice husk lignin system, rice husk was pretreated by alkali solution.The liquefaction factors of reaction time and reaction temperature and the solid-liquidratio were investigated.(1) lignin/silica hybrid was in situ designed using the Sol-Gel process from ricehusk. The ratio of Ml/Ms reached approximately2/3(lignin41.67%, silicon58.33%)under optimum hydrolysis conditions, that is, the reaction temperature was90°C,reaction time was4h, and the solid-liquid ratio was1:7.(2) In summary, the experiment obtained mesoporous lignin/silica materials werediameters of approximately60nm, and significantly high specific surface of471.7m2/g, pore volume and more uniform morphology distribution from RH.(3) Lignin/SiO2compounds in the PUF, with the amount of the increase incomplexes, the composite foam porosity decreased and the foam evenly distributed.This indicated that the compound was more evenly dispersed in the composite foam.Step4: Prapared activated carbon from rice husk(1) A simple and effective method with environmental and economic benefits wasused to prepare high surface activated carbon by phosphoric acid activation from ricehusk pretreated with alkali solution. The influence of carbonization temperatures(400-700oC) and impregnation ratios (4:1-7:1) of the prepared activated carbon onthe pore development were investigated.(2) Results showed that in all cases, the pore diameter and pore volume increasedwith increasing the carbonization temperature and the impregnation ratio. Themaximum specific surface area of activated carbon was about2188m2/g at500oC with activation duration of1h and impregnation ratio of1:7.(3) Due to the large specific capacitance of activated carbon, the activated carbonusing this precipitation method from RH could devote to the EDLC as an electrode.The maximum specific capacitance of activated carbon was198F/g.A new comprehensive utilization method of alkali lignin and rice husk wasconducted by the study of this dissertation. This method was caused by pollution andwaste from wood paper on the source of industrial waste and rice husk waste. Itcreates significant economic and social benefits. According to the results of this study,the lignin through modification has led some instead of polyether polyols, andimproved the content of lignin in the polymer, so not only can greatly reduce the costof production of the polyurethane, but also can reduce the dependence on mineralresources and environmental pressures. For the alkali lignin and rice husk resources,the development progress of the study will be a strong impetus to the alkali lignin inpolyurethane applications, as well as the industrialization of rice husk.