| Phenolic foam is a new kind of flame-retatdant thermal insulation material, it is known as"the third generation of thermal insulation material". Conventional phenolic foam wassynthesized by incorporating petroleum-based resol resin with several additional chemicals.However, with the rising cost and foreseeable future scarcity of petrochemicals and theimprovement of the environmental protection consciousness, researches on natural renewableresources replacing petrochemicals has attracted more and more attention. Lignin is animportant feedstock for the renewable production of phenolic compounds in forestrymaterials, and technical lignin is available in great quantities. Less expensive lignin can replacephenol to formulate phenolic foam thermal insulation material, which has significantpromotion to make biomass resource advantage, improve ecological environment and developphenolic foam thermal insulation material industry.In the present work, a new method of introducing lignin into resol resin was explored.Lignin was oxidated into fractions containing phenolic compounds at low temperauture, whichimproved its reactive activity. Oxidatively degradated fractions of lignosulfonate replaced50%phenol to formulate resol resin and good properties of the resulted phenolic foam was obtained.The main purpose of the thesis was to reveal effect of replacement percentage of phenol byoxidatively degradated lignin on properties of resol resin and phenolic foam. The main researchand obtained results were summarized as follows.1. Structure difference, qualitative and quantitative analysis of functional group, andthermodynamic properties of lignosulfonate. Corn kraft lignin and indulin kraft lignin werecharacterized by FTIR,UV,1H NMR,GPC,DSC and TG, corn kraft lignin was a typical GSHtype lignin, lignosulfonate and indulin kraft lignin were mainly guaiacyl structure.1H NMRanalysis showed three phenylpropanoid monomers were interconnected by a multitude ofinter-unit bonds that include several types of ethers (e.g. β-1, β-5, and β-O-4) and carbon-carbon linkages, β-O-4and β-5structures constituted the main intermonomericconnections. The contents of phenolic hydroxyl in lignosulfonate, corn kraft lignin, and Indulinkraft lignin were2.32%,3.26%and2.66%, respectively, and effective lignin contents were59.82%,85.35%and90.26%, respectively. DSC analysis indicated Tgof corn kraft lignin andIndulin kraft lignin were124℃and143℃, respectively,lignosulfonate Tgwasn't foundwithin the range of temperature.2. Optimization of lignin oxidative degradation technology was carried out usingDesign-Exper8.0software. Take reactive conditions of H2O22g, reaction time2h, reactiontemperature60℃, pH=10for example, number molecular weight (Mn) of lignosulfonate,corn kraft lignin and indulin kraft lignin decreased to493,895and1449after oxidativedegradation, versus17774,1205and1977before oxidative degradation, respectively. Thecontents of phenolic hydroxyl of lignosulfonate, corn kraft lignin and indulin kraft ligninincreased to2.98%,3.70%and2.91%after oxidative degradation, respectively. Consideringprices of three lignins, lignosulfonate was selected as phenol substitution to proceed the nextstudy.3. Oxidative degradation fractions of lignosulfonate were characterized. FTIR showedphenolic hydroxyl content increased, while methoxyl content decreased. Great changes in1HNMR spectrum was observed pre-and post-oxidative degradation. Proton absorption peak at8.5ppm was very strong, while almost none in raw lignosulfonate1H NMR spectrum, whichwas likely attributed to aromatic proton connected with strong electron-withdrawing group.Proton absorption peak at6-8ppm weakened, and so did peak at5.2ppm,4.5ppm and3.80ppm, which indicated part cleavage of ether bond and methoxy removal, macromoleculelignosulfonate degradated into small fractions. Great possible cleavage occurred at β-O-4andβ-5. UV analysis revealed partial lignosulfonate benzene rings open after oxidative degradation,its spectrum has a little red shift in comparison with raw lignosulfonate, guaiacly monoercontent increased to some extent. GC-MS analysis disclosed there were kinds of phenoliccompounds in oxidative degradation fractions. Reactive activity toward formaldehyde experiment indicated100g oxidative degradation fractions consumed0.59mol formaldehyde,versus0.41mol formaldehyde consumed by raw lignosulfonate.4. Oxidatively degradated lignosulfonate substitute phenol to formulate resol resin,properties of resol resin were effected by different formaldehyde/phenol molar ratio anddifferent lignin replacement. Free phenol content decreased and free formaldehyde contentincreased with the increasing molar ratio under the same replacement percentage of phenol bylignin. Free phenol content and free formaldehyde content both decreased with the increasingreplacement of phenol by lignin under the same formaldehyde/phenol molar ratio. Viscosity ofresol resin increased slowly when both formaldehyde/phenol molar ratio and replacementpercentage of phenol by lignin were low, Whereas it increased rapidly. Take resol resinprepared under the conditions of formaldehyde/phenol molar ratio1.7:1and differentreplacement percentage of phenol by lignin for example, HAAKE Rotational Rheometer isused to evaluate resol resin reactive activity. The results showed that reactive activity decreasedwith the increasing replacement percentage of phenol by lignin, temperature at which viscositybegan to increase tended to rise, for example,125℃was for resol resin with0%replacementpercentage to increase viscosity rose to130℃f or resol resin with50%replacement percentage.Take resol resin prepared under the conditions of formaldehyde/phenol molar ratio1.7:1forexample, differential scanning calorimetry (DSC) was applied to investigate resin resolisothermal curing reaction kinetics at different temperature, when replacement percentage ofphenol by lignin were40%and0%, reaction order were0.838and0.845, and curingactivation energy were125.27KJ mol-1and110.35KJ mol-1, respectively, indicating theintroduction of lignin decreased resol resin reactive activity.5. Different replacement percentage of phenol by lignin,different formaldehyde/phenolmolar ratio and different foam density had influence on properties of phenolic foam. Foamcompressive strength increased with the increasing of formaldehyde/phenol molar ratio on thecondition of the same replacement percentage of phenol by lignin and the same foam density.Foam compressive strength increased with the increasing of foam density on the condition of the same formaldehyde/phenol molar ratio and the same replacement percentage of phenol bylignin. When formaldehyde/phenol molar ratio was1.9:1, replacement percentage of phenol bylignin was20%and foam density was60kg/m3, foam compressive strength reached its highestvalue (0.21MPa). According to Gbison-Ashby equation, foam density-compressive strengthmodels was established. Foam closed hole rate and hole diameter were effected by replacementpercentage of phenol by lignin, when replacement percentage of phenol by lignin increasedfrom0%to50%, closed role rate decreased from99.9%to86.3%, and hole diameter increasedfrom115μm to290μm. Foam thermal conductivity was very low, it ranged from0.021W/(m·K)(0%replacement) to0.030W/(m·K)(50%replacement). The introduction of lignininto phenolic foam leaded to higher toughness, lower thermal stability, and lower oxygen index.Cone calorimeter analysis indicated lignin phenolic foam possessed shorter igniting time andlasting time, it had a decrease in effective heat of combustion (EHC) and its peak values, heatrelease rate (HRR) and its peak values (PHRR) changed little, CO and CO2rate increased alittle, heat release results decreased (THR) with the increasing replacement percentage ofphenol by lignin, compared to conventional phenolic foam.
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