Study On Preparation And Propetries Of Alkali Lignin-phenolic Foams Reinforced With Natural Bamboo Fiber

With the growing shortage of crude oil resources, considerable research effort has beendevoted to developing new products using renewable biomass resources as raw materials.Using renewable resources and their derivative products to prepare new lightweight buildingmaterial instead of non-renewable mineral resources completely or partially, which couldpromote the efficient use of biomass resources, and provide a new way for the preparation ofnew biomass-based foam sandwich panels. It is of great significance to the sustainabledevelopment of foam material. Due to these reasons, the development of environmentallyfriendly foam sandwich materials has become a popular area of study in China and othercountries.In this thesis, environmentally friendly PF foaming materials were prepared using alkalilignin to replace crude oil resources, which reduce the pollution of papermaking waste onenvironment. Reinforced phenolic foams by natural bamboo fiber were also prepared. Theaddition of bamboo fiber could improve the mechanical properties of foam and promote theefficient use of biomass resources. In addition, the reinforced PF foams were modified byflame-retardant modification of natural bamboo fiber and phenolic foam, which could bestowfoam materials with low toxicity and high performance. Meanwhile a new lightweightfire-retardant panel for energy-saving insulation and sound insulation were also prepared usingmodified PF foam compositing material as core materials to develop, lightweight buildingmaterials, damping materials, decoration and other aspects with high performance and highsafety. The main research contents and conclusions are as follows:1. First, modified PF resins were prepared by utilizing alkali lignin as phenol’ssubstitution to prepare PF resin instead of phenol partially. Prepared alkali lignin-phenolicresin has a phenol substitution level in the range of10⁴0%. The effects of alkali lignin on thestructure, preparation and properties of the resin were studied in detail. When the formaldehydeto phenol （F/P） molar ratio is1.8and the substitution level of phenol less than30%, the viscosity of prepared resin could meet the demand of expandable resin, in this case the residualfree formaldehyde and phenol is very low. The analysis of rheological properties showed thatthe prepared resin possessed Newton fluid behavior when alkali lignin’s substitution lever wasin the range of10%to30%. TGA-DTG-DSC analysis illustrated that thermal stability and theexothermic peak of the resin decreased with the increase of the substitution level of alkalilignin to phenol, and the reaction enthalpy also showed an obvious downtrend.13C-NMRanalysis suggested that connected mode between pure PF phenol internuclear connections waspara-position based, while in the resin with30%of alkali lignin substitution level （KLPF-30）there existed ortho-and and on-para two different linkages. DSC analysis showed that Theanalysis of non-isothermal DSC showed cured process of KLPF-30resin. The cure kineticmode was also established, the apparent activation energy of the curing system was93.51kJ/mol and the reaction order was0.9506.2. By studying the influence of curing agent on mechanical properties, oxygen index andthermal stability of the phenolic foam, we took hydrochloric acid-phosphoric acid-organicacid-water mixed curing agent as the curing agent of PF foam and alkali lignin-phenolic foam.The effects of alkali lignin’s substitution level on mechanical properties, thermal stability,flame retardant properties and microstructure of PF foam were analyzed. The analysis resultsshowed that compressive strength, flexural strength, foam powder surface salinity and othermechanical properties decreased with the increase of alkali lignin’s substitution level, and thepore of foam material showed enlargement size and uneven distribution. While the flameretardant and thermal stability of phenolic foam showed changing tendency with the variationof alkali lignin content. The mathematical models of the density-mechanical properties of thealkali lignin-PF foam were established according to the classical Gibson-Ashby model and fitmodel of density and mechanical properties data, and the established model was basicallyconsistent with real testing data in the density range of0.030⁰.300g/cm3, and the obtainedindex was close to the simplified Gibson-Ashby formula’s index value in the range of1.3941¹.7758. 3. The compatibility between natural bamboo fiber and PF foams or alkalinelignin-phenolic foams was improved using silane coupling agent KH550as bamboo fiber’ssurface modification agent, and then the effect of modified bamboo fiber on the flame retardant,mechanical and the structure of modified compositing foams were studied. For theirmechanical properties, modified bamboo fiber improved the toughness of cell walls andincreased compression strength, flexural strength and surface powder degree of foams. Theoptimal addition of modified bamboo fiber for reinforced PF foam and alkali lignin-phenolicfoam was3%and4%, respectively. Smoke release characteristics and heat release rate of PFfoam and alkali lignin-phenolic foam modification with different addition amount of bamboofiber were measured by cone calorimeter. The analysis results displayed that the heat releaserate, total heat release, mass loss rate, smoke production rate （or smoke release rate） and thetotal amount of smoke （or total smoke release amount） of PF foam and alkali lignin-phenolicfoam showed uptrend with the increase in bamboo fiber content, which indicated that theaddition of bamboo fiber could reduce the flame retardant properties of PF foam and alkalilignin-phenolic foam. Especially when bamboo fiber content in PF foam is≥5%and in alkalinelignin-phenolic foam is≥4%, the flame retardant properties of foam materials had a greatreduction, so it is necessary to carry flame retardant modification for bamboo fiber.4. The best fit flame retardant of nature bamboo fiber and PF foam was explored. Theanalysis results showed that N-P composed of flame retardant and ammonium dihydrogenphosphate （ADP） flame retardant was fitted for nature bamboo fiber. Two kinds of flameretardants are phosphorus flame retardant and their retardant mechanism were consistent, andthe optimum addition amount was15%. The mechanism of flame retardant of melamine wasthat rapid decomposition of ammonia and nitrogen that are not combustible gas and theseplayed the key role for PF foam’s flame retardant property. Oxygen index of2%melamineflame retardant modified PF foam was67.8, which was over35.06%than that of PF foam.Orthogonal testing analysis showed the optimal flame retardant for nature bamboo fiber is ADPand optimal content was15%, the optimal flame retardant for alkali lignin-phenolic foam agentwas melamine and optimal content was3%. Oxygen index of lignin-phenolic foam reinforced by flame retardant nature bamboo fiber could reach55.6. The compressive strength, bendingstrength and dregs rate of lignin-phenolic foam were92.99kPa,134.96kPa and7.99%,respectively.5. The combustion characteristics of alkali lignin-phenolic foam （KLPF）,5%naturebamboo fiber reinforced alkali lignin-phenolic foam （5B-KLPF） and5%flame retardantmodified bamboo fiber reinforced alkali lignin-phenolic foam （ZR-5B-KLPF）, were analyzedby using the cone calorimeter under the condition of thermal radiation flux at25,50and75kW/m2. Flame retardant ADP and melamine had obvious effect on modifying5B-KLPFfoam, and5B-KLPF foam had a high char yield, low heat release and smoke release.Meanwhile, the fire risk comprehensive evaluation system of polymer material was establishedby analyzing the data of fire growth index （FGI）, heat index (THRI_6min), smoking index(TSPI_6min), toxic gas generation rate index (ToxPI_6min) via CONE test, the fire dangerindex-IFHI of these3kinds of foams showed that ZR-5B-KLPF had the minimum fire hazard.The mechanical and flame retardant properties of alkali lignin-phenolic foam had promoted toobtain a certain degree of promotion via flame retardant modification and nature bamboo fiberreinforced.6. The reinforced PF foam sandwich panels were manufactured using renewable bamboofiber, sliced bamboo veneer and bamboo lamina as raw materials. The nature bamboo fiberreinforced PF foam sandwich panel was prepared with epoxy adhesive and natural hemp’s fibermesh fabrics. The properties of the sandwich panels reinforced by natural hemp’s fibers meshfabrics could closely meet the demands of industry standard （JC/T1051–2007）"Aluminum foilfaced rigid phenolic foam sandwich panels". In order to improve the mechanical properties andprocessability of sandwich panels, alkali lignin-phenolic sandwich panels was prepared byusing bamboo lamina existed in market as raw material. N-P compositing flame retardant andADP flame retardant were much fitted for sliced bamboo veneer and bamboo lamina, and theoptimal retention rate was3.80%and3.58%, respectively. A comparative analysis of flameretardant properties of natural bamboo fiber reinforced sliced bamboo veneer PF foamsandwich panels and natural bamboo fiber reinforced bamboo lamina alkaline lignin-phenolic foam sandwich panels were studied by using the cone calorimeter. The results showed thatthese2kinds of flame retardants had obvious effect on each composite plate. The preparedfoam sandwich panels had high char yield, low heat release and smoke release. Meanwhile, avariety of foam sandwich panels were also trial-manufactured.