Study On The Application Of Lignin Modified Phenolic Resin On Paper Based Friction Materials

Phenolic resin has the characteristics of low smoke,low toxicity and stable chemical resistance.It is widely used in plastics,coatings,adhesives and composite materials.Phenolic resin,however,there are also big brittleness,cure rate is slow,the free content of higher defect,choose by replacing parts of the phenol by lignin lignin modified phenolic resin,can not only improve its brittleness,lower toxicity,and can improve the use of biomass resources,reduce the use of petroleum base material,this research has the vital significance.The waterproof adhesive used in water-resistant sandpaper is mainly oil-based resin adhesive,which will inevitably produce a lot of organic waste gas in the production process.First in this study by controlling the synthesis conditions on the basis of combining the toughening and the toughening modification of lignin modified aqueous phenolic resin adhesive was prepared,and use it to water proof abrasive paper base of paper making,discusses the lignin modified phenolic resin for water proof abrasive paper paper base water resistance,mechanical properties,the influence of grinding performance and so on.Secondly,the synthetic lignin-modified phenolic resin adhesive was used as the base material,and the fiber reinforced resin based brake friction material was prepared by compacting with the polyphenylbenzodioxazole fiber paper base material.The wet printing process of PBO fiber,the preparation method of the composite material,the mechanical properties of the material and the braking friction properties were discussed.Under the condition of phenol:formaldehyde molar ratio of 1:1,alkaline lignin was used to replace phenol(the substitution rate was 40%),the phenolic modification temperature was 65℃,and the synthesis temperature was 90 ℃～100 ℃.The solid content of the product was controlled in the range of 45%-50%.Using 15 wt%sodium polyacrylate as dispersant and 50 wt%ethanol as diluent,the lignin modified phenolic resin was mixed with styrene butadiene latex and acrylic latex(5:0.8:3.2).After rolling coating and curing,the wet tensile strength of the adhesive paper increased from 0.81 kN·m-1 to 5.30 kN·m-1,which increased by 554%.The Z-direction tensile strength increased by 638%from 67.1 kPa to 495.5 kPa,and the water absorption decreased by 54.4%from 0.079 g·m-2·s-1 to 0.036 g·m-2·s-1.Using solvent lignin instead of alkali lignin and polyethylene glycol as internal toughening agent,the solvent lignin modified phenolic resin adhesive was prepared(reaction time 150 min,polyethylene glycol 600 was added 1.0 wt%,and the solid content was diluted to 33%by anhydrous ethanol).The curing temperature was 160℃ and the curing time was 5 min.The water absorption rate of the adhesive paper decreased from 0.044 g·m-2·s-1 to 0.035 g·m-2·s-1,the wet tensile strength was as high as 10.28 kN·m-1,and the Z-direction tensile strength was 1002.7 kPa.The grinding time of the waterproof sandpaper produced by the adhesive paper reached more than 30 min,which fully met the actual production requirements of enterprises.PBO pulp was obtained after pretreatment with acetone extraction for 24 h and 1 wt%potassium permanganate/sulfuric acid immersion for 10 min.Under the condition of adding 0.5 wt%polyvinyl oxide as dispersant,PBO pulp with beating time of 30 min(W30)and 60 min(W60)and aramid pulp or aramid precipitation fiber(6:1:3)were wet coprecipitatively formed to obtain PBO paper.After hot pressing(temperature 200℃,time 60 min,pressure 3 MPa),the solvent lignin modified phenolic resin adhesive was impregnated and cured at 160℃ for 20 min.PBO fiber reinforced phenolic resin based brake friction materials(permeability,tensile strength and Z-tensile strength are 6.31 L·min-1,5.98 kN·m-1,752.7 kPa,respectively)were obtained.When the friction temperature increased from 100℃ to 200 ℃,the friction coefficient remained stable at about 0.25 μ,and the wear rate decreased from 0.15×10-7 cm3·n-1·m-1 to 0.06×10-7 cm3·n-1·m-1.The friction coefficient also remains in the range of 0.27 μ～0.29 μ when the temperature decreases from 200 ℃ to 100 ℃.Scanning electron microscope observation shows that the micro surface is smooth after friction,the surface wear is uniform,and there is no micro convex or peeling off,which can fully meet the requirements of brake friction materials.