| Parallel Strand Lumber(PSL)is a new type of Wood-based panels produced by hot pressing after glued parallel strand paving.It is an important achievement in the production of high-strength,large-sized alternative building structures using small diameter wood and low-grade veneers,which has the advantages of high utilization,uniform material,beautiful texture,high mechanical properties and so on.Besides,it is an important structural engineering material,being sued in the fields of furniture,flooring,containers.Bamboo is a unique resource in China.It is known as the "second forest resource",for the bamboo area,standing bamboo stock,and annual output of bamboo all rank first in the world.Compared with wood,bamboo has some advantages,such as long-term use,fast growth,short cycle time,etc.Bamboo fiber is long,generally equivalent to 300-600 times that of wood fiber,with high strength,obvious directionality,etc.As a preferred material for wood engineering materials,Parallel Bamboo Strand Composite(PBSC)has the potential to alleviate the conflict between the supply and demand of wood resources.In recent years,it has gradually become a research subject in the field of materials science.However,exposure to the outdoors for a long time is prone to biodegradation and potential fire hazards,affecting the use value and safety of product.In this study,a systematic and in-depth study of the PBSC preparation process was conducted.The orthogonal test method was used to examine the effects of various factors on the physical and mechanical properties of PBSC,such as the size of the bamboo strip,the concentration of the glue solution,the immersion time,and the type of the adhesive.The best preparation process of PBSC was investigated.On this basis,the effects of copper sulfate,aluminum sulfate,and water glass on the functional improvement and protection of PBSC were examined,and PBSC was given sufficient technical and economic advantages to expand its application and gradually develop into a wood industry,realizing the concept of "replace wood with bamboor".The main details were summarized as follows:(1)The preparation process and mechanical properties of PBSC were studied,using an the orthogonal experimental design was to evaluated the effects of the raw material size,solution concentration and dipping time of phenol formaldehyde and isocyanate resin adhesives on the mechanical properties of PBSC.The results show that,within the experimental range,the mechanical properties of PBSC increased with the concentration of adhesives.The performance of PBSC reached the best values when the phenol formaldehyde and isocyanate adhesive concentrations were 30%,with MOEs of 9780MPa and 9840MPa,respectively,and MORs of 121.08MPa and 124.34MPa,respectively,and HSSs of 5.18MPa and 5.21MPa,respectively,both meeting the national standard GB/T20241-2006 "laminated veneer lumber"structural veneer lumber 100E class grade requirements,HSS meeting the national standard GB/T20241-2006 "laminated veneer lumber " structural veneer lumber 55V-47H class grade requirements.Showing the best mechanical properties when the dipping time was 60 min.The effects of the veneer strips size on the MOR and MOE of PBSC were not significant.In addition,no significant differences were found in mechanical properties of PBSC impregnated by phenol formaldehyde and isocyanate resin adhesives.(2)The mechanical properties and anti-corrosion performance of PBSC treated by preservative were examined.The results showed that compared with the control group,with the preservative loading increasing,the copper sulphate-treated PBSC showed enhanced resistance to white rot and brown rot,increased anti-bleeding performance,and decreased mechanical properties as the preservative loading increased,meeting the national standard GB/T20241-2006 "laminated veneer lumber " structural veneer lumber 100E class grade requirements.The study of white rot and brown rot results of PBSC treated with copper sulfate solution showed that compared with control group,the PBSC treated with copper sulfate solution had improved performance against white rot and brown rot.White rot performance increased by 57.1%and browning resistance improved by 61.2%.Meeting grade II decay resistance regulation of GB/T 13942-2009 durability of wood-part 1:method for laboratory test of natural decay resistance.The results of the effect of copper sulfate pretreatment on the leaching resistance of PBSC showed that,with the increase of loading,the copper loss rate decreased,when the concentration of copper sulfate solution was 10.0%,the soaking time was 24 h,and the drug loading was At 7.76 Kg/m3,the copper loss rate was 13.52 ppm.The effect of copper sulfate pretreatment on the mechanical properties of PBSC was studied.The results showed that when the concentration of copper sulfate solution was 10.0%,the soaking time was 24 h,and the drug loading was 7.76 Kg/m3,the binding strength in PBSC was reduced by 21.8%.MOR decreased by 10.5%and MOE decreased by 4.2%.(3)The results of the influence of the concentration of the flame retardant solution and the immersion time on the mechanical and flame retardant properties of PBSC showed that,compared with control group,the resistance was increased.With the increase of the loading,the flame retardancy of PBSC treated with water glass and aluminum sulfate was enhanced.The mechanical properties of PBSC treated with water glass were improved,and the mechanical properties of PBSC treated with aluminum sulfate were reduced.However,it meet the national standard GB/T20241-2006 "laminated veneer lumber" structural veneer lumber 100E class grade requirements.The effect of water glass and aluminum sulfate pretreatment on the flame retardant properties of PBSC has been studied.The results show that with the increase of the loading of the flame retardant,the time delay of the second peak appears and the total heat release decreases.Water glass and aluminum sulfate have the same flame-retardant properties as commercial flame retardants,which can effectively reduce the heat release rate and total heat release of PBSC,inhibit bamboo pyrolysis and reduce the effective heat of combustion,and delay the second pkHRR peak,reducing the total heat released,the later the second pkHRR peak appears,the better the flame retardant performance,aluminum sulfate and water glass treated PBSC reduce the pyrolysis rate and the release of toxic smoke.Flame retardant performance reach the class B2 regulation of GB8624-2012 Classification for burning behavior of building materials and products.The effect of water glass and aluminum sulfate pretreatment on the mechanical properties of PBSC was studied.The results showed that compared with control group,when the water glass solution concentration was 15%,the impregnation time was 48 h,and the loading was 7.88 Kg/m3.In PBSC,the internal bond strength increased by 25.9%,the MOR increased by 12.0%,and MOE increased by 4.6%.When the concentration of aluminum sulfate solution was 15%,the immersion time was 12 hours,and the loading was 5.73 Kg/m3,the internal bond strength of PBSC was reduced by 32.5%,MOR of PBSC was reduced by 13.7%,and MOE of PBSC was reduced by 5.1%. |
