The Preparation And Sand-water Erosion Wear Resistance Of Bamboo Fiber/PTMG-based Polyurethane Elastomer

Bamboo fiber(BF)is a natural high-performance plant lignocellulosic fiber.It has the outstanding characteristics of wide sources,easy availability,low cost,light weight and high strength.In recent years,it has been successfully used as reinforcement in polymer matrix composites.Polytetrahydrofuran ether glycol/toluene diisocyanate(PTMG/TDI)casting polyurethane(PU)elastomers have lots of excellent properties such as low heat generation,high wear resistance,solvent resistance,perfect dynamic mechanical properties,excellent adhesion to metal and outstanding comprehensive performance,widely used in fields of pulley,pipeline transportation and so on.However,the limited mechanical strength of PTMG2000-based polyurethane elastomer can not adjust to higher loading fields such as sand-water transportation pipeline lining.Therefore,the BF introduced into the PTMG/TDI polyurethane elastomer in this paper,the surface treatment of the BF and the performance of the composites were studied.Besides,the sand-water erosion wear resistance and application in pipeline lining of the composite was explored.The numerical prediction method of sand-water erosion wear of composite pipelines was also established,which can provide a certain reference for the prediction and analysis of sand-water erosion wear of polyurethane composite pipelines under complex working conditions.(1)In order to achieve the full reinforcing effect of BF on PU elastomers,the effects of alkali treatment(15wt%Na OH solution)at different temperature and time on BF were studied.The effects of alkali treatments on BF were analyzed via infrared(FTIR),scanning electron microscope(SEM),X-ray diffraction(XRD),contact angle and other tests,and the optimal alkali treatment conditions and mechanism of bamboo bundle fibers obtained.The conclusions were as following:With the increase of the alkali treatment temperature,the non-cellulose components such as lignin and hemicellulose in the bundle fibers continued to dissolve,with the elementary fibers separated from the bundle fibers and the cellulose on the fiber surface continuously exposed.The optimal alkali-treated bamboo fiber(NBF)was obtained at 100?and 2 hours.The NBF have lots of elementary fibers with smaller diameter,higher reactivity.Its cellulose content increased by 11.25%than that of the original BF,and its crystallinity was close to that of the original BF.The cellulose content increased,which increased the reactivity of the cellulose hydroxyl groups on the surface of the NBF.Its contact angle with the PU prepolymer decreased to 55°from 68°,improving the interface chemical bonding and achieving sufficient enhancement to the PU matrix.(2)NBF/PU composites were prepared by in-situ polymerization.The tensile and tear strength of NBF/PU increased first and then decrease with the increase of fiber content.With3wt%fiber content,the tensile and tear strength of NBF/PU were 44.0 MPa and 87.3 k N/m,improvement by 75.3%and 32.2%compared with pure PU,respectively.With the same fiber content,the reactivity of cellulose hydroxyl groups on the surface of NBF was better than that of BF,contributing to the better interface bonding between NBF and PU matrix than original BF,achieving better enhancement of PU.while the elongation at break of NBF/PU-3 still maintained more than 500%.The microphase separation structure of NBF/PU-3 was excellent.The maximum decomposition rate temperature T_max1of the hard phase and T_max2of the soft phase were 307.4?and 412.5?,respectively,much higher than pure PU,thermal stability of NBF/PU-3 improved.In addition,NBF/PU-3 has excellent dynamic mechanical properties and perfect low temperature resistance.The glass transition temperature(Tg)was about-39.6°C,and the loss factor was 0.259,which was slightly lower than that of pure PU.Unluckily,when the fiber content is 3wt%,the processing viscosity of the NBF/PU composite was relatively large,up to 4.57 Pa.s.(3)In order to solve the problem of high viscosity in the processing of composites,the surface coating of BF through a laboratory-made high-reactivity PU coating agent with a14.5%-NCO group was studied.FTIR,SEM and XRD results proved that after coating treatment,the surface of PUBF was chemically coated with a thin layer of PU coating agent,and the molecular end of the coating layer was terminated with an amino group(-NH₂).Since the coating layer and the PU matrix were both polyurethane,which was very beneficial to the interface compatibility of the composites.The viscosity test showed that the processing viscosity of the PUBF/PU was less than 2.7 Pa.S within 5wt%of BF coated with PU(PUBF),closed to that of pure PU,which had good processing fluidity and helpful for rotary casting molding of polyurethane pipeline lining.The tensile and tear strength of PUBF/PU-3 prepared by in-situ polymerization increased from 25.1 MPa and 66 k N/m of pure PU to 38 MPa and82.9 k N/m,respectively.In addition,the flexural resistance resistance of PUBF/PU-3improved by more than 700%compared with pure PU,the rolling wear resistance increased by 44%,with the wear resistance further improved.Sand-water erosion experiments showed that within a certain condition,the erosion wear rate of PUBF/PU increases with the erosion rate and sand content,and the erosion wear rate at 40wt%sand content was 6.053E-7kg/(m².s).Its sand-water erosion wear resistance was 3.3 times of 304 stainless steel.PUBF/PU-3 had excellent sand-water erosion wear resistance,a good material for sand and water transportation pipelines.(4)The research of sand-water erosion wear resistance via experimental method need a long time and expensive cost.Based on the erosion wear datas obtained by experiment,numerical simulation was carried out on the Ansys Fluent platform.Up to now,as for PUBF/PU,the velocity exponent factor(n)and the particle size correlation coefficient C(dp)in the DPM-Generic general erosion model have no report.Therefore,these two important parameters were determined in this paper,and a numerical prediction and analysis method for sand-water erosion wear PUBF/PU pipeline was established.Numerical simulation analysis of the effects of erosion velocity and sand content on the sand-water erosion wear of PUBF/PU pipelines showed that the maximum wear position occurred at the bottom outlet section of the pipe wall,and the erosion wear rate within 22wt%of sand content was below 3.942E-7kg/(m².s).Gaussian fitting was used to obtain the sand-water erosion wear prediction formula under 30%-50%high sand content.