Preparation And Interfacial Characterization Of Modiifed-Bamboo-Fibers Reinforced Unsaturated Polyester Composites

Recently natural fiber reinforced unsaturated polyester (UPE) composites havereceived more and more attention because of its wide application and market potential.In order to investigate the effect of bamboo fiber morphology on the mechanicalproperties and water resistance of bamboo-fiber-UPE composites, the aspect ratiosand chemical composition of bamboo powders and bamboo original fibers weremeasured. The results showed that the length of bamboo powders were distributedmajorly into0.1~0.7mm, and bamboo original fibers into10~30mm respectively.The width of bamboo powders were basically distributed into20~220μm, whilebamboo original fibers into40~190μm. The length-width ratio of bamboo powdersranged from1.5to10.5, while bamboo original fibers from40to280, showing asignificant difference between bamboo powders and bamboo original fibers. Thecontent of cellulose, pentosan and lignin of bamboo powders was37.3%,20.1%and24.50%, respectively; while that of bamboo original fibers was65.6%,17.1%and11.5%, respectively. The difference of fiber morphology and chemical compositionbetween bamboo powders and bamboo original fibers might reveal partly how theyinfluence the mechanical properties of bamboo fiber reinforced UPE composites.The bamboo/UPE composites were prepared by hand lay-up compressionmolding. The process parameters of composites were optimized using orthogonalexperiments. Analysis of variances of the results of orthogonal experiments revealedthat the optimum combination of process parameters for composites was as follows:100g for bamboo powder usage,160°C for hot-pressing temperature,20min forhot-pressing duration,7g for initiator usage,0.5g for acclerant usage, and1g fordiluent usage.The bamboo powders were treated by isocyanantoethyl methacrylate (IEM) asmodifier and dibutyltin dilaurate as catalyst. The modified bamboo powder reinforcedUPE composites were prepared with the optimum process parameters. Themechanical properties and water absorption of the resulting composites wereinvesitigated as well. It was found that the mechanical properties of IEM-treated bamboo powder reinforced UPE composites significantly improved compared withthose of untreated-bamboo-powder composites. The modified-bamboo-powdercomposites had the highest tensile strength and flexural strength when IEM contentwas5%based on the weight of bamboo powders. The modified-bamboo-powdercomposites had38.3%and36.8%higher than that of untreated-fiber composites interms of the tensile strength and flexural strength, respectively. However, theirflexural modulus and impact strength had no significant difference between indifferent IEM usages. Also the modified-bamboo-powder-UPE composites had betterwater resistance compared with untreated-fiber-UPE composites.Also, the bamboo original fibers were treated by IEM and using dibutyltindilaurate as catalyst. The effects of surface modification for bamboo original fibers onthe mechanical properties and water resisitance of the reruslitng composites wereinvestigated. The results showed that the mechanical properties of IEM-modifiedbamboo original fiber reinforced UPE composites significantly increased comparedwith those of untreated-fiber composites. The IEM-treated-fiber composites had thehighest tensile strength when the IEM content was3%based on the weight of bamboooriginal fibers; and they had53.5%higher tensile strength than that of theuntreated-fiber composites. The IEM-treated-fiber composites had the highest flexuralstrength and flexural modulus when the IEM content was5%based on the weight ofbamboo original fibers, and had38.9%and25.9%higher flexural strength andflexural modulus than that of untreated-fiber composites, respectively. Compared withthe control, all the modified-fiber composites with different IEM usages had betterwater resistance.The interfacial adhension between bamboo powders and bamboo original fiberswere characterized by scanning electronic microscope (SEM) using thefractured-surface of composites as samples. The surface chemical composition ofbamboo fibers were characterized by using Fourier transform infrared (FT-IR) andX-ray photoelectron spectroscopy (XPS) analyses. The SEM graphs showed thatbamboo powders and bamboo original fibers were well coated with UPE resins aftermodification with IEM and the interfacial adhesion between fibers and UPE resins was much better than that of the untreated ones. The results of FT-IR and XPSanalyses showed that carbamates were formed on the IEM-modified fibers, i.e., IEMwere bonded covalently onto fiber surface.