Extraction Of Long Bamboo Fiber Bundles And Preparation Of Their Reinforcing Polypropylene Composites

The application of natural fibers in composites a s reinforcement ha s better economical and environmental benefits for replacing synthetic fiber.Moso bamboo as raw material,t his paper researched the extraction of long bamboo fiber bundles and preparation of their reinforcing polypropylene composites.The a ffect of splitting ways and softening parameters in extraction process on proformance of long bamboo fiber bundles were investigated,and the structure,the properties of long ba mboo fiber bundles were analyzed.P olypropylene unidirectional composite s reinforced by long bamboo fiber bundles stitched int o felts were prepared by film laminating process,Modification of the composites by biodegradable Zein were discu ssed.The research results were significantly instructive to develop new usa ge of ba mboo a nd its potential to applied in composites.The main results were a s following :Long bamnoo fiber bundles were extra cted by combined combing a nd multi-step splitting,t he effect of splitting ways on the properties of long ba mboo fiber bundles was studied.It concluded that: long ba mboo fiber bundles in length of original bamboo node could be extracted by combing.Combined combing was benifit to improve the fiber separation degree and strength of long bamboo fiber bundles,in which combing combined by rolling was better than combing combined by flattening in respect to t he fineness and strength of ba mboo fiber bundles.Multi-splitting of twice-combing could further remove the impruites and improve the surfa ce smoothness and fineness uniformity of the bamboo fiber bundles.Low concentration alkali was u sed to soften bamboo to extra ct long ba mboo fiber bundles,and the change of long bamboo fiber bu ndles was discussed.The results showed that:the residual gum、liner densitiy and tensile strength of long bamboo fiber bundles were a ffected by the softening fa ctor s:concentration of NaOH,temperature and time,which the gu m removal rate wa s a ffected significantly with the order: NaOH concentration> temperature> time,the interact ing a ffect among the factors was not significant.The a ffect of softening factors on tensile strength of bamboo fiber bundle s didn’t show any regularity,and the tensile strength mightn ’t decrea se with the increase of softening degree.The optimum softening parameters were: 7.25% for NaOH concentration,110 ℃ for temperature and 2.5h for time.Underr these parameters,the actual gu m removal rate was 85.46%.Long bamboo fiber bundles extracted by ultrasonic treatment and different ages(0.2 ~ 4 years)as the materials,the properties of l ong bamboo fiber bundles had been ananlyzed,the results indicated: the chemical composition of bamboo fiber bundles wa s simmar to that of bamboo,but the cellulose content wa s higher;The crystal type was natural cellulose Ⅰ,which wa s the same as bamboo,while the crystallinity and thermal stability were higher than th ose of ba mboo.The single fiber’s morphology of ba mboo fiber bundles was completely revealed becau se of the removal of impurties,and gaps appeared among ea ch single fiber which were benefit for the intera ction of composites.The tensile properties of ba mboo fiber bundles took out large scatter and Weibull distribution due to fiber characteristics,extraction process,and mea sure methods etc.the average tensile strength,average tensile modulus a nd the avera ge elongation at break were 504 MPa,27.28 GPa 2.28%,respectly.Ultra sonic treatment could increa se the dispersibility of fibers a nd improve the tensile strength,but hardly a ffected the chemical stru cture and thermal stability.T he age of bamboo ha s a little impa ct on t he properties of bamboo fiber bundles,a mong which 3 years ol d wa s better for the application of composites.Long bamboo fiber reinforced polypropylene unidirectional composites(LBFUCs)were prepared by stitching and film impregnation processes,the preformance wa s evaluated.The research revealed: the machnical properties of composites improved by stitching and beca me best when stiching spa ce wa s 30 mm.The suitable hot pressing parameters for machnical properties of composites were 5 Mpa and 190 ℃.When fiber volume content was 40%,the composites exhibited better tensile properties,and the tensile strength and tensile modulus were 181.83 MPa and 11.38 GPa,respectively.Reasonable extraction methods of long bamboo fiber bundle s could attribute to the mechanical properties of composites.Degrada ble Zein wa s used to modify LBFUCs,the properties and modification mechanism were evaluated.The results showed that the tensile modulus,flexural strength and flexural modulus of the composites increa sed due to the modification,but the tensile strength decrea sed.The temperature of recrystallization a nd melting of composites were not a ffected by modification.Mechanical properties of composite modified by Zein were slightly higher than that of the composites modified by alkali treatment,but lower than modified by alkali-sila ne treatment.The storage modulus and loss modulus decrea sed by Zein modification which may caused by the pla sticity of bamboo fiber bundles due to zein modification.Zein had chemically reacted with long ba mboo fiber bundles,and formed thin films on the surfa ce of bamboo fiber bundles which possiblely promote the interfa ce between fiber a nd matrix.