Preparation And Properties Of Filters And Composites Of Fine And Short Fiber From Cotton Stalk Bark

Cotton straw is an important biomass resource with a wide range of sources and huge output.The annual yield of cotton straw in China is as high as 26 million tons,of which the quality of cotton stalk barks is about 7 million tons.However,cotton straws is still burning in the field due to the inadequate recycling,lack of processing technology and narrow application.It will cause a serious burden on the air,but also lead to the waste of resources.Some studies have tried to separate the cotton stalk bark and ues the fiber in textile fiber and composite.In this paper,cotton stalk bark fiber was extracted by repeated steam explosion,and the non-woven was prepared by papermaking and thermo-compression.The process for the separation of cotton stalks and the preparation of nonwovens were discussed.The cotton stalk bark fiber was respective mixed with chitosan to prepare filters and mixed with polylactide(PLA)to prepare composites.The preparation,properties,and applications of the materials were studied.First,the cotton stalk bark fiber was separated by repeated steam explosion.Comparing the repeated steam explosion and the delayed steam explosion.The surface morphology,chemical composition and mechanical properties of the fibers obtained by repeated steam explosion were characterized.The repeated steam explosion reduce damage of fibers at high temperatures.These fibers are short with a large number of branches and hairiness.The optimal experiment was explosion 3 times.And the fiber yield was 32.45%,47.7 mm of length,50.4dtex of fineness,726.9 of aspect ratio,68.5%of cellulose content and 2.2±0.4 cN/dtex of breaking strength.Next,a cotton stalk bark fiber nonwoven in which fibers are randomly distributed is prepared by sheet-making and thermo-compression.The parameters of beating time and basis weight were studied.Optimal parameters were:beating for 20 minutes and the basis weight was95.5 g/m~2.At this point,the thickness of the cotton stalk bark fiber sheet was 0.113±0.007mm,the tightness was 0.846g/cm~3,the tensile strength was 2.43±0.13kN/m,the elongation was about 1.1%,and the tensile absorption was 16.94±1.9J/m~2.The process does not have chemical additives and the water can be recycled as a carrier.Finally,the application of cotton stalk bark fibers were studied.One method is to make filters by hot-pressing a cotton stalk bark fiber sheet which impregnated chitosan solution.The pressure,basis weight and chitosan concentration were studied respectively,and the air filtration,pore size and tensile mechanical properties of the filter were characterized.The best experimental conditions were 1MPa of pressure,95.5 g/m~2 of basis weight,18g/L of chitosan solution concentration.In this time,tensile strengths of the dry and wet filters were 15 MPa and7.2 MPa,respectively;the elongation was 2.5%and 3.7%,respectively;the Young's modulus was 810 MPa and 229 MPa,respectively.At a particle size of 2?m,the filtration efficiency is as high as 97.7%,and the airflow resistance is 0.24 kPa.The pore diameter is mainly distributed in 26~29?m,and the total distribution is 95%.The research results provide the possibility for the application of cotton stalk bark fiber filters in air filtration.In another method,the composite is formed from cotton stalk bark fiber and PLA fiber by beating,papermaking and thermo-compression.The mass ratio of cotton stalk bark fiber to polylactic acid and thermo-compression time were studied.It showed that the mass ratio was1/1,temperature was 190?C and thermo-compression for 15 min was the best condition.The composite has a thickness of 0.126 mm,and the tensile strength under dry and wet conditions is 12.15 MPa and 4.88 MPa,respectively.The elongation is 1.55%and 1.5%,and the Young's modulus is 1126 MPa and 508 MPa,respectively.The bending stiffness is 35 cN·cm~2/cm.The composite is constructed from cotton stalk bark fiber as skeleton into a network,and polylactic acid covers and fills the structure.This structure improves the flexibility of fiber and polylactic acid composites.In summary,the utilization of cotton stalk bark is not only in textile fibers with high aspect ratio and fiber-reinforced composites.For the effective utilization of fibers which are unequal or short,the reuse of cotton straw resources can be realized in a wider range.In addition,the combination of cotton stalk bark fiber with chitosan and polylactic acid provides new ideas for using fibers in air filtration and flexible composites.