Preparation And Characterization Of Composite Fiber Materials

Among various methods to prepare composite fibers, electrospinning technologyhas been highlighted recently with simple operation, wide applicable rang andrelatively higher efficiency. Micro/nano size of electrospinning fibers were potentiallyused in the field of advanced materials. It became a hot spot for preparation ofnano-sized composite fibers by electrospinning in the study of fibers.This work was mainly divided into three parts. The mixtures of Poly (L-lacticacid)(PLLA) and cellulose acetate (CA) were electrospun into composite nanofibrousmembranes for the first part. PLLA and Polyoxyethylene (PEO) were electrospunsuccessfully for the second part. Chloroform and acetone with ratio of3/1(v/v) wasused as solvent for above two parts. Field-emission environmental scanning electronmicroscope (FE-ESEM), differential scanning calorimetry (DSC), wide-angle X-raydiffraction (WAXD), static material mechanical performance test and surface contactangle measurement were used to characterize the physical properties of membranes.Results were as follows.For PLLA/CA fabric membranes, the microstructure of fibers was observed byusing FE-ESEM. It was found that the fabric membranes were composed of biomodalnanofibers with the addition of CA. The mean diameter of coarse fibers increasedwith the addition of CA, but decreased with the gradual increase of CA. The result ofDSC indicated that PLLA and CA were compatible and the CA content was the mainfactor influencing the change of enthalpies in PLLA/CA fabric membranes. Staticmaterial mechanical performance test showed that the tensile stress was enhancedwith the increase of CA content. After CA was added, the hydrophilic of compositefabric membranes was improved, which was showed in surface contact anglemeasurements. The more was CA content, the better was the hydrophilic.For PLLA/PEO fabric membranes, the microstructure of the membranes wascomposed of biomodal nanofibers with addition of PEO. The mean diameter ofcomposite fibers increased with increase of PEO content. Porous structure occurredand distributed evenly on the surfaces of fibers with gradual increase of PEO content.DSC result test showed that PLLA and PEO were compatible with PEO content lessthan0.5%. However, the side effect from PLLA on the crystallization of PEO wasabated with the PEO content increased, PLLA and PEO crystallized respectively. Phase-separation occurred between PLLA and PEO in keeping with WAXD result.Tensile stress of the composite membranes increased with the increase of PEO content.Surface contact angle measurement showed the hydrophilicity of the compositemembranes was improved with the addition of PEO, which was a very importantcharacter as for electrospun materials in the application of scaffold fields.In the third part, the methods to characterize degradation performance ofcellulose fibers were studied. The biodegradability of fabrics in laboratory and largescale composting environments were compared. Four cellulose fabrics (NaturalCotton, Man-made Modal, Bamboo and Tencel) and three methods (ASTM D5988-03, enzymatic hydrolysis and composting) were used. It was found that the fourkinds of fabrics showed a good biodegradability in all three process of degradation.The degradation of man-made cellulose fabrics was better than natural cotton.Bamboo fabric showed fastest degradation rates among them. The morphology andstructures of fibrics before and after degradation were analyzed by scanning electronand infrared spectrum. Two results were further evidence for the conclusion above.Compared with natural soil and laboratory conditions, compost environment providedrelatively higher temperature and more activity components such as microbes andenzyme, which were more advantageous to the degradation of cellulose fabrics.