Research On Biological Scouring Of Flax Rove And Evolution Of Fiber Structural And Properties

Natural flax fiber is known as the Queen of plant fiber. It is quaint, soft, unique cool and comfortable. These properties are not available in chemical fibers and are incomparable for other natural fibers. Flax products have the feature of green health which does consumers a favor, and is one of the most popular in the international textile market. However, technology deficiencies of the flax degumming restrict linen textile spinning high counts yarn and production of high-end products. The processes of roving scouring and bleaching can help spinning high counts yarn, but chemical scouring was multi-used in industrial which produces environmental pollution and damage to the yarn properties. So it is urgent to make bio-retting, bio-degumming and bio-scouring and bleaching process industrial application.Currently the bio-scouring of the flax roving has been done more in neutral or slightly acidic conditions. The alkaline pectinase was used for cotton fiber, fabric scouring and degumming of hemp fibers. For gum composition of flax roving as well as its use of fiber spinning process characteristics, the paper discusses possibilities of the bio-scouring in alkaline conditions. In the industrialization process of the bio-scouring, more attention to shorten the scouring time, scouring process and its effects evaluation about residual gum, strength, splitting and other indicators was paid. But the structure and properties of the fiber is less of a concern. To achieve bio-scouring or biological degumming of the flax roving, an alkalophilic strain containing pectinase and xylanase was screened from the rotten wrack around Zhoushan archipelago sea area and used for flax roving under alkaline conditions. After exploring the optimal scouring process, some novel analysis methods such as thermal analysis technology of DSC, TGA and TDA, gas chromatography-mass spectrometry, X-ray small-angle scattering and Raman spectroscopy were used to discuss the structure and performance characteristics of different flax fibers after different scouring. The conclusions of this study are as follows:(1) An alkalophilic strain was screened from the rotten wrack around Zhoushan archipelago sea area. It was characterized as Cellulomonas sp and named DA8by strain morphology, physiology, biochemistry and the16s rDNA sequences. Enzyme activity showed that the activities of petinase and xylanase were obtained, and are stable under50℃and at pH values in the range of6.5to9.0. The application showed that the strain had a good characteristic of scouring, and less strength loss of flax fiber was14.19%. Scanning electron microscopy (SEM) showed that the gum in the flax fiber was mostly degraded, and the most smooth fiber surface was displayed, compared with fiber untreated and scoured by caustic soda. The fineness and strength of bundle fiber were evaluated and the orthogonal experimental design of bacterial scouring. An optimum processing was obtained:the initial pH is9.0, the scouring temperature is40℃, Liquor ratio is1:15, degum time is12h and the shake speed is200rpm. The effect of initial pH and scouring temperature on the fineness and strength of bundle fiber was higher.(2) The effects of bleaching process, role of alkaline pectinase on bacterial scouring of DA8, DA10bacteria and crude enzyme were analysized and compared. Studies have shown that the fiber strength damage on process of bacteria scouring and bleaching is about1.5-1.9percent, while the fiber strength damage after scouring without washing and directly bleaching and direct roving bleach is relatively large. Compared to the untreated sample, DA8bacteria scouring and sodium hydroxide chemical scouring will damage flax fiber strength. But the fiber strength damage from DA8bacteria scouring is small than that of chemical scouring, and the overall strength of the bacteria scouring and bleaching is a decrease of approximately58.8%of traditional chemical scouring and bleaching.It is concluded that the amount of alkaline pectinase and DA8ratio of15:135, the fiber fineness and strength reached the highest, and that JFC, EDTA and Na5P3O10will improve further the effect of bio-scouring of DA8. The crude enzyme-alkali scouring occupy a certain advantage compared with DA10bacteria-alkali scouring on fiber performance.(3) The analysis such as thermal performance, pyrolysis kinetic and crystallization kinetics was carried out for different fibers after different scouring and bleaching processes. TGA curve indicated pyrolysis of flax roving after different scouring and bleaching processes can be divided into three processes such as the initial degradation phase, the main phase and the residue pyrolysis stage. In the third stage, DA8bacteria scouring and its bleaching is divided into carbonized fiber weight loss phase and the second phase, while other samples occurs only charring. Different residues of flax roving show bio-scouring generated volatiles more easily and will not continue to produce coke during pyrolysis. TGA, DTA and DTG analysis showed initial temperature, peak temperature and final temperature in various stages have a slight move to the higher temperature side and the main reaction zone also increases for different samples. The transition temperature was obtained from DSC curves, and the order of S4> SO> S1> S3> S5> S2was concluded. While the DSC curve of the sample with conventional chemical scouring and bleaching is relatively flat, in which the endothermic peak, exothermic peak and the glass transition temperature can not be determined. The activation energy E and the kinetic parameters were calculated by the method of Coats and Redfern during the second reaction stages. The results show that pyrolysis of flax fibers after different scouring may be represented by a second stage reaction process description, and the fitting coefficients are good in the0.99-1for all samples. The crystallinity of the fiber after scouring was also calculated from DSC curves and the parameters of crystallization kinetics flax fibers after scouring was obtained through different Avrami method.(4) Features on Pyrolysis of flax fibers after scouring treatment were analysized using pyrolysis-gas chromatography mass spectrometry (PG-CMS). The results indicated there are total37kinds of pyrolysis compounds for flax fiber treated with different scouring and bleaching under the rate of10℃/min heating at the temperature of570℃. Wherein there are four kinds of co-pyrolysis products including in carbon dioxide, propylene, ethylene oxide and beta.-D-Glucopyranose. For different processes of scouring and bleaching there are significant peaks before16min of retention times, and there are no obvious characteristic peaks after16min of retention times. While for the flax fibers treated with different bio-scouring small molecule compounds such as carbon dioxide, ethylene oxide and tri-dodecyl heterocyclic compounds and sugar compounds like DL-Arabinose were included in the pyrolysis products. As far as the samples from pilot, the pyrolysis products increase considerably for the flax fibers mentioning the crude enzyme scouring and bleaching, which including small molecules of carbon dioxide, aldehydes, ketones, alcohols, ethers, acids and esters, aldehydes and DL-Arabinose etc..(5) Structural evolution characteristics of flax fibers treated different scouring were discussed by the Small angle X-ray scattering (SAXS). A distinct scattering peak can be observed by SAXS curve for flax fibers treated by different scouring and bleaching. Besides, a meridional peak between q=0.6-0.8nm-1was also observed, possibly for the first time in cellulose fibers, and this has been attributed to a crystalline/non-crystalline repeat distance between80-108nm. It has also been noted that there is considerable change in structure as flax fibers scouring of NaOH and bleaching in industry for its smallest meridional peak value. Thus repeat distant of chemical scouring-bleaching is the longest, while it is the lowest for samples of bleaching. The repeat distance is similar to two bleaching samples of DA8bacteria scouring and both of them is87.59nm. It is similar for that of samples untreated, NaOH cooked and DA8bacteria scoured. The results show that Guinier curve goes in the small concave corners, which indicates the density of scattering system is uneven for flax fiber with different scouring. The microfibrils of similar spherical is observed for two samples of DA8bacterial scouring and traditional chemical scouring and bleaching, while the micro-fibrils of rotated ellipsoidal or long rod are observed for the other samples. The results of Porod showed that there is a positive deviation for all samples untreated and treated. Analysis indicated that the structure of the cellulose micro-fibrils is consistent with cross section thickness of approximately0.59-0.64nm after different scouring and bleaching processes, while the cross section thickness of samples with different scouring are located about0.62-0.70nm. In addition to the sample of scouring with crude enzymatic and bleaching in pilot the surface of the scattering body has a fractal structure, other treatments have mass fractal characteristics.(6) The structure evolution characteristics of flax fiber after different scouring were studied by Raman spectroscopy. The results showed that the principal peaks of cellulose for treated flax fiber with different roving methods are2897,1121,1098,378cm-1respectively. The intensitive Raman line (2897cm-1) in the range of the CH and CH2stretching vibrations. The Raman line assigned to the vibrational mode Vs(C-O-C) of the fiber cellulose at1121cm-1, while the Raman lines at1098cm-1assigned to the skeletal vibrational modes Vs(C-O-C) and Vas(C-O-C)of the β(1→4) glycosidic linkages of the P-D-glucopyranosyl units of cellulose can serve as characteristic marker bands for multi-component systems like flax fiber. The Raman lines at378cm-1assigned to the β-D-glucopyranosyl units of cellulose. Two Raman lines of cellulose have been used to calculate the intensity rations R=I1120/I1098which had turned out as a sensitive response to molecular changes of flax fibers treated with different scouring. Bleaching of bio-scoured flax fibers in0.3-0.4%of alkali concentrations causes the polymorphic transformation of cellulose Ⅰ into cellulose Ⅱ.In conclusion, it is feasible that the bioscouring was carried out under alkaline conditons for flax roving. It is helpful to extract, analyze and compare the caracteristics on the evolution of the structure and performance after different scourings by modern analytical techniques. And it can provide data support for further developing process, industrialization and mechanisms discussing of bioscouring.