Quantitative Fiber Mixture Analysis by Scanning Electron Microscopy

12 - DNA analysis in the identification of animal fibers in textiles

Fibers containing both polyacrylonitrile (PAN) and cellulose acetate (CA) were prepared through wet‐spinning by using N,N‐dimethylformamide (DMF) as a solvent. Compatibility of PAN and cellulose acetate blend (PCB) fibers was investigated by means of scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and infrared (IR) spectrophotometry. The absorptive capacity and mechanical properties of the fibers were measured. It was observed that the surface and the cross section of PAN fibers were quite smooth and free from voids and microcracks, whereas cracks and voids were present on the surface and cross section of blend fibers, which increased with the incorporation of CA in the blend. Moisture regains of blend fibers were quite high while their tensile properties showed a partial decrease. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2000–2005, 2007

Sustainable reuse of fashion waste as flame-retardant mattress filing with ecofriendly chemicals

In this paper, the blend fibers of ultrahigh molecular weight polyethylene (UHMWPE) and high‐density polyethylene (HDPE) were prepared by solution blending and gel spinning process. The uniformity of the blend fibers has been confirmed by rheological data and thermodynamic unimodal curve. They were further characterized by single fiber strength test, scanning electron microscopy, wide‐angle X‐ray diffraction, small‐angle X‐ray scattering, and so forth, to explore the structural evolution mechanism with the change of UHMWPE content. The results showed that when the molar content of UHMWPE was only 2.9 mol%, entanglement appeared in the structure of shish‐kebab, and when the proportion reached 20 mol%, an interlocking structure could be observed. With the increase of UHMWPE content, kebab began to be networked, and when the content reached 33 mol%, kebab's orientation reached its peak. After that, the interlocking network structure gradually improved. When the content reached 50 mol%, the shish's orientation reached saturation, and the shish‐kebab network became perfect. In addition, with the increase of UHMWPE content, stress‐induced recrystallization occurred on the wafer, some kebab would be converted into shish crystals, and when the content exceeded 50 mol%, the microfibers began to merge, and the wafer became denser, but still had entanglements. Our work has proposed a quantitative explanation for the evolution of hierarchical crystal structure of HDPE/UHMWPE blend fibers.

The morphology and photoluminescence properties of electrospun poly(9-vinylcarbazole) (PVK)/poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) blend fibers, which were loaded with either halloysite clay nanotubes (HNTs) or an organically modified montmorillonite (OMMT) clay, were studied by scanning electron microscopy, transmission electron microscopy, and fluorescence spectroscopy. A concentration range of 0–30 wt.% was used for the clays, while the MEH-PPV concentration was fixed at 0.5 wt.%. Both clays, especially the OMMT clay, increased the phase separation of the components in the electrospun PVK/MEH-PPV blend fibers. This was attributed to their selective localization on the polymer phases. The HNTs and OMMT clay also increased energy transfer to the lowest energy states of MEH-PPV generated during electrospinning, and modified the amount of the partially overlapping conformation of carbazole groups (p-PVK) that constrained the aggregation of the PVK chains. These changes resulted in an increased emission from p-PVK, which varied depending on the type and concentration of the clay.

Nano-SiO2-coated wool fibers were prepared by coating nano SiO2 onto wool fibers pretreated by low-temperature plasma (LTP) irradiation. The morphologies and structures of coated wool fibers were characterized by scanning electron microscopy, transmission electron microscopy, and fourier transformation infrared spectrometry. The results show that after LTP irradiation, the surface structure of wool fibers was changed and new chemical bonds were formed; nano-SiO2 combined well with the wool fibers and formed a functional layer on the surface of wool fibers. Compared with parent wool, the coated wool fibers had better thermal stability, breaking strength, elongation, and frictional property.

Microplastic pollution is a growing concern for the earth’s terrestrial and marine environments. Synthetic fibers from textiles are one source of microplastic pollution as fibers may be released from garments during use and especially during laundering, whereby they may enter the aquatic environment via wastewater systems. Wool is a natural fiber, but it is often given treatments to enhance its performance, such as to make it resistant to shrinkage caused by machine washing. Treatments of this type might influence the fiber’s inherent biodegradability. We sought to understand the aquatic biodegradation behavior of wool (in its unmodified form, and chlorine-Hercosett shrink-resist treated) and a range of synthetic fibers that are used in similar clothing applications. The biodegradation test was carried out in a simulated marine environment using a natural seawater inoculant according to the ASTM D6691 method with some modifications. Biodegraded wool residues were characterized by Fourier transform infrared and energy dispersive X-ray spectroscopies. The extent of fiber damage was observed by scanning electron microscopy. Both types of wool biodegraded readily under these conditions and machine-washable wool biodegraded to a greater extent than untreated wool. Regenerated cellulosic fiber (viscose rayon) also degraded readily, but all three synthetic fibers (polyester, nylon and polypropylene) showed virtually no biodegradation. Analysis of solid and liquid residues generated by the biodegraded wool showed no evidence that the chlorine-Hercosett-treated wool generated any non-degraded residues. Based on these findings we believe that, unlike synthetics, wool fibers are very unlikely to lead to microplastic pollution in the aquatic environment.

Wool fibers pretreated with chitosan and nano chitosan and dyed with saffron red and yellow mixture as natural dye by using microwave heating method. The effect of chitosan and nano chitosan concentrations on color strength (K/S) was measured. The results indicated that, wool fibers pretreated with chitosan and nano chitosan recorded higher color strength than the untreated fibers. Fastness properties and the color yield of the dye on wool fibers were evaluated. The results indicated that color fastness to rubbing, washing and perspiration of all dyed wool fibers are excellent to good. The morphologies structure of the untreated and pretreated wool fibers were examined by scanning electron microscopy (SEM). The untreated wool fibers have a rough surface. The pretreated wool fibers were swelling compared to the untreated fibers. The diameter of the fibers increased and has smooth and even surfaces. The changes in the surface morphology due to the effect of pretreatment with chitosan and nanochitosan.The antimicrobial activity with some species of bacteria and fungi were tested. The results indicated that the pretreated fibers exhibit higher reduction percent than the untreated fibers.

Glucose oxidase is a type of enzyme that converts glucose into hydrogen peroxide and gluconic acid by enzymatic reaction. Glucose oxidase is widely used in industry; however, in the textile industry, glucose oxidase has only received academic interest. Previously, wool was bleached by some reducing agents; however, currently in industry, hydrogen peroxide dominates the bleaching of wool fibres. In this study, the effect of glucose oxidase enzyme treatment on wool merino fibres and dyeability properties was investigated. Wool fibres were treated with glucose oxidase enzyme, after which the whiteness index (Stensby) and yellowness index (ASTM D 1925 and ASTM E 313) were investigated. Scanning electron microscopy and scanning electron microscopy with energy dispersive X‐ray spectroscopy were used to identify the morphological structure of wool fibres and their atomic content. The chemical damage caused by enzyme was investigated using a fluorescence and a light microscope, and the alkali solubility (ASTM D 1283) was determined. After enzymatic treatment, the wool fibres were dyed at a 2.0% concentration with reactive dyes. Dyeability (K/S) and CIELab values were assessed with a Minolta CM 3600 D spectrophotometer (D65, 10°). The washing fastness of wool fibres was investigated according to TS EN ISO 105‐C06 (A1S).

Calcium alginate fibers and nano-silica/calcium alginate blend fibers were prepared by the mean of wet spinning at the same spinning condition. The effect of nano-particles SiO2 on the structure and properties of alginate fibers were studied via many tests. The results showed that the tenacity of blend fibers increased with the growth of the content of SiO2 ranging from 1% to 5%, however, the tenacity of fibers became worse when the content of SiO2 was more than 5%. The effect of SiO2 content on hardness and tribological properties of the calcium alginate fiber was studied. The morphologies of the fibers surfaces were examined with a Scanning Electron Microscope (SEM). The result showed that the surface of blend fibers was still smooth when the consent of SiO2 not up to 7%, the best surface was obtained when SiO2 content was 5%. The incorporation of SiO2 also affected the absorption property of alginate fiber and made it decrease with the increase of SiO2 content. The structures of calcium alginate fibers and nano-silica/calcium alginate blend fibers were studied by infrared spectrum.

Hydroxypropyl chitosan (HPCS) was synthesized from chitosan and propylene oxide under alkali conditions. It was characterized by IR spectroscopy and X‐ray diffraction (XRD). We prepared alginate/HPCS blend fibers by spinning their solution through a viscose‐type spinneret into a coagulating bath containing aqueous CaCl2 and ethanol. The structure and properties of the blend fibers were studied with the aid of IR spectroscopy, scanning electron microscopy, and XRD. The results indicate a good miscibility between alginate and HPCS because of the strong interaction of the intermolecular hydrogen bonds. The mechanical properties and water‐retention properties were also measured. The best values of the tensile strength and breaking elongation of the blend fibers were obtained when the HPCS content was 30 wt %. The water‐retention values of the blend fibers increased as the amount of HPCS increased. Antibacterial fibers, obtained by the treatment of the fibers with an aqueous solution of silver nitrate, exhibited good antibacterial activity to Staphylococcus aureus. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Fabrics marketed as flame resistant are often blends of more than one fiber. The effect of flame-resistant finishes and of heat on different fibers is not the same. A previous study compared differences in morphology of cotton and polyester fibers, and of cotton and wool fibers in two blended fabrics before and after heating. This report shows, using scanning electron microscopy (SEM), the progressive changes that occur during stages of heat stress in fibers in a triblended fabric. Samples of a cotton, polyester, and wool (60/25/15) triblend, unfinished and finished with bis[tetrakis(hydroxymethyl)phosphonium] sulfate (THPS), urea, and trimethylolmel amine, were studied before and after burning. The SEM examination compares re sponses of each fiber to heat and shows that of the treated fabrics, polyester responds first by melting, wool bubbles and flows, and the external structure of cotton is relatively unchanged. Energy dispersive x-ray analyses show the location of the flame retardant agent in cotton and wool fibers. Thermal analysis data are correlated with these struc tural changes.

Blending high content of polyhydroxyalkanoates (PHAs ≥ 30 wt.%) with polylactide (PLA) provides an effective strategy to significantly improve heat resistance of PLA fibers. However, it has proven challenging to maintain good spinnability of the PLA/PHAs blends with the high content of PHAs. In this study, a series of poly(L‐lactide) (PLLA)/poly[(R)‐3‐hydroxybutyrate‐co‐4‐hydroxybutyrate] (P34HB) blend fibers with low P34HB content (≤ 8 wt.%) is successfully fabricated with excellent spinnability. The incorporation of P34HB contributes to a substantially improved heat resistance of the PLLA/P34HB blend fibers, as evidenced by a notable reduction in boiling water shrinkage from ca. 80% to 9%. This exceptionally improved heat resistance is closely related to substantial increase in crystallinity of PLLA in the blend fibers. Specifically, the addition of low P34HB content remarkably enhances chain mobility of PLLA chains, as such reduces crystallization half‐times (t1/2) and accelerates crystallization of PLLA. In fact, the amorphous P34HB phase favors crystal growth of PLLA phase rather than heterogeneous nucleation inferred previously. These results provide a facile and effective method to produce PLLA/P34HB blend fibers with enhanced heat resistance and sound spinnability.

The best chance for an efficient bleaching of highly pigmented wool with minimum fiber damage is provided by the use of metal catalysts in mordanting step preceding peroxide bleaching. This study evaluates the catalytic effect of copper sulfate (CuSO4) in the bleaching process of pigmented wool fibers under the used condition. The effects of CuSO4 and Na4P2O7 (as a stabilizer) concentration, bleaching time and rinsing time after mordanting on yellowness index, optical and mechanical properties were investigated and the optimum conditions for each step was reported. The results showed that an excellent depigmentation with minimum fiber damage is provided by using 1 %w/v CuSO4 and subsequent rinsing for 60 min, as well as bleaching with 60 ml/l H2O2 and 7 %w/v Na4P2O7 for 15 min. The optical properties of fibers were improved after bleaching under optimum conditions compared with raw samples. The color indices revealed that the black wool fibers have turned into a pale light brown shade. The morphology and structure of wool fibers, before and after bleaching, were characterized by using optical microscopy, scanning electron microscopy (SEM), and EDAX test method.

We present single-epoch radio afterglow observations of 24 long-duration gamma-ray burst (GRB) on a timescale of >100 d after the burst. These observations trace the afterglow evolution when the blastwave has decelerated to mildly- or non-relativistic velocities and has roughly isotropized. We infer beaming-independent kinetic energies using the Sedov-Taylor self-similar solution, and find a median value for the sample of detected bursts of about 7x10^51 erg, with a 90% confidence range of 1.1x10^50-3.3x10^53 erg. Both the median and 90% confidence range are somewhat larger than the results of multi-wavelength, multi-epoch afterglow modeling (including large beaming corrections), and the distribution of beaming-corrected gamma-ray energies. This is due to bursts in our sample with only a single-frequency observation for which we can only determine an upper bound on the peak of the synchrotron spectrum. This limitation leads to a wider range of allowed energies than for bursts with a well-measured spectral peak. Our study indicates that single-epoch centimeter-band observations covering the spectral peak on a timescale of ~1 yr can provide a robust estimate of the total kinetic energy distribution with a small investment of telescope time. The substantial increase in bandwidth of the EVLA (up to 8 GHz simultaneously with full coverage at 1-40 GHz) will provide the opportunity to estimate the kinetic energy distribution of GRBs with only a few hours of data per burst.