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The UV short-wavelength/infrared excitable dual-wavelength fluorescent anti-counterfeiting polypropylene (PP) fibers were spun by the traditional melt spinning process. The effects of pH value, temperature, and solvents on the structure and properties of fibers were investigated by means of tensile tester, fluorescence spectrometer and scanning electron microscope (SEM), respectively. The results showed that the fibers could emit red light under the excitation of 254 nm wavelength UV light and emit green light under the excitation of 980 nm wavelength infrared light, which show the double anti-counterfeiting effects. The dual-wavelength fluorescent fibers showed stable mechanical properties in acid and alkali resistance, whereas the fluorescence properties of fibers decreased with the increase of processing time in acid and alkali solutions. With the extension of high temperature treatment time, the mechanical properties of fibers decreased slightly and tended to be stable, while the fluorescence performance of fibers decreased gradually. The influences of different organic solvents on the properties of fluorescent fibers were different, and the fibers showed relatively good solvent resistance.

In order to fabricate high performance artificial silk, hybrid fibers were dry spun from regenerated silk fibroin (RSF) aqueous solution mixed with graphene oxide (GO) nanosheets. The influence of draw ratio on the microstructure and mechanical properties of RSF/GO hybrid fibers was studied through Fourier transform infrared spectroscopy (FT-IR), synchrotron radiation wide-angle X-ray diffraction, Raman spectroscopy and mechanical testing. The results showed that with increasing draw ratio, both amorphous phase and mesophase of the dry-spun artificial fiber gradually converted to crystals. The orientation of crystals and mesophase changed slightly at low draw ratio, but increased significantly at draw ratios of 3 and 4X. The β-sheet content of silk fibroin and the disorder degree of GO sheets in the fibers also increased with the increase of draw ratio. The initial modulus, breaking strength and breaking energy of the hybrid fibers achieved great improvement at a draw ratio of 4X. The structure evolution of the RSF/GO hybrid fibers may benefit the understanding of the structure-property relationship of other composite fibers.

The homogenization treatment was performed to fibrillate Lyocell fiber, and then the effects of different factors including NaOH concentration, homogeneous time, temperature and bath ratio on the fibrillation degree of Lyocell fiber were investigated through the orthogonal experiment. Various characterization techniques were employed to compare the fibrillation degree of Lyocell fiber. The polarized light microscope (POM) and scanning electron microscope (SEM) were used to observe the appearance of the fiber after different treatment, and the results showed that it was a quick and efficient approach to obtain the fibrillated Lyocell fiber by homogenization treatment, and the fibrillation degree of fibers varied with different treatment conditions. The results of water retention value (WRV) and the characteristic parameter of the fibrillation degree revealed that the ranking of factors affecting the fibrillation degree of fibers was NaOH concentration > homogeneous time > temperature > bath ratio, using the extreme difference analysis and variance analysis methods. The degree of fibrillation was influenced dominantly by NaOH concentration, rather than any other three factors. By means of BET test, the specific surface area of treated fiber showed a similar trend with WRV, and they matched well with fibril amount on the fibers observed by SEM.

In order to improve the mechanical properties of poly (lactic acid) (PLA), cotton fiber/PLA composites were prepared by melting compounding and injection molding. The effects of cotton fiber content and coupling agent on mechanical properties, crystalline behavior and interface morphology of the composites were studied by universal testing machine, DSC and SEM, respectively. The results showed that the crystallinity of the composites increased gradually with the increase of cotton fiber content, whereas the mechanical properties of the composites increased firstly and then decreased with further addition of cotter fiber. The composite with 20wt% cotton fiber had an optimal mechanical performance. In addition, with the incorporation of 1wt% coupling agent, the interfacial adhesion between cotton fiber and PLA improved obviously, and the mechanical properties of the composites increased accordingly. Compared with the neat PLA, the tensile strength, flexural strength, flexural modulus and impact strength of the resultant composites were increased by 66.0%, 27.4%, 45.8% and 60.4%, respectively.

Synthesis of Poly(L-lactide) (PLLA) by the ring-opening polymerization (ROP) of L-lactides in supercritical carbon dioxide (SC-CO2) with co-solvent were studied. Effects of kinds of co-solvent on the molecular weight (MW) and the molecular weight distribution (MWD) of the resultant polymers were investigated by the gel permeation chromatography (GPC). The resultant polymers were also characterized with1H NMR,13C NMR and FT-IR. It was found that PLLA with high purity and almost without racemization could be obtained by this technology and the acetone is the best co-solvent for this kind of polymerization. By using stannous octoate as initiator and acetone as co-solvent, PLLA having a weight-average molecular weight (Mw) near to 9×104and polydispersity index (PDI) of 1.7 was successfully synthesized.

The as-spun fibers, which be produced by dry spinning technique, were treated with methanol solution. The results showed that the morphology, structure and mechanical properties of the as-spun fibers had changed. Before methanol treatment,the as-spun fiber had a smooth surface, after methanol treatment, the fiber exhibited rough surface and banded features along the fiber axis. The structure of the as-spun fibers changed from random-coil or silk I conformation to silk II conformation and the breaking intensity of the as-spun fibers were improved after methanol treatment. Compared with degummed silk fibers, the fibers treated with methanol had higher module, but the breaking elongation was lower, the fibers were still brittle.

The adsorption processes in physical vapor deposition (PVD) and alternating vapor deposition polymerization (AVDP) of organic compounds are analyzed to estimate the parameters associated with the adsorption characteristics. Observation by a simple technique using a precisely tuned quartz crystal microbalance (QCM) reveals that the first stage in the thin film formation comprises two types of adsorption, namely physisorption and chemisorption. A modified model for physisorption involving free and metastable states is proposed for the analysis of the physisorption behavior in order to estimate the average lifetime and the adsorption energy of molecules on the substrate.

The film formation mechanism during the alternating vapor deposition polymerization was studied by monitoring the change in the amount of adsorbate during the deposition. Azelaoyl dichloride (ADC) monomers can be chemisorbed onto the diaminoheptane (DAH) layer and form a mono-molecular layer with a normal molecular orientation. DAH monomers can be chemisorbed onto the ADC layer and form a multi-molecular layer on the surface of the chemisorbed DAH layer with the normal molecular orientation. Polyamide thin film with a layered structure like an Langmuir-Blodgett film was obtained by use of the alternating vapor deposition polymerization method, similar to the atomic layer epitaxy method.

Stepwise transmetalation of the neutral molecular target (µ4-O)N4 Cu4 C16(N is a monodentate pyridine) with M(NS)n transmealators (NS is a monanionic S-methyl hydrazinecarbodithioate ligand, M is Co (n = 2 or 3), Ni or Zn (n = 2)) in aprotic solvents gives a large family of heteropolymetallic products (µ4 - O)N4 (Co,Ni,Cu,Zn)4 C16 that contain from one to four different metals. Thermolysis of these solid products in flowing O2 at 220 - 250°C gives uniform, highly dispersed mixtures of the respective metal oxides. For example, thermolysis of bulk precursor (µ4 -O)N4 CoNiCuZnCl6 gives a uniform mixture of 1 - 2° particles of Co3 O4, NiO, CuO and ZnO.

Electrical Conductivity in Nylon 66 Thin Films Prepared by Alternating Vapor Deposition Polymerization