Showing papers by "Donghua University published in 2003"

Hydrophobic cotton fabric coated by a thin nanoparticulate plasma film

Abstract: The audio frequency (AC) plasma of some kind of fluorocarbon chemical was applied to deposit a nanoparticulate hydrophobic film onto a cotton fabric surface. The measurement of the video contact angle showed that the superhydrophobicity of the cotton fabric was obtained with a treatment of only 30 s. The softness, water retention, moisture regain, color retention, abrasion, friction, and permeability were thoroughly investigated by a standard method that compared the fabric with a commercial Scotchgard-protector-sprayed cotton fabric. The results showed that the textile performances of the plasma-coated fabric were superior to those of Scotchgard-sprayed samples, except for the moisture regain, which was almost the same. A post-treatment at a high temperature was conducive to increasing the hydrophobicity and the recovery of the water repellency of the plasma-coated fabric after it was washed. Atomic force microscopy images and time-of-flight secondary-ion mass spectra of plasma thin films on silicon wafers indicated that some physical and chemical changes took place during the post-treatment process. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1473–1481, 2003

Clothing Thermal Insulation During Sweating

Abstract: Heat transfer through clothing is an important topic related to thermal comfort in environmental engineering and functional clothing design. The total heat transmitted through clothing is commonly ...

Determination of limit cycles for strongly nonlinear oscillators.

Abstract: An innovative approach to finding limit cycles is proposed and illustrated on the van der Pol equation. The technique developed in this Letter is similar to the Ritz's method in variational theory. The present theory can be applied to not only weakly nonlinear equations, but also strongly nonlinear ones, and the obtained results are valid for the whole solution domain.

Effect of Atmospheric Plasma Treatment on Desizing of PVA on Cotton

Abstract: Both air/He and air/O 2/He atmospheric plasma treatments are applied to desize PVA on cotton, then PDR (percent desizing ratio) and tensile strengths of cotton fabrics and single yams are measured. XPS and SEM are used to analyze the effects of atmospheric pressure plasma treatments on PVA. These treatments can both remove some PVA sizing and significantly improve PDR by washing, especially by cold water washing. The tensile strengths of cotton fabrics treated with atmospheric pressure plasma are the same as for the unsized fabric. XPS analysis of the plasma treated PVA films reveals surface chemical changes such as chain scission and formation of polar groups, which promote the solubility of PVA in cold water. Air/O2/He plasma is more effective than air/He plasma on PVA desizing.

A New Approach for the Flocculation Mechanism of Chitosan

Abstract: A peak III/I ratio (δpeak) in pyrene-fluorescence spectrum was used to measure the polarity of microenvironment of chitosan adsorbing pyrene molecules. The authors detected the pyrene-fluorescence spectrum of chitosan with different degrees of deacetylation (DD) and determined the relationship between the flocculation of bentonite colloid and the δpeak of chitosan with a different molecular weight (MW) and DD. It can be concluded that MW rather than DD plays a key role in the flocculation and that bond bridging rather than charge neutralization dominates the flocculation with chitosan from a microenvironmental structure of view.

Delay-Dependent Robust Stability of Stochastic Uncertain Systems with Time Delay and Markovian Jump Parameters

Abstract: This paper is concerned with the delay-dependent stability for a class of stochastic uncertain systems with time delay and Markovian jump parameters. The uncertainties considered in this paper are norm-bounded and governed by the Markov process. Un like the topics in the existing literature, the stability criterion is expressed in terms of linear matrix inequalities, which can be efficiently solved by using a convex-optimization algorithm. Finally, a numerical example is given to illustrate the effectiveness of the proposed method.

Controllable preparation of patterns of aligned carbon nanotubes on metals and metal-coated silicon substrates

Abstract: Patterns and alignment of carbon nanotubes (CNTs) are particularly important for fabricating functional devices such as field emitters, scanning probes, sensors, and nanoelectronics. In this paper, the effects of various metal substrates on CNT growth are studied. Depending on the different growth mechanisms associated with the various substrate surfaces, two- or three-dimensional micropatterns of aligned carbon nanotubes have been prepared via pyrolysis of iron(II) phthalocyanine. Patterns created on silicon substrates were obtained by photolithographic techniques. The prepared CNT patterns have resolutions down to the micrometer scale. Possible growth mechanisms of aligned carbon nanotubes on different metal surfaces are also discussed.

Modeling Polymer Air Drawing in the Melt Blowing Nonwoven Process

Abstract: An air drawing model of a polymer in a melt blowing process is presented and solved by introducing the numerical computation results of the air jet flow field of the dual slot die. The model's prediction of fiber diameter tallies well with the experimental data. The effects of processing and die design parameters on fiber diameter are discussed. A lower polymer flow rate, higher initial polymer temperature, higher initial air velocity, higher initial air temperature, smaller angle between the slot and the spinneret axis, smaller width of the die head, and larger width of the slot can all yield finer fibers.

Enhancing the wash fastness of dyeings by a sol–gel process. Part 1; Direct dyes on cotton

Abstract: A series of sols were prepared from selected silane derivatives. When dyed cotton was treated with such sols, the colloidal particles linked together to form a network on the fibre. Thus the direct dye was fixed on cotton and the wash fastness was enhanced. This new method, based on the sol–gel process, was rudimentarily proved to be an effective way to improve the wash fastness of direct dyes on cotton without essential loss of properties, such as handle and strength of the fabric.

Influence of Processing Conditions on the Microstructure and Properties of Shape Memory Polyurethane Membranes

Abstract: Solution-cast films of shape memory polyurethane are investigated by Fourier trans form infrared spectroscopy, differential scanning calorimetry, dynamic mechanical anal ysis, tensile properties, water vapor permeability, and shape memory effect tests. Samples cast at higher temperatures contain more hard segments in the crystalline state and better water vapor permeability than samples cast at lower temperatures. The change in water vapor permeability of shape memory polyurethane films with respect to temperature follows an S-shaped curve, and increases abruptly at Ts, the shape memory temperature of the soft segment. The higher the modulus ratio at two specified temperatures before and after Ts, the better the shape memory behavior of shape memory polyurethane.

Linearized perturbation technique and its applications to strongly nonlinear oscillators

Abstract: A new perturbation technique called linearized perturbation method is proposed. Contrary to the traditional perturbation techniques, the unperturbed equations is obtained by linearizing the original nonlinear equation, not by setting ϵ = 0. Therefore, the obtained results are valid not only for small parameter, but also for very large values of ϵ. The present theory is processed as simple as the straightforward expansion, while omits the secular terms completely.

Nonlinear stability of the Muskat problem with capillary pressure at the free boundary

Abstract: The Muskat problem models the motion of two immiscible fluids in a porous medium. We assume that the medium occupies the exterior of a circle r = δ, that the fluids are incompressible, and that the capillary pressure at the interface is nonnegligible. We take any radially symmetric stationary solution with interface r = Rs,Rs ∞λmeimlΘ, l any integer ≥ 2. The nonlinear constraints are, under some assumptions on the solution, also necessary.

Preparation and swelling properties of solution crosslinked poly(cis‐1,4‐butadiene) gels

Abstract: Poly(cis-1,4-butadiene) (PCB) gels were prepared by the crosslinking polymerization of 4-tert-butylstyrene (tBS) and divinylbenzene (DVB) onto unvulcanized butadiene rubber with a solution polymerization technique with benzoyl peroxide (BPO) as an initiator. The effects of the reaction conditions, such as the amount of the solvent, the amount of DVB and tBS, and the initiator (BPO), on the equilibrium swelling ratio (Qe) were also investigated. The highest oil absorbencies of crosslinked gels in xylene and cyclohexane were 51.35 and 32.98 g/g, respectively. A swelling kinetic equation was proposed for this system: Qt = Qe − {Kt + [1/(Qe − Q0)]}−1, where Qt is the swelling ratio at time t, Q0 is the initial swelling ratio, and K is the swelling kinetic constant. This equation fit the experimental results quite well. The diffusion of organic solvents in PCB gels was Fickian. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2241–2245, 2003

Nucleating Efficiency of Organic Phosphates in Polypropylene

Abstract: Organic phosphates used as nucleating agents can remarkably promote the stiffness and crystallization rate of polypropylene homopolymer and ethylene–propylene copolymer. In this article, the nucleating activity of 2,2′-methylene-bis(4,6-di-tert-butylphenyl) phosphoric acid and its derivatives for isotactic polypropylene (iPP) were investigated with a differential scanning calorimeter (DSC) and polarized light microscope (PLM), and their influence on mechanical properties of polypropylene was also studied. The results showed that the sodium salt (NA7) and the glyceride ester (NA8) of the organic phosphoric acid were of high nucleating efficiency. If 0.4 wt% of NA7 or NA8 was added to PP, the crystallization peak temperature of PP was raised 15°C or 11°C, respectively, the amount of crystallinity was increased by 3 to 6%, and the crystallization rate was enhanced significantly. The nucleating activity is thermally stable when the mixture of iPP and a nucleating agent was melted and crystallized repeatedly i...

The Use of Atmospheric Pressure Plasma Treatment in Desizing PVA on Viscose Fabrics

Abstract: In this study, both air-oxygen-helium and air-helium atmospheric pressure plasma treatments were employed to desize PVA on a rayon (viscose) fabric. Both the plasma treatments were able to remove s...

Effects of sunshine UV irradiation on the tensile properties and structure of ultrahigh molecular weight polyethylene fiber

Abstract: This study investigated sunlight-simulated ultraviolet (UV) beam irradiation on the tensile properties and structure of ultrahigh molecular weight polyethylene (UHMWPE) fibers The tensile results showed that after 300 h sunlight UV irradiation, the tensile properties of the UHMWPE fibers were obviously degraded Investigation of morphology revealed that the crystallinity was slightly increased, whereas the overall orientation and molecular weight of the fibers were decreased SEM observations indicated that the degradation process was nonuniform throughout the fiber and a change from a ductile to a brittle fracture mechanism was found after UV irradiation DMA results showed two β-relaxations and one α-relaxation in the original single filament, and UV irradiation led to the increased intensity of the high-temperature β-relaxation and the lowered position of the low-temperature β-relaxation This indicated that irradiation-induced molecular scission and branching were located primarily in the amorphous and the interface areas of the fiber Changes in the thermal behavior were also examined by DSC © 2003 Wiley Periodicals, Inc J Appl Polym Sci 89: 2757–2763, 2003

Synthesis of a New-type Carbonific and Its Application in Intumescent Flame-retardant (IFR)/Polyurethane Coatings:

Abstract: This work deals in the first part, with the synthesis and characterization of a new-type carbonific. Two steps were used in the synthesis of the carbonific. Meanwhile, the structure was characterized by Fourier transform infrared spectroscopy (FTIR), magic-angle spinning nuclear magnetic resonance (MAS-NMR) 13C spectroscopy and elemental analysis. The addition of ammonium-polyphosphate (APP) and the carbonific into polyurethane (PU) varnish leads to a great improvement in its carbonization and flame-retardant (FR) performances. The second part deals with choosing the most effective combination of APP, carbonific and PU varnish. The last part deals with the evaluation of characteristic performances such as FR property, thermal stability of IFR/PU-based coatings, rheology of IFR/PU-based coating solutions and mechanical properties such as hardness, adhesion, flexibility of IFR/PU-based dry coating films.

Preparation and properties of cellulose/chitin blend fiber

Abstract: The blend solution of cellulose xanthate with chitin xanthate has excellent filtering property as an ordinary cellulose viscose. The SEM photos show that the fiber surface becomes coarse with increasing chitin content. The X-ray diffraction shows that the addition of chitin interferes with the crystallization of cellulose. The dry and wet strength and density of blend fibers decrease with increasing chitin content. The hygroscopicity of the blend staples decreases with increasing chitin content, and there exists a minimum at 3.85% chitin mass percent, while the accessibility shows the same tendency. The fiber prepared has effective bacteriostatic effects on Staphylococcus aureus, Escherchia coli, etc., and the bacteriostastic rate increases with increasing chitin content. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3430–3436, 2003

Synthesis and Anticancer Effect of Chrysin Derivatives.

Abstract: A series of chrysin derivatives, prepared by alkylation, halogenation, nitration, methylation, acetylation and trifluoromethylation, were tested in vitro against human gastric adenocarcinoma cell line (SGC-7901) and colorectal adenocarcinoma (HT-29) cells. Among these derivatives of chrysin, 5,7-dimethoxy-8-iodochrysin 3 and 8-bromo-5-hydroxy-7-methoxychrysin 11 have the strongest activities against SGC-7901 and HT-29 cells, respectively. 5,7-Dihydroxy-8-nitrochrysin 12 were found to have strong activities against both SGC-7901 and HT-29 cells.