Fibre Chemistry最新文献

The object of the study were samples of fibers obtained from ultrahigh-molecular-weight polyethylene (UHMWP) gel with different multiplicity of stretching (λ) with a scatter (dispersion) of mechanical properties. It is shown that the dependence of strength (σ_b) on breaking elongation (ε) of the studied samples is expressed by the equation σ_b = σ_b0 + K·ε and appears as a series of variously inclined straight lines specific for each λ value, which converge upon extrapolation to ε = 0 to a single point (pole), the ordinate of which coincides with the strength of unoriented fiber (σ_b0). With increase of λ the straight lines representing the course of the relationships σ_b(ε) shift toward low ε values. The decrease of ε is compensated abundantly by increase of angular coefficient K, which determines the degree of effect of ε on σ_b.

In this work, we demonstrate the possibility of obtaining elastic electrically conductive composites by aerosol application of graphite and polytetrafluoroethylene dispersions in an organic solvent on fiber materials made of natural and synthetic polymers. We observe a manyfold change of electrical resistance, as well as deformation and strain sensitivity parameters of the obtained fiber electrically conductive composites due to elongation and elastic contraction of filaments in the deformation range of 15–30 %. Laboratory prototypes of strain sensors manufactured from electrically conductive composites based on a knit fabric with a minimal electrical resistance hysteresis (less than 4 %) were tested under cyclic deformation.

Various methods for modifying fibrous composite materials for application in respiratory protective devices are discussed. The main advantages and disadvantages of absorptive materials prepared by various methods for modifying composites are enumerated. The most effective activated carbons used in respiratory protective devices and samples of absorptive materials filled by them are compared by testing. The effects of the properties of the filler and the structure of the absorptive fibrous composite materials on its characteristics are studied.

The influence of the speed of processing on a special equipment and the content of polypropylene fibers on tensile strength and porosity of modified nonwovens has been studied. The technology of processing needle-punched nowoven fabrics made from blend of fibers with different melting points on a roller calender and a special equipment has been analyzed. At fixed temperatures of the roller in the special equipment the speed of processing affects the tensile strength, but the tensile strength of the modified materials does not depend on the processing speed significantly.

The effect of the degree of impregnation of nonwoven needlepunch cloth made of poly(ethylene terephthalate) fibers of diameter 45-47 μm by synthetic elastomer latex on the water permeability of the fibrous composite material was investigated. The technological factors determining the formation of the porous structure of the composite material were identified. A composite material with a permeability 2.5 times greater than that of the starting cloth was obtained for degree of impregnation 0.09. The material was impermeable to water for degree of impregnation 0.56. The structure of composite materials and distribution of elastomer particles on the cloth were studied using electron microscopy.

The constitution is analyzed and the structural characteristics of natural and synthetic shoe felts modified by water repellents of various compositions are determined. The pattern of water repellent distribution on the fiber and in the structure of the modified materials is established. A predictive appraisal of the feasibility of use of modified felts for making parts of shoe upper is given.

A methodology for investigating the rigidity and morphology of kemp and undercoat wool fiber impregnated with a synthetic latex emulsion is investigated. Experimental data are processed according to standard methods. The fiber before and after impregnation is assessed in terms of its bending angle and fineness. The coefficients of variation that confirm the effect of impregnation effect on the angle of fiber bending are calculated.

Eco-unfriendliness of viscose process − the main producer of tire cord from wood cellulose − does not meet the growing need for creation of “green” tires. Alongside viscose cord fiber, production of a new cord fiber, Lyocell, from wood cellulose by eco-clean NMMO process is developing. Technical fibers were obtained from high-molecular flax cellulose by the method of its solid-phase dissolution in N-methylmorpholine-N-oxide. Comparative studies of the structure and mechanical and thermal properties of flax fibers and industrial cord fibers showed correspondence of their properties and that the stiffness of the flax fiber is almost 30 % higher than that of the cord fiber. Flax fibers are resistant to cyclic deformative actions and their deformation at high temperature is less than that of commercial samples. Water losses by the samples in the process of thermal studies at temperatures up to 170 °C have a reverse nature, which is confirmed by the stability of the mechanical properties of the samples under equilibrium conditions after thermal action. The obtained data set indicates sufficiently high fatigue strength of flax fibers and makes it possible to use them as cord fiber at par with cord fiber from wood cellulose.

The structure and mechanical properties of composites obtained by impregnation of fabric from blend of 0.22 and 0.66 tex fibers with aqueous dispersion of polyurethane have been studied. The process of stretching fabric and composites impregnated to different degrees has been investigated. The parameter for estimation of the resistance of the fabric and composites to stretching in the first deformation stage has been validated. The dependencies of the parameters representing stretching of the composites and of conventional breaking stress on the degree of impregnation have been obtained. The noted dependencies have an extremal form. The compositions of the composites having maximum tensile resistance under the action of conventional breaking stress have been determined.

A mathematical method for determining a catalyst surface is discussed. The bond angles in an Fe[O₂(NH₂)₃] fragment are determined. The geometry of the resulting complex is established. The effectiveness of using quantum-chemical modeling to study the active-site structure is examined.