A. V. Dedov

Mechanical and structural characteristics of needle-punched materials with the use of different needles

The feasibility of partially or completely replacing imported needles by Russian-made needles is studied. Different needles and combinations of needles were used for the stage in which additional punching is performed. It is shown that Russian-made needles can partially take the place of imported needles, but such a substitution will require closer monitoring of the depth of needle penetration.

Carbon Fibre Filled Radiation Absorbing Nonwovens

The dependence of electromagnetic radiation reflection coefficient of nonwovens on the content in them of carbon fibres cut to various lengths is studied. A technique for inserting electroconductive carbon fibres, which ensures formation of an intermediate layer of these fibres between fabrics from dielectric fibres, is described. The frequency dependence of the reflection coefficient on the intermediate layer composition and carbon fibre cut length for fabrics and multilayered materials obtained by joining fabrics is determined. It is shown that the multilayered materials are of interferential-absorptive type, but are also capable of absorbing low-frequency electromagnetic radiation.

Evaluating Models for Predicting the Air Permeability of Needle-Punched Nonwovens

An analysis is made of effective models that have been proposed for predicting the air permeability of needle-punched nonwovens in accordance with the requirements of the Russian standard. An approach that entails constructing models with a single structural parameter is suggested. The parameter can be thickness, surface density, volumetric density, or the space factor. The given approach precludes obtaining models with one correction factor. Models constructed with two correction factors make it possible to predict air permeability for certain values of the structural parameters. The optimum model uses surface density as the structural parameter.

Production of Nonwoven Needlepunched Material With Increased Stretch Resistance

We have studied the stretch resistance of needlepunched web with bicomponent fibers, as a function of processing conditions. We propose a mechanism for stretching of the web and provide a rationale for a processing method. We consider the major processing methods and perform a comparative analysis of their effectiveness. Stretch resistance depends on the combination of temperature and processing speed, and to a large extent the effectiveness of processing is determined by its speed.

Modeling the Vaporization Kinetics of a Polyvinylchloride Plasticizer

The possibility of obtaining a general model for predicting the vaporization and extraction kinetics of a polyvinylchloride plasticizer was examined. It was shown that extraction and vaporization occurred differently. The model for predicting the extraction kinetics could be used to predict the vaporization kinetics only under certain process conditions. Vaporization of plasticizers occurred in two steps with different rates. The process steps were a consequence of a non-uniform plasticizer distribution in the polymer and the formation of a surface layer with reduced plasticizer content.

Modeling of plasticizer extraction from polyvinyl chloride with vegetable oil

Based on published data, a model is proposed for predicting the rate of plasticizer extraction from polyvinyl chloride (PVC) with vegetable oil under conditions where the plasticizer flows counter to the polymer. The empirical factors of the equations are shown to be dependent on the oil temperature and plasticizer content, which widens the boundaries of use of the model under the experimental conditions. Extraction is found to cease at a specific temperature and plasticizer content. The mechanism of the process of plasticizer desorption from the PVC is studied. The problems of extraction modeling under conditions where the extractant flows counter to the polymer are discussed.

Predicting the strength of high-density needle-punched nonwovens

A study is made of the use of a model developed to predict the strength of materials after basic needle-punching and additional needle-punching. With a limit on surface density, the model adequately describes the effect of the structure of the material on its strength in the case of high needle density. The additional needle-punching increases strength in the longitudinal direction without changing the transverse strength achieved during the main needle-punching stage.

Mechanical characterisics of needle-punched materials treated with heated air

A study is made of the relationship between the deformation and strength characteristics of needle-punched materials made from a mix of polyester and bicomponent fibers and treated with heated air. This type of treatment is very effective for obtaining materials with good initial tensile strength. However, the material’s resistance to deformation is preserved with relatively little elongation. Its strength increases only in the transverse direction.