S. Yu. Vavilova

Improvement of polypropylene nonwoven fabric antibacterial properties by the direct fluorination

An one-step “dry” method of direct fluorination was applied to highly improve antibacterial properties of polypropylene nonwoven fabric. A treatment of polypropylene nonwoven fabric with F2/N2 mixture highly improved the barrier antibacterial properties with respect to test bacteria – Gram-positive Staphylococcus aureus (total reproduction suppression) and partially for Gram-negative Escherichia coli. A treatment with F2/N2/O2 mixture totally suppressed Candida albicans microfungus reproduction. Polypropylene nonwoven fabric tensile strength was slightly increased after fluorination.

X-Ray Analysis of Polypropylene Thread Crystallization during Spinning

The need to account for the anisotropy of compact samples pressed from ground polypropylene (PP) fibers was demonstrated during a determination of the degree of polymer crystallinity using x-ray structure analysis. The destruction of the spherical scattering symmetry of x-rays by PP fiber samples was proven to be unrelated to the polymer amorphous phase. A method for calculating the degree of crystallinity of fiber composites from the normalized intensity of the diffuse halo of the studied composites and standard powdered PP samples was proposed. It was found that the degree of spinneret drawing of PP composite threads had practically no effect on the degree of polymer crystallinity whereas the simultaneous effects of temperature and orientation factors during solid-state drawing increased the fiber crystallinity by 1.15-1.17 times with degree of drawing 4.2-5.6, which was one of the reasons for the increased thread strength.

Antimicrobial properties of polypropylene yarn modified by metal nanoparticles stabilized by polyethylene

A new approach to the creation of polypropylene fiber materials with barrier antimicrobial properties was proposed. It is based on the modification of polypropylene yarns in the process of their production by metal-containing nanoparticles with biocidal properties. Nanoparticles were used in the stabilized by polyethylene form to prevent aggregation. It has been shown that the ability of the modified yarns to inhibit the activity of pathogenic microorganisms depends on the type of metal-containing nanoparticles, the stabilizing polymer matrix, and the concentration of nanoparticles in the yarn. Nanoparticles of manganese, iron, and nickel provide a very good antimicrobial effect when exposed to Gram-positive bacteria Staphylococcus aureus and fungi of the genus Candida (Candida albicans), but lead only to a slight reduction in the number of colonies of gram-negative bacterial test strain Escherichia coli. Nanoparticles of gold and palladium have little effect on pathogenic bacteria, but have a good antimicrobial effect in contact with yeast fungi of the genus Candida (C. albicans). The antimicrobial activity of nanoparticles increases with their concentration in the polymer structure.

Modification of polypropylene filaments with metal-containing nanoparticles immobilized in a polyethylene matrix

The possibility of modifying polypropylene fibrous materials at the stage of melt spinning through the introduction of composite powders based on metal-containing nanoparticles immobilized in a high-pressure polyethylene matrix during their synthesis has been investigated. It has been shown that the use of immobilized iron-, manganese-, and nickel-containing nanoparticles as a modifier creates conditions which prevent their aggregation during the melt spinning of the polypropylene filament and ensures the retention of stability of sizes of nanoparticles. It has been established that the introduction of metal-containing nanoparticles immobilized in polyethylene into polypropylene at the stage of filament spinning yields the high uniformity of their distribution in the polypropylene filaments.

Surface characteristics of polypropylene fibrous materials modified with ultradisperse polytetrafluoroethylene

This paper is devoted to analysis of the surface properties of polypropylene fibrous materials modified during molding via introduction of polytetrafluoroethylene ultradisperse powder into polypropylene melt. It is shown that the modification changes not only the bulk, but also surface, characteristics of the fibrous material. Evidence is provided of the presence of polytetrafluoroethylene particles on the fiber surface, and its content is determined. The effect of fiber modification on its tangential resistance coefficient and its amenability to processing is considered. The effect of ultradisperse polytetrafluoroethylene introduced into polypropylene melt on the hydrophobicity of the modified fibrous material is analyzed in detail.

Polypropylene Threads Modified by Iron-Containing Nanoparticles Stabilized in Polyethylene

The production and properties of polypropylene threads modified by small amounts of iron-containing nanoparticles were studied. The nanoparticles were stabilized during the synthesis by immobilizing them in a low-density polyethylene matrix. The structure of the modified threads was examined. The strength, friction coefficients, surface electrical resistance, and antimicrobial properties of the threads were evaluated.

Modification of polypropylene fibrous materials with ultradispersed polytetrafluoroethylene

The effects of narrowly and widely dispersed fractions of ultradispersed polytetrafluoroethylene on the structures of melt-spun polypropylene fibrous materials and the ultimate tensile half-cycle characteristics of polypropylene filaments and nonwoven materials have been studied via X-ray diffraction analysis, optical microscopy, and differential scanning calorimetry. It has been shown that the addition of 1–2% ultradispersed polytetrafluoroethylene, which exists as an individual phase in polypropylene, allows a significant increase in the relative tensile stress of the filament and its elastic modulus.

The Problem of Cyclic Oligomers in Dyeing and Processing Polyester and Ways of Solving It

Approaches to reducing the content of oligomers on the surface of PET fibres are substantiated. The first one is based on reducing surface sorption of oligomers on the fibre by rational selection of textile auxiliaries for dyeing polyester fabric and creating new preparations based on them; the second consists of chemical decyclization of the oligomers by use of catalysts of ammonolysis and hydrolysis in low concentrations. A method of eliminating cyclic oligomers and unfixed dye from the surface of the dyed textile material was developed based on use of aqueous solutions of ammonia in 0.04-0.06% concentration. Technology is created for giving polyester fibres stable antistatic properties, and this significantly reduces its resistivity from 2.8·1014 to 2.68·109Ω.

Orientation Processes in Crystalline and Amorphous Regions of Polypropylene During Yarn Spinning

The influence of the spinneret draw ratio and subsequent solid-state stretching of polypropylene multifilament yarns (PMY) on changes in the orientation of crystallites and molecular chains in the polymer amorphous regions was studied using x-ray structure analysis. It was shown that crystallites and molecular chains of amorphous polypropylene (PP) became significantly more oriented already for a yarn spinneret draw ratio of 2400% and changed little if it was increased further. Additional solid-state stretching of yarns at elevated temperature had practically no effect on the orientation of PP crystallites but did halve the misorientation angle of molecular chains in the polymer amorphous regions. This phenomenon suggested that the substantial decrease of the elongation at break and increase of PMY physicomechanical parameters could be attributed to distribution of the applied load onto a larger number of continuous chains.

X-Ray Diffraction of the Supramolecular Structure of Polypropylene Yarns

We show that for orientational drawing of polypropylene multifilament yarns within the draw ratio range 4.2-5.6 at elevated temperature, we observe practically complete transition of the folded-chain lamellar crystallites to fibrillar crystallite formations of stretched chains, resulting in a significant increase in the relative breaking load for the yarns. We established that increasing the preliminary spinneret draw ratio, which considerably reduces the possibility of formation of a*-oriented folded-chain lamellae, lets us obtain stronger yarns.