Strengthening of polypropylene fibre

Conclusions It has been shown that elongation of polypropylene fibre at a temperature above the melting point of the unoriented polymer is accompanied not only by an increase in structure orientation, but also by formation of a denser structure, which ensures a high fibre strength.All-Union Scientific Research Institute for Synthetic Fibres (VNIIV). Translated from Khimicheskie Volokna, No. 5, pp. 12–13, September–October, 1969.     

Orientation processes in spinning man-made fibres

Conclusions The appreciable specific surface of stretched gel-fibres based on semirigid polymers increases their sorptive power, which ensures the possibility of combining fibre strengthening with inclusive fibre modification.The high activity of surfaces of the oriented polymer substrate which have been newly generated during the process of fibre formation predetermines the possibility of effecting rapidly occurring polymer-analogous transformations in making special-purpose fibres.The form of the load-elongation diagrams, which are recorded under isothermal conditions at a constant rate of deformation, depends on the spinning conditions and is determined by all the conditions of supermolecular organization of the polymer substrate.The initial fibre modulus, compliance, and porosity depend on the method and efficiency of orientation stretch of the fibre.The diversity of the regions of application of man-made fibres requires using various effects which are realizable during orientation: strength, relaxation, and sorption activity.Translated from Khimicheskie Volokna, No. 2, pp. 36–40, March–April, 1985.     

The problem of orientation strenghthening of polycaproamide fibres

It is shown that the absolute strength of PCA fibre at 291 K is almost independent of the preliminary draw ratio and the relative strength increases proportionally to the total draw ratio attained in orientation drawing and subsequent stretching at a constant rate. The values of the breaking load and total draw ratio of the oriented fibre can be lower than for the unoriented fibre. The data obtained suggest the existence of temperature-force conditions that allow significantly increasing the orientation draw ratio of PCA fibres.Translated from Khimicheskie Volokna, No. 5, pp. 20–21, September–October, 2004.     

Ultrastrong fibres fabricated by orientational crystallization from gel. A review

The methods of fabrication of ultrastrong chemical fibres from flexible-chain polymers examined in the review require use of a starting polymer with an ultrahigh-molecular-weight. Attaining ultrahigh draw ratios is a common technological condition. This is almost exclusively determined by the ratio between the deformation rate, temperature, and initial state of the polymer. Gel technology is a priority method of fabrication of ultrastrong fibres. The polyester fibres fabricated by this method attain strengths of 6–7 GPa and Young's modulus of 220–250 GPa. All ultrastrong fibres have the structure of a fibrillar crystallite with a significant fraction of KVTs. All ultrastrong fibres have a melting point 5–10°C higher than for oriented fibres and elevated technical stability with high temperatures and moderate loads.Ukrainian Scientific-Research Institute of Fibres, Kiev. Translated from Khimicheskie Volokna, No. 6, pp. 8–17, November–December, 1992.     

Untersuchungen zum Schmelz- und Strukturverhalten von Polyethylenterephthalatfasern in Luft bei 1 bar und in überkritischem CO2 bis 280 bar

A comparative study was carried out as to the influence of CO₂ on changes of the fibre structure of thermofixed and unfixed PETP multifilament and monofilament fibres in relation to pressure and temperature. To this aim measurements were carried out on the glass transition-, the pre-melting- and the melting temperature with a dynamic heat flow difference calorimeter (DDC) in air at 1 bar, as well as in CO₂ at pressures up to 280 bar. In the thermograms taken under high pressure the melting point was clearly visible, in contrast to the glass transition- and pre-melting temperatures. Owing to its hydrophobic properties, the CO₂ is capable of diffusing into the fibre where it can act as a virtual contamination to the effect that the melting point at 280 bar is lowered by 13–14°C for all PETP fibres. Measurements of the pre-melting temperature, stress-strain behaviour and shrinkage after treatment of the PETP fibres at temperatures between 80 and 200°C in air and CO₂ show that particularly in the case of non-thermofixed PETP yarns at 280 bar structural changes are brought about from temperatures as low as 80°C upwards which are attributable to partial crystallite growth in the imperfect areas of the fibre polymers. In CO₂ at 280 bar, this results in higher pre-melting temperatures, increased shrinkage and higher elasticity of the fibres in contrast to air at 1 bar at comparable treatment temperatures. In the case of thermofixed fibres these effects are, as a rule, considerably less marked.     

High-modulus,high-strength carbon fibre based on polyacrylonitrile

Conclusions -- The effect of the method of preliminary heat treatment and of the structure of fibre being subjected to boronation on the strength of high-modulus carbon fibres has been shown.-- A moreoriented structure of the fibre subjected to boronation and stress relaxation during the heat-treatment process aid in bringing about an increase in strength of high-modulus carbon fibre up to 3.0–3.5 GPa at an elastic modulus greater than 700 GPa.All-Union Scientific Research and Project-Technological Institute of Electrical Carbon Articles, Élektrougli. Translated from Khimicheskie Volokna, No. 3, pp. 29–30, May–June, 1991.     

Realization of the strength of Armos fibres with different acidity in epoxy plastics

The acidity of Armos fibres significantly affects the strength of the fibre in a microplastic as a function of the moisture content of the starting fibre. There is an optimum moisture content at which maximum realization of the fibre strength in the microplastic is attained for each fibre pH. The highest strength of the adhesive bond of Armos fibre is attained for acid fibres, and the best realization of the strength in ringshaped samples of an organoplastic is obtained for neutral fibres.All-Russian Scientific-Research Institute of Polymer Fibres, Mytishchi. Translated from Khimicheskie Volokna, No. 1, pp. 53–54, January–February, 1996.     

Production of high-strength cellulose-hydrate fibres

Conclusions The physicomechanical properties of a fibre, particularly its strength, are governed by its structure and by the orientation of the structural elements. Structure formation in precipitation of xanthate from viscose occurs in accordance with the general kinetic laws of phase transitions (formation of supersaturated solutions, formation of centres of the new phase, growth of particles of the new phase according to a linear law (if the substance is in excess) or according to a quadratic law (in the case of diffusion limitation around the centres), formation of oriented structures, and an extremal dependence of the process rate on the temperature).Increase of the zinc sulphate concentration in the coagulation bath leads to an increase in the number of structure-formation centres. The fibre formed possesses a fine fibrillar structure and good mechanical properties. The capacity of this fibre for orientation stretching depends on the structure of the freshly-formed fibre, the degree of plasticisation, and the temperature of the plasticising medium. In ordinary conditions, viscose fibre is stretched by elastic forced deformation. The authors show that in principle it is possible for freshly-formed fibre to be stretched by plastic flow at 165–170°C in an atmosphere of saturated vapor.All-Union Scientific-Research Institute for Synthetic Fibres (VNIIV). Translated from Khimicheskie Volokna, No. 4, pp. 40–45, July–August, 1969.     

Mechanical properties and microstructure of high strength concrete containing polypropylene fibres exposed to temperatures up to 200 °C

High strength concrete has been used in situations where it may be exposed to elevated temperatures. Numerous authors have shown the significant contribution of polypropylene fibre to the spalling resistance of high strength concrete. This investigation develops some important data on the mechanical properties and microstructure of high strength concrete incorporating polypropylene fibre exposed to elevated temperature up to 200 °C. When polypropylene fibre high strength concrete is heated up to 170 °C, fibres readily melt and volatilise, creating additional porosity and small channels in the concrete. DSC and TG analysis showed the temperature ranges of the decomposition reactions in the high strength concrete. SEM analysis showed supplementary pores and small channels created in the concrete due to fibre melting. Mechanical tests showed small changes in compressive strength, modulus of elasticity and splitting tensile strength that could be due to polypropylene fibre melting.     

Orientierung und Streckmechanismen in amorphen und teilkristallinen Polycarbonatfäden

Heat-stretched fibres of bisphenol-A-polycarbonate may be produced in the fully amorphous as well as in the semi-crystalline state, depending on the choice of the molecular weight of the polymer and the spinning and stretching conditions. Investigations are made as to the influence of the stretching conditions on the orientation of the amorphous regions of the semi-crystalline material and on the orientation of the fully amorphous fibres. The orientation of the fully amorphous fibres is determined by measuring the birefringence, whereas that of the amorphous regions in semi-crystalline material results from the difference in birefringence of the entire structure of the fibres and the birefringence of the crystalline regions. The latter is calculated from the factor of orientation \documentclass{article}\pagestyle{empty}\begin{document}$ \[ \text{f}_\text{k} \text{ = }\frac{1} {2}(3\overline {\cos ^2 } \text{ }\varphi −1) \] $\end{document}, which in turn is measured by wide-angle X-ray scattering. From the polarizabilities of the individual atomic bonds it was possible, on the basis of known interatomic distances and valence angles, to calculate the components of the polarizability tensor for polycarbonate. These values were used to determine the maximum birefringence of amorphous and crystalline polycarbonate. It was shown that the calculated values for birefringence, which were obtained using orientation functions determined by X-ray scattering, agreed very well indeed with those measured from the optical birefringence. Equally good agreement for the oriented filament yarns was obtained between the values for the mean angle existing between chain direction and fibre axis as determined by X-ray examination, and the results calculated from IR-dichroism. In the case of the highly stretched polycarbonate filament yarns, it was observed that, despite the rigid molecule structure, the orientation of the crystalline regions was as high as with, for example, polyethylene-terephthalate fibres. (Mean angle between chain direction and fibre axis approx. 16°). The formation of stretch-induced crystallites with fibres of higher molecular weight polycarbonate can be explained by assuming a heterogeneous stretching mechanism with necking. In the case of low molecular weight polycarbonate fibres consolidated domains of high density cannot be destroyed by heat stretching; instead, they merely slide past each other, with the result that the stretching process takes place homogeneously without initiating any crystallization.     

Effect of the conditions of spinning of polyester fibres on the longitudinal velocity gradient

The velocity gradient changes as a function of the conditions of spinning PETP, and the value can increase from several tens to hundreds of units in the order LSS (low-speed spinning)—MSS (medium-speed spinning)—HSS (high-speed spinning). A combined increase in the longitudinal velocity gradient, orientation, and relaxation time is observed with an increase in the speed of spinning PETP. It was shown that crosslinking of PETP is determined by the character of the strain in the longitudinal velocity gradient field. The features and common points of spinning of PETP monofilament and complex fibre and their cross-linking in a longitudinal velocity gradient field were determined.All-Russian Scientific-Research Institute of Synthetic Fibres, Tver'. Translated from Khimicheskie Volokna, No. 5. pp. 30–33, September–October, 1996.     

Preparation of reinforced composite yarns based on polymer mixtures

Conclusions The possibility has been demonstrated of preparing self-reinforcing composite fibres on spinning the following mixtures from the melt: polycaproamide—polyoxymethylene; copolyamide—polyoxymethylene; or an ethylene—vinylacetate copolymer—polyoxymethylene, due to the formation of ultrathin polyoxymethylene fibres in the bulk of the other polymer on flow of the mixture melt. Because of the presence of microfibres, an increase in the orientation stretch ratio of the composite fibre is observed, plus a synergistic increase in its strength and initial modulus.In articles from polymer mixtures with a well-developed interfacial layer and a strong interaction of the components in it, the maximum reinforcement will take place only at a low (up to 10%) content of the disperse phase polymer. In the absence of a strong interaction, the maximum reinforcing effect is observed when there is a predominant formation of ultrathin fibres of continuous length by the disperse phase polymer.The presence of films decreases the rise in strength and modulus of the composite fibre to a greater extent than the presence of short fibres.Translated from Khimicheskie Volokna, No. 3, pp. 35–37, May–June, 1984.     

How the limiting degree of strength of Capron threads depends on irregularities of the component fibres

Conclusions 1. We have studied how the diameter and birefringence of the oriented fibres composing standard Capron thread influence their strength.2. We found that the thread contains fibres with very high tenacities, which are obtained by stretching the finest initial fibres.Kiev Branch, All-Union Scientific-Research Institute for Man-Made Fibre (VNIIV). Translated from Khimicheskie Volkna, No. 6, pp. 11–12, November–December, 1969.     

Effect of short fibers on residual permeability and mechanical properties of hybrid fibre reinforced high strength concrete after heat exposition

Mechanical and permeability performance of fibre reinforced high strength concrete after heat exposition were evaluated in the experimental study. Cylindrical concrete specimens were exposed to heat with the rate of 10 °C/min of up to 400 °C. In order to study the effect of short fibres on residual performance of heated high strength concrete, polypropylene and steel fibres had been added into the concrete mix. The melting and vaporization of its fibre constituents were found to be responsible for the significant reduction in residual properties of polypropylene fibre reinforced high strength concrete. In terms of non-destructive measurement, UPV test was proposed as a promising initial inspection method for fire damaged concrete structure. Furthermore, the effect of hybrid fibre on the residual properties of heated fibre reinforced high strength concrete was also presented.     

Connection between diamagnetic and physicomechanical properties of fibres

Conclusions Measurement of the diamagnetic anisotropy of man-made fibres permits one, in a number of cases where fibre defectiveness does not play a decisive role, to evaluate their strength in extension.The interconnection between strength and diamagnetic anisotropy, in the general case, is caused by their identical dependence on the mean degree of molecular orientation of the fibre-forming polymer, and also on the character of the chemical bonds in the main chains.Translated from Khimicheskie Volokna, No. 6, pp. 23–24, November–December, 1989.     

Preparation of fibres modified with enzymes having milk-curdling activity and their properties

Conclusions Conditions have been found for preparing enzyme-containing fibres with milk-coagulating activity.The effect of the type of carrier fibre, the character and content of functional groups, the disposition of these with respect to the main polymer chain, and also of the enzyme concentration on the milk-coagulating activity of enzyme-containing fibres has been established.A high stability of enzymes immobilized on fibres has been shown, plus the possibility of repeated use of enzyme-containing fibres for the preparation of milk curd.Leningrad Institute of Textile and Light Industry. Translated from Khimicheskie Volokna, No. 2, pp. 11–14, March–April, 1987.     

Some features of heterophase graft polymerization on synthetic fibers from thermoplastic polymers

Conclusions A considerable effect of structural-physical properties and molecular dynamics of the polymer as a solid on the process of radical graft polymerization to fibres from thermoplastic polymers which have been spun from the melt has been found.In the case of heterophase graft polymerization of vinyl monomers to polypropylene fibre, it has been shown that orderedness of the polymer structure primarily affects the initiation stage.High kinetic parameters of heterophase graft polymerization in oriented systems from thermoplastic polymers can be realized only at temperatures which exceed the glass point of the polymer matrix.Moscow Textile Institute. Translated from Khimicheskie Volokna, No. 1, pp. 7–9, January–February, 1987.     

Some features of spinning hollow fibres from polycarbonatesiloxane melts

Conclusions The following parameters have been determined as a result of calculations: fibre tension, solidification path length, and the change along the spinning path of the following: stretching stresses, speed, radius, wall thickness, and fibre temperature.It has been shown that, with increase in take-up speed, the length of the section of fibre deformation is reduced, varying practically proportionally to the flow rate of the polymer system.Stability of the process of spinning hollow fibres from polycarbonatesiloxane melts is assured within a narrow range of stretching force.Translated from Khimicheskie Volokna, No. 3, pp. 41–43, May–June, 1989.     

Structure of carbon fibres

Conclusions -- Carbon fibres have been examined as carbon band oriented amorphous-crystalline polymers.-- Characteristic regions in the formation of the structure of carbon fibres have been established, plus the interconnection between structural parameters.-- The components of preferential orientation of carbon fibres have been marked out, and a systematization of orientation in the transverse section of fibres has been presented.-- The character of change in axial component of texture with change in treatment temperature has been given, plus the connection between it and the elasticity and strength of fibres.-- A characteristic has been proposed for evaluating the activity of the surface of carbon fibres.Combustible Minerals Institute. Translated from Khimicheskie Volokna, No. 3, pp. 26–29, May–June, 1991.     

Spectroscopic investigation of polymers dyed with fluorescent dyes — Naphthalimide derivatives

Conclusions 1. Naphthalimide derivatives are promising for the preparation of dyed and fluorescing polyamide, and especially acetate fibres. Thereupon dyeing of the fibres in bulk is a more economical and ecologically clean method than dyeing from solutions.2. The optimum dye concentration in the fibre — about 0.5% by weight — at which the fibre acquires a bright color and fluoresces intensively has been determined.Scientific Research Institute of Physical Chemistry, Moscow. Translated from Khimicheskie Volokna, No. 5, pp. 16–18, September–October, 1993.