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.     

Inverse evaluation of the integral ordering of the structure and defectiveness of fibres and yarns for technical applications based on normalized values of the mechanical properties

Methods are proposed for an integral (generalized) evaluation of the degree of ordering of the structure and defectiveness of fibres based on the inverse use of indexes of their mechanical properties — modulus of elasticity and strength — normalized with respect to their maximum attainable values. These maximum attainable values are determined in defined temperature-time conditions for a defect-free polymer crystal by several methods, obtaining values in relatively good agreement. The coefficients characterizing the overall ordering and imperfection of the structure, and the defectiveness of different types of fibres based on linear (aliphatic and aromatic), laminar (carbon), and three-dimensional (silicate) polymers were estimated. Different types of fibres, including fibres of the same type, were compared with respect to the level of structural organization and defectiveness. This could serve as a measure of the perfection of the fabrication processes.St. Petersburg State University of Technology and Design. Translated from Khimicheskie Volokana, No. 5, pp. 34–41 September–October, 1996.     

Effect of thermal aging on the defectiveness of thermostable aromatic arimid and togilen fibres

The effect of thermal aging in air on the defectiveness of thermostable heteroaromatic Arimid-T and Togilen fibres was investigated based on the change in the scale dependences and coefficients of variation of the breaking characteristics: strength, elongation at break, and arbitrary deformation energy to break. The change in the scale dependences and scale coefficients of the deformation characteristics (elongation and deformation energy to break) more significantly and objectively reflect the increase in the defectiveness of thermostable fibres during thermal aging than the change in the scale dependences and scale coefficients of the strength and the coefficients of variation of the breaking characteristics. In thermal aging, the change in the defectiveness of Arimid-T fibres is smaller than for Togilen fibres. The data obtained indicate the elevated workability of thermostable heteroaromatic fibres at temperatures of 300°C: 300 h and more for Arimid-T fibres and up to 100 h for Togilen fibres.St. Petersburg State University of Design and Technology. Translated from Khimicheskie Volokna, No. 3, pp. 27–30, May–June, 1995.     

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.     

Effect of surface-treatment and moisture on realization of the strength of carbon fibres in microplates

Conclusions The coefficient of strength utilization of CF in microplates can be brought to a level which is characteristic of glass fibres.Humidifying of CF, with filling of defects of transitional and macroscopic size, reduces the coefficient of CF strength utilization.Chemical or heat-treatment of CF does not guarantee a high coefficient of strength realization if, during the course of spinning, adsorption of moisture by the fibres takes place with filling of the defects having a transition size.Published to stimulate discussion.Progress MP, Samarskii Polytechnic institute, Perm'. Translated from Khimicheskie Volokna, No. 2, pp. 30–32, March–April, 1992.     

Theory of Extremal Mechanical and Thermal Properties of Fibres and Needle Crystals. Comparison With Experimental Data

The current status of the problem of the extremal mechanical properties (modulus of elasticity, strength, thermal stability) of fibres and filamentary crystals that I elaborated over more than 50 years is presented. Two new integral energy indexes of the structure of polymers are proposed and evaluated — energy density of interatomic and intermolecular interactions, which determine many of the properties of oriented polymers and are important for predicting the mechanical properties. In addition to the theoretical modulus of elasticity and the theoretical strength of polymers (like the strength at absolute zero according to H. Mark and G. M. Bartenev), two new, practically important indexes are proposed — the maximum attainable moduli of elasticity and maximum attainable strength (in the given temperature-time conditions) are proposed. Models are developed and comparative calculations of the theoretical and maximum attainable moduli of elasticity, maximum attainable strength, and maximum thermal stability are performed with different methods for a number of linear (aliphatic and aromatic) and laminar (including carbon) structures. A comparison is made with the maximum values of the mechanical and thermal properties of the fundamental types of fibres and needle crystals based on aliphatic and aromatic polymers and materials with covalent bonds of laminar and three-dimensional structures. Oriented materials with the maximum possible properties among all of the elements of periods 2 and 3 in the Mendeleev Periodic System and their compounds — hexagonal boron nitride, graphite, and the linear carbon polymer, -carbyne, as a material with the highest modulus and strength possible in nature, are determined. New integral coefficients of completion of the structure of fibres as the ratios of the moduli of elasticity and strength attained to their maximum attainable values are proposed and evaluated. These coefficients characterize the level of the actually attained properties of oriented polymeric materials and consequently the perfection of the manufacturing technology. Ways of obtaining oriented polymeric materials with the maximum possible properties are discussed.     

Problems in preparing organoplastics based on highly oriented polyethylene fibres

Conclusions -- Some special features of epoxy organoplastics based on highly oriented polyethylene fibres have been determined, which consist in a low strength in shear, compression, or transverse extension, which are 4–6 times less than those of composites based on aramide fibres and which are caused by low adhesive interaction.-- Some basic ways of preparing monolithic polyethylene plastics have been shown, the most important of which are based on increasing the adhesive strength of fibres to the binder or by autohesive binding of the fibres.-- The possibility of preparing organoplastics of various types based on polyethylene fibres with a strength level in extension not less than 1.5 GPa, and elastic modulus up to 90–120 GPa, at a density not over 1100 kg/m³ has been confirmed.Translated from Khimicheskie Volokna, No. 4, pp. 36–39, July–August, 1990.     

Use of liquid ammonia to increase the quality of textiles made of hydrated cellulose fibres

A method was developed for preparation of samples for determining the adhesive strength of joints of thermoplastics with CF 6–9 µm in diameter by the pull-out method. The proposed method can be used to evaluate the adhesive power of thermostable thermoplastics (polyphenylene sulfide, polycarbonate, polysulfone, polyphenylene sulfide sulfone). The strength of the interface in bonds of these polymers with UKN-5000 fibres in the selected spinning conditions is sufficiently high and is as good as the adhesive strength of bonds of fibres with modified epoxy resins.Institute of Chemical Physics, Russian Academy of Sciences, Moscow; Tekhnologiya ONPP RF GNTs, Obninsk. Translated from Khimicheskie Volokna, No. 4, pp. 33–37, July–August, 1995.     

Effect of thermal aging on the defectiveness of ultrastrong para-aromatic armos and SVM fibres

The change in the defectiveness of ultrastrong para-aromatic Armos and SVM fibres during thermal aging in air was investigated based on the scale dependences and coefficients of variation of the breaking characteristics: strength, elongation, and strain energy at break. The increase in the defectiveness of ultrastrong para-aromatic fibres during thermal aging can be more objectively assessed by the change in the scale dependences and coefficients of the strain characteristics (elongation and strain energy at break) than with the change in the scale dependences and scale coefficients of the strength and the coefficients of variation of the breaking characteristics. The defectiveness of Armos fibres in thermal aging changes less significantly than for SVM fibres. The data obtained show the sufficiently high working capacity of Armos and SVM fibres in extreme temperatures — up to 300°C — for up to 10 h.Translated from Khimicheskie Volokna, No. 1, pp. 34–38, January–February, 1995.     

Determination of the strength anisotropy of oriented man-made fibres

Conclusions To investigate the transverse strength of highly oriented man-made fibres it is advisable to use the strength anisotropy method.The strength anisotropy of highly oriented fibres (Kevlar-49, Terlon, polyheteroarylene) is approximately two decimal orders of magnitude and is close to the anisotropy of the modulus of deformation.Translated from Khimicheskie Volokna, No. 3, pp. 47–48, May–June, 1983.     

Some aspects of fibre profiling in forming maximally reinforced organic resin-fibre composites

Conclusions When the profile of polyheteroarylene fibers of an initial round cross-section is trans-formed into a polygonal form, a considerable change in fibre strength takes place, associated with the extent of profiling and the final form of the fibres, at essential invariance in the elastic modulus.The change in relative area of inter-fibre contact area in a jointly profiled package of fibres has an S-shaped character, which determines the shear strength of maximally reinforced organic resin-fibre composites.An extreme dependence of strength under tension on reinforcement coefficient has been found for such composites which are based on jointly profiled fibres.Translated from Khimicheskie Volokna, No. 6, pp. 22–24, November–December, 1987.     

Process of preparing hydrocellulose fibres and films from aqueous solutions of cellulose in zinc chloride

Conclusions The possibility of preparing concentrated solutions of cellulose in zinc chloride and the properties of the concentrated solutions have been investigated.Experimental hydrocellulose fibres and films have been spun on laboratory and experimental units; these had properties close to those of ordinary viscose fibres and films, and excelled them in a number of characteristics (elastic modulus, knot strength).Translated from Khimicheskie Volokna, No. 6, pp. 6–9, November–December, 1988.     

Status and prospects for production of carbon fibres based on polyacrylonitrile

Production of PAN-based carbon fibres (CF) is a rapidly developing sector. Production in 2006 was 28,000 tons. The production capacities in 2007 increased to 55,500 tons and will attain 66,000 tons in 2008. The Japanese companies Toray, Toho, and Mitsubishi are the leaders and are responsible for 77% of total production. Toray is the leader with respect to fibre quality. The CF manufactured by the company basically have a strength of 500–560 kgf/mm². The properties of the PAN precursor are of decisive importance for the quality of the CF. Each company has its own PAN precursor plant for successfully competing. The fibre manufactured in the RF has a strength of 300–350 kgf/mm². Uglekhimvolokno NlTs has developed technology for production of CF with a strength of 450 kgf/mm². Economy in production of CF is attained by creating units (flow production lines) with individual capacity of 150–200 and even 400 tons/year (the capacity of existing domestic units is 10–20 tons/year). This increase in capacity is attained by using primarily new technical solutions, including conductive tempering of oxidized tows, separate air-oxidant and air-heat carrier circulation, making the PAN tow compact by selecting an appropriate oiling agent, and vertically positioning the carbonization furnace stack. The maximum modulus of elasticity of PAN CF is 60,000 kgf/mm². To attain high orientation and a high degree of crystallinity, boron, which decreases the temperature of transition of the fibre into the highly elastic state and thus facilitates the occurrence of orientation drawing and crystallite growth, should be used as a plasticizer. In semi-industrial conditions, when boron is added in the stage of oxidation in the form of boric acid, CF with a modulus of elasticity of 47,700 kgf/mm² are obtained. To prolong the lifetime of the graphite heaters, it is recommended that they be given a shape that allows focusing radiation on the processed fibre. Thin carbon fillers in the form of prepregs 0.04–0.17 mm thick and fabrics 0.11–0.15 mm thick are manufactured to increase the uniformity of the properties of multilayer composites. Prepregs made of “thick” PAN tow with a linear density of 3.2 ktex which are processed into CF with a strength of 500 kgf/mm², elongation of 2%, and modulus of elasticity of 23,000 kgf/mm², are the most economical. In the RF, unidirectional slivers of the Elur type 0.08 mm thick are manufactured for these purposes, but they have lower strength and due to the low processing speeds, high cost. These drawbacks have been eliminated in the semicontinuous method for manufacturing thin PAN fibres. __________ Translated from Khimicheskie Volokna, No. 1, pp. 20–26, January–February, 2008.     

Change in the Mechanical Properties of Liquid-Crystalline Thermoplastic Polymers at High Temperatures

The change in the modulus of elasticity and tensile strength of initial and heat-treated liquid-crystalline polyester fibres after annealing at a temperature 20-40°C higher than the melting point of the crystallites in the polymers was investigated. It was shown that from 50 to 90% of the initial values of the strength characteristics were preserved. In heating above the melting point of the crystallites, LC polyester fibres can melt into a monolith with preservation of elevated mechanical properties, which permits production of self-reinforced composites. The fibres melt as a result of cooperative molecular movement, and preservation of the strength indexes is ensured by the cross-links formed at high temperatures. Selection of the temperature—time conditions of heat treatment and molding is especially important for production of high-strength self-reinforced composites by melting of LC polyester fibres into a monolith.     

Mechanisms of fracture and prediction of the strength of unidirectional carbon-fibre-reinforced plastics

The principal difference in the mechanisms of fracture of unbound carbon fibres and reinforcing filler in unidirectional carbon-fibre-reinforced plastics does not allow predicting the strength of composites using Weibull distribution parameters and the average strength of the fibres on a standard testing base. An alternative approach that allows estimating the limiting strength of carbon fibres and the degree of its realization in a composite was repeatedly tested. The dependence of the strength realization coefficient of a reinforcing fibre on its volume content, the scaling effect of the strength, and the modulus of elasticity is given. The information required for predicting the strength of composites could be obtained from testing composites with a single fibre (SFC tests). __________ Translated from Khimicheskie Volokna, No. 1, pp. 51–57, January–February, 2006.     

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.     

Prediction of creep of oriented polycaproamide fibres

A method of predicting permanent creep with dynamometric curves was proposed for oriented PA-6 monofilament. The curves of the changes in the modulus of elasticity in different stretching modes were used to estimate the effect of the change in the modulus of elasticity on the deformability of the monofilament in the creep mode.Blagoveshchensk Institute of Technology. Institute of Textile and Light Industry, St. Petersburg. Translated from Khimicheskie Volokna, No. 6, pp. 38–41, November–December, 1992.     

Complex evaluation of the thermostability of aromatic fibres

The change in the mechanical properties of the aromatic fibres Armos, Arimid-T, and Togilen in heat treatment was investigated. The change in the strain properties was examined in detail for the first time: the strain modulus and strain energy causing breakage of the fibres during thermochemical aging. It was shown that the intensity of thermochemical aging, estimated by the relative change in the strength and elongation, and strain energy to break differed significantly and should be taken into consideration as a function of the conditions of use of the fibres. Of all fibres investigated, the smallest relative change in the mechanical properties was observed in Arimid-T fibre, and the most important change was observed in Armos and SHM (synthetic high-polymer material) fibres.St. Petersburg Academy of Technology and Design. Translated from Khimicheskie Volokna, No. 6, pp. 43–47, November–December, 1993.     

Structural features and strength of carbon fibres

Conclusions -- Dimensions, orientation of the ordered regions, and also the heterogeneous structure parameters have been determined for a number of foreign and domestic high-strength and high-modulus carbon fibres (CF). Characteristic features of the behavior of the heterogeneous structure of CF with change in dimensions of the ordered regions have been noted.-- It has been shown that small dimensions of the ordered and unordered regions are characteristic of high-strength CF together with an increased mean density of the unordered and porous phases.-- An attempt has been made to establish correlations between the ultimate strength of CF in extension and the heterogeneous structure parameters of the fibre.Translated from Khimicheskie Volokna, No. 1, pp. 47–49, January–February, 1991.     

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.