Effect of combined extrusion parameters on mechanical properties of basalt fiber-reinforced plastics based on polypropylene

Basalt fibers are efficient reinforcing fillers for polypropylene because they increase both the mechanical and the tribotechnical properties of composites. Basalt fibers can compete with traditional fillers (glass and asbestos fibers) of polypropylene with respect to technological, economic, and toxic properties. The effect of technological parameters of producing polypropylene-based basalt fiber-reinforced plastics (BFRPs) by combined extrusion on their mechanical properties has been investigated. The extrusion temperature was found to be the main parameter determining the mechanical properties of the BFRPs. With temperature growth from 180 to 240°C, the residual length of the basalt fibers in the composite, as well as the adhesive strength of the polymer-fiber system, increased, while the composite defectiveness decreased. The tensile strength and elastic modulus increased from 35 to 42 MPa and 3.2 to 4.2 GPa, respectively. At the same time, the growth in composite solidity led to its higher brittleness. Thus, a higher temperature of extrusion allows us to produce materials which can be subjected to tensile and bending loads, while the materials produced at a lower temperature of extrusion are impact stable. The effect of the gap size between the extruder body and moving disks on the mechanical properties of the BFRPs is less significant than that of temperature. An increase of the gap size from 2 to 8 mm improves the impregnation quality of the fibers, but the extruder productivity diminishes. The possibility of controling the properties of reinforced polypropylene by varying the technological parameters of combined extrusion is shown. The polypropylene-based BFRPs produced by the proposed method surpass the properties of glass and asbestos fiber-reinforced plastics.Submitted to the 10th International Conference on Mechanics of Composite Materials (Riga, April 20–23, 1998).Ukrainian State University of Chemical Technology, Dnepropetrovsk, Ukraine. Translated from Mekhanika Kompozitnykh Materialov, Vol. 33, No. 6, pp. 845–850, November–December, 1997.     

Influence of fiber structure modification on the mechanical properties of flax fiber-epoxy composites

The mechanical characteristics of flax fibers were optimized by using the NaOH treatment process to improve the properties of composite materials. Shrinkage of the fibers during this treatment had a significant effect on the structure and, as a result, on the mechanical properties of the fibers and the composites based on them. Due to the higher mechanical strength and stiffness of flax fibers after NaOH treatment under isometric conditions, the strength and stiffness of composites in general increase. Further, NaOH treatment leads to a rougher surface morphology, as shown, e.g., for jute fibers, compared with the surface of untreated fibers without improved fiber/matrix adhesion.     

Influence of technological processing parameters on the properties of carbon filled thermoplastics

The effect of processing parameters of injection molding on the mechanical and tribotechnical properties of carbon plastics based on polyacetals is investigated. The copolymer of 1,3,5-trioxane with 1,3-dioxolane is used as the polymer matrix. Hydrated cellulose Ural LO-24 carbon fibers are used as the reinforcing filler. The effect of molding temperature, pressing time, and temperature of the casting mould on the properties of carbon plastics is investigated. It has been found that for improving the mechanical properties of carbon plastics it is necessary to raise the molding temperature up to 200–210°C. Prolongation of the technological cycle leads to thermal degradation of the polymer in the cylinder of a casting machine. The mould temperature only slightly affects the composite strength properties, but lower temperatures create better conditions for polymer crystallization. As a result of our investigations, the optimal processing parameters of the above carbon plastics are determined.Ukrainian State University of Chemical Technology, Dnepropetrovsk, Ukraine. Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 3, pp. 385–392, 1999.     

Antifriction basalt-plastics based on polypropylene

A study is made of the dependence of the mechanical and friction-engineering properties of polypropylene reinforced with basalt fibers on the viscosity of the polymer matrix. It is established that the main factors that determine the mechanical properties of the plastics are the quality of impregnation of the fibers by the binder and the residual length of the reinforcing filler in the composite after extrusion and injection molding. The material that was developed has a low friction coefficient and low rate of wear within a relatively brood range of friction conditions. The basalt-plastics can be used in the rubbing parts of machines and mechanisms subjected to dry friction.Ukrainian State Chemicotechnical University, Dnepropetrovsk, Ukraine. Translated from Mekhanika Kompozitnykh Materialov,33, No. 3, pp. 417–421, May–June, 1997.     

Choice of optimal structure of glass laminates with random reinforcement. I

The effect of structural parameters — length, diameter, and distribution of the reinforcing elements — on the mechanical characteristics of glass-reinforced plastics is investigated with reference to the case of glass laminates with randomly distributed, straight, uncut glass fibers in parallel planes. It is shown that the reduced strength of these laminates as compared with unidirectional material is associated with the redistribution of the load between the fibers and the resin and the relative reduction in the number of fibers in the cross section. A formula is proposed for estimating the strength of glass-reinforced plastics with a random distribution of the fibers in parallel planes.All-Union Scientific-Research Institute of Glass-Reinforced Plastics and Glass Fiber, Moscow Region. Moscow Bauman Higher Technical College. Translated from Mekhanika Polimerov, Vol. 4, No. 6, pp. 1043–1050, November–December, 1968.     

Determination of adhesive strength in a thermoplastic-resin-thin-fiber system

Conclusion A method was developed for determining adhesive strength in thermoplastic-material—thin-fiber systems formed from a melt. Values of _o were determined for joints between PSF and PC On the one hand and high-modulus organic fibers on the other hand. We studied the dependence of the bond strength on the temperature at which the contact is formed, the area of the contact, and the condition of the surface. The adhesion of PC and PSF to organic polyamide fibers is good enough to make it unnecessary to develop adhesives or specially modify the fiber surfaces for the production of organic-fiber-reinforced plastics. The low shear strength of laminated plastics based on thermoplastic resins is evidently due to the small area of actual contact, which is in turn a consequence of the poor wetting and impregnation of the fiber filler by the melt.Translated from Mekhanika Kompozitnykh Materialov, No. 1, pp. 9–12, January–February, 1990.     

Regulation of the mechanical properties of thermoplastic carbon fiber-reinforced plastics by changing their production conditions and surface treatment of the fibers

The effect of technological parameters of processing and surface treatment of carbon fibers on the mechanical properties of carbon fiber-reinforced plastics (CFRPs) was investigated. The copolymer of 1,3,5-trioxane with 1,3-dioxolane was used as the polymer matrix, and medium-modulus hydrated cellulose Ural LO-24 carbon fibers served as the reinforcing filler. The polymer matrix was mixed with the carbon fibers by the method of combined extrusion. The dependence of the mechanical properties of CFRPs on the technological parameters of screw-disk extrusion was studied. It was found that the properties of the composites were greatly affected by the size of the working disk gap, the disk rotation rate, and the temperature in the zone of normal stresses. The surface of the carbon fibers was activated with atmospheric oxygen in the temperature range of 450–600°C, with mass loss of the fibers no greater than 3–4%. A 30–40% increase in the mechanical properties of the CFRPs was achieved. A decrease in the melt index of the 1,3,5-trioxane copolymer with 1,3-dioxolane reinforced with oxidized carbon fibers was observed, which should be taken into account in processing the composites into products. Introduction of carbon fibers in the 1,3,5-trioxane copolymer with 1,3-dioxolane allows us to increase the wear resistance and decrease the friction coefficient, which makes it possibile to use these materials in the friction units of machines and mechanisms, such as plain bearings, gears, and flange packings.Presented at the 10th International Conference on the Mechanics of Composite Materials (Riga, April 20–23, 1998).Ukrainian State University of Chemical Technology, Dnepropetrovsk, Ukraine. Translated from Mekhanika Kompozitnykh Materialov, Vol. 34, No. 5, pp. 673–682, September–October, 1998.     

Study of the effect of the dressing of carbon fibers on the properties of carbon-fiber-reinforced plastics based on polyacetals

Studies are made of the mechanical and friction engineering properties of a copolymer of trioxane-1,3,5 with dioxolan-1,3 reinforced with dressed carbon fibers based on hydrated cellulose. Polyalkyloxysilanes are used as the finishes. The optimum concentrations of the finishes on the fibrous filler are determined. Relations are obtained to describe the dependence of the mechanical properties of carbon-fiber-reinforced plastics on the type of finish and its effect on the condition of the phase boundary between filler and the polymer matrix. The effect of adhesion of the polymer to the fibrous filler on the properties of a randomly reinforced thermoplastic composite is also determined. The dependences of the friction engineering properties of polyacetal-based carbon-plastics on the loading parameters of the friction-loading unit are examined. The material that is developed has high values of strength, elastic modulus, and notch toughness and low values of the friction coefficient and shrinkage. The material can be used as structural and anti-friction elements in rocketry, aviation, and the automobile industry.Ukrainian State Chemical Engineering University, Dnepropetrovsk. Translated from Mekhanika Kompozitnykh Materialov, No. 1, pp. 90–97, January–February, 1997.     

Resistance to interlayer shear of plastics on a carbon filament base

Conclusions 1. An equation has been derived for the strength during interlayer shear along reinforcing fibers of a composite material of unidirectional texture which allows calculation of this index as a function of composition of the material and state of the interphase boundary. Experimental confirmation of this equation has shown that the effectiveness of surface treatment of the reinforcing filler can be estimated by its use.2. It has been shown that the strength during interlayer shear of an epoxy-phenol plastic can be increased by a factor of more than 3, and during bending by a factor of 1.3, as the result of treatment of high-modulus carbon fibers in nitric acid.3. A correlation has been established between changes in electrical resistivity of the carbon fiber and the molecular component of adhesion to it of consolidated epoxy-phenol binder.Moscow. Translated from Mekhanika Polimerov, No. 3, pp. 445–451, May–June, 1977.     

Anisotropy of the elastic and strength properties of reinforced plastics

The method and results of experimental investigation of anisotropy of the elastic and strength properties of reinforced plastics are discussed. A method of determining the mechanical characteristics in different directions on tubular test pieces is proposed. A special testing machine is described. It is shown that determining the strength and elastic properties of reinforced materials in directions other than the directions of reinforcing on flat test pieces cut mechanically leads to distorted results.Mekhanika Polimerov, Vol. 3, No. 3, pp. 461–466, 1967     

Modeling of the mechanical characteristics of chaotically reinforced GRP

Experimental results on the mechanical properties under tension and compression of composites based on a phenol-formaldehyde binder reinforced with short glass fibers are reported. Unidirectional structures, in which the reinforcing elements had different orientations with respect to the external load, were studied, as well as chaotically reinforced composites. In addition, the mechanical properties of the polymer matrix and of the reinforcing elements as well as the bond strength between them were also determined. An analysis of the results obtained in the tension experiments is presented, based on a model in which the frictional mechanism of interaction between the polymer matrix and the reinforcing elements is utilized. The quantitative relationships deduced give results agreeing with those obtained experimentally.     

Effect of surface modification of fibers with a polymer coating on the interlaminar shear strength of a composite and the translation of fiber strength in an F-12 aramid/epoxy composite vessel

The surface of aramid fibers was modified with a polymer coating — a surface treatment reagent containing epoxy resin. The resulting fibers were examined by using NOL tests, hydroburst tests, and the scanning electron microscopy. The modified fibers had a rougher surface than the untreated ones. The interlaminar shear strength of an aramid-fiber-reinforced epoxy composite was highest when the concentration of polymer coating system was 5%. The translation of fiber strength in an aramid/epoxy composite vessel was improved by 8%. The mechanism of the surface treatment of fibers in improving the mechanical properties of aramid/epoxy composites is discussed. Russian translation publeshed in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 6, pp. 729–738, November–December, 2006.     

Effect of surface modification on the adhesion and mechanical properties of glass-reinforced plastics

The adhesion of an epoxy-polyester resin to glass fibers with clean and modified surfaces has been determined. The effect of this adhesion on some of the properties of glass-reinforced plastics (bending, tension, shear) is investigated.Mekhanika polimerov, Vol. 1, No. 1, pp. 93–99, 1965     

The Effect of an Active Diluent on the Properties of Epoxy Resin and Unidirectional Carbon-Fiber-Reinforced Plastics

The influence of an active diluent on the properties of an epoxy matrix and carbon-fiber-reinforced plastics (CFRP) is investigated. The physicomechanical properties of an ED-20 epoxy resin modified with diglycidyl ether of diethylene glycol (DEG-1), the adhesion strength at the epoxy matrix–steel wire interface, and the mechanical properties of unidirectional CFRP are determined. The concentration of DEG-1 was varied from 0 to 50 wt.%. The properties of the matrix, the interface, and the composites are compared. It is stated that the matrix strength affects the strength of unidirectional CFRP in bending and not their strength in tension, compression, and shear. The latter fact seems somewhat unexpected. The interlaminar fracture toughness of the composites investigated correlates with the ultimate elongation of the binder. A comparison between the concentration dependences of adhesion strength and the strength of CFRP shows that the matrices utilized provide such a high interfacial strength that the strength of CFRP no longer depends on the adhesion of its constituents.     

A study of the causes of the reduced strength of glass-reinforced phenolformaldehyde plastics

A study of the curing kinetics of phenolformaldehyde resin in the presence of glass and quartz has shown that one of the chief causes of the reduced strength of glass-reinforced plastics based on phenol-formal-dehyde resin is the difference in the rate and degree of cure in layers close to the fibers and in the bulk of the resin. This is caused by the presence on the surface of the fibers of a hydrate sheath with increased concentration of hydroxyl ions and by the presence of hydrogen bonds between the oxyphenyl groups of the resin and the silanol groups on the surface of the fibers. Chemical treatment of the glass fibers has the effect of diminishing those factors responsible for the reduced rate and degree of cure, and in spite of the lower surface energy of the fibers, the strength of the glass-reinforced plastic increases.Mekhanika Polimerov, Vol. 1, No. 3. pp. 8–14, 1965     

Effects of plasma and nitric acid treatment of carbon fibers on the mechanical properties of thermoplastic polymer composites

Polyacrylonitrile-based carbon fibers were submitted to nitric acid oxidation and a dielectric barrier discharge treatment to improve the interfacial adhesion in carbon-fiber-reinforced thermoplastic polymer composites. The mechanical properties of the composites were investigated. The results obtained showed that the tensile strength of the composites improved considerably due to the treatments.     

Effect of the conditions of bond formation and destruction on the adhesion of polymers to synthetic fibers

It is shown that the adhesion of linear polymers can be measured by shearing a monofilament relative to a microblock of adhesive [1]. Experiments have been performed on polypropylene, polyethylene terephthaliate, polycaprolactam, polyvinyl alcohol, and glass fibers. Broad variation of the diameter, structure, and physicomechanical properties of the various kinds of oriented fibers had practically no effect on the adhesion. The physicochemical properties of the adhesive solutions at the moment of application to the fiber likewise do not affect the adhesion which, other things being equal, is determined by the nature and supermolecular structure of the polymers in the contact zone.Belorussian Lenin State University, Minsk. Branch of the Karpov Scientific-Research Physicochemical Institute, Obninsk. Translated from Mekhanika Polimerov, No. 6, pp. 1042–1048, November–December, 1970.     

A Study of the Relation between the Mechanical Properties and the Adhesion Level in a Laminated Packaging Material

The mechanical properties of a laminate consisting of aluminum-foil, adhesive, and polymer layers were studied in relation to the adhesion level. A special application for liquid-food packaging materials was considered. In experiments, laminates with and without adhesive layers were tested. Tensile tests were first run for every layer of the laminate, and the data obtained were then used in analyzing the results of tensile tests on the entire laminate, as well as in theoretical and finite-element calculations. Relations between different mechanical properties (such as Young's modulus, the peak stress, and the strain at the peak stress) and the adhesion level were analyzed. It was found that the tensile strength and the strain at the peak stress increased with adhesion level. Only slight differences in Young's modulus were observed at different adhesion levels.     

Strength of adhesion of epoxy polymer to carbon,glass, and steel fibers

A study has been made of the strength of adhesion of epoxy polymer to fibers of various chemical natures, and it has been shown that the magnitude of the adhesion depends not only on the nature of the fiber but also on its surface geometry. Questions are discussed on the effect of residual (internal) stresses arising during the process of heat-treating or cooling samples of bonded articles on the strength of the adhesive bond.Institute of Chemical Physics, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 1, pp. 37–42, January–February, 1974.     

Wear of glass-reinforced plastics in aggressive media

The effect of certain aggressive media on the wear of glass-reinforced plastics has been investigated. It is shown that as the angle of inclination of the glass reinforcing fibers relative to the friction surface increases, the wear of the material is sharply reduced.Ukrainian Agricultural Academy, Kiev. Translated from Mekhanika Polimerov, No. 2, pp. 364–366, March–April, 1974.