The influence of the EP-0234 adhesive primer on the properties of adhesive joints made using VK-50 phenolic–rubber adhesive

Results of testing adhesive joints of D19AT aluminum alloy made with VK-50 adhesive with the use of the EP-0234 primer are presented. It was shown that the EP-0234 primer not only increases the period between the operations of anodizing and bonding of aluminum alloy samples, but also improves the strength characteristics of adhesive joints under the conditions of exposure to water, artificial tropical climate, high temperature, and overloads.     

The influence of glued-material composition on properties of adhesive joints

The behavior of adhesive joints of different steels glued together by VK-49 phenolic-organosilicon adhesive is studied at 400, 500, and 600°C for 3000 h. The relationship between steel composition and adhesive-joint resistance to the long-term affects of high temperatures is shown. The adhesive joints of 30KhGSA carbon steel are significantly superior to adhesive joints of 1Kh18N9T and EP-609 stainless steels in terms of thermal stability.     

Application of adhesion coats and systems of surface modification during gluing

Technologies of preparation for gluing of surfaces from aluminum, beryllium alloys, porous materials (glass-fiber plastics and heat-protective materials), and technologies of polyimide film, rubber, and fabric gluing are described. It is shown that the application of epoxy primer, phosphatizing (mordant) coat, VK-32-200 and VK-25 phenolic-elastomer adhesives, and adhesive sublayers and primers allows one to preserve the activity of the preliminary treated adherent surface. The modification of polypropylene and polyester fiber surfaces by the coupling agents based on silanes with the aim to improve the nonwoven fabric properties is considered.     

One-pack epoxy adhesives containing latent hardeners

The adhesive capacity of novel one-pack epoxy adhesives, which contain latent hardeners and are thermostable at 150°C, to carbon-filled and glass-reinforced plastics and aluminum alloys is studied. The heat resistance and the adhesive and cohesive characteristics of the adhesive composites developed are found to be comparable with the VK-20, VK-89, and VK-91 two-pack adhesives.     

Current-conducting adhesives developed at OAO Kompozit

Requirements for current-conducting adhesives used to assemble electric and radio products are formulated. Current-conducting adhesives presently used in Russian and foreign practice are reviewed. The main characteristics of current-conducting, hot-cured TZK-14s adhesive developed at OAO Kompozit are given. Based on preliminary testing, TZK-14s adhesive has been proposed as a substitute for VK-20 adhesive (which contains silver powder), the components of which are no longer produced in Russia.     

Assessment of strength of adhesive joints made with epoxy adhesives under the influence of different factors

The behavior of adhesive joints made with epoxy adhesives of various compositions under exposure to different climatic zones with and without a load, as well as water resistance and resistance to thermal aging, is considered.     

Contribution of relaxation processes to adhesive-joint strength of viscoelastic polymers

Relaxation processes accompany all stages of the lifetime of viscoelastic pressure-sensitive polymer adhesives, which can form strong adhesive joints with substrates of various chemical natures under application of a slight external pressure to the adhesive film for a few seconds. This review deals with comparison of the adhesion and relaxation properties of a number of typical pressure-sensitive adhesives based on polyisobutylene, butyl rubber, styrene-isoprene-styrene triblock copolymers, alkyl acrylate copolymers, and silicone adhesives as well as pressure-sensitive adhesives based on blends of high-molecular-mass polyvinylpyrrolidone with oligomeric poly(ethylene glycol). Within all three stages of the lifetime of adhesive joints (under adhesive-bond-forming pressure, upon withdrawal of contact pressure in the course of relaxation of the adhesive material, and under the force detaching an adhesive film from the substrate surface), the strength of adhesive joints has been shown to be controlled by large-scale relaxation processes, which are characterized by long relaxation times in the range 150–800 s. All examined pressure-sensitive adhesives can be arbitrarily divided into two groups. The first group is composed of fluid adhesives that relax comparatively fast and exhibit no residual (unrelaxed) stress. The second group includes elastic adhesives capable storing mechanical energy in the course of deformation that are characterized by appreciably longer relaxation times and display residual stress after relaxation. Conditions of adhesive debonding (e.g., strain amplitude and deformation velocity) significantly affect the relaxation process.     

Structural organoplastics based on film adhesives

The use of VK-36RT film adhesive as a polymer bonding agent for producing structural hermetic organoplastics and VK-3 film adhesive for creating organoplastics with high shock and ballistic resistance for producing protective structures for aerotechnic purposes was considered.     

Criteria for the evaluation of strength characteristics of composites working in large-sized honeycomb structures

The results of determining the criterion of the working capacity of a five-ply structure of a glass-reinforced plastic fairing of a DRLOA-50 aircraft are reported. As a result of the performed accelerated climatic tests, it is revealed that, for the glass-reinforced plastic honeycomb structure of the fairing wall, the most sensitive characteristic to aging processes and the action of service and climatic factors is the tensile strength of the adhesive joint prepared with VK-36RD film adhesive. The range of admissible values of this and other strength characteristics of the composite constituting the wall of a large-scale fairing are additionally revealed.     

In Vitro and In Vivo Characterization of Biodegradable Reactive Isocyanate‐Terminated Three‐Armed‐ and Hyperbranched Block Copolymeric Tissue Adhesives

Tissue adhesives are an attractive class of biomaterials, which can serve as a treatment for meniscus tears. In this study, physicochemical and adhesive properties of novel biodegradable three‐armed‐ and hyperbranched block copolymeric adhesives are evaluated. Additionally, their degradation in vitro and in vivo, and the tissue reaction after subcutaneous injection in rats are assessed. The developed adhesives have sufficient adhesive strength to meniscus tissue after curing (66–88 kPa). Networks based on the three‐armed adhesive have tensile properties that are in the same range as human meniscus. After 26 weeks, networks based on the hyperbranched adhesive show a faster mass loss (25.4%) compared to networks prepared from the three‐armed ones (5.5%). Both adhesives induce an inflammatory reaction, however, no necrosis and only initial toxic effects on peripheral tissues are observed. The proposed materials are suitable candidates for the use as resorbable tissue adhesives for meniscus repair.     

Thermal behavior and dismantlability of adhesives containing various inorganic salts

As a fundamental study on the development of dismantlable adhesives containing chemically reactive materials, the thermal behavior and dismantlability of an epoxy adhesive containing one of the twenty-seven inorganic salts (chlorides, perchlorates, and nitrates) were observed. In the thermal behavior measured by the differential scanning calorimetry, epoxy adhesives with inorganic salts containing iron, copper, zinc, and aluminum cations released heats of reaction at lower temperatures than the adhesive alone or the adhesives with other inorganic salts. Since such inorganic salts were considered to be effective candidates as fillers in dismantlable adhesives, the adhesion strengths of their mixtures with the adhesive were observed after heat aging at 270 °C for 30 min. The results showed that both chloride and perchlorate salts specifically decreased the adhesion strength after heating. On the other hand, the effect of nitrate salts on the decrease in adhesion strength was low in comparison with the chloride and perchlorate salts.     

Problems of the reliability of machines with adhesive joints

Considered are reliability factors (nonfailure life, working life, repairability, and storage ability) for adhesive joints and constructions, for the assembly of which several different grades of adhesives and sealants are used. It is shown that, upon the calculation of adhesive joints, it is feasible to use the model of gradual failures. Parameters characterizing the strength of adhesive joint, its hermeticity, modulus of rigidity, etc. can be used as output parameters.     

A bonded–riveted technique of fabrication and machine maintenance using hot-melt adhesives

Results of mechanical tests of bonded–riveted joints using two types of adhesives represented by epoxy adhesive and hot-melt adhesives derived from ethylene vinyl acetate are given. Removal time of bonded–riveted joints is evaluated and elastic characteristics of the employed adhesive materials are measured. It is shown that the use of hot-melt adhesives is more processable, because it provides the removal of riveted connections in short period without mechanical damages.     

Adhesion and tack of polymers: Influence of mechanical properties and surface tensions

The adhesion of various polymers used as model adhesives, polyisobutylene, polyacrylates etc. has been investigated by means of an apparatus measuring the adhesive failure energyw in dependence on contact time, contact pressure, rate of separation, and temperature. The adhesive failure energy of adhesive joints formed with low contact pressure during a short contact time is called tack. After a sufficiently long contact time and with a high bonding pressure an adhesive joint exhibits its maximum energy of separationw _m .The viscoelastic properties of the model adhesives were characterized by creep experiments in dependence on time and temperature. The surface tension of the polymer adhesives and adherents could be determined by contact angle measurements. Adhesion measurements of polyisobutylene on a number of adherents were carried out in air and in various liquids in order to obtain information about the influence of surface tension on tack and maximum adhesive failure energy. w _m can be written as the product of two terms: the thermodynamic work of adhesionW _A which is related to the surface and interfacial tensions of adhesive and adherent and a dimensionless function dependent on temperature and rate of separation which describes the viscoeleastic properties of the adhesive and which obeys the rate-temperature superposition principle known from linear viscoelasticity. The tack is related to incomplete bond formation and cannot be described in the same manner. It is, however, strongly dependent on the viscoelastic properties of the adhesive showing a maximum at about 50 to 70 °C above the glass transition temperature. It is, moreover, influenced by the compliance in the plateau range above the glass transition which is determined by the entanglement network of the polymer. Wetting of the adherent by the adhesive is a further important condition for high tack values which is fulfilled if the adherent has a higher surface tension than the adhesive.     

Properties of adhesives and adhesive materials used in aviation industry

Methods for developing adhesives and adhesive material used in the structures of almost all units of aviation machinery are described step by step. The properties of high-strength film-forming adhesives; adhesive prepregs; sandwich-type aluminum-polymer materials (SIALs); cold- and hot-setting adhesives intended for gluing metals, different nonmetallic materials, and combined joints; and self-adhesive film materials of ZPPK and FAS grades are given. It is also shown where and for which purposes these adhesives are applied.     

A study of epoxide–polysulfone polymer systems for high-strength adhesives of aviation purpose

The influence of polysulfones with different structures on rheological and strength characteristics of epoxide adhesive compositions was studied. A scientific approach to developing high-strength epoxidepolysulfone adhesives that provide operational reliability of adhesive joints in the design of aviation-equipment products was shown.     

Properties of solvent based polyurethane adhesives containing fumed silicas

Five hydrophilic and two hydrophobic fumed silicas of different surface area and particle size were added to solvent based polyurethane adhesives. Silica addition produced a noticeable increase in the adhesive viscosity, imparted negative thixotropy, increased the storage modulus (G') and improved the green adhesion of chlorinated rubber/PU adhesive/chlorinated rubber joints. Those modifications were more pronounced in the adhesives which contain hydrophilic silicas.