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.     

Thermal stability of high temperature epoxy adhesives by thermogravimetric and adhesive strength measurements

The thermal degradation of two high temperature epoxy adhesives has been measured in terms of weight loss and adhesion loss and the lifetime predictions are compared for the two independent measurements of thermal degradation. Weight loss measurements were performed at high temperature under accelerated thermal aging conditions. Adhesion loss measurements were performed at lower temperatures closer to typical continuous operating temperatures. An Arrhenius relationship is validated for the thermal degradation of the epoxy adhesives, and the extent of degradation in terms of weight loss and adhesion loss is modelled with an autocatalytic rate expression. The degradation kinetic parameters and models are compared between the two thermal degradation measurements and are found to give similar predictions for the lifetime of the adhesives. In addition, the relationship between network degradation and loss of adhesive strength is discussed.     

The Influence of Combined Magnetic and Vibrowave Fields on the Thermal Conductivity and Strength of Filled Polymer Adhesives

The results of the experimental study of the effect of the combined effect of a constant magnetic field and low-frequency mechanical oscillations on the coefficient of thermal conductivity of adhesive interlayers and the shear strength of adhesive joints are presented. It is shown that the action of the combined field leads to the modification of polymer adhesives filled with nickel and iron powders, which makes it possible to make adhesive joints with higher thermal conductivity and strength properties.     

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.     

Surface Modifications Produced by N2 and O2 RF Plasma Treatment on a Synthetic Vulcanized Styrene-Butadiene Rubber

A low-pressure gas RF plasma-treatment has been used to improve the adhesion of a synthetic vulcanized rubber to polyurethane adhesive as an environmentally friendly alternative surface treatment to the conventional chemical treatments. A sulfur vulcanized styrene-butadiene rubber (R2) containing a noticeable amount of zinc stearate and paraffin wax (both providing a lack of adhesion) in its formulation was used. Two different gases (oxygen and nitrogen) were used to generate the RF plasma, which was performed at 50 Watt for 1–15 min. The modifications produced on the R2 rubber surface by the RF plasma treatments were assessed by using advancing and receding contact angle measurements, ATR-IR spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Scanning Force Microscopy (SFM), and Scanning Electron Microscopy (SEM). Adhesion evaluation was obtained from T-peel tests of joints produced between plasma treated R2 rubber and a polyurethane adhesive. The plasma treatment produced a decrease in advancing and receding contact angle values on R2 rubber, irrespective to the gas used to generate the RF plasma. The treatment with RF plasma produced the partial removal of hydrocarbon moieties from the rubber surface and the generation of oxygen moieties. An increase in surface roughness was also produced. The degree of oxidation and the amount of hydrocarbon-rich layer removed from the R2 rubber surface was more important by treating with oxygen plasma. The treatment of rubber in oxygen plasma for 1 minute was enough to noticeably increase adhesion of R2 rubber to polyurethane adhesive. However, an extended treatment (15 min.) was needed when nitrogen plasma was applied to R2 rubber. The loci of failure in the joints produced between the plasma treated R2 rubber and the polyurethane adhesive was assessed by using ATR-IR spectroscopy. A mixed failure (partially adhesional and partially cohesive failure in the rubber) in the joints produced with plasma treated R2 rubber joints was always obtained.     

Irradiation effects on thermal,surface, and physicomechanical properties of ethylene and vinyl acetate copolymer

The structural and thermal transitions for ethylene and vinyl acetate copolymer (EVA) samples irradiated by fast electrons at doses in the range of 2.5–25 Mrad were investigated by DSC and X-ray diffraction analysis. The parameters of chemical bonds in the amorphous phase of copolymer were determined. The change in the degree of crystallinity, melting temperature, and crystallite sizes before and after radiochemical modification were estimated. The obtained results were analyzed and corresponded to the physicomechanical properties of copolymers. The surface energy of copolymers before and after irradiation was defined. The strength of adhesive joints based on EVA from PET substrates and the influence of radiochemical modification of adhesive before joint formation on its strength were analyzed.     

Polymer alloy adhesive film made up of epoxy resin and aromatic polyester

Printed wiring boards (PWBs) with high wiring density such as thin multilayer PWBs and flexible PWBs requiring bonding sheets with superior thermal and adhesive properties, and must have a flat board surface. To meet these requirements, a polymer alloy adhesive film made up of epoxy resins and aromatic polyester has been developed. The crosslinking reaction between the components was utilized to improve thermal properties. The polymer alloy adhesive film demonstrates good heat resistance and adhesiveness. It features a low processing pressure of 2 MPa at 170°C and gives the board surface greater flatness, which is better for the fine wiring of PWBs.     

Investigation of peculiarities of sealant thermal degradation under conditions of high-temperature aging modes

Investigations on the relationship between the adhesive and thermal chemical properties of Viksint U-2-28NT sealant at high-temperature modes of adhesive joint aging are presented. It is shown that, under these conditions, if nonporous substrates are used, an abnormal thermal oxidative reaction takes place both in the volume of the adhesive, i.e., Viksint U-2-28NT sealant, and at the interphase boundary of the adhesive joint.     

General rules of formation of an ordered relief on a sealant fracture surface under shear loading

General rules of deformation and fracture of the elastomeric adhesive layer under external shear loads, which consist in periodic behavior of the surface relief, have been found.     

Bore making using vibration-resistant boring arbors assembled with the use of adhesive materials

An original structural design of arbor shafts has been suggested. It has been shown that the application of adhesive joints in arbor shafts provides a solution to the problem of the generation of vibrations, which lead to worsening of the quality of the surface layer of the bore, and a large tooling variety, which results in an increase in the cost and labor consumption of the workpiece.     

原位计算水分在碳/碳复合材料粘接接头的扩散系数和扩散动力学

利用X射线能谱分析 (EDX)计算出粘接层胶粘剂水分含量的增加 ,从而计算出胶粘剂粘接碳 碳复合材料湿热老化后的扩散系数和扩散动力学 ,该方法不用将仅 0 1mm厚的胶粘剂从被粘材料表面除去再进行分析 ,因此相对简单 ,与元素分析测试方法相比误差较小 .比较了碳 碳复合材料表面不同处理方法粘接接头的水分扩散系数和扩散动力学 ,表明碳 碳复合材料经偶联剂处理的耐久性能要好于化学氧化和砂纸打磨处理 .     

Electrothermomechanical analysis and its application to studying electrically conductive adhesive joints

Electrothermomechanical analysis (ETMA) is effective for studying electrically conductive adhesive joints. Post curing of an electrically conductive adhesive (silver particle filled epoxy) by heating at an elevated temperature significantly enhances the thermal and mechanical stability of the conductive adhesive joint. The contact electrical resistivity and thickness of a joint tend to decrease cycle to cycle upon thermal cycling between 30 and 50°C and upon compression (up to 0.55 MPa). The effects of compression and thermal cycling are significant in the joint without post curing, but is insignificant after post curing. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal Resistance of Carborane-Containing Polyurethane-Adhesive Systems

The influence of the structure of polyestercarboranes and a technique of introducing them into the composition of polyurethane–adhesive systems on the physico-mechanical properties and the thermal resistance of glued joints on their basis was studied. It was shown that the introduction of carborane groups into polyurethane adhesive compositions increases their thermal resistance and the level of properties of compositions containing m-carboranes is higher than that in the case of using o-carboranes. The composition of gaseous products released under the thermal decomposition of carborane-containing polyurethane systems in air and in an inert medium is given.     

Monocomponent Waterborne Polyurethane Adhesives: Influence of the Crosslinking Agent on Their Properties

To improve the properties of the monocomponent waterborne polyurethane (WPU) adhesives, a series of crosslinked WPU were prepared with trifunctional polyester polyol (P210) as crosslinking agent. The crosslinked WPU dispersions and their films were characterized by conventional methods. The adhesion property of the samples was measured from T-peel test of leather/WPU adhesive/leather joints. Compared with the linear one, the crosslinked WPU exhibited low viscosity, small particle size, and low surface tension. For crosslinked films, the thermal stability, water resistance and mechanical properties were remarkably enhanced. The experimental data of T-peel test indicated that the adhesive strength significantly increased to 4.8 KN/m by crosslinking up to the optimum crosslink index of 1.2 and then showed a small decrease with excess.     

Predicting the endurance of adhesive joints

The paper studies the causes of loss of efficiency of designs with adhesive joints and models for determining their endurance and probability of failure-free operation upon gradual and sudden failure. For the model of gradual failure, we propose a technique for assessing the maximum allowable value of the output parameter, for which the shear strength is most often used, and the rate of degradation processes of adhesive materials. Examples of calculating the endurance are given.     

Improvement in strength of the aluminium/epoxy bonding joint by modification of the interphase

This contribution describes the influence of different surface pre-treatments including self-assembly of phosphoric acid mono alkyl ester as adhesion promoter (AP) for adhesive bonding of aluminium alloy AlMg3. The investigations were performed using a cold hardening two components epoxy-adhesive. The pre-treated surfaces, the interphase structures and the joints were characterized by: SEM/EDX, surface tension, XPS, DMA and the determination of mechanical parameters. The results interestingly show that the test sample with three step pre-treatment (degreasing in acetone, then anodic oxidation in phosphoric acid and adsorption of AP) has the highest adhesive strength and durability.     

Polymer matrix of polyethylene porous films functionalized by electrical discharge plasma

The polyethylene porous films were treated by dielectric surface barrier discharge (DSBD) plasma at atmospheric pressure in oxygen (O₂) or nitrogen (N₂), and by radio-frequency discharge (RFD) plasma in air at reduced pressure 46 Pa. The surface energy of films was carried out by direct measurements of contact angles of six testing liquids. The strength of adhesive joints in the system modified polyethylene porous films - polyacrylate was measured by peeling of the joints under the angle of 90°. The significant increase of the surface energy and its polar component of polyethylene porous films modified by all types of plasma were observed. The higher strengths of adhesive joints were found for modification of polyethylene porous films by radio-frequency discharge plasma in comparison with modification of the films by barrier discharge plasma.     

The influence of polysulfones of various structures on the properties of adhesive materials

A study of a samples of polyarylsulfones and polyarylsulfidesulfones with a glass-transition point of 210–245°C as received and in the formulations of adhesive compositions has been conducted. It has been shown that the developed adhesive compositions containing polyarylsulfones are capable of forming a film and provide high strength indices of adhesive joints in shear of 23–29 MPa within a temperature range from 20 to 150°C.     

Adhesive behavior of UV pre‐treated polyolefins

The effect of surface modification of polyolefin, mainly isotactic polypropylene and low‐density polyethylene, by UV irradiation and phosphoryl chloride on its adhesive behavior was investigated. A non‐linear increase of the surface free energy, its polar component and strength of adhesive joint to more polar polymer was observed. The effect of modification of polyolefins was strongly depended on the intensity of the UV radiation. The obtained values of the strength of adhesive joints to polyvinyl acetate correspond with the measured level of hydrophilicity of modified polyolefin.     

Polydimethylsiloxane–cristobalite composite adhesive system for aerospace applications

The effect of phase‐pure cristobalite (a high temperature crystalline polymorph of silica) on the adhesive characteristics of hydroxyl terminated polydimethylsiloxane (PDMS) was studied. The potential advantages of PDMS/cristobalite composite system as an adhesive for aerospace applications are also discussed. A PDMS/cristobalite composite adhesive system containing different filler contents (0–46 volume percentage, vol%) was prepared. The filler material, phase‐pure cristobalite, was synthesized by the pyrolysis of fused silica at 1400°C. The mechanical, rheological, and thermal characteristics of the composites were studied. A high yield stress (0.151 Pa), shear‐thinning index (1.051), and fast recovery rate were observed for ～34 vol% cristobalite loading, which indicate that PDMS retains its excellent adhesive and flow characteristics even at high filler loading with enhanced mechanical characteristics. Thermal analysis shows the onset of degradation of PDMS shifts to higher temperatures, 372–438°C and 317–417°C in nitrogen and air atmosphere respectively, which shows excellent thermal stability. The residual component yields after thermal degradation of PDMS/cristobalite composite system in nitrogen and air atmosphere show different degradation mechanisms. Copyright © 2008 John Wiley & Sons, Ltd.