An Attachment Theory for Microsphere Adhesion

A theory of the mechanics of adhesion between a microsphere and substrate is presented. When a force is applied to an elastic body, the deformation depends not only on the magnitude of the force but also its location and distribution. Molecular adhesion between bodies is a surface force localized to the contact area. In contrast, applied forces such as from gravity, flow fields, inertia, etc., are distributed over the volume (body forces) and/or surface areas. Effects of different types of force systems on deformation, particularly when these forces are combined, can influence adhesion. The Hertzian structural stiffness parameter K does not reflect the effects of differently distributed multiple forces. A theory is developed that takes into account simultaneous application of the adhesion force and applied forces through the development of a reduced stiffness, K_R. The paper also develops an equivalent Hertzian process for the condition of adhesion forces alone so that the mechanics of adhesion can be modeled completely by Hertzian theory. Illustrations of how adhesion alone is handled and how the reduced stiffness behaves are provided using experimental data from compressed, crossed rods and from hard particles in static equilibrium with both relatively hard and soft substrates.     

An Adhesion Process for Space Solar Cells

A type of silicone adhesive was used for bonding anti-irradiation cover glasses to space solar cells. A new adhesion process for solar cells was designed, and implemented by means of an automated coating and bonding system based on an industrial robot. On the basis of non-Newtonian fluid theory, flow models of three sub-processes were created, and the commercial finite element analysis code Adina was employed to simulate the whole process. The purpose of the investigation was to acknowledge the mechanism of the adhesion process and identify correlative factors that influence the adhesion quality, to provide a basis for optimization of the adhesion process. A simulation platform was created, to make it possible to evaluate or predict the adhesion quality of space solar cells when the dimensions of the solar cells and the adhesive were changed.     

An Adhesion Process for Space Solar Cells

A type of silicone adhesive was used for bonding anti-irradiation cover glasses to space solar cells. A new adhesion process for solar cells was designed, and implemented by means of an automated coating and bonding system based on an industrial robot. On the basis of non-Newtonian fluid theory, flow models of three sub-processes were created, and the commercial finite element analysis code Adina was employed to simulate the whole process. The purpose of the investigation was to acknowledge the mechanism of the adhesion process and identify correlative factors that influence the adhesion quality, to provide a basis for optimization of the adhesion process. A simulation platform was created, to make it possible to evaluate or predict the adhesion quality of space solar cells when the dimensions of the solar cells and the adhesive were changed.     

紫外光固化树脂涂料层间附着力的研究

研究了影响紫外光固化树脂涂料层间附着的结构因素及施工因素。通过调整配方、控制底漆的固化程度,能很好解决该涂料层间附着力问题     

An Improved Procedure for Determining the Work of Adhesion for Polymer-Solid Contact

Force-balance experiments in conjunction with the Johnson-Kendall-Roberts (JKR) theory have been used to determine the work of adhesion between solid systems. It has been shown that deficiencies in understanding the deformation behavior can lead to erroneous results. A modified procedure for determining the work of adhesion by force-balance experiments and JKR theory using normal displacement behavior has been introduced to address these deficiencies. This procedure involves improved experiental and data analysis protocols and has been applied to give more precise work of adhesion values for PDMS poly(dimethylsiloxane)-PDMS, PDMS-F(fluorinated silicon) and PDMS-Si (silicon) systems. The work of adhesion determinations are consistently less than those estimated by contact angle measurements.     

The Adhesion Society Award for Excellence in Adhesion Science-1994

The Adhesion Society Award for Excellence in Adhesion Science for 1994, sponsored by the 3M Company, will be presented to Professor Lawrence T. Drzal at the annual meeting of the Society at Orlando, Florida, February 21-23, 1994. Professor Drzal is Professor of Chemical Engineering and Materials Science and Mechanics, and the Director of the Composite Materials and Structures Center, Michigan State University, East Lansing, Michigan. Professor Drzal is cited in the award:     

Improved Matrix-Filler Adhesion

Enhanced matrix-filler adhesion is realized after filler treatment with a surface treatment process. The hydrosol/coupling agent treatment was applied to a wide range of inorganic and organic fillers, and adhesion to a variety of matrix resins was improved. Scanning Electron Microscopy (SEM) was used to determine the locus of failure in the filled systems. The locus of failure shows the relative degree of adhesion between the filler and the polymer matrix. Significant improvement in adhesion in humid environments is also observed.     

Adhesion of Polytetrafluoroethylene

Nucleation and crystallization of polytetrafluoroethylene in contact with gold produces a surface region of high mechanical strength in the polymer as evidenced from the strong adhesive joints prepared with a conventional epoxy adhesive. In addition, the wettability of the gold-nucleated polytetrafluoroethylene, after dissolution of the gold, is vastly improved. The critical surface tension of wetting increases from 18.5 dynes/cm to 40 dynes/cm, indicating an increase in the surface density of the gold-nucleated polymer. We conclude from this study, that the occurrence of the normal weak boundary layer on polytetrafluoroethylene is a consequence of the morphology of the surface region and is therefore influenced by the method of preparation.     

An Environmentally-Friendly Process for Bonding Aluminum Using Aqueous Metasilicate Sol-Gel and Silane Adhesion Promoters

Bonding aluminum metal and its alloys with epoxy adhesives is sensitive to process variables, particularly surface contamination and moisture exposure. In the past, several surface modification schemes have been developed to improve the epoxy-bonding of aluminum. The present work describes a simple process that produces significant improvement in strength and durability of epoxy-bonded aluminum. In this process, aluminum surfaces are first rinsed with dilute sodium metasilicate solution followed by a dilute aqueous epoxysilane solution. The combination of the two materials exhibits a bond strength synergism as measured by bondline fracture toughness. The treated aluminum surface also exhibits a significant increase in bond strength tolerance to contamination and moisture exposure. The effect of epoxysilane chemical structure on bond durability was examined, as was the role of the silicate surface treatment.     

An ASTM Standard for Quantitative Scratch Adhesion Testing of Thin, Hard Ceramic Coatings

Thin, hard ceramic coatings on metals and ceramics are extensively used for wear and abrasion resistance, friction control, corrosion resistance, and tailored functional (electrical, optical, and magnetic) properties across a wide range of high-performance applications. Coating producers and users have to measure and control the coating-substrate adhesion strength, because adhesion failure is often the primary failure mechanism of the coating, limiting its performance and life. The quantitative test method of choice for thin hard coatings is scratch adhesion testing. In this technique, a diamond stylus is drawn across the coating on the surface under increasing normal load and the damage to the coating is assessed against the applied load. With DOE funding and in coordination with the ASTM Committees C28, G08, and B02, a new scratch adhesion test standard has been researched and written and has been published. The ASTM C1624 test standard (Adhesion Strength and Mechanical Failure Modes of Ceramic Coatings by Quantitative Scratch Testing) provides comprehensive and detailed guidance and instructions on scratch adhesion testing of thin, hard ceramic coatings—the principles, terminology, applications, limitations, equipment, specimen preparation and characterization, critical experimental factors, calibration, procedures, calculations, and reporting requirements.     

涂膜附着机理与附着力促进剂的选择

介绍了涂层的附着机理;讨论了附着力促进剂的类型、选择和应用.     

增粘树脂对丙烯酸酯压敏胶性能的影响

介绍了增粘树脂与丙烯酸酯压敏胶的相容性 ,及对其压敏性能的影响     

Adhesion on Carbon-Fibre-Reinforced Plastics

The adhesion on CRFP-laminates is technically often used but the microscopic mechanisms are not yet completely understood. Besides the task to characterize the surfaces closely enough, the principal problem to predict the mechanical, physical and chemical properties of the boundary zone remains unsolved. More of less only the “try and error” method leads to the development of adhesive bonding processes, which satisfy the demands of aircraft structures concerning quality, reproducibility and durability. Experiments with varying substrates, surface pretreatments and adhesives show that all these parameters have a distinct influence on the mechanical performance of the bonds.     

Soft and Hard Adhesion

The force needed to pull a cylindrical stud from a soft elastomeric film depends on their elastic and geometric properties. For a rigid stud and a thick elastomeric film, the pull-off stress (σ) depends on the elastic modulus (E) of the film and the radius (a) of the stud as σ ～ (E/a)^1/2 (soft adhesion). However, when the film is very thin, the pull-off stress is significantly higher than the case with thick films, and its value depends on the elastic modulus and the thickness (h) of the film as σ ～ (E/h)^1/2 (hard adhesion). Here, we study the pull-off behavior of a soft cylindrical stud, one flat end of which is coated with a high modulus thin baseplate. As the flexural rigidity of this baseplate is varied, we observe the transition between the two types of adhesion. We present a simple physical interpretation of the problem, which could be of value in understanding various biofouling and adhesive situations.     

Adhesion at polypropylene-cellophane interfaces

The shear strength of bonds between isotactic polypropylene and cellophane, formed under standard conditions, has beer studied as a function of cooling rates, following bond formation, and after ageing at temperatures up to 90°C. Rapid cooling produced cohesively failing bonds with shear strengths above 20 kg/em². Weak, adhesively failing joints were produced under slow-cooling conditions. Strong bonds deteriorated when joints were aged at temperatures above 50°C, but further improvement in bond strength was observed upon ageing at lower temperatures. Experimental observations were consistent with the development of smectic structure in the polypropylene upon rapid cooling; a tendency for transcrystallization in slow-cooled joints was offset by the presence of weak boundary layers in the interface. Ageing produced further development of weak boundary layers and a transition from smectic to monoclinic crystallization in polypropylene. At higher ageing temperatures, the former effect seemed dominant; at lower temperatures, the structural change was assumed responsible for the observed improvement in bond strength.     

粉末涂料与附着力

介绍了粉末涂料成膜过程、附着机理,系统地探讨了影响附着力的因素,以及如何检测附着力与现在存在的困难.