Adhesion design for

One of the newer developments in adhesives is the growing use of ultraviolet light or electron beam radiation to cure adhesives. Adhesives designed for UV- or E-beam curing are usually pressure sensitive or hot-melt systems based on acrylates, functional rubbers, or epoxidized rubbers, and use special UV or EB lamps to provide the cure. These systems can provide greatiy improved heat resistance compared to hot melts, and avoid the soivent emission problems of some of the solvent-based systems with which they compete. 

Table 5.25 Two-part methacrylate adhesives designed for structural bonding...

A primerless adhesive designed for heat fixture or radio frequency cure assembly, whilst also offering long bondable open times at room temperature. Ideal for high performance composites, including automotive and personal watercraft assembly. 

Some of the insulating fillers found in the first row of Table 5.19 are used in foams and adhesives designed for insulation in modem appliances. ... 

Minimum and maximum service temperatures. Many formulations perform satisfactorily at temperatures ranging from -10°F to +150°F. However, if the application requires performance at temperatures that will exceed 200°F, there is no point in evaluating adhesives designed for performance in these lower ranges. Extreme cold temperatures, -30°F. and colder, pose an added problem in that many formulations become very brittle at these temperatures. Also a consideration is whether exposure to the upper and lower temperature limits is to be at a sustained rate or intermittent on a cyclical basis. 

Installation for Ultrasonic Testing AKV-S is designed for testing of diesel motors pistons. Particularly, this device identifies the areas with cracks and lowered adhesion on interfacial boundary between niresist ring and base material. 

Equation X-17 was stated in qualitative form by Young in 1805 [30], and we will follow its designation as Young s equation. The equivalent equation, Eq. X-19, was stated in algebraic form by Dupre in 1869 [31], along with the definition of work of adhesion. An alternative designation for both equations, which are really the same, is that of the Young and Dupre equation (see Ref. 32 for an emphatic dissent). 

Fig. 31. An acrylic terpolymer designed for chemically amplified resist applications. The properties each monomer contributes to the final polymeric stmcture are for MMA, PAG solubility, low shrinkage, adhesion and mechanical, strength for TBMA acid-cataly2ed deprotection and for MMA, aqueous...

The Hercules viscometer was originally designed for paper and paperboard coatings, but its use has been extended to paints, adhesives, mineral slurries, emulsions, and starch solutions. The iastmment, noted for being robust and rehable, is particularly well suited for quaUty control and product formulation. It is capable of measuting viscosity over a moderate range 1-10 mPa-s) up to high shear rates (115,000 ). A more recent model is the... 

Rheometric Scientific markets several devices designed for characterizing viscoelastic fluids. These instmments measure the response of a Hquid to sinusoidal oscillatory motion to determine dynamic viscosity as well as storage and loss moduH. The Rheometric Scientific line includes a fluids spectrometer (RFS-II), a dynamic spectrometer (RDS-7700 series II), and a mechanical spectrometer (RMS-800). The fluids spectrometer is designed for fairly low viscosity materials. The dynamic spectrometer can be used to test soHds, melts, and Hquids at frequencies from 10 to 500 rad/s and as a function of strain ampHtude and temperature. It is a stripped down version of the extremely versatile mechanical spectrometer, which is both a dynamic viscometer and a dynamic mechanical testing device. The RMS-800 can carry out measurements under rotational shear, oscillatory shear, torsional motion, and tension compression, as well as normal stress measurements. Step strain, creep, and creep recovery modes are also available. It is used on a wide range of materials, including adhesives, pastes, mbber, and plastics. 

Bond and Adhesion (ASTM D1191). This test, designed for use on crack and joint sealers, is used primarily to determine whether a jointing material possesses an arbitrary amount of bonding strength at low temperatures where pordand cement concrete is being used. 

The type of chloroprene polymers used is perhaps best illustrated by the variety of special products, designed for adhesive appHcations, that Du Pont has developed. These are described ia Table 8. Standard polymer grades are also often used, especially to modify adhesive properties and to reduce cost. 

Type AD-G is used in an entirely different sort of formulation. The polymer is designed for graft polymerisation with methyl methacrylate. Typically, equal amounts of AD-G and methyl methacrylate are dissolved together in toluene, and the reaction driven to completion with a free-radical catalyst, such as bensoyl peroxide. The graft polymer is usually mixed with an isocyanate just prior to use. It is not normally compounded with resin. The resulting adhesive has very good adhesion to plasticised vinyl, EVA sponge, thermoplastic mbber, and other difficult to bond substrates, and is of particular importance to the shoe industry (42,43). 

Current usage is almost entirely associated with the good adhesion to aluminium. Specific applications include the bonding of aluminium foil to plastics films, as the adhesive layer between aluminium foil and polyethylene in multilayer extrusion-laminated non-lead toothpaste tubes and in coated aluminium foil pouches. Grades have more recently become available for manufacture by blown film processes designed for use in skin packaging applications. Such materials are said to comply with FDA regulations. 

One key consideration in developing radiation curable adhesive systems is the thermal stability and volatility of any photoinitiators used. These chemicals are designed for liquid systems where these issues do not arise. Few of the commercial photoinitiators have adequate thermal stability at the highest hot melt temperatures (180-200°C) and many are too volatile. Reduced application temperatures and special antioxidant packages are often required. 

Because most plastic bottles are recycled, it is necessary to separate the label and adhesive from the bottle. The label is contaminated with ink and not recyclable. The adhesive is also not recycled. Ideally the adhesive will stick tenaciously to the film, but release cleanly from the bottle during the recycling operation. Adhesives designed to aid in recycling have been developed for this market. They incorporate conventional surfactants in place of some or all of the oil in PSA compositions [69] or use ingredients such as rosin which when neutralized by base can function as surfactants. A goal of the recycling industry is to eliminate the need to use base in the process. 

There are, of course, many more aspects of composite hardware design that differ from metallic bonded structure but do not necessarily involve adhesive bonding. For instance there are many types of reinforcement tape and fabric to choose from, the orientation of the plies must be chosen, the ply stackups must be balanced to avoid part warping after cure, a minimum number of plies must be used to prevent non-visible impact damage that significantly affects the load carrying capability of the part, etc. 

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