POLYMER APPLICATIONS ADHESIVES

Manuelli, A. Knobloch, A. Bernds, A. Clemens, W. 2002. Applicability of coating techniques for the production of organic field effect transistors. 2nd International IEEE Conference on Polymers and Adhesives in Microelectronics and Photonics, POLYTRONIC 2002. pp. 201-204. 

Adhesives are used in everyday applications. Adhesives may be in liquid form or thick pastes. Their main mechanism is based on the polymerization or crosslinking of polymers, which gives rise to glue or other adhesive application. The degree of adhesion of such a process is determined by conventional technological tests. 

The benefits demonstrated from the preservative use of Bronopol alone and in combination with other preservatives have been realised in several other application fields, namely polymer dispersions, adhesives, paper coatings and water-based paints. By way of example, the results of a study in a water-based paint system are reported, where Bronopol is evaluated alone and in combination with 2,2-dibromodicyanobutane (DBDCB). 

Much attention has been paid to the synthesis of fluorine-containing condensation polymers because of their unique properties (43) and different classes of polymers including polyethers, polyesters, polycarbonates, polyamides, polyurethanes, polyimides, polybenzimidazoles, and epoxy prepolymers containing pendent or backbone-incorporated bis-trifluoromethyl groups have been developed. These polymers exhibit promise as film formers, gas separation membranes, seals, soluble polymers, coatings, adhesives, and in other high temperature applications (103,104). Such polymers show increased solubility, glass-transition temperature, flame resistance, thermal stability, oxidation and environmental stability, decreased color, crystallinity, dielectric constant, and water absorption. 

Suspension Polymerization. The suspension or pearl polymerization process has been used to prepare polymers for adhesive and coaling applications and for conversion to poly(vinyl alcohol). Suspension polymerization are carried out with monomer-soiubie initiators predominantly, with low levels of stabilizers Continuous tubular polymerization of vinyl acetate in suspension yields stable dispersions of beads with narrow particle size distributions at high yields. 

Suspension Polymerization. At very low levels of stabilizer, eg, 0.1 wt %, the polymer does not form a creamy dispersion that stays indefinitely suspended in the aqueous phase but forms small beads that settle and may be easily separated by filtration (qv) (69). This suspension or pead polymerization process has been used to prepare polymers for adhesive and coating applications and for conversion to poly (vinyl alcohol). Products in bead form are available from several commercial suppliers of PVAc resins. Suspension polymerizations are carried out with monomer-soluble initiators predominandy, with low levels of stabilizers. Suspension copolymerization processes for the production of vinyl acetate—ethylene bead products have been described and the properties of the copolymers determined (70). Continuous tubular polymerization of vinyl acetate in suspension (71,72) yields stable dispersions of beads with narrow particle size distributions at high yields. 

In this respect, the most important future application of lignin will be as a natural plastic in the field of general polymer applications, especially as adhesives for wood composites. 

Modified Polymers. Future applications of carbohydrate polymers or oligomers derived from these polymers as adhesives will depend on modifying the polymer provided by nature to give a component that can undergo further crosslinking to form adhesive materials. 

Another approach to 3D integration is to use wafer bonding to stack die before singulation this approach is referred to as wafer-level 3D. There have been a variety of approaches to wafer-level 3D that have been demonstrated, which can be categorized by the wafer-bonding approach used oxide-to-oxide, copper-to-copper, polymer-to-polymer (or adhesive bonding), and mixtures of these approaches (such as redistribution layer bonding). Each of these four approaches will be introduced in this section, with emphasis placed on their application to 3D. The bond unit processes are described further in Section 15.4.2, and their associated CMP issues are discussed in detail in Section 15.5. 

The polymer particle size in latexes is far too small to he effective for adhesive applications. Therefore, many of these very tiny budding Uocks must coalesce through the diffusion adhesion mechanism to provide an optimum sized critical mass of polymer for the particular adhesive requirement. Methods of bringing the CTUcial number of particles together at the proper point of intersection for optimum bonding represents much of the ingenuity and skill involved in the utilization of emulsion polymers in adhesive applications. 

This material is approved by the FDA, as specified 21CFR in the following applications adhesives and polymers in food contact in the following polymers petroleum hydrocarbon resins, polyethylene, and polybutadiene. 

FDA approved for use in various polymers and adhesives intended for food contact applications as defined in 21CFR178.2010 and 175.105. 

Major polymer applications surface protective coatings (protective and decorative - automotive, metal cans, industrial flooring, anticorrosive paints), electrical/elec-tronics (printed circuit panels, conductive adhesives), composites (building/construction, marine, electrical/electronics, aircraft, communication satellites, automotive, pipes, consumer products), bonding and adhesives, flooring, tooling and casting, biosensors... 

Major polymer applications hot-melt coatings, hot-melt adhesives, wall covering adhesives, paints, tubing, sporting goods, footwear, baby products, controlled release devices, wire and cable (semiconductor shields, automotive wire, automotive ignition, low-smoke cable), asphalt modification, slow burning candles, cap liners... 

Major polymer applications membranes, adhesives, elastomeric applications... 

Major polymer applications aerospace, electronics (mostly films and coatings), photosensitive materials for positive imaging, solar cells, hollow fiber membranes, composites. unclear power plants, space shuttle, microprocessor chip carriers, structural adhesives... 

Major polymer applications TPU coatings, footwear, automotive, wire and cable, hose and tubes, film and sheet PU coatings, sealants, adhesives, foams, primers, mortars, and numerous other products... 

Major polymer applications production of poly(vinyl alcohol), adhesives, paints... 

Major polymer applications safety glass interlayer (automotive windshields), control of light, heat and sound in construction glass, bulletproof glass, adhesives and sealants, binders for rocket propellant, photoconductive papers, magnetic tapes, powder coating, wood sealers and primers, inks, ceramic binders, dry toners, wash primers, composite fiber binders... 

Major polymer applications pressure-sensitive adhesives, ablatives... 

Since the chemical reaction of the two components A and B begins in a pot immediately after mixing, this ready-made adhesive mixture requires speedy application. Otherwise the reaction for the formation of the AB polymer (the adhesive layer) will have developed to such an extent already prior to the application to the adherends that the expected strength of the bonded joint is impaired. Between the mixing of the adhesive mix and its application to the adherends and their fixing only a certain time span is allowed - which may vary for the individual reactive adhesives. This time is called the pot life. Depending on the reactivity of the A and B monomers, pot life can lie in the range of minutes or even hours. 

This chapter will deal with the chemistry and applications of epoxies, phenolics, urethanes, and a variety of current vogue high-temperature polymers. Applications in fiber-reinforced plastics will be discussed in the individual sections on resin chemistry where appropriate. Separate sections will deal with adhesives and sealants. Adhesives are most important because, as early history demonstrates, they led the way to the application of resins in aerospace. A section is also included on silicone and polysulfide sealants. Although these materials are elastomers rather than resins, no discussion of aerospace polymers would be complete without some mention. Some major thermosetting polymers have been omitted from this review. Among these are the unsaturated polyesters, melamines, ureas, and the vinyl esters. Although these products do find their way into aerospace applications, the uses are so small that a detailed discussion is not warranted. 

The immiscibility between both polymers is an important drawback that obliges us to look for a well-balanced set of properties, namely, mechanical, vapor, and gas permeability for barrier applications. Most applications are as multilayer, or sandwich sheet stmctures (polymer A/adhesive layer/polymer B), obtained by coextrusion, lamination or coating operations. The high operation costs associated with these processing techniques and the inability to obtain complex shapes that can expand... 

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