Adhesives commercially available

Adhesion. Commercially available 1- or 2-coat adhesive systems produce mbber failure in bonds between ethylene—acryflc elastomer and metal (14). Adhesion to nylon, polyester, or aramid fiber cord or fabric is greatest when the cord or fabric have been treated with carboxylated nitrile mbber latex. 

Among the various structural adhesives commercially available today, epoxies are the most widely accepted and used. A recent market study showed that epoxy structural adhesives account for approximately 41% of all structural adhesives sold, and it is expected that they will maintain this market share over at least the next several years. Numerous references exist, both in the patent and journal literature, describing every facet of these adhesives. It is not the intention to review all of the available information. Rather, this chapter will concentrate on three main areas (1) A general description of epoxy adhesives (2) A discussion of commercially available raw materials, formulations, properties, and uses of epoxy adhesives (3) A review of developments in epoxy adhesives since 1979. Earlier work has been discussed in several reviews, and will not be covered in detail in this chapter. "... 

In a compilation of adhesives commercially available in the U.S., eight companies are listed as suppliers of anaerobic adhesives Devcon, Pel Pro, Loctite, Master Bond, Permabond, SPS Technologies, Sumitomo Chem Co., and Three Bond. This section contains a description of anaerobic products and their cured properties. 

In a comprehensive study Curry [730] examined small samples (< 10 p.g) of 94 household adhesives commercially available in the UK. Modern adhesives are quite intractable (insoluble, rubbery, etc.)... 

It is hoped that this brief overview will give the reader who is unfamiliar with the science and technology of the chemistry and formulation of common types of adhesives a general appreciation of the ways in which the adhesive may be transformed from the liquid to the solid state. Also, the aims of this chapter have been to give a broad appreciation of why there is such a myriad of adhesives commercially available and to have introduced the non-specialist to some of the major chemical types. 

Commercial products of adhesive are varied and the number of raw materials involved in them is almost infinite. The reason to employ so many raw materials is that adhesives need special compositions to meet the different demands or conditions such as adherends, applications, conditions of use, environments, and laws such as regulation concerning the registration, evaluation, authorization, and restriction of chemicals (REACH). O Figures 40.1 and O 40.2 show the main composition of adhesives commercially available. Since adhesives are varied, the raw materials also vary to a great extent. In this chapter, the description is concentrated in synthesized organic adhesives which are commercially available and widely used, because this reduces the number of combinations. 

An important newer use of fluorine is in the preparation of a polymer surface for adhesives (qv) or coatings (qv). In this apphcation the surfaces of a variety of polymers, eg, EPDM mbber, polyethylene—vinyl acetate foams, and mbber tine scrap, that are difficult or impossible to prepare by other methods are easily and quickly treated. Fluorine surface preparation, unlike wet-chemical surface treatment, does not generate large amounts of hazardous wastes and has been demonstrated to be much more effective than plasma or corona surface treatments. Figure 5 details the commercially available equipment for surface treating plastic components. Equipment to continuously treat fabrics, films, sheet foams, and other web materials is also available. 

Hydrocarbon resins are used extensively as modifiers in adhesives, sealants, printing inks, paints and varnishes, plastics, road marking, flooring, and oil field appHcations. In most cases, they ate compounded with elastomers, plastics, waxes, or oils. Selection of a resin for a particular appHcation is dependent on composition, molecular weight, color, and oxidative and thermal stabiHty, as weU as cost. A listing of all hydrocarbon resin suppHers and the types of resins that they produce is impractical. A representative listing of commercially available hydrocarbon resins and their suppHers is included in Table 6. 

Poly(vinyl alcohol) is used as an additive to dry-wall joint cements and stucco finish compounds. Rapid cold-water solubiUty, which can be achieved with finely ground PVA, is important in many dry mixed products. Partially hydrolyzed grades are commercially available in fine-particle size under the name S-grades. The main purpose of the poly(vinyl alcohol) is to improve adhesion and act as a water-retention aid. 

Vinyl neodecanoate [26544-09-2] is prepared by the reaction of neodecanoic acid and acetjiene in the presence of a catalyst such as zinc neodecanoate. Physical properties of the commercially available material, VeoVa 10 from Shell, are given in Table 4. The material is a mobile Hquid with a typical mild ester odor used in a number of areas, primarily in coatings, but also in constmction, adhesives, cosmetics, and a number of misceUaneous areas. Copolymerization of vinyl neodecanoate with vinyl acetate gives coating materials with exceUent performance on alkaline substrates and in exterior weathering conditions. 

Global consumption of thermoplastic mbbers of all types is estimated at about 600,000 t/yr (51). Of this, 42% was estimated to be consumed in the United States, 39% in Western Europe, and 19% in Japan. At present, the woddwide market is estimated to be divided as follows styrenic block copolymers, 48% hard polymer/elastomer combinations, 26% thermoplastic polyurethanes, 12% thermoplastic polyesters, 4% and others, 9%. The three largest end uses were transportation, 23% footwear, 18% and adhesives, coatings, etc, 16%. The ranges of the hardness values, prices, and specific gravities of commercially available materials are given in Table 4. 

Polynuclear Phenol—Glycidyl Ether-Derived Resins. This is one of the first commercially available polyfunctional products. Its polyfunctionahty permits upgrading of thermal stabiUty, chemical resistance, and electrical and mechanical properties of bisphenol A—epoxy systems. It is used in mol ding compounds and adhesives. 

Ethylene has also been copolymerised with a number of non-olefinic monomers and of the copolymers produced those with vinyl acetate have so far proved the most significant commercially . The presence of vinyl acetate residues in the chain reduces the polymer regularity and hence by the vinyl acetate content the amount of crystallinity may be controlled. Copolymers based on 45% vinyl acetate are rubbery and may be vulcanised with peroxides. They are commercially available (Levapren). Copolymers with about 30% vinyl acetate residues (Elvax-Du Pont) are flexible resins soluble in toluene and benezene at room temperature and with a tensile strength of about lOOOlbf/in (6.9 MPa) and a density of about 0.95 g/cm. Their main uses are as wax additives and as adhesive ingredients. 

Newer silicone adhesives having solids levels up to 97% are also commercially available [109]. Instead of using silanol condensation reactions, they rely on addition chemistry between vinyl functional silicone oligomers and silicon hydride terminated silicones. This addition reaction is typically facilitated with platinum derived catalysts. This hydrosilation process can be run at reduced oven temperatures, but the finished products typically do not yield the same balance of properties as seen for condensation cure materials. 

A word should be said about the weak boundary layer effect and silicone release [40,41]. Studies have shown that having loose silicone oil that can transfer to the PSA will lower release, however subsequent adhesion will likely suffer as well. In most commercial instances using silicone liners, a weak boundary layer is not intentionally employed. Additionally, many low transfer silicone liners are commercially available which provide premium release and show low to no PDMS transfer to PSAs, indicating that PDMS transfer is not a necessary condition for easy release. 

Acrylonitrile-butadiene rubber (also called nitrile or nitrile butadiene rubber) was commercially available in 1936 under the name Buna-N. It was obtained by emulsion polymerization of acrylonitrile and butadiene. During World War II, NBR was used to replace natural rubber. After World War II, NBR was still used due to its excellent properties, such as high oil and plasticizer resistance, excellent heat resistance, good adhesion to metallic substrates, and good compatibility with several compounding ingredients. 

The most commonly used isocyanate in urethane adhesives is MDI. The pure material methylene diphenyl-isocyanate is a solid that melts around 37°C. Many variations of MDI are commercially available, and these variations fall into three major classes monomeric MDI, modified MDI s, and polymeric MDI s. 

The morphology of a typical urethane adhesive was previously shown in Fig. 3. The continuous phase usually comprises the largest part of the adhesive, and the adhesion characteristics of the urethane are usually controlled by this phase. From a chemical standpoint, this continuous phase is usually comprised of the polyol and the small amount of isocyanate needed to react the polyol chain ends. A wide variety of polyols is commercially available. A few of the polyols most commonly used in urethane adhesives are shown in Table 2. As a first approximation, assuming a properly prepared bonding surface, it is wise to try to match the solubility parameters of the continuous phase with that of the substrate to be bonded. The adhesion properties of the urethane are controlled to a great extent by the continuous phase. Adhesion to medium polarity plastics, such as... 

Applications for blocked urethane adhesives are small. However, they may be used as flocking adhesives or as crosslinkers for solvent-borne adhesives. Blocked urethane adhesives are also used as splicing adhesives for belts. Blocked isocyanates based on TDI, IPDI, and derivatives of hexamethylene diisocyanate are most commonly commercially available. 

Table 3 lists the selected properties [16] that we have measured for several commercially available acrylate resins manufactured by the Sartomer Company and the Rohm and Haas Company. The resins were cured in an AECL Gammacell Model 240. The temperature rise was measured for an 8-g sample using Acsion s (formerly AECL Radiation Applications Branch) Gamma Calorimetry method [17]. All of this information is being used to evaluate the applicability of EB-cured acrylate adhesives for repairing composite structures. Combinations of these adhesives can be used to create electron-curable adhesives suitable for composite repair. 

Of the commercially available EB-curable adhesives [9-12], the resins fall within one of two categories based on their curing mechanisms. The majority of EB-curable resins are based on (meth)acrylate-functionalized oligomers involving a free-radical curing mechanism. The second category is the epoxy resins that cure by a cationic mechanism. 

At present there is only one commercially available tissue adhesive with approved on-label indications for skin closure. 2-Octyl-cyanoacrylate (Dermabond, Ethicon, Inc., Somerville, NJ) is presently indicated for skin closure in wounds which are not under extreme tension. This tissue adhesive is approved for topical skin application only. It is not indicated for internal use. The material is useful in closing traumatic skin lacerations [4,5] after wounds have been thoroughly cleaned as well as for minimally invasive surgical incisions and even larger surgical incisions in elective cases. The cyanoacrylate is applied while the skin... 

Polyethylene coating on ferrous pipes may be applied by means of one of the following processes circular or ring-type head extrusion, side extrusion and wrapping or powder sintering. The commercially available coating systems also differ further in that the extruded polyethylene may be applied in conjunction with various primer/adhesive systems. 

Another approach is that of bioadhesive materials. The principle is to administer a device with adhesive polymers having an affinity for the gastric surface, most probably the mucin coat [12]. Bioadhesives have demonstrated utility in the mouth, eye, and vagina, with a number of commercially available products. To date, use of bioadhesives in oral drug delivery is a theoretical possibility, but no promising leads have been published. 

---