Adhesion, improvement

Solvent mixture also affects the application properties of the CR adhesives. Improved application properties are obtained by using a solvent blend which falls closer to the shady area of the kidney-shaped diagram of Fig. 37. 

As demonstrated earlier, the addition of other eleetron defieient monomers to eopolymerize with the eyanoaerylate monomer has not proven to be an effeetive means of modifying the physieal properties of eyanoaerylate-based adhesives. The most effeetive adhesive improvements have eome through the ineorporation of various additives, whieh modify the adhesive physieal properties but do not eopolymerize with the monomers. These produet development efforts have been quite sueeessful in improving the properties of alkyl eyanoaerylate-based adhesives to the point where they ean now be used in a huge variety of applieations. 

Because of the need for basic initiators, cyanoacrylate adhesives do not perform well on acidic surfaces, such as wood. However, the addition of sequestering agents, such as crown ethers [30], 10, or calixarenes [31], 11, and others [32] to the adhesive improves the reactivity of the adhesive on less active surfaces. 

Many types of chemical treatment are used in industry. Chromic, permanganic, sulphuric, and chlorosul-phonic acids are often used as the oxidants. It has been shown that the adhesion of polyethylene to substrates, such as cellophane, steel, aluminium, and epoxy adhesives, improves upon pretreatment with any of the etchants mentioned previously. 

Titanium is a very difficult metal to electroplate because of the presence of an oxide film. Sophisticated pretreatments with acids to remove the oxide film are necessary to achieve good adhesion. Improvements in the level of adhesion can, however, be obtained by heat treatment of the resultant Pt/Ti composites... 

For formation of anticorrosive and adhesion-improving protective layers on metals the cleaned surface is treated with aqueous acidic solution containing molybdate, chromium fluoride, phosphate, acetate, and Zn ions. As dispersant a mixture of 60% alkali salt of a phosphate ester, 20% alkylpolyglucoside, and 20% fatty alcohol ethoxylate was applied. This method passivates the metal surface by formation of an anticorrosive and protective layer that improves adhesion of subsequent coatings. 

Recently siloxane-imide copolymers have received specific attention due to various unique properties displayed by these materials which include fracture toughness, enhanced adhesion, improved dielectric properties, increased solubility, and excellent atomic oxygen resistance 1S3). The first report on the synthesis of poly(siloxane-imides) appeared in 1966, where PMDA (pyromellitic dianhydride) was reacted with an amine-terminated siloxane dimer and subsequently imidized 166>. Two years later, Greber 167) reported the synthesis of a series of poly(siloxane-imide) and poly(siloxane-ester-imide) copolymers using different siloxane backbones. However no physical characterization data were reported. 

Bemabeu-Gonzalvez A., Pastor-Bias M.M., and Martm-Martmez J.M., 1998, Modified adhesion of rubber materials by surface migration of wax and zinc stearate, in Proceedings of the World Polymer Congress, 37th International Symposium on Macromolecules MACRO 98, Gold Coast, Australia, 705. Romero-Sanchez M.D., Pastor-Bias M.M., and Martm-Martmez J.M., 2001, Adhesion improvement of SBR rubber by treatment with trichloroisocyanuric acid solutions in different esters, Int. J. Adhes. Adhes., 21, 325-337. 

Despite such limitations, plasma-deposited a-C(N) H films were found to be used in a number of applications. The stress reduction induced by nitrogen incorporation [12] and consequent adhesion improvement, allowed the development of a-C(N) H antireflective coatings for Ge-based infrared detectors [13]. It was also found that N can electronically dope a-C H films, and can strongly decrease the defect density, which gives prospects on its use as a semiconductor material [14]. Nitrogen incorporation was also found to decrease the threshold electric field in electron-field emission process [15], making possible the use of a-C(N) H films as an overcoat on emission tips in flat-panel display devices [16]. 

Adhesive Improving cohesion Colophony, gelatine, animal glue, casein... 

F-BDAF Tg for various blend compositions, see Fig. 14. The microphase-separated morphology further manifests itself in the self-adhesion behavior of polyimide films derived from such mixtures. For mixture containing at least 25 wt% of the flexible component, peel tests of polyimide bilayer samples prepared by solution casting, bulk failure of the test specimens was observed. Since the flexible component contained fluorine, the samples could be examined by X-ray photoelectron spectroscopy to determine the surface composition. At only 10% loading, the flexible component comprised 100% of the top 75 A of the sample. The surface segregation of the flexible component is believed to be responsible for the adhesion improvements. 

Initial adhesion improvement and increased reliability is seen when APS is used in connection with Si02, but no significant change is observed with... 

Silanes have also been employed to improve adhesion to metal substrates. For example, Toray Chemicals of Japan has observed adhesion improvement for Mo by employing an organosilane (isopropanol solution) and for Al, Ti, Ni, and Pd by employing an organotitanate spun from toluene. Results for other silanes to Au and Al are reviewed later. Similarly, Dynamit Nobel recommended employing glycidoxypropyltrimethoxysilane to improve positive photoresist image adhesion to Ta, W, Al, and Nb. 

Further work by Comyn (private communication) has attempted to use a peel test to measure the actual adhesion improvements. Zirconium propionate was... 

Polychloroprene (neoprene) Toluene, methanol, isopropanol 1. Abrasion followed by brushing. Grit or vapor blast or 100-grit emery cloth followed by solvent wipe. 2. Etch surface for 5-10 min at RT following procedure 2 for natural rubber. Adhesion improved by abrasion with 280-grit emery cloth followed by solvent wipe... 

Finally, comparing the results for CF4 plasma-treated PC and PVC, we note that substantial adhesion improvement occurs for the former but not for the latter. The fact that both treated surfaces become highly fluorinated and hydrophobic once again underscores the state-... 

Even if the Al Oj interlayer accelerates the activation of the transverse cracking, it seems to have the opposite effect on adhesion failure. Indeed, we observe for both systems with an Al Oj interlayer (B and E) that the debonding and buckling are delayed. Therefore, the adhesion of the films is improved. The presence of this thermally grown Al Oj interlayer increases the interfacial fracture energy values to about 15 J.m in both systems. Two qualitative explanations can be proposed for the adhesion improvement. First, the Al Oj certainly permits an increase in the number of 0-Si bonds between the interlayer and the film. Second, prior to the... 

Figure 30.8 Adhesion improvement of Parylene C to TMS or TMS/CH4 plasma pol5rmer coated 7075-T6 panels with subsequent Ar RF plasma treatment at 100W and SOmtorr (a) and (b) on TMS plasma polymer, treatment time 1.0 min, (c) on TMS/CH4 plasma polymer, treatment time 2.0 min, (d) on TMS/CH4 plasma polymer, treatment time 10.0 min the blue color (dark) in (b) is the color of TMS film, indicating that Parylene C film was peeled off.

Figure 30.10 Adhesion Improvement of solvent-borne primer (519X303, Courtaulds Aerospace) to the Parylene C surface after LTCAT plasma treatment at various plasma resident times Ar flow rate 1000 seem, arc current 6.0 A.

Use Imparts water tolerance and vapor permeability to copolymer films latex and water-based coating compositions adhesion improver for cellulosics, concrete, glass cross-linking agent in polyester resins color photography. 

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