Epoxy adhesives strength

To obtain a usable adhesive bond with polyolefins, the surface must be treated. A number of surface preparation methods, including flame, chemical, plasma, and primer treatments, are in use. Figure 16.4 illustrates the epoxy adhesive strength improvements that can be made by using various prebond surface treatments to change the critical surface tension of polyethylene. 

Bonin HW, Bui VT, Pak H, Poirer H, Harris H (1998) Radiation effects on aluminum-epoxy adhesive strength. J Appl Polym Sci 67 37 7 Borowitz S, Beiser A (1971) Essentials of physics a text for students of science and engineering, 2nd edn. Addison-Wesley series in physics. Addison-Wesley, Reading... 

A.dhesiveslCements Sealants j Coatings. Excellent adhesives of high strength and high oil resistance can be prepared using nitnle mbber (25). Many references have discussed the use of nitnle mbber—phenoHc and nitnle mbber—epoxy adhesives for printed circuit boards. 

Fig. 5. Examples of ihe correlation between measured adhesive strength and (l+cos6). (a) Plot of data from Raraty and Tabor [171J for adhesion of ice to various solids, (b) Plot of data of Barbaris [172] for adhesion of a mixture of epoxy and polyamide resin to low density poly(ethylene) treated in various ways. Both figures from ref. [31], by permission.

There has been very little work done on the development of EB-curable epoxy adhesives. When undertaking this development work the authors had two objectives. The first objective was to develop a series of adhesives for bonding aluminum-to-aluminum (Al-Al) and composite-to-composite (C-C) with lap shear strengths of 30 MPa or greater at room temperature. The second objective was that the... 

We have also looked at the lap shear strength of selected EB-ciirable epoxy adhesives. Because the adhesives being developed were being used for both aluminum-to-aluminum and composite-to-composite applications the lap shear strengths for both adherends was measured. Aluminum adherends were T2024 phosphoric acid anodized according to ASTM 3933. The composite adherends... 

Lap shear strengths (MPa) of selected EB-cured epoxy adhesives at various temperatures... 

Effects on lap shear strength of EB-cured epoxy adhesives from different surface preparations on aluminum and composite adherends... 

Adhesive strength is evaluated at room temperature as well as at the extreme temperatures of —65°F and 180°F. Aircraft structure can reach —65°F at cruise altitudes and 180°F on the ground in a hot, sunny location. The types of toughened epoxies commonly used for metal bond adhesives have glass transition temperatures not much greater than 200°F, so properties fall off drastically at higher temperatures. 

The thickness of the coating also affects permeability, and in general, there is a correlation between thickness and life. However, with relatively thick coatings as obtained with some modern materials such as epoxies the relationship is not so well established. There may be a limiting thickness above which either little additional protection is obtained or the increase in cohesive strength reduces its adhesive strength. Coatings should always be applied as closely as possible to the manufacturer s recommended thickness. 

Table 16.5. Peel Strengths Obtained for Surface Fluorinated PE with Epoxy Adhesives"...

Our experience indicates that fluorination generally results in decreased adhesion strength compared to oxyfluorination (see Tables 16.6 and 16.8). This is in contrast to reported findings in the literature where epoxy adhesives were used.7,29 This discrepancy can be attributed to the surface energy implications of the increased acyl fluoride to the C—H—F functionalkation ratio (compare Figures 16.3 and 16.4). However, as indicated by our data, certain resin formula-... 

Table IV. Effect of Primer Chemistry on Bond Strength of SMC/Primed Steel Epoxy Adhesive Bonds...

Other effects were more selective. While recycle usually lowered impact strength and heat deflection temperat ire, pre-soaking polyamine recycle surprisingly improved both of these properties. While recycle usually lowered volume resistivity, polyamide recycle improved it. Finally, adhesion of epoxy formulations to the aluminum mold, in spi/ e of wax and silicone mold release agents, was dramatically increased by the use of presoaked recycle, especially in the ai ydrlde system, suggesting unexpected usefulness in epoxy adhesive formulations. 

The DP is dependent on the ratio of reactants. Generally an excess of the epichlorohydrin is used to produce cyclic ether end groups. Epoxies are formed from the reaction of diamines with low molecular weight epoxy resins that retain their cyclic ether end groups. Figure 4.9 shows the formation of this process. These materials are often sold as two-part, or two-pot, epoxy adhesives. Most use-at-home epoxy packages contain a part A of epoxy resin and a part B of hardener (typically a diamine). These two are mixed as directed and applied. They dry fast, so they can be handled in 5 10 min. Full strength occurs after 5 7 days. 

Minit Grip Epoxy adhesives High Strength Plastics Corp. 

Stafford CM, Kim JH, Kawaguchi D, Royston G, Chiang MYM (2006) Probing the interfacial adhesion strength in compositional libraries of epoxy films. Mater Res Soc Symp Proc 894 129-137... 

Table III. Tensile Shear Adhesive Strength of Ozonized Lignin/Epoxy Resins. (Normal Test)...

This review will first present the metal/epoxy resin adhesive system and discuss how the presence of metal oxides influences adhesion secondly, present the reasons why these systems exhibit very good adhesion strength under dry conditions and why this adhesion strength is greatly reduced in the presence of water thirdly, examine possible methods of increasing their durability in wet environments and finally, discuss some of the spectroscopic techniques that are currently being used to aid in the advancement of metal/polymer adhesion technology. 

Allen and Alsalim 22 compared the effect of various pretreatments of stainless steel (martensitic structure) on the torsional shear strength of napkin ring joints formed with an epoxy adhesive (Redux 319 (Bonded Structures Ltd.)). They concluded that... 

High initial adhesion strength between epoxy resins and metals is readily obtainable as long as surface contamination and weak oxide layers have been removed from the... 

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