Urethane adhesives failure

It is difficult to generalize regarding adhesion properties and physical characteristics of urethanes, because both the adhesion properties and physical properties can vary widely. One two-part urethane adhesive may be an outstanding adhesive for bonding SMC/SMC. Another urethane adhesive may fail miserably using the same SMC, due to delamination at the interface or adhesive failure. 

The LRT data is summarized in Table II. The only change of note is with Urethane C and since that change indicates improved slope error, it cannot be related to adhesive failure. The other small changes are not considered significant enough to warrant any statement about a change in adhesive properties that might cause them. 

T Urethanes not shown because of great differences in physical properties, depending on formulations. Adhesion characteristics should he related by actual test data. Any system which shows concrete failure when tested for surfacing adhesion should he rated excellent with decreasing rating for systems showing failure in cohesion or adhesion below concrete failure. 

In a specific example of adhesive bonds between cold rolled steel and SMC adherends (Table II) an adhesive based on hydrolysis resistant epoxy chemistry (i.e., adhesive E) was compared with an adhesive based on hydrolysis prone urethane chemistry (i.e., adhesive C) in composite to cold rolled steel bonds. After corrosion testing, a significant difference in both retention of initial bond strength and locus of failure was observed. For bonds prepared with adhesive E, little if any reduction of the initial bond strength was observed after corrosion testing. The locus of failure for both the tested and untested bonds was largely in the... 

Adhesive properties are listed in Table IX. Shear strength, wood failure, and swelling data for two wood species, southern pine and hard maple, illustrate excellent performance properties of lignin-based urethane products. 

Failure loads for the three adhesives tested. Urethanes A, B, and C, are shown in Figure 7. Urethane A showed virtually no change in failure load. Urethanes B and C showed changes in... 

Adhesives (128) play an important role in the construction of a solar parabolic trough reflector. The adhesives should be compatible with silvered glass mirrors and should be able to carry structural loads. Moreover the adhesives should be durable for at least twenty years without losing their properties. Adhesives screened for solar collectors were epoxies, urethanes, and acrylics. Three types of stress conditions were identified as the most likely causes of failure in the trough modules ... 

The static moduli, failure stresses and dynamic moduli of an unfilled and filled polyether-urethane were measured over a range of equilibrium water contents and the results obtained compared with those for dry controls. Fillers employed were barytes (and small amounts of fumed silica and carbon black) or iron oxide. A quantitative relationship between water content and mechanical properties was established and the mechanics of the water/ polymer/filler interaction assessed. (Tenth Annual Meeting of the Adhesion Society Inc., Williamsburg, Virginia, USA, 22-27 Feb. 1987). 4 refs. 

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