Substrate failure

Adhesives need to produce high peel forces when the adherends are pulled apart — preferably high enough to induce substrate failure. To accomplish high peel, the... 

Adhesion depends on a number of factors. Good adhesion is defined by most customers as substrate failure. The major adhesive manufacturers possess equipment that allows them to make bonds with customer substrates under conditions that closely simulate actual packaging lines. These bonds are peeled either automatically or by hand to gauge adhesion. The most important factors influencing adhesion are the wet-out of the substrate, partieularly by the polymer component of the adhesive system, and the specific adhesion with the substrate. Choice of resin is critical for both. Rosin, rosin esters and terpene phenolics are eommonly added for these purposes in EVA and EnBA-based systems. Adhesion at low temperatures is also influenced by the overall toughness of the system at the test temperature. 

Low surface energy substrates, such as polyethylene or polypropylene, are generally difficult to bond with adhesives. However, cyanoacrylate-based adhesives can be effectively utilized to bond polyolefins with the use of the proper primer/activa-tor on the surface. Primer materials include tertiary aliphatic and aromatic amines, trialkyl ammonium carboxylate salts, tetraalkyl ammonium salts, phosphines, and organometallic compounds, which are initiators for alkyl cyanoacrylate polymerization [33-36]. The primer is applied as a dilute solution to the polyolefin surface, solvent is allowed to evaporate, and the specimens are assembled with a small amount of the adhesive. With the use of primers, adhesive strength can be so strong that substrate failure occurs during the course of the shear tests, as shown in Fig. 11. 

Both the above simulations considered identical tips and substrates. Failure moved away from the interface for geometric reasons, and the orientation of the interface relative to easy slip planes was important. In the more general case of two different materials, the interfacial interactions may be stronger than those within one of the materials. If the tip is the weaker material, it will be likely to yield internally regardless of the crystallographic orientation. This behavior has been observed in experiments between clean metal surfaces where a thin tip is scraped across a flat substrate [31]. When the thin tip is softer than the substrate, failure is localized in the tip, and it leaves material behind as it advances. However, the simulations considered in this section treated the artificial case of a commensurate interface. It is not obvious that the shear strength of an interface between two incommensurate surfaces should be sufficient to cause such yield, nor is it obvious how the dislocation model of Hurtado and Kim applies to such surfaces. 

These adhesives have been found to adhere strongly to metals, glass, wood, ceramics, masonry, asphalt, leather, and plastics like polystyrene, phenolics, polycarbonates, ABS, cellulose acetate, polyesters, rubbers, and some polyolefins. In general, the most favorable results are noted in the bonding of steel and aluminum, perhaps because the bond strengths are more easily observed before substrate failure. 

Cure on pine wood 40 mil gap 500 psi Partial substrate faUure Substrate failure... 

Figure 7 Durability of cyanoacrylate adhesives. Asterisk denotes substrate failure.

FAILURE THROUGH ORDINARY CEMENT MORTAR (SUBSTRATE) FAILURE through LATEX-MODIFIED MORTAR FAILURE THROUGH THE INTERFACE (ADHESIVE FAILURE)... 

Substrate failure, break in the substrate, the bond line is stronger than the substrate (structural bonding)... 

Notes Peel - NF T 76.126. Flash point 66 C pH 6. Similar products Notes x DIN 53283 aluminium Rigid-PVC 10 MPa (substrate failure). Peel ... 

Notes x DIN 53283 (substrate failure). Notes Resistivity DIN 53482 10. Dielectric Index DIN 53482 (lOHz/RT)... 

Notes x nitrile rubber) 0.2MPa - substrate failure. T-peel, RT. Notes x(nitrile rubber) 0.2MPa - substrate failure. ... 

Notes x(nitrile rubber) 0.7MPa substrate failure. Notes > ... 

Notes substrate failure, x PTFE, polyethylene, polyamide 1.5-3.3 N/mm. Notes <40%RH increases cure time, x DIN 53283. Flash point DIN 53213. ... 

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