Adhesive strength determination

The coating tensile adhesion strength determined by ASTM C633-13 designation (see Chapter 7.5.1.1) can be expressed by the polynomial equation... 

Fig. 19. Inlerfacial shear strengths of various fiber/matrix composites as a function of the work of adhesion as determined by IGC. 1, glass fiber-poly (ethylene) 2, carbon fiber-epoxy B 3, carbon fiber-epoxy A and 4, carbon fiber-PEEK. Redrawn from ref. [102].

An example of this improvement in toughness can be demonstrated by the addition of Vamac B-124, an ethylene/methyl acrylate copolymer from DuPont, to ethyl cyanoacrylate [24-26]. Three model instant adhesive formulations, a control without any polymeric additive (A), a formulation with poly(methyl methacrylate) (PMMA) (B), and a formulation with Vamac B-124 (C), are shown in Table 4. The formulation with PMMA, a thermoplastic which is added to modify viscosity, was included to determine if the addition of any polymer, not only rubbers, could improve the toughness properties of an alkyl cyanoacrylate instant adhesive. To demonstrate an improvement in toughness, the three formulations were tested for impact strength, 180° peel strength, and lapshear adhesive strength on steel specimens, before and after thermal exposure at 121°C. 

A surface is that part of an object which is in direct contact with its environment and hence, is most affected by it. The surface properties of solid organic polymers have a strong impact on many, if not most, of their apphcations. The properties and structure of these surfaces are, therefore, of utmost importance. The chemical stmcture and thermodynamic state of polymer surfaces are important factors that determine many of their practical characteristics. Examples of properties affected by polymer surface stmcture include adhesion, wettability, friction, coatability, permeability, dyeabil-ity, gloss, corrosion, surface electrostatic charging, cellular recognition, and biocompatibility. Interfacial characteristics of polymer systems control the domain size and the stability of polymer-polymer dispersions, adhesive strength of laminates and composites, cohesive strength of polymer blends, mechanical properties of adhesive joints, etc. 

ISO 5893 2002 Rubber and plastics test equipment - Tensile, flexural and compression types (constant rate of traverse) - Specification ISO 6237 2003 Adhesives - Wood-to-wood adhesive bonds - Determination of shear strength by tensile loading... 

ISO 6237 2003 Adhesives - Wood-to-wood adhesive bonds - Determination of shear strength by tensile loading... 

The quantity directly measured in a tear test is the force on the test piece during testing. Particularly with the trouser method, this force will fluctuate along the tear path. ISO 34 takes the maximum force reached in the case of crescent, angle and Delft methods but for the trouser method a median force is determined in accordance with procedures given in ISO 6133147, Analysis of multi-peak traces obtained in determinations of tear strength and adhesion strength. 

ISO 6133, 1998. Analysis of multi-peak traces obtained in determinations of tear strength and adhesion strength. 

Samples for adhesion measurements were prepared in a separate chamber with a base pressure of 1 x 10 ° Torr under identical conditions. Typically, -1000 A silver coverages were used for adhesion measurements. Adhesion strength of the deposited Ag films was determined using a polyester adhesive tape and standard peel test procedures on an Instron tester. 

It could be shown by the adhesion strength experiments that the best results are obtained if the ratio of free SiOH phCH = 0.18 and bridged SiOHrphCH is less than 0.05. Higher and lower values lead to a decrease of adhesion, however, the overall adhesion is only in the range of about 3-3.5 N cm , determined as peel strength. Investigations of the fracture mechanism show that the seal shows a brittle fracture behavior, as indicated in Fig. 9. 

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