Adhesion elastomer inclusion

The location of the maximum stress concentration moves away from the particle surface with increasing inclusion volume fraction and its actual position depends on the spatial packing of the inclusions. In Chapter 6, it was shown that not much of a difference is seen in the shape of the stress field around an elastomer inclusion, a void, and a rigid inclusion with no adhesion to the matrix. 

Requirements for rubber toughening of glassy polymers include (I) good adhesion between the elastomer and matrix, (2) cross-linking of the elastomer, and (3) proper size of the rubber inclusions. These topics are reviewed briefly in the order listed ... 

Quantitative surface and interfacial tension data for polymers are crucial to many aspects of the production and application of elastomers, plastics, textiles, films and coatings, foams, polymer blends, adhesives, and sealants. Although interface is the inclusive term for the region in space where two phases meet, if one of the phases is gaseous it is usually called a surface [1]. Thus we refer here to the surface tension of a polymer in air but to the interfacial tension between a polymer and a condensed phase such as water or another polymer. 

The CNIS and of a group of ternary composites of polypropylene filled with 30 vol% of rigid Mg(OH)2 and 10 vol% of elastomeric EPR inclusions were studied as a function of a concentration of maleic anhydride (MAH). In all systems studied, the variation in adhesion was achieved by increasing the concentration of MAH in either the matrix (complete separation of the elastomer and filler) or in the elastomer (complete encapsulation of the filler by the elastomer). The CNIS/Gc ratio and scale factor are plotted versus MAH concentration in Fig. 6.13,a and b, respectively. 

It is clear that ab will be extremely large for inclusions of small radius r, even if the level of adhesion, represented by Ga, is relatively small, only of the order of magnitude of van der Waals attractions. For example, when E is assumed to be 2 MPa, representative of soft elastomers, and Ga is given the relatively low value of 10 J/m, then the critical applied stress for detachment is predicted to reach a magnitude similar to E when the radius of the inclusion is reduced to about 20 ixm, even if the initially debonded zone is as large as feasible, 6 — 45°. These considerations appear to account for some features of reinforcement of elastomers by particulate fillers Fillers (140). 

The adhesive characteristics of an elastomer are recognizably altered by the inclusion of as little as 0.01 equivalent of carboxyl per hundred grams of rubber (ephr) although larger amounts, even in excess of 0.1 ephr, are often preferable. The optimum carboxyl content, molecular weight, and the particular elastomeric polymer selected for use as an adhesive depend on the nature of the surfaces to be adhered and the requirements of the adhesive bond. 

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