Additives to Compounds for Brass Adhesion

A low cobalt and boron-containing additive was also described by Bobrov [37], although their materials were not specified. It was shown that the effect of a resorcinol derivative (aminolysis of the brass coating), could be negated by the cobalt-boron additive, resulting in a high-modulus belt compound with a high corrosion resistance of the steel cord. 

Hoff reported on the use of certain melamine resins that were able to function as standalone or one-component systems when used in steel wire belt applications [39]. One-component melamine resins were described that were capable of forming a network in the rubber without the need for a co-reactant such as resorcinol. The performance of these new resins was compared to that of some classic two-component methylene donor-methylene acceptor systems. The new, one-component systems gave good initial and aged adhesion, equivalent tensile and dynamic mechanical properties and superior crack growth resistance than the currently used two component systems. 

Whereas the observations described in Section 6.2.6 can easily be accommodated by the adhesion model described earlier, this poses more problems with a series of papers published on the effect of precipitated silica [31, 40, 41]. Partial replacement of carbon black with precipitated fine particle size silica resulted in improved bond fatigue life of 

The positive effect of replacement of some carbon black by precipitated silica was further evaluated in a compound for wire adhesion that also contained an organocobalt adhesion promoter. Up to 20 phr of different types of silicas with widely varying surface areas was added. It was found that the energy of adhesion, which increased linearly with the phr of silica, did not correlate with any of the silica properties. Thus, the observed improvement of wire adhesion was not a physical effect due to increased compound tear strength, but was again related to changes in the interfacial layer formed on the wire [40]. 

Waddell did some work on the changes in the interfacial layers [41]. A wide range of surface-analytical tools were used Auger electron spectroscopy (AES), x-ray photoelectron spectroscopy (XPS), SEM, EDX, and particle indnced x-ray emission (PIXE), which indicated that silica use reduced the thickness of the interfacial film, and particularly promoted zinc oxide formation and lowered the amount of sulphide formed. 

---