1. Introduction
Despite rubber-to-metal bonded assemblies being used
in a wide and growing range of industrial applications,
particularly for the reduction of noise and vibration, the socalled
“vulcanization bonding process” remains poorly
understood [1]: It consists of molding and vulcanizing raw
rubber onto a metallic surface coated with an adhesive
reactive bonding layer. The rubber-to-metal assembly is
thus obtained in a unique step. Contrary to “post-vulcanization
bonding” techniques, it also allows the molding of
complex shapes with bonded metallic inserts. Nevertheless,
the process is quite complex since it involves various
diffusion phenomena, along with chemisorption, bulk and
interfacial crosslinking reactions [2]. Fig. 1 shows the
generally accepted schematic view of the interface in the
case of a bonding layer consisting of two layers [1]: A
primer, coated on the metallic substrate, and an adhesive
layer in contact with the raw rubber. The total thickness of
these layers is typically lower than 30 mm.
In such a complex system, various conditions have to be
fulfilled in order to obtain high performance rubber-tometal
adhesion:
The first condition concerns the internal crosslinking
reactions of the rubber, the primer and the adhesive, the
respective kinetics of which have to be compatible within
the imposed molding cure temperature cycle: Persson et al.
[3] have used Dynamic Mechanical Thermal Analysis
(DMTA) to study and compare the individual reaction kinetics
of commercial adhesives and primers with that of a
model rubber compound. They conclude that the reaction
sequences of the three components need to be matched in
the best possible manner for optimal bonding.
The second condition is the presence of efficient
chemisorption and cross-bridging reactions that allow the
generation of chemical adhesion at the different interfaces.copolymer, such a multilayer setup allows sensing and
modelling this key phenomenon. In addition, the same
rotational rheometer can be used to separately characterize
the individual rheokinetic behavior of the different reactive
layers: primer, adhesive and rubber.
1. IntroductionDespite rubber-to-metal bonded assemblies being usedin a wide and growing range of industrial applications,particularly for the reduction of noise and vibration, the socalled“vulcanization bonding process” remains poorlyunderstood [1]: It consists of molding and vulcanizing rawrubber onto a metallic surface coated with an adhesivereactive bonding layer. The rubber-to-metal assembly isthus obtained in a unique step. Contrary to “post-vulcanizationbonding” techniques, it also allows the molding ofcomplex shapes with bonded metallic inserts. Nevertheless,the process is quite complex since it involves variousdiffusion phenomena, along with chemisorption, bulk andinterfacial crosslinking reactions [2]. Fig. 1 shows thegenerally accepted schematic view of the interface in thecase of a bonding layer consisting of two layers [1]: Aprimer, coated on the metallic substrate, and an adhesivelayer in contact with the raw rubber. The total thickness ofthese layers is typically lower than 30 mm.In such a complex system, various conditions have to befulfilled in order to obtain high performance rubber-tometaladhesion:The first condition concerns the internal crosslinkingreactions of the rubber, the primer and the adhesive, therespective kinetics of which have to be compatible withinthe imposed molding cure temperature cycle: Persson et al.[3] have used Dynamic Mechanical Thermal Analysis(DMTA) to study and compare the individual reaction kineticsof commercial adhesives and primers with that of amodel rubber compound. They conclude that the reactionsequences of the three components need to be matched inthe best possible manner for optimal bonding.The second condition is the presence of efficientchemisorption and cross-bridging reactions that allow thegeneration of chemical adhesion at the different interfaces.copolymer, such a multilayer setup allows sensing andmodelling this key phenomenon. In addition, the samerotational rheometer can be used to separately characterizethe individual rheokinetic behavior of the different reactivelayers: primer, adhesive and rubber.
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