Adhesion of FKM/VMQ and FVMQ/VMQ in turbocharger hoses for combustion engines.
For a long time the fluoroelastomer FKM, fluorosilicone FVMQ and silicone VMQ are used in internal combustion engines. There has been new application, which is elastic silicone hoses, feasible to work in dynamic conditions at high temperature, being at the same time exposed to contact with organic fluids and exhaust gases.
VMQ polymer shows low resistance to carbohydrates, whereas FKM and FVMQ fluorinated rubber in fact have such resistance. Thanks to these properties they find useful application in construction of high-temperature silicone hoses, such as turbocharging elements for combustion engines.
Currently producers of compounds and silicone hoses face a problem that constrain them, which is a lack of possibility to obtain sufficient and permanent adhesion of FKM or FVMQ layer to VMQ. Solutions available on the market enable to obtain only initial acceptable adhesion of fluorine compounds to the silicone one. Moreover, the adhesion decreases drastically at the time when the system is aging at elevated temperature (200 ° C).
Therefore, there are three critical parameters to be considered: thermal resistance, oil resistance and adhesion of the FKM or FVMQ internal layer to the VMQ external layer. The integrity of the readymade hose depends not only on acceptable initial bond strength but also on feasibility to maintain it while it is exposed to high temperature, oil and vibrations occurring during normal usage.
To meet the expectations of the market, we designed:
high-temperature, silicone adhesive with strong adhesion to FVMQ
fluorine compound to be applied as internal layer of a silicone hose and adhesive silicone SEMISIL-BS
The developed compounds, thanks to appropriate selection of polymer basis, fillers and cross-linking agents, enable obtaining bounds characterized by very good adhesion in natural state as well as an ability to maintain it after aging in the temperature of 200 o C. The high adhesive SEMISIL-BS silicone compound – applied as an adhesive layer allows to acquire permanent bounding of either BS-70 or FVMQ compounds to VMQ silicone compounds in the process of hot vulcanization.