Sunday, March 17, 2013

Rubber to metal bonding

Rubber to metal bonding is used in wide industrial such as shaft seals, gaskets, engine mount ,rubber rolling, bridge bearings etc. Elastermer selection is important in rubber product that present above. In this content we will present principal and performance of rubber to metal bonding detail as below. 
Principal of bonding agents
  • Applied like tackfree paints or varnishes to bond elastomers on rigid substrates under vulcanization conditions.
  • Advantage , Simultaneous molding and bond formation process between elastermer and substrate.
Requirement of bonding agents
  • Bond strength such as initial bonding . type of elastomer and vulcanization system.
  • Application such as application method, film formation and drying condition.
  • Storage such as shelf lift at variable temperature, freeze-thaw-stability and heat resistance.
  • Processing such as vulcanization method, prebreaking, method fouling and short curing cycles.
  • Resistance such as boiling water, salt spray climate, glycol and heat etc.
Product of rubber to metal bonding.
There are two type as standard product and special product. Standard products has three products as primer, covercement and one coat bonding agent. Special products has two product as waterbased bonding agents and electrostatic sprayable bonding agents.
Bonding performance.
Bonding performance influence  from rubber selection , hardness of cured rubber , carbon black concentration and type of carbon black, anioxidant or antiozonants type, curative, compound cure, plasticizer concentration and type.
Adhesive selection.
  • Which elastomer stock?
  • Durometer of the cured rubber compound.?
  • Cure speed?
  • Rigid substrate selection?
  • Special pre-bake and or sweep requirements.
  • How will adhesive be applied to the metal?

Instruction of rubber to metal bonding
Figure 1 Instruction of rubber to metal bonding

How to apply rubber to metal bonding.
  • Brush coating used in small scale ; usually applied undiluted.
  • Spray coating : used in large scale ; using jig for complex and specified area shape.
  • Dip coating : used in large scale ; avoiding tears and fatty edges from dip tank.
  • Roller coating : used in large flat sheets or roller components ; low product waste , uniformity film thickness.


Figure 2 example of rubber to metal bonding*

Hysteresis effect in race car tire and street car tire.


Tires are made from rubber, which is a viscoelastic material the loading and unloading stiffness curve are not exactly the same thus which make a loop with the unloading curve below the loading. The area within the loop is the amount of dissipated energy during loading and unloading. We are called hysteresis loop or damping properties .As a tire rotates under the weight and carry load of a vehicle, it experiences repeated cycles of deformation and recovery and it dissipates energy loss as heat. The amount of dissipated energy depends on the mechanical characteristics of the tire. Hysteresis energy loss in rubber decreases as temperature increases. The hysteresis effect causes a loaded rubber not to rebound fully after load removal.
Consider a high hysteresis race car tire rolling over road irregularities. The deformation tire recovers slowly and therefore, it cannot push the footprint tail on the road as hard as the footprint head. The difference in tail and head pressure causes a resistance force, which is called rolling resistance. Race car have high hysteresis tire to increases friction and limited traction that improve stability during running match. Street car such as passenger car  truck tire and solid tire have a low hysteresis tire to reduce the rolling resistance and low operating temperature that improve fuel consumption.  Hysteresis level of tire inversely effect the stopping distance such as a high hysteresis tire make the stopping shorter however it wear rapidly and has a shorter life time but do not affect with race car .