Senior Flexonics Pathway's New FKM Adhesion System

One of the most common problems in the manufacture of FKM products is getting the FKM to bond to the reinforcing fabric. FKM’s major virtue, chemical resistance, is a serious detriment when trying to get it to combine chemically with anything else. It is important to remember that the bond between the rubber and its reinforcing fabric is a chemical bond, much more than a mechanical bond.

There have been three basic approaches to this problem by expansion joint manufacturers:

1. The use of a fluoroelastomer cement to coat the fabric. This works well, but involves the use of large amounts of solvents, which must be recovered in an environmentally responsible way. There are two major drawbacks: incomplete solvent recovery will produce voids and soft spots in the belt when heated, and the fi nal product will tend to be relatively stiff, making it diffi cult to install. This type belt also puts the base polymer under large amounts of stress when the belt is deformed under normal use.

2. The use of other chemicals to treat the cloth. The stiffness problem is abated; however, the solvent problem still exists.

3. Ignoring the whole issue. This practically guarantees the belt will delaminate in service, given the lack of a chemical bond.

Senior Flexonics Pathway's Approach

Senior Flexonics Pathway has invented an entirely new approach to the problem. Our new patent pending method involves no chemicals at all. We treat the cloth using a non-chemical technique which preserves the fl exibility of the cloth, but will withstand huge amounts of movement without delamination.

In our testing program, we compared the endurance of our new product with conventional, fl uoroelastomer coated cloth. Running side by side in a Demattia-type Flex Tester, inside an oven at 350 F, we observed 3 conventional samples fail due to delamination while the new material ran unaffected. We discontinued the tests at over 108,000 cycles without failure.

Perhaps more signifi cantly, the new material will withstand truly amazing amounts of lateral offset with little stress on the belt itself. Senior Flexonics Pathway has completed a series of studies which will shed new light on the amounts of offset possible with a nonmetallic expansion joint belt.

One of the major surprises was a comparison of the force needed to stretch a conventional belt as opposed to the Senior Flexonics Pathway belt. Our lateral resultant test program showed the force necessary to move a conventional belt as little as 1” laterally was several times greater than that for the Senior Flexonics Pathway belt.

Conclusion

The major implications of the new Senior Flexonics Pathway adhesion system are these:

1 . We do not use any chemicals whatsoever in our treatment. Therefore, the problems associated with them in production and in use are eliminated.

2. Mechanical stress on the rubber in service, a major cause of premature failure, is largely eliminated the problem. Our new patent pending method

3. Installation problems due to the inherent involves no chemicals at all. We treat the cloth using a non-chemical technique which preserves, the fl exibility of the cloth, but will withstand huge amounts of movement without delamination. stiffness of a conventional belt become much simpler.