The invention is a patch
system for repairing collapsible fuel tanks,
water tanks,
inflatable boats, and other articles fabricated from a flexible structural fabric coated with a
polymer. The coated structural fabric is made of nylon or
polyester synthetic fibers or a blend thereof, which are coated with a
thermoplastic elastomer. The structural coated fabric is coated with a
thermoplastic elastomer that is a urethane (TPU), or a TPU
alloy polymer. Likewise, the patch is a urethane
adhesive having a latent cure coated on a TPU film. The patch can also have an integral reinforcing fabric for applications requiring a higher tensile patch. In the invention, the urethane
adhesive of the patch is
solvent activated by the application of a thin
coating of a volatile, substantially low
odor, fugitive
solvent like
acetone or MEK. While in the activated state, the
adhesive has much less cyrstallinity and a lot more tack. The
solvent activated adhesive has good
wetting, and aggressively wets out and adheres to the surface of the TPU
coating on the tank. The activated adhesive side of the patch is pressed against the surface of the tank. The solvent will also partially etch the
thermoplastic urethane
polymer coating on the tank fabric, and rapidly diffuses therein, ultimately evaporating to the surroundings. The cross-linkable urethane adhesive contains a blocked
isocyanate and, preferably, an uretdione. The reduced cyrstallinity in the adhesive imparts greater freedom to the blocked
isocyanate that can, depending on the equilibrium of the
system, begin to cross-link the adhesive. The curing process can be accelerated through the application of heat, albeit will slowly progress to a cured state at ambient conditions.