Polyurethane Science

Polyurethane Science

We have worked tirelessly within Rockdoor to improve how our doors are injected with PU foam. PU foam not only provides Rockdoor with the strength, weight it's thermal efficiency we are so proud of, but it's also what prevents the doors from bubbling.

Rockdoor skins are bonded to an inner frame with high impact adhesive and then a secret mix of Iso and Poly creates a high-density polyurethane foam that is injected into the void between the frame and skins.

Injecting PU Foam

Because every Rockdoor is made-to-measure, each needs a different amount of foam. Too much or too little - or the wrong mix, means the void doesn’t fill completely and if it gets too warm in the factory, the adhesive starts to set too quickly. When any of that happened during production, air bubbles the size of pinheads were created. These eventually expanded and turned into visible blisters in the centre and around the edge of the PVC-U skin.

Science Based Approach & Results

To ensure next generation Rockdoors don’t bubble, we’ve re-engineered our factory. Our foam partner’s scientists have changed their chemical formulae. Barcode scanners tell the injection heads precisely how much foam to pump into each door. And a new closed loop lagging system with inline temperature sensors automatically cools or heats the filling and glue lines to make sure all the chemicals flow as they should.

Like all doors, whether they are made of PVC-U, Timber or GRP, there is pressure on the door skins used. Through Rockdoors focus on research and development, we have vastly improved the overall performance of the door and the way we fill it towards banishing the bubble.