Will urethane rubber stick to PVA bags?
In lamination applications where urethane rubber is being used - yes the urethane rubber will permanently stick to PVA bags - IF ALLOWED.
To prevent urethane rubber from sticking to the PVA bag, it is necessary to strip the bag off the urethane rubber before the urethane rubber is fully cured.
In most cases, the time frame for stripping the bag is 3 to 4 hours after the "Work Time" has expired.
Once the bag is stripped, the urethane rubber remains on the cast until fully cured. The cast can be placed in an oven set at 150 F / 65 C, and allowed to cure under heat.
This process is highlighted in the Renew Materials Vol. 3 DVD "Fabrication of Custom Urethane Ankle-Foot & Wrist-Hand Orthoses."