A common industry practice is to pre-cut or sheet the encapsulant material prior to assembling the entire module construction for lamination. If this is done, the sheeted encapsulant is usually left unprotected in the factory environment, and a typical question is: how long can the encapsulant be exposed to factory ambient conditions without protection?

The exposure time certainly depends on the factory environment. The lower the humidity, the longer the sheeted material can survive without impacting its critical properties (i.e., adhesion strength).

Figure 1 shows how a sheeted encapsulant's glass adhesion strength depends on the time it is exposed to controlled environmental conditions of 65% relative humidity and 21°C. Even after 11 days, the exposed sheet had a glass adhesion above 45 lb/in.

For situations where it is uncertain how long sheeted encapsulant will be left unprotected, STR recommends to store precut materials in a cabinet “desiccator.” Similarly, unused encapsulant rolls should be repackaged.