Release films are plastic films to which the resin material will not adhere.  They are usually placed next to the laminate and separate the laminate from breather and bleeder fabrics which would become boned to the laminate otherwise.

There are many release films available, we have only listed a couple.  Selection will depend on cure (including exotherm from the resin system), vacuum or pressure, resin system and complexity of the component.  The listed ones will suit all but the more exotic applications.

Release films can be perforated if resin bleed is necessary or it is needed to enable trapped air, excess resin or solvents to be removed. Prepregs normally do not have excess resin so it would not be usual to use a perforated film with a prepreg.

Better release films are very stretchy.  This permits the film to draw into complex shapes and is less likely to bridge over corners and gaps.  The elongation specification sets out stretchiness.