This work was designed to study the effects of inorganic calcite powder on structurally different copolymer [poly(propylene-co-ethylene)] and terpolymer [poly (propylene-co-ethylene-co-1-butene)] matrices and the possibility of making a suitable porous composite film. The yield stress of the composites did not improve, but the modulus increased gradually with the filler loading. The theoretical and experimental modulus and yield stress of the composites provided evidence of filler and polymer adhesion behavior. The impact strength showed little enhancement up to a 20 wt % loading for the poly(propylene-co-ethylene-co-1-butene) system. The number-average, weight-average, and z-average air-hole diameters were compared with respect to the draw ratio as well as the calcite loading. The morphology of a micromechanically deformed composite, studied with an image analyzer, revealed that the aspect ratio and area of the air holes increased linearly as a function of the draw ratio, but the change in the aspect ratio upon filler loading was not remarkable. A suitable loading of a filler up to 30 wt % was good for controlling the porosity in the composite films. (C) 2008 Wiley Periodicals, Inc.