Micro-porous films are defined as having a narrow pore-size distribution, usually in the sub-micrometer range although they can range from 0.1 to 10 um. It is common for micr0-porous films to have 1-2 billion pores per square centimeter in a film 10-50 um thick.
Modified atmosphere packaging (MAP) of fresh produce has been an active research area for many years. The problem is that most polymeric films are too impermeable for packaging high-respiring products like broccoli, cauliflower, carrots and cut fruit.
In order of achieving high rates of gas exchange is through the use of micro-porous and perforated films.
The gas diffusion constant for a perforation is approximately 4 to 8 million times greater than that of a low-density polyethylene film.
Micro-porous films are prepared by extrusion of filler-containing polymers. The common fillers are CaCO2 or SiO2, although other porous powders may be included.
Gas permeability is controlled by adjusting the filler content, the particle size of the filler and the degree of stretching the film.
Micro-porous film
