WATER-VAPOR AND OXYGEN PERMEABILITY OF WAX FILMS

The water vapor (WVP) and oxygen (O2P) permeabilities of beeswax (BW), candelilla wax (CnW), carnauba wax (CrW) and microcrystalline wax (MW), formed as free-standing films, were determined. CnW and CrW both had small values for O2P (0.29 and 0.26 g.m-1.sec-1.Pa-1 X 10(-14), respectively), which are less than half the value for high-density polyethylene and about a decade greater than the value for polyethylene terephthalate. O2P values for BW and MW were about 6-9 X greater than those of CnW and CrW. WVP of CnW was 0.18 g.m-1.sec-1.Pa-1 X 10(-12), which is about one-half the value for CrW and MW and about one-third the value for BW The WVP of CnW was somewhat less than that of polypropylene and somewhat greater than that of high-density polyethylene. Differences in permeabilities among the wax films are attributed mainly to differences in chemical composition and crystal type as determined by X-ray diffraction.