A Novel Methodology for Controlled Migration of Antifog From Thin Polyolefin Films

Transparent plastic films are widely used in agriculture as greenhouses covering and in the food industry as packaging films. The films are usually prepared by hydrophobic low polarity thermoplastics such as polyethylene (PE). In a greenhouse, the temperature and humidity are usually higher than the outside temperature and fog will appear on the inner surface of the PE film. Anti-fogging (AF) additives are tensoactive materials, mainly nonionic surfactants, equalizing the PE and water surface tensions, thus creating a thin, continuous film of water rather than discrete droplets. In the present work, a new method of controlled migration of AF is described, by grafting AF molecules to the surface of submicron inorganic particles. Glycerides and fatty acids are used as AF. During the grafting reaction two fractions are formed: attached AF fraction to the inorganic particles' surface, a fraction which cannot be detached by extraction, and an unreacted, thus unattached AF fraction. Solvent extraction, FTIR and TGA measurements have confirmed the existence of the grafted AF molecules to the inorganic particle's surfaces. Aging tests, developed in the present work, have shown a significant decrease of the AF migration rate, thus confirming an extended duration of the anti-fog's activity. (C) 2013 Society of Plastics Engineers