- 13 March 2007 -
Danisco develops antifog for polypropylene film

Danisco Emulsifiers of Denmark has developed new antifogging additives for polypropylene (PP) film based on glycerol esters. Reported at the recent Addcon conference in Cologne, Germany, the new antifog solution is aimed at applications in the rapidly growing film packaging market for PP.

According to Danisco, glycerol esters offer several important advantages in the increased focus on safe and sustainable packaging solutions. They offer a high degree of safety and the company says that the latest developments demonstate greater efficiency.

Glycerol esters are most often referred to as GMS, glycerol monostearate and GMO, glycerol monooleate. GMS and GMO have been used as antistats and antifogs in various polyolefin applications for some time. However, the chemistry of glycerol esters can be more complex than represented by these two products; the new additives developed by Danisco are polyglycerol esters. These products are made by the polymerization of glycerin, which is then esterified with fatty acids. The degree of polymerization can vary and different fractions can be separated out to yield a well defined and narrow distribution of polymerized glycerin, which offers significant opportunities for antifog and antistatic performance in PE and PP.

The company explains that while there have been antifogging agents that have worked well in polyethylene (PE) for many years, finding an antifogging agent for polypropylene that is also unconditionally approved for food contact use has been more challenging. The main difference in performance between the two polymers is due largely to the difference in crystallinity. PE has low crystallinity and allows faster migration of additives to the polymer surface. In PP, migration is slow because of the much higher crystallinity. PE antifogs cannot be used in PP because they will not migrate fast enough, says Danisco.

Danisco adds that in order for antifogs to work in PP, the molecules need to be redesigned to migrate faster in a crystalline polymer, which means smaller and ‘slimmer’ molecules. In addition, the polarity of molecules must not suffer as the ability to reduce surface tension and establish the antifog property must be intact. Danisco presented research on a polyglycerol ester, PGE 907, at a 1% loading in a 50 micron blown PP film and the efficiency was shown to be very good.

The company has also developed products that are offering new antistatic solutions in LDPE and LLDPE, which work well at low loading levels and conditions of low humidity. This is particularly attractive in electronic packaging applications because this new product is completely free of any components that can result in stress cracking of polycarbonate.

Danisco Emulsifiers; www.danisco.com