ASSESSMENT OF FREON RELEASE FROM POLYURETHANE FOAMS

S. Kesari, S. Kapila and G. Bertrand

Center for Environmental Science and Technology and Department of Chemistry, University of Missouri-Rolla, Rolla, MO, 65401


ABSTRACT

Significant amounts of freons, predominantly CFC-11 (trichlorofluoromethane), are trapped over long periods in polyurethane foams. These foams are one of the most widely used forms of plastic with varied applications. Polyurethane and polystyrene form the bulk of polymeric foams for which freons have been used as the foaming agents. Initial concentrations of freons in such foams are in the 20-30% range. Results of a survey of freon residues in polyurethane foam revealed that, in the absence of free exchange with air, these foams effectively retain freon for long periods of time. Polyurethane foam samples from 15 year old refrigerators were found to contain freon at concentrations ranging from 15-20% w/w. These concentrations clearly indicate that polyurethane represents a large, long-term source of freon in the environment.

To estimate the long-term release of freon, an experimental release model has been developed. The model takes into account such parameters as polymer film thickness, temperature and photoinduced degradation of polyurethane foam. The model has been validated with experimental results. The results show that the release of freon from a polymeric foam is dependent on permeability across the polymer film. The permeability is dependent on environmental parameters to which the foams are exposed. The most pertinent of these are temperature and exposure to sunlight. To monitor the effects of these parameters, a series of weathering experiments were undertaken. A QUV accelerated weathering tester was used for simulation of the damage to the polymer structure from exposure to the elements. Some of the foam samples were also aged under natural sun light. Freon content of foam was determined periodically. The determinations were carried out by extracting freon with methanol and injecting methanol solution into a calibrated gas chromatograph-mass spectrometer (GC-MS). Studies showed that freon release from foams is accelerated by exposure to near UV region of the solar radiation and an increase in temperature. The rate of release of freon from foam was found to be significantly higher at temperatures greater than 70ºC. The release was found to follow first order kinetics with respect to time and temperature.

KEY WORDS

freon, polyurethane foam, experimental model

This paper is from the Proceedings of the 10th Annual Conference on Hazardous Waste Research 1995, published in hard copy and on the Web by the Great Plains/Rocky Mountain Hazardous Substance Research Center.