Wetenschapsforum

Phthalate Plasticizers

The PVC polymer chains form an attraction to one another, which produces a very rigid plastic. When a soft or flexible plastic is required, a softener or plasticiser is added to allow the chains to slide against each other, providing the desired flexibility. Although a range of chemicals are used as softeners, phthalate esters (phthalates) are by far the most commonly used in PVC. DEHP (Di-Ethylhexyl Phthalate) has been the most commonly used, but in the past few years, DINP (Di-Isononyl Phthalate) has also been used.

Phthalates do not bind to the PVC, remaining present as a freely mobile and leachable phase in the plastic. As a consequence, phthalates are continuously lost from soft PVC over time. DEHP is nearly insoluble in water, but highly soluble in fats and oils. When used in medical tubing, it has been found to accumulate in blood, lung, and liver tissue, as well as in fat. In fatty foods, such as butter, cheese, and prepared meat products packaged in PVC, significant amounts of DEHP or DINP have been found in surface layers. DEHP does not vaporize easily at room temperature, but does migrate out of the plastic as a vapor over 30° C (86° F), and has been found in the air stream of medical respiratory tubing. Under relatively slight pressure, phthalates will exude from PVC. As little as 1.4 lb/sq. inch can result in the loss of 30 percent of the plasticizer.