- February 01, 2003, Dr. Richard M. Podhajny, Ph.D., Contributing Editor
Plasticizers are used extensively to soften plastics, building products, blood bags, cosmetics, and personal care products, as well as packaging inks and coatings. They are commonly found around the home in products such as “cling plastics,” PVC plumbing materials, vinyl floors, and many children's toys. The majority of plasticizers fall into a broad class of chemicals called esters. These include esters such as stearates, citrates, and benzenedicarboxylic acid esters, which generally are referred to as phthalates or phthalate esters.
In recent years phthalate esters emissions have become a major environmental and health concern. Many European countries — including Austria, Belgium, Denmark, England, Germany, the Netherlands, and Spain — have recommended a ban on PVC toys that contain phthalate esters. At issue are health concerns about phthalates. Phthalates also are used extensively in medical and food packaging products. In PVC products, plasticizers account for nearly half of the weight of the plastic and are the primary source of phthalate emissions to the environment. Phthalate esters are one of the most abundant man-made environmental pollutants.
Most phthalate esters are high-boiling liquids that partially “dissolve” the polymer framework of resin polymers and are used to plasticize and reduce the softening point and make polymers pliable. Some plasticizers can volatilize on standing or through heat exposure. Microwave temperatures are sufficient to volatilize phthalate esters.
Phthalate esters vary in their toxicity, but the most widely used phthalate, DEHP [di(-ethylhexyl)phthalate] has been linked in animal studies to damage to kidneys and liver and has been labeled as a probable human carcinogen. It can be passed through skin and mouth or by inhalation. Children are at particular risk since many toys (such as chewable items) are made from PVC. Millions of pounds of DEHP have been released into land and water in the US.
Exposure to phthalates also has been linked to medical devices made from highly plasticized PVC such as PVC respiratory tubes.
While high levels of phthalates seem to be leaching from products such as medical devices, toys, and packaging products, those represent only a small part of the widespread dispersion of phthalates into our environment; fabric, building, and automobiles account for the major phthalate emissions.
Food packaging concerns have been focused recently on the use of phthalate plasticizers in many inks, coatings, and packaging films. These plasticizers are used to add flexibility to resins, such as nitrocellulose. Phthalates can migrate into food from plastics, inks, or coatings. Levels greater than a few parts per million of phthalates can be transferred.
Although alternative plasticizer materials are available, a better approach may be to use modifying resins with lower Tgs as polymeric plasticizers. This approach commonly is used in modifying ink resins to attain adequate flexibility and adhesion to films.
Over the years, packaging's list of approved raw materials has seen many changes. Many products we are using today undoubtedly will be challenged in the future. This is a never-ending cycle, which requires raw material substitutions to protect our customers and employees. Suitable alternates to phthalate esters need to be identified for the various products affected.
The only real security when dealing with packaging product safety lies in the technical competence of your staff and that of your suppliers to provide that added level of safety. Never has it been more important to stay current with governmental regulations and safety product issues. You need to know what you are buying from your supplier. A simple change in plasticizer requires careful testing to assure the product meets your performance specifications and, most importantly, provides the safe use of your product.
Dr. Richard M. Podhajny has been in the packaging and printing industry for more than 30 years. Contact him at 215/616-6314, or via email at email@example.com.