Researchers at the University of Massachusetts Lowell say they have identified and tested a potential chemical substitute for bisphenol A (BPA) in epoxy.
Use of epoxy in food contact applications, such as can linings, have been under pressure because of concerns about potential health effects of the BPA used to make it. With financial support from the Massachusetts Toxics Use Reduction Institute, the researchers studied a possible alternate--the bis(epoxide) of 2,2,4,4-tetramethyl-1,3-cyclobutanediol.
In a paper presented at ANTEC this month, they said they chose that particular chemical because of "its successful use in Eastman's Tritan resin as a means of enhancing the properties of terephthalate (co)polyesters."
The presence of four methyl groups provides substantial rigidity to the monomer, "while the total absence of any phenolic compounds should substantially limit concerns over estrogenic potential."
Resin viscosity and UV cutoff are lower in the potential replacement plastic and "lap shear adhesion to mild steel is superior, the latter on par with a commercial heavy duty epoxy adhesive. These results indicate promise from this material as a high-performance BPA-free epoxy resin."
BPA is used to produce most polycarbonates, as well as less widely used high-performance engineering thermoplastics such as polysulfones, polyetheretherketones, polyarylates, and polyetherimides.
"The leaching of BPA into foods and beverages, coupled with its structural similarity to estrogen and its endocrine-disrupting potential have resulted in significant consumer and regulatory pressure," the researchers wrote. "The end result has been the phasing out of polycarbonate in baby bottles, water bottles, and food contact items more generally." Medical plastics applications are also under scrutiny.
Substitutions are less complicated in thermoplastics because of a wide number of other materials that could be used. They include polypropylene, cyclic olefin copolymers, copolyesters, and transparent polyamides.
"In contrast to the world of thermoplastics, the replacement of BPA-based thermosets has been much slower, in spite of growing concern over their use in coatings and liners for food and beverage cans." The main reason has been the lack of identified substitutes.
Further work needs to be done on the potential BPA substitute in epoxy, particularly in the area of properties' testing of very pure versions of the material.
Authors of the report are Robert Romano, Smruti Patil and Daniel Schmid of the Department of Plastics Engineering at the University of Massachusetts Lowell, Lowell, MA.
Funding was also provided by the University of Massachusetts Commercial Ventures and Intellectual Property (CVIP) Technology Development Fund.