What is a food safe epoxy? Do they contain bisphenol A?
What is bisphenol A?
Bisphenol A is an organic synthetic compound used in formulating plastics and epoxy resin. The chemical formula is (CH3)2C(C6H4OH)2. In order to formulate an epoxy adhesive, one must have either bisphenol A or bisphenol F. Bisphenol A (BPA) is generally preferred for its curing properties.
What is a food safe epoxy?
Food grade epoxy and food safe epoxy are general terms. In the US and many other countries, the US Food and Drug Administration (FDA) uses Title 21 Code of Federal Regulations; CFR 175 subsection 105 is Adhesives and subsection 300 is Resinous and polymeric coatings. Each section contains a list of raw materials that are acceptable for use in food contact applications of adhesive. Permabond has several epoxy adhesives that were formulated with FDA approved raw materials. These adhesives comply with CFR 175.105 and 175.300 and are ideal for bonding and sealing food contact equipment and appliances. 2-Part epoxy adhesives offer a quick and easy way of bonding a wide variety of plastics, metals, composites, ceramics, and glass. They allow accurate alignment of parts and, if necessary, can be cured quickly by applying heat. They cure to form a high strength rigid solid which is non-porous and can be easily cleaned. They offer excellent resistance to water, food, cleaning fluids, and heat. For product details contact Permabond.
Do food safe epoxies contain bisphenol A?
As mentioned, to formulate an epoxy adhesive, one must have either bisphenol A or bisphenol F. Bisphenol A (BPA) is generally preferred for its curing properties. The FDA has said that BPA is safe at the very low levels that occur in some foods. However, the FDA is continuing its review of BPA.
Bisphenol A has been used since the 1960’s to create polycarbonate plastics and epoxy resins. The CDC reports that detectable levels of BPA were found in 93% of 2517 urine samples from people six years and older. There is concern over limiting exposure to BPA due to studies that show it may be related to health effects. Concerned? Here are a few ways to reduce bisphenol A exposure.
- Plastics marked with recycle code 3 or recycle code 7 might be made with bisphenol A. So if they aren’t marked BPA-free you might want to avoid them.
- Epoxy resins are used to coat the inside of metal food containers – like canned food and metal bottle caps. These epoxy applications provide much more opportunity for the BPA to leach into food than a bonded joint. If you are concerned, reduce or eliminate your use of canned foods.
- Keep a plastic or resin containing bisphenol A away from heat sources, as heat can encourage leaching. For example, do not leave water bottles made with BPA in your car, even in winter.
If you are manufacturing an item that requires a food safe epoxy adhesive, (again that means one that is made with ingredients listed in the FDA CFR 21 175.105 and/or 177.300), epoxy is your only option.
We are often asked for food safe adhesives that are not epoxy, such as UV curable or instant adhesives (cyanoacrylates). It is not possible to make a UV or Cyanoacrylate from the FDA list of raw materials as the list does not contain the raw materials required.
Some minimal leaching of uncured monomer can occur in any curing system as some monomers may not crosslink. These remain in the polymer matrix but are not linked to it and are free to move around and eventually leach out of the system. Although specific data related to each application is not possible, it is generally expected to be less than 100 ppb.
What can be done to minimize bisphenol A leaching out of your manufactured item?
- Be certain to mix the epoxy thoroughly. If using bulk food safe epoxy – ensure accurate measuring and thorough mixing. If using a static mixer nozzle, be sure to completely fill the static mix nozzle and waste a bead of an inch or two until the static mix nozzle is uniformly filled.
- Design joints with a barrier such that minimal gap or minimal amount of epoxy is exposed to the food.
The vast majority of food contact with BPA is a long-term continuous contact of food or water packaged in a plastic containing BPA or a can lined with BPA-containing epoxy. Although there is BPA in food grade epoxy used for bonding food equipment, the relatively small contact area of a bond joint in food equipment and the short duration contact of food items during food processing equipment use contribute to this contact being minimal.
For assistance in designing an adhesive into your food contact application, please contact our technical team.