Polyethylene-2,6-naphthalene dicarboxylate is a recently commercialized polyester resin referred to as PEN. PEN is mainly produced by the poly-condensation of 2,6-napthalene dicarboxylate or its derivative, naphthalene-2,6-dicarboxylic acid, with ethylene glycol via a catalyst under appropriate reaction conditions . The method of production is dependent on whether the ester or the acid derivative is being used. Once produced through condensing polymerization, producers melt the resin into its desired form, usually a film for post-production use. PEN exhibits physical and chemical properties that make it ideal for plastic applications. As its commercial popularity grows and it is more easily produced, PEN has many applications including but not limited to high performance fibers and films used in packaging.

Polyethylene naphthalene is commercially valued for its many characteristics. Its low permeability, higher temperature resistance, and stability make it very useful for many packaging applications. One of these applications it bottling beverages, both carbonated and non-carbonated. It is currently gaining popularity for its ability to be hot filled and to preserve the contents of containers lined with PEN film . It is also popular in the food packaging industry of being used as a barrier to reduce permeability of gases, flavors, and vapors in to or out of containers. PEN films are used for flexible food packaging because they add durability and strength to the package. Due to its dielectric insulating properties PEN is being favored in electrical insulation and barrier applications as well as advanced photography and imaging purposes. It is also used to make thermal sheets. Due to its resistance to oxidation and ultraviolet light, PEN applications for a number of packaging purposes are being explored such as coating protective solar cells and containers that contain photosensitive materials.

While PEN is structurally similar to the widely used polyethylene terephthalate, commonly referred to as PET, it is a slightly superior polymer. PEN shows increased strength, temperature resistance, and better dimensional stability when compared to PET . In packaging applications, this makes it an ideal material for using hot-filling for sterilization as in the case of bottled beverages or beer. It is less permeable to oxygen and water vapor which makes it ideal for barrier applications . The reduction in oxidation effects on products in PEN containers makes it appealing to those who wish to preserve food products longer. PEN is highly valued as a barrier because it retains it barrier properties even upon bending and flexing . This is why it is gaining popularity in the food packaging industry . As manufacturer’s look for a quality cost effective means of packaging food they could turn to PEN. From bags of potato chips to beer cans, PEN offer superior product protection for the contents of the film lined containers. Thin, durable, flexible film coating that protects the contents of a package from moisture and chemical gases and vapors is a packaging engineer’s idealistic polymer for its many uses. PEN meets all of these requirements as well as being light weight and visibly attractive enough to rival PET.

PEN also has a higher glass transition temperature and also shows improved dielectric capabilities based on the crystalline molecular structure created by appropriately aligning the substance during formation . Those in the electronics industry have examined that PEN can be used to make capacitors and storage devices such as USBs. It can also be used to coat electrical circuit boards while still allowing them to be flexible.

PEN has many equivocal or similar inherent properties compared to PET. One of the key benefits to using PEN is that it can fulfill many of the same purposes as PET, making it comparable polymer. Yet, less material is required using PEN to achieve the same criterion as PET. For example, a film made of PEN may have the same tensile strength, resistance, and permeability as a film made from PET; but the film made from PEN would be narrower and thinner than that made from PET. Copolymers of PEN and PET show improved properties as well such as impermeability by ultraviolet light, gases, chemicals, and water vapor. These properties of copolymer resins are attributed to PEN’s contribution to the mixture.

Due to its costly production, PEN has been classified as a specialty polymer. However, new research and raw material availability is making it a more commercialized plastic due to its high performance qualities.

There are multiple methods to determining ways to make PEN more cost effective. It is preferable to PET, but the former lack of raw materials and the cost of production formerly limited it to a specialty polymer only used in certain critical applications. Since 2006, Google Patents has registered an innumerable number of multilayered packaging techniques. There is evidence of PEN being used in both plastic packaging applications and electrical applications. Both the electronics industry and the packaging industry are trending upwards in manufacturing and profitability and it should be expected that as time and technology progress, PEN applications will grow as well. PEN production is projected to increase into commonplace practice and possibly replace PET once its production and distribution can be proven to be a cost effective alternative to the applications of PET in packaging, apparel, film, coating etc.

References

Ghai, Lekharaj, “Polyethylene Naphthalate- A New Generation, High Performance Polymer”, Polymer Update, p.1

Ibid, p. 2

Ebnesajjad, Sina, Plastic Films in Food Packaging: materials, Technology, and Applications, p,5-6.

Bertrand, J.A., and D.J. Higgs, M.J. Young, and S.M. George, “H2O Vapor Transmission Rate through Polyethylene Naphthalate Polymer using Electrical Ca Test”, The Journal of Physical Chemistry A, 117:46, July 30, 2013, p.12026-12034, DOI: 10.1021/jp40430574

Groner, M.D., and S.M. George, R.S. McLean and P.F. Carcia, “Gas Diffusion Barrier on Polymers using Al2O3 Atomic Layer Deposition”, Applied Physics Letters: 88,2006, DOI: 10.1063/1.2168489 . 5

Siracusa, Valentina “Food Packaging Permeability Behaviour: A Report,” International Journal of Polymer Science, vol. 2012, Article ID 302029, 11 pages, 2012. doi:10.1155/2012/302029

Yang,Peng, Ohki. Y., Fuqiang Tian, “Analysis on Thermally Stimulated Currents in Polyethylene-terephthalate and Polyethylene-naphthalate”, Electrical Insulating Materials (ISEIM): Proceedings of 2014 International Symposium, IEEE, DOI: 1109/ISEIM.2014.6870804