April 26th, 2021
Efforts are being made across several industries to phase out the use of per- and polyfluoroalkyl substances (PFAS). One such industry is food packaging, where PFAS has been used as a processing aid to produce plastic film. In this blog post, we take a look at the role boron nitride will play in providing a safe and effective polymer processing aid to replace PFAS.
What are PFAS?
PFAS are large class of over 4,700 organofluorine compounds: essentially, these molecules resemble simple hydrocarbons in which several hydrogen atoms have been replaced with fluorine atoms. PFAS find widespread use in industry as an essential polymer processing aid, helping to improve the processing efficiency and quality of plastic products. This means that PFAS are widely used in the production of food packaging materials, including polyethylene film.
In light of recent shifts away from using PFAS, the food packaging industry must find alternative process modifiers in order to meet demand – and boron nitride may offer a solution.
Boron Nitride as a Processing Aid for PFAS-Free Food Packaging
A number of polymer processes require “processing aids” in order to prevent flow instabilities in the molten polymer. These instabilities can result in surface distortions or fractures in extruded polymers – one effect of this is a limit on throughput rate for a number of polymer processes such as the production of food packaging films. This problem is typically solved by the addition of a processing aid – such as fluoroelastomers, a group of polymers classified under PFAS – to the molten polymer.
Substantial historical research shows boron nitride to be a highly effective polymer process aid. Dispersing boron nitride powder into molten polymers has been shown to increase the threshold shear rate at which distortions appear by several orders of magnitude. This essentially means that boron nitride enables order-of-magnitude increases in throughput before distortions and instabilities appear in the polymer. Boron nitride powder has been shown to be effective in the production of films used for food packaging including polyethylene and m-LLDPE films.
Even a small amount of boron nitride, as low as 200 ppm, can significantly delay the onset of both surface and gross melt fracture in polymers during processing, making the production of these materials much faster and more efficient without requiring the use of PFAS. With food packaging manufacturers looking for PFAS-free processing aids, boron nitride is set to have an important role to play in the future of food packaging.
Boron Nitride Powders from Saint-Gobain
Saint Gobain specialize in developing tailored boron nitride solutions for industry. We have been awarded FDA approval to use polyolefin processing for all types of food contact substance (FCS) notifications. To find out more about boron nitride as a polymer processing aid, contact a member of the Saint-Gobain team today.
Glüge, J. et al. An overview of the uses of per- and polyfluoroalkyl substances (PFAS). Environmental Science: Processes & Impacts 22, 2345–2373 (2020)
Kazatchkov, I., Yip, F. & Hatzikiriakos, S. The effect of boron nitride on the rheology and processing of polyolefins. Rheologica Acta 39, 583–594 (2000)
Achilleos, E. C., Georgiou, G. & Hatzikiriakos, S. G. Role of processing aids in the extrusion of molten polymers. J Vinyl Addit Technol 8, 7–24 (2002)
The effect of surface energy of boron nitride on polymer processability - Rathod - 2004 - Polymer Engineering & Science - Wiley Online Library. https://onlinelibrary.wiley.com/doi/abs/10.1002/pen.20151