Polymer processing aids (PPAs) reduce and/or eliminate sharkskin melt fracture (MF) instabilities in polyethylene extrusion. This is achieved by increasing the critical flow rate at which MF occurs thus resulting in increased extrusion rate, productivity, as well as reduced energy cost. Fluoropolymers, classified as per- and poly-fluoroalkyl substances (PFAS), have been successfully used as PPAs for several decades but have come under increasing regulatory and consumer scrutiny. Non-PFAS PPAs have been developed and their performance in film extrusion is evaluated in this work. Slip velocity measurements have been carried out using capillary and parallel plate rheometry for the newly developed non-PFAS PPAs as well as a traditional PFAS PPA. A transient flow model has been developed to describe PPA layer thickness build-up and model predictions have been used to correlate experimental observations from time-to-clear (TTC) studies in pilot scale blown film extrusion.
DealyJM. Elements of rheology. In: HatzikiriakosSGMiglerKB (eds) Polymer processing instabilities: control and understanding. 1st ed. Boca Raton: CRC Press, 2020, pp. 13–15.
2.
HatzikiriakosSGMiglerKB. Overview of processing instabilities. In: HatzikiriakosSGMiglerKB (eds) Polymer Processing Instabilities: Control and Understanding. 1st ed. Boca Raton: CRC Press, 2020, pp. 1–11.
3.
BagleyEBBirksAM. Flow of polyethylene into a capillary. J Appl Phys1960; 31(3): 556–561.
4.
VinogradovGVInsarovaNIBoikoBB, et al.Critical regimes of shear in linear polymers. Polym Eng Sci1972; 12(5): 323–334.
5.
BrochardFDe GennesPG. Shear-dependent slippage at a polymer/solid interface. Langmuir1992; 8(12): 3033–3037.
6.
HatzikiriakosSGDealyJM. Role of slip and fracture in the oscillating flow of HDPE in a capillary. J Rheol1992; 36(5): 845–884.
7.
KulikovOLHornungKWagnerMH. Novel processing additives for extrusion and injection of polymers. Advances in Polymer Processing. Woodhead Publishing, 2009, pp. 438–475.
8.
GeorgiouG. Stick-slip instability. In: HatzikiriakosSGMiglerKB (eds) Polymer processing instabilities: control and understanding. 1st ed. Boca Raton: CRC Press, 2020, p. 161.
9.
HatzikiariakosSGMiglerKB. Polymer processing additives for melt fracture control. In: KontopoulouM (ed) Applied Polymer Rheology: Polymeric Fluids with Industrial Applications. 1st ed. John Wiley & Sons, 2011, pp. 29–58.
10.
DealyJMKimS. Gross melt fracture in extrusion. In: HatzikiriakosSGMiglerKB (eds) Polymer Processing Instabilities: Control and Understanding. 1st ed. Boca Raton: CRC Press, 2020, p. 207.
11.
KharchenkoSBMcGuigganPMMiglerKB. Flow induced coating of fluoropolymer additives: development of frustrated total internal reflection imaging. J Rheol2003; 47(6): 1523–1545.
12.
KharchenkoSBMiglerKBHatzikiriakosSG. Conventional polymer processing additives. In: HatzikiriakosSGMiglerKB (eds) Polymer Processing Instabilities: Control and Understanding. 1st ed. Boca Raton: CRC Press, 2020, pp. 244–246.
13.
AmosSEGiacolettoGMHornsJH, et al. Polymer processing aids (PPA) in: zweifel H. Plastic additives Handbook. 5th ed. Hanser Gardner Publications, 2000, pp. 553–584.
14.
XingKCSchreiberHP. Fluoropolymers and their effect on processing linear low‐density polyethylene. Polym Eng Sci1996; 36(3): 387–393.
15.
AchilleosECGeorgiouGHatzikiriakosSG. Role of processing aids in the extrusion of molten polymers. J Vinyl Addit Technol2002; 8(1): 7–24.
16.
OrianiSR. Optimizing process aid performance by controlling fluoropolymer particle size. J Plast Film Sheeting2005; 21(3): 179–198.
17.
OECD. Reconciling terminology of the universe of per- and polyfluoroalkyl substances: recommendations and practical guidance. Paris: OECD Publishing, 2021. DOI: 10.1787/e458e796-en.
18.
SchymanskiELZhangJThiessenPA, et al.Per-and polyfluoroalkyl substances (PFAS) in PubChem: 7 million and growing. Environ Sci Technol2023; 57(44): 16918–16928.
19.
BrennanNMEvansATPeakSA, et al.Trends in the regulation of per-and polyfluoroalkyl substances (PFAS): a scoping review. Int J Environ Res Public Health. 2021Oct17; 18(20): 10900.
YoshimuraAPrud'hommeRK. Wall slip corrections for Couette and parallel disk viscometers. J Rheol1988; 32(1): 53–67.
24.
AnsariM. Rheology and processing of high-density polyethylenes (HDPEs): effects of molecular characteristics. PhD Thesis. Canada: University of British Columbia, 2012.
