Stability of nonfouling electroless nickel-polytetrafluoroethylene coatings after exposure to commercial dairy equipment sanitizers

Abstract

Application of nonfouling coatings on thermal processing equipment can improve operational efficiency. However, to enable effective commercial translation, a need exists for more comprehensive studies on the stability of nonfouling coatings after exposure to different sanitizers. In the current study, the influence of different commercial dairy equipment sanitizers on the nonfouling properties of stainless steel modified with electroless Ni-polytetrafluoroethylene (PTFE) coatings was determined. Surface properties, such as dynamic contact angle, surface energy, surface morphology, and elemental composition, were measured before and after the coupons were exposed to the sanitizers for 168 cleaning cycles. The fouling behavior of Ni-PTFE-modified stainless steel coupons after exposure was also evaluated by processing raw milk on a self-fabricated benchtop-scale plate heat exchanger. The results indicated that peroxide sanitizer had only minor effect on the Ni-PTFE-modified stainless steel surface, whereas chlorine- and iodine-based sanitizers influenced the surface properties drastically. The coupons after 168 cycles of exposure to peroxide sanitizer accumulated the least amount of fouling material (4.44±0.24mg/cm(2)) compared with the coupons exposed to the other 3 sanitizers. These observations indicated that the Ni-PTFE nonfouling coating retained antifouling properties after 168 cycles of exposure to peroxide-based sanitizer, supporting their potential application as nonfouling coatings for stainless steel dairy processing equipment.

Hybrid Antifouling and Antimicrobial Coatings Prepared by Electroless Co-Deposition of Fluoropolymer and Cationic Silica Nanoparticles on Stainless Steel: Efficacy against Listeria monocytogenes

“…Native stainless steel presented regular cracks and crevices typical of 2B finished 316 SS (Figure A). Inclusion of PTFE NPs alone (no SiO 2 @PEI NPs) resulted in a uniform deposition, indicated by dark spots ∼200 nm diameter, in agreement with prior reports . Introduction of SiO 2 @PEI NPs to the Ni-PTFE coating resulted in a uniform embedding of both particle types within the coating, evidenced by presence of both darker (from PTFE NPs) and lighter (from SiO 2 @PEI NPs) gray spheres uniform within the nickel plated coating.…”

“…Coating of PTFE nanoparticles alone (no SiNP + ) resulted in a significant increase in hydrophobicity with both advancing and receding contact angles significantly higher than those of native stainless steel. The Ni-PTFE composite coating further exhibited a significant reduction in surface energy (from >30 mN/m in native steel to 22 mN/m in Ni-PTFE coated steel), in agreement with prior reports on the antifouling character of Ni-PTFE coatings . Coating of SiNP + alone (no PTFE nanoparticles) resulted in a noted decrease in hydrophobicity and corresponding increase in surface energy, compared to that of native stainless steel, as expected due to the introduction of highly hydrophilic primary amine decorated silica nanoparticles.…”

“…Three measurements were performed at three separate areas for each test coupon, and three individual coupons for each surface were analyzed. Surface energies were quantified using a Neumann model as described in previously published work. , …”

“…Surface energies were quantified using a Neumann model as described in previously published work. 25,26 As a complementary source of coating characterization, coupons of native and modified stainless steel were analyzed using X-ray photoelectron spectroscopy, on a Physical Electronics Quantum 2000 (Physical Electronics, Chanhassen, MN, USA). A single 100 μm spot was analyzed from every coupon at an angle of 45°relative to the coupons' surface with Al Kα excitation.…”

Solid–Liquid–Liquid Wettability of Surfactant–Oil–Water Systems and Its Prediction around the Phase Inversion Point

“…Stainless steel is widely used in food and dairy industry as well as in many applications in the oil and gas industry, such as pipelines and heat exchangers. Finally, PTFE is used in coating applications, , and it is one of the benchmark materials used in wettability studies.…”