2 nd International Conference on Sustainable Energy and Resource Use in Food Chains How might surface properties affect cleaning performance? Alejandro Avila-Sierra*, Zhenyu J. Zhang, Peter J. Fryer University of Birmingham, United Kingdom Cyprus , 2018 RCUK Centre for Sustainable Energy Use in Food Chains
2 nd International Conference on Sustainable Energy and Resource Use in Food Chains Cleaning in place system (CIP) Example of CIP system. Image from Sanimatic RCUK Centre for Sustainable Energy Use in Food Chains Alejandro Avila-Sierra axa1312@student.bham.ac.uk 2
2 nd International Conference on Sustainable Energy and Resource Use in Food Chains Fouling problems - Depends on the type of product processed and surface - Fluid Flow – Pipes – Foulant Deposit Deposition Removal Substrate - Stainless steel 304/316L - Schematic diagram of foulant deposition Types of foulant. Image from Laboratory of Colloid and Surface Chemistry (LCSC) RCUK Centre for Sustainable Energy Use in Food Chains Alejandro Avila-Sierra axa1312@student.bham.ac.uk 3
2 nd International Conference on Sustainable Energy and Resource Use in Food Chains Fouling on heat exchanger - Dairy industry - Milk fouling after 8 hours processing on heat exchanger before (A & C) and after anti-fouling coating (B & D) application. Image from Anti-Fouling, Heat Exchanger Solutions Inc. RCUK Centre for Sustainable Energy Use in Food Chains Alejandro Avila-Sierra axa1312@student.bham.ac.uk 4
2 nd International Conference on Sustainable Energy and Resource Use in Food Chains Key question: -To understand what we have -To know what we can do How might surface Natural characteristics of each substrate: properties Surface free energy (related with composition) affect cleaning performance? External variables (can be modified): Surface temperature (25-80 ° C) Topography of the surface – Roughness (Ra<0.8µm) RCUK Centre for Sustainable Energy Use in Food Chains Alejandro Avila-Sierra axa1312@student.bham.ac.uk 5
2 nd International Conference on Sustainable Energy and Resource Use in Food Chains Surface roughness (B) (A) Surface roughness of the used surfaces: • mirror (A) [Ra 0.0295 ± 0.0045µm] • satin (B) [Ra 0.3090 ± 0.0095µm] • brush (C) [Ra 0.8250 ± 0.1276µm] Characterised by Interferometry. (C) RCUK Centre for Sustainable Energy Use in Food Chains Alejandro Avila-Sierra axa1312@student.bham.ac.uk 6
2 nd International Conference on Sustainable Energy and Resource Use in Food Chains Wettability of liquids - Liquids selected - Polar Non-polar • • Ethylene glycol Diiodomethane • • Distilled Water 1-Bromonaphthalene Liquids commonly used to characterise Surface Free Energy Boiling point ( ° C) Liquid Surface tension (mN/m) Ethylene glycol 197 47.47 Diiodomethane 181 50.00 1- Bromonaphthalene 135 44.63 Water 100 72.10 Boiling temperature and surface tension of liquids tested. Surface tension measured at room temperature. RCUK Centre for Sustainable Energy Use in Food Chains Alejandro Avila-Sierra axa1312@student.bham.ac.uk 7
2 nd International Conference on Sustainable Energy and Resource Use in Food Chains Equilibrium Contact Angle - Method - • Atmospheric pressure • No saturation conditions • Temperature range: 25 - 80 ° C 10µL of liquid • Liquid drop is sufficiently small to avoid gravity effect Stainless steel coupon High Speed Camera (1000fps) Heating stage Thermal bath RCUK Centre for Sustainable Energy Use in Food Chains Alejandro Avila-Sierra axa1312@student.bham.ac.uk 8
2 nd International Conference on Sustainable Energy and Resource Use in Food Chains ECA measurements 50 40 Contact angle (°) Contact angle (°) 40 30 30 20 Equilibrium contact angle of liquids as a function of temperature on three different 20 10 types of polished surfaces: 20 40 60 80 20 40 60 80 (A) (B) Temperature (°C) Temperature (°C) Mirror 80 50 Satin Brush Contact angle (°) Contact angle (°) 70 Liquids tested: 60 40 • Ethylene glycol (A) • 1-Bromonaphthalene (B) 50 • Diiodomethane (C) • Distilled water (D) 40 30 20 40 60 80 20 40 60 80 (C) (D) Temperature (°C) Temperature (°C) RCUK Centre for Sustainable Energy Use in Food Chains Alejandro Avila-Sierra axa1312@student.bham.ac.uk 9
2 nd International Conference on Sustainable Energy and Resource Use in Food Chains Modelling -ECA as a function of temperature- As shown in previous studies [1][2], it is possible to describe the contact angle’s temperature dependence of liquids on several substrates. • The sharp-kink approximation (SK) [1] (considering only Van der Waals type forces): cos θ = −1 + ∆ρ· I / γ lv (Eq. 1) • Decreasing Trend Model (DTm) [2] . The model has two formulations depending on the type of liquid used, non-polar (Eq. 2) or polar (Eq. 3). Surface tension of the solid can be extrapolating from ambient conditions. 𝛿 𝑡𝑤 cos𝜄 = −1 + 2 · (Eq. 2) 𝛿 𝑚𝑤 𝐸 𝑄 𝛿 𝑚𝑤 𝛿 𝑚𝑤 2 𝐸 ∙ 𝑄 ∙ cos𝜄 = −1 + ∙ 𝛿 𝑡𝑤 𝛿 𝑚𝑤 + 𝛿 𝑡𝑤 (Eq. 3) 𝛿𝑚𝑤 𝛿 𝑚𝑤 R. Garcia, K. Osborne, and E. Subashi, “Validity of the ‘ Sharp-Kink Approximation ’ for Water and Other Fluids,” J. Phys. Chem. , vol. 112, pp. 8114 – 8119, 2008. [1] F. Villa, M. Marengo, and J. De Coninck, “A new model to predict the influence of surface temperature on contact angle,” Sci. Reports Nat. , vol. 8, no. 6549, pp. 1 – 10, 2018. [2] RCUK Centre for Sustainable Energy Use in Food Chains Alejandro Avila-Sierra axa1312@student.bham.ac.uk 10
2 nd International Conference on Sustainable Energy and Resource Use in Food Chains Modelling 80 80 Contact angle ( ⁰ ) 60 60 Contact angle ( ⁰ ) A & B) Modelling of ECA average 40 40 as a function of wall temperature for real food-contact surfaces (Ra<0.8 20 20 µm). Liquids tested: 0 0 Water 20 40 60 80 20 40 60 80 (A) (B) Diiodomethane Temperature (⁰C) Temperature (⁰C) 1-Bromonaphthalene □ Ethylene glycol 80 80 C & D) Modelling of water ECA as a 70 70 Contact angle ( ⁰ ) Contact angle ( ⁰ ) function of both wall temperature and surface roughness: 60 60 Mirror Satin 50 50 Brush 40 40 20 30 40 50 60 20 30 40 50 60 SK approximation model (A and C). Temperature (⁰C) DT model (B and D). Temperature (⁰C) (C) (D) RCUK Centre for Sustainable Energy Use in Food Chains Alejandro Avila-Sierra axa1312@student.bham.ac.uk 11
2 nd International Conference on Sustainable Energy and Resource Use in Food Chains Characterisation of SFE -Methods- In this work, 1- bromonaphthalene and ethylene glycol were the liquids selected to characterise solid SFE with polar and disperse components. The two methods used to calculate and compare SFE are: • Owens & Wendt method and Wu method [3] 𝛿 𝑚𝑤 1 + 𝑑𝑝𝑡 θ = 2 𝛿 𝑡𝑤𝐸 ∙ 𝛿 𝑚𝑤𝐸 + 2 𝛿 𝑡𝑤𝑄 ∙ 𝛿 𝑚𝑤𝑄 • Wu method [4][5] 𝐸 ∙ 𝛿 𝑚𝑤𝐸 𝛿 𝑡𝑤𝐸 + 𝛿 𝑚𝑤𝐸 + 4 ∙ 𝛿 𝑡𝑤𝑄 ∙ 𝛿 𝑚𝑤𝑄 𝛿 𝑚𝑤 1 + 𝑑𝑝𝑡 θ = 4 ∙ 𝛿 𝑡𝑤 𝛿 𝑡𝑤𝑄 + 𝛿 𝑚𝑤𝑄 γ lv : Surface tension liquid-air; θ : equilibrium contact angle; γ sv : surface tension sol d−air Wu harmonic mean model often provides more reliable values between both parts -for low surface free energies systems (up to 40 mJ/m 2 ), than the geometric mean approach. D. Owens and R. Wendt, “Estimation of the surface free energy of polymers,” J. Appl. Polym. Sci. , vol. 13, no. 8, pp. 1741 – 1747, 1969. [3] S. Wu, “Calculation of interfacial tension in polymer systems,” J. Polym. Sci. Polym. Symp. , vol. 34, no. 1, pp. 19 – 30, 1971. [4] S. Wu, “Polar and Nonpolar Interactions in Adhesion,” J. Adhes. , vol. 5, no. 1, pp. 39 – 55, 1973. [5] RCUK Centre for Sustainable Energy Use in Food Chains Alejandro Avila-Sierra axa1312@student.bham.ac.uk 12
2 nd International Conference on Sustainable Energy and Resource Use in Food Chains Characterisation of SFE 50 50 40 40 Solid SFE (mN/m) Solid SFE (mN/m) 30 30 20 20 10 10 0 0 20 40 60 80 20 40 60 80 Temperature ( ° C) Temperature ( ° C) (A) (B) Average of solid surface free energy as a function of temperature on three different types of polished surfaces. • Total SFE • Polar part • Disperse part Liquids tested: Ethylene glycol and 1-Bromonaphthalene. Methods: Owens & Wendt (A); Wu method (B). RCUK Centre for Sustainable Energy Use in Food Chains Alejandro Avila-Sierra axa1312@student.bham.ac.uk 13
2 nd International Conference on Sustainable Energy and Resource Use in Food Chains SFE as a function of roughness 3% SFE increase 2% 1% 0% 0 0.2 0.4 0.6 0.8 Ra (µm) Surface free energy increase (%) of SS316L as a function of surface roughness. Methods: Owens &Wendt method Wu method Liquids tested: Ethylene glycol and 1-Bromonaphthalene. RCUK Centre for Sustainable Energy Use in Food Chains Alejandro Avila-Sierra axa1312@student.bham.ac.uk 14
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