Manon Saget's thesis

"Surface Engineering of Stainless Steel for Dairy Fouling Management

Defense on Monday, May 2, 2022, at 2:00 p.m.
Amphitheater of the IEMN - Central Laboratory - Villeneuve d'Ascq

Guillaume DELAPLACE, INRAe Research Director, Chairman
Patrick CHOQUET, Research Director, LIST, Luxembourg, Rapporteur
Stéphane VALETTE, University Professor, École Centrale de Lyon, Rapporteur
Olivier FURLING, Doctor, BEL Group, Examiner
Valérie LECHEVALIER, Doctor, Hdr, Agrocampus Ouest, Examiner
Guillaume DAMBLANS, France Énergies Marines, Guest
Vincent THOMY, University Professor, IEMN, Guest speaker
Maude JIMENEZ, University Professor, University of Lille, UMET, Thesis supervisor
Yannick COFFINIER, CNRS Research Director, IEMN, Co-director

Summary:

The dairy industry is heavily affected by fouling in pasteurisation and sterilisation equipment. One of the solutions being considered to limit the adhesion of fouling is to modify the stainless steel surface of heat exchangers. Various types of coating, either limiting adhesion or facilitating cleaning, have previously shown promising results. However, these coatings must be durable and compatible with food. This thesis therefore aims to develop surfaces that are stable, non-toxic and durable at high temperatures and in turbulent conditions. Innovative surface modification techniques were used to design these coatings: (1) deposition of thin layers by atmospheric pressure plasma and (2) bio-inspired sliding surfaces obtained by laser ablation and lubricant infusion/impregnation. The first technique enabled the deposition of thin layers of hexamethyldisiloxane (HMDSO), which facilitates cleaning of fouling but is not very durable.
The alternating deposition of two precursors (HMDSO and 1H,1H,2H,2H perfluorooctyltriethoxysilane) was also studied. This led to the deposition of original, stable and superhydrophobic bilayers. The deposition parameters could be further optimised to improve their cleanability (reduction of fouling after rinsing: 72%). The bio-inspired sliding surfaces (SLIS) were manufactured in three stages: (1) structuring of the stainless steel by laser ablation, (2) chemical modification of the structured surface and (3) impregnation with an oil lubricant. Optimisation of the laser parameters made it possible to rapidly achieve various types of microstructure of different depths. The fluorinated oil usually infused was replaced by coconut oil, making the surface compatible with food contact. Despite poor durability due to oil loss, the slippery surfaces infused with coconut oil made cleaning easier (reduced fouling after rinsing: 114%).

Abstract:

In dairy industries, production costs are highly impacted by the deposition of fouling onto equipment. Promising coatings to prevent fouling adhesion (i.e. anti-fouling) or to ease fouling removal (i.e. fouling-release) were previously developed. Nonetheless, their durability and food-compatibility were limited. Consequently, to overcome these limitations, this work aims at designing coatings based on innovative surface modification techniques and concepts: (1) polymer deposition by atmospheric pressure plasma torch and (2) bioinspired slippery surfaces by femtosecond laser ablation and oil infusion. The first technique allowed the deposition of hexamethyldisiloxane (HMDSO) which demonstrated good fouling-release performances but did not allow the durability improvement.
The alternative deposition of two precursors (HMDSO and 1H,1H,2H,2H perfluorooctyltriethoxysilane) was studied. Superhydrophobic and very stable bilayers were deposited on stainless steel, showing good but still improvable fouling-release properties (fouling reduction of 72%). The second research axis consisted in designing slippery liquid-infused surfaces (SLIS) following three steps: (1) laser structuration of stainless steel, (2) chemical modification of structured surface and (3) lubricant impregnation. An optimization of laser parameters allowed to reach quickly various types of deep microstructures. Food-compatible SLIS were developed by replacing fluorine-based lubricant by coconut oil. Although a poor durability due to a loss of oil, coconut-SLIS exhibited promising fouling-release performances with a fouling deposit reduction of 114%.