ICMCTF 2025 Session TS3-TuA: Circular Strategies for Surface Engineering

Current industrial processes for power, fuel, and commodity production are responsible for massive, ongoing CO₂ emissions that adversely affect the stability of Earth’s climate with potentially disastrous consequences. Increased use of hydrogen as a fuel and chemical building block promises to reduce CO₂ emissions in critical sectors, but contemporary hydrogen production technologies also involve high greenhouse gas emissions. This talk considers a process in which concentrated radiation from a simulated solar source converts methane and similar hydrocarbons to high-value synthetic flake graphite and hydrogen gas. Methane flows within a photo-thermal reactor through the pores of a thin substrate irradiated by several thousand suns at the focal peak. The methane decomposes primarily into hydrogen while depositing highly graphitic carbon that grows conformally over ligaments in the porous substrate. The direct heating of the porous substrate serves to capture the solid carbon into a readily captured and useful form while maintaining active deposition site density with persistent self-catalytic activity. The talk will cover topics including solar irradiation profile modeling and measurements, chemical kinetics, gas-phase diagnostics, material characterization, product yields, and solar-to-chemical efficiency.

Flexible food packaging materials are complex surface engineered products that must meet demanding quality criteria yet be produced at very high volume and low cost. Until recently, typical flexible packaging material might consist of an inner heat sealable polyethylene (PE) film, then combinations of adhesives to hold the laminated structure together, inks for printing product details, a topcoat, a barrier layer and finally an outer polymer film, such as polyethylene terephthalate (PET). The barrier layer provides extended shelf life to the food product by preventing moisture and oxygen ingress, which spoils the product over time. Barrier layers can be organic layers (e.g. polyvinylidene chloride (PVdC)) deposited by wet chemical techniques, aluminium foil layers or as in the case here, either aluminium or aluminium oxide (‘AlOx’) coatings deposited by thermal evaporation techniques. These coatings are deposited at very high rates (line speeds are up to 1000m/min) and over very large areas (up to 4.85m wide x 100km long rolls) in roll-to-roll vacuum systems. Average barrier layer thicknesses are 40-50nm for Al films and 8-15nm for AlOx layers.

As a consequence of the mixed materials used in conventional flexible packaging, most products cannot be recycled and go to landfill or are incinerated. The increasing demand for sustainable packaging products has led Bobst and other companies in the packaging value chain (ranging from raw material producers and convertors to brand owners and retailers) to develop new products that meet the criteria of ‘recyclable, reusable or compostable’.

This paper describes progress towards mono-material polyolefin-based solutions for fully recyclable polymeric packaging and paper-based products, which are suitable to be processed in the existing paper recycling stream. In both cases, the Bobst oneBARRIER PrimeCycle PE product and the FibreCycle paper-based product provide high barrier performance and meet international recyclable standards. In addition to the development of these products, extensive life cycle analyses (LCAs) have been undertaken on each stage of the manufacturing process to allow accurate and comparable assessments to be made of the environmental impact and sustainability of the product.

Per- and polyfluoroalkyl substances (PFAS) are a large class of thousands of synthetic chemicals currently used in a wide variety of products (e.g. food packaging, cookware, textiles, medical devices, semiconductor components, batteries, among many others). PFAS contain carbon-fluorine bonds, which are one of the strongest chemical bonds in organic chemistry, meaning they are very attractive in different consumer products as they can resist to degradation. Nevertheless, the degradation resistance also persists once they are disposed. Currently PFAS are increasingly detected as environmental pollutants and some are linked to negative effects on human health, which has led to the current restriction proposal by European Chemical Agency (ECHA).

The restriction on use of PFAS will require the development of new solutions, which must fulfill health and environmental requirements. Medical devices are one of the main fields of use of PFAS, where PTFE based coatings are widely used, among many applications as anti-stick coatings in electrosurgical devices. In the current work existing coating solutions already in use for medical market and approved by regulatory authorities (e.g. FDA) have been tested (e.g. TiN, CrN, DLC, Parylene C) and compared to new coating solutions under research and development. The main goal is to obtain coatings with good anti-stick performance, which ideally can be re-used as multiple use devices, opposed to concept of single-use devices, which are discarded after each surgery generating large amount of waste. In order to fulfill the requirements for multiple use devices the coatings must stand multiple cleaning and sterilization cycles meaning they must have good corrosion properties as well as good abrasion resistance.

In the present study the coatings are characterized regarding their surface energy given that this surface property is connected with anti-sticking properties, and also functional tests are performed in a test set-up consisting of an electrosurgical unit (ESU) where coatings anti-stick performance is tested against pork liver. Additionally, the corrosion and abrasion resistance of the coatings are evaluated under autoclave and alkaline cleaning conditions and under abrasive cleaning test condition in order to resemble the lifecycle of multiple-use electrosurgical devices.

From the more than 500 EJ of the World energy consumption, 20% regards losses due to friction in mechanical contacts¹. The obvious solution to decrease friction, the use of liquid lubricants, rises increasing concerns to the environment due to their harmful impact. Therefore, alternatives that can either provide a decrease of the friction in solid contacts or a reduction/removal of the usage of liquid lubrication, will have a significant and positive impact in both saving of energy and protection of the environment.

Low friction coatings were intensively developed in last decades as solutions for applications where liquid lubrication is restricted (space, food industry, vacuum,…) as well as a tool for removing either the usage of liquid lubrication or the extremely harmful additives of lubricant oils. As friction is a surface phenomenon, the main advantage of low friction coatings is that they can be applied over the currently used materials for mechanical applications without significant changes of the components and devices.

In this talk several examples related with the development and application of sputtering coatings in mechanical applications (moulding, cutting, forming,…) with main objectives of decreasing friction and reducing the harmful impact of oil lubricants, will be presented. The sliding mechanisms, in particular the understanding of tribolayers formation, will be addressed and connected to different concepts which were in the basis of the coatings development.

¹ K. Holmberg, A. Erdemir, Influence of tribology on global energy consumption, costs and emissions, Friction 5 (2017) 263–284