23rd International Colloquium Tribology - January 2022 87 Development and characterization of Ultra-Low Foaming Metalworking products Bellini Marco Bellini SpA, Zanica (BG), Italy Corresponding author: mbellini@bellini-lubrificanti.it Pota Simone Bellini SpA, Zanica (BG), Italy 1. Introduction The development of low foaming metalworking fluids arises from several reasons. In the last years, there is a tendency to migrate on semi-synthetic MWFs, with a lower oil/ surfactants ratio, and ester-based MWFs that require higher HLB surfactants. These necessities, paired to continuous improvement of additive package and elongation of time of life of emulsions lead sometimes to foaming issues on semi-synthetic MWFs. In addition to this, many filters could gradually remove antifoams from emulsions. If this happen, the effect of antifoam breaks down, causing foaming problems. The idea is to develop products that could counteract this problem by buffering antifoam loss on their own. 2. Results and discussion A deep study on MWFs formulation and components is performed, resulting in long-lasting ultra-low foaming products. Foaming properties are measured with an automatic foam analyser. MWFs optimization goes through two different ways: first optimize the formulation without antifoam and then find the best antifoam. An internal method to check antifoam compatibility is developed while a strong MWFs formulation revision is done. The initial part of this work is dedicated to collecting data and elaborate ad hoc method to reproduce on-the-field feedback of working emulsions. Aging of concentrates, temperature and stress tests are just few of the studied parameters. 2.1 Formulation optimization MWFs have many components used as stabilizers or additives, such as surfactants or phosphate compounds. During this work, each component is analysed in synthesized water (fixed hardness and fixed temperature) to find the most suitable one in terms of foaming properties and surface tension. Figure 1: Foamability of different surfactants Using Design Of Experiment (DOE) technique a new formulative approach is investigated. A fixed starting ‘base product’ is used to develop a new ultra-low foaming MWF. A narrow range of n selected surfactants is used to stabilize MWF concentrate starting from ‘base product’. The first aim is to find more combinations of these n surfactants that can guarantee concentrate stability. After that, a safe area is studied deeper, testing foam performances. The best formulation is a trade-off obtained maximizing concentrate stability response and minimizing foaming. Experimental effort has been reduced by using D-optimal design. 88 23rd International Colloquium Tribology - January 2022 Development and characterization of Ultra-Low Foaming Metalworking products Figure 2: DOE contour plots Generally, MWFs have a strong increase in foam volume after a certain period. This behaviour is enhanced if MWF concentrate is stressed at high temperature. A study on foamability and foam stability before and after concentrates aging is performed. 2.2 Study of antifoams As broadly known one of the most effective class of antifoams is silicon-based products. This class of antifoams often is not compatible with high alkalinity semi-synthetic MWFs. Even if antifoam is highly effective at t=0, incompatibility occurs as flocculation and loss of effectiveness. The more the time passes the higher is the loss in terms of performances. This causes several negative feedbacks on the field that generally intensify during summer period when temperature rises up. Find the best antifoam for a selected formulation means find a trade-off between performances and compatibility. We have studied and developed an internal method to assess compatibility in 7 days using spectroscopy paired to visual check of concentrates. Performances loss is studied collecting several foam data after fixed periods and related to spectroscopic data. Spectroscopic data are collected and the difference between samples with and without antifoam is studied. Collected and elaborated data allow predicting if a selected antifoam will be suitable in a defined MWF formulation. 3. Conclusion This new formulation approach guarantees a strong improvement in foaming properties because of many reasons: selection of low-foaming raw materials, knowledge of components interactions, check of formulation aging, compatibility of selected antifoams, etc. Several comparisons are shown comparing new formulations and old ones. A strong improvement on selected MWFs is achieved.