Conventional metal working fluids are prepared from petroleum based mineral oils with toxic, carcinogenic, non-
biodegradable and unsustainable additives, which can cause serious environmental contamination and health
risks to operators. Formulations with non-toxic emulsifiers and natural additives such as vegetable oils are
currently being considered for further development and use of non-toxic tribological products. This study is
concerned with the thermal and flow properties of a cutting fluid (taladrine, T) mixed with a phase change
material (PCM) coconut oil (CO) in a proportion of 1:9 (CO-0.1T) and hydrophilic silica in 0.01, 0.03 and 0.05
vol fractions. The thermal properties were evaluated by differential scanning calorimetry (DSC) and thermal
conductivity measurements while the flow properties were assessed by viscosity temperature curves. The
addition of solid particles has demonstrated an enhancement of the thermal conductivities with small differences
in the latent heat. The microstructure of the suspensions was established from the DSC cooling dynamic ther-
mogram and the rheological measurements. These results were confirmed by the images of optical polarized
microscopy in which plate-like needles were observed. The suspension of 0.03 silica in CO-0.1T demonstrated an
adequate gel strength and produced a reduction of 11 ◦C in drilling performance. A Minimum Quantity of Cutting
Fluid (MQCF) of 2 g as an alternative for dry machining and flood cooling. It also prevented evaporative loss and
removed metal chips, as a high viscosity complex fluid. In this work the use of phase change materials filled with
solid particles as a way of sustainable eco-friendly toxic waste removal in drilling was justified.
