POLYMER STABILIZED NANOPARTICLE CONTAINING COMPOSITIONS FOR

USE AS CUTTING FLUIDS AND/OR COOLANTS

RELATED APPLICATIONS

[0001 ] The present application claims the benefit of priority from co-pending U.S. provisional patent application no. 62/557,966 filed on September 13, 2017, the contents of which are incorporated herein by reference in their entirety.

FIELD

[0002] The present application relates to cutting fluid and/or coolant compositions, in particular cutting fluid and/or coolant compositions comprising one or more superabsorbent polymers and one or more nanoparticles, and to methods of making the same, and to their use in manufacturing processes.

BACKGROUND

[0003] Cooling is one of the most critical challenges in the machining process faced by numerous industries where the machining process is used, such as the automobile industry. In recent years, methods such as cryogenic cooling, high-pressure coolants, flood cooling, minimum quantity lubrication (MQL/MQCL), and solid lubricants have been developed to increase the overall effectiveness of the machining process. However, each of these methods are associated with drawbacks.

[0004] Winter et al. [1 ] studied the application of glycerol-based coolants in the inner cylindrical grinding of hardened carbon alloy steel. Two different wheels, CBN and AI2O3, were used with the glycerol coolant and results were compared to grinding oil and mineral based emulsions. The glycerol-based fluid showed better surface finish, and less grinding wheel wear compared with other cutting fluids. Application of metalworking fluids can cause noticeable results at higher material removal rates rather than lower ones.

[0005] Grosse et al. [2] conducted honing on grey cast iron with a different type of lubricant, known as polymer dilution, with various concentrations, rotational speeds, and contact pressures to find out which concentration results in the best performance. Results revealed that increasing the polymer concentration leads to better surface finishes at higher rotational speeds. However, at low rotational speeds and contact pressures, up to 5% polymer concentration shows lower honing stone wear.

[0006] However, less focus has been given to flooding techniques due to environmental restrictions, and health and safety concerns. Alternatives to flood cooling are sought to lower costs of purchase and disposal of cutting fluids, as well as to reduce environmental and health impacts [3-6].

[0007] Liao et al. [7] applied minimum quantity lubrication (MQL), in high-speed end milling of NAK80 hardened steel with coated carbide tools. Their results show that, despite the positive effect of MQL on the finished surface and tool life, it was unsuccessful in decreasing the cutting forces compared to flood cooling across all milling speeds.

[0008] In the cryogenic approach, liquid nitrogen at -196°C is applied as a cooling agent and is practical for almost all types of materials. Liquid nitrogen absorbs heat and evaporates into the air, so it is beneficial in decreasing diffusion related tool wear [8]. This method directly addresses the environmental concerns associated with coolant disposal because it does not generate any waste or extra residuals [9].

[0009] Kaynak et al. [10] machined the difficult-to-cut Inconel 718 alloy to compare cryogenic machining with MQL and dry conditions. The experiments reported in this document showed that applying MQL at the low cutting speed of 60 m/min resulted in more moderate cutting force than cryogenic or dry machining. However, at high cutting speed (120 m/min) the force components in cryogenic machining were lower than in the other two methods. Neither of the chosen methods reduced the progressive notch wear or chip breakability. It was also mentioned that the main drawbacks of using the cryogenic method are the high cost of liquid nitrogen and the need to precool the workpiece, which can lead to hardening of the workpiece material and dimensional variation during machining. In most of the scientific notes, MQL machining is known as an environmentally friendly technique. However, this technique does not protect operators from respiratory diseases, because some of the cutting fluid is evaporated on exit from the nozzle and distributed by airflow around the machine, which is harmful to the operator's health. Another drawback of MQL is its requirement of expensive and noisy equipment [1 1 ].

[0010] Bermingham et al. [12] evaluated tool life and chip morphology with cryogenic and high-pressure cooling when turning Ti-6AI-4V and found that both methods improve tool life compared to dry conditions, but that neither was able to reduce the cutting temperature sufficiently to prevent diffusion. It was also noted that cryogenic cooling is more sensitive to nozzle position than high-pressure emulsion.

[001 1 ] Li et al [13] compared six different nanofluids in vegetable-based oil with MQL techniques on the nickel-based alloy. It was found that carbon nanotubes (CNT) produced the lowest grinding temperature because of the high thermal conductivity of CNT, which served to transfer heat faster from the grinding zone and also because of the low surface tension and large contact angle that CNT particle-rich fluids provide when compared to other nanofluids. Micro-drilling of aluminum 6061 with nanofluids (NFs) applied by MQL indicated that nano-diamond particles in paraffin oil-based liquids decreased the drilling forces and torques as well as increased the quality of the drilled holes. It was determined that nanoparticles, in this case, prevent chip adhesion to the drill [14]. However, sedimentation and high cost present a big challenge for nanofluids. Moreover, certain nanoparticles are harmful to human health. [15, 16]

[0012] Table 1 summarises the challenges of various cooling techniques used in the machining process.

Table 1 - Different cooling techniques and drawbacks

[0013] To develop and increase the efficiency of manufacturing processes, various techniques have been incorporated into machining. For instance, the inherent heat generated during the high-speed material removal, the need to reduce the friction between the tool and workpiece, and the demand for more top quality surfaces of final products has led to the use of cutting fluids as coolants and lubricants during machining. In fact, many operations cannot be carried out without the use of coolants. Cutting fluid is a coolant and lubricant applied during the machining processes to improve the tribological conditions between the tool, chip, and workpiece, to stabilize the temperature in the cutting zone (to avoid fluctuation and reduce heat generation) and to facilitate chip removal.

[0014] Cutting fluid has become one of the most important parts of the manufacturing processes, yet it only accounts for between 7 to 17% of the total production costs. There are many issues hindering the use of cutting fluids in manufacturing. Two of the most prominent reasons deterring the usage of coolants include environmental restrictions, and occupational health and safety concerns. As a result, manufacturers continue to seek out safer and more economical techniques to improve their production process.

SUMMARY

[0015] Superabsorbent coolant (SAC) is an approach to increasing tool life and machining performance significantly while simultaneously reducing environmental and occupational health concerns about cutting fluids. SAC can also be used for various manufacturing processes from drilling to milling and even forming. Superabsorbent polymers, including hydrogels, are materials that can absorb liquids hundreds of times their own weight. When operating temperatures reach a particular point they start to release their absorbed liquid. This ability can be exploited for cooling and lubrication of tools during machining.

[0016] Commercial semi-synthetic cutting fluids or vegetable based coolants (10% oil + 90% water) plus certain amounts of lubricious nanoparticles can be added to superabsorbent particles. The resulting SAC takes on a gel like consistency and can be used for semi-dry machining. When SAC is applied on the tool or workpiece it slowly releases its component ingredients in the cutting zone as the tool temperature increases, which helps the tool work at a lower temperature. This in turn decreases friction between tool and chip, creating optimal cutting conditions and results in a better overall finish on the workpiece.

[0017] Accordingly, the present application relates to cutting fluid and/or coolant compositions comprising one or more superabsorbent polymers, one or more nanoparticles, one or more water-soluble oils and water. The present application also relates to methods of making the cutting fluid and/or coolant compositions. Further, the present application relates to the use of the cutting fluid and/or coolant compositions for manufacturing processes such as cutting, machining, drilling, milling, turning, and forming. [0018] In one aspect, the present application relates to cutting fluid and/or coolant compositions of comprising:

about 1 % w/w to about 5% w/w of one or more superabsorbent polymers; about 0.5% w/w to about 5% w/w of one or more nanoparticles; about 5% w/w to about 15% w/w of one or more water soluble oils; and balance water.

[0019] In another aspect, the present application relates to methods of making the cutting fluid and/or coolant composition comprising the steps:

a) combining the one or more nanoparticles and the one or more oils to provide a first suspension;

b) adding water to the first suspension to provide a second suspension; c) mixing the second suspension at ultrasonic bathto provide a nanofluid; and

d) mixing the nanofluid with the one or more superabsorbent polymers under conditions to form a gel.

[0020] In another aspect, the present application relates to uses of the cutting fluid and/or coolant composition as a cutting fluid for cutting, machining, drilling, milling, turning and/or forming.

[0021 ] In another aspect, the present application relates to methods of cutting, machining, drilling, milling, turning, and/or forming a substrate comprising applying the cutting fluid and/or coolant to the substrate and cutting, machining, drilling, milling, turning and/or forming the substrate.

[0022] The present application relates to a gel-based cutting fluid and coolant composition, which can be used in various manufacturing processes. The SAC is composed of a superabsorbent polymer (SAP), and is fabricated by creating a suspension of graphite, copper and/or Magnesium Oxide nanoparticles that are suspended in a liquid. In some embodiments, the liquid is 90% water: 10% oil mixture and the SAP selected is a cross-linked sodium polyacrylate polymer. Superabsorbent polymers are powder-like solid materials that can absorb up to several hundred times their own weigh in liquid and are used in a wide range of applications including drug delivery, filters, and separation processes. In some embodiments, the superabsorbent polymer developed with lubricating graphite, copper and/or magnesium oxide nanoparticles, greatly improves the milling and turning processes in terms of tool wear, surface roughness, cutting forces and chip morphology. The Superabsorbent Coolant (SAC) is an eco-friendly metalworking fluid, where minimum amounts of emulsions and nanoparticles are used, which reduced the amount of waste and limits the post-processing expenses. Moreover, the key characteristics of the SAC fluid can be manipulated though varying the preparation process. Table 1 outlines the challenges associated with previous cooling techniques and illustrates how this new composition and method, disclosed herein, addresses the issues. In some embodiments, when the SAC is applied a significant improvement in the tool life is observed compared to manufacturing under dry condition and flood cooling system with commercial coolant.

[0023] Other features and advantages of the present application will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples while indicating preferred embodiments of the application are given by way of illustration only, since various changes and modifications within the spirit and scope of the application will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Embodiments of the present application will now be described in relation to the drawings in which:

[0025] Figure 1 Panel A shows an exemplary composition of SAC and Panel B shows an exemplary SAC preparation sequence.

[0026] Figure 2 shows examples of different nanoparticles used in the composition.

[0027] Figure 3 shows a scanning-electron microscopy (SEM) cross-sectional view of exemplary SAC particles containing graphite nanoparticles under different magnifications. Panel A shows [700x MAGNIFICATION]. Panel B shows [6.00kx MAGNIFICATION]. Panel C shows [900x MAGNIFICATION].

[0028] Figure 4 shows a scanning-electron microscopy (SEM) cross-sectional view of the SAC particles containing exemplary copper nanoparticles under different magnification. Panel A shows [900x MAGNIFICATION]. Panel B shows [6.00kx MAGNIFICATION]. Panel C shows [2.02kx MAGNIFICATION]. [0029] Figure 5 shows a scanning-electron microscopy (SEM) cross-sectional view of exemplary SAC particles containing Magnesium Oxide nanoparticles under different magnification. Panel A shows [900x MAGNIFICATION]. Panel B shows [15kx MAGNIFICATION]. Panel C shows [6.00kx MAGNIFICATION].

[0030] Figure 6 shows an exemplary delivery system for the SAC composition for machining process.

[0031 ] Figure 7 shows the viscosity of different exemplary SAC containing different nanoparticles at different shear rate. Panel A shows viscosity of SAC without nanoparticles. Panel B shows viscosity of SAC with graphite nanoparticles. Panel C shows viscosity of SAC with copper nanoparticles. Panel D shows viscosity of SAC with Magnesium Oxide nanoparticles.

[0032] Figure 8 shows an exemplary machining step. Panel A shows a nozzle location for flood coolant. Panel B shoes a pre-rubbed superabsorbent coolant (SAC) on a surface.

[0033] Figure 9 shows an exemplary delivery system setup for the lathe machine. Panel A shows the machining setup on the lathe machine. Panel B shows the exemplary SAC delivery system installed outside of the machine. Panel C shows the delivery system attached to the machine with magnet and nozzle position.

[0034] Figure 10 shows flank wear and total material removal during the machining of Hardened H13 under different cooling environments, where square is data under dry conditions, circle is data underflood conditions, and triangle is data under exemplary SAC conditions.

[0035] Figure 1 1 shows optical microscope images of tool wear under different conditions. Panel A shows optical microscope image of tool wear under dry conditions. Panel B shows optical microscope image of tool wear under flood conditions. Panel C shows optical microscope image of tool wear under exemplary SAC conditions.

[0036] Figure 12 shows DSC test result of dry superabsorbent polymer.

[0037] Figure 13 shows results of cutting force in different times under dry (square), flood (circle), and exemplary SAC (triangle) conditions. [0038] Figure 14 shows results of cutting energy in different times for different conditions, where square is for dry conditions, circle is for flood conditions, and triangle is for exemplary SAC conditions.

[0039] Figure 15 shows fluctuation of surface roughness values vs machining time under dry (square), flood (circle), and exemplary SAC (triangle) conditions.

[0040] Figure 16 shows chips SEM images and scratch depth changes under different cooling conditions. Panel A shows image under dry conditions. Panel B shows image under flood conditions. Panel C show images under exemplary SAC conditions

[0041] Figure 17 shows chip 3D scanning under Alicona™ microscope for different conditions where panel A is the scanning of the chip under dry conditions, panel B is the scanning image of the chip under flood conditions, and panel C is the scanning image of the chip under exemplary SAC conditions.

[0042] Figure 18 shows growth of flank wear during the machining of Inconel 718 under flood and exemplary SAC with Cu (square) and MgO (triangle) nanoparticles and SAC without nanoparticles (diamond) conditions. Results under flood conditions are shown in circle.

[0043] Figure 19 shows Chip 3D scanning under Alicona™ microscope; (A) Flood, (B) SAC without nanoparticles (C) exemplary SAC with Cu nanoparticles and (D) exemplary SAC with MgO nanoparticles

DETAILED DESCRIPTION

I. Definitions

[0044] The term "superabsorbent coolant" or "SAC" as used herein refers to cutting and/or coolant compositions that are used in machining processes that comprise at least one superabsorbent polymer.

[0045] The term "superabsorbent polymer" or "SAP" as used herein refers to polymers that absorb up to several hundred times their own weigh in liquid.

[0046] The term "nanoparticle" as used herein refers to a particle between about 1 and about 100 nm in size and that is compatible with use as a coolant/cutting fluid in machining.

[0047] The term "nanoparticle" as used herein includes metals, metal oxides and materials with high micro plasticity, such as lubricious nanoparticles. [0048] The term "lubricious" as used herein refers to substantially soft materials having lubricious (i.e. smooth or slippery) qualities, which are capable of reducing the coefficient of friction between a tool and an article such as a workpiece.

[0049] In understanding the scope of the present application, the term "comprising" and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The foregoing also applies to words having similar meanings such as the terms, "including", "having" and their derivatives.

[0050] The term "consisting" and its derivatives, as used herein, are intended to be closed ended terms that specify the presence of stated features, elements, components, groups, integers, and/or steps, and also exclude the presence of other unstated features, elements, components, groups, integers and/or steps.

[0051 ] Further, terms of degree such as "substantially", "about" and "approximately" as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. These terms of degree should be construed as including a deviation of at least ±5% of the modified term if this deviation would not negate the meaning of the word it modifies.

[0052] As used in this specification and the appended claims, the singular forms "a", "an" and "the" include plural references unless the content clearly dictates otherwise. Thus, for example, a composition containing "a nanoparticle" includes a mixture of two or more nanoparticles. It should also be noted that the term "or" is generally employed in its sense including "and/or" unless the content clearly dictates otherwise.

[0053] The definitions and embodiments described in particular sections are intended to be applicable to other embodiments herein described for which they are suitable as would be understood by a person skilled in the art.

[0054] The recitation of numerical ranges by endpoints herein includes all numbers and fractions subsumed within that range (e.g. 1 to 5 includes 1 , 1 .5, 2, 2.5, 3, 3.5, 4, 4.5 and 5). It is also to be understood that all numbers and fractions thereof are presumed to be modified by the term "about."

[0055] Further, the definitions and embodiments described in particular sections are intended to be applicable to other embodiments herein described for which they are suitable as would be understood by a person skilled in the art. For example, in the following passages, different aspects of the application are defined in more detail. Each aspect so defined may be combined with any other aspect or aspects unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.

II. Compositions and Methods

[0056] The present application relates to cutting fluid and/or coolant compositions comprising one or more superabsorbent polymers, one or more nanoparticles, one or more water-soluble oils and water. The present application also relates to methods of making the cutting fluid and/or coolant compositions. Further, the present application relates to the use of the cutting fluid and/or coolant compositions for manufacturing processes such as cutting, machining, drilling, milling, turning, and forming.

[0057] In one aspect, the present application relate to cutting fluid and/or coolant compositions of comprising:

about 1 % w/w to about 5% w/w of one or more superabsorbent polymers; about 0.5% w/w to about 5% w/w of one or more nanoparticles; about 5% w/w to about 15% w/w of one or more water soluble oils; and balance water.

[0058] In another aspect, the present application relate to methods of making the cutting fluid and/or coolant composition comprising the steps:

a) combining the one or more nanoparticles and the one or more oils to provide a first suspension;

b) adding water to the first suspension to provide a second suspension; c) mixing the second suspension at ultrasonic speed to provide a nanofluid; and

d) mixing the nanofluid with the one or more superabsorbent polymers under conditions to form a gel.

[0059] In an embodiment, the one or more superabsorbent polymers in the cutting fluid and/or coolant composition are hydrogels. [0060] In an embodiment, the one or more superabsorbent polymers in the cutting fluid and/or coolant composition are selected from natural and synthetic hydrogels.

[0061 ] In an embodiment, the one or more superabsorbent polymers in the cutting fluid and/or coolant composition are selected from cross-linked sodium polyacrylate polymers and polyacrylamide polymers.

[0062] In an embodiment, the one or more nanoparticles in the cutting fluid and/or coolant composition are lubricious nanoparticles. In an embodiment, the lubricious nanoparticles are nanoparticles of tungsten, lead, bismuth, indium or tin, or alloys thereof. In some embodiments, the one or more nanoparticles are carbonaceous or metallic.

[0063] In an embodiment, the one or more nanoparticles in the cutting fluid and/or coolant composition are selected from tungsten nanoparticles, boron nanoparticles, molybdenum nanoparticles, copper nanoparticles, calcium nanoparticles and graphite nanoparticles. In an embodiment, the one or more nanoparticles are selected from tungsten disulphide nanoparticles, boron nitride nanoparticles, molybdenum disulfide nanoparticles, calcium fluoride, molybdenum oxide nanoparticles and graphite nanoparticles.

[0064] In an embodiment, the one or more nanoparticles in the cutting fluid and/or coolant composition are selected from graphite nanoparticles, copper nanoparticles, and magnesium oxide nanoparticles, or mixtures thereof. In an embodiment, the one or more nanoparticles in the cutting fluid and/or coolant composition are graphite nanoparticles.

[0065] In an embodiment, the one or more oils of the cutting fluid and/or coolant composition are selected from semi-synthetic oils, synthetic oils, vegetable oils, soluble oils and mineral oils. In an embodiment, the one or more oils of the cutting fluid and/or coolant composition are selected from semi-synthetic oils.

[0066] In an embodiment, the cutting fluid/coolant composition comprises about 1 % w/w to about 5% w/w, about 1 .5% w/w to about 3% w/w, about 1 .75% w/w to about 2.5% w/w, or about 2 % w/w of one or more superabsorbent polymers.

[0067] In an embodiment, the cutting fluid/coolant composition comprises about 0.5% w/w to about 5% w/w, about 0.75% w/w to about 3% w/w, about 1 % w/w to about 2% w/w, or about 1 .5% w/w of one or more nanoparticles. [0068] In an embodiment, the cutting fluid/coolant composition comprises about 5% w/w to about 15% w/w, about 7% w/w to about 13% w/w, about 8.5% w/w to about 1 1 .5% w/w, about 9% w/w to about 1 1 % w/w, or about 10% w/w of one or more water soluble oils.

[0069] In an embodiment, the cutting fluid/coolant composition comprises about 2% w/w of one or more superabsorbent polymers, about 1 % w/w to 1 .5% w/w of one or more nanoparticles, and about 10% w/w of one or more water soluble oils.

[0070] In another embodiment, the present application relates to a cutting fluid and/or coolant composition comprising a cross-linked sodium polyacrylate polymer, graphite nanoparticles, and a semi-synthetic oil.

[0071 ] In another embodiment, the present application relates to a cutting fluid and/or coolant composition comprising a cross-linked sodium polyacrylate polymer, copper nanoparticles, and a semi-synthetic oil.

[0072] In another embodiment, the present application relates to a cutting fluid and/or coolant composition comprising a cross-linked sodium polyacrylate polymer, Magnesium Oxide nanoparticles, and a semi-synthetic oil.

[0073] In another embodiment, the present application relates to a cutting fluid and/or coolant composition comprising about 2% w/w of cross-linked sodium polyacrylate polymer, about 1 % w/w to 1 .5% w/w of graphite nanoparticle, about 10% of semi-synthetic oil, and balance water.

[0074] In another aspect, the present application relates to uses of the cutting fluid and/or coolant composition as a cutting fluid for cutting, machining, drilling, milling, turning and/or forming.

[0075] In another aspect, the present application relates to methods of cutting, machining, drilling, milling, turning, and/or forming a substrate comprising applying the cutting fluid and/or coolant to the substrate and cutting, machining, drilling, milling, turning, and/or formingthe substrate.

[0076] The above application generally describes the present application. A more complete understanding can be obtained by reference to the following specific examples. These examples are described solely for the purpose of illustration and are not intended to limit the scope of the application. Changes in form and substitution of equivalents are contemplated as circumstances might suggest or render expedient. Although specific terms have been employed herein, such terms are intended in a descriptive sense and not for purposes of limitation.

[0077] The following non-limiting examples are illustrative of the present application. As is apparent to those skilled in the art, many of the details of the examples may be changed while still practicing the methods and preparing the compositions described herein.

III. Examples

Example 1 Composition Preparation and Characterisation

[0078] Based on the manufacturer's suggestion, semi-synthetic soluble oil in the ratio of 1 :10 was added to water and used as a flood coolant. The concentration of the cutting fluid checked before and after the tests were 9.5 and 10%, respectively. The reason for this small change is because of water evaporation during the machining tests because of heat and high surface area. This concentration was applied for both milling H13 and turning Inconel 718. A change in concentration of this level is not expected to affect the final results.

[0079] To prepare the SAC, nanoparticles, such as graphite nanoparticles, were added to soluble oil and mixed with a magnetic stirrer for 20 min. Then water was added to the first suspension, and the resulting second suspension was immersed in an ultrasonic bath for two hours to disperse the nanoparticles uniformly in the fluid to form a nanofluid. Finally, the superabsorbent polymer was added to the nanofluid and allowed to gel for about 10 minutes. One issue with utilizing nanofluids in the industry and especially as cutting fluid is the sedimentation of nanoparticles over time and the liberating of nanoparticles into the environment, which changes the thermal conductivity and lubricity of the fluid and can lead to environmental hazards depending on the nature of the nanoparticles. However, when superabsorbent polymer is added, the nanoparticles penetrate the porous network of the polymer and remain stable indefinitely and are not free to leave the cutting surfaces. Figure 1 Panel A illustrates SAC ingredients for preparing one kilogram of coolant in one embodiment of the application. Figure 1 Panel B summarizes the sequence for SAC preparation in one embodiment of the application. Figure 2 provides information about characteristics of the nanoparticles that were used in this study. [0080] The same procedure was done when copper (Cu) nanoparticles or Magnesium Oxide (MgO) nanoparticles were added instead of graphite for cutting Inconel 718. The only difference is that percentage of graphite nanoparticles was 1 % w/w, and Cu nanoparticles and MgO nanoparticles 1 .5 % w/w. The reason was adding more graphite leads to sedimentation of extra particles so it seems 1 % w/w was suitable in this case. The absorbency ratio in this case was about 50 for coolants with graphite nanoparticles and copper nanoparticles additives and a little less than that for coolant with Magnesium Oxide nanoparticles content (approximately 40).

[0081 ] After the preparation of SAC, one of the polymer particles was dissected and imaged in the scanning electron microscope (SEM) to determine whether the nanoparticles are embedded in the polymer network or only adhered to the surface. For the best stability, it is optimal to have nanoparticles embedded deep inside the porous structure of the superabsorbent particle. Figures 3 to 5 show cross-sectional view of a superabsorbent particle in the SEM and confirms the presence of nanoparticles throughout the polymer structure.

Example 2 Delivery System

[0082] For dry milling, compressed air with a pressure about 4.5 bars was used for chip evacuation to prevent the re-cutting of the chips. The nozzle position for the flood coolant was chosen according to previous work on milling of steel ST60: nozzle feed position, elevation angle, and distance of nozzle tip from tool were set at 120°, 60° and 30mm respectively. Moreover, the pressure of coolant was set 1 .8 Mpa and flow rate of 9.7 L/min. Due to the viscosity of the SAC, it was not possible to pump it efficiently using a typical flood cooling system. Thus to deliver the SAC gel to the cutting region, a 200ml_ syringe was used. Approximately 45 mL/min of SAC was used for each pass.

[0083] Because SAC was applied to the surface before machining, there is no flow rate or coolant pressure. The adhesive nature of the gel caused some of the chips to stick to the gel, leading to re-cutting of the chips. To solve this problem, a compressed air nozzle with 3 bars pressure was positioned to remove the chips from the cutting zone.

[0084] For turning, compressed air was removed because there was no longer any dry cutting. Then flood coolant with 86 lit/min flow rate and 200 psi pressure was delivered during machining Inconel 718. The condition for applying SAC was developed and a new inexpensive delivery system for continuous and uniform pressure and flow rate was designed and built (Figure 6). The mechanism of working new system is easy and applicable for most of the machine tools. In this case an ABS pipe with internal diameter of 76 mm and length of 50 cm was chosen and one end connected to the air pressure regulator and the other end connected to a valve to control flow rate. Then valve with a plastic hose and couple of fittings connected to a flow distributor and ultimately, with regular nozzle SAC could deliver near the cutting point. SAC is embibed into the pipe and when air pressure is applied from the top, it pushes SAC downward and forces it to move into the pipe and hose. The normal pressure that is required for this process is about 20 psi. This device could be attached and removed to every machine by two magnets.

[0085] Table 2 and Figure 7 show coolant characteristics including viscosity and thermal conductivity. The ThermTest™ TPS 2500 S Thermal Constants Analyzer with 20 second test time was used to measure thermal conductivity of the coolants. SAC with nanoparticles shows different values depending on shear rate due to non-Newtonian behaviour.

Table 2 - Coolant Characteristics

Example 3 Machining Condition for H13 [0086] Machining was performed under dry, flood and Superabsorbent Coolant (SAC) conditions so that the results could be compared. Machining conditions and parameters are listed in Table 3.

Table 3 - Machining conditions for milling H13

Milling tests were done on hardened H13 steel. Table 4 shows characteristics and composition of the workpiece.

Table 4 - H13 Workpiece characteristics and composition

[0087] The cutting tool applied was an uncoated carbide end mill manufactured by OSG (code - 414-3937). Figure 8 shows the experimental setup on a Makino™ MC56 CNC milling machine.

Example 4 Machining Conditions for Inconel 718

[0088] Machining was carried out on Nakamura™ CNC lathe under followed conditions:

• Flood: semi-synthetic soluble oil in the ratio of 1 : 10 mixed with water

• SAC without nano-additive: semi-synthetic soluble oil in the ratio of 1 : 10 mixed with water and superabsorbent powder added at the end to form SAC

• SAC with Cu nano-additive and SAC with MgO nano-additive: Composition is as mentioned in Figure 1 .

[0089] Widia™ CNGG uncoated carbide inserts (code: 120408FS) were used to cut Inconel 718. Table 5 includes cutting parameters and Table 6 illustrates lnconel718 material characteristics.

Table 5 - Machining conditions for Inconel 178

Table 6 - lnconel718 workpiece characteristics and composition

[0090] Nozzle position for flood condition was set based on the previous research by author [1 1 ]. For providing continuous flow of SAC in this test nozzle it was set on the edge of rake face and flank face around 10 mm away from tool tip and aiming both rake face to facilitate chip flow and flank face to reduce flank wear. Figure 9 shows the machining setup and nozzle position for this set of tests.

Example 5 Measurement

[0091 ] As outlined in Tables 3 and 6, cutting force, tool wear, surface roughness and chip morphology were measured and evaluated during machining. Cutting Force was measured with a Kistler™ 9255b piezoelectric dynamometer on milling machine. Tool flank wear at each stage was assessed using a Mitutoyo™ TM optical microscope and a Keyence™ microscope model VHX-5000. A machining cycle was defined on the CNC machine to stop cutting after 2.5 minutes. Each time the machine stopped, tool wear and surface roughness were measured. Surface roughness was measured during at each stage of the tool wear growth, and an average of four measurements has been taken using a Mitutoyo™ SJ-201 at three different points. For each point, the scattering length is 1 .7 mm. Differential Scanning Calorimetry (DSC) was used to determine the energy per gram of SAC required to change phase in each stage.

[0092] For turning operation same microscopes and surface roughness tester were used. But this time after a certain length of cut, 20 mm, tool wear recorded and roughness measured at the end of the process. Finally, chips collected from both process at beginning of the cutting before any effect of tool wear or formation of tribo-layers and Alicona™ 3D microscope was used to measure chip undersurface roughness.

Example 6 Results of Milling Hardened H13

[0093] The machining performance of SAC coolant is outlined regarding cutting forces, surface roughness, tool wear and chip morphology. Cutting force represents the amount of energy that a machine tool needs to remove the material and it is one of the factors that affect the economics of machining and quality of the final part. Results indicate that different cooling conditions lead to different machining outcomes. The effects of dry, flood and SAC conditions on cutting forces, surface roughness, tool wear and chip morphology will be discussed separately in this paper. Under tool wear, the Marangoni effect that influences the drawing of the fluid to the hot surface of the tool will be addressed, and it will be demonstrated that SAC overcomes this adverse effect. DSC test results will also be analyzed to evaluate the heat absorbency of the SAC during its phase change.

[0094] Tool Wear:

[0095] Tool wear is one of the determining factors impacting the economics and efficiency of manufacturing processes. Rapid tool wear due to reduced cutting parameter selection or unsuitable tool material selection will increase processing cost. Tool wear was observed and recorded using an optical microscope after each 2.5 min of cutting. Figure 10 exhibits flank wear and total material removal under different cooling environments.

[0096] During the cutting process, a significant amount of heat is generated due to friction into the cutting zone. This can result in substantial heating at the contact region between interface workpiece - cutting tool - chip, especially, machining hardened steels such as H13 which is considered difficult to machine due to its high hardness and low thermal conductivity. Additionally, the low thermal conductivity of H13 tends to increase the cutting temperature, which further promotes tool wear and tool failure, such as chipping and fracture. Furthermore, in a milling operation, the intermittent process can produce oscillated temperatures, in combined with loading and unloading forces; it leads to cracking and fracturing of cutting edges mainly when flood coolant is applied. Therefore, the early tool failure in flood machining is a combined effect of thermal fatigue wear. [0097] In another way, on dry cutting, the high temperatures generated cutting zone decrease the shear strength of the material. Thus, the material becomes easier to cut, and the cutting tool experiences less resistance. But, in wet cooling, fluid cools down the work material, and the process uses higher force. Furthermore, milling is an interrupted cutting operation in which each cutting flute cuts the workpiece for a short period and then rests briefly. This short rest allows the fluid to penetrate to the tool tip and cool the cutting edges. When this occurs, the tool experiences a high-temperature gradient that can cause premature failure due to thermal shock for brittle tools such as uncoated carbide. In the case of SAC, due to the gradual release of the emulsion from the hydrogel and generation of less heat in the secondary shear deformation zone owing to the rolling action of the nanoparticles (which decrease the friction and heat), the tool experiences a smaller temperature gradient. Moreover, graphite nanoparticles have relatively high thermal conductivity and thus conduct some heat away, further reducing the severity of the temperature gradient due to their dwell time on the surface of the tool.

[0098] There is another phenomenon behind the success of the SAC technique. A fundamental principle known as the Marangoni effect restricts the penetration of cutting fluid into the contact zone. The Marangoni effect occurs where the surface tension of a fluid changes according to temperature. At higher temperatures, less surface tension is observed, and the liquid has a tendency to move toward a point with a lower temperature. In machining, the Marangoni effect causes coolant to move away from the cutting zone due to its high temperature. This effect is minimized with SAC because the oil is in the water emulsion and the nanoparticles are trapped inside the porous structure of the superabsorbent, and there is no coolant flow toward the contact zone. Equations 1 and 2 demonstrate why SAC is more efficient than conventional coolant:

(1 )

(2)

where Ma is Marangoni number, r is drop radius, vO is velocity, k is thermal conductivity, σ is surface tension between the drop and the workpiece, T is temperature, and μ is dynamic viscosity. The dynamic viscosity of SAC, due to its gel form, is much higher than that of commercial coolants. Accordingly, vO tends to zero and the Marangoni number tends to zero as well. Therefore, Marangoni effect is minimal or negligible for SAC, allowing better penetration of SAC into the hottest area directly reducing its temperature and, subsequently, tool wear. Figure 1 1 shows the optical images of the worn tool at 200μιη flank wear.

[0099] With respect to SAC's high viscosity and ability to move and penetrate into the cutting zone, an attractive feature of hydrogels is that they exhibit non-Newtonian behavior in viscosity experiments: viscosity is not a constant value and changes according to the shear rate (Figure 7). As shear rate increases, the complex viscosity decreases. During the cutting operation, when SAC comes into initial contact with the tool, its viscosity is high, and it does not splash away. Due to elevated temperature and high shear rate related to the high relative speed between the chip and tool, the viscosity decreases rapidly, and two phenomena may occur: If the temperature is high enough, burning or evaporation of the superabsorbent particles can happen, and graphite nanoparticles can be left on the tool to perform lubrication. At lower temperatures, SAC changes phase from a gel to a liquid and propels the nanoparticles into the secondary shear deformation zone. Thus, nanoparticles and emulsion are present at the tool-chip interface and act as a coolant and lubricant. The second phenomenon was mainly observed in this study, as the amount of SAC was sufficient to prevent much evaporation or burning. Only a small amount of smoke was found during machining. It is worth mentioning that when SAC changes phase to liquid, capillary flow takes the place of the Marangoni effect to fill in micro cracks and fissures in the chips and tool-chip interface. Thus, the Marangoni effect seems to be the functional determinant during the initial contact between the coolant and the hot tool, but the capillary flow is efficient in the contact area due to the existence of cracks and fissures.

[00100] There is another advantage to the SAC technique. With the wet cooling method, the fluid that comes into early contact with the hot tool surface evaporates and creates a pocket of vapor around the hot point of the tool and prevents subsequent efficient heat transfer. This challenge is addressed by atomizing the coolant in MQL because it eliminates the vapor pocket, and small droplets use latent heat, which is higher than heat transfer in the same phase, to conduct heat away. This phenomenon also occurs in SAC because the superabsorbent gradually releases coolant and the amount of coolant that is utilized in SAC is much lower than a flood method. This means that the emulsion within the polymer network of the superabsorbent draw on latent heat to evaporate. Moreover, the phase changes of the polymer from a gel to a liquid and then from a liquid to gas are endothermic. Figure 12 shows the result of the Differential Scanning Calorimetry (DSC) test on the dry superabsorbent polymer. DSC is a solid laboratory method to determine the thermodynamic behavior of a material. The graph indicates that each gram of superabsorbent absorbs approximately 1 .5 W of heat to change its phase from solid particles to gas (at 94.55 °C it turns the phase to liquid, and at 214.88 °C it evaporates).

[00101 ] Cutting forces and energy:

[00102] The cutting force in Figure 13 indicates that the use of SAC results in lower cutting forces over time as compared to dry and flood methods. Supplementary, coefficient of friction was calculated at the beginning, which represents the state of two new contact surfaces (chip and cutting tool).

[00103] In machining, tool-workpiece and tool-chip friction are very high and lead to high cutting forces. The tool-chip contact area is divided into two sections: the sticking zone and the sliding zone. Penetration of the coolant into the sticking zone is almost impossible due to the high normal stresses. The small size (APS: 400nm and thickness: 40nm) and superior lubricity of the nanoparticles allows them to penetrate the sliding zone and change the sliding friction into the combination of rolling and sliding friction decreasing the resistant force and, consequently, generated heat.

[00104] Cutting forces for dry conditions are initially lower than for flood conditions because the heat produced softens the material locally and the tool can remove the material with less force. In the case of flood cooling, the water-based coolant cools the surface and dissipates heat, so the material retains its hardness and the tool experiences higher resistance from the workpiece material as it deforms. However, in the case of SAC, the work material is cooled, but the friction is lowered by the presence of the lubricious nanoparticles. As the tool wear increases with time for flood conditions, the contact area between tool and workpiece increases, excluding the liquid cutting fluid from a larger area, and cutting forces become the same as experienced under dry conditions. Cutting forces experienced while applying SAC increase gradually to nearly double the initial value by the end of the experiment, which is expected due to the increase in contact area arising from the larger flank wear region and increased tool engagement with workpiece material. [00105] To show that friction conditions were improved during machining with SAC, required energy to remove the material was also calculated (Figure 14). During the cutting, extreme frictional conditions and high temperature lead to several damages at the cutting tool, which increases cutting force and energy for material removal. However, during the cutting process with SAC as a result of less friction provided by the coolant the energy for material removal is lower than the others conditions (Dry and Flood).

[00106] Surface roughness:

[00107] Average Surface roughness (Ra) of the workpiece was measured after each machining cycle (2.5 min) from three different points. The results reveal that for all three conditions surface roughness fluctuates over time (Figure 15).

[00108] Dry cutting has the most fluctuation followed by flood and SAC. One explanation for the better performance of the SAC is due to the presence of nanoparticles. For example, the inclusion of graphite nanoparticles in the contact zone reduces the friction efficiently and prevents metal-to-metal contact, resulting in decreased scarring of the machined surface and a smoother surface. Furthermore, less tool wear and better cooling action, which was discussed in the tool wear section, lead to the better surface finish and less oxidation. A logical explanation for the fluctuations in the graph is vibration. Vibration in interrupted machining like side milling is exacerbated when working with hardened H13 steel, which is unable to absorb vibrations to the extent that softer materials are, and it increases the impact of the tool on the workpiece, so higher surface roughness is observed under dry conditions. This situation is supported by the fact that preheating the workpiece to 650°C reduced the amount of vibration during end milling of Ti-6AI-4V. SAC and flood coolant, by lubricating the tool-workpiece contact area, allow the tool to slide on the surface reducing the effect of vibration on the surface. It should be noted that each time during machining that the operator unclamps the tool to measure tool wear and then replaces it, the tool position may be changed. This would change the eccentricity and, consequently, vibration, leading to variations in surface roughness values.

[00109] Chip undersurface:

[001 10] Studying chip shape and formation can give useful information about machining performance and the effectiveness of each cooling method. Chips collected during machining were inspected under an SEM. Direction and depth of the parallel lines on the chip surface are good indications of friction between the tool and chip. Shallower lines in SAC indicate that the force between tool - chip was lower than other conditions that prevent metal-to-metal contact and decreased friction. As is seen in Figure 16, dry machining creates deeper lines meaning that there was no lubricant to reduce the friction. Lines become shallower in flood cooling due to the lubrication agent, and chip surface is almost smooth under SAC cooling technique because of acting graphite nanoparticles with superior lubricity in addition to the oil in water emulsion.

[001 1 1 ] To verify these results and measure the depth of the scratches, an Alicona™ microscope (high-resolution optical 3D microscope) was used to scan the chips and measure the surface roughness. The result of undersurface roughness can be seen in Figure 17.

Example 7 Results of Turning lncone!718

[001 12] Performance of turning Inconel 718 under four different coolant conditions is explained. Copper and Magnesium Oxide nanoparticles added to the SAC and results compared with two benchmarks, flood and SAC without any nanoparticles. Machine tool was equipped with a new design of delivery system for these tests so that SAC was supplied continuously to the tool-chip interface. Tool wear, chip undersurface roughness and surface roughness of the final workpiece were evaluated as main criteria for performance comparison.

[001 13] Tool wear:

[001 14] Inconel 718 alloy is known as one of the most challenging materials to cut. This Nickel-based alloy is extensively used in aerospace, nuclear and defense industry. Low thermal conductivity (compared to steel alloys), maintaining strength at high temperature, hard abrasive particles inside the material matrix and sticking to tool tip during machining and creating build up edge make Inconel a difficult-to-cut material because in such a condition more energy and force is used to remove the excess material and temperature increases at cutting area. This can result in poor surface quality and fast tool wear during machining Inconel.

[001 15] As it shown in Figure 18 application of Cu and MgO nanoparticles in SAC could improve tool life significantly. Uncoated carbide tool under flood condition reaches maximum flank wear just after 440 m machining whereas SAC without nanoparticles extends tool life to 570 m, however, tool failure is observed before touching maximum flank wear (300μιη). By keeping same machining condition for all of the coolants, adding nanoparticles to the SAC improved the performance of the coolant and extended the tool life by almost twice as compared to SAC without nanoparticles.

[001 16] There are different theories about function of nanoparticles during cutting operation. According to [17], different mechanisms are possible when nanoparticles act between two surfaces; rolling effect, protective film, mending and polishing effects.

[001 17] In this case, tool is constantly in contact with workpiece material and gel is supplied near the cutting region. High temperature and shear rate of cutting area reduce the viscosity and release the nanofluid inside the gel locally. Actually, superabsorbent gel works as a carrier to deliver nanoparticles to the tool tip in low flow rate and prevent spreading nanoparticles into the air. As shown in Figure 7, SAC with Copper is more viscose at higher shear rates than SAC with Magnesium Oxide. Based on the Marangoni equation (Equation (1 )), higher viscosity leads to lower Marangoni number. It means more and better penetration to the tool-chip interface. Then nanoparticles can fulfill their lubrication action (it could be combination of mentioned mechanisms) and decrease tool- chip contact.

[001 18] Beside penetration of nanoparticles to the cutting zone, another reason that SAC performed better than flood coolant is the higher thermal conductivity of nanoparticles. Because of low thermal conductivity (1 1 .2 W/m. K), Inconel 718 keeps most of the generated heat in cutting area causing tool softening, BUE and finally tool failure. Flood coolant creates a pocket of vapor around cutting point and not capable to penetrate and remove heat [18]. So nanoparticles in this case, help to extract more heat from tool tip and tool faces less temperature gradient consequently, tool life would be higher.

[001 19] According to the Figure 18, SAC with Copper additives shows slightly higher tool life than SAC with Magnesium Oxide. The reason possibly could be morphology of particles. Based on the manufacturer's technical data sheet Copper nanoparticles have spherical shape but Magnesium Oxide has polyhedral shape. Therefore, logically for rolling action of the nanoparticles Copper works better than Magnesium Oxide.

[00120] Surface roughness:

[00121 ] Surface roughness (Ra) is another criterion to judge the effectiveness of a coolant during cutting. It impacts the fatigue strength, friction between surfaces and corrosion resistance. [00122] Workpiece roughness was measured after the last pass of machining with surface profile tester. According to Table 7, roughness values are almost same for all of the cases. It means all of the coolants showed same performance in terms of surface roughness, however, tool wear results were totally different. Nanoparticles in this case, could not bring about any specific improvement. One possible reason could be in turning operation the coolant applied in the tool-chip interface (SSDZ) not tertiary shear deformation zone (TSDZ) which is the contact point and friction between tool and workpiece. Therefore, nanoparticles are not able to reduce friction and generate better surface finish. In the worst case scenario SAC with nanoparticles works as well as flood condition in terms of surface quality.

surface roughness values of the Inconel 718 workpeace under different

[00123] Chip undersurface:

[00124] If there was a doubt that nanoparticles are working or not, chip undersurface roughness confirms the function of nanoparticles in SAC during cutting lnconel718. Chips were gathered after first pass of machining in each cooling condition. The idea of gathering chip in very beginning is observing the effect of coolant before forming any tribo- layer or tool wear. Then Alicona microscope was used to scan the chips and measure roughness. Results indicate that Ra values when Cu and MgO nanoparticles were utilized are less than SAC without nano-additive and flood coolant.

[00125] All of the lubrication mechanism of nanoparticles could play role in reducing chip roughness. As mentioned herein, lower values of chip roughness means that scratches are shallower and there is an agent reducing the contact area and severity of contact between tool and chip which is nanoparticle additives. Moreover, Figure 19 demonstrates that SAC despite of its high viscosity (at low temperature and shear rates) was able to penetrate effectively and reduce friction. [00126] Sustainability:

[00127] Beside all of the benefits that SAC could provide during cutting operation, environmental and occupational effects need to be considered. Disposal of metalworking fluids after machining is one of the concerns for government and extra expenses for industry. Some of the challenges of cutting fluids has mentioned below:

• Almost 17% of industrial cost of machining goes for metalworking fluids

• Chemical disintegration and phase separation occurs in cutting fluids due to bacterial growth and high temperature in cutting area · Operator diseases exacerbation such as respiratory problems and skin irritation

• Can cause soil and water pollution and high cost of post processing because of harsh environmental regulations

[00128] However, new techniques like MQL could improve both cutting performance and sustainability but it does not provide full operator protection since coolant is atomized into the air and it can get in to the respiratory system and cause serious problems.

[00129] Superabsorbent Coolant simultaneously could provide the benefits of MQL and solid lubricant and meanwhile reduce the environmental and human side- effects. Actually, this method introduces a safer condition to utilize nanoparticles by focus on "near cutting zone release" and prevent dust or mist formation during machining. Therefore, nanoparticles preserve inside the SAP and release takes place when temperature is high enough to loosen the internal bonding of SAP and lets the nanofluid comes out. Additionally, it can absorb dust or small chips that generate during specific operations. As an example machining cast iron due to brittle nature of the material produces very small chips and when coolant is used, chips can agglomerate and stick to the machine tool and needs cleaning after machining. This problem addressed by using SAC. In a sets of tests on cast iron in MMRI lab when SAC was applied, due to gel form and sticky nature of the gel, small chips automatically absorbed to superabsorbent particles and made cleaning easier for operator after machining. Other alloys like stainless steel, nickel based alloys and chrome reported to have the same problem and applying MWF during machining absorbs the microscopic dust and reduce the potential hazard of cutting these materials for operator. [00130] From post-processing point of view, disposing MWFs is costly and some techniques such as thermal evaporation, ultrafiltration, reverse osmosis (RO) and nanofiltration consume a lot of energy. SAC reduces the amount of coolant consumption remarkably. It means less volume of MWF needs to be treated after usage and it saves cost and energy, consequently, less soil and water would be polluted.

Conclusion

[00131 ] This application outlines a new lubricating technique and cooling material, which displays superior functions for semi-dry machining with superabsorbent particles. It was found that it is possible to apply SAC as a new coolant and lubricant in an industrial field. In order to demonstrate the performance of SAC, cutting force, surface roughness, tool wear and chip morphology measurements were conducted and results were compared with dry and flood conditions. The examples of the developed features are summarized and listed below:

• Higher thermal conductivity as compared to commercially available coolant due to the presence of graphite nanoparticles that help to extract more heat from the cutting zone. Furthermore, nanoparticles can withstand higher temperatures that are expected during machining difficult-to-cut materials and high speed machining. Graphite is also an excellent lubricant that acts in the sliding zone and decreases the friction by changing the sliding friction to rolling friction. · Better penetration of nanoscale particles into the tool-workpiece-chip contact area.

• The cooling emulsion and nanoparticles are released from the superabsorbent at high temperature, so the cutting zone can be specifically targeted. This phenomenon significantly decreases the amount of cutting fluid required, which will decrease the waste treatment and post-processing expenses. · SAC provides the benefits of both MQL and solid lubricant methods. Because the amount of cutting fluid is much lower than flood cooling, latent heat is used for evaporation. Additionally, nanoparticles are a solid lubricant and decrease the friction. Furthermore, the phase changes of polymer are endothermic and may be helpful in extracting more heat from the cutting zone. · Reduced thermal shock and temperature gradient on the tool: The tool is immersed in the hydrogel throughout the cutting process, so temperature changes are gradual. In addition, the Marangoni effect is minimized which allows the SAC to penetrate to the tool tip and reduce the temperature gradient. In comparison, in the flood method, the Marangoni effect prevents coolant from contacting the hottest area, and in cryogenic cooling, the tool suddenly encounters -196 °C temperature which can cause thermal shock and micro cracks.

• Due to high viscosity and semi-solid nature of SAC it is stable in the machining zone and does not splash away. Therefore, it is not messy like flood coolant and there is less operator contact with cutting fluid which decreases the likelihood of occupational disorders such as skin problems, eye irritation, and pulmonary diseases.

• While nanoparticles have excellent characteristics like high thermal conductivity and lubricity however they can be really dangerous for humans if they are absorbed into the body and thus can cause serious health problems for operators. This problem is addressed by utilizing the superabsorbent material as a carrier for the nanoparticles because the hydrogel traps the nanoparticles inside their porous structure and prevents the distribution of the nanoparticles into the air.

[00132] Based on machining outcomes and comparisons with dry and flood machining it was demonstrated that superabsorbent hydrogels as coolants can be adopted to increase the efficiency of machining by increasing tool life, yielding better surface finish and reducing cutting forces while exhibiting superior environmental and occupational characteristics.

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