Production of octyl levulinate biolubricant over modified H-ZSM-5:Optimization by response surface methodology

The present study highlighted the use of modified H-ZSM-5 （Meso-HZ-5） as heterogeneous catalyst for the synthesis of octyl levulinate biolubricant by catalytic esterification of biomass derived renewable levulinic acid （LA） with n-octanol. The process variables such as catalyst loading （X1）, n-octanol to LA molar ratio （X2） and reaction temperature （X3） were optimized through response surface methodology （RSM）, using Box-Behnken model. Analysis of variance was performed to determine the adequacy and significance of the quadratic model. The yield of octyl levulinate was obtained to be 99% at optimum process parameters. The developed quadratic model was found to be adequate and statistically accurate with correlation value （R2） of 0.9971 to predict the yield of octyl levulinate biolubricant. The study was also extended on the validation of theoretical and experimental data, including catalyst reusability.

Synthesis and Characterisation of a Biolubricant from Cameroon Palm Kernel Seed Oil Using a Locally Produced Base Catalyst from Plantain Peelings

Biolubricant was synthesized from Cameroon palm kernel oil (PKO) by double transesterification, producing methyl esters in the first stage which were then transesterified with trimethylolpropane (TMP) to give the PKO biolubricant in the presence of a base catalyst obtained from plantain peelings (municipal waste). The yields from both catalysts were significantly similar (48% for the locally produced and 51% for the conventional) showing that the locally produced catalyst could be valorized. The synthesized biolubricant was characterized by measuring its physical and chemical properties. The specific gravity of 1.2, ASTM color of 1.5, cloud point of 0°C, pour point of -9°C, viscosities at 40°C of 509.80 cSt and at 100°C of 30.80 cSt, viscosity index of 120, flash point greater than 210°C and a fire point greater than 220°C were obtained. This synthesized biolubricant was found to be comparable to commercial T-46 petroleum lubricant sample produced industrially from mineral sources. We have therefore used local materials to produce a biolubricant using a cheap base catalyst produced from municipal waste.

Comparative assessment of force,temperature,and wheel wear in sustainable grinding aerospace alloy using biolubricant

The substitution of biolubricant for mineral cutting fluids in aerospace material grinding is an inevitable development direction,under the requirements of the worldwide carbon emission strategy.However,serious tool wear and workpiece damage in difficult-to-machine material grinding challenges the availability of using biolubricants via minimum quantity lubrication.The primary cause for this condition is the unknown and complex influencing mechanisms of the biolubricant physicochemical properties on grindability.In this review,a comparative assessment of grindability is performed using titanium alloy,nickel-based alloy,and high-strength steel.Firstly,this work considers the physicochemical properties as the main factors,and the antifriction and heat dissipation behaviours of biolubricant in a high temperature and pressure interface are comprehensively analysed.Secondly,the comparative assessment of force,temperature,wheel wear and workpiece surface for titanium alloy,nickel-based alloy,and high-strength steel confirms that biolubricant is a potential replacement of traditional cutting fluids because of its improved lubrication and cooling performance.High-viscosity biolubricant and nano-enhancers with high thermal conductivity are recommended for titanium alloy to solve the burn puzzle of the workpiece.Biolubricant with high viscosity and high fatty acid saturation characteristics should be used to overcome the bottleneck of wheel wear and nickel-based alloy surface burn.The nano-enhancers with high hardness and spherical characteristics are better choices.Furthermore,a different option is available for high-strength steel grinding,which needs low-viscosity biolubricant to address the debris breaking difficulty and wheel clogging.Finally,the current challenges and potential methods are proposed to promote the application of biolubricant.

An overview of functional biolubricants

At present,more and more diseases are associated with the lubrication dysfunction,which requires a systematic study of the complex lubrication behavior of tissues and organs in human body.Natural biomacromolecular lubricants are essential for maintaining ultra-low coefficients of friction between sliding biological interfaces.However,when the surface lubrication performance of tissues or organs destroys heavily,it will bring friction/shear damage for sliding contact interfaces.Therefore,the application of exogenous biological lubricating materials to improve the lubrication situation of damaged tissue or organ interfaces has attracted extensive attention of researchers.In this review,based on a simple summary of lubrication mechanism at sliding biological interface,we systematically introduce the research progress of several kinds of representatively biolubrication materials,including eye drops,tissue anti-adhesion agents,joint lubricants,and medical device lubricants.Meanwhile,the lubrication mechanism and individual advantage and shortcoming for each of these synthetic exogenous lubricated materials are clarified.Correspondingly,the important lubrication application functionality of these biolubricant materials in typically medical surgery scenes,such as dry eye syndrome,tissue adhesion,arthritis,and interventional medical devices,is discussed.Finally,we look forward to the future development direction of artificial biolubricant materials.

Nano-enhanced biolubricant in sustainable manufacturing:From processability to mechanisms

To eliminate the negative effect of traditional metal-working fluids and achieve sustainable manufacturing,the usage of nano-enhanced biolubricant(NEBL)is widely researched in minimum quantify lubrication(MQL)machining.It's improved tool wear and surface integrity have been preliminarily verified by experimental studies.The previous review papers also concluded the major influencing factors of processability including nano-enhancer and lubricant types,NEBL concentration,micro droplet size,and so on.Nevertheless,the complex action of NEBL,from preparation,atomization,infiltration to heat transfer and anti-friction,is indistinct which limits preparation of process specifications and popularity in factories.Especially in the complex machining process,in-depth understanding is difficult and meaningful.To fll this gap,this paper concentrates on the comprehensive quantitative assessment of processability based on tribological,thermal,and machined surface quality aspects for NEBL application in turning,milling,and grinding.Then it attempts to answer mechanisms systematically considering multi-factor influence of molecular structure,physicochemical properties,concentration,and dispersion.Firstly,this paper reveals advanced lubrication and heat transfer mechanisms of NEBL by quantitative comparison with biolubricant-based MQL machining.Secondly,the distinctive filmformation,atomization,and infiltration mechanisms of NEBL,as distinguished from metal-working fluid,are clarified combining with its unique molecular structure and physical properties.Furtherly,the process optimization strategy is concluded based on the synergistic relationship analysis among process variables,physicochemical properties,machining mechanisms,and performance of NEBL.Finally,the future development directions are put forward aiming at current performance limitations of NEBL,which requires improvement on preparation and jet methods respects.This paper will help scientists deeply understand effective mechanism,formulate process specifications,and find future development trend of this technology.

Electrostatic atomization minimum quantity lubrication machining:from mechanism to application

Metal cutting fluids(MCFs)under flood conditions do not meet the urgent needs of reducing carbon emission.Biolubricant-based minimum quantity lubrication(MQL)is an effective alternative to flood lubrication.However,pneumatic atomization MQL has poor atomization properties,which is detrimental to occupational health.Therefore,electrostatic atomization MQL requires preliminary exploratory studies.However,systematic reviews are lacking in terms of capturing the current research status and development direction of this technology.This study aims to provide a comprehensive review and critical assessment of the existing understanding of electrostatic atomization MQL.This research can be used by scientists to gain insights into the action mechanism,theoretical basis,machining performance,and development direction of this technology.First,the critical equipment,eco-friendly atomization media(biolubricants),and empowering mechanisms of electrostatic atomization MQL are presented.Second,the advanced lubrication and heat transfer mechanisms of biolubricants are revealed by quantitatively comparing MQL with MCF-based wet machining.Third,the distinctive wetting and infiltration mechanisms of electrostatic atomization MQL,combined with its unique empowering mechanism and atomization method,are compared with those of pneumatic atomization MQL.Previous experiments have shown that electrostatic atomization MQL can reduce tool wear by 42.4%in metal cutting and improve the machined surface Ra by 47%compared with pneumatic atomization MQL.Finally,future development directions,including the improvement of the coordination parameters and equipment integration aspects,are proposed.

Dopamine-triggered one-step functionalization of hollow silica nanospheres for simultaneous lubrication and drug release

Osteoarthritis(OA)has been regarded as a lubrication deficiency related joint disease.Combination of both joint lubrication and drug intervention may provide a promising nonsurgical strategy for treatment of OA.Developing novel and simple approaches to fabricate superlubricating nanoparticles with drug release property is highly required.Herein,dopamine triggered one-step polymerization method was employed to fabricate polydopamine/poly(3-sulfopropyl methacrylate potassium salt)(PDA-PSPMA)conjugate coating on hollow silica(h-SiO_(2))nanosphere surfaces to engineer functional nanoparticles(h-SiO_(2)/PDA-PSPMA).The as-prepared h-SiO_(2)/PDA-PSPMA exhibits excellent aqueous lubrication performance on biomaterial substrates as well as natural bovine articular cartilage based on hydration effect of negatively charged PDA-PSPMA coating and"rolling"effect of h-SiO_(2)nanospheres.In vitro drug loading-release experiments demonstrate that PDA-PSPMA coating functionalized h-SiO_(2)nanospheres show high drug-loading and sustained-release capability of an anti-inflammatory drug,diclofenac sodium(DS).Such h-SiO_(2)/PDA-PSPMA nanospheres can be potentially used as a synergistic therapy agent for OA treatment combining by simultaneous joint lubrication anddrugrelease.

Nanoparticle-enhanced coolants in machining:mechanism,application,and prospects

Nanoparticle-enhanced coolants(NPECs)are increasingly used in minimum quantity lubrication(MQL)machining as a green lubricant to replace conventional cutting fluids to meet the urgent need for carbon emissions and achieve sustainable manufacturing.However,the thermophysical properties of NPEC during processing remain unclear,making it difficult to provide precise guidance and selection principles for industrial applications.Therefore,this paper reviews the action mechanism,processing properties,and future development directions of NPEC.First,the laws of influence of nano-enhanced phases and base fluids on the processing performance are revealed,and the dispersion stabilization mechanism of NPEC in the preparation process is elaborated.Then,the unique molecular structure and physical properties of NPECs are combined to elucidate their unique mechanisms of heat transfer,penetration,and antifriction effects.Furthermore,the effect of NPECs is investigated on the basis of their excellent lubricating and cooling properties by comprehensively and quantitatively evaluating the material removal characteristics during machining in turning,milling,and grinding applications.Results showed that turning of Ti‒6Al‒4V with multi-walled carbon nanotube NPECs with a volume fraction of 0.2%resulted in a 34%reduction in tool wear,an average decrease in cutting force of 28%,and a 7%decrease in surface roughness Ra,compared with the conventional flood process.Finally,research gaps and future directions for further applications of NPECs in the industry are presented.