Lubricating oil additives based on boron compounds are promising materials for lubrication due to their tribological advantages such as antiwear efficiency, good film strength, and high temperature resistance. This article deals with the preparation of zinc borate particles that are well dispersed and colloidally stabilized in mineral oil. This method starts with preparing two inverse emulsions (water-in-oil) with sorbitan monostearate (Span 60) as a surfactant, light neutral oil as a continuous phase, and the aqueous solutions of borax decahydrate (Na 2 B 4 O 7 Á10H 2 O) and zinc nitrate (Zn(NO 3 ) 2 Á6H 2 O) as the dispersed phases. The produced particles were zinc borate crystals having both rod-like and spherical morphologies, and the diameters of spherical particles were changing between 20 and 30 nm. FTIR spectra of the obtained particles showed the characteristic peaks of trihedral borate (B(3)-O) and tetrahedral borate (B(4)-O) groups as well as the specific peaks of the sorbitan monostearate. TG showed 30.42% and 22.08% mass loss at 600°C for the samples prepared by inverse emulsion and precipitation techniques, respectively. The endothermic peak at 50°C is observed due to the melting of sorbitan monostearate and the heat of melting is evaluated as -3.50 J/g. Tribological studies revealed that sorbitan monostearate not only outperformed as a dispersing agent of inorganic particles, but also it proved to be an anti-wear agent. Zinc borate produced by precipitation decreased the wear scar diameter from 1.402 to 0.639 mm and the friction coefficient from 0.099 to 0.064. The inverse emulsion was effective in decreasing wear scar diameter and the friction coefficient by lowering them to 0.596 and 0.089 mm, respectively.

The effect of emulsion process formulation ingredients on the morphology, structure, and properties of polyvinyl chloride (PVC) powder has been considered in this study. PVC powder was extracted with ethanol and films were obtained by solvent casting from tetrahydrofurane. Characterization of powders, films, and ethanol extract was performed through FTIR spectroscopy, DSC, AFM, SEM, EDX analysis, methylene blue, and nitrogen adsorption. PVC powder was composed of spheres of a large particle size range from 10 nm to 20 lm as shown by SEM. The specific surface area of the PVC powder was determined as 16 and 12 m 2 g -1 from methylene blue adsorption at 25°C and from N 2 adsorption at -196°C, respectively. AFM indicated the surface roughness of the films obtained by pressing the particles was 25.9 nm. Density of PVC powder was determined by helium pycnometry as 1.39 g cm -3 . FTIR spectroscopy indicated that it contained carbonyl and carboxylate groups belonging to additives such as surface active agents, plasticizers, and antioxidants used in production of PVC. These additives were 1.6% in mass of PVC as determined by ethanol extraction. EDX analysis showed PVC particles surfaces were coated with carbon-rich materials. The coatings had plasticizer effect since, glass transition temperature was lower than 25°C for PVC powder and it was 80°C for ethanol extracted powders as found by using differential scanning calorimetry. These additives from polymerization process made PVC powder more thermally stable as understood from Metrom PVC thermomat tests as well.

Experimental design was used to optimize the processing parameters for the decomposition of poly (vinyl chloride). Factorial design and face centered composite design (FCC) were applied to determine the optimum conditions. A total of 10 g PVC powder was mixed with different amounts of zinc stearate (ZnSt 2 ) and natural zeolite and tested for thermal stability. Factorial fitted model was explained by first order pattern due to the significant main effect regression constants, and FCC model was described by second order model owing to higher order polynomial coefficients. FCC design was superior to factorial design as FCC considers not only its pure quadratic effects contribution but also its higher overall desirability for thermal stability of PVC. For factorial design the optimum conditions were determined as 163.06 mg for ZnSt 2 , 399.99 mg for zeolite, and 140 C for temperature with desirability of 0.933. However, 400 mg for ZnSt 2 , 333.24 mg for zeolite, and 140 C for temperature with desirability of 0.956 were obtained as the optimum conditions by FCC design.

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The formation of the first membrane, the swelling of the crystal by incoming water from the semipermeable membrane and the formation of irregular shaped branches were observed by optical microscopy, when zinc sulfate heptahydrate crystals were immersed in saturated borax solution. The powders obtained by mixing dilute aqueous borax and zinc sulfate solutions had B, O, Na, S and Zn elements. Presence of Na Zn 1/2 B 4 O 7 .xH 2 O was indicated by EDX analysis. The molar ratio of B 2 O 3 /ZnO in powders was around 2. FTIR analysis indicated the ratio of absorbance values of asymmetric stretching vibrations of B (3) -O at 1351 cm -1 to that of B (4) -O at 1026 cm -1 increased with their heating time at 90ºC during their preparation. X-ray diffraction patterns indicated the presence of Zn(OH) 2 and Zn 4 (OH) 6 (SO 4 )•4H 2 O. The zinc borate compounds in the powders were not crystalline since no sharp peaks related to zinc borates were present in x-ray diffraction diagram. There were two mass loss steps in TG curves of the powders. The first step at 150-350ºC and the second step at 700-950ºC were due to elimination of water and due to decomposition of sulfate ions respectively. The submicron powders were a mixture of zinc borate, Zn(OH) 2 , Zn 4 (OH) 6 (SO 4 )•4H 2 O and Na Zn 1/2 B 4 O 7 .xH 2 O and they could be used as lubricant additive due to their small particle size of 600 nm.

Lubricants consist of base oils and chemical additives such as dispersants, surfactants, oxidation inhibitors, and antiwear agents. Organic and inorganic boron-based additives increase wear resistance and decreases friction. Hexagonal boron nitride and metal borates are used for this purpose. Zinc borate is a synthetic hydrated metal borate. The production techniques of zinc borate generally include the reaction between zinc source materials (zinc oxide, zinc salts, zinc hydroxide) and the boron source materials (boric acid and borax). The nano zinc borate particles were prepared from zinc nitrate and borax in the present study by using low initial zinc and borate concentrations and low temperature to prevent particle growth. The templates span 60 and PEG 4000 were used to control the particle size. The particles were separated from mother liquor by centrifugation, washed with ethanol, dried and ground and used as additive to base oil. The particles have H2O and B(3)-O vibrations in their FTIR spectra. The empirical formula of the nanoparticles was approximately 3ZnO.2B2O3.4H2O from EDX and TGA analysis. X-ray diffraction diagram indicated the particles were in amorphous state. When the nanoparticles were added to light neutral oil the wear scar diameter and friction coefficient was lowered 50% and 20% respectively.

Abstract:The present study attempts the preparation of copper borate as a lubricating oil additive by the reaction of copper nitrate and borax solutions. Effects of borax/ copper ratio, surface active agent (Span 60), pH, temperature and mixing time on properties of the products were investigated. The obtained products were not pure form; therefore they were analyzed in detail. They were characterized by color measurement, X-ray diffraction, SEM, zeta sizer, ICP, EDX, TG, DSC, CHNS analysis and FTIR spectroscopy.