Lubricant and method of preparing the same

Dispersion stability test of copper nanoparticles in lubricants

The copper nanoparticles were modified by dioctyl dithiophosphate which accounted for 60 wt. % of the modified copper nanoparticles. The copper nanoparticles had an average particle size of 4 nm and the C 8 -alkyl chain modifier was distributed outside the copper nanoparticles. The copper nanoparticles were mixed with different dispersants in different additive amounts for the study of dispersion stability in lubricants.

The mixtures of the copper nanoparticles and different dispersants in different additive amounts were respectively dissolved in a base oil comprising 70 wt. % of a synthetic oil and 30 wt. % of a trimethylolpropane ester, and the synthetic oil was polyalphaolefin 6 (PAO6). 24 hours later, the mixtures were centrifuged at 30° C. under 8000 rpm for 20 min. 10 mL of supernates were collected, and the transmittance thereof were measured using an UV spectrophotometer.

The copper nanoparticles contained a C 8 -alkyl chain modifier so that they had excellent dispersion stability. However, the addition of the dispersant changed the dispersion stability of the copper nanoparticles, and the dispersant competed with the modifier to adsorb on the copper core. Once the protection of modifier disappeared, the copper nanoparticles tended to oxidize, and the color changed from brown red to grey green, deteriorating the lubricity. On the other hand, the addition of the dispersants changed the agglomeration of the copper nanoparticles, thus adversely affecting its dispersion stability in the base oil. The test results are shown in Table 1 and Table 2.

The results showed that, the polyamide dispersants (T151, T152, T153, T161, produced by Xinxiang Ruifeng New Materials Co., Ltd.) competed with the modifier of the copper nanoparticles to adsorb on the copper nanoparticles, so that the copper nanoparticles were oxidized and deteriorated. However, the pentaerythritol ester dispersants (T171, produced by Lanzhou Lubo Runlan Refining Additives Co., Ltd.) can efficiently disperse the copper nanoparticles. Too many of the dispersants caused the agglomerates of the copper nanoparticles to deposit, so that the additive amount were about 2-4 weight parts.

The copper tends to oxidize the lubricant. Thus, the copper nanoparticles need to cooperate with different antioxidants to improve the antioxidant ability of the lubricant. Different antioxidants were mixed with a base oil comprising 70 wt. % of a synthetic oil and 30 wt. % of a trimethylolpropane ester, and the synthetic oil was polyalphaolefin 6 (PAO6). The antioxidant properties of the base oil were listed in Table 3.

The results show that, the copper nanoparticles can improve the antioxidant ability of the base oil. When mixing with the antioxidant T512, the antioxidant ability of the lubricant has been improved to the greatest extent.

The copper nanoparticles as soft metals have excellent antifriction and repair functions, but under high load and extreme pressure conditions, the copper nanoparticles cooperate with an anti-wear agent to form a synergistic effect to achieve extreme pressure lubrication effect. The anti-wear agent is a mostly organic polar compound containing sulfur, phosphorus and chlorine. The extreme pressure anti-wear ability of the lubricant is evaluated by measuring its P B (maximum nonseizure load) and P D (minimum sintering load).

The results show that, the copper nanoparticles greatly improve the extreme pressure anti-wear ability of the base oil. When mixing with the anti-wear agent T304 (dibutyl phosphite), the copper nanoparticles can improve the P B and P D of the lubricant to the greatest extent.

A lubricant comprises: 80 parts of a base oil; 2 parts of a methyl-silicone oil; 1 part of polymethacrylate; 4 parts of pentaerythritol polyisobutylene succinate; 2 parts of di-n-butyl phosphite; 3 parts of butylhydroxytoluene; 4 parts of an ethylene-propylene copolymer; 1 part of alkenyl succinate; and 3 parts of copper nanoparticles. The base oil comprises 70 wt. % of a synthetic oil and 30 wt. % of a trimethylolpropane ester, and the synthetic oil is a polyalphaolefin 6 (PAO6).

A method of preparing the lubricant comprises:

adding the base oil, the methyl-silicone oil, the polymethacrylate, the ethylene-propylene copolymer, the butylhydroxytoluene, the alkenyl succinate to a reactor, and stirring a resulting first mixture under normal temperature and pressure (NTP) at 300 rpm for 4 hours, to yield a primary product; and adding the di-n-butyl phosphite, the pentaerythritol polyisobutylene succinate, and the copper nanoparticles to the primary product, and stirring a resulting second mixture at 150 rpm for 2.5 hours.

A lubricant comprises: 82 parts of a base oil; 2 parts of a methyl-silicone oil; 1 part of polymethacrylate; 2 parts of pentaerythritol polyisobutylene succinate; 1 part of di-n-butyl phosphite; 3 parts of butylhydroxytoluene; 3 parts of an ethylene-propylene copolymer; 2 parts of alkenyl succinate; and 4 parts of copper nanoparticles. The base oil comprises 70 wt. % of a synthetic oil and 30 wt. % of a trimethylolpropane ester, and the synthetic oil is a polyalphaolefin 8 (PAO8).

A method of preparing the lubricant comprises:

adding the base oil, the methyl-silicone oil, the polymethacrylate, the ethylene-propylene copolymer, the butylhydroxytoluene, the alkenyl succinate to a reactor, and stirring a resulting first mixture under normal temperature and pressure (NTP) at 400 rpm for 3 hours, to yield a primary product; and adding the di-n-butyl phosphite, the pentaerythritol polyisobutylene succinate, and the copper nanoparticles to the primary product, and stirring a resulting second mixture at 250 rpm for 2 hours.

A lubricant comprises: 85 parts of a base oil; 1 part of a methyl-silicone oil; 1 part of polymethacrylate; 2 parts of pentaerythritol polyisobutylene succinate; 1 part of di-n-butyl phosphite; 2 parts of butylhydroxytoluene; 2 parts of an ethylene-propylene copolymer; 1 part of alkenyl succinate; and 5 parts of copper nanoparticles. The base oil comprises 70 wt. % of a synthetic oil and 30 wt. % of a trimethylolpropane ester, and the synthetic oil is a polyalphaolefin 10 (PAO10).

A method of preparing the lubricant comprises:

adding the base oil, the methyl-silicone oil, the polymethacrylate, the ethylene-propylene copolymer, the butylhydroxytoluene, the alkenyl succinate to a reactor, and stirring a resulting first mixture under normal temperature and pressure (NTP) at 350 rpm for 4 hours, to yield a primary product; and adding the di-n-butyl phosphite, the pentaerythritol polyisobutylene succinate, and the copper nanoparticles to the primary product, and stirring a resulting second mixture at 200 rpm for 2.5 hours.

The properties of the lubricants prepared in above examples are tested and the test results are shown in FIGS. 1A-1B . The friction pairs employed in the tests comprise one of four types of carbon films (that is, pure carbon film, Si-doped carbon film, Al-doped carbon film, H-doped carbon film) and stainless-steel balls. Friction conditions: the stainless-steel balls have a diameter of 4 mm, a single stroke of 5 mm, a linear velocity of 10 mm/s and a vertical load of 8 N. The experiments are carried out at room temperature. As shown in FIGS. 1A and 1B , compared with the SL grade engine oil on the market, the lubricant as described in the disclosure can reduce the friction coefficient and wear rate of the four types of carbon films by 9-19% and 93-99%, respectively. It can be concluded that the lubricant of the disclosure can effectively protect the carbon film and exhibit efficient lubricating properties.

It will be obvious to those skilled in the art that changes and modifications may be made, and therefore, the aim in the appended claims is to cover all such changes and modifications.