Synthesis of the Multifunctional Additive N-acyl Glutamic Acid and Application in Water-Based Lubricating Fluids

A series of N-acyl glutamic acid were prepared by reaction of glutamic acid with chlorides (1–3) or anhydrides (4–8) in good yield, within the solution of pH 8–10, keeping the reaction at 10∼15°C for 2–3 hours. The tribological behaviors of the resulting N-acyl glutamic acid salts with triethanolamine as additives in water were examined on a four-ball machine. The rust-inhibiting properties were evaluated. The elemental composition of the boundary lubricating film was analyzed by means of auger electron spectroscopy (AES). It was found that the N-acyl glutamic acid with long acyl chain functioned to considerably increase anti-wear and friction-reducing abilities of water. The rust-inhibiting properties got better with increase of the length of acyl-chain of N-acyl glutamic acid triethanolamine slats. And the additives had relative good antimicrobial properties in water.