Diphenylamine Antioxidants


Lubrizol provides lubricant additives that are designed to protect all types of engine oils, automatic transmission fluids, and other driveline products.  Lubrizol's unique understanding of chemistry, technology and the additives market, along with decades of experience enable Lubrizol to provide broad product offerings ranging from basic technology to novel, cutting-edge - performance chemistry. 


Diphenylamine (DPA) antioxidants control oxidation, keeping engines running longer and more smoothly by preventing oil thickening.  The antioxidant properties of these additives increase the life of engine oil by reducing breakdown that can result from the formation of sludge.  Their antioxidant properties also allow them to be used in other functional fluids.

Physical and Chemical Properties

DPA antioxidants are produced by reacting diphenylamine with an olefin containing the desired functional groups.  The reaction product then is typically purified by distillation.  They are solids or viscous liquids that have a low water solubility and a low vapor pressure.  Calculated octanol-water partition coefficients vary depending on the substance.

Health Effects

The health effects of DPA antioxidants have been assessed as part of the Petroleum Additives Substituted Diphenylamine category under the U.S. Environmental Protection Agency (EPA) voluntary High Production Volume (HPV) Challenge Program.  While some may cause skin irritation and weak to moderate eye irritation, they are not known to cause skin sensitization. The HPV assessment has shown that they have a slight to very low order of acute toxicity by oral and dermal routes of exposure in animals.  Inhalation toxicity is not expected to be a concern because of their low vapor pressure. Repeat dose studies have found that the extent and nature of systemic effects following repeat dose exposures vary depending on the DPA antioxidant.  They are of low concern for reproductive and developmental toxicity.  A combined repeat dose and reproduction/developmental screen of a DPA antioxidant that was deemed an appropriate, predictive analog of the other compounds in this category observed slight, non-significant effects on offspring only at maternally toxic doses.  No developmental toxicity was observed.  The weight of evidence indicates that they are not genotoxic, and, therefore, are not expected to be carcinogenic.  However, the presence of significant levels of unreacted DPA can affect the health hazards of the product.  DPA is acutely toxic by oral, dermal and inhalation routes of exposure.  Repeated exposure also poses danger of cumulative effects.

Environmental Effects

The environmental effects of DPA antioxidants also have been assessed as part of the Substituted Diphenylamine under the U.S. Environmental Protection Agency (EPA) voluntary High Production Volume (HPV) Challenge Program.  Because of their low vapor pressure, they are not expected to partition into air to any significant extent.  They are not readily biodegradable.  Their low water solubility indicates that water is not a target compartment, limiting the potential for bioaccumulation.  Results of ecotoxicity studies also indicate that they are of low concern for acute aquatic toxicity. However, the presence of significant levels of unreacted DPA can affect the ecotoxicity hazard of the product, making it toxic to aquatic organisms.

Regulatory Information

DPA antioxidants are subject to the European Commission REACH (Registration, Evaluation, Authorisation and Restriction of Chemical substances) regulation. The registration and Chemical Safety Reports for these substances were subject to 2010 reporting and have been submitted to the European Chemicals Agency (ECHA) by Lubrizol.  As noted in Lubrizol safety data sheets, DPA antioxidants have gained acceptance in major industrialized countries through global notifications.

Exposure Potential

DPA antioxidants are sold to industrial customers who formulate engine oils and other functional fluids.  Workers in these industrial exposure scenarios, professional workers and consumers can be exposed to these products via dermal contact.  The potential for inhalation exposure is limited by their low volatility.  However, some industrial operations that are conducted under elevated temperatures may increase the potential for inhalation exposure.  Because formulated products contain low levels of these antioxidants, the exposure potential for professional workers and consumers generally is much lower.  The extent of exposure varies depending on use conditions such as closed systems and the duration and frequency of use.  The potential for oral exposure is limited to cases of accidental ingestion. Indirect exposure via environmental media is expected to be negligible because of their low water solubility, low volatility and low levels in formulated products.

Risk Management

Information on the safe handling of these products is provided to workers who make the products and who formulate engine oils and other functional fluids through dissemination of material safety data sheets.  These documents provide a broad range of safety information including hazard warnings and risk management measures.  They note engineering controls, work practices, and personal protective equipment that are needed during the manufacture and formulation to control exposures. Good industrial hygiene practices also are used to avoid skin contact.  Environmental risk is mitigated by controlling spills and environmental releases. 


DPA antioxidants are designed to meet the special protection needs of all engines.  Their excellent physical and functional properties make them ideal for use in lubricants to increase the durability and performance of engines.  They have been well-studied.  Some may cause skin irritation and weak to moderate eye irritation.  The potential for systemic effects vary depending on the substance.  They have a low order of aquatic toxicity and a low potential to bioaccumulate.  However, the presence of significant levels of unreacted DPA can affect the hazards of the product making the product acutely toxic, a danger for cumulative effects and toxic to aquatic organisms.  The use of appropriate engineering controls, work practices, personal protective equipment and environmental release controls and practices provides effective risk management.