Smithers Blog // Assessing DPG Use and Alternative Materials for Rubber Manufacturing

Sustainability and environmental stewardship continue to drive innovation in polymer and industrial chemical development for a wide variety of end-use applications. Whether the goal is improving material performance to support evolving application requirements, or simply to find more sustainable or environmentally ‘kind’ materials, material scientists are now challenged to review the full product life cycle before making final product decisions. In this blog, Smithers explores the regulatory status, environmental impact, and future considerations surrounding N,N’-Diphenylguanidine (DPG), a key accelerator in rubber manufacturing.

Background to DPG

 N,N’-Diphenylguanidine (DPG) is a secondary vulcanisation accelerator for natural and synthetic rubbers, typically used in conjunction with other accelerator types. It comprises around 0.1 to 0.2% concentration predominantly in passenger tire tread rubber compounds, but is also used in the manufacture of general and technical rubber goods.

DPG and its associated reaction by-products, for example, aniline, are not currently subject to the same level of public exposure and concern around human and environmental risks as PFAS and 6PPD. However, the landscape is fluid. Future research, awareness and understanding of any risks posed could prompt further reviews and evaluations.

Legislative Landscape for DPG

European Chemicals Agency (ECHA)

According to the harmonised classification and labelling (CLP Regulation for classification, labelling and packaging of products) approved by the European Union, DPG is deemed toxic to aquatic life with long lasting effects, is harmful if swallowed, causes serious eye irritation, is suspected of damaging fertility, causes skin irritation and may cause respiratory irritation. The Harmonised Classification is generally a minimum classification and may not cover all hazards.

French Agency for Food, Environmental and Occupational Health & Safety (ANSES)

However, the French Agency for Food, Environmental and Occupational Health & Safety (ANSES) is seeking to strengthen the classification of diphenyl guanidine used to manufacture rubber products. Following its assessment, ANSES is proposing that its European classification be strengthened in order to better protect human health from neurological disorders as well as damage to fertility and development in particular.

ANSES determined that the level of evidence concerning the substance’s reprotoxic nature justified an increase in its classification, following an updated assessment of the substance’s various effects in light of the latest available data. The Agency is therefore proposing changes to the classifications for human health, particularly regarding acute effects on the skin and eyes, as well as on reproduction and development. However, with regard to its environmental effects, ANSES is proposing a less stringent classification. Based on the most recent and reliable biodegradation study, DPG is considered to be rapidly biodegradable, with a low bioaccumulation potential. Studies have shown chronic toxicity for aquatic organisms, with algae being the most sensitive species assessed.

Government of Canada

The Government of Canada has conducted a science-based evaluation of DPG, called a screening assessment. Screening assessments address potential for harm to the general population (not including workplace exposures) and the environment.

Based on the conclusion of the final screening assessment, DPG is not expected to accumulate in or cause harm to organisms, and the quantities of DPG that may be released to the environment are below the levels expected to cause harm to organisms. Therefore, the Government of Canada has concluded that DPG is not entering the environment in a quantity or under conditions that constitute a danger to the environment. The Government of Canada has also concluded that DPG is not harmful to the health of the general population at current levels of exposure.

Future Direction and Risk Mitigation

This snapshot indicates that DPG and its associated reaction by- products do not currently face the same level of scrutiny or recognised risk as PFAS and 6PPD. However, evolving research, increased awareness, and a deeper understanding of potential environmental impacts could prompt regulatory bodies to re-evaluate DPG in the future. While alternatives to DPG do exist, they are not always direct substitutes and will typically require validation and optimisation based on the specific application.

How Smithers can help – evaluating DPG alternatives

 As global material regulations rapidly evolve and sustainability reporting requirements become more robust, manufacturers require end-to-end solutions for the development process.

Working with an expert testing and technology provider who understands both sides of the DPG issue, is critical to support development with material property and environmental impact concerns.

Smithers is in a unique position amongst independent, third-party testing and consulting organisations as we provide holistic support for raw material and product manufacturers in the rubber and polymer industry.

Our global team of testing experts can design and conduct integrated studies and custom testing protocols to get you the answers you need as you strive to find solutions.

Smithers’ services range from material chemistry and whole product testing to environmental fate and toxicology studies:

• Understanding material requirements and developing testing plans to support development activities
• Material chemical characterisation benchmarking and analysis Small batch compound mixing to evaluate options.
• Physical property testing and evaluation of compounds
• End-product evaluation of real-world or test-bench performance.
• Analytical Chemistry:

– Qualitative and quantitative compositions of antidegradant materials
– Qualitative and quantitative compositions of rubber specimens, including samples excised from tires

• Standard and custom environmental studies: environmental fate, environmental metabolism, and ecotoxicology studies to investigate the overall effects of tire particulates on the environment and specific flora and fauna populations

How Smithers can help

Smithers is equipped to help you solve your rubber challenges, giving you confidence in your materials and helping you develop optimised products. Smithers provides consultancy and technical training tailored to your individual and corporate needs, enabling you to answer the questions you face in relation to the rubber and plastics materials you use. We also have in-house polymer testing labs, giving data and insights into your products, including rubber hardness assessments, electrical property testing and much more.

Read more news from Smithers here.

Smithers
01372 802 000
Website