Compounding and Mixing Methodology for Good Performance of EPDM in Tire Sidewalls

Abstract

Ethylene propylene diene terpolymer (EPDM), which is a terpolymer of ethylene, propylene, and a diene, is characterized by having a fully saturated polymer backbone, resulting in excellent ozone and oxidative aging resistance. By contrast, diene elastomers such as natural rubber (NR) and polybutadiene rubber (BR) have high levels of unsaturation along their main polymer backbones, increasing their susceptibility to chemical degradation by main chain scission and therefore their need for a protection system. This is generally provided by adding combinations of primary antioxidants and migrating waxes. Protective systems based on paraphenylenediamines (PPDs) are very effective and are used extensively for the protection of tire sidewalls, but because they function by preferentially reacting with ozone, their activity becomes depleted over the service life of the tire. Other potential drawbacks are that PPDs form a reaction product that discolors the surface of the sidewall, and they are considered to be potentially hazardous to human health and the environment through contamination of water systems. By contrast, it has been shown that the addition of EPDM to a conventional sidewall compound can give a permanent high level of ozone protection that is nonhazardous and non-discoloring. However, differences in polarity, solubility, and levels of unsaturation create significant challenges for achieving successful blends of EPDM in typical NR/BR sidewall compounds, leading to inferior physical and dynamic properties. This study shows that by combining best practices for compound design and mixing methodology with optimum grades of EPDM, it has been possible to produce tire sidewall compounds having full ozone protection as well as physical and dynamic properties closely matching a typical sidewall compound. Additionally, this study shows that the presence of EPDM leads to improved properties after heat aging and vulcanized compounds having reduced energy dissipation behavior, which could lead to tires having reduced rolling resistance.

Occurrence of Substituted p-Phenylenediamine Antioxidants in Dusts

“…Most of these PPDs could be applied to the rubber products for the manufacturing of vehicle tires. For example, 6PPD is widely employed in commercial vehicle tire formulations (1–4% by mass). − Several other PPDs, such as CPPD, IPPD, and DNPD, also find applications in rubber for tire manufacturing . Tire wear particles, which are formed from tires undergoing friction on the road, could be the primary route for the release of these rubber additives into the environment .…”

Widespread Occurrence and Transport of p-Phenylenediamines and Their Quinones in Sediments across Urban Rivers, Estuaries, Coasts, and Deep-Sea Regions

“…The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.est.2c07652. Physicochemical properties as well as overall persistence and long-range transport potential (Pov, CTD, and TE) of seven PPDs and four PPD-Qs (Table S1); optimized ESI (+)-MS/MS parameters (Table S2); summarized QA/QC results (Table S3); detailed concentration data (Table S4); Spearman's correlation analysis (Table S5); MRM chromatograms and MS 2…”

“…p -Phenylenediamines (PPDs) are an important class of synthetic antioxidants that are used as additives in rubber-related products, mostly in rubber tires. , Among the globally used PPDs, N -(1,3-dimethylbutyl)- N ′-phenyl- p -phenylenediamine (6PPD) is the most frequently used tire antioxidant and has been listed as a high production volume (HPV) chemical by the Organization for Economic Co-operation and Development (OECD) . In China, the current annual production of 6PPD alone is 200,000 tons, accounting for approximately 54% of the total production of all current-use rubber antioxidants .…”

Beyond Substituted p-Phenylenediamine Antioxidants: Prevalence of Their Quinone Derivatives in PM2.5

“…Substituted para -phenylenediamines (PPDs), as a class of anthropogenic antioxidants, have been largely produced and applied in the rubber industry due to their capability for the protection of rubber materials against flex cracking, heat degradation, and ozone cracking. 1 However, massive production and consumption of these PPD antioxidants have caused increasing concern regarding their emissions and potential influence on the aquatic and terrestrial ecosystems. Emerged evidence indicated that these chemicals can be ubiquitously detected in receiving waters, 2 , 3 dusts, 4 , 5 sediments, 6 and air particles.…”

“…9,10 In addition, N-isopropyl-m′-phenyl-p-phenylenediamine (IPPD) was defined as predominantly occupational allergens, causing allergic contact dermatitis through direct contact with industrial rubber. 11 A test report from the U.S. EPA has illustrated the acute toxicity of N,N′-bis (1,4-dimethylpentyl)-p-phenylenediamine (77PD) to rats through inhalation with a LC 50 of 400 mg/m 3 . 12 In addition to PPDs, the environmental emissions and acute toxicity of their derived quinones (PPD-Qs) have attracted great attention lately.…”