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.

No abstract

The current study shows that screening was successfully implemented in a Canadian hospital, with high specificity (99.4%) and good compliance (88%). Reasons for non-acceptance of screening by midwives need to be addressed.

Hybrid swell packers are rubber products capable of swelling in (saline) water and hydrocarbon oils, by exploiting the hydrocarbon diffusion properties of an nonpolar elastomer with the osmotic swelling of a water absorbent (WA). In this study, a variety of modified natural and synthetic WAs and mixtures thereof have been screened in a rubber compound with respect to swelling in decalin, demineralized, and saline water, respectively. We aimed at achieving high and fast swelling in all used media. Mixing of the various WAs in an ethylene/propylene/diene monomer (EPDM)/carbon black masterbatch at an addition level of 75 phr did not pose any problems, although it was found that the WAs did affect the sulfur vulcanization. Decalin swelling of the vulcanizates is very fast, reaching high equilibrium swelling within 1.5 days. Swelling in demineralized or saline water is much slower, with up to 300% swelling in water and up to 100% swelling in saline water. Significant leaching of the organic WA from the EPDM vulcanizates to the water phase occurs. Some combinations of WAs show synergetic effects for swelling in water. To our knowledge, such a systematic study of hybrid swelling elastomers constitutes a novelty in the open literature.

No abstract