Key Takeaways & Executive Findings
- •• • Optimal KB loading is 10 phr, yielding maximum tensile strength at room temperature and best tribological and barrier performance due to uniform filler dispersion, critical for components requiring wear resistance and low gas permeability. • • Tensile strength retention exceeds 80% for all compositions after aging in ozone, UV, and saline environments, indicating robust durability for outdoor or chemically aggressive service conditions. • • The 20% KB composite exhibits a 5 °C reduction in glass transition temperature (Tg), extending the operational temperature range for rubber-like elasticity, beneficial for applications in variable climates. • • Activation energy for thermal decomposition, determined via KAS modeling, is highest for the KB20 composite, signifying enhanced thermal stability and resistance to high-temperature degradation.
Abstract
Elastomers are widely used in engineering but suffer degradation when exposed to heat, ozone, UV radiation, and chemicals. To enhance performance for specific industrial applications, blending with other materials is common. In this study, chloroprene rubber (CR) was blended with brominated butyl rubber (BIIR) and reinforced with Ketjenblack (KB) at concentrations up to 20%. KB exhibits a porous, fluffy morphology with a high specific surface area of 1347 m²/g. Tensile tests were conducted before and after exposure to UV, ozone, saline, petrol, and diesel environments, and retention capacity was evaluated per ASTM standards. Transmission electron microscopy confirmed uniform dispersion of KB filler. Tribological and barrier property studies identified 10% KB as optimal due to uniform dispersion. Thermal degradation kinetics were analyzed using Kissinger–Akahira–Sunose modeling to determine activation energy. Dynamic mechanical analysis indicated a 5 °C reduction in glass transition temperature for the 20% composite. These elastomeric blends demonstrate potential as advanced materials for harsh industrial applications.
1. Introduction
Elastomeric components in demanding industrial sectors—automotive sealing systems, offshore hoses, and chemical processing equipment—face simultaneous attack from ozone, UV radiation, aggressive fluids, and mechanical wear. Conventional rubber compounds, such as neoprene or butyl rubber alone, offer only partial protection: neoprene provides oil and weather resistance but suffers from poor air impermeability, while butyl rubber excels in gas barrier properties but lacks mechanical strength and ozone resistance. Blending these elastomers is a logical strategy, yet simple blends often exhibit phase separation and compromised mechanical integrity, limiting their practical utility.
This study addresses that bottleneck by incorporating Ketjenblack (KB), a high-surface-area carbon black (1347 m²/g), into a chloroprene rubber/brominated butyl rubber (CR/BIIR) blend. The hypothesis is that KB's unique porous morphology and high structure will promote uniform dispersion, acting as a reinforcing filler that simultaneously enhances mechanical properties, barrier performance, and resistance to environmental aging. By systematically varying KB content up to 20%, the research identifies an optimal loading that balances tensile strength, tribological behavior, and thermal stability, providing a data-driven pathway to formulate elastomers capable of surviving extreme operational conditions.
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Rakesh Reghunath, Dileep P, Mehar Al Minnath, Unnikrishnan T G, Soney C George, Nandakumar Kalarikkal, Murali K P, Jinu Paul (2026). Ketjenblack-Reinforced Chloroprene Rubber / Brominated Butyl Rubber Blends: Enhanced Ozone and UV Stability, Air Permeability, and Tribological Performance. New Carbon Materials. https://doi.org/10.1016/S1872-5805(26)61073-6
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Frequently Asked Questions
What is the optimal Ketjenblack loading for achieving maximum tensile strength and tribological performance, and what are the underlying mechanisms?
The optimal loading is 10 phr (parts per hundred rubber). At this concentration, tensile strength at room temperature is maximum, and tribological and barrier properties are best. This is attributed to uniform dispersion of KB particles, as confirmed by TEM, which ensures effective stress transfer and reduces filler agglomeration that could act as stress concentrators or wear debris.
How does the addition of Ketjenblack affect the glass transition temperature and operational temperature range of the CR/BIIR blend?
Dynamic mechanical analysis (DMA) shows a 5 °C reduction in Tg for the 20% KB composite compared to the unfilled blend. This reduction extends the operational window where the material maintains rubber-like properties, making it suitable for lower-temperature applications without becoming brittle.
What is the thermal stability of the composites, and how is it quantified?
Thermal stability was assessed via Kissinger–Akahira–Sunose (KAS) modeling to determine activation energy for thermal degradation. The KB20 composite required the highest activation energy, indicating superior thermal stability. This suggests that higher KB loadings enhance resistance to thermal decomposition, which is critical for high-temperature applications.
How do the composites perform after exposure to aggressive environments such as ozone, UV, and saline?
All compositions retained more than 80% of their tensile strength after aging under ozone, UV, and saline treatments. This high retention capacity indicates excellent environmental resistance, making these materials suitable for outdoor or marine applications where such degradation factors are prevalent.
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