Influence of Multiwalled Carbon Nanotubes and Thermal Aging on the Swelling, Hardness, and Tear Properties of Pineapple‐Leaf‐Fiber‐Reinforced Natural Rubber Composites

The properties of elastomeric materials under thermal aging are crucial for determining the appropriate temperature range and service lifetime. In this study, the effects of thermal aging under various aging conditions on the swelling, hardness, and tear properties of pineapple leaf fiber (PALF)‐reinforced natural rubber (NR) composites with the inclusion of multiwalled carbon nanotubes (MWCNTs) were investigated. The PALF and MWCNT contents were fixed at 30 and 10 parts per 100 rubber, respectively. Thermal aging was conducted at different temperatures (60°C and 80°C) and for different exposure durations (2, 4, and 6 days). The morphologies of the tear‐fractured surfaces were investigated using scanning electron microscopy. Early in aging, the tear strength showed an initial increase followed by a downward trend. In contrast, the aged composites exhibited an increase in crosslink density and hardness with increasing aging duration and temperature. However, the swelling ratio decreased with increasing aging duration and temperature. For instance, when NR30P and NR30P/MWCNT composites were thermally aged at 80°C for 6 days, the swelling ratio decreased to 177.23% and 160.62%, respectively. The addition of MWCNTs remarkably improved the additional crosslinking degree during the aging process, which contributed to a noticeable reduction in crack size, as revealed by microscopic analysis. The findings provide valuable insights for improving the end‐use properties of NR composites.