Full definition
Elongation at Break is a critical property of elastomers that measures the maximum percentage increase in gauge length a tensile specimen can endure before failure. This property is determined through standardized testing methods such as ASTM D412 and ISO 37, which typically involve the use of dumbbell or ring specimens subjected to a pull rate of 500 mm/min. The elongation at break is not merely a measure of stretch; it is a direct indicator of the material's flexibility, elasticity, and extensibility, which are essential for various applications in industrial settings. For instance, natural rubber (NR) exhibits the highest elongation at break, ranging from 600% to 900%, making it suitable for applications where high flexibility is crucial, such as in seals and flexible membranes. In contrast, materials like fluoroelastomer (FKM) show lower elongation, between 150% and 300%, which may limit their use in highly flexible applications but can still be suitable for environments requiring chemical resistance. Understanding elongation at break is vital for selecting the appropriate elastomer for specific applications, as it directly impacts performance under stress and environmental conditions.
The elongation at break can be influenced by several factors. Higher hardness, which often results from increased filler content, tends to reduce elongation, making the material less flexible. Additionally, higher cross-link density leads to a stiffer material, which in turn decreases elongation. Aging also plays a significant role; as elastomers undergo oxidation, their molecular chains can break down, resulting in reduced elongation properties. For instance, aging tests conducted per ASTM D573 measure elongation retention, where a retention rate of less than 50% indicates substantial material degradation. Thus, it is essential to consider both the initial elongation at break values and their retention over time when evaluating elastomer performance in real-world applications. Test conditions are standardized at a temperature of 23 ± 2°C to ensure consistency across evaluations, providing a reliable basis for comparison among different elastomer compounds.