Will EVA foam degrade significantly in extreme temperatures?
Publish Time: 2025-08-27
EVA foam, due to its lightweight, soft, cushioning, and waterproof and moisture-resistant properties, may be exposed to a wide range of temperatures in actual use, from sub-zero temperatures in winter to scorching temperatures in summer.1. Performance in Low-Temperature Environments: Risk of Hardening and BrittlenessUnder low temperatures, the molecular chain mobility of EVA foam weakens, and the material gradually loses its elasticity, exhibiting a "hardening" phenomenon. When the ambient temperature drops to -20°C or even lower, EVA foam's resilience and flexibility significantly decrease, making it feel stiff and its impact resistance weakened. If subjected to severe impact or bending in this state, microcracks or even brittle fracture may occur. However, EVA foam's low-temperature tolerance is closely related to its vinyl acetate (VA) content. The higher the VA content, the better the material's softness and low-temperature toughness. Therefore, EVA foam used in cold regions or winter outdoor products typically uses a high VA content formula to improve its low-temperature aging resistance. Once the temperature rises, the material's properties are generally restored, representing a reversible change that does not constitute permanent degradation.2. Aging Mechanisms in High-Temperature Environments: Softening, Oxidation, and DegradationCompared to low temperatures, high temperatures have a more significant and irreversible effect on the aging of EVA foam. When ambient temperatures consistently exceed 60°C, EVA foam begins to soften, its resilience decreases, and it is prone to permanent compression set (i.e., collapse) after prolonged compression. If temperatures rise further above 80°C, especially in direct sunlight, the material will experience even more severe thermal-oxidative aging. Ultraviolet (UV) radiation is a significant factor accelerating EVA aging. Under the combined effects of high temperature and strong UV radiation, EVA molecular chains break, and vinyl acetate groups may decompose, resulting in cracking, chalking, and discoloration (such as yellowing) on the material surface. This type of aging is chemical degradation, and once initiated, it is irreversible. Furthermore, prolonged exposure to high temperatures can cause changes in the cross-linking structure of EVA foam, affecting its elasticity and service life. For example, the collapse or hardening of athletic shoe midsoles after prolonged exposure to the sun in the summer is a result of high-temperature aging.3. Synergistic Effects of Environmental Factors: Humidity, Ozone, and PollutantsExtreme temperatures often work in conjunction with other environmental factors to exacerbate EVA foam aging. For example, in high-temperature and high-humidity environments, while moisture is unlikely to penetrate the closed-cell structure of EVA, it can accelerate hydrolysis or mildew of the surface material. In polluted urban areas or industrial areas, ozone and acidic substances in the air can also erode the EVA surface, causing microcracks to develop. Furthermore, prolonged exposure to oil, sweat, or detergents can cause swelling or chemical reactions, further weakening EVA foam's stability in extreme temperatures.EVA foam can indeed experience significant aging in extreme temperature environments, particularly under high temperatures and strong UV radiation, resulting in softening, discoloration, cracking, and performance degradation. In low-temperature environments, while it may temporarily harden, its recovery is relatively good. Therefore, when designing and using EVA foam products, the application environment should be carefully considered, and appropriate material formulations and protective measures should be selected to avoid long-term exposure to extreme temperature swings and direct sunlight to extend product life and ensure functionality and safety.
