Loss of Elasticity in Jack Shock-Absorbing Rubber Blocks: Causes and Countermeasures
Jack shock-absorbing rubber blocks are designed to cushion impact loads, reduce vibration, and maintain stable contact between the jack and the supported structure. Loss of elasticity is a common failure mode during long-term service and can seriously affect lifting safety and performance. Understanding the causes and implementing effective countermeasures are essential for reliable operation.
1. Material Aging and Degradation
Rubber materials gradually lose elasticity due to physical and chemical aging processes. Oxidative aging leads to molecular chain scission or excessive crosslinking, resulting in hardening and reduced resilience. Ozone exposure accelerates surface microcracking, while thermal aging at elevated temperatures increases stiffness and brittleness. Over time, these effects significantly reduce the rubber’s ability to recover after compression.
2. Long-Term Static Compression
Jack rubber blocks are often subjected to prolonged static loads. Continuous compression causes permanent deformation, known as compression set, which prevents the material from returning to its original thickness. As compression set increases, elastic recovery and shock-absorbing capability decrease, leading to apparent elasticity loss.
3. Overloading and Impact Stress
Operating the jack beyond its rated capacity or exposing the rubber block to frequent impact loads accelerates internal fatigue damage. Repeated high stress can destroy the rubber’s internal network structure, resulting in reduced elasticity and increased stiffness.
4. Environmental Influences
Exposure to oils, fuels, chemicals, moisture, and ultraviolet radiation can degrade rubber materials if they are not properly formulated for such conditions. Oil swelling or chemical attack may alter the rubber’s mechanical properties, while UV radiation and ozone further accelerate hardening and loss of elasticity.
5. Manufacturing and Material Selection Factors
Improper rubber formulation, insufficient antioxidants or anti-aging agents, and inadequate vulcanization control can lead to poor long-term elastic performance. Additionally, selecting an unsuitable rubber type for the operating environment, such as using natural rubber in oily or high-temperature conditions, greatly increases the risk of elasticity loss.
6. Preventive Measures and Improvement Strategies
To reduce elasticity loss, appropriate rubber materials should be selected based on service conditions, such as NBR for oil resistance, EPDM for outdoor and ozone exposure, and polyurethane for high-load applications. Rubber formulations should include sufficient anti-aging additives, and vulcanization processes must be strictly controlled. In use, overloading should be avoided, static compression duration minimized, and regular inspections carried out to replace rubber blocks showing signs of hardening or permanent deformation.
Conclusion
Loss of elasticity in jack shock-absorbing rubber blocks is mainly caused by material aging, long-term compression, overloading, environmental exposure, and improper material selection. Through rational material choice, optimized design and manufacturing, controlled operating conditions, and effective maintenance, the elastic performance and service life of jack rubber blocks can be significantly improved.
References
Gent, A. N. Engineering with Rubber: How to Design Rubber Components. Hanser Publishers, 2012.
Lake, G. J. “Fatigue and Fracture of Elastomers.” Rubber Chemistry and Technology, 2000.
ASTM D395 – Standard Test Methods for Rubber Property—Compression Set.
ISO 1431-1 – Rubber, Vulcanized or Thermoplastic — Resistance to Ozone Cracking.
