The aging of geosynthetic materials (geotextiles, geomembranes, composite geomembranes) refers to the process in which the material properties gradually deteriorate under environmental influences during processing, storage, and use. The manifestations of aging can be divided into four aspects:
1. Changes in appearance and tactile feel, such as stickiness, hardening, softening, brittleness, deformation, and discoloration.
2. Changes in physical and chemical properties, such as density, thermal conductivity, melting point, relative molecular mass, heat resistance, and cold resistance.
3. Changes in mechanical properties, such as tensile strength, elongation, elasticity, and wear resistance.
4. Electrical properties, such as changes in insulation resistance and dielectric constant.
In civil engineering, the primary concern is the changes in mechanical properties.
The intrinsic cause of the aging phenomenon is that polymer materials have a hydrocarbon structure, which can undergo degradation and cross-linking reactions under external influences. Degradation reactions involve the breakdown of polymer chains into smaller molecules, including chain scission and main chain decomposition. Cross-linking reactions occur when large molecules link together, forming network or three-dimensional structures, which lead to changes in material properties.