ABSTRACT
Developments in the field of engineering polymers include the introduction of high-performance polymers, such as polyethersulphone (PES), which is amorphous, and polyetheretherketone (PEEK), which is semi-crystalline; these polymers offer properties far superior to those of the normal thermoplastic polymers. In assessing the creep of a polymer material, it is particularly important to ensure that the service temperature does not approach the glass transition temperature of the polymer. Isostrain stress–log time and isochronous stress–strain curves in a three-dimensional creep graph are generally different from stress relaxation–log time and tensile testing stress–strain curves, respectively. Sealants are elastomeric materials, which can be used for sealing joints against wind and water in construction. The elastomer is another member of the polymer family. The material consists of long-chain molecules that are coiled and twisted in a random manner, and the molecular flexibility is such that the material is able to undergo very large deformations.
