Silicone

A flexible material applied to joints and interfaces to exclude water, air or other media while accommodating movement between the parts, in contrast to an adhesive whose primary job is to transfer load. Silicone, polyurethane, polysulphide and silane-modified polymer chemistries dominate construction and industrial sealing.

A curing mechanism in which a one-part adhesive, sealant or coating reacts with atmospheric humidity, hardening from the exposed surface inwards. One-part polyurethanes, silicones and silane-modified polymers cure this way; cure through thick sections is slow and depends on humidity and temperature.

An adhesive and sealant chemistry based on polymer chains terminated with silane groups that crosslink with atmospheric moisture, combining the flexibility and weather resistance of silicones with the paintability and cleaner handling of polyurethanes, and containing no isocyanates. Widely used for elastic bonding and sealing in construction, marine deck fitting and vehicle assembly.

The gradual change in the appearance and properties of a material caused by outdoor exposure to ultraviolet radiation, moisture, temperature cycling and airborne pollutants. Coating and material durability is assessed by natural exposure trials and by accelerated weathering tests in the laboratory.