Cold Flow - What is cold flow?
Another term for creep, cold flow is a type of material deformation that is defined as the tendency of a solid material to slowly move or deform under the influence of mechanical stress. Cold flow is a time-dependent deformation and accumulates as a result of long-term exposure to stress; the rate of cold flow is determined by the material’s properties, exposure time, exposure temperature, and the degree of stress that is applied to the material. Temperature is a particularly influential factor as virtually all materials will demonstrate cold flow when approaching their melting point. This means that cold flow can occur at relatively low temperatures; for example, some plastics and metals (with low melting temperatures) will begin to flow at room temperature, while glacier flow is a result of creep in ice.
In labelling, cold flow can occur in any of the materials used to make labels, including adhesives, coatings, face materials, backing sheets, and printing inks. Cold flow is most commonly caused by label materials being exposed to too much heat and/or pressure at any point throughout the manufacturing and printing processes, during storage, or after a label has been applied to a substrate. It is particularly problematic when dealing with label adhesives, as cold flow will result in an adhesive moving outside of its own layer within a label construction, which can result in blocking (surface to surface sticking between sheets or rolls of labels), deformation or discolouration in adjacent layers, can damage printers, and can ultimately prevent a label from successfully adhering to a substrate. When cold flow occurs in an adhesive it is commonly referred to as adhesive bleed or adhesive ooze.Go Back to Glossary