Phenolic-formaldehyde resins have been in use for over a century. These materials are very hard organic polymers. They are used, e.g., in circuit boards, many types of electrical laminates, countertops, bearings, binders in friction surfaces (such as brake pads, brake shoes, and clutch disks), billiard and snooker balls, and other applications where hardness (such as in an outer shell) is a desirable attribute.
These polymers often contain residual formaldehyde, which may outgas during its service life and create exposure issues. For this reason, there is a strong push to find alternative materials. However, few other organic polymers may match the hardness of phenolic-formaldehyde type resins.
In some applications, phenolic-formaldehyde resins are subjected to conditions of high temperature, elevated pressures, and moisture. Examples of these applications include, e.g., composite materials used as conduits for high-temperature water and/or steam, certain undersea applications, and coatings for materials that are exposed during use to steam or high temperature water. Under those conditions, the resins exhibit a loss of properties, and may lose mass to the surrounding moisture. For example, when phenolic-formaldehyde resins are immersed in high temperature water, decomposition products are often seen leaching into the water, leading to the water turning milky white. For these applications, an alternative polymer that maintains its properties better is sought.