Aliphatic polyamides, often referred to as "nylons," are commercially important materials that, for example, may be used to make fibers or molded articles. The properties of such polymers can be significantly affected by their end groups, one such property being dyeability. For example, after a nylon is formed into a fiber, it is often dyed. The end groups of the nylon can affect the amount of dye that is adsorbed by the fiber and the rate at which the adsorption occurs. For many dyes, the greater the amount of amine end groups in the nylon, the greater the amount of dye that will be adsorbed. In order to obtain fibers with consistent coloration, therefore, it may be desirable to modify and control the polymer end groups. The end groups on an aliphatic polyamide can also affect its other properties such as adhesion of the aliphatic polyamide to other materials.
British Patent 1,553,617 describes the use of polyureas for improving the properties of filled, particularly glass fiber filled, nylon molding resin compositions. Modification of the nylon end groups is not mentioned.