Rubber toughening and damage competition theory. In material selection it is important to look at the interaction between the matrix and the secondary phase. For example, crosslinking within the rubber phase will promote high strength fibril formation that will toughen the rubber, preventing particle fracture. Carboxyl-terminated butadiene-acrylotnitrile (CTBN) is often used to toughen epoxies, but using CTBN alone increases the toughness at the cost of stiffness and heat resistance. Amine-terminated butadiene acrylonitrile (ATBN) is also used. Using ultra-fine full-vulcanized powdered rubber (UFPR) researchers have been able to improve all three, toughness, stiffness, and heat resistance simultaneously, resetting the stage for rubber toughening
Polymer blend more than one kind of polymer. A new polymers modification process, based on a simple mechanical mixture of two polymers first appeared when Thomas Hancock got one mixture of natural rubber with gutta-percha. This process generated a new polymer class called "polymer blends". Polymer blends can be broadly divided into three categories: The use of the term polymer alloy for a polymer blend is discouraged, as the former term includes multiphase copolymers but excludes incompatible polymer blends. Examples of miscible polymer blends: Polymer blends can be used as thermoplastic elastomer Polymer blend A polymer blend, or polymer mixture, is a