text: Reactive compatibilization is the process of modifying a mixed immiscible blend of polymers to arrest phase separation and allow for the formation of a stable, long-term continuous phase. It is done via the addition of a reactive polymer, miscible with one blend component and reactive towards functional groups on the second component, which result in the "in-situ" formation of block or grafted copolymers.
  A large number of commercial polymeric products are derived from the blending of two or more polymers to achieve a favorable balance of physical properties. However, since most polymer blends are immiscible, it is rare to find a pair of polymers that both are miscible and have desired characteristics. An example of such pair is the miscible resin NORYL™, a mix of poly(phenylene oxide) and polystyrene. Immiscible blends will phase separate and form a dispersed phase, which may improve physical properties (figure 1). DuPont’s rubber toughened Nylon consists of small particles of poly(cis-isoprene) (natural rubber) in a Nylon matrix that toughen the material by arresting crack propagation.