Blend Polymers are similar to metal alloys. They are mixtures of two or more polymers to create a new material with different physical properties.
Polymer blends can be:
Immiscible: The polymers do not mix together, creating a 'two phase blend'. In other words, the two polymers are together in the same mixture but they remain chemically separate. An easy way to think about this is picturing cooking oil in water; they are part of the same mixture but they remain separate. If the polymer blend is made from two polymers, it will exhibit two glass transition temperatures. This is the most common type of polymer blend.
Compatible: The polymers do not mix together, like an immiscible polymer. Unlike an immiscible polymer, the polymers are able to interact with each other at a sufficient strength resulting in uniform properties across the material.
Miscible: The polymer blend is single phase. In other words, the polymers are able to mix together and resulting in a material that has only one glass transition temperature. PC-ABS.