National Research Council of Canada. NRC Industrial Materials Institute
Text, Book Chapter
A polymer blend is a mixture of at least two macromolecular substances, polymers or copolymers, in which the concentration of each polymeric ingredient is above 2 wt.%. Blends are either miscible or immiscible , The miscible polymer blends are homogeneous down to the molecular level. Their free energy and heat of mixing, ΔGm ≅ ΔH m≤0 and ∂2ΔGm/φ>2>0, where φ is the volume fraction. In these blends, the domain size is comparable to the dimension of the macromolecular statistical segment, d<20 nm. The immiscible polymer blends are those where ΔGm>0, and/or ∂2ΔG m/∂φ2<0. Most polymer blends are immiscible.