The modulus of the amorphous component in polyethylenes

Various approaches to representing the modulus of a semicrystalline polymer as a composite crystal‐amorphous material are applied to the extensive data of Illers on the shear modulus of linear and branched polyethylenes as a function of crystallinity and temperature. It is found that the modulus of linear polyethylene is fit very well over the range of 47‐96 percent crystallinity from − 180 to 100°C by the Tsai‐Halpin equation with a single value of the contiguity factor, ζ, and crystallinityindependent phase moduli. A value of ζ ≃ 1(near lower bound behavior) is found. In branched polyethylene the behavior below the β relaxation ( T < T β ) is similar to linear polyethylene, but above T β , the behavior indicates that the amorphous modulus is crystallinity dependent. The amorphous component modulus as a function of temperature for linear polyethylene extracted from the fitting process is discussed in terms of various interpretations of the relaxations (α, β, γ) in polyethylene.