Thermal, dynamic mechanical, and rheological behavior of linear low‐density polyethylene/poly(octadecene‐co‐maleic anhydride) blends

Blends of linear low-density polyethylene (LLDPE) and a 50:50 copolymer of octadecene and maleic anhydride (C18-MAH) were characterized by calorimetry, dynamic mechanical testing, and rheometry. In the solid state, the blends are essentially immiscible. No evidence was obtained for cocrystallization of the LLDPE with the paraf-finic side-chains of the C18-MAH. Interactions between the blend components were observed in three ways. First, presence of the C18-MAH in the LLDPE melt increases the nucleation rate for LLDPE crystallization. Second, side-chain crystallization in a portion of the C18-MAH component equivalent to approximately 15% of the total blend is apparently suppressed in the blends. Third, although the mechanical loss of the blends is essentially a sum of the pure components, the β relaxation of the LLDPE is absent in blends containing more than 20% C18-MAH. The blends are also immiscible in the melt. The steady and dynamic shear rheology is dominated by the immiscibility and mismatch in viscosity, η, between the two polymers. A linear dependence on blend composition was found for log η in dynamic (small strain) tests. Nonlinear behavior with positive and negative deviations from linearity was found for log η in steady shear (large strain) tests.