Multiple melting and partial miscibility of ethylene‐vinyl acetate copolymer/low density polyethylene blends

Abstract

Multiple melting behaviors and partial miscibility of ethylene-vinyl acetate (EVA) copolymer/low density polyethylene (LDPE) binary blend via isothermal crystallization are investigated by differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD). Crystallization temperature T ( C) is designed as 30, 50, 70, 80 C with different crystallization times t (min) of 10, 30, 60, 300, 600 min. The increase of crystallization temperature and time can facilitate the growth in lateral crystal size, and also the shift of melting peak, which means the completion of defective secondary crystallization. For blends of various fractions, sequence distribution of ethylene segments results in complex multiple melting behaviors during isothermal crystallization process. Overlapping endothermic peaks and drops of equilibrium melting points of LDPE component extrapolated from HoffmanWeeks plots clarify the existence of partial miscibility in crystalline region between EVA and LDPE. WAXD results show that variables have no perceptible influence on the predominant existence of orthorhombic crystalline phase structure.

Multifunctional hydrolyzed EVA membranes with tunable microstructure and water barrier properties

“…When t h ¼ 8 h (Fig. 6b), a crystalline peak related to the VOH diffractant plane (200) of the orthorhombic lattice appears at 2θ¼24.070.21 [59]. The presence of the crystalline phase of EVOH starts to be visible in this case (Fig.…”

Non-isothermal crystallization kinetics of partially miscible ethylene-vinyl acetate copolymer/low density polyethylene blends

“…As shown in Figure 1, overlapping of exotherms widely existed in blending situation, which was mostly due to the partial miscibility [7] between EVA and LDPE. Both widely used Jeziorny theory and Mo's method suitable for neat polymers, are based on the exothermic enthalpy integration of single exothermic peak.…”

“…While those defective chain segments were repelled to the surface of the existing crystal. They were forced to crystallize under a lower temperature later with more deficiency during arrangement, thus formed the secondary crystallization region [7]. It has been widely accepted that the short ethylene branches in LDPE could inhibit its overall crystallization behavior [19].…”

“…It has been accepted that, a high ambient temperature would inhibit the nucleation but facilitate the crystal growth of polymer molecules. While a low temperature environment could have contrary influences on crystallization behaviors [7,25,26]. Intense cooling rate has limited the time needed for a sufficient primary crystallization growth.…”

“…This could lead to multiple crystallization stages based on complex thermal history. Regarding their binary blends, the partial miscibility has been studied in our previous works via isothermal crystallization [7]. However, their crystallization under non-isothermal conditions would be more complicated than the ideal isothermal situation.…”