Effect of Blended Ionomers on the Strain Hardening of Polyester-Type Elastomer/Ionomer Blends

Abstract

A Na-type ionomer based on poly(ethylene-co-methacrylic acid) (EMAA-Na ionomer) was blended with thermoplastic polyester elastomer (TPEE) and the effect on uniaxial elongational viscosity was investigated. To clarify the effect of the degree of neutralization (ND) by the EMAA-Na ionomer on strain hardening of TPEE/ionomer blends system, EMAA-Na ionomers with different NDs were prepared and blended with TPEE above their melting temperature using a twin screw extruder. An unexpected strong strain hardening was observed for a ND above 40% for a TPEE/EMAA-Na blend ratio of 80/ 20 wt %, which corresponds to the critical ND for the formation of ion aggregates. The results can be explained using the acid-cation exchange mechanism proposed by Vanhoorne and Register. It is considered that blending EMAA-Na ionomers is an effective method for the modification of TPEE with respect to the intensity of strain hardening under uniaxial elongation.KEY WORDS: TPEE / Ionomer / Rheology / Ion Aggregates / Uniaxial Elongation / Strain Hardening / Ionomers are polymers that include a small amount of metal ionic salt groups. Poly(ethylene-co-methacrylic acid) (EMAA) neutralized with sodium (Na) cations is widely used in industrial applications, such as golf balls and food packaging film, etc. The structural and mechanical properties of ionomers in both the solid and melt states have been extensively investigated. Ionic groups tend to form ionic aggregates in a hydrophobic polymer matrix.1-5 Dielectric, dynamic mechanical relaxation and melt rheological studies show that the occurrence of microphase separation of ionic aggregates and the hydrocarbon matrix is dependent on the degree of neutralization (ND) of the ionomer. Hirasawa et al. and Tachino et al. suggested that for a EMAA-Na ionomer in the solid state, ionic aggregates were formed when the ND exceeded 35%.6,7 Nishioka et al. reported a rheological investigation for the EMAA-Na ionomer in the melt state that showed ionic aggregates are formed at a ND of approximately 40%. 8 These results indicate that there is a critical ND for the formation of ion aggregates that exists between 35-40%.Many melt rheological studies on EMAA ionomers have been conducted; however, most of these studies were related to EMAA ionomers as a polymer matrix. [8][9][10][11][12][13][14][15] We consider that research of ionomers for the modification of melt rheology should be noted for new applications. To clarify the roll of blended ionomers for the modification of melt rheological properties, especially uniaxial elongational viscosity, is an important field of research for industrial application.Much research has already been carried out regarding the solid state application of ionomers to blend with polymer materials. [16][17][18] However, very few studies on the melt rheological properties of ionomer blend systems have been carried out. 10,19,30,31 The development of methods for the modification of melt rheological properties such as strain hardening under uniaxial elongation is of significant importan...

Elongational rheology of biodegradable poly(lactic acid)/poly[(butylene succinate)‐co‐adipate] binary blends and poly(lactic acid)/poly[(butylene succinate)‐co‐adipate]/clay ternary nanocomposites

“…To elucidate the effect of PBSA content on the strain hardening behavior of the binary blends and ternary nanocomposites, a nonlinear parameter λ n is defined as follows33: in which η E ,linear and η E ,nonlinear are the elongational viscosities in the short time region and the long time region, respectively.…”