Effect of metal cation type on the structure and properties of ethylene ionomers

Abstract

SYNOPSISThermal properties by DSC, stiffness, melt viscosity, tensile properties, and dynamic mechanical properties were measured for the Na+, K', Mg2+, Zn2+, Cu2+, Mn2+, and Co2+ salts of poly (ethylene-co-methacrylic acid) (EMAA) . The changes in the structure and properties with increasing neutralization are larger in the alkaline and alkaline earth metal salts than in the transition metal salts. The stiffness shows a maximum at 33% neutralization in both the alkaline and alkaline earth metal salts, while no maxima are found up to 60% neutralization in the transition metal salts. The microphase separation of salt group aggregates is observed in both the alkaline and alkaline earth metal salts, but is not seen in the transition metal salts. These differences were attributed to both the stronger ionic interactions and the larger number of carboxyl groups associated with the alkaline and alkaline earth metal salts in the ordered structure of ionic salt groups (ionic crystallites). The mechanical properties measured at low strain, such as stiffness and yield stress, strongly depend on the degree of the crystalline order of the ionic crystallites. The high-strain properties, such as tensile strength and elongation at break, depend on the strength of the ionic interactions and the valence of the cation.

Review and critical analysis of the morphology of random ionomers across many length scales

“…postulated that at higher temperatures, ionic aggregates underwent an orderdisorder transition, that is, the atomic arrangement inside the aggregates was ordered below that temperature and disordered above that temperature. This interpretation has been the subject of many papers since that time [33,34,[102][103][104][105][106][107][108][109][110][111]. EMAA or EAA copolymer ionomers have been exclusively used, and the primary evidence for this interpretation has been a DSC endothermic peak at 508C with time that grows slowly with room temperature annealing.…”

Strong Attractive Interaction between Ethylene Ionomer and Carboxyl Groups of Styrene-Co-Methacrylic Acid

“…Ionomer retains pseudcross-linked structure mediated by ionic aggregates. Due to the existence of ionic aggregates, stiffness and impact resilience of EMAA ionomer are higher than those of EMAA [1][2][3][4][5][6][7][8] .…”

“…They also reported that the lowest neutralization degree for formation of ionic aggregates is 80 % for EMAA ionomer neutralized with zinc ion 2,3) . Existence is reported of ionic aggregates in EMAA ionomer at even 300 ºC which is higher than melting temperature 9) .…”

Structure and Properties of Ionomers Based on Ethylene-Co-Methacrylic Acid Copolymer (Emaa)

“…Kohzaki et al [6] found that the moduli of EMAA ionomers increased with aging time and ascribed it to the formation of subcrystalline ethylene in EMAA ionomers. However, Hirasawa et al [7,8] and Tadano et al [9] explained that an increase in moduli was due to the formation of ordered structure during aging process. They also reported that the order structure (ionic crystallite) did not form during the cooling process from melt, although it could form in the aging process at room temperature after the moding from melt, resulting in the increase in stiffness of EMAA ionomers.…”