Effect of degree of neutralization of sodium-based ionomers on hot-tack properties |
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Authors: | Tatsuya Sehata Takuto Yoshiura Tomonori Koda Hiroko Yano Motoaki Isokawa Akihiro Nishioka |
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Affiliation: | 1. Graduate school of Organic Materials Science, Yamagata University, Yonezawa, Japan;2. Dow-Mitsui Polychemicals Co.Ltd., Ichihara, Japan |
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Abstract: | The hot-tack properties of ethylene-methacrylic acid copolymers neutralized with sodium (Na) cations to produce ionomers were investigated. Specimens with neutralization degrees of 20%, 54%, and 70% were examined. After testing at low sealing temperatures (<130°C), the highest hot-tack strength was obtained from a specimen with a neutralization degree of 20%. In contrast, at high sealing temperatures (>140°C), the hot-tack strength increased with an increasing degree of neutralization. Observations of the surfaces of samples tested at low sealing temperatures after hot-tack tests showed that specimens having a neutralization degree of 20% exhibited cohesive breakdown while the 54% and 70% specimens underwent interfacial delamination. The effect of sealing temperature on hot-tack strength was determined by assessing the rheological properties of molten ionomers. The results suggested that, when testing at low sealing temperatures, a low melt viscosity provided high hot-tack strength by allowing flow diffusivity of the resin at the sealed interface. At high sealing temperatures, uniaxial elongational viscosity related to strain hardening contributed to the high hot-tack strength of these Na-based ionomers. The present study highlights the important effect of ionic aggregates on hot-tack properties. |
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Keywords: | adhesion ionomers rheology |
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