Shear-Strained Structures Induced during Hot-Melt Coating and Their Gradual Temporal Changes in Coated Layers Composed of Block Copolymer/Tackifier Blends AITranslate

Basic Information:

DOI：https://doi.org/10.1021/acsapm.2c00484

Chinese Library Classification Number:

Citation Information:

We revealed the effects of solubility difference of a tackifier to the respective components of block copolymers on shear-strained structures induced during the hot-melt coating process and their temporal changes during storage at 50 °C by the two-dimensional small-angle X-ray scattering measurements. For this purpose, three types of tackifiers were used, which were the selective resin only solubilized in the polyisoprene (PI) phase, the one preferentially solubilized in the PI phase, and the neutral resin solubilized homogeneously into both of PI and polystyrene (PS) phases. The hot-melt coated layer was composed of such a tackifier and PS-block-PI-block-PS triblock copolymer with the blended PS-block-PI diblock copolymer, which forms PS spherical microdomains embedded in the PI matrix. It was found that the amount of tackifier solubilized in the PS microdomains significantly affected the degree of structural anisotropy. It was suggested that the neutral resin solubilized in the PS phase caused the pulling-out of the PS block chains from the PS spherical microdomains during coating. Furthermore, the relaxation of the remaining shear strain, the relaxation of the structural anisotropy, and the improvement of the ordering of PS spheres during storage at 50 °C proceeded faster as compared to the cases of the selective resins because of the increased mobility of PS chains. It was also found that the d spacing of the (110) planes of the body-centered cubic lattice was larger for the case of specimens prepared by the hot-melt coating as compared to that by the solution coating. This fact implies that nanosized aggregations of the tackifier remained in the hot-melt-coated layer. Thus, this study clearly revealed that the significance of the appropriate selection of the tackifier for plasticizing the hard (PS) phase promotes suppression of structural strain and stabilization of the quality of the hot-melt-coated layer product.