Piyada Charoensirisomboon

Pull-out of copolymer in situ-formed during reactive blending: effect of the copolymer architecture

Abstract Reactive melt blending of polyamide 6 (PA) and polysulfone (PSU) was carried out and the effect of the copolymer architecture on the pull-out of the copolymer in situ-formed during reactive blending was studied. To create various block and graft copolymers by reactive blending, three types of reactive PSU were prepared and used; maleic anhydride-grafted PSU, carboxylic-grafted PSU, and phathalic anhydride-terminated PSU. Polymer blend morphology was observed by transmission electron microscopy (TEM). The TEM results suggested that the block copolymers with linear chain structures are more easily pulled out to form micelles in the matrix than the graft copolymers having branch structure with trunk chains locating in the dispersed phase. Such graft copolymers stayed at the interface and played the role of emulsifiers. By contrast, the in situ-formed graft copolymers having trunk chains locating in the matrix were easily pulled out. The micelle formation via the pull-out of copolymers took place even in the rather symmetric block or graft copolymer system. Such interfacial behavior is against the current theories on polymer–polymer interface, which deal with the chain statistics under quiescent state; implying that the hydrodynamic contribution plays an important role of the pull-out.

Interfacial behavior of block copolymers in situ-formed in reactive blending of dissimilar polymers

Reactive melt blending of polyamide 6 (PA) and polysulfone (PSU) was carried out and the interfacial behavior of in situ-formed block copolymer was studied. A series of reactive PSUs with different functional groups at chain ends were prepared and used; PSU-epoxy, -triazine and -phthalic anhydride. The morphology development during melt blending was investigated by light scattering and transmission electron microscopy. The results suggested that when coupling reaction quickly proceeded and the in situ-formed copolymers were densely accumulated at the interface, they could be easily pulled out by external shear forces to form micelles in matrix. This micelle formation led to 10 nm order dispersion as a whole at late stages of mixing. By contrast, the pull out did not take place when the coupling reaction was slow and the copolymer chains were less accumulated at the interface. In this case, the in situ-formed block copolymer acted as a simple emulsifier to yield sub-μm level dispersion. The difference between the fast and slow reaction systems was discussed in terms of a balance between thermodynamic stability of copolymer chains at the interface and hydrodynamic effect for the pull-out.

Reactive blending of polysulfone with polyamide: a potential for solvent-free freparation of the block copolymer

Abstract Reactive blending of polysulfone (PSU) and polyamide 6 (PA) was carried out at 20:80 (PSU-PA) wt. ratio using a gram-scale mixer (Mini-Max Molder). Three PSUs with different functional groups were prepared and used: maleic anhydride-grafted PSU (PSU-MAH), carboxylic acid-grafted PSU (PSU-COOH) and phthalic anhydride-terminated PSU (PSU-PhAH), having almost same molecular weight ( M w = ca. 20 k) and functional group content (ca. 90 μmole g −1 ). The change in PSU particle size with mixing time was investigated by light scattering and transmission electron microscopy. As expected, all reactive systems yielded finer particles via faster size reduction process, compared with non-reactive system. Attainable particle diameters were: ca. 1 μm for non-functionalized PSU, ca. 0.6 μm for PSU-MAH, 0.3 μm for PSU-COOH, and ca. 40 nm for PSU-PhAH. The particle size of PSU-PhAH system was comparable to that in a pre-made block copolymer synthesized by solution polymerization, suggesting a potential for the solvent-free preparation of PSU-PA block copolymer when adequate reactivity and molecular architecture are provided in reactive blending.

In situ formed copolymers as emulsifier and phase-inversion-aid in reactive polysulfone/polyamide blends

Abstract Reactive blending of dissimilar polymers involves in situ reactions of functionalized components to form a block or graft copolymer at the interface between phases. The copolymer is believed to play a role of the emulsifier to prevent particle coalescence and to improve interfacial adhesion. A mixture of non-reactive polysulfone (PSU) and small amount of reactive PSU, phthalic anhydride-terminated PSU (PSU–PhAH), was melt-blended with polyamide (PA) at 65/35 (PSU/PA) wt ratio using a miniature mixer. When the molecular weight of PSU–PhAH was high (comparable with non-reactive PSU), PA particles were dispersed in PSU matrix and the particle size was much smaller than non-reactive system, suggesting the typical emulsifying effect caused by the in situ formed block copolymer. On the other hand, when the molecular weight of PSU–PhAH was much smaller than the non-reactive PSU, phase inversion took place; i.e. at early stages of mixing, PA particles were dispersed in PSU matrix; however, at later stages the PSU particles were dispersed in PA matrix. TEM observation showed a micelle formation in PSU particles. The phase inversion mechanism was discussed in terms of the increase in viscosity of PSU phase caused by the pull-out of the in situ formed block copolymers.

Polysulfide containing s-triazine rings as a new thermoplastic elastomer: Spherulite morphology arid strain recovery behaviour

A new polymer, polysulfide containing s -triazine rings, was found to be crystalline but it showed an excellent strain recovery after large deformation; residual strain was less than 10% after 25–400% elongation. The elastic recovery was much better than low density polyethylene (LDPE), a typical rubber-like crystalline polymer. As in the case of LDPE, a four-leaf clover pattern in H v (cross-polarized) light scattering was observed, suggesting the formation of spherulites. The H v pattern deformed with bulk deformation and recovered to the original pattern after releasing, without any change in the disorder parameter of orientation correlation. The reversible change in scattering pattern suggests that the spherulite itself is highly elastic and it may render the elastomeric character in bulk.

Influence of a low molecular weight anhydride on the morphology of PSU/PA-alloys

Abstract In order to develop a new polymeric material with a nice combination of high heat resistance, chemical resistance and flow, polysulfone (PSU)/polyamide blends have been investigated. The incompatibility of these polymers can be overcome by the addition of functionalized PSU, especially anhydride terminated PSU (PSU–PhA). Since PSU–PhA sometimes contains traces of low molecular weight compounds, the influence of such reactive impurities was investigated with phthalic anhydride (PhA) as model compound. Solvent extraction and electron microscopy results suggested that the amount of in situ created PSU–PA-copolymers is significantly reduced by the addition of PhA during the extrusion process resulting in a coarsening of the morphology.