Surface Characteristics of Polyhedral Oligomeric Silsesquioxane Modified Clay and Its Application in Polymerization of Macrocyclic Polyester Oligomers

Abstract

Novel porous aminopropyllsooctyl polyhedral oligomeric silsesquioxane (POSS) modified montmorillonite clay complexes (POSS-Mts) with large interlayer distance and specific surface area have been successfully prepared via ion-exchange reaction and followed by freeze-drying treatment. The morphology of the POSS-Mts is highly influenced by the POSS concentration, pH of the suspension and drying procedure, but the interlayer distance of the POSS-Mts does not change much when the POSS concentration is above 0.4 CEC. The POSS-Mts were used as Sn-catalyst supporters to initiate the ring-opening polymerization of cyclic butylene terephthalate oligomers (CBT) for the first time. No diffraction peak was detected by wide-angle X-ray diffraction for the polymerized composites (pCBT/POSS-Mt), even at 10 wt % loading of POSS-Mt. A clay network rather than exfoliation structure was observed unexpectedly in the composites by transmission electron microscopy. The pCBT/POSS-Mt composite with 10 wt % POSS-Mt was further melt-compounded with commercial PBT resin as a master batch. The tensile properties of the resultant PBT/POSS-Mt composites were highly improved as compared to the pristine PBT due to the homogeneous dispersion of POSS-Mt in the PBT matrix.

A Review of the Recent Advances in Cyclic Butylene Terephthalate Technology and its Composites

“…[134][135][136][137][138] An increasing amount of reports on pCBT/organoclay nanocomposites can also be found. 14,65,[139][140][141][142][143][144][145][146] The low viscosity of molten or dissolved oligomers is utilized to obtain a CBT-intercalated organoclay. Subsequent ROP causes then an increase in interlayer distance along with the disintegration of the layered clay structure, as shown in figure 22.…”

“…Only few reports on complete clay exfoliation of the final nanocomposites are available, 139,146 whereas intercalated or flocculated-intercalated structures are more commonly observed. [141][142][143][144][145] Although the organoclay is successfully intercalated with CBT oligomers or even completely exfoliated before ROP, the silicate layers tend to reorganize due to the low viscosity of the molten CBT during ROP. Thus the exfoliated structure is lost and a flocculated-intercalated structure is obtained after polymerization.…”

Isocyanate toughening of pCBT/organoclay nanocomposites with exfoliated structure and enhanced mechanical properties

“…Although several researchers have shown that the organoclay was successfully intercalated with CBT oligomers or even completely exfoliated prior to ROP, the silicate layers tended to reorganize due to the low viscosity of the molten CBT during ROP. Consequently, the exfoliated structure was lost and a flocculated-intercalated structure was obtained after polymerization [16,19,20]. Similarly, clay nanocomposites made from other types of cyclic oligomers have been reported.…”

“…Nevertheless, pCBT is inherently brittle which has been ascribed to the formation of large perfect crystals with a lack of intercrystalline tie molecules [8], different crystalline morphologies [10] as well as to a low molecular weight [11,12]. An increasing amount of publications dealing with pCBT/organoclay nanocomposites can be found in the literature [7,[13][14][15][16][17][18][19][20][21]; however, despite this considerable body of papers, little is known about the mechanical properties of these materials [15,18,20] and information about the deformation behaviour is rare. Most researchers employ the low viscosity of molten or dissolved oligomers in order to obtain a CBT-intercalated organoclay.…”

“…Subsequent ROP causes an increase in interlayer distance along with the disintegration of the layered clay structure. Nevertheless, obtaining complete clay exfoliation is rather difficult [13], whereas intercalated structures and flocculated-intercalated structures are more commonly observed [15,16,[18][19][20][21]. Although several researchers have shown that the organoclay was successfully intercalated with CBT oligomers or even completely exfoliated prior to ROP, the silicate layers tended to reorganize due to the low viscosity of the molten CBT during ROP.…”