Synthesis, thermal, and rheological properties of poly(trimethylene terephthalate)/BaSO4 nanocomposites

Abstract

AbstractA novel method was developed for fabricating poly(trimethylene terephthalate) (PTT)/BaSO4 nanocomposites using in situ polymerization. A nano‐BaSO4 suspension was prepared by reacting H2SO4 with Ba(OH)2 in 1,3‐propanediol (PDO). The mean size of original nano‐BaSO4 is 15–23 nm. PTT matrix was synthesized by condensation polymerization of bis(3‐hydroxypropyl terephthalate) after the completion of transesterification of dimethyl terephthalate (DMT) with PDO. It was found that the addition of BaSO4 had little influence on the synthesis of PTT. The properties of nanocomposites with a wide range of BaSO4 fraction were systematically studied. The morphologies of the composites were investigated by transmission electron microscopy (TEM), which showed that agglomerate structures did not form until BaSO4 content higher than 8 wt%. The thermal properties of the nanocomposites were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The DSC results revealed that the triple endothermic melting phenomenon is only observed for the nanocomposites which contained 4 wt% BaSO4, other samples exhibit double endothermic melting. These results indicated that nano‐BaSO4 could induce a microcrystal to form more perfect morphology and restrain the formation of much thicker lamellar crystallinity, that is, nano‐BaSO4 could induce the formation of more uniform crystallinity. Besides, the crystallization ability of the composites was greatly improved by loading nano‐BaSO4. The TGA results suggested that nano‐BaSO4 slightly increased the maximum‐decomposing‐rate temperature 1 (Tmax1), but markedly increased the maximum‐decomposing‐rate temperature 2 (Tmax2). Furthermore, the steady‐state shear behavior of samples was investigated by a parallel‐plate rheometer. The storage modulus (G') and loss modulus (G”) curves shifted to higher modulus upon addition of 2–16 wt% of nano‐BaSO4. All of the samples investigated exhibited the expected shear‐thinning behavior. Proper contents of nano‐BaSO4 would decrease the shear viscosity of nanocomposites, whereas superfluous amounts would greatly increase the viscosity of nanocomposites and the composites which loaded 8 wt% nano‐BaSO4 revealed an equivalent shear viscosity compared to pure PTT. Copyright © 2008 John Wiley & Sons, Ltd.