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Crystallization Ability (crystallization + ability)
Selected AbstractsThermal properties and phase morphology of melt-mixed poly(trimethylene terephthalate)/poly(hexamethylene isophthalamide) blendsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Fang-Chyou Chiu Abstract This work examines the thermal properties and phase morphology of melt-mixed poly(trimethylene terephthalate) (PTT)/poly(hexamethylene isophthalamide) (PA 6I) blends. Two temperatures, i.e., 250 and 260°C, are used to prepare the blends, respectively. Differential scanning calorimetry results indicate the immiscible feature of the blends. It is thus concluded that the ester-amide interchange reaction hardly occurred in the PTT/PA 6I blends. Depending on the composition and mixing temperature, the crystallization ability of PTT in the blends is either enhanced or hindered. Basically, a lower PA 6I content shifts the PTT melt crystallization to a higher temperature, whereas a higher PA 6I content causes an opposing outcome. The original complex melting behavior of neat PTT becomes more regular after the incorporation of 60 wt % or 80 wt % of PA 6I. Thermogravimetry analyses (TGA) show that the thermal stability of the blends improves as the PA 6I content increases. The two-phased morphology of the blends is examined by scanning electron microscopy (SEM). Polarized light microscopy (PLM) results reveal that the PTT spherulites become coarser with the inclusion of PA 6I; only smaller/dispersed crystallites are observed in the blend with 20 wt % of PTT. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] An efficient synthetic route to well-defined theta-shaped copolymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2009Gang-Yin Shi Abstract A series of well-defined ,-shaped copolymers composed of polystyrene (PS) and poly(,-caprolactone) (PCL) with controlled molecular weight and narrow molecular weight distribution have been successfully synthesized without any purification procedure by the combination of atom transfer radical polymerization (ATRP), ring-opening polymerization (ROP), and the "click" chemistry. The synthetic process involves two steps: (1) synthesis of AB2 miktoarm star copolymers, which contain one PCL chain terminated with two acetylene groups and two PS chains with two azido groups at their one end, (,,,,-diacetylene-PCL) (,-azido-PS)2, by ROP, ATRP, and the terminal group transformation; (2) intramolecular cyclization of AB2 miktoarm star copolymers to produce well-defined pure ,-shaped copolymers using "click" chemistry under high dilution. The 1H NMR, FTIR, and gel permeation chromatography techniques were applied to characterize the chemical structures of the resultant intermediates and the target polymers. Their thermal behavior was investigated by DSC. The mobility decrease of PCL chain across PS ring in the theta-shaped copolymers restricts the crystallization ability of PCL segment. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2620,2630, 2009 [source] Nonisothermal melt crystallization kinetics of poly(ethylene terephthalate)/Barite nanocompositesPOLYMER COMPOSITES, Issue 9 2010Chunhua Ge Poly(ethylene terephthalate) (PET)/Barite nanocomposites were prepared by direct melt compounding. The nonisothermal melt crystallization kinetics of pure PET and PET/Barite nanocomposites, containing unmodified Barite and surface-modified Barite (SABarite), was investigated by differential scanning calorimetry (DSC) under different cooling rates. With the addition of barite nanoparticles, the crystallization peak became wider and shifted to higher temperature and the crystallization rate increased. Several analysis methods were used to describe the nonisothermal crystallization behavior of pure PET and its nanocomposites. The Jeziorny modification of the Avrami analysis was only valid for describing the early stage of crystallization but was not able to describe the later stage of PET crystallization. Also, the Ozawa method failed to describe the nonisothermal crystallization behavior of PET. A combined Avrami and Ozawa equation, developed by Liu, was used to more accurately model the nonisothermal crystallization kinetics of PET. The crystallization activation energies calculated by Kissinger, Takhor, and Augis-Bennett models were comparable. The results reveal that the different interfacial interactions between matrix and nanoparticles are responsible for the disparate effect on the crystallization ability of PET. POLYM. COMPOS., 31:1504,1514, 2010. © 2009 Society of Plastics Engineers [source] Synthesis, thermal, and rheological properties of poly(trimethylene terephthalate)/BaSO4 nanocompositesPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 10 2009Chenguang Yao Abstract A 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. [source] | ||||||||||