Stannous-acetylacetonate:A new catalyst for poly(trimethylene terephthalate) synthesis

Stannous-acetylacetonate was prepared efficiently and characterized by ^1H NMR and FT-IR. Its catalytic activity for poly（trimethylene terephthalate） （PTT） synthesis was investigated. By this catalyst, the degree of esterification of pure terephthalic acid was up to 91.7% after reaction at 260 ℃ for 2 h, while the intrinsic viscosity and content of terminal carboxyl groups of the corresponding PTT polymerized at 260 ℃, 60 Pa for 2 h was 0.8816 dL/g and 17 mol/t,respectively. Stannous-acetylacetonate was more active and promising than tetrabutyl titanate and stannous octoate for PTT synthesis.

Thermal degradation and isothermal crystalline behavior of poly(trimethylene terephthalate)

Poly（trimethylene terephthalate） （PTT） is an excellent fiber material. Its thermal degradation and isothermal crystalline behaviors were in this study investigated using thermogravimetric analysis （TGA）, thermogravimetric analysis-Fourier transform infrared spectroscopy （TGA-FTIR） analysis, differential scanning calorimetry （DSC） and X-ray diffraction （XRD）. The thermal degradation mechanism of PTT follows Mclafferty rearrangement principle. The PTTwithintrinsicviscosity（IV） of 0.74 dL/g has a maximum crystallinity of about 55% at 190 ℃, as demonstrated by DSC and XRD measurements consistently.

Banded Spherulites Grown from Poly(trimethylene terephthalate) Solution-cast Film

Various morphologies of poly（trimethylene terephthalate） （PTT） solution-cast thin films at different crystallization temperatures were investigated by polarized light microscopy （PLM）,atomic force microscopy （AFM） and transmitted electron microscopy （TEM）.In the range of 110-150 ℃,banded spherulite occurred and banding space gradually decreased along the radial direction from the primary nucleation site.Between 160 and 170 ℃,normal non-banded spherulite was found.Above 170 ℃,banded configuration occurred again.Lamellar growth direction of banded spherulite was determined to the crystal a-axis.

Studies on the rheological, phase morphologic, thermal and mechanical properties of poly(trimethylene terephthalate)/ ethylene propylene diene monomer copolymer grafted with maleic anhydride/metallocene polyethylene blends

The rheological,phase morphologic,thermal andmechanicalpropertiesofpoly(trimethyleneterephthalate)/metallocene polyethylene(PTT/mPE)blends in the presence of ethylene propylene diene monomer copolymer grafted with maleic anhydride(EPDM-g-MAH)as compatibilizer are studied by means of a capillary rheometer,scanning electron microscopy(SEM),differential scanning calorimetry(DSC)and thermogravimetric analyzer(TGA).Results suggest that the compatibility of PTT/mPE blends is improved greatly after the addition of a compatibilizer.The radius of the dispersed phase in the system decreases greatly when the compatibilizer is added into the blend.When the amount of compatibilizer exceeds 8 wt-%,the size of dispersed phase becomes larger again.This phenomena could be attributed to the higher viscosity of the EPDM-g-MAH phase,which is dispersed more difficulty in the PTT phase of lower viscosity,thus the mixing efficiency is apparently decreased during the melt blending process.Moreover,the melt viscosity of the blend reaches the maximal value in case of 4 wt-%compati-bilizer content,above which it would decrease again.This result is associated with the generation of more and bigger dispersed phase inside the bulk phase,thus the grafting efficiency at the interface is decreased,which could result in lower viscosity.The DSC results suggest that the mPE component shows a nucleating effect,and could increase the overall degree and rate of PTT crystallization,while the addition of a compatibilizer might slightly diminish these effects.In addition,the blend with 4 wt-%compatibilizer shows the best thermal stability.Furthermore,the Izod impact strength and the tensile strength at room temperature of the blend are also markedly improved by the addition of a 4–8 wt-%compatibilizer.

Study on the crystal morphology and melting behavior of isothermally crystallized composites of short carbon fiber and poly(trimethylene terephthalate)

The spherulites of the short carbon fiber(SCF)/poly(trimethyleneterephthalate)(PTT)compositesformedin limited space at designed temperatures,and their melting behaviors were studied by the polarized optical microscopy,atomic force microscopy(AFM),and scanning electron microscopy(SEM),respectively.The results suggest that SCF content,isothermal crystallization temperatures,and the film thicknesses influence the crystal morphology of the composites.The dimension of the spherulites is decreased with increasing SCF content,but whether banded or nonbanded spherulites will form in the composites is not dependent on SCF content.However,the crystal morphology of the composites depends strongly on the temperature.When the isothermal crystallization temperatures increase from 180℃ to 230℃,the crystal morphology of SCF/PTT composites continuously changes in the following order:nonbanded→banded→nonbanded spherulites.Disconti-nuous circle lines form in the film when the film thickness increases from 30 to 60μm.Basing on the SEM observation,it is found that these circle lines are cracks formed due to the constriction difference of the different parts of the spherulites.These cracks are formed when the film is cooled from the isothermal crystallization temperature to the room tempera-ture at a slow cooling rate;while they will disappear gradually at different temperatures in the heating process.The crack will appear/disappear first around the center of the spherulite when the film was cooled/heated.The nontwisted or slightly twisted lamellas will reorganize to form highly twisted lamellas inducing apparent banded texture of the spherulites.