ABSTRACT:The isothermal crystallization and subsequent melting behavior of poly(trimethylene terephthalate) (PTT) composites filled with nano-CaCO 3 were investigated at designated temperatures with differential scanning calorimetry. The Avrami equation was used to fit the isothermal crystallization. The Avrami exponents were determined to be 2-3 for the neat PTT and PTT/CaCO 3 composites. The particles of nano-CaCO 3 , acting as nucleating agents in the composites, accelerated the crystallization rate, with the half-time of crystallization decreasing or the growth rate constant (involving both nucleation and growth rate parameters) increasing. The crystallization activation energy calculated from the Arrhenius formula was reduced as the nano-CaCO 3 content increased from 0 to 2%, and this suggested that nano-CaCO 3 made the molecular chains of PTT easier to crystallize during the isothermal crystallization process. Subsequent melting scans of the isothermally crystallized composites exhibited triple or double melting endotherms: the greater the content was of nano-CaCO 3 , the lower the temperature was of the melting peak. The degree of crystallization deduced from the melt enthalpy of composites with the proper concentration of nano-CaCO 3 was higher than that of pure PTT, but it was lower when the nano-CaCO 3 concentration was more than 2%. The transmission electron microscopy pictures suggested that the dispersion state of nano-CaCO 3 particles in the polymer matrix was even when its concentration was no more than 2%, whereas some agglomeration occurred when its concentration was 4%. Polarized microscopy pictures showed that much smaller or less perfect crystals formed in the composites because of the interaction between the molecular chains and nano-CaCO 3 particles.

The organic–inorganic hybrid boron‐containing phenol–formaldehyde (BPFR) resin/SiO2 nanocomposites was synthesized in‐situ from boric acid, phenol, and tetramethoxysilane. The structure of BPFR modified and the distributions of silicon element were studied by Fourier‐transform infrared spectroscopy, energy dispersive X‐ray spectrometry, and transmission electron microscope, respectively. The glass transition temperature (Tg) was determined by torsional braid analysis. The results show that silicon element distribution is homogeneous, and the size of nanosilica is about 40–60 nm. The thermal stability and kinetics parameters of thermal degradation were determined by thermogravimetry analysis (TGA). TGA results show that the resin modified has higher heat resistance property when the additive quantity of SiO2 was 3 wt%. The temperature of 5% weight loss is 487.7°C, which is 12.4°C higher than that of common BPFR. The residual ratio of 3 wt% SiO2/BPFR was 62.3% at the temperature of 900°C, which is 11.2% higher than that of common BPFR. The mechanics loss peak Tp of 3% SiO2/BPFR is 33°C higher than common BPFR. Fiberglass‐reinforced BPFR modified by 3 wt% SiO2 has better mechanical and dielectric properties than that of common BPFR. POLYM. COMPOS., 2008. © 2007 Society of Plastics Engineers

Two novel liquid crystalline epoxy resins (LCER) based on bisphenol-S mesogen, 4,4 0 -Bis-(2,3-epoxypropyloxy)-sulfonyl bis(1,4-phenylene) (p-BEPSBP) and sulfonyl bis(4,1-phenylene) bis[4-(2,3-epoxypropyloxy)benzoate] (p-SBPEPB), were synthesized. Their liquid crystalline behavior and structure were characterized by Fourier transmittance infrared ray (FTIR), differential scanning calorimetry (DSC), 1 HNMR, polarized optical microscopy (POM) and X-ray diffraction (XRD). The results show that p-BEPSBP is a kind of thermotropic liquid crystal and has a smectic mesophase with a melting point (T m ) at 165 C; the p-SBPEPB is a kind of nematic mesophase with the temperature range of 155-302 C from the T m to the clearing point T i . The curing behaviors and texture of the liquid crystalline epoxy resins with 4,4 0 -diaminodiphenyl ether (DDE) were also studied by DSC and some kinetic parameters were evaluated according to the Ozawa's method. The dynamic mechanical properties of curing products were also investigated by torsional braid analysis (TBA), and the results suggest that the dynamic mechanical loss peak temperature (T p ) of p-BEPSBP/DDE and p-SBPEPB/DDE is 120 and 130 C, respectively.

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Abstract3‐Glycidyloxypropyl‐polyhedral oligomeric silsesquioxanes (G‐POSS) was prepared from 3‐glycidyloxypropyl‐trimethoxysilane (GTMS) by hydrolytic condensation. The cocuring behavior and kinetics of G‐POSS with bisphenol‐A epoxy resin (BPAER) using 3‐methyl‐tetrahydrophthalic anhydride (MeTHPA) as curing agent were investigated by nonisothermal differential scanning calorimetry (DSC) and torsional braid analysis (TBA). The face distribution of silicon in the cured products was characterized by energy dispersive X‐ray spectrometry (EDS). The results show that the compatibility of G‐POSS with BPAER is very well and can cocure. The curing mechanism was proposed. The relationship of Ea and conversion α can be obtained by the isoconversional method of Kissinger. These curing reactions can be described by the Šesták–Berggren (S–B) equation and can be depicted by the following equation: $ \font\abc=cmmib10\def\bi#1{\hbox{\abc #1}}{\bi d\alpha \over \bi dt} {=} A\ {\bf exp} (-{E_a \over RT}) {{\alpha}}^m ({\bf 1}-a)^n $. TBA analysis indicated that Tg was decreased when the contents of G‐POSS is over to 30 wt%. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers