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Poly(ethylene succinate) (PES) and its copolyesters that contain 7, 10, or 48 mol % butylene succinate (BS) were synthesized through a direct polycondensation reaction with titanium tetraisopropoxide as the catalyst. Measurements of intrinsic viscosity (1.08-1.27 dL/g) proved the success of the preparation of polyesters with high molecular weights. The compositions and the sequence distributions of the copolyesters were determined from 1 H and 13 C NMR spectra. The distributions of ethylene succinate and BS units were found to be random. Their thermal properties were elucidated using a differential scanning calorimeter (DSC) and a thermogravimetric analyzer. No significant difference exists among the thermal stabilities of these polyesters. All of the copolymers exhibit a single glass transition temperature. Wide-angle X-ray diffractograms (WAXD) were obtained from polyesters that were crystallized isothermally. The DSC thermograms and WAXD patterns indicate that the incorporation of BS units into PES significantly inhibits the crystallization behavior of PES. The heat of fusion of ideal PES crystals is 163 J/g, as determined by the depression of the melting point of PES crystals in acetophenone.

Copolyester was synthesized and characterized as having 89.9 mol % ethylene succinate units and 10.1 mol % butylene succinate units in a random sequence, as revealed by NMR. Isothermal crystallization kinetics was studied in the temperature range (T c ) from 30 to 73 C using differential scanning calorimetry (DSC). The melting behavior after isothermal crystallization was investigated using DSC by varying the T c , the heating rate and the crystallization time. DSC curves showed triple melting peaks. The melting behavior indicates that the upper melting peaks are associated primarily with the melting of lamellar crystals with various stabilities. As the T c increases, the contribution of recrystallization slowly decreases and finally disappears. A Hoffman-Weeks linear plot gives an equilibrium melting temperature of 107.0 C. The spherulite growth of this copolyester from 80 to 20 C at a cooling rate of 2 or 4 C/min was monitored and recorded using an optical microscope equipped with a CCD camera. Continuous growth rates between melting and glass transition temperatures can be obtained after curve-fitting procedures. These data fit well with those data points measured in the isothermal experiments. These data were analyzed with the Hoffman and Lauritzen theory. A regime II ! III transition was detected at around 52 C.

Background/purpose In a previous fractural study of implant-supported crowns, it was found that the palladium−silver crowns possessed the highest fracture force. The ceramic–metal interface was examined to explain its high resistance to fracture. Materials and methods Palladium−silver crowns with the morphology of a maxillary second premolar were prepared following standard dental laboratory procedures. Crown specimens were compressed vertically in the center of the occlusal surface until fracture, using a universal testing machine. The fractured surfaces were examined using scanning electron microscopy combined with energy dispersive X-ray spectroscopy to determine the failure mode. The ceramic–metal interface of the crown was examined with electron probe microanalysis. Additionally, sheet specimens with a dimension of 10 × 9 × 4 mm 3 were prepared to examine the surface morphology and composition of palladium−silver alloy after oxidation and porcelain-fused-to-metal firing cycles. Results The average fracture force was 1425 ± 392N. Analyses with scanning electron microscopy combined with energy dispersive X-ray spectroscopy revealed that the failure mode was cohesive within the ceramic layer. Electron probe microanalysis micrographs indicated that Sn and In were found to distribute only on the alloy side of the ceramometal crown. Energy dispersive X-ray spectroscopy analysis and electron probe microanalysis micrographs confirmed that ZnO had diffused into the ceramic phase. Conclusion In 2 O 3 , SnO 2 , and ZnO were found along the interface; the presence of these oxides at the boundary promotes ceramic–metal adhesion, and this resulted in cohesive failure of the ceramic layer. ZnO was found to diffuse into the ceramic phase, and it is suggested to be beneficial for high fracture resistance in the present study.

Background/purpose In a previous fractural study, high-gold crowns possessed the second highest fracture force. The objective of this study is to analyze the interface of porcelain fused to high-gold alloy using different observation devices. Materials and methods High-gold crowns specimens with the morphology of a maxillary second premolar were compressed vertically in the center of the occlusal surface until fracture using a universal testing machine. The fractured surfaces were examined using scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (SEM/EDX) to determine the failure mode. The ceramic–metal interface of the crown was examined with electron probe microanalysis (EPMA). In addition, sheet specimens with dimensions of 10 × 9 × 4 mm 3 were prepared to examine the surface morphology and composition of high-gold alloy after oxidation using X-ray photoelectron spectrometer (XPS). Results The average fracture force was 1368 ± 312 N. Photograph of fractured crown and SEM/EDX analyses reveal that the crown initially suffered from cohesive failure in the upper and middle regions, with the fracture occurring mostly within the ceramic. XPS results and both EPMA color photomicrographs of crown and sheet specimens show that indium was observed along the porcelain–metal interface with a 1- to 2-μm disrupted zone of oxide layer. Conclusion In 2 O 3 and Au were found along the interface from the multitechnique analysis methods; the presence of this oxide at the boundary promotes ceramic–metal adhesion. In 2 O 3 is suggested to be beneficial for the second highest fracture resistance in a previous fractural study of implant-supported crowns.