Yi-Dong Li

Structure and Properties of Soy Protein/Poly(butylene succinate) Blends with Improved Compatibility

A novel environmentally friendly thermoplastic soy protein/polyester blend was successfully prepared by blending soy protein isolate (SPI) with poly(butylene succinate) (PBS). To improve the compatibility between SPI and PBS, the polyester was pretreated by introducing different amounts of urethane and isocyanate groups before blending. The blends containing pretreated PBS showed much finer phase structures because of good dispersion of polyester in protein. Consequently, the tensile strength and modulus of blends increased obviously. A lower glass transition temperature of protein in the blends than that of the pure SPI, which was caused by the improvement of the compatibility between two phases, was observed by dynamic mechanical analyzer (DMA). The hydrophobicity, water resistance, and moisture absorption at different humidities of the blends were modified significantly due to the incorporation of PBS.

Unique crystalline/crystalline polymer blends of poly(ethylene succinate) and poly(p-dioxanone): miscibility and crystallization behaviors.

Miscibility and crystallization behaviors of poly(ethylene succinate)/poly(p-dioxanone) (PES/PPDO) blends were investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM), and wide-angle X-ray diffraction (WAXD). PES/PPDO blends are completely miscible as proved by the single grass transition temperature (T(g)) dependence of composition and decreasing crystallization temperature of the blends in comparison with the respective component. POM observation suggests that simultaneous crystallization of PES and PPDO components in the blends took place, spherulites of one component can crystallize inside the spherulites of the other component, and the unique interpenetrated crystalline morphology has been formed for the blends in the full composition range. Isothermal crystallization kinetics of the blends was studied by DSC and the data were analyzed by the Avrami equation. The results suggest that the crystallization mechanisms of the blends were unchanged but the overall crystallization rates were slowed down compared with neat PES and neat PPDO. WAXD results indicate that the crystal structures of PES and PPDO did not change in the blends.

Thermal and Thermo-Oxidative Degradation of Biodegradable Poly(Ester Urethane) Containing Poly(L-Lactic Acid) and Poly(Butylene Succinate) Blocks

A novel biodegradable poly(ester urethane; PEU) was synthesized by chain extension reaction of dihydroxylated poly(L-lactic acid; PLLA) and poly(butylene succinate; PBS) using diisocyanate as a chain extender. The kinetics of thermal and thermo-oxidative degradation of PEU containing PLLA and PBS blocks were studied by thermogravimetric analysis (TGA). TGA results indicated that PEU was more stable in air than in nitrogen and went through a two-stage degradation process irrespective of the experimental atmosphere. Activation energy of each stage was calculated by means of Kissinger, Kim-Park, Friedman, Flynn-Wall-Ozawa, and Kissinger-Akahira-Sunose methods. For the first stage, the activation energy value obtained in air was slightly higher than the corresponding value obtained in nitrogen; and for the second stage, the activation energy showed a much higher value in air than in nitrogen. The Coats-Redfern method was employed to study the degradation mechanism of each stage. The results indicated that the degradation of the first stage follows the P3/4 mechanism irrespective of the experimental atmosphere; the degradation of the second stage of PEU obeys the P1 mechanism in nitrogen while P3/2 in air.

Non-isothermal Crystallization Behaviors of Poly(p-dioxanone) and Poly(p-dioxanone)-b-poly(butylene succinate) Multiblock Copolymer from Amorphous State

A novel alternating multiblock copolymer poly(p-dioxanone)-b-poly(butylene succinate) (PPDOBS) was prepared through a two-step process including the initial ring-opening polymerization of p-dioxanone (PDO) initiated by poly(butylene succinate)-diol and the following chain extension, using hexamethylene diisocyanate (HDI) as a chain extender. The resulting PPDOBS was characterized by hydrogen nuclear magnetic resonance spectroscopy (1H NMR), wide angle X-ray diffraction (WAXD), and differential scanning calorimeter (DSC). The WAXD analysis showed that the introduction of PBS segments did not change the crystal structure of PPDO. The heating scans of DSC curves showed that the cold crystallization temperature was decreased after the introduction of PBS segments, which indicated that the ability of PPDO to crystallize was improved. The non-isothermal crystallization kinetics of PPDO and PPDOBS were evaluated by means of Avrami, Ozawa, and Mo methods. It was found that the Ozawa method was not suitable to describe the crystallization kinetics for both PPDO and PPDOBS. The results of Avrami and Mo methods showed that crystallization rate of PPDO were enhanced by introduction of PBS segments. In addition, the activation energies for non-isothermal crystallization calculated using the Kissinger method for PPDO and PPDOBS were 46 kJ/mol and 38 kJ/mol, respectively, indicating the crystallization ability of PPDO was improved after the introduction of PBS segments.