Nai Xu

Clean and rapid synthesis of double metal cyanide complexes using mechanochemistry

A novel and green chemistry technique is presented for the synthesis of double metal cyanide (DMC) complexes that are further used for the copolymerization of CO2 and propylene oxide. The catalytic activity and selectivity are improved by this strikingly efficient and practically applicable method. The mechanosynthesis of DMC reveals clear merits.

Isothermal Cold Crystallization, Heat Resistance, and Tensile Performance of Polylactide/Thermoplastic Polyester Elastomer (PLA/TPEE) Blends: Effects of Annealing and Reactive Compatibilizer

The combined influences of crystallinity and reactive compatibilizer—a multifunctional epoxide (ADR)—on morphology, tensile performance, and heat resistance of polylactide/thermoplastic polyester elastomer (PLA/TPEE) (80/20) blends were investigated. Annealing involved an isothermal cold crystallization of PLA matrix was performed to increase crystallinity of the samples. First, isothermal cold crystallization kinetics were investigated using differential scanning calorimetry measurement. It was found that the addition of ADR decreased the crystallization rate of the samples. The maximum crystallinity of the annealed samples also decreased from 40% to 34% while ADR loading increased from zero to 1.0 phr. Furthermore, influence of crystallinity on mechanical performances of the PLA/TPEE sample was researched. The heat resistance of the sample showed a significant enhancement while increasing its crystallinity. Meanwhile, the tensile ductility of the crystallized PLA/TPEE sample became very poor due to the embrittlement with increased crystallinity and the incompatibility between PLA and TPEE. However, the annealed PLA/TPEE/ADR samples with high crystallinity kept a higher tensile ductility because ADR greatly improved the interfacial compatibility. Differences in tensile fracture behaviors of the quenched and annealed PLA/TPEE samples with and without ADR were discussed in detail. At last, crystallized PLA/TPEE/ADR blends with excellent heat resistance and high tensile ductility were obtained by annealing and reactive compatibilization.

Crystallization Behavior and Melting Characteristics of Isotactic Polypropylene Nucleated by a Novel Nucleating Agent

The crystalline structure, morphology, and nonisothermal crystallization and melting behavior of isotactic polypropylene (iPP) with and without a novel nucleating agent containing amide group (TMC-328) were investigated with differential scanning calorimetric (DSC), polarized optical microscopy (POM) and X-ray diffraction (XRD). TMC-328 could increase the crystallization temperature and accelerate the crystallization rate of iPP. As an efficient α-form nucleating agent, the addition of TMC-328 could obviously reduce the spherulite size of iPP. There is a critical concentration of TMC-328. When the content of TMC-328 is 0.1%, iPP matrix exhibits the maximum crystallization peak temperature (123 °C) and the maximum crystallinity of 45.0%. With the content of TMC-328 increasing, crystallinity of iPP matrix decreases obviously. XRD measurements indicate that the crystal structure of the α-form of iPP is unaffected by TMC-328.

Preparation and Characterization of Poly(propylene carbonate)/Alkali Lignin Composite Sheets by Calendering Process

PPC is a new biodegradable aliphatic polycarbonate with poor thermal stability and mechanical properties which is difficult to form sheets or films and so on. Through the addition of alkali lignin, thermal stability and mechanical properties of PPC was improved largely. PPC/ alkali lignin sheets could be prepared. DSC results showed that the thermal stability of PPC was improved by the introduction of alkali lignin. SEM showed good dispersion of alkali lignin particles into PPC matrix that resulted in good miscibility. Improved mechanical properties and thermal stability of PPC/ alkali lignin blends were attributed to stronger interfacial interaction of PPC and alkali lignin. These results indicate that blending PPC with alkali lignin is an efficient and convenient method to improve the properties of PPC.

Rheological Property of Sodium Alginate-Agar-Montmorillonite Ternary Solution

The rheological properties of sodium alginate (SA)/agar (AR)/montmorillonite (MMT) solutions were investigated using a rotational viscometer. The dependence of solution apparent viscosity on rotation speed, MMT proportion and solution temperature were researched systematically. Furthermore, the relation of apparent viscosity and micro-structure of the ternary solution was also discussed.

Isothermal Crystallization Behavior and Kinetics of Poly (lactic acid) Filled with a Novel Nucleating Agent

The crystallization behavior and crystalline structure of poly (lactic acid) (PLA) filled with a novel nucleating agent (TMC328), which is a kind of aromatic amide derivatives, were investigated using differential scanning calorimetry (DSC) and wide angle X-ray (XRD). In isothermal crystallization from the melt, the present of TMC328 remarkably affected the isothermal crystalline behaviors of PLA. PLA/0.5% TMC328 sample exhibited very short crystallization half-times at 90-130 °C. Furthermore, the Avrami theory was used to describe the isothermal crystallization kinetics of PLA/TMC328 samples. It is confirmed that TMC328 showed a significant heterogeneous nucleation effect on the crystallization of PLA matrix. Moreover, XRD measurement indicates that TMC328 is a kind of α-form nucleating agent for PLA.

Preparation of Polymer Composite Latex via Miniemulsion Polymerization: Fluorinated Acrylate as Co-Stabilizer and Functional Modifier

The silica/polyacylate composite latex was prepared via miniemulsion polymerization. Fluorinated acrylate monomer was used the co-stabilizer and hydrophobic modifier. The effect of fluorinated acrylate on stability of the composite latex was compared with the traditional co-stabilizer. The composite latex and the resultant film were characterized by Fourier transformation infrared spectroscopy, Dynamic laser scattering, Water contact angle. Fluorinated acrylate can stabilize the miniemulsion polymerization as the co-stabilizer and the resultant film has good durability of hydrophobicity under high moisture environments.

Nonisothermal Crystallization Kinetics of Isotactic Polypropylene Filled with a Novel Nucleating Agent

The nonisothermal crystallization kinetics of isotactic polypropylene (iPP) filled with a novel nucleating agent (TMC328) was studied by using differential scanning calorimetric. The commonly used Arami, Ozawa, and Mo models were used to model the crystallization kinetics, and it appears that Arami and Mo models can well describe the nonisothermal crystallization behaviors of iPP/TMC328 blends. The results indicate that a small amount of TMC328 can obviously enhance the kinetic crystallizability of iPP due to its heterogeneous nucleation effect.

Copolymerization of Carbon Dioxide and Propylene Oxide with Multi-Metal Cyanide Complexes as Catalyst

A novel and green mechanochemical technique, the grinding-based method, was applied for synthesis of multi-metal cyanide (MMC) complexes. In order to discovery the effect of metal element on structure and catalyst efficiency, the obtained three MMCs were made from deferent three metal salts groups, which including ZnCl2 to NiCl2 to K3Fe(CN)6 molar ratio of 4:3:1 (MMC-1), ZnCl2 to NiCl2 to K3Co(CN)6 molar ratio of 4:4:1 (MMC-2), and ZnCl2 to NiCl2 to K4Fe(CN)6, respectively. And three MMCs were further used for copolymerization of CO2 and propylene oxide. FTIR and 1H NMR results shown, the alternating copolymerization obtained anticipated poly(propylene carbonate) with high catalytic activity. Comparing to the conventional solvent-based synthesis, the strikingly efficient and practically applicable grinding-based method reveals clear merits for syntheses of MMC complexes.