原油流动性改进剂

本文从聚合物化学结构的角度分大类综述了实验室研制和工业应用的各种原油流动性改进剂,探讨了研制中的问题.     

Crystallisation behaviour and transparency of poly(lactic acid) nucleated with dimethylbenzylidene sorbitol

In this paper, dimethylbenzylidene sorbitol (DMBS) was applied to poly(lactic acid) (PLA) as a nucleating and clarifying agents. Eight level concentrations, from 0.25 to 10?wt-%, were added and measured some changes in the thermal, mechanical, physical and morphological properties. Experimental results revealed that the nucleated PLA crystallised earlier together with the reductions of the crystallisation temperature (T_c) at all DMBS concentrations, while the glass transition temperature (T_g) reduced by around 10°C. The degree of crystallinity (X_c) increased from 1.48 to 16.6% corresponding to the decreased crystallisation time (t_c) from more than 40 to less than 5?min at 100°C. The nucleated PLA maintained its clarity at all DMBS concentrations, with reductions of the haze value from around 36–29%. The tensile modulus and tensile strength increased slightly with the content of DMBS up to 1.5?wt-%. Beyond this content, they dropped slightly.     

Preparation and Characterization of Polyvinylpyrrolidone/L-leucine Amino Acid–Modified Montmorillonite/Chiral Diacid–Functionalized Mg-Substituted Fluorapatite Nanocomposites by Ultrasonic-Assisted Rapid Process

In this work, the surface of synthetic nanosized Mg-substituted fluorapatite particles was modified with biodegradable diacid N-trimellitylimido-L-leucine as a coupling agent in methanol. Furthermore, different contents of N-trimellitylimido-L-leucine-modified Mg-substituted fluorapatite were doped into polyvinylpyrrolidone/L-leucine-modified montmorillonite material to prepare novel ternary polyvinylpyrrolidone/modified montmorillonite/N-trimellitylimido-L-leucine-Mg-substituted fluorapatite nanocomposites by an efficient sonication process. Nanocomposite containing 5?wt% modified montmorillonite and 3, 5, and 7?wt% N-trimellitylimido-L-leucine-modified Mg-substituted fluorapatite contents were prepared and labeled as polyvinylpyrrolidone/modified montmorillonite/N-trimellitylimido-L-leucine-Mg-substituted fluorapatite 3, polyvinylpyrrolidone/modified montmorillonite/N-trimellitylimido-L-leucine-Mg-substituted fluorapatite 5, and polyvinylpyrrolidone/modified montmorillonite/N-trimellitylimido-L-leucine-Mg-substituted fluorapatite 7, respectively. The structure and morphology of the aforesaid products were characterized by different analytical apparatuses.     

Delamination of Mg-Al Layered Double Hydroxide on Starch: Change in Structural and Thermal Properties

Mg-Al layered double hydroxide decorated starch bionanocomposites (starch/layered double hydroxide) are prepared by solution intercalation method. The bionanocomposites are systematically characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and high-resolution transmission electron microscopy techniques. The thermal stability of starch is enhanced due to dispersion of layered double hydroxide within the starch matrix. The chemical resistance property of starch is improved substantially with slight sacrifice in biodegradation behavior by the delamination of layered double hydroxide in starch matrix. Herein, layered double hydroxide acts as potential laminated filler for change in structural, thermal, and chemical resistance properties of starch with little sacrifice in biodegradable behavior.     

Dispersion Stability and Tribological Characteristics of TiO2/SiO2 Nanocomposite-Enriched Biobased Lubricant

The stable dispersion of nano-additives is highly desirable for the effective lubrication performance of nanolubricants. The compatibility of base oil with selected nano-additives is required for uniform and stable dispersion. This research evaluated the dispersion stability and tribological characteristics of nano-TiO₂/SiO₂ (average particle size 50 nm) as an additive in a biobased lubricant. The wear protection and friction reducing characteristics of the formulations were evaluated by four-ball extreme pressure tests and piston ring–cylinder liner sliding tests. Surface analysis tools, including scanning electron microscopy, energy-dispersive X-ray spectroscopy, and atomic force microscopy, were used to characterize the worn surfaces. Results showed that the nanolubricants demonstrated appreciable dispersion capability in the absence of a surfactant and an improvement in load-carrying capacity, antiwear behavior, and friction reduction capability.     

Structure development and properties of high-speed melt spun poly(butylene terephthalate)/poly(butylene adipate-co-terephthalate) bicomponent fibers

Ultra-high-speed bicomponent spinning of poly(butylene terephthalate) (PBT) as sheath and biodegradable poly(butylene adipate-co-terephthalate) (PBAT) as core was accomplished with the take-up velocity up to 10 km/min. The structure development of the individual component and the properties of PBT/PBAT fibers were investigated through the measurements on differential scanning calorimetry, wide-angle X-ray diffraction, birefringence and tensile test. Due to the mutual interaction between two polymer-melts along the spinline, the processability of both components in PBT/PBAT bicomponent spinning was improved compared with those of corresponding single component spinnings. Furthermore, in PBT/PBAT fibers, the structure development of PBT component was found to be greatly enhanced, which led to the improvement in its thermal and mechanical properties; whereas the structure development of PBAT component was significantly suppressed, in which nearly non-oriented structure was observed in both crystalline and amorphous phases.     

可降解PBT/PEG共聚物的合成及降解行为研究

采用大分子酯交换反应制备了可降解的聚对苯二甲酸丁二醇/聚乙二醇共聚醚酯.采用核磁共振氢谱表征了产物的结构,研究了共聚物的吸水率和水解降解行为;探讨了共聚物结构对其性能的影响.当聚乙二醇的质量分数增大、摩尔质量不变时,共聚物的吸水率和降解速率同时增大;而当聚乙二醇质量分数保持一定、摩尔质量增大时,共聚物的吸水率增大,但对降解速率的影响则较为复杂.在一定范围内,PEG摩尔质量增大,共聚物的降解速率降低,但摩尔质量继续增大时,降解速率急剧增大.     

生物降解材料聚乙醇酸及乙醇酸共聚物的新发展

介绍了生物降解性材料聚乙醇酸及乙醇酸共聚物的发展现状,综述了聚乙醇酸的合成、乙交酯的纯化、乙醇酸聚合催化剂的选择、乙醇酸聚合物的降解机理、乙醇酸均聚和共聚改性及乙醇酸共聚物在生物医学领域和生态学领域的应用,并讨论了乙醇酸共聚物的发展前景。     

Preparation of L-PLA submicron particles by a continuous supercritical antisolvent precipitation process

Submicron particles of L-polylactic acid (L-PLA) without residual solvent were prepared by a continuous supercritical antisolvent (SAS) recrystallization process. Methylene chloride (CH₂C1₂) was used as a carrier solvent of L-PLA. Experiments were performed with changing process parameters such as pressure and temperature at constant concentration. Also, L-PLA initial concentrations in methylene chloride were varied from 0.3 to 4 wt%. The flow rates of CO₂ and solution, which were introduced into the precipitator, and nozzle diameter were kept unchanged in all of the experiments. It was found that the SAS process gives fine tuning of particle size and particle size distribution (PSD) by simple manipulations of the process parameters. In all cases of SAS recrystallization experiments, the formed spherical fine particles with a smooth surface were non-agglomerated and free flowing. Mean particle size of the L-PLA microparticles formed was varied from 0.1 to 1 μm by means of adjusting the system pressure and/or temperature.     

Development and characterization of photopolymerizable biodegradable materials from PEG-PLA-PEG block macromonomers

As tissue engineering and drug delivery applications increase in both number and complexity, the demand for new synthetic biocompatible polymers with precisely tailored properties grows accordingly. Block copolymers are a particularly promising biomaterial as the physical and physiological properties of these polymers can be closely controlled through manipulation of the type and organization of the blocks in the polymer's backbone. In this work, poly(ethylene glycol) (PEG) and poly(lactic acid) (PLA) were incorporated into PEG-PLA-PEG block macromonomers with (meth)acrylate functionality to form photopolymerizable, highly cross-linked polymers for potential use in a variety of biomedical applications. Simply by directing the PLA:PEG ratio in these macromonomers, the hydrophobicity, physical behavior, degradation, and biocompatibility of the resulting polymer were controlled. Specifically, it was found that by increasing the PLA:PEG ratio, the degree of water uptake and the mechanical strength of the material is significantly decreased, while the glass transition temperature and degradation of the PEG-PLA polymers are delayed. Additionally, the biocompatibility of the PEG-PLA polymers is significantly influenced by the chemical composition of the material as increased PLA generally yields greater cell compatibility. By demonstrating the versatility of the photopolymerizable PEG-PLA polymers, the results of this study indicate that these materials have the potential to serve as a synthetic biomaterial platform, in which the properties of the polymer can be tailored to a variety of tissue engineering or drug delivery applications.