Thermal stability of modified end‐capped poly(lactic acid)

The influence of functional end groups on the thermal stability of poly(lactic acid) (PLA) in nitrogen‐ and oxygen‐enriched atmospheres has been investigated in this article using differential scanning calorimetry, thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). Functional end groups of PLA were modified by succinic anhydride and l ‐cysteine by the addition–elimination reaction. PLA was synthesized by azeotropic condensation of l ‐lactic acid in xylene and characterized by nuclear magnetic resonance. The values of the activation energies determined by TGA in nitrogen and oxygen atmospheres revealed that the character of functional end groups has remarkable influence on the thermal stability of PLA. Moreover, DMA confirmed the strong influence of functional end groups of PLA on polymer chains motion. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41105.     

Calendered linear low‐density polyethylene consolidated meat and bone meal composites

Bioplastics produced from meat and bone meal (MBM) suffer from rapid and drastic mechanical property deterioration because of their hydrophilic nature. This study investigates mechanical and water stability of composites produced from introduction of a minor component of a synthetic polyethylene as a binder phase to consolidate MBM. The milled and sieved MBM was compounded with 5–60 wt % linear low‐density polyethylene (LLDPE) and formed into composite sheets by calendering, which is an industrially relevant process. Results indicated that a minimum of 15 wt % LLDPE content was required to form a nominally continuous binder phase that allowed for good processability and environment stability of the composites. As expected, the water vapor permeability (WVP) and water absorption characteristics of the composites were intermediate between those of MBM and LLDPE. Sheets containing 15 wt % LLDPE absorbed up to 35 wt % water. Composites tested after being soaked in water showed an initial decrease in TS of about 30% for the first hour but then remained fairly unchanged in the next 72 hours, confirming their moderate environment stability. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41145.     

Small diameter tubular structure design using solvent‐free textile techniques

The aim of research was to elaborate the non‐biodegradable (made of polypropylene (PP)) and resorbable (made of polylactide (PLA)) tubular fibrous structures for the reconstruction of the vascular vessels. For the mentioned structures design, nonconventional manufacturing techniques such as melt blown, melt electrospinning, and melt electroblowing were used. Three techniques were chosen as methods allowing on the fibrous structures manufacture containing fibers in nano‐ or submicro‐size diameter. Other advantages of free‐solvent technique use is the reduction in the clinical adverse events associated with solvent resided in the fibrous structure during the fabrication. The tubular fibrous structures of PP and PLA using above‐mentioned techniques were designed. In first stage, the analysis of the processing parameters influence on the nonbiodegradable and biodegradable tubular structures fiber diameter was performed. Subsequently, the validation step was the analysis of the influence of processing parameters on PP and PLA structural properties for each manufacturing techniques was investigated. The research results confirmed the ability of the tubular structures manufacture with various fiber diameter depending on the applied technique and processing parameters. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40147.     

Effect of gas properties on the onset of flooding in small diameter inclined tubes

This work concerns the effect of gas phase properties on incipient flooding in counter-current gas–liquid two-phase flow in small diameter inclined tubes (D < 10 mm). The aim is to propose generalized correlations that can be used to predict incipient flooding in small diameter tubes. Experiments were performed in a 7 mm glass tube and at two inclination angles, i.e. 30 and 60° from the horizontal, using water as liquid phase and atmospheric air, He and CO₂ as gas phase. Previously proposed correlations for flooding prediction ( Pantzali et al., 2008) were suitably adjusted to incorporate the effect of gas phase properties. It has been proved that the flooding curves calculated using the proposed correlations are in good agreement with both the results of the present study and relevant literature data.     

Enhancing the solubility and bioavailability of isoflavone by particle size reduction using a supercritical carbon dioxide-based precipitation process

Isoflavones are a group of small molecular compounds found in many plants. Genistein is the most well studied isoflavones because of its beneficial effects in reducing menopausal symptoms, anti-oxidant and anti-cancer. The major difficulty in developing isoflavone-based healthcare products is their low water solubility. In this study, the solubility and oral bioavailability of genistein were increased by reducing its particle size using supercritical CO₂ as an antisolvent in the precipitation process. The effects of various process parameters including type of solvent, pressure of precipitation, and concentration of genistein solution on particle formation were evaluated. We found that under optimized conditions: dissolving 4 mg/mL genistein in acetone and precipitating them with supercritical CO₂ under 100 bar at 40 °C, the size of genistein particles was reduced from its original width of 10–50 μm to ∼254 nm. The reduction of genistein particle size not only increased its water solubility by 2 fold but more importantly increased its 24 h-plasma concentration by 2.6 fold after orally administrated to rats. These results proof the concept of using supercritical CO₂ as an antisolvent in the precipitation process to reduce particle size of water insoluble compounds such as genistein and to improve its oral bioavailability.     

Thermal Analysis of Charcoal from Fast-Growing Eucalypt Wood: Influence of Raw Material Moisture Content

This study aimed to investigate the influence of raw material moisture content on the properties of charcoal from fast-growing Eucalyptus benthamii wood. For that, three treatments were performed with 0, 30, and 50% in relation to the wet basis moisture of the wood samples. The carbonization process used an electric kiln with a heating rate of 1.60°C min^?1, initial temperature of 25 to 600°C at the end, kept constant at that temperature for two hours. Variables were statistically analyzed for charcoal yield, non-condensable gases, liquor, and fixed carbon and properties: fixed carbon content, volatile, ash, bulk density, and moisture content of charcoal. According to the results, the charcoal produced from dry wood presented the highest properties, yet the charcoal produced from wood with 30% moisture content showed similar properties.     

模拟古代铸铁在典型碱液中的电化学行为

通过动电位极化曲线法,在几种含不同氯离子浓度的典型碱性水溶液中研究了模拟古代灰口铸铁、白口铸铁的电化学行为。结果表明,在不同碱性溶液中同种铸铁试样对氯离子浓度的钝化/活化敏感性不同;不同材质的铸铁试样在相同溶液中对氯离子的敏感性也不相同。并且,对于同种溶质的碱性溶液,铸铁对氯离子的敏感性则随着溶液的pH值增加而降低。这一结果将为铁质文物脱盐除氯的终点判定提供重要的依据。     

医用尼龙血液过滤网材料的差热分析

医用尼龙血液过滤网材料的标准鉴别方法为差热分析(DSC),但尼龙材料的多重熔融以及加工历史、测试条件等给熔点测试带来许多不确定因素。文章通过改变DSC测试条件,测试某定型尼龙血液过滤网材料,分析其材料种类和加工热历史等信息,并进一步确定应用差热分析技术定性鉴别常见医用尼龙血液过滤网材料品种的合理程序。     

圆钢管钢纤维活性粉末混凝土短柱轴压性能试验研究

为研究圆钢管钢纤维活性粉末混凝土（RPC）短柱的轴压性能,完成了7根外径219~273mm的圆钢管钢纤维RPC短柱轴压性能试验,分析了套箍系数、径厚比对轴压试件荷载-应变曲线和破坏特征的影响。结果表明：套箍系数ξ在0.63~0.88时,荷载-位移曲线在峰值荷载后出现下降段,短柱呈现剪切破坏模式;当ξ≥1时,在到达峰值荷载后,荷载下降幅度明显减小或出现回升趋势,短柱呈现腰鼓形破坏模式。在达到峰值荷载的85%之前,试件处于弹性阶段,钢管纵向应变大于横向应变;弹塑性阶段,钢管横向应变增加较快,其横向变形系数超过钢管的泊松比并逐渐增大,钢管对RPC的约束作用不断增强。随着混凝土抗压强度提高,其横向变形系数减小,钢管对核心区RPC约束效果降低。     

Performance-based seismic fragility analysis of retaining walls based on the probability density evolution method

Seismic fragility analysis is an efficient way to study the seismic behaviour and performance of structures under the excitation of earthquakes of varying intensity, and an essential part of the seismic risk assessment of structures. A recently developed dynamic reliability methodology, the probability density evolution method (PDEM), is proposed for the dynamic reliability and seismic fragility analysis of a retaining wall. The PDEM can obtain an instantaneous probability density function of the seismic responses and easily acquire the seismic reliability of the structural system. An important advantage of the PDEM is its high efficiency relative to that of the Monte Carlo simulation method, which is often used in the reliability and fragility analysis of structures. The present study uses a typical gravity retaining wall to illustrate stochastic seismic responses and fragility curves that can be obtained by the PDEM. The combined uncertainties of the seismic force and soil properties are explicitly and systematically modelled by stochastic ground motions and random variables respectively. The performance of the retaining wall is analysed for different acceptable levels of backfill settlement. Additionally, seismic fragility curves are constructed without assuming the distribution of the seismic response.