Mechanochemical degradation treatment of TBBPA: A kinetic approach for predicting the degradation rate constant

Persistent organic pollutants (POPs) have been banned from production and use. The brominated flame retardant TBBPA is a type of POP and has been widely used in plastics to enhance their fire resistance. However, because the natural degradation of TBBPA is a difficult process, it is particularly important to propose an appropriate treatment method. Hence, the mechanochemical degradation of TBBPA is a feasible method because it does not require high temperature heating and does not produce secondary pollutants after the reaction is completed. In this study, we performed a series of TBBPA degradation experiments with a planetary ball mill and confirmed the degradation efficiency and the rate under various conditions. Then, we conducted a discrete element method (DEM) simulation to compute the collision energies in the ball mill. By comparing the degradation rate and collision energies, we revealed that the mechanochemical degradation rate of TBBPA can be predicted by a normal collision energy computed by DEM simulation. This kinetic approach enables us to predict the rate constant and consequently, the energy consumption for the mechanochemical treatment. The predictability of these parameters will encourage the further application of mechanochemical reaction in the field of POPs treatment.     

水化龄期及光源类型对TiO2水泥砂浆降解罗丹明B性能的影响研究

采用干混法制备了掺TiO₂水泥砂浆,测试了砂浆力学性能,研究了TiO₂掺量、水化龄期、光源类型及光强等因素对罗丹明B降解性能的影响。结果表明,随TiO₂掺量增加,砂浆对罗丹明B的降解率增加,而砂浆强度则呈先增加后降低规律。在相同TiO₂掺量条件下,砂浆对罗丹明B的降解率随水化龄期延长而降低。与水化3 d试件相比,水化28、180 d掺5%TiO₂水泥砂浆对罗丹明B的降解率分别降低7.84%、11.21%。砂浆对罗丹明B的总降解率随光源类型、光强的变化不明显,但其降解速率随紫外线光强的增大而显著提高。在波长(λ=365 nm)、光射时间(60 min)均相同的条件下,与20 W紫外灯相比,200 W紫外灯照射下的掺5%TiO₂水泥砂浆对罗丹明B的降解率提高约80%。与太阳光相比,200 W紫外灯照射60 min砂浆对罗丹明B的降解率为85.54%,仅降低约1.46%。     

Effects of hydrogen on the mechanical response of X80 pipeline steel subject to high strain rate tensile tests

Hydrogen‐induced degradation of X80 pipeline steel was investigated through a high strain rate tensile test (2 × 10^?4/s) with interposed unloading, reloading, aging at 30°C, or annealing at 200°C with or without hydrogen charging. The results indicated that plasticity degradation does not occur in the hydrogen‐precharged specimens; however, hydrogen embrittlement occurs in the reloading stage when the specimens are charged with hydrogen in the unloading stage after applying a prestrain. Interposed aging at 30°C or annealing at 200°C can also increase the degradation. It indicates that the hydrogen traps caused by the strain along with hydrogen charging are the major source of dislocations. The formation of a hydrogen atmosphere around mobile dislocations, which is related to the rates of hydrogen diffusion and dislocation movement, plays an important role in the degradation process. Both pinning and depinning of dislocations affect plasticity degradation.     

PP/纳米CaCO3复合材料的紫外光老化行为

用FT-IR研究了紫外光老化聚丙烯(PP)/纳米CaCO<,3>和相容剂改性PP/纳米CaCO<,3>复合材料的微观结构变化,结果表明,纳米CaCO<,3>和相容剂加入加快了PP紫外光氧化降解,但对PP光氧化降解机理无影响.纳米CaCO<,3>促进PP光氧化降解作用较相客荆的大.纳米CaCO<,3>加快PP紫外光氧化降...     

快速水解法测定羽毛及其降解物中的色氨酸

通过提高水解温度,减少水解时间的前处理方法,用氨基酸自动分析仪测定羽毛及其降解物中色氨酸的测定值。分析结果表明,采用4mol/LLiOH、145℃、水解5h的快速水解法与常规前处理方法所测得色氨酸含量基本一致,方法回收率91%,变异系数2.24%。可缩短分析时间,且不影响分析结果的准确度。     

PLA的酸性降解及其机理分析

目的研究PLA在酸性条件下降解及其机理。方法通过在酸性水溶液中降解不同时间,得到一系列不同相对分子质量的PLA,利用黏度法、凝胶色谱以及红外光谱对PLA的降解机理进行研究。结果 PLA的数均分子量随降解时间的增加逐渐减小,失重率和降解率逐渐升高,在降解23 d后,产物的数均分子量从4050降至2490,失重率从9.9%升至75.1%,降解率从98.3%提高至99.0%。降解过程中,PLA的相对分子质量分布系数基本保持不变,一直维持在1.25左右。结论在降解过程中,酯键的断裂是PLA初步降解的主要方式,H+浓度的升高有利于催化酯键的断裂,加剧PLA降解。     

频繁启停过程中拉杆微裂纹引起的组合转子性能退化研究

燃气轮机的性能下降很大程度上是由于燃机的核心部件——组合转子的退化导致的,因此,非常有必要重点研究组合转子的性能退化规律.组合转子局部结构的损伤,必将导致整体性能的下降.从该角度出发,建立组合转子的有限元模型,对组合转子拉杆裂纹进行扩展计算,定义组合转子性能退化量,分析了不同尺寸的拉杆裂纹对转子性能退化的影响.研究结果表明:随着裂纹尺寸的逐渐增加,组合转子的退化速率逐渐加快;不同微裂纹拉杆的分布形式对组合转子退化程度影响不同,当微裂纹拉杆相邻分布时组合转子退化速率最快,裂纹拉杆180°分布时组合转子退化速率最慢.     

A novel pseudo‐maximum likelihood estimation method for accelerated degradation tests under Wiener process

For reliability assessment based on accelerated degradation tests (ADTs), an appropriate parameter estimation method is very important because it affects the extrapolation and prediction accuracy. The well‐adopted maximum likelihood estimation (MLE) method focuses on interpolation fitting and obtains results via maximizing the likelihood of the observations. However, a best interpolation fitting does not necessarily yield a best extrapolation. In this paper, therefore, a pseudo‐MLE (P‐MLE) method is proposed to improve the prediction accuracy of constant‐stress ADTs by considering the degradation mechanism equivalence under Wiener process. In particular, the degradation mechanism equivalence is characterized by a mechanism equivalence factor which presents the proportional relationship between degradation rate and variation. Then, the mechanism equivalence factor is determined via a two‐step method. The other model parameters can be estimated by the general MLE method. The asymptotic variances of acceleration factors and the p‐quantile of product failure time under normal condition are adopted to compare the statistical properties of the proposed method and the general MLE approach. Numerical examples show that the novel P‐MLE method may not achieve a maximum likelihood but can provide more benefits regarding prediction accuracy enhancement especially when the sample size is limited.     

Enzymatic degradation and radiopaque attenuation of iodinated poly(ester-urethane)s with inherent radiopacity

Biodegradable radiopaque iodinated polyurethanes (I-PUs) based on poly(ε-caprolactone) diol (PCL) as soft segment have been synthesized using 4,4′-isopropylidene-(2,6-diiodophenol) (IBPA) as chain extender. In order to elucidate the effect of iodinated chain extender on degradation properties of I-PUs, a control polyurethane with bisphenol A as chain extender was also synthesized. The enzymatic degradation study of these I-PUs was carried out using phosphate-buffered solution (pH 7.4) at 37 °C. The mass loss, surface morphology, iodine content, radiopacity, hydrophilicity and thermal properties of the samples during degradation were characterized with scanning electron microscopy (SEM), energy-dispersive X-ray detector (EDX), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and static contact angle. Results of enzymatic degradation during 3 months indicated that the incorporation of iodinated chain extender greatly hindered the in vitro degradation of I-PUs compared with the control PU-C sample. The reason for the retarded degradation was attributed to the bulky iodine atoms on IBPA chain extender with steric hindrance, which decreased the surface hydrophilicity of I-PUs and slowed water/lipase diffusion rate. Moreover, the radiopacity of I-PUs does not sharply attenuate after long-time degradation, which is useful for interventional biomedical applications.     

Photocatalytic degradation of indigo carmine in aqueous solution by TiO2-coated non-woven fibres

The photocatalytic degradation of indigo carmine has been investigated in aqueous solutions using TiO2 coated non-woven fibres as photocatalyst. The experiments were carried out to investigate the factors influencing the photocatalytic degradation, such as the previous adsorption in the dark, initial concentration of dye solution, temperature, and pH. The experimental results show that adsorption is an important parameter controlling the apparent kinetic constant of the degradation. The photocatalytic degradation rate was favoured by a high concentration of solution in respect to Langmuir-Hinshelwood model. The degradation rate was pH and temperature dependent with a high degradation rate at high temperature.     

新型含磷阻燃共聚酯热降解动力学

利用F lynn-W a ll-O zaw a方法,对纤维用聚酯(PET)及二羧乙基苯基氧化磷(BCPO)改性的阻燃聚酯(FR-PET)的热失重(TG)降解行为进行了研究,发现聚酯和阻燃聚酯的热降解过程相近,热降解活化能没有较大的变化,阻燃剂BCPO的引入对热降解过程无显著影响。     

Effect of inorganic salts,amino acids and proteins on the degradation of pure magnesium in vitro

The possibility of magnesium and its alloys in medical applications is actively investigated in these days for the realization of biodegradable metallic devices. However, the degradation behavior and mechanisms of magnesium and its alloys in physiological environment such as inside the human body have not been elucidated. In this study, we performed 14-d long immersion tests of pure magnesium (3N) in 4 kinds of physiological solutions simulating the body fluids to examine the effects of the chemical components of the body fluids on the degradation of magnesium. The degradation rate of pure magnesium was strongly influenced by the kinds of the solution used. The highest degradation rate was obtained in NaCl, followed by E-MEM, Earle's solution, and E-MEM+FBS. The average degradation rate in NaCl for 8–14 d is about 100 times larger than that in E-MEM+FBS, which is the closest solution to human blood plasma. These results show that protein adsorption and insoluble salt formation retarded magnesium degradation, whereas organic compounds such as amino acids encourage the dissolution of magnesium. Buffering the solution also influenced the degradation rate; buffering NaCl with HEPES increased the degradation rate but buffering with NaHCO₃ decreased it. Based on these results, the use of appropriate solution such as E-MEM+FBS is important for in vitro evaluation of the magnesium degradation rate under the physiological environment simulating inside the human body.     

ON THE REACTIVITY OF C60 FULLERENE WITH DIENE RUBBER MACRORADICALS. I. THE CASE OF NATURAL AND SYNTHETIC CIS-1,4-POLYISOPRENE UNDER ANAEROBIC AND THERMOOXIDATIVE DEGRADATION CONDITIONS

C₆₀ fullerene has been studied as thermal stabilizer and as antioxidant of both natural rubber (cis-1,4-polyisoprene) and synthetic cis-1,4-polyisoprene. The study has been conducted respectively under nitrogen flow and under air flow by simultaneous thermogravimetric analysis and differential thermal analysis (TGA-DTA) on rubber samples containing known quantities of fullerene in comparison to a “blank” of pure rubber. The results show that C₆₀ fullerene (in absence of oxygen) is a thermal stabilizer of cis-1,4-polyisoprene because it reacts with the polyisoprene macroradicals formed by the thermally-induced chain scission reaction slowing down the degradation reaction. Conversely, under thermo-oxidative degradation conditions (in air flow) fullerene C₆₀ acts as an antioxidant for cis-1,4-polyisoprene, provided that the heating rate of the samples is slow (5°/min). At higher heating rates (20°C/min) C₆₀ does not show any antioxidant effect.     

多孔ZnO/羟基磷灰石生物复合材料的制备与性能

利用放电等离子烧结技术制备多孔ZnO/羟基磷灰石（HA）生物复合材料,研究不同纳米ZnO含量对ZnO/HA复合材料微观结构、孔隙特征、力学性能、矿化和降解性能的影响。结果表明:烧结后ZnO/HA复合材料主要由HA相和ZnO相组成;随着ZnO含量提高,多孔ZnO/HA复合材料孔隙率缓慢增大,抗压强度略有减小,弹性模量变化不大;多孔ZnO/HA复合材料的孔隙率>40%,孔径在50～500 μm之间,抗压强度>148 MPa,弹性模量为6.5 GPa左右,能够满足骨修复材料的要求;模拟人工体液中矿化和降解实验表明,多孔ZnO/HA复合材料浸泡7天后表面开始形成大量类骨磷灰石层,且随着ZnO含量增加,磷灰石形成能力明显增强而降解速率加快。      

电极材料对含酚废水处理效果的影响

含酚废水是难降解有机废水,电化学方法处理工业废水具有高效、快速、无二次污染及适应性强的特点.该法是基于电极上的直接氧化和产生的自由基的间接氧化除去废水中的污染物.电极材料是电化学处理方法的核心,在很大程度上决定了废水处理效率.着重概述了不同电极材料对酚类降解效果的影响,认为该方法处理含酚废水应选择高过电位、性能稳定、活性高、成本低的电极材料.     

V-N-TiO2/凹凸棒土和V-N-TiO2/玻璃珠复合材料的吸附及光催化性能

采用自主研制的V-N-TiO₂光催化剂、V-N-TiO₂/凹凸棒土、V-N-TiO₂/玻璃珠光催化复合材料,选用腐殖酸、亚甲基蓝、二甲基甲酰胺为目标降解物,对复合材料的吸附特点和光催化性能进行了研究。研究表明,除对二甲基甲酰胺,V-N-TiO₂光催化剂、V-N-TiO₂/凹凸棒土、V-N-TiO₂/玻璃珠光催化复合材料、凹凸棒土、玻璃珠负载材料对腐殖酸、亚甲基蓝的吸附符合Langmuir等温模型,V-N-TiO₂/凹凸棒土、V-N-TiO₂/玻璃珠光催化复合材料的负载形式对其吸附性能影响最大。V-N-TiO₂光催化剂、V-N-TiO₂/凹凸棒土、V-N-TiO₂/玻璃珠光催化复合材料对腐殖酸、亚甲基蓝的光催化反应均符合一级动力学方程。V-N-TiO₂/凹凸棒土、V-N-TiO₂/玻璃珠光催化复合材料的光催化性能与吸附平衡常数K_a、光催化表面反应的速率常数K_r有关。当光催化复合材料对不同目标降解物的吸附平衡常数差别较大时,吸附平衡常数越大,反应速率常数越大,光催化反应进行得越快;当光催化复合材料对不同目标降解物的吸附平衡常数差别不大时,光催化表面反应的速率常数越大,反应速率常数则越大,光催化反应进行得越快。      

PHB,crystalline and amorphous magnesium alloys: Promising candidates for bioresorbable osteosynthesis implants?

In this study various biodegradable materials were tested for their suitability for use in osteosynthesis implants, in particular as elastically stable intramedullary nails for fracture treatment in paediatric orthopaedics. The materials investigated comprise polyhydroxybutyrate (PHB), which belongs to the polyester family and is produced by microorganisms, with additions of ZrO₂ and a bone graft substitute; two crystalline magnesium alloys with significantly different degradation rates ZX50 (MgZnCa, fast) and WZ21 (MgYZnCa, slow); and MgZnCa bulk metallic glasses (BMG). Push-out tests were conducted after various implantation times in rat femur meta-diaphysis to evaluate the shear forces between the implant material and the bone. The most promising materials are WZ21 and BMG, which exhibit high shear forces and push-out energies. The degradation rate of ZX50 is too fast and thus the alloy does not maintain its mechanical stability long enough during the fracture-healing period. PHB exhibits insufficient mechanical properties: it degrades very slowly and the respective low shear forces and push-out energy levels are unsatisfactory.     

Degradation of alachlor in aqueous solution by using hydrodynamic cavitation

The degradation of alachlor aqueous solution by using hydrodynamic cavitation was systematically investigated. It was found that alachlor in aqueous solution can be deomposed with swirling jet-induced cavitation. The degradation can be described by a pseudo-first-order kinetics and the degradation rate was found to be 4.90 × 10⁻² min⁻¹. The effects of operating parameters such as fluid pressure, solution temperature, initial concentration of alachlor and medium pH on the degradation rates of alachlor were also discussed. The results showed that the degradation rates of alachlor increased with increasing pressure and decreased with increasing initial concentration. An optimum temperature of 40 °C existed for the degradation rate of alachlor and the degradation rate was also found to be slightly depend on medium pH. Many degradation products formed during the process, and some of them were qualitatively identified by GC–MS.     

纳米纤维素/聚乳酸复合材料的降解性能

目的研究纳米纤维素/聚乳酸(NCC/PLA)复合薄膜在不同降解条件下的降解情况。方法在p H值为3,7,11的溶液及紫外光照射条件下,降解自制的复合薄膜,通过测失重率、扫描电子显微镜观察、X射线光电子能谱分析等手段,分析p H值、光照和NCC的添加与复合材料降解能力间的关系,研究其降解机理,并与纯PLA薄膜对比。结果 NCC/PLA复合薄膜在碱性条件下质量损失最快,酸性稍慢,中性更慢,紫外光照射下最慢,复合薄膜质量损失均比纯PLA薄膜多。在p H值为3和7的溶液及紫外光照射降解后,NCC/PLA复合薄膜氧碳原子数量的比值均比未降解时增大,分别提高了35.16%,36.66%,38.65%。结论 NCC的添加提高了NCC/PLA复合薄膜的降解性能,在不同降解过程中,薄膜表面C原子所占比例减少,相对地O原子所占比例增加,氧碳原子数量的比值增大。     

羟基磷灰石纳米纤维增强甲基丙烯酸酐改性明胶复合水凝胶的制备及性能

采用溶剂热法制备了具有超高长径比的羟基磷灰石(HAP)纳米纤维,并将其与甲基丙烯酸酐改性明胶(GelMA)结合,利用紫外光交联制备了HAP纳米纤维/GelMA复合水凝胶。通过SEM、XRD、力学测试、溶胀测试、降解测试、细胞培养等对HAP纳米纤维/GelMA复合水凝胶进行结构表征和性能测试。SEM断面观察表明,HAP纳米纤维/GelMA水凝胶呈三维孔隙贯通的多孔结构。力学实验表明,HAP纳米纤维能有效增强水凝胶的弹性模量,且随着HAP纳米纤维添加量的增加,力学性能增强效果越明显。溶胀实验表明,当HAP纳米纤维质量分数为5.2wt%~14.2wt%时,HAP纳米纤维复合水凝胶的溶胀率变化不明显,当质量分数为18.2wt%时,溶胀率降低。降解实验表明,HAP纳米纤维的加入能有效保持水凝胶结构形态,使其更加稳定可控。细胞包裹培养实验表明,HAP纳米纤维/GelMA复合水凝胶能为细胞提供良好的三维生长环境,表现出优良的生物相容性。本实验制备的HAP纳米纤维/GelMA复合水凝胶在组织工程领域有着良好的应用前景。