金属材料的高应变率塑性变形及纳米化

塑性变形方法是目前研究与制备金属纳米晶材料的技术方法之一,包括低应变率变形和高应变率变形2种．作者对金属材料在表面机械研磨和高能球磨这2种高应变率塑性变形条件下的微观组织演化及纳米晶形成机理的研究和最新进展进行了综述,旨在更好地理解该力学条件下金属材料的纳米化现象,以促进纳米材料的制备研究．     

乳化-热交联法制备明胶微球

采用乳化-热交联法制备了明胶微球,研究了乳化条件对微球粒径大小和溶胀性的影响.研究结果表明,最佳的乳化条件为:明胶溶液质量分数为20%,水油比为1:5(体积比),乳化温度为50℃,乳化时间为30 min,冷却时间为1.5 h,冷却温度为4℃.采用该方法可制备出粒径为50～1400 μm,溶胀率为150%～400%的明胶微球.     

酸预处理对酶法骨明胶功能性质和分子质量分布的影响

本文以牛骨粉为原料,采用酶解法制备明胶,考察了骨粉预处理试剂——盐酸的浓度对明胶产品的冻力、粘度、分子量分布和等电点的影响.研究表明,随着骨粉预处理用的盐酸浓度的增大,明胶产率降低.骨粉经过盐酸预处理后,明胶产品的冻力大于300 bloom g,高于原料未经盐酸处理得到的明胶产品.与传统的碱法工艺明胶相比,酶法明胶具有高冻力、高等电点和相对较低的粘度等特点.采用聚丙烯酰胺凝胶电泳表征明胶的分子质量分布,酶法明胶不但具有传统碱法明胶具有的96 KDa、97 KDa、193 KDa和289 KDa组分,而且具有165 KDa和120 KDa组分.酶法明胶的等电点在碱性范围内,随着预处理用盐酸浓度的增大,明胶产品的等电点升高.骨料的预处理工艺对明胶的产率、冻力、粘度、等电点和分子质量分布有重要的影响,在明胶制备过程中,通过调控骨料预处理酸浓度可以调控明胶的技术指标.     

Electrospun electroactive nanofibers of gelatin‐oligoaniline/Poly (vinyl alcohol) templates for architecting of cardiac tissue with on‐demand drug release

In this study, grafted gelatin with oligoaniline (GelOA) was synthesized and then mixed with Poly (vinyl alcohol) (PVA). Several scaffolds with different ratio of PVA/GelOA were electrospun to fabricate electroactive scaffolds. GelOA was characterized using Fourier‐transform infrared spectroscopy (FTIR); moreover, nanofiber properties were evaluated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and scanning electron microscope (SEM) analyses. Nanofibers diameter was decreased with aniline oligomer increment form 300 to 150 nm because of the hydrophobic nature of the aniline oligomer. Aniline oligomer electroactivity was studied using cyclic voltammetry, which exhibited two redox peaks at 0.4 and 0.6. Moreover, aniline oligomer enhancement resulted in melting point increasing from 220°C to 230°C because of the crystallinity increment. To assess the biocompatibility of nanofibers, cell viability and cell adhesion were tracked using mesenchymal stem cell (MSCs). It was revealed that the presence of aniline oligomer leads to enhancing the conductivity, thermal properties and lowering the degradation rate and drug release. Among of different scaffolds, sample with high content of GelOA shows better behavior in physical and biological properties. Accumulative drug releases under applied electrical field at 40 minutes showed that the drug release for stimulated condition is about 33% more than the unapplied electrical field one.     

NMR relaxometry study of gelatin based low-calorie soft candies

ABSTRACT

Soft candies are popular confectionery products. The most significant concern on the consumption of these products is the high amount of sugar and thus the high calories. The use of low-calorie sweeteners is a desirable trend in confectionery research. In this study, gelatin-based soft candies were formulated by using different sweeteners and their characterisation was performed using high and low field nuclear magnetic resonance (NMR) relaxation experiments. To complement the information obtained by NMR experiments, moisture content, water activity, texture analysis and differential scanning calorimeter experiments were also conducted. T₁ and T₂ relaxation times were measured at both low and high fields and also temperature-dependent measurements were conducted at the high field system. Candies were formulated by substitution of sucrose with maltitol, isomalt and stevia at 30%, 50% and 70% ratios. Significant difference was observed on relaxation times. T₁ values were best described by a mono-exponential model, whereas for T₂ relaxation times a bi-exponential model gave better results at both fields.     

Crosslinking of gelatin membranes with ferulic acid or glutaraldehyde: Relationship between gas permeability and renaturation level of gelatin triple helices

This study investigated the gas separation membranes made with gelatin, crosslinked with ferulic acid (FA) and blended with polyethylene glycol (PEG) 200, by using a solvent‐free procedure. Gas permeation properties (He, N₂, O₂, and CO₂) of these “green membranes” were studied and discussed in relation with their structure. Differential scanning calorimetric measurements were carried out to determine the gelatin triple helical renaturation level. The lowest permeability values [He and CO₂ permeability (4.5 × 10^?2 Barrer) with CO₂/O₂ selectivity of 14.5] were reached with gelatin/PEG 200 uncrosslinked membranes showing the highest renaturation level (40%). Crosslinking with FA lead to less rigid and brittle materials than GTA and to 10 times more permeable membranes compared with uncrosslinked membranes. Membranes crosslinked with glutaraldehyde broke during gas permeation measurements. Results demonstrated that higher gas permeability values were closely related to lower renaturation level of gelatin. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 280–287     

多孔磁性明胶微球的制备与结构表征

首先通过乳化法得到磁性明胶微球, 然后在高速搅拌条件下向乳液中直接加入正硅酸乙酯(TEOS), 制备出多孔磁性明胶微球. 用SEM, TEM观察了微球的微观形貌, 发现微球呈疏松多孔状结构. 用FT-IR, TGA, VSM等测试手段对微球的结构和性能进行表征. 结果表明, 二氧化硅掺杂于磁性明胶微球中. TEOS在反应中作为明胶微球的交联固化剂, 推测其固化机理是物理交联固化. 实验证实二氧化硅改性后, 磁性明胶微球内部磁性颗粒氧化速度有所降低. 所得到的多孔磁性明胶微球表现出铁磁性.     

Phase behavior and properties of polyvinyl alcohol/gelatin blends with novel pH‐dependence

A novel change of phase behavior and properties of polyvinyl alcohol (PVA)/gelatin blends as a function of pH was reported. The PVA/gelatin blends were found to be completely miscible in acidic condition (pH < 4), partially miscible in basic condition (pH > 8), and immiscible in neutral condition (pH was ca. 6). As a result, the membranes cast from acidic condition showed the highest tensile strength and the lowest alcohol vapor permeation (AVP) rate; those obtained from neutral condition showed the lowest tensile strength and highest AVP rate; the properties of membranes cast from basic condition lay in between. The interaction between PVA and gelatin was investigated via Fourier transform infrared spectrum (FTIR), differential scanning calorimetry (DSC), and Zetasizer measurement. The novel pH‐dependence of the blends was ascribed to the protonation of amino groups of gelatin in acidic condition, which resulted in a strong electrostatic attraction between ? NH of gelatin and ? OH of PVA. The partial miscibility in basic condition was due to the ionization of carboxyl groups of gelatin, which caused a stretching of gelatin via electrostatic repulsive force and a breakage of the H‐bonding among the molecular chains, leading to a limited interaction between PVA and gelatin and forming a partially miscible blend. In neutral conditions, there were almost no charges (very limited protonation and ionization) at the weak polyampholyte gelatin, and the strong H‐bonding among gelatin molecules themselves or PVA molecules themselves caused the phase separation between gelatin and PVA. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 239–247, 2009     

Keratin-Based Composite Bioactive Films and Their Preservative Effects on Cherry Tomato

In this study, keratins were extracted from pig nail waste through the reduction method using L-cysteine as a reductant. Curcumin was successively incorporated in a mixed solution including keratin, gelatin, and glycerin to prepare different kinds of keratin/gelatin/glycerin/curcumin composite films. The morphology of the keratin/ gelatin/glycerin/curcumin composite films were examined using scanning electron microscopy. The structures and the molecular interactions between curcumin, keratin, and pectin were examined using Fourier transform infrared spectroscopy and X-ray diffraction, and the thermal properties were determined through thermogravimetric analysis. The tensile strengths of keratin/gelatin/glycerin/curcumin and keratin/gelatin/curcumin composite films are 13.73 and 12.45 MPa, respectively, and their respective elongations at break are 56.7% and 4.6%. In addition, compared with the control group (no film wrapped on the surface of tomato), the ratio of weight loss of the keratin (7.0%)/gelatin (10%)/glycerin (2.0%)/curcumin (1.0%) experimental groups is 8.76 ± 0.2%, and the hardness value of the tomatoes wrapped with composite films is 11.2 ± 0.39 kg/cm³. Finally, the composite films have a superior antibacterial effect against Staphylococcus aureus and Escherichia coli because of the addition of curcumin. As the concentration of curcumin reaches 1.0%, the antibacterial activity effect of the film is significantly improved. The diameter of the inhibition zone of E. coli is (12.16 ± 0.53) mm, and that of S. aureus is (14.532 ± 0.97) mm. The multifunctional keratin/gelatin/glycerin/curcumin bioactive films have great potential application in the food packaging industry.