Effects of plasticizers on the properties of oat starch films

Oat starch films were prepared by casting using glycerol, sorbitol, glycerol–sorbitol mixture, urea and sucrose as plasticizers. The effects of these plasticizers on the microstructure, moisture sorption, water vapor permeability (WVP) and mechanical properties were investigated using films stored under a range of relative humidities. The plasticizer type did not affect significantly (p ≤ 0.05) the equilibrium moisture content of films, except at 90% relative humidity (RH). Films without plasticizer adsorbed less water and showed higher WVP than plasticized ones, indicating the antiplasticizing effect observed in this work. In general, a decrease in stress at break and Young's modulus and an increase in strain at break were observed when RH increased in all film formulations. Films without plasticizer showed higher stress at break values than the plasticized ones and presented stable strain at break under a range of RH. Sucrose films were the most fragile at low RH while glycerol films were the most hygroscopic.     

Thermoplastic starch/polyester films: Effects of extrusion process and poly (lactic acid) addition

Biodegradable films were produced using the blown extrusion method from blends that contained cassava thermoplastic starch (TPS), poly(butylene adipate-co-terephthalate) (PBAT) and poly(lactic acid) (PLA) with two different extrusion processes. The choice of extrusion process did not have a significant effect on the mechanical properties, water vapor permeability (WVP) or viscoelasticity of the films, but the addition of PLA decreased the elongation, blow-up ratio (BUR) and opacity and increased the elastic modulus, tensile strength and viscoelastic parameters of the films. The films with 20% PLA exhibited a lower WVP due to the hydrophobic nature of this polymer. Morphological analyses revealed the incompatibility between the polymers used.     

Highly conducting graphene sheets and Langmuir-Blodgett films

Graphene is an intriguing material with properties that are distinct from those of other graphitic systems. The first samples of pristine graphene were obtained by 'peeling off' and epitaxial growth. Recently, the chemical reduction of graphite oxide was used to produce covalently functionalized single-layer graphene oxide. However, chemical approaches for the large-scale production of highly conducting graphene sheets remain elusive. Here, we report that the exfoliation-reintercalation-expansion of graphite can produce high-quality single-layer graphene sheets stably suspended in organic solvents. The graphene sheets exhibit high electrical conductance at room and cryogenic temperatures. Large amounts of graphene sheets in organic solvents are made into large transparent conducting films by Langmuir-Blodgett assembly in a layer-by-layer manner. The chemically derived, high-quality graphene sheets could lead to future scalable graphene devices.     

Effects of oxidizing gases on semiconductivity and thermal stability of phthalocyanine thin films

The effects of oxidizing gases (O₂ and NO₂) on the p-type semiconductivity of the phthalocyanines H₂Pc, PbPc, ZnPc, CuPc, AlPcCl, AlPc-O-AlPc and (AlPc) _n films treated in nitrogen at 350 ° C have been examined. The conductance increased in the presence of oxidizing gases. Reversible effects of oxidizing gases on the conductance were observed for PbPc, CuPc and ZnPc, all of which are thermally and/or chemically less stable than the other Pcs. For the latter, the conductance in nitrogen increased permanently after exposure to NO₂. The reversibility of the former may be related to the thermal and chemical stability of neutral and/or oxidized phthalocyanines. The conductivity is described byG =G ₀ exp (E/kT) The activation energy,E, decreased in the presence of oxidizing gases. The pre-exponential factor,G ₀, was lowered by the introduction of NO₂ especially for PbPc, CuPc and ZnPc. It seems that the adsorption of NO₂ is limited to the surface of fine crystals and the increase in the conductance caused by exposure to NO₂ is strongly influenced by the crystallinity of phthalocyanine.     

Linear stability of non-Newtonian annular liquid sheets

Summary This paper reports a linear stability analysis of a non-Newtonian annular liquid sheet that is surrounded by nonviscous fluids in relative axial motion to it. It is shown that for a stress free basic flow the dispersion relation giving the absolute and convective instability mechanisms can be immediately obtained from the dispersion relation for a Newtonian sheet by introducing a wavenumber dependent viscosity. The stability behavior of the sheet is investigated numerically by a continuation algorithm, by which the solution branches of the dispersion relation, relevant for the stability information, can be traced. The results give a stability picture which covers the whole range of annular sheets from the cylindrical jet to the plane liquid curtain.     

Effects of feedstocks on the process integration of biohydrogen production

Future production of hydrogen must be sustainable. To obtain it, renewable resources have to be employed for its production. Fermentation of biomasses could be a viable way. The process evaluated is a two-step fermentation to produce hydrogen from biomass. Process options with barley straws, PSP, and thick juice as feedstocks have been compared on the basis of process balances. Aspen Plus has been used to calculate mass and energy balances taking into account the integration of the process. Results show that the production of hydrogen as energy carrier is technically feasible with all the considered feedstocks and thanks to heat integration, second generation biomass (PSP and barley straws) are competitive with food crops (thick juice).     

Effects of process parameters on the quality aspects of weld-bead in laser welding of NiTinol sheets

The effects of process variables, like scan speed and laser power, on the quality of bead-on-plate welding of NiTinol sheets were investigated. The measured quality aspects for the weld-bead profile were bead geometry, changes in microstructure, variation of microhardness value along the weld-bead, extent of oxide contamination during welding, Ti/Ni ratio after welding, changes in tensile strength of the welded samples and corrosion behavior of the welded and parent materials. The laser weld-bead profile changed from the shape of a stemless wineglass to that with a prominent leg. Dimensional aspects of weld-bead geometry showed a decreasing trend with increasing scan speed. However, an increasing trend of the same was observed with power. The Ti/Ni ratio on the top surface after welding was found to decrease with scan speed at a particular power. Oxide contamination during welding followed the same pattern of variation as that of the Ti/Ni ratio. Microhardness values gradually increased from the weld centerline to the base metal. Formation of brittle intermetallic compounds reduced the tensile strength of the material after welding. A dual failure mode for the welded sample was observed, whereas a single mode of failure was detected for the parent material. The corrosion properties of the welded samples were better than that of the parent material.     

Effects of distortional components in biaxial stretching of poly (ethylene terephthalate) sheets on dimensional stability and structure

Thin sheets of poly (ethylene terephthalate) were stretched biaxially over a wide range to temperatures below the melting point of the polymer. The linear shrinkage occurring at temperatures between 85 and 100 °C decreased with increasing draw temperature and draw ratio. Specimens taken near the edges of the drawn sheets, which had been subjected to in-plane shear deformations, were found to exhibit linear shrinkage 5–8 times lower than those taken from the middle of the sheet. Subsequent experiments, using purpose-built clamps to achieve a more uniform state of shear in both directions of the biaxially drawn samples, confirmed the universality of the principle of shrinkage suppression by the superposition of shear deformations. X-ray diffraction studies revealed that the phenomenon was not related to differences in type of orientation of the crystals. The information from the X-ray diffraction studies and data from thermal analysis have led to the conclusion that the enhanced dimensional stability of biaxially drawn sheets subjected to superimposed shear deformations results from a combination of a higher rate of stress-induced crystallization and a reduction in the level of orientation within the amorphous phase.     

溅射工艺对LaNiO3薄膜结构和电性能的影响

采用射频磁控溅射法在Si(100)衬底上制备了LaNiO3薄膜.通过后续热处理使薄膜晶化,并用四探针法测量了薄膜的表面电阻率.借助X射线衍射分析、电感耦合等离子体发射光谱、原子力显微镜等手段研究了溅射工艺及热处理温度对薄膜显微结构的影响.实验结果表明,在氧气氛保护下,于550℃处理1h,薄膜晶化.溅射氧分压在10%～25%之间,700℃热处理时可以得到表面光滑致密且电性能较好的薄膜.     

Chitosan/poly (vinyl alcohol) films containing ZnO nanoparticles and plasticizers

In this study ZnO nanoparticles were prepared by the Pechini method from a polyester by reacting citric acid with ethylene glycol in which the metal ions are dissolved, and incorporated into blend films of chitosan (CS) and poly (vinyl alcohol) (PVA) with different concentrations of polyoxyethylene sorbitan monooleate, Tween 80 (T80). These films were characterized by infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), swelling degree, degradation of films in Hank's solution and the mechanical properties. Besides these characterizations, the antibacterial activity of the films was tested, and the films containing ZnO nanoparticles showed antibacterial activity toward the bacterial species Staphylococcus aureus. The observed antibacterial activity in the composite films prepared in this work suggests that they may be used as hydrophilic wound and burn dressings.     

工艺参数对磁控溅射金属化薄膜性能的影响

溅射金属化技术不仅环保,而且工艺过程简单,金属化质量高,将成为未来金属化工艺的主要发展方向.本文采用真空溅射技术在镍锌铁氧体表面制备了Cr(150 nm)/Ni-Cu(460 am)/Ag(200 nm)结构的金属化复合薄膜,从理论和实验上研究分析了溅射工艺参数对于薄膜性能的影响.研究表明:当溅射功率密度为20 W·cm-2,靶片间距8 cm,溅射气压0.5 Pa时,结合性能和高温可焊接性能最好,可达6.19 Mpa和100%,成膜速率也比较理想.     

Exponential growth of LBL films with incorporated inorganic sheets

The fastest growth pattern of layer-by-layer (LBL) assembled films is exponential LBL (e-LBL), which has both fundamental and practical importance. It is associated with "in-and-out" diffusion of flexible polymers and thus was considered to be impossible for films containing clay sheets with strong barrier function, preventing diffusion. Here, we demonstrate that e-LBL for inorganic sheets is possible in a complex tricomponent film of poly(ethyleneimine) (PEI), poly(acrylic acid) (PAA), and Na(+)-montmorillonite (MTM). This system displayed clear e-LBL patterns in terms of both initial accumulation of materials and unusually thick individual bilayers later in the deposition process with film thicknesses reaching 200 microm for films composed of 200 pairs of layers. Successful incorporation of MTM layers was observed by scanning electron microscopy and thermo-gravimetric analysis. Surprisingly, the growth rate was found to be nearly identical in films with and without clay layers, which suggests fast permeation/reptation of polyelectrolytes between the nanosheets during the "in-and-out" diffusion of polymer. In considering these findings, e-LBL growth property is expected for a wide array of available inorganic nanoscale components and have a potential to greatly expand the e-LBL field and LBL field altogether. The large thickness and rapid growth of the films affords fast preparation of nanostructured materials which is essential for multiple practical applications ranging from optical devices to ultrastrong composites.     

Influence of plasticizers and drugs on the physical-mechanical properties of hydroxypropylcellulose films prepared by hot melt extrusion

Hydroxypropylcellulose (HPC) films containing drugs or hydrophilic or hydrophobic plasticizers were prepared by a hot melt extrusion process. Polyethylene glycol 8000 (PEG 8000) 2%, triethyl citrate (TEC) 2%, acetyltributyl citrate (ATBC) 2%, and polyethylene glycol 400 (PEG 400) 1% were the plasticizing agents studied. In addition, either hydrocortisone (HC) 1% or chlorpheniramine maleate (CPM) 1% was incorporated into the films as a model drug. The physical-mechanical properties of the films that were investigated included tensile strength (TS), percentage elongation (%E), and Young's modulus (YM). Differential scanning calorimetry (DSC) was utilized to determine glass transition temperatures (T_g' s). These parameters were studied as a function of time and temperature. The glass transition temperatures initially decreased with the inclusion of the drugs and plasticizers. However, after 6 months aging, films containing PEG 400 and HC showed a marked increase in T_g. The films containing PEG 400 showed physical-mechanical instability in all parameters studied. All extruded films exhibited a marked decrease in TS in contrast to a large increase in %E when testing was performed perpendicular to flow versus in the direction of flow. In addition, a consistent film of HPC in the absence of drugs or plasticizers could not be extruded due to the excessive stress on the equipment. Although the theoretical percentage of CPM on aging remained fairly constant over the processing temperature ranges in this study, the HC levels remaining in the extruded films during storage were a function of time and temperature.     

淀粉/PVA复合膜的制备及血液相容性

在无化学处理的条件下制备出淀粉/聚乙烯醇(PVA)复合膜, 进行了力学性能、 溶胀度及红外光谱测试, 并通过溶血试验、 动态凝血试验、 血小板消耗试验对复合膜的血液相容性进行了表征。研究结果表明, 通过共混改性把淀粉引入到PVA中, 改善了力学性能和血液相容性。当PVA与淀粉的质量比为4∶1时, 复合膜的抗拉强度为13.73 MPa, 抗拉应变率为43.07%, 性能最佳。      

6016与H70板的冲压变形连接过程及剥离强度分析

对6016与H70板的冲压变形连接和剥离过程进行了物理实验和连续数值模拟,分析了不同模具与工艺参数对连接点颈部厚度、互锁及金属流动的影响.研究表明:随着凸模圆角半径(Rp)增大,颈厚值(Tn)增大,互锁值(Tu)减小;凹模深度(Hd)增大,Tn减小、Tu增加.底部厚度X取决于凸模下压量,过大底部材料流动不到位影响互锁,过小则底部太薄,推荐X取总板厚的25%.采用L型试样测剥离抗拉强度时应考虑加载力臂的影响.利用数值模拟可以预测连接强度,并为工艺与模具设计提供有效指导.     

The stability of insulin in solid formulations containing melezitose and starch. Effects of processing and excipients

Solid insulin formulations obtained by different methods of preparation were compared with respect to chemical stability and morphology. Spray- and freeze-drying, solution enhanced dispersion by supercritical fluids (SEDS) and precipitation into starch microspheres were the methods used for preparation of solid powders. The excipients applied were melezitose, starch, and sodium taurocholate. The stability of the samples was evaluated after storage in open containers at 25°C and 30% RH for 6 months.

All samples were amorphous after processing and storage as detected by XRD, except for the starch microspheres which were semi-crystalline. The spray- and freeze-dried samples containing melezitose and sodium taurocholate experienced a significant water uptake during storage, resulting in changes in morphology and disappearance of Tg. However, the chemical stability of these samples did not seem to be affected by the water uptake. Changes in morphology were not observed for the SEDS powders and the starch microspheres.

The chemical stability of the samples was assessed by HPLC. In general, conventional spray- and freeze drying resulted in samples with higher chemical stability compared to SEDS powders and starch microspheres. Nevertheless, the excipients applied were observed to be of major importance, and further optimization of the formulation as well as processing conditions may lead to slightly different conclusions.     

Effect of process parameters on electromagnetic impact welding of aluminum sheets

Electromagnetic forming of aluminum sheets has been studied in detail by many researchers due to its advantages of increased formability and reduced springback. The feasibility of electromagnetic impact welding of aluminum sheets has been established, but the effect of process parameters on the weld strength has not been reported. The present study investigates the effect of parameters such as energy, standoff distance and coil geometry on the shearing strength and the width of the weld achieved by electromagnetic impact welding of aluminum sheets. A study has been carried out to characterize the effectiveness of the process of welding two aluminum sheets of same chemical composition and of 1 mm thickness. The results of the microstructure and shearing strength tests are reported in this paper. The shearing strength and the width of the weld are found to increase with an increase in discharge energy. Further, when the geometry of the coil is changed from rectangular shape to tapered shape, it gives higher shearing strength. The standoff distance has an optimum value that gives maximum shearing strength and width of the weld. If the standoff distance is varied on either side of its optimum value the shearing strength and the width of the weld reduce.     

A dry process for production of microfluidic devices based on the lamination of laser-printed polyester films

A new microfabrication process based on a xerographic process is described. A laser printer is used to selectively deposit toner on a polyester film, which is subsequently laminated against another polyester film. The toner layer binds the two polyester films and allows the blank regions to become channels for microfluidics. These software-outlined channels are approximately 6 microm deep. Approximately twice this depth is obtained by laminating two printed films. The resulting devices were not significantly damaged after 24 h of exposure to aqueous solutions of H3PO4, NaOH, methanol, acetonitrile, or sodium dodecyl sulfate. Electric tests with an impedance analyzer and microchannels filled with KCl solution demonstrated that (1) wide channels suffer from deformation of the top and bottom walls due to the lamination of the polyester films and (2) the toner walls are somewhat porous. Although these drawbacks limit the maximum width of a channel and the minimum distance between two channels, the process is an attractive option to other expensive, laborious, and time-consuming methods for microchannels fabrication. The process has been used to implement devices for electrospray tip and capillary electrophoresis with contactless conductivity detection.     

Leaching of water-soluble plasticizers from polymeric films prepared from aqueous colloidal polymer dispersions

Abstract

The leaching of water-soluble plasticizers from polymeric films prepared by casting and drying of plasticized colloidal polymer dispersions was investigated with respect to the type and concentration of plasticizer (triethyl citrate or triacetin), film thickness, type of colloidal polymer dispersions (acrylic: Eudragit RS30D, RL30D, or L30D; cellulosic: Aquacoat), Eudragit RS30D/RL30D ratio, and method of film preparation (solvent- or pseudolatex-casting). The leaching increased with increasing level of plasticizer as indicated by an increase in the release rate constant while the release rate constant was independent of the film thickness. The leaching was more rapid from Aquacoat films than from Eudragit RS30D films at all plasticizer concentrations. Increasing the amount of the more hydrophilic polymer dispersion, Eudragit RL30D, in mixed Eudragit RS/RL films increased the rate of leaching. The incorporation of propranolol HCl into the polymeric films significantly increased the leaching rate constant when compared to drug-free films. The leaching from pseudolatex-cast films was faster when compared to the leaching from solvent-cast films due to the denser structure of the solvent-cast films.     

Leaching of water-soluble plasticizers from polymeric films prepared from aqueous colloidal polymer dispersions

The leaching of water-soluble plasticizers from polymeric films prepared by casting and drying of plasticized colloidal polymer dispersions was investigated with respect to the type and concentration of plasticizer (triethyl citrate or triacetin), film thickness, type of colloidal polymer dispersions (acrylic: Eudragit RS30D, RL30D, or L30D; cellulosic: Aquacoat), Eudragit RS30D/RL30D ratio, and method of film preparation (solvent- or pseudolatex-casting). The leaching increased with increasing level of plasticizer as indicated by an increase in the release rate constant while the release rate constant was independent of the film thickness. The leaching was more rapid from Aquacoat films than from Eudragit RS30D films at all plasticizer concentrations. Increasing the amount of the more hydrophilic polymer dispersion, Eudragit RL30D, in mixed Eudragit RS/RL films increased the rate of leaching. The incorporation of propranolol HCl into the polymeric films significantly increased the leaching rate constant when compared to drug-free films. The leaching from pseudolatex-cast films was faster when compared to the leaching from solvent-cast films due to the denser structure of the solvent-cast films.