The ability of different hydrophilic polymers to improve compression behavior of metformin hydrochloride after co-spray drying from aqueous solutions was investigated. Spray dried products were ...evaluated by laser diffraction, light microscopy with image analysis, SEM, PXRD, DSC, instrumented press and diametrical loading of compacts. The obtained powders consisted of agglomerated spherical particles with median diameters between 6.7 and 11.0μm, and were able to compress after mixing with 7% process aids. Compared with the spray dried drug alone, co-spray drying with polymers resulted in increase of amorphous content (from 0.5 to between 2.0 and 15.6%) associated with increased deformability/interparticle bonding and reduced ejectability. Importance of amorphous content on particle bonding and deformation was confirmed by significant correlation between compaction work and relative crystallinity (p=0.042). Compactability and tabletability were improved considerably by co-spray drying with the anionic polymers (sodium alginate and sodium carboxymethylcellulose), while decreased by co-spray drying with PVP and copovidone compared to spray dried drug alone. On the other hand, ejectability was less compromised by co-spray drying with copovidone and HPMC. By using overall desirability scores the polymers were ranked for efficiency in the order: sodium alginate>HPMC>sodium carboxymethylcellulose>copovidone>PVP. The plot of tensile strength vs the ratio work of compaction/(elastic recovery%×yield pressure) was a straight line (r=0.814) allowing prediction of tensile strength from in-die measured parameters.
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•Metformin HCl co-spray dried with polymers exhibited reduced crystallinity.•Composite particles were directly-compressible after mixing with 7% process aids.•The anionic Na alginate and Na CMC enhanced compactability of metformin HCl.
To solve the problem that waste oil residues cannot be utilized and to reuse the aged asphalt, suitable modifiers were selected to compound the aged asphalt with waste oil residues to study its ...performance. SBS/REOB modified-rejuvenated asphalt was prepared by a high-speed shearing mechanism with aged asphalt, Recycled Engine Oil Bottom (REOB), Styrenic Block Copolymers (SBS) modifier, and stabilizer. The effects of SBS content, REOB content, shear time, and shear rate on the conventional physical properties of asphalt were studied by orthogonal grey correlation analysis, and the optimum preparation scheme of SBS/REOB modified-rejuvenated asphalt was determined. The high and low temperature rheological properties of SBS/REOB modified-rejuvenated asphalt were studied using the Multiple Stress Creep Recover (MSCR) test and bending beam rheological (BBR) test. The mechanism of SBS/REOB on the modification and regeneration of aged asphalt was explored through four component tests and Fourier transforms infrared spectroscopy. The results show that the optimum preparation scheme is 4.5% SBS dosage, 9% REOB dosage, 50~60 min shear time, and 4500 r/min shear rate. The addition of SBS improves the elastic recovery performance and high temperature deformation resistance of REOB rejuvenated asphalt. At the same time, the S-value decreases and the m-value increases, which significantly improves the low temperature cracking resistance of REOB rejuvenated asphalt. The addition of REOB achieves component blending and regeneration of aged asphalt by supplementing the light components. After the addition of SBS absorbs the light component and swelling reaction occurs, the whole modification-regeneration process is mainly physical co-mixing and co-compatibility.
Debris flows often cause local damage to engineering structures by exerting destructive impact forces. The debris-flow–deformable-barrier interaction is a significant issue in engineering design. In ...this study, a large physical flume model test device was independently designed to repeatedly reproduce the flow and impact process of debris flow. Three physical flume tests were performed to investigate the effect of barrier stiffness on the debris flow impact. The flow kinematics of debris flow with three barrier stiffness values are essentially consistent with the process of impact–run-up–falling–pile-up. The development of a dead zone provided a cushion to diminish the impact of the follow-up debris flow on the barrier. The peak impact forces were attenuated as the barrier stiffness decreased. The slight deflections of a deformable barrier were sufficiently effective for peak load attenuation by up to 30%. It showed that the decrease of the barrier stiffness had a buffer effect on the debris flow impact and attenuated the peak impact force. And with the decrease of the barrier stiffness, when the barrier was impacted by the same soil types, the recoverable elastic strain will be larger, and the strain peak will be more obvious.
Disposable medical gloves (DMGs) have long been used to mitigate the risk of direct exposure to diverse microorganisms and body fluids; hence, they are a critical weapon to protect patients and ...healthcare staff from infectious diseases. Measures to control the spread of COVID-19 have sparked the production of an excessive number of DMGs, most of which are eventually being disposed of in landfills. Untreated DMGs in landfills do not only pose a direct risk of transmitting coronavirus and other pathological germs but also pollute air, water, and soil dramatically. As a healthier alternative, recycling discarded polymer-rich DMGs into bitumen modification is considered to be a prospective waste management strategy applicable to the asphalt pavement industry. In this study, this conjecture is tested by examining two common DMGs — latex gloves and vinyl gloves — at four different percentages (1%, 2%, 3%, and 4% by weight). The morphological characteristics of DMG-modified specimens were inspected by using a high-definition scanning electron microscope (SEM) equipped with an energy dispersive X-ray analyzer (EDX). A wide range of laboratory tests including penetration, softening point temperature, ductility, and elastic recovery were undertaken to evaluate the impact of waste gloves on the conventional engineering properties of bitumen. Moreover, viscoelastic behavior and modification processing were studied by conducting the dynamic shear rheometer (DSR) test and the Fourier transform infrared spectroscopy (FTIR) analysis. Test results have revealed the outstanding potential of recycled DMG waste for modifying neat asphalt binder. More specifically, bitumens modified with 4% latex glove and 3% vinyl glove were seen as capable of superiorly withstanding permanent deformations caused by heavy axle loads at high service temperatures. Furthermore, it has been shown that 1.2 tons of modified binder would embed approximately 4000 pairs of recycled DMGs. This study shows that DMG waste can be used as a viable modifier, which would help open a new avenue for mitigating the environmental pollution arising from the COVID-19 pandemic.
Graphical Abstract
We report nitrogen-induced enhanced electron tunnel transport and improved nanomechanical properties in band gap-modulated nitrogen doped DLC (N-DLC) quantum superlattice (QSL) structures. The ...electrical characteristics of such superlattice devices revealed negative differential resistance (NDR) behavior. The interpretation of these measurements is supported by 1D tight binding calculations of disordered superlattice structures (chains), which include bond alternation in sp3-hybridized regions. Tandem theoretical and experimental analysis shows improved tunnel transport, which can be ascribed to nitrogen-driven structural modification of the N-DLC QSL structures, especially the increased sp2 clustering that provides additional conduction paths throughout the network. The introduction of nitrogen also improved the nanomechanical properties, resulting in enhanced elastic recovery, hardness, and elastic modulus, which is unusual but is most likely due to the onset of cross-linking of the network. Moreover, the materials’ stress of N-DLC QSL structures was reduced with the nitrogen doping. In general, the combination of enhanced electron tunnel transport and nanomechanical properties in N-DLC QSL structures/devices can open a platform for the development of a new class of cost-effective and mechanically robust advanced electronic devices for a wide range of applications.
This study aims to formulate experimental vinylpolysiloxane (VPS) impression materials and compare their elastic recovery and strain-in-compressions with three commercial VPS materials (Aquasil, ...Elite, and Extrude). Five experimental materials (Exp), two hydrophobic (Exp-I and II) and three hydrophilic (Exp-III, IV and V) were developed. Exp 1 contained vinyl-terminated poly-dimethyl siloxane and a conventional cross-linking agent (poly methylhydrosiloxane), while Exp- II contained a novel cross-linking agent that is tetra-functional dimethyl-silyl-ortho-silicate (TFDMSOS). Exp III-V (hydrophilic materials) were formulated by incorporating different concentrations of non-ionic surfactant (Rhodasurf CET-2) into Exp II formulation. Measurement of elastic recovery and strain-in-compression for commercial and experimental materials were performed according to ISO4823 standard using the calibrated mechanical testing machine (Tinius Olsen). One-way analysis of variance (one-way ANOVA) and Tukey's
(HSD) test were used for statistical analysis and a
-value of ≤ 0.05 was considered significant. Exp-I has statistically similar values to commercial VPS. The Exp-II showed the highest elastic recovery, while % elastic recovery was reduced with the addition of the non-ionic surfactant (Rhodasurf CET-2). The % reduction was directly related to the concentration of Rhodasurf CET-2. In addition, Exp II had significantly higher strain-in-compression values compared to Exp-I and commercial materials. These values were further increased with the addition of a non-ionic surfactant (Rhodasurf CET-2) was added (Exp-III, IV and V).
Springback Reduction by Using Tool Rollers Nikhare, Chetan P.
International journal of precision engineering and manufacturing,
2020/1, Letnik:
21, Številka:
1
Journal Article
Recenzirano
Springback is defined as a geometric defect, which occurs due to elastic recovery in the part after it has been unloaded. This challenge is most common in lightweight alloys as well as in advanced ...high strength steels. The materials, which exhibit lower elastic modulus or higher tensile strength, would be more prone to springback. In this paper, a novel patented technique is introduced to eliminate the springback by using rollers in the forming tool. It was found that due to the rotation of rollers in the tool during forming, reduces the stress in the part and, thus reduces the springback.
Crosslinking plays a crucial role in determining mechanical properties of polymer materials. Although various crosslinks based on covalent or noncovalent bonds have been adopted, it remains an ...enormous challenge to develop a crosslink which could endow corresponding polymer network with robust yet dynamic properties. Herein, we report a crosslink simultaneously having dynamic property and woven geometry, and the polymer network with woven crosslinks (WPN) could integrate the merits of covalent polymer network (CPN) and supramolecular polymer network (SPN). In specific, the WPN not only exhibits comparable stiffness, strength, elastic recovery, and anti‐fatigue property to those of CPN, but also possesses decent mechanical adaptivity and ductility, similar to those of SPN. Particularly, its toughness and puncture resistance are much superior to those of the others. Besides, the dynamicity of woven crosslink also imparts good performances of self‐healing and processability to WPN.
Woven nodes, serving as dynamic crosslinks, afford a woven polymer network (WPN). The WPN exhibits comparable stiffness, strength, elastic recovery, and anti‐fatigue properties to those of covalent polymer networks (CPN), but also possesses decent mechanical adaptivity, self‐healing, and reprocessability, resembling those of supramolecular polymer networks (SPN).
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