Band 39, Heft 9

The present work reveals pyrolysis kinetics of polypropylene (PP) over zeolite modernite using thermogravimetry. The activation energy ( E a ) and frequency factor ( A ) were calculated applying Ozawa Flynn Wall, Coats-Redfern, and Tang Wanjun methods. The E a calculated by all the methods were found in accord with each other. The pyrolysis was also performed in a salt bath in the temperature range 350°C–390°C. It was observed that a temperature of 370°C is the optimum temperature for maximum liquid fuel production. Moreover, the amount of solid residue decreases with the rise in temperature. Similarly, gas fraction also shows linear relationship with temperature. The condensable and noncondensable fractions were collected and analyzed by gas chromatography-mass spectrometry. The fuel properties of the oil produced were assessed and compared with commercial fuel. These properties agree well with fossil fuel and therefore have potential applications as fuel.

New formulations of cellulose acetate (CA) membrane with graphene (G)/graphene oxide (GO) are suggested and investigated in the present work. This study is intended to find a wide range of conditions for fabricating CA membranes in the presence of some additions of graphene (G), and graphene oxide (GO). The membrane is prepared by phase inversion process. Microscopic investigations for graphene (G), graphene oxide (GO), and prepared membrane were performed by high-resolution transmission electron microscope (HRTEM) and scanning electron microscopy (SEM). The mechanical properties of prepared membranes are determined and evaluated. Permeation tests were performed using natural seawater and simulated seawater to check the prepared membrane performance. The results presented that the permeate flux of M 25% CA membranes containing 0.01 wt.% G is the highest flux (57–74 l/m 2 h) compared with the neat CA membrane, and the 0.01 wt.% GO-based membranes, while the GO-based membranes were comparable as the neat CA membrane at operating pressures (30–35 bar) and with a feed of 35 g/l NaCl solution. The results showed a remarkable salt rejection of simulated seawater of 95%, and natural seawater with a feed from the Mediterranean Sea displayed 90% salt rejection and accepted pure water flux as well.

Friction measurements have been carried out to characterize surface damages during photodegradation of low-density polyethylene. The average and mean deviation of the friction coefficients increase with the irradiation time in the early stage of photodegradation processes, indicating the increase in the surface roughness, whereas the mechanical properties remain essentially unchanged. In the following stage, where the ductile-brittle transition takes place, the mean deviation of the friction coefficients shows an appreciable decrease with maintaining almost constant average values, suggesting that the surface becomes more homogeneous. Beyond the ductile-brittle transition, both of the average and mean deviation of the friction coefficients gradually increase with the irradiation time, indicating further enhancement of surface roughness, followed by formation of surface cracks. The soundness of the friction measurements is confirmed by comparing with optical measurements of the surface roughness, and it is suggested that the present method gives a convenient and sensitive method of detection for degradation in polymeric materials.

The objective of this study is to investigate the electrically conductive properties and percolation thresholds of carbon black (CB)-filled polypropylene (PP)/glass fiber (GF), PP/polyamide 6 (PA6), and PP/PA6/GF composites. Compared to CB-filled PP/GF and PP/PA6 composites, PP/PA6/GF/CB composites exhibited a reduction of the percolation threshold. Under the same CB loading, the surface resistivity of PP/PA6/GF/CB composites was much lower, indicating a better conductivity. According to the morphology images characterized by transmission electron microscopy, CB was preferentially located in the PA6 phase due to the good interaction between CB and PA6 and the lower viscosity of PA6. The addition of GF formed a PA6-coated GF structure. This structure with a relatively long diameter can effectively assist the construction of conductive paths. Meanwhile, GF also played a volume-occupying role and improved the effective concentration of the conductive component in the system. The influences of GF and PA6 mass fraction on the surface resistivity of PP/PA6/GF/CB composites were also explored, respectively. It was found that appropriate amounts of GF and PA6 could effectively increase the electrical conductivity, providing guidance for fabricating an antistatic or conductive material with high comprehensive performance.

The aim of the study was to prepare lansoprazole (LNS)-loaded poly( d,l -lactide- co -glycolide) (PLGA) nanoparticles in order to improve the physicochemical stability associated with LNS. We synthesized LNS-loaded PLGA nanoparticles in the presence of magnesium oxide as alkalizer to improve the release of LNS and stability against photodegradation. The LNS-encapsulated PLGA nanoparticles were developed by the nanoprecipitation/solvent evaporation method, resulting in a particle size of 246.7 ± 3.4 nm, polydispersity index (PDI) of 0.126, percent drug entrapment (PDE) of 82.85 ± 4.5%, percent drug loading (PDL) of 3.54 ± 0.34%, and pH of 8.10 ± 0.56. The developed nanoparticles were further evaluated for in vitro release and resistance to photodegradation by NMR spectroscopy and LC-MS. The sustained release of the drug was confirmed after the encapsulation of LNS in the PLGA matrix. The protection of LNS in the PLGA matrix against photodegradation was confirmed by NMR and LC-MS studies. The LC-MS of UV-exposed samples of pure LNS and LNS-loaded PLGA nanoparticles at 254 nm showed the same (M + 1) peak at 370 m/e , and the base peak at 369 m/e accounted for the unchanged structure of LNS inside PLGA nanoparticles. Overall, it was proved that PLGA nanoparticles in the presence of magnesium oxide are an efficient carrier to deliver and protect LNS from physicochemical instability.

A limiting factor for industrial usage of laser-sintered parts is the high surface roughness due to the semi-molten or attaching powder particles resulting from tool and pressureless manufacturing. An approach to improve the surface quality is the postprocessing with acids to smoothen the surface as it enables improvement without geometrical restrictions of the parts. The present work deals with the usage of nitric, hydrochloric, and trifluoroacetic acids, and exhibits the influence on the resulting surface morphology, dimensional accuracy, and the mechanical properties. The results exhibit different interaction mechanics and show great differences in the resulting part properties.

An innovative sandwich battery composite was designed and manufactured by applying he vacuum assisted hand lay-up molding process. A series of bending mechanical properties and electrical performance testing were performed to investigate the reliability of the structure-battery composites. Experimental results showed that embedding the lithium polymer cell had no influence on the specific strength of the composite components and the electrical properties of the battery packs. Moreover, the charging and discharging properties of the structure-battery composites were not affected when subjected to 60% of failure load level or less. Under 80% of failure load, the charging and discharging capacities of the battery were reduced by 21.80% and 22.78%, respectively, and this degradation was unrecoverable. The structure-battery system has great potential as a multifunctional composite to optimize structural design and improve lightweight integrated properties.

In the present study, an improved consolidation model, with mold inertia included, is proposed to completely predict how the upper mold rapidly moves from rest to maximal velocity and then decelerates to a steady value for a constant force-controlled compression resin transfer molding (CRTM). Simulation results show that all preform compaction cases cannot apply to quasi-static consolidation theory in CRTM. For cases with a massy mold, inadequate preform resistance, and low resin viscosity, the mold inertia has a short, remarkable influence on the resin counter-force and causes a slightly slow resin progression in the early compression stage. Contrarily, the compaction of the rigid preform is applicable to the quasi-static consolidation theory. Additionally, a reasonable time increment is discussed for using the quasi steady-state approximation.

A mathematical study of an Oldroyd 4-constant fluid for a blade coating process is studied in this paper. The results for plane as well as exponential coaters are analyzed. Suitable dimensionless variables are used to convert the model governing equations into dimensionless form. Lubrication approximation theory is applied to simplify the dimensionless form of governing partial differential equations. The well-known numerical technique known as the shooting method is used to solve the non-linear boundary value problem. Influence of the involved rheological parameters on the blade coating process is analyzed. From an engineering point of view, load on the blade and pressure are important outcomes of the present study as they ensure the thickness and quality of coating and enhance the life of the substrate. The effects of material parameters on load, thickness, velocity, pressure and pressure gradient are discussed. Obtained results for velocity, pressure gradient and pressure distribution are shown graphically, whereas load and thickness are expressed in a tabulated form.