Influence Of Melt Processing Research Articles

Comment on “Wetting of liquid copper on TC4 titanium alloy and 304 stainless-steel at 1273–1433 K” Materials & design 169 (2019) 107667

In the present paper a few comments on the paper “Wetting of liquid copper on TC4 titanium alloy and 304 stainless-steel at 1273–1433 K” Materials & Design 169 (2019) 107667, have been discussed. The comments are mainly focused on the wetting mechanism. We used the ISD method for characterization of the intrinsic wetting behavior of molten Cu on 304ss. In Sun et al.’s work, they adopt MSD method for characterization. With this respect the obtained data and discussed results are doubtful. For the wetting behavior characterization of metal/metal system, oxide film is a non-negligible factor on both the droplet surface and the substrate surface. To characterize the intrinsic wetting behavior, it is necessary to avoid the involvements of de-oxidation process and the influence of melting process.

The Influence of Plasticizers and Accelerated Ageing on Biodegradation of PLA under Controlled Composting Conditions

The overall performance of plasticizers on common mechanical and physical properties, as well as on the processability of polylactic acid (PLA) films, is well-explored. However, the influence of plasticizers on biodegradation is still in its infancy. In this study, the influence of natural-based dicarboxylic acid-based ester plasticizers (MC2178 and MC2192), acetyl tributyl citrate (ATBC Citroflex A4), and polyethylene glycol (PEG 400) on the biodegradation of extruded PLA films was evaluated. Furthermore, the influence of accelerated ageing on the performance properties and biodegradation of films was further investigated. The biodegradation of films was determined under controlled thermophilic composting conditions (ISO 14855-1). Apart from respirometry, an evaluation of the degree of disintegration, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM) of film surfaces was conducted. The influence of melt-processing with plasticizers has a significant effect on structural changes. Especially, the degree of crystallinity has been found to be a major factor which affects the biodegradation rate. The lowest biodegradation rates have been evaluated for films plasticized with PEG 400. These lower molecular weight plasticizers enhanced the crystallinity degrees of the PLA phase due to an increase in chain mobility. On the contrary, the highest biodegradation rate was found for films plasticized with MC2192, which has a higher molecular weight and evoked minimal structural changes of the PLA. From the evaluated results, it could also be stated that migration of plasticizers, physical ageing, and chain scission of films prompted by ageing significantly influenced both the mechanical and thermal properties, as well as the biodegradation rate. Therefore, the ageing of parts has to be taken into consideration for the proper evolution of the biodegradation of plasticized PLA and their applications.

Microstructure Homogeneity and Mechanical Properties of Large-Size As-Cast High Nb Containing TiAl Alloy Ingot

The high Nb containing TiAl alloy with a nominal composition of Ti–44Al–8Nb–0.2W–0.2B–0.1Y was fabricated by a Vacuum Arc Remelting furnace. The microstructure and mechanical properties of specimens located in different sites of the ingot were investigated. Owing to the influence of melting process and electrode fabricating method, the morphologies and phase containing of this near lamellar structure in the top, middle, and bottom parts of ingot were different. The subtle difference in microstructure strongly influenced the room and high-temperature tensile properties in turn. However, the dominant influence factor of the mechanical properties was the defects at the bottom of this large-size ingot, though the bottom had the finest grain size.

Influence of melt processing with electromagnetic acoustic fields on the structure and properties of Al–Si system alloys

The research on the influence of melt processing with electromagnetic acoustic fields on the structure and properties of binary alloys Al–12%Si and Al–20%Si was conducted. The frequency of electromagnetic field induced in the loop antenna was changed between 500, 1000 and 2000 kHz during the experiments. Melts were processed after their degassing and refining. It was determined that this method of melt processing reduces the average total time of alloy production by 12 %. Short-term treatment of melts with electromagnetic acoustic fields helps to grind main phase alloy components and to improve their mechanical properties. Grinding of α-Al dendrites (from 30 to 22 μm) and eutectic Si crystals (from 13 to 10 μm) was observed while processing Al–12%Si eutectic alloy with a frequency of 500 kHz. At the same time, Al–20%Si hypereutectic alloy treatment with a frequency of 1000 kHz led to reduction of eutectic Si crystals from 8 to 5 μm, and of primary Si crystals – from 90 to 62 μm. Under specified processing conditions the tensile strength of Al–12%Si eutectic alloy increased by 13 %, and elongation – by 17 %, the same mechanical properties of Al–20%Si hypereutectic alloy increased by 9 and 65 % respectively. Based on the studies performed it was concluded that the choice of parameters for Al–Si melt processing with electromagnetic acoustic fields depended on the silicon content in the alloy. The increase in silica concentration needs treatment with the waves of higher vibration frequency. This processing technique allows modifying the fine crystalline structure of alloys and as a result causes an improvement of their mechanical properties. It can be successfully used for the production of fine-grained ligatures and Al–Si system alloys. However, further research is required to determine optimal processing parameters depending on the structure of the original charge and the nature of the alloys.

Influence of melt processing on biodegradable nisin‐PBAT films intended for active food packaging applications

ABSTRACTBiodegradable poly(butylene adipate‐co‐terephthalate) (PBAT) films incorporated with different levels of the antimicrobial peptide nisin were developed by melt processing. Structural, morphological, thermal, mechanical, and antimicrobial properties of the films were determined. The X‐ray diffraction patterns exhibited decreasing levels of intensity at 2θ values as the concentration of nisin increased. Scanning electron microscopy showed a heterogeneous morphology when higher amounts of nisin were incorporated. The antimicrobial films tested presented no significant differences in the melting temperature (123–125°C), and the crystallization temperature ranged from 69 to 75°C. The addition of nisin caused no significant modification in tensile strength values. However, results of Young's modulus and deformation at break differed significantly among samples. Active films demonstrated inhibition against the Gram‐positive bacterium Listeria monocytogenes. These results demonstrated that PBAT/nisin films produced by melt processing present a great potential for use as active food packaging materials aiming enhanced food safety. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43212.

Reactive extrusion effects on rheological and mechanical properties of poly(lactic acid)/poly[(butylene succinate)‐co‐adipate]/epoxy chain extender blends and clay nanocomposites

ABSTRACTPoly(lactic acid) (PLA), a biosource, biodegradable polymer, is not suitable for some important polymer processing operations, such as film blowing and blow molding, due to its low melt strength. Moreover, while it has high tensile modulus and strength in the solid state, it exhibits low ductility. The present work is an extension of our earlier effort to improve the processability and mechanical properties of PLA by blending with poly[(butylene succinate)‐co‐adipate)] (PBSA), a biodegradable polymer with lower glass transition temperature. We evaluate the influences of incorporation of an epoxy chain extender and nanoclay on the properties of the blend. Since earlier work was conducted in a batch mixer, the influence of melt processing in the twin screw extruder and the differences between products obtained in the extruder and the batch mixer are evaluated and explained. Based on earlier work, the following PLA/PBSA blend ratios of 90:10, 80:20 and 70:30 were selected. All the samples were prepared in the twin‐screw extruder at two different screw speeds (50 and 150 rpm), to evaluate the effects of residence time and shear rates. The morphology and structure of the blends were examined using field emission scanning electron microscopy. Transmission electron microscopy (TEM) and X‐ray diffraction (XRD) were used to evaluate the levels of intercalation and exfoliation in the nanocomposites. The chain extension reaction was evaluated using nuclear magnetic resonance (NMR) spectroscopy and other techniques. Rheological properties (dynamic oscillatory shear and elongational viscosity measurements) and mechanical characteristics of the pure components, blends, and nanocomposites were studied and discussed in light of the composition and morphology of the blends and the nanocomposites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42664.

Experimental Study on Influence of Fly Ash in Melting Process on Heavy Metal Speciation

The influence of melting process on heavy metal speciation was studied. The results show that although there are different changes of heavy metals Cd, Cu, Mn and Zn after melting process, percentage of residue is increasing and others are decreasing. Before melting process, Pb exists mainly in carbonate, Fe-Mn oxide and organic matter bound fractions and in Fe-Mn oxide bound fraction after the process. The percentage distribution of Cr, As, Ba and Ni are not changed obviously before and after melting. In general, the existence forms of all testing heavy metals trend to more stable speciation after melting process.

Study on the Influence of Melt Processing on Segmented Polyurethanes Morphology

AbstractA study on thermoplastic polyurethanes (TPU) is described. The investigation focuses on morphology of TPU parts depending on processing conditions and its relation with mechanical and thermal properties. It was found that TPU materials present different crystalline structures depending on chemical composition and melt processing conditions during part manufacturing. Due to that fact, strong variations in mechanical and tribological properties are expected.

Flux penetration in granular YBa 2Cu 3O 7−δ samples : A magneto-optical study

Using the high-resolution Faraday effect (HRF) technique, flux distributions of sintered, granular YBa 2Cu 3O 7−δ samples are obtained. The flux penetration is found to occur stepwise and only the last step of the penetration of Abrikosov vortices into individual grains can be observed directly. The high spatial resolution of the HRF technique enables one to determine the flux-density profiles inside individual grains. From these profiles, the intragranular critical current densities and acting local pinning forces are obtained. The intragranular critical current densities and the corresponding volume pinning forces are found to be reciprocally dependent on the grain size. This behavior could be explained by pinning at the grain boundaries between superconducting YBa 2Cu 3O 7−δ grains and non-superconducting phases like BaCuO 2 assuming a disturbed layer Δ x with a thickness of approximately 0.1 μm. Furthermore, the influence of melt processing on the weak-link behavior can be directly observed in the flux distributions. Melt-processed samples are found to show an intermediate behavior of flux penetration between sintered, polycrystalline samples and single-crystalline materials like single crystals and epitaxial thin films. It is shown that the parameter γ= H g cl / H J cl , linking the lower critical field of the grains, H g cl, to the lower critical field of the matrix, H J cl, has a significant influence on the flux-penetration behavior in type-II superconductors.

Key indicators for plastics performance in consumer products

AbstractTwo overriding characteristics for major applications of plastics in consumer products are: —the need for high volume production and —their exposure to hostile environments.Successful application and continued growth for plastics in these products requires knowledgeable prediction of performance in the process to produce the plastic part and in the environments to which it will be exposed during the product's lifetime. Progress on establishing relationships between material properties and structure are described with emphasis on response to melt process conditions and behavior when exposed to hostile environments.Commercial plastics and the processes by which they are converted into useful applications are complex systems. A multitude of interacting variables must be dealt with in order to achieve successful implementation in commercial products. Specific examples are discussed in the area of processing for non‐Newtonian flow characteristics and overt effects in injection molding and extrusion, tailoring of polymers within established rheological limits and the influence of melt processing on physical and mechanical properties. The influence of application environments is discussed and specific examples are given for environmental stress cracking, stress‐environment embrittlement and the effects of hot water solutions on polymer systems.