Modification of poly(lactic) acid by reactive extrusion and its melt blending with acrylonitrile–butadiene–styrene

Poly(lactic) acid (PLA) is a biodegradable polymer that has attracted interest as a potential substitute for some thermoplastic polymers. However, its advanced brittleness at room temperature represents one of the major drawbacks for its general use. In this work, PLA was modified by reactive extrusion (PLA_REx) to enhance the rheological behaviour and to limit its degradation. The modified material was melt blended with acrylonitrile–butadiene–styrene (ABS), and the resultant morphology, rheological, thermo‐mechanical and fracture behaviour were analysed. Since PLA does not have reasonable compatibility with ABS, maleic‐anhydride‐grafted ABS (ABS‐g‐Ma) was used as compatibilizer. The morphology of the PLA_REx/ABS samples resulted in the formation of small ABS rods in the matrix. The presence of maleic anhydride contributed to reducing the interfacial energy of the blends and to obtaining finer micro‐domains of the ABS‐rich phase in the PLA_REx matrix. In the compatibilized blends, the presence of elongated ABS‐rich phases opposed free crack propagation and contributed to the increase in fracture energy in comparison to neat PLA. © 2020 Society of Chemical Industry     

Refractive Index Dispersion of Sodium Magnesium Silicate Glasses for Ultralow-Loss Fibers

The refractive index dispersion and infrared (IR) reflection spectra of soda magnesium silicate glasses with low Rayleigh scattering were measured to evaluate their potential for use in fabricating ultralow-loss fibers. The zero-material dispersion wavelength (λ₀) was found to be around 1.5 μm, which is one of the key wavelengths in the present telecommunication system. The compositional dependence of λ₀ was found to relate to the population of nonbridging oxygen. Since the oscillation strength and frequency of the Si—O stretching vibrations of the glasses were found to be smaller than those of silica glass, their IR absorption loss was considered to be less than that of silica glass. The minimum loss due to the intrinsic factors, Rayleigh scattering and IR absorption, was estimated to be 0.06 dB/km at 1.6μm.     

Adsorption and Decomposition of Glycerol on Pristine and Oxygen Modified Au(111) Surfaces

Topics in Catalysis - Research on biomass derived raw materials for conventional catalytic processes, especially those directed to replace human dependence on fossil-based energy, is a high...     

Effect of hard segment content and carbon-based nanostructures on the kinetics of flexible polyurethane nanocomposite foams

Reactive flexible polyurethane (PU) foams were synthesized with two contents of hard segments (HS) and filled with multi-walled carbon nanotubes (MWCNTs), functionalized MWCNTs (f-MWCNTs) and functionalized graphene sheets (FGS). The effect of the HS content and the carbon nanofillers on the kinetics of polymerization and the kinetics of phase-separation have been studied by Fourier transform infrared spectroscopy (FT-IR) and synchrotron small-angle X-ray scattering (SAXS). A slow down on the rate of polymerization and on the development of the polymer structure due to the increase of the HS content and the inclusion of the nanoparticles was observed. Therefore, this work demonstrates that there is a relationship between the kinetics of polymerization and the kinetics of phase separation in flexible PU nanocomposite foams. SAXS data was used to generate 3D microstructures of PU nanocomposite foams and the phase-separated morphology was observed by atomic force microscopy (AFM).     

Characterization of residual compressive stresses in layered ceramics by positron annihilation spectroscopy

Microstructural characterization of stress states of alumina layers subjected to residual compressive stresses was performed by positron annihilation spectroscopy (PAS). Al₂O₃–t-ZrO₂ three layered samples were appropriately designed and processed by sequential slip casting with symmetric structure. The zirconia contents inside the core layer were selected in order to generate compressive stresses of variable intensity in the outer Al₂O₃ layers. PAS results highlighted a correlation between positron annihilation parameters and microstructural changes related to the generation of residual stresses.     

Oxy-apatite reaction sintering of colloidal and classic ceramic processed powders

Oxy-apatites are promising electrolyte materials for intermediate-temperature solid oxide fuel cells, IT–SOFC. However the requirements of electrolytes make necessary the preparation of dense films with the appropriated composition to show good electrical properties; in this way, colloidal processing is a key issue.This work involves the application of colloidal processing for four oxygen-excess oxy-apatites, La_9.67(Si₆O₂₄)O_2.5, La₁₀(Si₆O₂₄)O₃, La₁₀(Si_5.5Al_0.5O₂₄)O_2.75 and La₁₀(Si₅Al₁O₂₄)O_2.5 and their characterization (phases, microstructure and electrical properties). The results have been compared with those obtained by classical ceramic method to assure the same composition without loosing properties. Samples with the desired compositions were obtained by reaction sintering of La₂O₃, SiO₂ and Al₂O₃. La₁₀(Si_5.5Al_0.5O₂₄)O_2.75 prepared by colloidal processing and heated at 1923 K showed the highest conductivity value, 3.0 × 10^?2 S cm^?1 at 973 K. Furthermore, its residual porosity was very low. On the other hand, La₁₀(Si₆O₂₄)O₃ stoichiometry was tried by colloidal and ceramic methods under several experimental conditions. Unfortunately, the obtained oxy-apatite seems to have slightly lower lanthanum content. In spite of previous reports claiming the preparation of stoichiometric La₁₀(Si₆O₂₄)O₃, this study cannot support these findings.     

Effective Air‐Spray Deposition of Thin Films Obtained by Sol–Gel Process onto Complex Pieces of Sanitary Ware

A deposition mechanism by air‐spray technique is carried out for depositing silica‐based thin films obtained by the sol–gel process. The air‐spray deposition is very useful to coat large and complex surfaces with different morphologies and roughnesses which favors the technology scale‐up, contrary to the most used deposition methods in the sol–gel process (dip and spin coating). To establish the adequate conditions of these techniques, a complete study of the sol properties (rheology, FT‐IR, roughness, thickness) is attempted, which has allowed determining the parameters for the effective air‐spray deposition of homogeneous thin films. By means of an experimental design, it has been possible to validate the selected parameters. Finally, a scheme of an effective spray deposition model is proposed for a better understanding of the deposition mechanisms.     

Waste Frying Oils as Substrate for Enzymatic Lipolysis: Optimization of Reaction Conditions in O/W Emulsion

Waste frying oils (WFO) can be both environmental pollutants and a source of valuable products. In this work we explore the conversion of WFO into surface‐active substances, such as FFA and partial glycerides, through enzymatic hydrolysis in O/W emulsion. Two different WFO and three lipases of different origin were tested. In addition, we optimized the conditions for the production of O/W emulsions to be used as reaction medium as well as several reaction parameters, such as the type of enzyme and its concentration, the pH, and the presence of Ca²⁺ ions. Gum arabic‐stabilized emulsions with an oil fraction of 0.15 proved to be the most adequate owing to their high interfacial area and short‐term stability. The physicochemical characterization of both WFO revealed the presence of an increased amount of surface‐active matter relative to food‐grade vegetable oils. These substances, mainly FFA, can interfere with lipase action and reduce the reaction rate. However, the extent of hydrolysis was only slightly affected by them, and remained fairly similar to that achieved with a control mixture of food‐grade vegetable oils. The product distribution depended on the enzyme used. Pseudomonas fluorescens lipase was found to be particularly suitable for the production of partial glycerides (mono‐ and diacylglycerols), which are in great demand by the food industry. In any case our results demonstrate that WFO are a good substrate for enzymatic hydrolysis, comparable to food‐grade vegetable oils, providing an alternative route for the valorization of this waste.     

Study of natural teeth color according to toothguide 3d master through cluster analysis

How natural teeth color are grouped with Toothguide 3D Master according to color coordinates, L*, C*, and h* is reported. Tooth color was measured through the Easyshade Compact (Vita‐Zahnfabrik) spectrophotometer using a sample of 1361 subjects aged between 16 and 89 years. The color of the middle third of the maxillary central incisor was registered according to the Toothguide 3D Master nomenclature and the coordinates L*, C*, and h*. Cluster analysis and the SPAD 5.5 statistical package were applied for data processing. Of the 1361 participants, only 545 (40%) had a match among the 26 physical shade tabs of the Toothguide 3D Master. Statistical analysis revealed the existence of four cluster groups: Cluster 1 comprised shade tabs 1M1–2L1.5–2M1; cluster 2 comprised 1M2–2L2.5–2M2–2M3–2R2.5–3M2–3L2.5; cluster 3 comprised 2R1.5–3L1.5–3M1–3R1.5–4L1.5–4M1; and cluster 4 comprised 3M3–3R2.5–4M2–4L2.5–4R1.5–4R2.5–4M3–5M1–5M2–5M3. Statistically significant differences (P < 0.0.1) were also found, both in the color dimension, and among the four cluster groups revealed. Taking into account the limitations of this study, the natural teeth color can be grouped into four clusters by following coordinates L*, C*, and h,* resulting from the compact spectrophotometer Vita Easyshade. Natural teeth color are not distributed homogeneously with Toothguide 3D Master according to color coordinates. © 2014 Wiley Periodicals, Inc. Col Res Appl, 41, 101–107, 2016