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• Tannic acid is neither a good flame retardant nor a highly swelling material. • TA combined with CLS reduces flammability of biocomposite by 30 % compared to PLA. • Mixing of TA with CLS in melt doesn't allow for PHRR reduction of more than 20 %. The purpose of this study was to determine the quantitative and qualitative effects of the form of natural phenolic compounds (NPCs) on the decomposition of polylactide (PLA) under different measurement conditions. For this purpose, thermogravimetry analysis (TGA), differential scanning calorimetry (DSC), and pyrolysis-combustion flow calorimetry (PCFC) analyses were carried out not only on individual raw materials like calcium lignosulfonate (BX), tannic acid (TA), BX chemically modified with TA (BMT), but also on PLA/BX, PLA/TA, and PLA/BMT composites with 3, 6, and 9 wt.% of filler. Moreover, the work checked whether to obtain satisfactory results it is necessary to carry out chemical modification lasting many hours, or whether simple physical mixing of ingredients (TABX) is enough, e.g. in proportions 1:2, 2:4, 3:6. The results of these analyses showed that TA is neither a good flame retardant nor a highly swelling material, but when combined with BX physically or chemically, it can produce an interesting synergistic effect. This work proves that chemically obtained BMT hybrid material allows to reduce flammability by 30 % compared to PLA which cannot be achieved by physically mixing these components in a polymer melt. On the other hand, the addition of TABX is sufficient to achieve a good thermal stabilization effect under processing conditions. [Display omitted] [ABSTRACT FROM AUTHOR]

Choice of alkali cation in mix design of geopolymers is critical for their thermal performance. However, the influence of alkali cation type on strength endurance of geopolymers subject to high temperature exposure and the underlying governing mechanisms have not been studied. This study investigated the effects of alkali cation type on high temperature response of fly ash geopolymers aiming towards structural applications. In-depth investigation was carried out to discover the underlying mechanisms governing the strength endurance of fly ash geopolymers subject to high temperature exposure and its correlation with their volume stability and chemical stability. Results showed that potassium geopolymer exhibited significant strength enhancement (30–40%) and sodium geopolymer displayed reduced strength (10%), and the strength of mixed sodium and potassium geopolymer remained unchanged after exposure to elevated temperature. While the binders were chemically stable without deterioration and formation of new crystal phases after high temperature exposure, the volume stability varied with the type of alkali cation used. Formation of cracks and gel densification due to shrinkage, and healing of micro-cracks and change of pore sizes due to sintering were identified as responsible mechanisms at different temperature ranges. While crack development and enlargement of pores lowered the strength, densification of matrix and healing of micro-cracks favored strength gain. These competing mechanisms determine the strength endurance of geopolymers depending on the type of alkali cation used. Overall, it shows that geopolymers can be tailored, such that stable (or even enhanced) strengths upon thermal exposure are realized, for structural applications. [ABSTRACT FROM AUTHOR]

Abstract: Poly(benzyl methacrylate)-magnesium phyllosilicate nanocomposites were synthesized using a novel in situ intercalative ambient temperature atom transfer radical polymerization (ATATRP). The organic moiety in the synthesized magnesium phyllosilicate was modified to initiate ATRP, in the presence of Cu(I)/PMDETA. Exfoliation was achieved and this process was rapid. The anchoring efficiency of the polymer chains on the organically modified phyllosilicate increased with silicate loading. This route to nanocomposite preparation is expected to be general and viable, and superior in comparison to the melt mixing route which did not result in the formation of a nanocomposite in these systems. [Copyright &y& Elsevier]

Abstract: The knowledge of thermal properties of technical components or internals in chemical reactors is often a key characteristic for planning and designing chemical engineering processes. As an alternative to packed beds or packings, sponges turned out to be used in new application fields in chemical and process engineering. Therefore an experimental study was performed to investigate the two-phase thermal conductivity of solid ceramic sponges made of alumina, mullite and oxidic-bonded silicon carbide (OBSiC) at moderate temperatures. A two-dimensional model is used for analysing the measured temperature profiles and for calculating the thermal conductivity. It can be observed, that the thermal conductivity increases with decreasing porosity and is nearly constant when the pore size (ppi number) is varied. The thermal conductivity data are modelled by an approach similar to the well known Krischer model. Compared to a packed bed of spherical particles, the values of the thermal conductivity of sponges turn out to be about five times higher. [Copyright &y& Elsevier]

Abstract: Many fibrous materials such as nonwoven materials are often consolidated by means of hot calenders, i.e., hot compaction rolls. Hot calendering compresses the fiber assembly and can cause changes in the structure. In nonwovens, calendering has an added function of thermally bonding the fibers at their respective crossovers to form a strong but yet somewhat porous material. Calendering causes a significant increase in the solid volume fraction (SVF) of the media and therefore, affects their permeability. To our knowledge, no work in the literature has been dedicated to modeling the permeability of calendered nonwovens. In this study, virtual nonwoven structures are generated and compressed from top and bottom to resemble the hot calendering process. In agreement with our experimental observations, it was found that the average SVF profile across the material''s thickness turns into a U-shape profile after the calendering. In this work, the dimensionless permeability of the calendered media is computed using CFD tools and reported for different compaction ratios. Results of our simulations are compared with the experiment as well as the available empirical and/or analytical permeability models in the literature and good agreement, depending upon the SVF, is observed. We also studied the influence of orientation distribution of the fibers on the dimensionless permeability of the fabric and noticed that permeability decreases by increasing the directionality of the fibers. This is found to be primarily due to the fact that highly oriented uncompressed fiber-webs tend to have a higher SVF. Fiber-webs of identical SVF, however, exhibited almost identical permeabilities regardless of their fiber orientations. [Copyright &y& Elsevier]