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Materials, Volume 8, Issue 2 (February 2015), Pages 379-831

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Open AccessEditorial Materials Best Paper Award 2015
Materials 2015, 8(2), 829-831; https://doi.org/10.3390/ma8020829
Received: 13 February 2015 / Accepted: 13 February 2015 / Published: 17 February 2015
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Abstract
Materials has established an annual award for the best article and for the best review published in Materials in order to acknowledge the outstanding contributions of our authors in the area of materials science and engineering.[...] Full article
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Open AccessArticle Damping Enhancement of Composite Panels by Inclusion of Shunted Piezoelectric Patches: A Wave-Based Modelling Approach
Materials 2015, 8(2), 815-828; https://doi.org/10.3390/ma8020815
Received: 24 November 2014 / Revised: 7 January 2015 / Accepted: 12 February 2015 / Published: 17 February 2015
Cited by 3 | PDF Full-text (379 KB) | HTML Full-text | XML Full-text
Abstract
The waves propagating within complex smart structures are hereby computed by employing a wave and finite element method. The structures can be of arbitrary layering and of complex geometric characteristics as long as they exhibit two-dimensional periodicity. The piezoelectric coupling phenomena are considered
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The waves propagating within complex smart structures are hereby computed by employing a wave and finite element method. The structures can be of arbitrary layering and of complex geometric characteristics as long as they exhibit two-dimensional periodicity. The piezoelectric coupling phenomena are considered within the finite element formulation. The mass, stiffness and piezoelectric stiffness matrices of the modelled segment can be extracted using a conventional finite element code. The post-processing of these matrices involves the formulation of an eigenproblem whose solutions provide the phase velocities for each wave propagating within the structure and for any chosen direction of propagation. The model is then modified in order to account for a shunted piezoelectric patch connected to the composite structure. The impact of the energy dissipation induced by the shunted circuit on the total damping loss factor of the composite panel is then computed. The influence of the additional mass and stiffness provided by the attached piezoelectric devices on the wave propagation characteristics of the structure is also investigated. Full article
(This article belongs to the Special Issue Smart Materials)
Open AccessArticle Alginate-Collagen Fibril Composite Hydrogel
Materials 2015, 8(2), 799-814; https://doi.org/10.3390/ma8020799
Received: 17 November 2014 / Revised: 10 February 2015 / Accepted: 12 February 2015 / Published: 16 February 2015
Cited by 20 | PDF Full-text (2717 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
We report on the synthesis and the mechanical characterization of an alginate-collagen fibril composite hydrogel. Native type I collagen fibrils were used to synthesize the fibrous composite hydrogel. We characterized the mechanical properties of the fabricated fibrous hydrogel using tensile testing; rheometry and
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We report on the synthesis and the mechanical characterization of an alginate-collagen fibril composite hydrogel. Native type I collagen fibrils were used to synthesize the fibrous composite hydrogel. We characterized the mechanical properties of the fabricated fibrous hydrogel using tensile testing; rheometry and atomic force microscope (AFM)-based nanoindentation experiments. The results show that addition of type I collagen fibrils improves the rheological and indentation properties of the hydrogel. Full article
(This article belongs to the Special Issue Mechanics of Biomaterials) Printed Edition available
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Open AccessArticle Recycling of Sustainable Co-Firing Fly Ashes as an Alkali Activator for GGBS in Blended Cements
Materials 2015, 8(2), 784-798; https://doi.org/10.3390/ma8020784
Received: 19 October 2014 / Revised: 12 January 2015 / Accepted: 11 February 2015 / Published: 16 February 2015
Cited by 4 | PDF Full-text (1788 KB) | HTML Full-text | XML Full-text
Abstract
This study investigates the feasibility of co-firing fly ashes from different boilers, circulating fluidized beds (CFB) or stokers as a sustainable material in alkali activators for ground granulated blast-furnace slag (GGBS). The mixture ratio of GGBS and co-firing fly ashes is 1:1 by
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This study investigates the feasibility of co-firing fly ashes from different boilers, circulating fluidized beds (CFB) or stokers as a sustainable material in alkali activators for ground granulated blast-furnace slag (GGBS). The mixture ratio of GGBS and co-firing fly ashes is 1:1 by weight. The results indicate that only CF fly ash of CFB boilers can effectively stimulate the potential characteristics of GGBS and provide strength as an alkali activator. CF fly ash consists of CaO3 (48.5%), SiO2 (21.1%), Al2O3 (13.8%), SO3 (10.06%), Fe2O3 (2.25%) and others (4.29%). SA fly ash consists of Al2O3 (19.7%), SiO2 (36.3%), Fe2O3 (28.4%) and others (15.6%). SB fly ash consists of Al2O3 (15%), SiO2 (25.4%), Zn (20.6%), SO3 (10.9%), Fe2O3 (8.78%) and others (19.32%). The mixtures of SA fly ash and SB fly ash with GGBS, respectively, were damaged in the compressive strength test during seven days of curing. However, the built up strength of the CF fly ash and GGBS mixture can only be maintained for 7–14 days, and the compressive strength achieves 70% of that of a controlled group (cement in hardening cement paste). The strength of blended CF fly ash and GGBS started to decrease after 28 days, and the phenomenon of ettrigite was investigated due to the high levels of sulfur content. The CaO content in sustainable co-firing fly ashes must be higher than a certain percentage in reacting GGBS to ensure the strength of blended cements. Full article
(This article belongs to the Section Advanced Composites)
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Open AccessReview The Effect of Different Non-Metallic Inclusions on the Machinability of Steels
Materials 2015, 8(2), 751-783; https://doi.org/10.3390/ma8020751
Received: 19 December 2014 / Revised: 6 February 2015 / Accepted: 11 February 2015 / Published: 16 February 2015
Cited by 21 | PDF Full-text (2578 KB) | HTML Full-text | XML Full-text
Abstract
Considerable research has been conducted over recent decades on the role of non‑metallic inclusions and their link to the machinability of different steels. The present work reviews the mechanisms of steel fractures during different mechanical machining operations and the behavior of various non-metallic
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Considerable research has been conducted over recent decades on the role of non‑metallic inclusions and their link to the machinability of different steels. The present work reviews the mechanisms of steel fractures during different mechanical machining operations and the behavior of various non-metallic inclusions in a cutting zone. More specifically, the effects of composition, size, number and morphology of inclusions on machinability factors (such as cutting tool wear, power consumption, etc.) are discussed and summarized. Finally, some methods for modification of non-metallic inclusions in the liquid steel are considered to obtain a desired balance between mechanical properties and machinability of various steel grades. Full article
(This article belongs to the Special Issue Steels)
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Open AccessReview Recent Progress on PEDOT-Based Thermoelectric Materials
Materials 2015, 8(2), 732-750; https://doi.org/10.3390/ma8020732
Received: 6 January 2015 / Revised: 23 January 2015 / Accepted: 9 February 2015 / Published: 16 February 2015
Cited by 67 | PDF Full-text (2314 KB) | HTML Full-text | XML Full-text
Abstract
The thermoelectric properties of poly(3,4-ethylenedioxythiophene) (PEDOT)-based materials have attracted attention recently because of their remarkable electrical conductivity, power factor, and figure of merit. In this review, we summarize recent efforts toward improving the thermoelectric properties of PEDOT-based materials. We also discuss thermoelectric measurement
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The thermoelectric properties of poly(3,4-ethylenedioxythiophene) (PEDOT)-based materials have attracted attention recently because of their remarkable electrical conductivity, power factor, and figure of merit. In this review, we summarize recent efforts toward improving the thermoelectric properties of PEDOT-based materials. We also discuss thermoelectric measurement techniques and several unsolved problems with the PEDOT system such as the effect of water absorption from the air and the anisotropic thermoelectric properties. In the last part, we describe our work on improving the power output of thermoelectric modules by using PEDOT, and we outline the potential applications of polymer thermoelectric generators. Full article
(This article belongs to the Special Issue Low-Dimensional Anisotropic Thermoelectrics)
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Open AccessReview Advances in Nanotechnology for Restorative Dentistry
Materials 2015, 8(2), 717-731; https://doi.org/10.3390/ma8020717
Received: 5 January 2015 / Revised: 4 February 2015 / Accepted: 12 February 2015 / Published: 16 February 2015
Cited by 30 | PDF Full-text (697 KB) | HTML Full-text | XML Full-text
Abstract
Rationalizing has become a new trend in the world of science and technology. Nanotechnology has ascended to become one of the most favorable technologies, and one which will change the application of materials in different fields. The quality of dental biomaterials has been
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Rationalizing has become a new trend in the world of science and technology. Nanotechnology has ascended to become one of the most favorable technologies, and one which will change the application of materials in different fields. The quality of dental biomaterials has been improved by the emergence of nanotechnology. This technology manufactures materials with much better properties or by improving the properties of existing materials. The science of nanotechnology has become the most popular area of research, currently covering a broad range of applications in dentistry. This review describes the basic concept of nanomaterials, recent innovations in nanomaterials and their applications in restorative dentistry. Advances in nanotechnologies are paving the future of dentistry, and there are a plenty of hopes placed on nanomaterials in terms of improving the health care of dental patients. Full article
(This article belongs to the Special Issue Dental Materials)
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Open AccessArticle Low Temperature Synthesis and Characterization of AlScMo3O12
Materials 2015, 8(2), 700-716; https://doi.org/10.3390/ma8020700
Received: 26 December 2014 / Revised: 13 January 2015 / Accepted: 10 February 2015 / Published: 16 February 2015
Cited by 1 | PDF Full-text (1121 KB) | HTML Full-text | XML Full-text
Abstract
Recent interest in low and negative thermal expansion materials has led to significant research on compounds that exhibit this property, much of which has targeted the A2M3O12 family (A = trivalent cation, M = Mo, W). The expansion
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Recent interest in low and negative thermal expansion materials has led to significant research on compounds that exhibit this property, much of which has targeted the A2M3O12 family (A = trivalent cation, M = Mo, W). The expansion and phase transition behavior in this family can be tuned through the choice of the metals incorporated into the structure. An undesired phase transition to a monoclinic structure with large positive expansion can be suppressed in some solid solutions by substituting the A-site by a mixture of two cations. One such material, AlScMo3O12, was successfully synthesized using non-hydrolytic sol-gel chemistry. Depending on the reaction conditions, phase separation into Al2Mo3O12 and Sc2Mo3O12 or single-phase AlScMo3O12 could be obtained. Optimized conditions for the reproducible synthesis of stoichiometric, homogeneous AlScMo3O12 were established. High resolution synchrotron diffraction experiments were carried out to confirm whether samples were homogeneous and to estimate the Al:Sc ratio through Rietveld refinement and Vegard’s law. Single-phase samples were found to adopt the orthorhombic Sc2W3O12 structure at 100 to 460 K. In contrast to all previously-reported A2M3O12 compositions, AlScMo3O12 exhibited positive thermal expansion along all unit cell axes instead of contraction along one or two axes, with expansion coefficients (200–460 K) of αa = 1.7 × 10−6 K−1, αb = 6.2 × 10−6 K−1, αc = 2.9 × 10−6 K−1 and αV = 10.8 × 10−6 K−1, respectively. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessArticle Enhanced Hydrophilicity and Biocompatibility of Dental Zirconia Ceramics by Oxygen Plasma Treatment
Materials 2015, 8(2), 684-699; https://doi.org/10.3390/ma8020684
Received: 17 January 2015 / Accepted: 12 February 2015 / Published: 16 February 2015
Cited by 21 | PDF Full-text (3145 KB) | HTML Full-text | XML Full-text
Abstract
Surface properties play a critical role in influencing cell responses to a biomaterial. The objectives of this study were (1) to characterize changes in surface properties of zirconia (ZrO2) ceramic after oxygen plasma treatment; and (2) to determine the effect of
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Surface properties play a critical role in influencing cell responses to a biomaterial. The objectives of this study were (1) to characterize changes in surface properties of zirconia (ZrO2) ceramic after oxygen plasma treatment; and (2) to determine the effect of such changes on biological responses of human osteoblast-like cells (MG63). The results indicated that the surface morphology was not changed by oxygen plasma treatment. In contrast, oxygen plasma treatment to ZrO2 not only resulted in an increase in hydrophilicity, but also it retained surface hydrophilicity after 5-min treatment time. More importantly, surface properties of ZrO2 modified by oxygen plasma treatment were beneficial for cell growth, whereas the surface roughness of the materials did not have a significant efficacy. It is concluded that oxygen plasma treatment was certified to be effective in modifying the surface state of ZrO2 and has the potential in the creation and maintenance of hydrophilic surfaces and the enhancement of cell proliferation and differentiation. Full article
(This article belongs to the Special Issue Dental Materials)
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Open AccessReview Recent Advances in Nanocomposite Materials of Graphene Derivatives with Polysaccharides
Materials 2015, 8(2), 652-683; https://doi.org/10.3390/ma8020652
Received: 16 December 2014 / Accepted: 5 February 2015 / Published: 16 February 2015
Cited by 23 | PDF Full-text (632 KB) | HTML Full-text | XML Full-text
Abstract
This review article presents the recent advances in syntheses and applications of nanocomposites consisting of graphene derivatives with various polysaccharides. Graphene has recently attracted much interest in the materials field due to its unique 2D structure and outstanding properties. To follow, the physical
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This review article presents the recent advances in syntheses and applications of nanocomposites consisting of graphene derivatives with various polysaccharides. Graphene has recently attracted much interest in the materials field due to its unique 2D structure and outstanding properties. To follow, the physical and mechanical properties of graphene are then introduced. However it was observed that the synthesis of graphene-based nanocomposites had become one of the most important research frontiers in the application of graphene. Therefore, this review also summarizes the recent advances in the synthesis of graphene nanocomposites with polysaccharides, which are abundant in nature and are easily synthesized bio-based polymers. Polysaccharides can be classified in various ways such as cellulose, chitosan, starch, and alginates, each group with unique and different properties. Alginates are considered to be ideal for the preparation of nanocomposites with graphene derivatives due to their environmental-friendly potential. The characteristics of such nanocomposites are discussed here and are compared with regard to their mechanical properties and their various applications. Full article
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Open AccessArticle Properties of Chemically Combusted Calcium Carbide Residue and Its Influence on Cement Properties
Materials 2015, 8(2), 638-651; https://doi.org/10.3390/ma8020638
Received: 23 November 2014 / Accepted: 5 February 2015 / Published: 13 February 2015
Cited by 3 | PDF Full-text (1146 KB) | HTML Full-text | XML Full-text
Abstract
Calcium carbide residue (CCR) is a waste by-product from acetylene gas production. The main component of CCR is Ca(OH)2, which can react with siliceous materials through pozzolanic reactions, resulting in a product similar to those obtained from the cement hydration process.
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Calcium carbide residue (CCR) is a waste by-product from acetylene gas production. The main component of CCR is Ca(OH)2, which can react with siliceous materials through pozzolanic reactions, resulting in a product similar to those obtained from the cement hydration process. Thus, it is possible to use CCR as a substitute for Portland cement in concrete. In this research, we synthesized CCR and silica fume through a chemical combustion technique to produce a new reactive cementitious powder (RCP). The properties of paste and mortar in fresh and hardened states (setting time, shrinkage, and compressive strength) with 5% cement replacement by RCP were evaluated. The hydration of RCP and OPC (Ordinary Portland Cement) pastes was also examined through SEM (scanning electron microscope). Test results showed that in comparison to control OPC mix, the hydration products for the RCP mix took longer to formulate. The initial and final setting times were prolonged, while the drying shrinkage was significantly reduced. The compressive strength at the age of 45 days for RCP mortar mix was found to be higher than that of OPC mortar and OPC mortar with silica fume mix by 10% and 8%, respectively. Therefore, the synthesized RCP was proved to be a sustainable active cementitious powder for the strength enhanced of building materials, which will result in the diversion of significant quantities of this by-product from landfills. Full article
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Open AccessReview New Cork-Based Materials and Applications
Materials 2015, 8(2), 625-637; https://doi.org/10.3390/ma8020625
Received: 20 November 2014 / Accepted: 4 February 2015 / Published: 10 February 2015
Cited by 11 | PDF Full-text (1005 KB) | HTML Full-text | XML Full-text
Abstract
This review work is an update of a previous work reporting the new cork based materials and new applications of cork based materials. Cork is a material which has been used for multiple applications. The most known uses of cork are in stoppers
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This review work is an update of a previous work reporting the new cork based materials and new applications of cork based materials. Cork is a material which has been used for multiple applications. The most known uses of cork are in stoppers (natural and agglomerated cork) for alcoholic beverages, classic floor covering with composite cork tiles (made by the binding of cork particles with different binders), and thermal/acoustic/vibration insulation with expanded corkboard in buildings and some other industrial fields. Many recent developments have been made leading to new cork based materials. Most of these newly developed cork materials are not yet on the market, but they represent new possibilities for engineers, architects, designers and other professionals which must be known and considered, potentially leading to their industrialization. This paper is a review covering the last five years of innovative cork materials and applications also mentioning previous work not reported before. Full article
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Open AccessArticle Al2O3/ZrO2/Y3Al5O12 Composites: A High-Temperature Mechanical Characterization
Materials 2015, 8(2), 611-624; https://doi.org/10.3390/ma8020611
Received: 28 October 2014 / Accepted: 29 January 2015 / Published: 10 February 2015
Cited by 4 | PDF Full-text (1719 KB) | HTML Full-text | XML Full-text
Abstract
An Al2O3/5 vol%·ZrO2/5 vol%·Y3Al5O12 (YAG) tri-phase composite was manufactured by surface modification of an alumina powder with inorganic precursors of the second phases. The bulk materials were produced by die-pressing and pressureless
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An Al2O3/5 vol%·ZrO2/5 vol%·Y3Al5O12 (YAG) tri-phase composite was manufactured by surface modification of an alumina powder with inorganic precursors of the second phases. The bulk materials were produced by die-pressing and pressureless sintering at 1500 °C, obtaining fully dense, homogenous samples, with ultra-fine ZrO2 and YAG grains dispersed in a sub-micronic alumina matrix. The high temperature mechanical properties were investigated by four-point bending tests up to 1500 °C, and the grain size stability was assessed by observing the microstructural evolution of the samples heat treated up to 1700 °C. Dynamic indentation measures were performed on as-sintered and heat-treated Al2O3/ZrO2/YAG samples in order to evaluate the micro-hardness and elastic modulus as a function of re-heating temperature. The high temperature bending tests highlighted a transition from brittle to plastic behavior comprised between 1350 and 1400 °C and a considerable flexural strength reduction at temperatures higher than 1400 °C; moreover, the microstructural investigations carried out on the re-heated samples showed a very limited grain growth up to 1650 °C. Full article
(This article belongs to the Section Advanced Composites)
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Open AccessArticle Method for Aluminum Oxide Thin Films Prepared through Low Temperature Atomic Layer Deposition for Encapsulating Organic Electroluminescent Devices
Materials 2015, 8(2), 600-610; https://doi.org/10.3390/ma8020600
Received: 5 November 2014 / Accepted: 27 January 2015 / Published: 10 February 2015
Cited by 14 | PDF Full-text (1017 KB) | HTML Full-text | XML Full-text
Abstract
Preparation of dense alumina (Al2O3) thin film through atomic layer deposition (ALD) provides a pathway to achieve the encapsulation of organic light emitting devices (OLED). Unlike traditional ALD which is usually executed at higher reaction n temperatures that may
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Preparation of dense alumina (Al2O3) thin film through atomic layer deposition (ALD) provides a pathway to achieve the encapsulation of organic light emitting devices (OLED). Unlike traditional ALD which is usually executed at higher reaction n temperatures that may affect the performance of OLED, this application discusses the development on preparation of ALD thin film at a low temperature. One concern of ALD is the suppressing effect of ambient temperature on uniformity of thin film. To mitigate this issue, the pumping time in each reaction cycle was increased during the preparation process, which removed reaction byproducts and inhibited the formation of vacancies. As a result, the obtained thin film had both high uniformity and density properties, which provided an excellent encapsulation performance. The results from microstructure morphology analysis, water vapor transmission rate, and lifetime test showed that the difference in uniformity between thin films prepared at low temperatures, with increased pumping time, and high temperatures was small and there was no obvious influence of increased pumping time on light emitting performance. Meanwhile, the permeability for water vapor of the thin film prepared at a low temperature was found to reach as low as 1.5 × 10−4 g/(m2·day) under ambient conditions of 25 °C and 60% relative humidity, indicating a potential extension in the lifetime for the OLED. Full article
(This article belongs to the Section Energy Materials)
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Open AccessArticle Producing Lignin-Based Polyols through Microwave-Assisted Liquefaction for Rigid Polyurethane Foam Production
Materials 2015, 8(2), 586-599; https://doi.org/10.3390/ma8020586
Received: 19 December 2014 / Accepted: 3 February 2015 / Published: 10 February 2015
Cited by 16 | PDF Full-text (559 KB) | HTML Full-text | XML Full-text
Abstract
Lignin-based polyols were synthesized through microwave-assisted liquefaction under different microwave heating times (5–30 min). The liquefaction reactions were carried out using polyethylene glycol (PEG-400)/glycerol as liquefying solvents and 97 wt% sulfur acid as a catalyst at 140 °C. The polyols obtained were analyzed
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Lignin-based polyols were synthesized through microwave-assisted liquefaction under different microwave heating times (5–30 min). The liquefaction reactions were carried out using polyethylene glycol (PEG-400)/glycerol as liquefying solvents and 97 wt% sulfur acid as a catalyst at 140 °C. The polyols obtained were analyzed for their yield, composition and structural characteristics using gel permeation chromatography (GPC), Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectra. FT-IR and NMR spectra showed that the liquefying solvents reacted with the phenol hydroxyl groups of the lignin in the liquefied product. With increasing microwave heating time, the viscosity of polyols was slightly increased and their corresponding molecular weight (MW) was gradually reduced. The optimal condition at the microwave heating time (5 min) ensured a high liquefaction yield (97.47%) and polyol with a suitable hydroxyl number (8.628 mmol/g). Polyurethane (PU) foams were prepared by polyols and methylene diphenylene diisocyanate (MDI) using the one-shot method. With the isocyanate/hydroxyl group ([NCO]/[OH]) ratio increasing from 0.6 to 1.0, their mechanical properties were gradually increased. This study provided some insight into the microwave-assisted liquefied lignin polyols for the production of rigid PU foam. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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