| 1. |
- Alongi, Jenny, et al.
(författare)
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Superior flame retardancy of cotton by synergetic effect of cellulose-derived nano-graphene oxide carbon dots and disulphide-containing polyamidoamines
- 2019
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Ingår i: Polymer degradation and stability. - : Elsevier. - 0141-3910 .- 1873-2321. ; 169
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Tidskriftsartikel (refereegranskat)abstract
- Linear polyamidoamines containing disulphide groups (SS-PAAs) were prepared by polyaddition of L-cystine with 2,2-bisacrylamidoacetic acid (B-CYSS), N,N'-methylenebisacrylamide (M-CYSS) and 1,4-bisacryloylpiperazine (BP-CYSS). They were evaluated as flame retardants for cotton, alone or with cellulose-derived nano-graphene oxide (nGO) carbon dots, to assess whether, due to their potential as radical scavengers, the latter would improve the already good performance of SS-PAAs. In vertical flame spread tests (VEST), cotton treated with 1% nGO burned as quickly as cotton, whereas B-CYSS, M-CYSS and BP-CYSS extinguished the flame at add-ons >= 12, 16 and 20%, respectively. Probably, the gaseous products of SS-PAA thermal degradation quenched the radicals involved in oxidation. Cotton treated with 8,12 and 15%, respectively, of B-CYSS, M-CYSS and BP-CYSS burned completely, but further addition of 1% nGO either inhibited ignition or shortly extinguished the flame, demonstrating synergism between the two components. Synergism was confirmed by assessing the synergism effectiveness parameter for the residual mass fraction (RMF) and by comparing the calculated and experimental TG curves in air for the cotton/SS-PAA-nGO systems. In cone calorimetry tests, the presence of nGO did not improve the already good performances of SS-PAAs, supporting the hypothesis that the action of both takes place in the gas phase.
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| 2. |
- Battegazzore, Daniele, et al.
(författare)
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Layer by Layer-functionalized rice husk particles : A novel and sustainable solution for particleboard production
- 2017
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Ingår i: Materials Today Communications. - : Elsevier. - 2352-4928. ; 13, s. 92-101
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Tidskriftsartikel (refereegranskat)abstract
- Rice husk particles from agro-wastes have been treated with a Layer by Layer (LbL) deposition of polyelectrolytes and further assembled to prepare a bio-based particle board. The all polymer system employed uses a branched polyethyleneimine combined with a polyacrylic acid. The two polyelectrolytes show a super-linear growth as demonstrated by infrared spectroscopy. A schematic description of the mechanism behind the LbL deposition on rice husk particles is proposed and discussed on the basis of electron microscopy observations. The mechanical properties of the prepared LbL-joined particle boards are evaluated and related to the unique structure and intermolecular ionic interaction occurring between the assembled polyelectrolytes. Only 2 BLs allow for the preparation of a free-standing/self-supporting material. Boards assembled with 3 and 4 BL-coated particles yielded impressive storage moduli of 1.7 and 2.2 GPa, respectively, as measured by dynamic mechanical analyses performed at different temperatures and relative humidities. When tested by three points bending mechanical tests the same materials showed an elastic moduli up to 3.2 GPa and a tensile strengths up to 12 MPa. The presented results demonstrate that the LbL functionalization of agro-waste particles represents an attractive, functional and sustainable solution for the production of mechanically strong particleboards.
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| 3. |
- Carosio, Federico, et al.
(författare)
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Clay nanopaper as multifunctional brick and mortar fire protection coating : Wood case study
- 2016
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Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 93, s. 357-363
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Wood is one of the most sustainable, esthetically pleasing and environmentally benign engineering materials, and is often used in structures found in buildings. Unfortunately, the fire hazards related to wood are limiting its application. The use of transparent cellulose nanofiber (CNF)/clay nanocomposites, with unique brick-and-mortar structure, is proposed as a sustainable and efficient fire protection coating for wood. Fire performance was assessed by cone calorimetry. When exposed to the typical 35 kW/m2 heat flux of developing fires, the time to ignition of coated wood samples increased up to about 4 1/2 min, while the maximum average rate of heat emission (MARHE) was decreased by 46% thus significantly reducing the potential fire threat from wood structures.
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| 4. |
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| 5. |
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| 6. |
- Carosio, Federico, et al.
(författare)
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Oriented Clay Nanopaper from Biobased Components Mechanisms for Superior Fire Protection Properties
- 2015
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 7:10, s. 5847-5856
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Tidskriftsartikel (refereegranskat)abstract
- The toxicity of the most efficient fire retardant additives is a major problem for polymeric Materials. Cellulose nanofiber (CNF)/clay nanocomposites, with unique brick-and-mortar structure and prepared by simple filtration, are characterized from the morphological point of view by scanning electron microscopy and X-ray diffraction. These nanocomposites have superior fire protection properties to Other clay nanocomposites and fiber composites. The Corresponding mechanisms are evaluated in terms of flammability (reaction to a flame) and cone calorimetry (exposure to heat flux). These two tests provide a wide spectrum characterization of fire protection properties in CNF/montmorrilonite (MTM) Materials. The morphology of the collected residues after flammability testing is investigated. In addition, thermal and thermo-oxidative stability are evaluated by thermogravimetric analyses performed in inert (nitrogen) and oxidative (air) atmospheres. Physical and chemical mechanisms are identified and related to the unique nanostructure and its low thermal conductivity, high gas barrier properties and CNF/ MTM interactions for char formation.
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| 7. |
- Castro, Daniele Oliveira, et al.
(författare)
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The use of a pilot-scale continuous paper process for fire retardant cellulose-kaolinite nanocomposites
- 2018
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Ingår i: Composites Science And Technology. - : Elsevier Ltd. - 0266-3538 .- 1879-1050. ; 162, s. 215-224
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Tidskriftsartikel (refereegranskat)abstract
- Nanostructured materials are difficult to prepare rapidly and at large scale. Melt-processed polymer-clay nanocomposites are an exception, but the clay content is typically below 5 wt%. An approach for manufacturing of microfibrillated cellulose (MFC)/kaolinite nanocomposites is here demonstrated in pilot-scale by continuous production of hybrid nanopaper structures with thickness of around 100 μm. The colloidal nature of MFC suspensions disintegrated from chemical wood fiber pulp offers the possibility to add kaolinite clay platelet particles of nanoscale thickness. For initial lab scale optimization purposes, nanocomposite processing (dewatering, small particle retention etc) and characterization (mechanical properties, density etc) were investigated using a sheet former (Rapid Köthen). This was followed by a continuous fabrication of composite paper structures using a pilot-scale web former. Nanocomposite morphology was assessed by scanning electron microscopy (SEM). Mechanical properties were measured in uniaxial tension. The fire retardancy was evaluated by cone calorimetry. Inorganic hybrid composites with high content of in-plane oriented nanocellulose, nanoclay and wood fibers were successfully produced at pilot scale. Potential applications include fire retardant paperboard for semi structural applications and as reinforcement mats in molded thermoset biocomposites.
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| 8. |
- Fu, Qiliang, et al.
(författare)
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Nanostructured Wood Hybrids for Fire-Retardancy Prepared by Clay Impregnation into the Cell Wall
- 2017
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Ingår i: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 9:41, s. 36154-36163
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Tidskriftsartikel (refereegranskat)abstract
- Eco-friendly materials need "green" fire-retardancy treatments, which offer opportunity for new wood nanotechnologies. Balsa wood (Ochroma pyramidale) was delignified to form a hierarchically structured and nanoporous scaffold mainly composed of cellulose nanofibrils. This nanocellulosic wood scaffold was impregnated with colloidal montmorillonite clay to form a nanostructured wood hybrid with high flame-retardancy. The nanoporous scaffold was characterized by scanning electron microscopy and gas adsorption. Flame-retardancy was evaluated by cone calorimetry, whereas thermal and thermo-oxidative stabilities were assessed by thermogravimetry. The location of well-distributed clay nanoplatelets inside the cell walls was confirmed by energy-dispersive X-ray analysis. This unique nanostructure dramatically increased the thermal stability because of thermal insulation, oxygen depletion, and catalytic charring effects. A coherent organic/inorganic charred residue was formed during combustion, leading to a strongly reduced heat release rate peak and reduced smoke generation.
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| 9. |
- Ghanadpour, Maryam, 1984-, et al.
(författare)
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All-natural and highly flame-resistant freeze-cast foams based on phosphorylated cellulose nanofibrils
- 2018
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Ingår i: Nanoscale. - : Royal Society of Chemistry. - 2040-3364 .- 2040-3372. ; 10:8, s. 4085-4095
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Tidskriftsartikel (refereegranskat)abstract
- Pure cellulosic foams suffer from low thermal stability and high flammability, limiting their fields of application. Here, light-weight and flame-resistant nanostructured foams are produced by combining cellulose nanofibrils prepared from phosphorylated pulp fibers (P-CNF) with microfibrous sepiolite clay using the freeze-casting technique. The resultant nanocomposite foams show excellent flame-retardant properties such as self-extinguishing behavior and extremely low heat release rates in addition to high flame penetration resistance attributed mainly to the intrinsic charring ability of the phosphorylated fibrils and the capability of sepiolite to form heat-protective intumescent-like barrier on the surface of the material. Investigation of the chemical structure of the charred residue by FTIR and solid state NMR spectroscopy reveals the extensive graphitization of the carbohydrate as a result of dephosphorylation of the modified cellulose and further dehydration due to acidic catalytic effects. Originating from the nanoscale dimensions of sepiolite particles, their high specific surface area and stiffness as well as its close interaction with the phosphorylated fibrils, the incorporation of clay nanorods also significantly improves the mechanical strength and stiffness of the nanocomposite foams. The novel foams prepared in this study are expected to have great potential for application in sustainable building construction.
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| 10. |
- Ghanadpour, Maryam, 1984-, et al.
(författare)
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Phosphorylated Cellulose Nanofibrils : A Renewable Nanomaterial for the Preparation of Intrinsically Flame-Retardant Materials
- 2015
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 16:10, s. 3399-3410
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose from wood fibers can be modified for use in flame-retardant composites as an alternative to halogen-based compounds. For this purpose, sulfite dissolving pulp fibers have been chemically modified by phosphorylation, and the resulting material has been used to prepare cellulose nanofibrils (CNF) that have a width of approximately 3 nm. The phosphorylation was achieved using (NH4)(2)HPO4 in the presence of urea, and the degree of substitution by phosphorus was determined by X-ray photoelectron spectroscopy, conductometric titration, and nuclear magnetic resonance spectroscopy. The presence of phosphate groups in the structure of CNF has been found to noticeably improve the flame retardancy of this material. The nanopaper sheets prepared from phosphorylated CNF showed self-extinguishing properties after consecutive applications of a methane flame for 3 s and did not ignite under a heat flux of 35 kW/m(2), as shown by flammability and cone calorimetry measurements, respectively.
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| 11. |
- Ghanadpour, Maryam, 1984-, et al.
(författare)
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Ultrastrong and flame-resistant freestanding films from nanocelluloses, self-assembled using a layer-by-layer approach
- 2017
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Ingår i: Applied Materials Today. - : Elsevier. - 2352-9407. ; 9, s. 229-239
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Tidskriftsartikel (refereegranskat)abstract
- Nanosized cellulose nanofibrils (CNF) prepared from phosphorylated pulp fibers (P-CNF) are combined with CNF prepared from aminated fibers (cationic CNF) through a layer-by-layer (LbL) assembly to prepare a freestanding, transparent all-cellulose film. It is shown that the thermal stability and flame-retardant properties of the all CNF film are significantly improved when phosphorylated CNF is combined with cationic fibrils in an LbL assembled structure. The freestanding films also show a tensile strength of 160 MPa and a Young's modulus of 9 GPa, placing it among strongest freestanding LbL films fabricated so far, showing large promise for the use of these types of ultrathin films in advanced applications. The LbL build-up of the cationic CNF/P-CNF multilayer film is carefully studied by quartz crystal microbalance with dissipation (QCM-D) and atomic force microscopy (AFM). Hydrophobized silicon substrates are used for the LbL deposition and it is shown that the (cationic CNFIP-CNF)(300) film, 2.3 pin thick, can be easily detached from the substrate using tweezers. The thermal stability, combustion behavior and mechanical properties of the films are further studied by thermogravimetric analysis, combustion and tensile tests respectively.
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| 12. |
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| 13. |
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| 14. |
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| 15. |
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| 16. |
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| 17. |
- Koklukaya, Oruc, et al.
(författare)
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Superior Flame-Resistant Cellulose Nanofibril Aerogels Modified with Hybrid Layer-by-Layer Coatings
- 2017
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 9:34, s. 29082-29092
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Tidskriftsartikel (refereegranskat)abstract
- Nanometer thin films consisting of cationic chitosan (Ch), anionic poly(vinylphosphonic acid) (PVPA), and anionic montmorillonite clay (MMT) are deposited on highly porous, wet-stabilized cellulose nanofibril (CNF) aerogels via the layer-by-layer (LbL) technique. Model experiments with silicon oxide surfaces are used to study the details of LbL formation and the multilayer structure. Formation of layers on the aerogels is also investigated as a function of solution concentration by use of polyelectrolyte titration. Thermogravimetric analysis indicates that the LbL coating significantly improves thermal stability of the CNF aerogel. Horizontal flame test shows that aerogels coated with five quadlayers of Ch/PVPA/Ch/MMT, using solutions/dispersion of high concentration, are able to self-extinguish immediately after removal of flame, and LbL-coated aerogels do not ignite under heat flux (35 kW/m(2)) in cone calorimetry. The LbL-coated aerogel can prevent flame penetration from a torch focused on the surface, achieving temperature drops up to 650 degrees C across the 10 mm thick specimen for several minutes. LbL treatment is hence a rapid and highly effective way to specifically tailor the surface properties of CNF aerogels in order to confer unprecedented flame-retardant characteristics.
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| 18. |
- Koklukaya, Oruc, et al.
(författare)
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Tailoring flame-retardancy and strength of papers via layer-by-layer treatment of cellulose fibers
- 2018
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Ingår i: Cellulose. - : Springer. - 0969-0239 .- 1572-882X. ; 25:4, s. 2691-2709
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Tidskriftsartikel (refereegranskat)abstract
- The layer-by-layer (LbL) technology was used to adsorb polyelectrolyte multilayers consisting of cationic polyethylenimine (PEI) and anionic sodium hexametaphosphate (SHMP) onto cellulose fibers in order to enhance the flame-retardancy and tensile strength of paper sheets made from these fibers. The fundamental effect of PEI molecular mass on the build-up of the multilayer film was investigated using model cellulose surfaces and a quartz crystal microbalance technique. The adsorption of a low (LMw) and a high molecular weight (HMw) PEI onto cellulose fibers and carboxymethylated (CM) cellulose fibers was investigated using polyelectrolyte titration. The fibers were consecutively treated with PEI and SHMP to deposit 3.5 bilayers (BL) on the fiber surfaces, and the treated fibers were then used to prepare sheets. In addition, a wet-strength paper sheet was prepared and treated with the same LbL coatings. Thermal gravimetric analysis of LbL-treated fibers showed that the onset temperature for cellulose degradation was lowered and that the amount of residue at 800 °C increased. A horizontal flame test and a vertical flame test were used to evaluate the combustion behavior of the paper sheets. Papers prepared from both cellulose fibers and CM-cellulose fibers treated with HMw-PEI/SHMP LbL-combination self-extinguished in a horizontal configuration despite the rather low amounts of adsorbed polymer which form very thin films (wet thickness of ca. 17 nm). The tensile properties of handsheets showed that 3.5 BL of HMw-PEI and SHMP increased the stress at break by 100% compared to sheets prepared from untreated cellulose fibers.
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| 19. |
- Köklükaya, Oruç, et al.
(författare)
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Flame-Retardant Paper from Wood Fibers Functionalized via Layer-by-Layer Assembly
- 2015
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 7:42, s. 23750-23759
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Tidskriftsartikel (refereegranskat)abstract
- The highly flammable character of cellulose-rich fibers from wood limits their use in some advanced materials. To suppress the flammability and introduce flame-retardant properties to individual pulp fibers, we deposited nanometer thin films consisting of cationic chitosan (CH) and anionic poly(vinylphosphonic acid) (PVPA) on fibers using the layer-by-layer (LbL) technique. The buildup of the rnultilayer film was investigated in the presence and absence of salt (NaCl) using model cellulose surfaces and a quartz crystal microbalance technique. Fibers were then treated with the same strategy, and the treated fibers were used to prepare paper sheets. A horizontal flame test (HFT) and cone calorimetry were conducted to evaluate the combustion behavior of paper sheets as a function of the number of bilayers deposited on fibers. In HFT, paper made of fibers coated with 20 CH/PVPA bilayers (BL), self-extinguished the flame, while uncoated fibers were completely consumed. Scanning electron microscopy of charred paper after HFT revealed that a thin shell of the charred polymeric multilayer remained after the cellulose fibers had been completely oxidized. Cone calorimetry demonstrated that the phosphorus-containing thin films (20 BL is similar to 25 nm) reduced the peak heat release rate by 49%. This study identifies a unique and highly effective way to impart flame-retardant characteristic to pulp fibers and the papers made from these fibers.
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| 20. |
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| 21. |
- Köklükaya, Oruç, et al.
(författare)
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The use of model cellulose gel beads to clarify flame-retardant characteristics of layer-by-layer nanocoatings
- 2021
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 255
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Tidskriftsartikel (refereegranskat)abstract
- Layer-by-Layer (LbL) assembled nanocoatings are exploited to impart flame-retardant properties to cellulosic substrates. A model cellulose material can make it possible to investigate an optimal bilayer (BL) range for the deposition of coating while elucidating the main flame-retardant action thus allowing for an efficient design of optimized LbL formulations. Model cellulose gel beads were prepared by dissolving cellulose-rich fibers followed by precipitation. The beads were LbL-treated with chitosan (CH) and sodium hexametaphosphate (SHMP). The char forming properties were studied using thermal gravimetric analysis. The coating increased the char yield in nitrogen to up to 29 % and showed a distinct pattern of micro intumescent behavior upon heating. An optimal range of 10-20 BL is observed. The well-defined model cellulose gel beads hence introduce a new scientific route both to clarify the fundamental effects of different film components and to optimize the composition of the films.
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| 22. |
- Li, Lengwan, et al.
(författare)
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Recyclable nanocomposites of well-dispersed 2D layered silicates in cellulose nanofibril (CNF) matrix
- 2022
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 279, s. 119004-
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Tidskriftsartikel (refereegranskat)abstract
- Nanocomposites based on components from nature, which can be recycled are of great interest in new materials for sustainable development. The range of properties of nacre-inspired hybrids of 1D cellulose and 2D clay platelets are investigated in nanocomposites with improved nanoparticle dispersion in the starting hydrocolloid mixture. Films with a wide range of compositions are prepared by capillary force assisted physical assembly (vacuum-assisted filtration) of TEMPO-oxidized cellulose nanofibers (TOCN) reinforced by exfoliated nanoclays of three different aspect ratios: saponite, montmorillonite and mica. X-ray diffraction and transmission electron micrographs show almost monolayer dispersion of saponite and montmorillonite and high orientation parallel to the film surface. Films exhibit ultimate strength up to 573 MPa. Young's modulus exceeds 38 GPa even at high MTM contents (40-80 vol%). Optical transmittance, UV-shielding, thermal shielding and fire-retardant properties are measured, found to be very good and are sensitive to the 2D nanoplatelet dispersion.
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| 23. |
- Maddalena, Lorenza, et al.
(författare)
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Polyelectrolyte-Assisted Dispersions of Reduced Graphite Oxide Nanoplates in Water and Their Gas-Barrier Application
- 2021
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 13:36, s. 43301-43313
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Tidskriftsartikel (refereegranskat)abstract
- Dispersion of graphene and related materials in water is needed to enable sustainable processing of these 2D materials. In this work, we demonstrate the capability of branched polyethylenimine (BPEI) and polyacrylic acid (PAA) to stabilize reduced graphite oxide (rGO) dispersions in water. Atomic force microscopy colloidal probe measurements were carried out to investigate the interaction mechanisms between rGO and the polyelectrolytes (PEs). Our results show that for positive PEs, the interaction appears electrostatic, originating from the weak negative charge of graphene in water. For negative PEs, however, van der Waals forces may result in the formation of a PE shell on rGO. The PE-stabilized rGO dispersions were then used for the preparation of coatings to enhance gas barrier properties of polyethylene terephthalate films using the layer-by-layer self-assembly. Ten bilayers of rGO(BPEI)/rGO(PAA) resulted in coatings with excellent barrier properties as demonstrated by oxygen transmission rates below detection limits [<0.005 cm(3)/(m(2) day atm)]. The observed excellent performance is ascribed to both the high density of the deposited coating and its efficient stratification. These results can enable the design of highly efficient gas barrier solutions for demanding applications, including oxygen-sensitive pharmaceutical products or flexible electronic devices.
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| 24. |
- Marcioni, Massimo, et al.
(författare)
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Flame-retardant Lightweight materials from layer-by-layer coated cellulose fibers
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Cellulose fibers were functionalized using the layer-by-layer approach, which allows for the formation of a coating by positively and negatively charged layers of polyelectrolytes on the fiber surface, consisting of sodium hexametaphosphate and chitosan. By using this coating approach, it was possible to obtain a bio-based, homogeneous and flame-retardant coating. Self-extinguishing properties was achieved at 1 bi-layer (BL) as visible in a horizontal flame test, while non-ignitability was obtained after 3BL coating. The coated cellulose fibers were used to produce foams, a self-standing lightweight 3D structure, by freeze-drying. Even though made by mainly cellulose, these foams gave self-extinguishing results when prepared by 1BL coated fibers and non-ignitability when prepared with 3BL coated fibers. Cone calorimetry showed a decrease in heat release rate and total heat release of 56% and 68% respectively for the foam containing 3BL coated fibers.
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| 25. |
- Marcioni, Massimo, et al.
(författare)
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Layer-by-Layer-Coated Cellulose Fibers Enable the Production of Porous, Flame-Retardant, and Lightweight Materials
- 2023
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 15:30, s. 36811-36821
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Tidskriftsartikel (refereegranskat)abstract
- New sustainable materialsproduced by green processing routes arerequired in order to meet the concepts of circular economy. The replacementof insulating materials comprising flammable synthetic polymers bybio-based materials represents a potential opportunity to achievethis task. In this paper, low-density and flame-retardant (FR) porousfiber networks are prepared by assembling Layer-by-Layer (LbL)-functionalizedcellulose fibers by means of freeze-drying. The LbL coating, encompassingchitosan and sodium hexametaphosphate, enables the formation of aself-sustained porous structure by enhancing fiber-fiber interactionsduring the freeze-drying process. Fiber networks prepared from 3 Bi-Layer(BL)-coated fibers contain 80% wt of cellulose and can easily self-extinguishthe flame during flammability tests in vertical configuration whiledisplaying extremely low combustion rates in forced combustion tests.Smoke release is 1 order of magnitude lower than that of commerciallyavailable polyurethane foams. Such high FR efficiency is ascribedto the homogeneity of the deposited assembly, which produces a protectiveexoskeleton at the air/cellulose interface. The results reported inthis paper represent an excellent opportunity for the developmentof fire-safe materials, encompassing natural components where sustainabilityand performance are maximized.
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| 26. |
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| 27. |
- Medina, Lilian, et al.
(författare)
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Nanocomposites from Clay, Cellulose Nanofibrils, and Epoxy with Improved Moisture Stability for Coatings and Semi-Structural Applications
- 2019
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Ingår i: ACS Applied Nano Materials. - : American Chemical Society (ACS). - 2574-0970.
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Tidskriftsartikel (refereegranskat)abstract
- A new type of high reinforcement content clay-cellulose-thermoset nanocomposite was proposed, where epoxy precursors diffused into a wet porous clay-nanocellulose mat, followed by curing. The processing concept was scaled to > 200 µm thickness composites, the mechanical properties were high for nanocomposites and the materials showed better tensile properties at 90% RH compared with typical nanocellulose materials. The nanostructure and phase distributions were studied using transmission electron microscopy; Young’s modulus, yield strength, ultimate strength and ductility were determined as well as moisture sorption, fire retardancy and oxygen barrier properties. Clay and cellulose contents were varied, as well as the epoxy content. Epoxy had favorable effects on moisture stability, and also improved reinforcement effects at low reinforcement content. More homogeneous nano- and mesoscale epoxy distribution is still required for further property improvements. The materials constitute a new type of three-phase nanocomposites, of interest as coatings, films and as laminated composites for semi-structural applications.
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| 28. |
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| 29. |
- Medina, Lilian, et al.
(författare)
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Recyclable nanocomposite foams of Poly(vinyl alcohol), clay and cellulose nanofibrils - Mechanical properties and flame retardancy
- 2019
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Ingår i: Composites Science And Technology. - : Elsevier. - 0266-3538 .- 1879-1050. ; 182
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Tidskriftsartikel (refereegranskat)abstract
- Foam-like clay-nanocellulose hybrids are of great interest as load-bearing structural foams with excellent fire retardancy, due to unique effects from clay on thermal cellulose degradation. For the first time, the fire retardancy of clay-nanocellulose foams are studied in detail, in particular the effect of a third polymer phase, poly(vinyl alcohol). The composition with optimum mechanical properties and fire retardancy is identified and analyzed. Foams are prepared by freeze-drying and the compositions are varied systematically. Thermogravimetric analysis is performed on foam degradation. Mechanical properties from compression tests and fire retardancy data from cone calorimetry are reported, together with cellular structures from SEM and relative density estimates for the foams. Self-extinguishing foams are obtained with superior flame retardancy to commercial polymer foams. Addition of poly(vinyl alcohol) is beneficial for mechanical properties of clay-nanocellulose foams, but impedes the fire retardancy by reducing clay-cellulose synergies and cellulose charring during degradation.
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| 30. |
- Mianehrow, Hanieh, et al.
(författare)
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Strong reinforcement effects in 2D cellulose nanofibril-graphene oxide (CNF-GO) nanocomposites due to GO-induced CNF ordering
- 2020
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7496 .- 2050-7488. ; 8:34, s. 17608-17620
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Tidskriftsartikel (refereegranskat)abstract
- Nanocomposites from native cellulose with low 2D nanoplatelet content are of interest as sustainable materials combining functional and structural performance. Cellulose nanofibril-graphene oxide (CNF-GO) nanocomposite films are prepared by a physical mixing-drying method, with a focus on low GO content, the use of very large GO platelets (2-45 mu m) and nanostructural characterization using synchrotron X-ray source for WAXS and SAXS. These nanocomposites can be used as transparent coatings, strong films or membranes, as gas barriers or in laminated form. CNF nanofibrils with random in-plane orientation, form a continuous non-porous matrix with GO platelets oriented in-plane. GO reinforcement mechanisms in CNF are investigated, and relationships between nanostructure and suspension rheology, mechanical properties, optical transmittance and oxygen barrier properties are investigated as a function of GO content. A much higher modulus reinforcement efficiency is observed than in previous polymer-GO studies. The absolute values for modulus and ultimate strength are as high as 17 GPa and 250 MPa at a GO content as small as 0.07 vol%. The remarkable reinforcement efficiency is due to improved organization of the CNF matrix; and this GO-induced mechanism is of general interest for nanostructural tailoring of CNF-2D nanoplatelet composites.
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| 31. |
- Mianehrow, Hanieh, et al.
(författare)
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Strong reinforcement effects in 2D cellulose nanofibril–graphene oxide (CNF–GO) nanocomposites due to GO-induced CNF ordering
- 2020
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Ingår i: Journal of Materials Chemistry A. - 2050-7488 .- 2050-7496. ; 8:34, s. 17608-17620
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Tidskriftsartikel (refereegranskat)abstract
- Nanocomposites from native cellulose with low 2D nanoplatelet content are of interest as sustainable materials combining functional and structural performance. Cellulose nanofibril–graphene oxide (CNF–GO) nanocomposite films are prepared by a physical mixing–drying method, with a focus on low GO content, the use of very large GO platelets (2–45 μm) and nanostructural characterization using synchrotron X-ray source for WAXS and SAXS. These nanocomposites can be used as transparent coatings, strong films or membranes, as gas barriers or in laminated form. CNF nanofibrils with random in-plane orientation, form a continuous non-porous matrix with GO platelets oriented in-plane. GO reinforcement mechanisms in CNF are investigated, and relationships between nanostructure and suspension rheology, mechanical properties, optical transmittance and oxygen barrier properties are investigated as a function of GO content. A much higher modulus reinforcement efficiency is observed than in previous polymer–GO studies. The absolute values for modulus and ultimate strength are as high as 17 GPa and 250 MPa at a GO content as small as 0.07 vol%. The remarkable reinforcement efficiency is due to improved organization of the CNF matrix; and this GO-induced mechanism is of general interest for nanostructural tailoring of CNF-2D nanoplatelet composites.
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| 32. |
- Salviati, Sergio, et al.
(författare)
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Ice-templated nanocellulose porous structure enhances thermochemical storage kinetics in hydrated salt/graphite composites
- 2020
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Ingår i: Renewable energy. - : Elsevier BV. - 0960-1481 .- 1879-0682. ; 160, s. 698-706
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Tidskriftsartikel (refereegranskat)abstract
- The freeze-drying technique is employed for the production of novel strontium bromide/graphite/ nanocellulose composites for thermochemical heat storage application. The aim is to obtain a better control and stability of salt organization within the composite, while maximizing the air/salt and salt/ graphite interfacial areas and enhancing mass and heat transfer associated to the salt hydration and dehydration. A comparison with a conventional wet impregnation method is also reported. The morphology was investigated by means of scanning electron microscopy. Differential scanning calorimetry was employed to evaluate the energy storage density, while hydration kinetics were evaluated at 23 degrees C and 50% RH. The wet impregnation approach delivered materials with a limited porosity while freeze-drying produced highly porous structures with oriented channels for moisture transport across the composite. The organic binder provided an active contribution to the energy storage process, producing energy storage densities up to 764 kJ/kg, 48% greater than the theoretical value. Freeze-dried nanocellulose composites evidenced a significant increase of 54% in the hydration kinetics, compared to the pristine salt. Based on these results, the freeze-drying of ternary composites based on salt hydrate, graphite and nanocellulose is envisaged as a promising route for the production of fast charge and discharge thermochemical storage systems.
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| 33. |
- Samanta, Archana, Post doc Researcher, et al.
(författare)
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Charge Regulated Diffusion of Silica Nanoparticles into Wood for Flame Retardant Transparent Wood
- 2022
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Ingår i: Advanced Sustainable Systems. - : Wiley. - 2366-7486 .- 2366-7486. ; 6:4, s. 2100354-2100354
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Tidskriftsartikel (refereegranskat)abstract
- The preparation of wood substrates modified by charged inorganic nanoparticles (NPs) diffusing into the internal cell wall structure is investigated for generating functional properties. The flammability problem of wood biocomposites is addressed. NPs applied from colloidal sols carry charge to stabilize them against aggregation. The influence of charge on particle diffusion and adsorption should play a role for their spatial distribution and localization in the wood substrate biocomposite. It is hypothesized that improved dispersion, infiltration, and stability of NPs into the wood structure can be achieved by charge control diffusion, also restricting NP agglomeration and limiting distribution to the wood cell wall. Cationic and anionic silica NPs of ≈30 nm are therefore allowed to diffuse into bleached wood. The influence of charge on distribution in wood is investigated as a function of initial sol concentration. Transparent wood is fabricated by in situ polymerization of a thiolene in the wood pore space. These biocomposites demonstrate excellent flame retardancy with selfextinguishing characteristics. The approach has potential for commercial fabrication of flame retardant transparent composites for glazing and other building applications.
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| 34. |
- Samanta, Pratick, et al.
(författare)
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Coloration and Fire Retardancy of Transparent Wood Composites by Metal Ions
- 2023
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 15:50, s. 58850-58860
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Tidskriftsartikel (refereegranskat)abstract
- Transparent wood composites (TWs) offer the possibility of unique coloration effects. A colored transparent wood composite (C-TW) with enhanced fire retardancy was impregnated by metal ion solutions, followed by methyl methacrylate (MMA) impregnation and polymerization. Bleached birch wood with a preserved hierarchical structure acted as a host for metal ions. Cobalt, nickel, copper, and iron metal salts were used. The location and distribution of metal ions in C-TW as well as the mechanical performance, optical properties, and fire retardancy were investigated. The C-TW coloration is tunable by controlling the metal ion species and concentration. The metal ions reduced heat release rates and limited the production of smoke during forced combustion tests. The potential for scaled-up production was verified by fabricating samples with a dimension of 180 x 100 x 1 (l x b x h) mm(3).
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| 35. |
- Samanta, Pratick, et al.
(författare)
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Fire-retardant and transparent wood biocomposite based on commercial thermoset
- 2022
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Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 156
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Tidskriftsartikel (refereegranskat)abstract
- Transparent wood (TW) biocomposites combine high optical transmittance and good mechanical properties and can contribute to sustainable development. The safety against fire is important for building applications. Here, a "green" bleached wood reinforcement is impregnated by water soluble and flame-retardant melamine formaldehyde (MF) in a scalable process, for a wood content of 25 vol%. FE-SEM is used for characterization of optical defects and EDX to examine MF distribution at nanoscale cell wall pore space. Curing (FTIR-ATR), mechanical properties, optical transmittance (74% at 1.2 mm thickness) and flame-retardant properties are also characterized (self-extinguishing behavior and cone calorimetry), and scattering mechanisms are discussed. The fire growth rate of transparent wood was less than half the values for neat wood. Transparent wood/MF biocomposites show interesting wood-MF synergies and are of practical interest in building applications. Critical aspects of processing are analyzed for minimization of optical defects.
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| 36. |
- Tabaka, Weronika, et al.
(författare)
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Bench-scale fire stability testing - Assessment of protective systems on carbon fibre reinforced polymer composites
- 2021
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Ingår i: Polymer testing. - : Elsevier BV. - 0142-9418 .- 1873-2348. ; 102
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Tidskriftsartikel (refereegranskat)abstract
- Fire resistance testing of components made of carbon fibre reinforced polymers (CFRP) usually demands intermediate-scale or full-scale testing. A bench-scale test is presented as a practicable and efficient method to assess how different fire protective systems improve the structural integrity of CFRPs during fire. The direct flame of a fully developed fire was applied to one side of the CFRP specimen, which was simultaneously loaded with compressive force. Three different approaches (film, non-woven, and coatings) were applied: paper with a thickness in the range of mu m consisting of cellulose nanofibre (CNF)/clay nanocomposite, nonwoven mats with thickness in the range of cm and intumescent coatings with a thickness in the range of mm. The uncoated specimen failed after just 17 s. Protection by these systems provides fire stability, as they multiply the time to failure by as much as up to 43 times. The reduced heating rates of the protected specimens demonstrate the reduced heat penetration, indicating the coatings' excellent heat shielding properties. Bench-scale fire stability testing is shown to be suitable tool to identify, compare and assess different approaches to fire protection.
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| 37. |
- Wicklein, Bernd, et al.
(författare)
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Thermally insulating and fire-retardant lightweight anisotropic foams based on nanocellulose and graphene oxide
- 2015
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Ingår i: Nature Nanotechnology. - 1748-3387 .- 1748-3395. ; 10:3, s. 277-283
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Tidskriftsartikel (refereegranskat)abstract
- High-performance thermally insulating materials from renewable resources are needed to improve the energy efficiency of buildings. Traditional fossil-fuel-derived insulation materials such as expanded polystyrene and polyurethane have thermal conductivities that are too high for retrofitting or for building new, surface-efficient passive houses. Tailored materials such as aerogels and vacuum insulating panels are fragile and susceptible to perforation. Here, we show that freeze-casting suspensions of cellulose nanofibres, graphene oxide and sepiolite nanorods produces super-insulating, fire-retardant and strong anisotropic foams that perform better than traditional polymer-based insulating materials. The foams are ultralight, show excellent combustion resistance and exhibit a thermal conductivity of 15 mW m(-1) K-1, which is about half that of expanded polystyrene. At 30 degrees C and 85% relative humidity, the foams retained more than half of their initial strength. Our results show that nanoscale engineering is a promising strategy for producing foams with excellent properties using cellulose and other renewable nanosized fibrous materials.
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| 38. |
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| 39. |
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