| 1. |
- García-García, Daniel, et al.
(författare)
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Optimizing the yield and physico-chemical properties of pine cone cellulose nanocrystals by different hydrolysis time
- 2018
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Ingår i: Cellulose. - : Springer. - 0969-0239 .- 1572-882X. ; 25:5, s. 2925-2938
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose nanocrystals (CNCs) were isolated for the first time from pine cones (PC) by alkali and bleaching treatments and subsequent sulfuric acid hydrolysis (64%) at 45 degrees C. The influence of the hydrolytic reaction time (30, 45, and 90 min) on the yield, chemical composition and structure, and thermal stability of CNCs was evaluated. The removal of non-cellulosic constituents during the alkaline and bleaching treatment resulted in high pure cellulosic fibres. The isolation of CNCs from these cellulosic fibres at different reaction times was verified by the nano-dimensions of the individual crystals (< 3 and < 335 nm of average diameter and length, respectively). The highest yield (15%) and the optimum CNCs properties in terms of aspect ratio, thermal stability and crystallinity were obtained for an extraction time of 45 min. PC appeared to be a new promising source of cellulose fibres and CNCs with potential to be applied as reinforcement in composites and for food-packaging.
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| 2. |
- García-García, Daniel, et al.
(författare)
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Reinforcing capability of cellulose nanocrystals obtained from pine cones in a biodegradable poly(3-hydroxybutyrate)/poly(ε-caprolactone) (PHB/PCL) thermoplastic blend
- 2018
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Ingår i: European Polymer Journal. - : Elsevier. - 0014-3057 .- 1873-1945. ; 104, s. 10-18
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Tidskriftsartikel (refereegranskat)abstract
- In this work, different loads (3, 5 and 7 wt%) of pine cone cellulose nanocrystals (CNCs) were added to films ofpoly(3-hydroxybutyrate)/poly(ε-caprolactone) (PHB/PCL) blends with a composition of 75 wt% PHB and 25 wt% PCL (PHB75/PCL25). The films were obtained after solvent casting followed by melt compounding in anextruder and finally subjected to a thermocompression process. The influence of different CNCs loadings on themechanical, thermal, optical, wettability and disintegration in controlled compost properties of the PHB75/PCL25blend was discussed. Field emission scanning electron microscopy (FESEM) revealed the best dispersion of CNCson the polymeric matrix was at a load of 3 wt%. Over this loading, CNCs aggregates were formed enhancing thefilms fragilization due to stress concentration phenomena. However, the addition of CNCs improved the opticalproperties of the PHB75/PCL25films by increasing their transparency and accelerated the film disintegration incontrolled soil conditions. In general, the blend with 3 wt% CNCs offers the best balanced properties in terms ofmechanical, thermal, optical and wettability
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| 3. |
- Moriana, Rosana, et al.
(författare)
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Improved thermo-mechanical properties by the addition of natural fibres in starch-based sustainable biocomposites
- 2011
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Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 42:1, s. 30-40
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Tidskriftsartikel (refereegranskat)abstract
- Sustainable biocomposites based on thermoplastic starch copolymers (Mater-Bi KE03B1) and biofibres (cotton, hemp and kenaf) were prepared and characterised in terms of their thermo-mechanical and morphological properties. Biocomposites exhibit improved thermal stability and mechanical properties in comparison with the Mater-Bi KE. Biofibres act as suitable thermal stabilizers for the Mater-Bi KE, by increasing the maximum decomposition temperature and the Ea associated to the thermal decomposition process. Biofibre addition into the Mater-Bi KE results in higher storage modulus and in a reduction of the free-volume-parameter associated to the Mater-Bi KE glass transition. The influence of different biofibres on the thermo-mechanical properties of the biocomposites has been discussed. Hemp and kenaf enhance the thermal stability and reduce the free volume-parameter of Mater-Bi KE more significantly than cotton fibres, although the latter exhibits the highest mechanical performance. These differences may be explained by the improved interaction of lignocellulosic fibres with the Mater-Bi KE, due to the presence of hemicellulose and lignin in their formulation. © 2010 Elsevier Ltd. All rights reserved.
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| 4. |
- Mankefors, S., et al.
(författare)
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Theoretical investigations of As overlayers on InP(110) surfaces
- 1997
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Ingår i: Physical Review B Condensed Matter. - : American Physical Society. - 0163-1829 .- 1095-3795. ; 56:24, s. 15847-15852
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Tidskriftsartikel (refereegranskat)abstract
- As adsorption and interaction with InP(110) is investigated by means of total-energy minimization calculations. We find that the As-P exchanged configuration has higher energy than the As/InP(110) epitaxially continued layer structure (ECLS), for all types of As reservoirs considered. In the presence of an additional As layer in ECLS (i.e., 1.5 ML adsorbed As), however, the exchanged configuration is only slightly higher in energy than the nonexchanged one. We conclude that the As-P exchange process is energetically unfavorable, and should in any case not be complete at room temperature, as suggested in a recent report. Our conclusion is supported by results of a photoemission study, including As adsorption, desorption, and redeposition, according to which the process is nonreversible.
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