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Gil-Castell, O., Badia, J. D., Strömberg, E., Karlsson, S. & Ribes-Greus, A. (2017). Effect of the dissolution time into an acid hydrolytic solvent to taylor electrospun nanofibrous polycaprolactone scaffolds. European Polymer Journal, 87, 174-187
Open this publication in new window or tab >>Effect of the dissolution time into an acid hydrolytic solvent to taylor electrospun nanofibrous polycaprolactone scaffolds
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2017 (English)In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 87, p. 174-187Article in journal (Refereed) Published
Abstract [en]

The hydrolysis of the polycaprolactone (PCL) as a function of the dissolution time in a formic/acetic acid mixture was considered as a method for tailoring the morphology of nanofibrous PCL scaffolds. Hence the aim of this research was to establish a correlation between the dissolution time of the polymer in the acid solvent with the physicochemical properties of the electrospun nanofibrous scaffolds and their further service life behaviour. The physico-chemical properties of the scaffolds were assessed in terms of fibre morphology molar mass and thermal behaviour. A reduction of the molar mass and the lamellar thickness as well as an increase of the crystallinity degree were observed as a function of dissolution time. Bead-free fibres were found after 24 and 48 h of dissolution time with similar diameter distributions. The decrease of the fibre diameter distributions along with the apparition of beads was especially significant for scaffolds prepared after 72 h and 120 h of dissolution time in the acid mixture. The service life of the obtained devices was evaluated by means of in vitro validation under abiotic physiological conditions. All the scaffolds maintained the nanofibrous structure after 100 days of immersion in water and PBS. The molar mass was barely affected and the crystallinity degree and the lamellar thickness increased along immersion preventing scaffolds from degradation. Scaffolds prepared after 24 h and 48 h kept their fibre diameters whereas those prepared after 72 h and 120 h showed a significant reduction. This PCL tailoring procedure to obtain scaffolds that maintain the nanoscaled structure after such long in vitro evaluation will bring new opportunities in the design of long-term biomedical patches. 

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
Electrospinning, Scaffold, Hydrolysis, Polycaprolactone (PCL), In vitro validation
National Category
Polymer Technologies Textile, Rubber and Polymeric Materials Polymer Chemistry
Identifiers
urn:nbn:se:his:diva-13498 (URN)10.1016/j.eurpolymj.2016.12.005 (DOI)000395210900015 ()2-s2.0-85007427983 (Scopus ID)
Available from: 2017-04-18 Created: 2017-04-18 Last updated: 2017-11-27Bibliographically approved
Gil-Castell, O., Badia, J. D., Kittikorn, T., Strömberg, E., Ek, M., Karlsson, S. & Ribes-Greus, A. (2016). Impact of hydrothermal ageing on the thermal stability, morphology and viscoelastic performance of PLA/sisal biocomposites. Paper presented at 5th International Conference on Bio-Based and Biodegradable Polymers (BIOPOL), San Sebastian, Spain, October 6-9, 2015. Polymer degradation and stability, 132, 87-96
Open this publication in new window or tab >>Impact of hydrothermal ageing on the thermal stability, morphology and viscoelastic performance of PLA/sisal biocomposites
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2016 (English)In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 132, p. 87-96Article in journal (Refereed) Published
Abstract [en]

The influence of the combined exposure to water and temperature on the behaviour of polylactide/sisal biocomposites coupled with maleic acid anhydride was assessed through accelerated hydrothermal ageing. The biocomposites were immersed in water at temperatures from 65 to 85 degrees C, between the glass transition and cold crystallisation of the PLA matrix. The results showed that the most influent factor for water absorption was the percentage of fibres, followed by the presence of coupling agent, whereas the effect of the temperature was not significant. Deep assessment was devoted to biocomposites subjected to hydrothermal ageing at 85 degrees C, since it represents the extreme degrading condition. The morphology and crystallinity of the biocomposites were evaluated by means of X-Ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). The viscoelastic and thermal performance were assessed by means of dynamic mechanic thermal analysis (DMTA) and thermogravimetry (TGA). The presence of sisal generally diminished the thermal stability of the biocomposites, which was mitigated by the addition of the coupling agent. After composite preparation, the effectiveness of the sisal fibre was improved by the crystallisation of PLA around sisal, which increased the storage modulus and reduced the dampening factor. The presence of the coupling agent strengthened this effect. After hydrothermal ageing, crystallisation was promoted in all biocomposites therefore showing more fragile behaviour evidencing pores and cracks. However, the addition of coupling agent in the formulation of biocomposites contributed in all cases to minimise the effects of hydrothermal ageing. 

Keywords
Biocomposites, Polylactide (PLA), Natural fibres, Sisal, Hydrothermal ageing, Degradation, Performance, Mechanical fibre effectiveness
National Category
Polymer Technologies Textile, Rubber and Polymeric Materials Polymer Chemistry
Identifiers
urn:nbn:se:his:diva-13422 (URN)10.1016/j.polymdegradstab.2016.03.038 (DOI)000393846000011 ()2-s2.0-84962695727 (Scopus ID)
Conference
5th International Conference on Bio-Based and Biodegradable Polymers (BIOPOL), San Sebastian, Spain, October 6-9, 2015
Available from: 2017-03-10 Created: 2017-03-10 Last updated: 2020-01-13Bibliographically approved
Vilaplana, F., Nilsson, J., Sommer, D. V. P. & Karlsson, S. (2015). Analytical markers for silk degradation: comparing historic silk and silk artificially aged in different environments. Analytical and Bioanalytical Chemistry, 407(5), 1433-1449
Open this publication in new window or tab >>Analytical markers for silk degradation: comparing historic silk and silk artificially aged in different environments
2015 (English)In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 407, no 5, p. 1433-1449Article in journal (Refereed) Published
Abstract [en]

Suitable analytical markers to assess the degree of degradation of historic silk textiles at molecular and macroscopic levels have been identified and compared with silk textiles aged artificially in different environments, namely (i) ultraviolet (UV) exposure, (ii) thermo-oxidation, (iii) controlled humidity and (iv) pH. The changes at the molecular level in the amino acid composition, the formation of oxidative moieties, crystallinity and molecular weight correlate well with the changes in the macroscopic properties such as brightness, pH and mechanical properties. These analytical markers are useful to understand the degradation mechanisms that silk textiles undergo under different degradation environments, involving oxidation processes, hydrolysis, chain scission and physical arrangements. Thermo-oxidation at high temperatures proves to be the accelerated ageing procedure producing silk samples that most resembled the degree of degradation of early seventeenth-century silk. These analytical markers will be valuable to support the textile conservation tasks currently being performed in museums to preserve our heritage.

Place, publisher, year, edition, pages
Springer Berlin/Heidelberg, 2015
Keywords
Silk, Conservation, Multivariate analysis, Amino acid composition, Infrared spectroscopy, Mechanical properties
National Category
Other Chemical Engineering Textile, Rubber and Polymeric Materials
Identifiers
urn:nbn:se:his:diva-13588 (URN)10.1007/s00216-014-8361-z (DOI)000349336400015 ()25492090 (PubMedID)2-s2.0-84937901397 (Scopus ID)
Available from: 2017-05-23 Created: 2017-05-23 Last updated: 2017-11-29Bibliographically approved
Atarijabarzadeh, S., Nilsson, F., Hillborg, H., Karlsson, S. & Strömberg, E. (2015). Image Analysis Determination of the Influence of Surface Structure of Silicone Rubbers on Biofouling. International Journal of Polymer Science, Article ID 390292.
Open this publication in new window or tab >>Image Analysis Determination of the Influence of Surface Structure of Silicone Rubbers on Biofouling
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2015 (English)In: International Journal of Polymer Science, ISSN 1687-9422, E-ISSN 1687-9430, article id 390292Article in journal (Refereed) Published
Abstract [en]

This study focuses on how the texture of the silicone rubber material affects the distribution of microbial growth on the surface of materials used for high voltage insulation. The analysis of surface wetting properties showed that the textured surfaces provide higher receding contact angles and therefore lower contact angle hysteresis. The textured surfaces decrease the risk for dry band formation and thus preserve the electrical properties of the material due to a more homogeneous distribution of water on the surface, which, however, promotes the formation of more extensive biofilms. The samples were inoculated with fungal suspension and incubated in a microenvironment chamber simulating authentic conditions in the field. The extent and distribution of microbial growth on the textured and plane surface samples representing the different parts of the insulator housing that is shank and shed were determined by visual inspection and image analysis methods. The results showed that the microbial growth was evenly distributed on the surface of the textured samples but restricted to limited areas on the plane samples. More intensive microbial growth was determined on the textured samples representing sheds. It would therefore be preferable to use the textured surface silicone rubber for the shank of the insulator.

Place, publisher, year, edition, pages
Hindawi Publishing Corporation, 2015
National Category
Polymer Technologies Textile, Rubber and Polymeric Materials
Identifiers
urn:nbn:se:his:diva-13591 (URN)10.1155/2015/390292 (DOI)000356264100001 ()2-s2.0-84934895948 (Scopus ID)
Available from: 2017-05-23 Created: 2017-05-23 Last updated: 2020-03-17Bibliographically approved
Moriana, R., Vilaplana, F., Karlsson, S. & Ribes, A. (2014). Correlation of chemical, structural and thermal properties of natural fibres for their sustainable exploitation. Carbohydrate Polymers, 112, 422-431
Open this publication in new window or tab >>Correlation of chemical, structural and thermal properties of natural fibres for their sustainable exploitation
2014 (English)In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 112, p. 422-431Article in journal (Refereed) Published
Abstract [en]

The potential of lignocellulosic natural fibres as renewable resources for thermal conversion and material reinforcement is largely dependent on the correlation between their chemical composition, crystalline structure and thermal decomposition properties. Significant differences were observed in the chemical composition of cotton, flax, hemp, kenaf and jute natural fibres in terms of cellulose, hemicellulose and lignin content, which influence their morphology, thermal properties and pyrolysis product distribution. A suitable methodology to study the kinetics of the thermal decomposition process of lignocellulosic fibres is proposed combining different models (Friedman, Flynn-Wall-Ozawa, Criado and Coats-Redfern). Cellulose pyrolysis can be modelled with similar kinetic parameters for all the natural fibres whereas the kinetic parameters for hemicellulose pyrolysis show intrinsic differences that can be assigned to the heterogeneous hemicellulose sugar composition in each natural fibre. This study provides the ground to critically select the most promising fibres to be used either for biofuel or material applications.

Place, publisher, year, edition, pages
Elsevier, 2014
Keywords
Natural fibres, Cellulose, Hemicellulose, Lignin, Crystalline content, Thermal properties
National Category
Polymer Technologies
Identifiers
urn:nbn:se:his:diva-15869 (URN)10.1016/j.carbpol.2014.06.009 (DOI)000341464600056 ()2-s2.0-84903648921 (Scopus ID)
Available from: 2014-10-16 Created: 2018-06-29 Last updated: 2019-11-26Bibliographically approved
Moriana, R., Strömberg, E., Ribes, A. & Karlsson, S. (2014). Degradation behaviour of natural fibre reinforced starch-based composites under different environmental conditions. Journal of Renewable Materials, 2(2), 145-156
Open this publication in new window or tab >>Degradation behaviour of natural fibre reinforced starch-based composites under different environmental conditions
2014 (English)In: Journal of Renewable Materials, ISSN 2164-6325, E-ISSN 2164-6341, Vol. 2, no 2, p. 145-156Article in journal (Refereed) Published
Abstract [en]

The purpose of this work was to study the effect of hydrothermal, biological and photo degradation on natural fibres reinforced biodegradable starch-based (Mater-BiKE) composites to characterize the structural changes occurring under exposure to different environments. The composites water-uptake rate was hindered by the interfacial interactions between matrix and fibres. Thermal, structural and morphological analysis provided useful information about the irreversible changes in the properties of the composites caused by degradation in soil and photodegradation, and their synergetic effects. The effects due to the photo-oxidation and degradation in soil on the composites depended on the different chemical composition of each fibre. The composite with more hemicellulose and lignin in its formulation was more affected by both types of degradation, but still the end result properties were better than the ones shown for the degraded Mater-BiKE. The photo-oxidation of all the studied materials achieved enhanced degradation rate in soil. The Mater-BiKE/ kenaf was shown to have the slowest water-uptake rate and better thermal properties once photo-oxidized, indicating better service life conditions. At the same time, the Mater-BiKE/kenaf was affected to a major extent by the synergetic effects of both photo-oxidation and soil burial test, showing a faster degradative rate and better disposal conditions. © 2014 Scrivener Publishing LLC.

Keywords
Biodegradable polymers, Composites, Natural fibres, Photodegradation test, Soil burial test, Water absorption test
National Category
Polymer Technologies
Identifiers
urn:nbn:se:his:diva-15890 (URN)10.7569/JRM.2014.634103 (DOI)000365663300007 ()2-s2.0-84941416223 (Scopus ID)
Available from: 2018-06-29 Created: 2018-06-29 Last updated: 2019-02-15Bibliographically approved
Gil-Castell, O., Badia, J. D., Kittikorn, T., Strömberg, E., Martínez-Felipe, A., Ek, M., . . . Ribes-Greus, A. (2014). Hydrothermal ageing of polylactide/sisal biocomposites: Studies of water absorption behaviour and Physico-Chemical performance. Paper presented at 4th International Conference on Biodegradable and Biobased Polymers (BIOPOL), OCT 01-03, 2013, Univ Perugia, Rome, ITALY. Polymer degradation and stability, 108(special issue), 212-222
Open this publication in new window or tab >>Hydrothermal ageing of polylactide/sisal biocomposites: Studies of water absorption behaviour and Physico-Chemical performance
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2014 (English)In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 108, no special issue, p. 212-222Article in journal (Refereed) Published
Abstract [en]

An accelerated hydrothermal degrading test was designed in order to analyse the synergic effect of water and temperature on PLA/sisal biocomposites with and without coupling agent. As well, the physicochemical properties of biocomposites were monitored along the hydrothermal test by means of Scanning Electron Microscopy, Size Exclusion Chromatography and Differential Scanning Calorimetry. The addition of fibre induced higher water absorption capability and promoted physical degradation, as observed in the surface topography. During the processing of biocomposites and throughout the hydrothermal ageing, a reduction of molecular weight due to chain scission was found. As a consequence, a faster formation of crystalline domains in the PIA matrix occurred the higher the amount of fibre was, which acted as a nucleating agent. Higher crystallinity was considered as a barrier against the advance of penetrant and a reduction in the diffusion coefficient was shown. The addition of coupling agent presented a different influence depending on the composition, showing an inflection point around 20% of sisal fibre. (C) 2014 Elsevier Ltd. All rights reserved.

Place, publisher, year, edition, pages
Elsevier, 2014
Keywords
Biocomposites, Polylactide (PLA), Natural fibres, Sisal, Hydrothermal, degradation, Water absorption
National Category
Polymer Technologies
Identifiers
urn:nbn:se:his:diva-16609 (URN)10.1016/j.polymdegradstab.2014.06.010 (DOI)000343380800026 ()2-s2.0-84903221897 (Scopus ID)
Conference
4th International Conference on Biodegradable and Biobased Polymers (BIOPOL), OCT 01-03, 2013, Univ Perugia, Rome, ITALY
Available from: 2019-02-08 Created: 2019-02-08 Last updated: 2019-11-26Bibliographically approved
Badia, J. D., Kittikorn, T., Strömberg, E., Santonja-Blasco, L., Martínez-Felipe, A., Ribes-Greus, A., . . . Karlsson, S. (2014). Water absorption and hydrothermal performance of PHBV/sisal biocomposites. Paper presented at 4th International Conference on Biodegradable and Biobased Polymers (BIOPOL), OCT 01-03, 2013, Univ Perugia, Rome, ITALY. Polymer degradation and stability, 108, 166-174
Open this publication in new window or tab >>Water absorption and hydrothermal performance of PHBV/sisal biocomposites
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2014 (English)In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 108, p. 166-174Article in journal (Refereed) Published
Abstract [en]

The performance of biocomposites of poly(hydroxybutyrate-co-valerate) (PHBV) and sisal fibre subjected to hydrothermal tests at different temperatures above the glass transition of PHBV (T-H = 26, 36 and 46 degrees C) was evaluated in this study. The influences of both the fibre content and presence of coupling agent were focused. The water absorption capability and water diffusion rate were considered for a statistical factorial analysis. Afterwards, the physico-chemical properties of water-saturated biocomposites were assessed by Fourier-Transform Infrared Analysis, Size Exclusion Chromatography, Differential Scanning Calorimetry and Scanning Electron Microscopy. It was found that the water diffusion rate increased with both temperature and percentage of fibre, whereas the amount of absorbed water was only influenced by fibre content. The use of coupling agent was only relevant at the initial stages of the hydrothermal test, giving an increase in the diffusion rate. Although the chemical structure and thermal properties of water-saturated biocomposites remained practically intact, the physical performance was considerably affected, due to the swelling of fibres, which internally blew-up the PHBV matrix, provoking cracks and fibre detachment. (C) 2014 Elsevier Ltd. All rights reserved.

Place, publisher, year, edition, pages
Elsevier, 2014
Keywords
Hydrothermal degradation, Biocomposites, Poly(hydroxybutyrate-co-valerate) (PHBV), Lignocellulosic fibres, Sisal, Statistical factorial analysis (SFA)
National Category
Polymer Technologies
Identifiers
urn:nbn:se:his:diva-16608 (URN)10.1016/j.polymdegradstab.2014.04.012 (DOI)000343380800020 ()2-s2.0-84956613223 (Scopus ID)
Conference
4th International Conference on Biodegradable and Biobased Polymers (BIOPOL), OCT 01-03, 2013, Univ Perugia, Rome, ITALY
Available from: 2019-02-08 Created: 2019-02-08 Last updated: 2019-11-26Bibliographically approved
Kittikorn, T., Strömberg, E., Ek, M. & Karlsson, S. (2013). Comparison of water uptake as function of surface modification of empty fruit bunch oil palm fibres in PP biocomposites. BioResources, 8(2), 2998-3016
Open this publication in new window or tab >>Comparison of water uptake as function of surface modification of empty fruit bunch oil palm fibres in PP biocomposites
2013 (English)In: BioResources, ISSN 1930-2126, Vol. 8, no 2, p. 2998-3016Article in journal (Refereed) Published
Abstract [en]

Empty fruit bunch oil palm (EFBOP) fibres were surface modified by four different methods, propionylation, vinyltrimethoxy silanization, PPgMA dissolution modification, and PPgMA blending, and integrated into a polypropylene (PP) matrix. The designed biocomposites were subjected to an absorption process at different temperatures. Their water uptake behaviour was compared with the unmodified fibre biocomposites. An increased fibre content and temperature resulted in increased water uptake for all of the biocomposites. The biocomposites containing modified fibres showed a reduction in water uptake, rate of diffusion, sorption, and permeation in comparison with unmodified fibre composites. Comparing the 20 wt% fibre composites at ambient temperature, the performance in water absorption followed the sequence silanization < propionylation < PPgMA dissolution modification < PPgMA blending < no modification. Furthermore, the lowest water absorption was obtained from the silanized fibre/PP composite with 40% fibre content at ambient temperature. Dissolution or blending of PPgMA gave similar water uptake results. The reduction of diffusion, sorption, and permeation confirmed that the modification of fibres was potentially effective at resisting water penetration into the composites.

Place, publisher, year, edition, pages
College of Natural Resources, 2013
Keywords
Biocomposite, Fibre modification, Oil palm fibre, Polypropylene, Water
National Category
Polymer Technologies
Research subject
Natural sciences
Identifiers
urn:nbn:se:his:diva-8928 (URN)000320185500073 ()2-s2.0-84877933255 (Scopus ID)
Note

Source: Scopus

Available from: 2014-03-11 Created: 2014-03-11 Last updated: 2017-11-27Bibliographically approved
Moriana, R., Vilaplana, F., Karlsson, S. & Ribes-Greus, A. (2011). Improved thermo-mechanical properties by the addition of natural fibres in starch-based sustainable biocomposites. Composites. Part A, Applied science and manufacturing, 42(1), 30-40
Open this publication in new window or tab >>Improved thermo-mechanical properties by the addition of natural fibres in starch-based sustainable biocomposites
2011 (English)In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 42, no 1, p. 30-40Article in journal (Refereed) Published
Abstract [en]

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.

Keywords
Polymer-matrix composites (PMCs), Thermomechanical, Electron microscopy, Thermal analysis, Bio-composites, Biofibres, Cotton fibres, Decomposition temperature, Mater-Bi, Mechanical performance, Morphological properties, Natural fibre, Starch-based, Storage moduli, Sustainable bio-composites, Thermal analysis, Thermal decomposition process, Thermal stability, Thermal stabilizers, Thermo-mechanical, Thermomechanical properties, Thermoplastic starch, Cotton, Cotton fibers, Glass transition, Hemp, Polymer matrix composites, Polypropylenes, Pyrolysis, Starch, Thermoanalysis, Thermodynamic stability, Mechanical properties, Composites, Electron Microscopy, Glass Transition Temperature, Polypropylene
National Category
Polymer Chemistry Materials Chemistry
Identifiers
urn:nbn:se:his:diva-15888 (URN)10.1016/j.compositesa.2010.10.001 (DOI)000285902300005 ()2-s2.0-78650223590 (Scopus ID)
Available from: 2018-06-29 Created: 2018-06-29 Last updated: 2018-08-14Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-5394-7850

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