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Xyloglucan-based polymers and nanocomposites – modification, properties and barrier film applications
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Biopolymers from renewable resources are of interest for packaging applications as an alternative to conventional petroleum-based polymers. One of the major application areas for biopolymers is food packaging, where a candidate polymer should meet critical requirements such as mechanical and oxygen barrier performance, also in humid conditions. Starch has long been used in certain packaging applications, either in plasticized state or blended with other polymers. However, native starch has high sensitivity to water and low mechanical and barrier performance. Recently, wood-derived hemicelluloses have been extensively studied as oxygen barrier films, but suffer from low film-forming ability and mechanical performance. In the present study, xyloglucan (XG) from tamarind seed waste is explored as an alternative high-performance biopolymer in packaging applications. The obstacles of polysaccharides in terms of moisture sensitivity and processability are addressed in this thesis.

In Paper I, film properties of XG were studied. XG has a cellulose backbone, but unlike cellulose, it is mostly soluble in water forming highly robust films. Moisture sorption isotherms, tensile tests and dynamic mechanical thermal analysis were performed. Enzymatic modification (partial removal of galactose in side chains of XG) was performed to study the effect of galactose on solubility and filmforming characteristics. XG films showed lower moisture sorption than starch. Stiffness and tensile strength were very high of the order of 4 GPa and 70 MPa respectively, with considerable ductility and toughness. The thermomechanical performance was very high with a softening temperature near 260 ºC.

In Paper II, several plasticizers were studied in order to facilitate thermal processing of XG films: sorbitol, urea, glycerol and polyethylene oxide. Films of different compositions were prepared and studied for thermomechanical and tensile properties. Highly favorable characteristics were found with XG/sorbitol system. A large drop in glass transition temperature (Tg) of XG of the order of 100 ºC with 20 - 30 wt% sorbitol was observed with an attractive combination of increased toughness.

In Paper III, XG was chemically modified and the structure-property relationship of modified XG studied. XG modification was performed using an approach involving periodate oxidation followed by reduction. The oxidation is highly regioselective, where the side chains of XG are mostly affected with the cellulose backbone well-preserved as noticed from MALDI-TOF-MS and carbohydrate analysis. Films were cast from water and characterized by dynamic mechanical thermal analysis, dynamic water vapor sorption, oxygen transmission analysis and tensile tests. Property changes were interpreted from structural changes. The regioselective modification results in new types of cellulose derivatives without the need for harmful solvents.

In Paper IV, moisture durability of XG was addressed by dispersing montmorillonite (MTM) platelets in water suspension. Oriented bionanocomposite coatings with strong in-plane orientation of clay platelets were prepared. A continuous water-based processing approach was adopted in view of easy scaling up. The resulting nanocomposites were characterized by FE-SEM, TEM, and XRD. XG adsorption on MTM was measured by quartz crystal microbalance analysis. Mechanical and gas barrier properties were measured, also at high relative humidity. The reinforcement in mechanical properties and effects on barrier properties were remarkable, also in humid conditions.

In Paper V, cross-linked XG/MTM composite was prepared with high clay content (ca. 45 vol%) by an industrially scalable “paper-making” method. Instead of using cross-linking molecules, cross-linking sites were created on the XG chain by selective oxidation of side chains. The in-plane orientation of MTM platelets were studied using XRD and FE-SEM. The mechanical properties and barrier performance were evaluated for the resulting 'nacre-mimetic' nanocomposites. The elastic modulus of cross-linked nanocomposites is as high as 30 GPa, one of the stiffest bionanocomposites reported.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , ix, 61 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2012:53
Keyword [en]
xyloglucan, packaging, oxygen barrier, nanocomposites
National Category
Polymer Technologies
Identifiers
URN: urn:nbn:se:kth:diva-107043ISBN: 978-91-7501-528-6 (print)OAI: oai:DiVA.org:kth-107043DiVA: diva2:574579
Public defence
2012-12-21, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20121107

Available from: 2012-12-07 Created: 2012-12-06 Last updated: 2012-12-07Bibliographically approved
List of papers
1. Tamarind seed xyloglucan: a thermostable high-performance biopolymer from non-food feedstock
Open this publication in new window or tab >>Tamarind seed xyloglucan: a thermostable high-performance biopolymer from non-food feedstock
2010 (English)In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 20, no 21, 4321-4327 p.Article in journal (Refereed) Published
Abstract [en]

Polysaccharide biopolymers from renewable resources are of great interest as replacements for petroleum-based polymers since they have lower cradle-to-grave non-renewable energy use and greenhouse gas emissions. Starch is widely used as a packaging material but is based on food resources such as potato or corn, and suffers from high sensitivity to water vapor even under ambient conditions. For the first time, xyloglucan (XG) from tamarind seed waste is explored as an alternative high-performance biopolymer from non-food feedstock. XG is purified, and dissolved in water to cast films. Moisture sorption isotherms, tensile tests and dynamic mechanical thermal analysis are performed. Glycerol plasticization toughening and enzymatic modification (partial removal of galactose in side chains of XG) are attempted as means of modification. XG films show much lower moisture sorption than the amylose component in starches. Stiffness and strength are very high, with considerable ductility and toughness. The thermal stability is exceptionally high and is approaching 250 degrees C. Glycerol plasticization is effective already at 10% glycerol. These observations point towards the potential of XG as a "new'' biopolymer from renewable non-food plant resources for replacement of petroleum-based polymers.

Keyword
Ambient conditions, Cast film, Dynamic mechanical thermal analysis, Enzymatic modification, Food plants, Food resources, High sensitivity, Moisture sorption, Moisture sorption isotherms, Non-renewable energy, Renewable resource, Side chains, Tensile tests, Thermal stability, Xyloglucans
National Category
Physical Chemistry Materials Engineering
Identifiers
urn:nbn:se:kth:diva-27854 (URN)10.1039/c0jm00367k (DOI)000277832700008 ()2-s2.0-77952522070 (Scopus ID)
Note
QC 20110112Available from: 2011-01-12 Created: 2011-01-03 Last updated: 2017-12-11Bibliographically approved
2. Plasticized xyloglucan for improved toughness-Thermal and mechanical behaviour
Open this publication in new window or tab >>Plasticized xyloglucan for improved toughness-Thermal and mechanical behaviour
2012 (English)In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 87, no 4, 2532-2537 p.Article in journal (Refereed) Published
Abstract [en]

Tamarind seed xyloglucan is an interesting polysaccharide of high molar mass with excellent thermomechanical properties. Several plasticizers were studied in order to facilitate thermal processing and improve toughness (work to fracture) of xyloglucan film materials: sorbitol, urea, glycerol and polyethylene oxide. Films of different compositions were cast and studied by thermogravimetric analysis (TGA), calorimetry (DSC), dynamic mechanical thermal analysis (DMA) and tensile tests. Results are analysed and discussed based on mechanisms and practical considerations. Highly favourable characteristics were found with XG/sorbitol combinations, and the thermomechanical properties motivate further work on this material system, for instance as a matrix in biocomposite materials.

Place, publisher, year, edition, pages
Elsevier, 2012
Keyword
Glass transition, Mechanical properties, Plasticization, Polymer films, Xyloglucan
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-90895 (URN)10.1016/j.carbpol.2011.11.024 (DOI)000299969800023 ()2-s2.0-84865653433 (Scopus ID)
Note

QC 20150716

Available from: 2012-03-07 Created: 2012-03-05 Last updated: 2017-12-07Bibliographically approved
3. Regioselective modification of a xyloglucan hemicellulose for high-performance biopolymer barrier films
Open this publication in new window or tab >>Regioselective modification of a xyloglucan hemicellulose for high-performance biopolymer barrier films
2013 (English)In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 93, no 2, 466-472 p.Article in journal (Refereed) Published
Abstract [en]

Biobased polymers such as starch and hemicelluloses from wood are of interest for packaging applications, but suffer from limitations in performance under moist conditions. Xyloglucan from industrial tamarind seed waste offers potential, but its Tg is too high for thermal processing applications. Regioselective modification is therefore performed using an approach involving periodate oxidation followed by reduction. The resulting polymer structures are characterized using MALDI-TOF-MS, size-exclusion chromatography, FTIR and carbohydrate analysis. Films are cast from water and characterized by thermo-gravimetry, dynamic mechanical thermal analysis, dynamic water vapor sorption, oxygen transmission and tensile tests. Property changes are interpreted from structural changes. These new polymers show much superior performance to current petroleum-based polymers in industrial use. Furthermore, this regioselective modification can be carefully controlled, and results in a new type of cellulose derivatives with preserved cellulose backbone without the need for harmful solvents.

Keyword
Xyloglucan, Oxygen barrier, Packaging, Periodate oxidation, Cellulose derivatives
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-107057 (URN)10.1016/j.carbpol.2012.12.041 (DOI)000317148200015 ()2-s2.0-84874167776 (Scopus ID)
Note

QC 20130514. Updated from accepted to published.

Available from: 2012-12-06 Created: 2012-12-06 Last updated: 2017-12-07Bibliographically approved
4. Bioinspired and highly oriented clay nanocomposites with a xyloglucan biopolymer matrix: Extending the range of mechanical and barrier properties
Open this publication in new window or tab >>Bioinspired and highly oriented clay nanocomposites with a xyloglucan biopolymer matrix: Extending the range of mechanical and barrier properties
Show others...
2013 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 14, no 1, 84-91 p.Article in journal (Refereed) Published
Abstract [en]

The development of clay bionanocomposites requires processing routes with nanostructural control. Moreover, moisture durability is a concern with water-soluble biopolymers. Here, oriented bionanocomposite coatings with strong in-plane orientation of clay platelets are for the first time prepared by continuous water-based processing. Montmorillonite (MTM) and a "new" unmodified biological polymer (xyloglucan (XG)) are combined. The resulting nanocomposites are characterized by FE-SEM, TEM, and XRD. XG adsorption on MTM is measured by quartz crystal microbalance analysis. Mechanical and gas barrier properties are measured, also at high relative humidity. The reinforcement effects are modeled. XG dimensions in composites are estimated using atomistic simulations. The nanostructure shows highly oriented and intercalated clay platelets. The reinforcement efficiency and effects on barrier properties are remarkable and are likely to be due to highly oriented and well-dispersed MTM and strong XG-MTM interactions. Properties are well preserved in humid conditions and the reasons for this are discussed.

Keyword
xyloglucan, nanocomposites, packaging, oxygen barrier
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-107058 (URN)10.1021/bm301382d (DOI)000313605800010 ()2-s2.0-84872567228 (Scopus ID)
Note

QC 20130213. Updated from accepted to published.

Available from: 2012-12-06 Created: 2012-12-06 Last updated: 2017-12-07Bibliographically approved
5. Nacre-mimetic xyloglucan/clay bionanocomposites prepared from hydrocolloidal suspension – a chemical modification route for preserved performance at high humidity
Open this publication in new window or tab >>Nacre-mimetic xyloglucan/clay bionanocomposites prepared from hydrocolloidal suspension – a chemical modification route for preserved performance at high humidity
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-107059 (URN)
Note

QS 2012

Available from: 2012-12-06 Created: 2012-12-06 Last updated: 2012-12-07Bibliographically approved

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