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Closed-loop strategy for valorization of starch: From starch to functionalized starch biomaterials and bioplastics
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The desire to utilize renewable resources and avoid wastes drives us to develop new concepts for material design. Non-edible starch feedstocks and starch bioplastic wastes were previously considered useless. However, with a proper design and process chain, starch-rich biomasses are a promising resource for production and modification of future materials. Therefore, a top-down and closed-loop strategy for valorization of starch through a circle consisting of “StarchÞEnhancerÞNew starch product” is developed and demonstrated in this work. Starch, as a model for starch rich waste resources, was converted into valuable chemicals or carbon products through a two-step decomposition. The valorization products were then utilized as property enhancers in starch-rich biomaterials and bioplastics through design of “structure adapted utilization”: i.e., the obtained products were included in the design of starch-rich products aiming at property enhancement or introduction of new properties. This leads to the closed-loop strategy for valorization of starch.

Through a two-step processing, starch was converted into two categories of value-added products: water soluble degradation products (mixture of glucose, levulinic acid (LA) and formic acid (FA)), and 0D nano-graphene oxide (nGO, smaller than 100 nm in all dimension). Specifically, in step one, through acid-catalyzed microwave-assisted reaction; starch was converted to a mixture of glucose, LA and FA in soluble phase and carbon spheres (C-spheres) as a solid residue phase. In step two, the insoluble C-spheres were further oxidized under oxygen-rich acidic conditions to obtain multifunctional nGO.

Through “structure adapted utilization”, four routes were designed to efficiently utilize the two categories of value-added products as functional enhancers for new starch-rich products. On one hand, starch-derived biomedical scaffolds were developed in route 1 and 2: nGO could stabilize porous 3D starch scaffolds (route 1) and starch nanofibrous scaffolds (route 2), and meanwhile endorse them the ability to induce biomineralization. On the other hand, starch-rich (and fully starch-derivable) bioplastics were developed in route 3 and 4: nGO effectively compatibilized poly lactic acid/starch composites enhancing the mechanical performance and barrier properties (route 3) and the water soluble degradation products plasticized starch films reducing their brittleness (route 4).

Along this closed-loop pathway, the material value of starch was significantly improved and minimum waste was derived, paving towards the sustainable environment and circular economy. 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017. , 60 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2017:22
Keyword [en]
Starch, Nano-graphene oxide, Microwave, Valorization, Scaffold, Biomineralization, Bioplastics, Compatibilizer, Plasticizer
National Category
Materials Engineering Medical Materials Medical and Health Sciences
Research subject
Fibre and Polymer Science
Identifiers
URN: urn:nbn:se:kth:diva-208188ISBN: 978-91-7729-341-5 (print)OAI: oai:DiVA.org:kth-208188DiVA: diva2:1104810
Public defence
2017-05-05, F3, Lindstedtsvägen 26, 10:00
Opponent
Supervisors
Note

QC 20170602

Available from: 2017-06-02 Created: 2017-06-01 Last updated: 2017-06-02Bibliographically approved
List of papers
1. A Closed-Loop Process from Microwave-Assisted Hydrothermal Degradation of Starch to Utilization of the Obtained Degradation Products as Starch Plasticizers
Open this publication in new window or tab >>A Closed-Loop Process from Microwave-Assisted Hydrothermal Degradation of Starch to Utilization of the Obtained Degradation Products as Starch Plasticizers
2014 (English)In: ACS Sustainable Chemistry and Engineering, ISSN 2168-0485, Vol. 2, no 9, 2172-2181 p.Article in journal (Refereed) Published
Abstract [en]

A green closed-loop water-based process for chemical recycling of starch was demonstrated. The process starts from microwave-assisted controllable starch degradation to functional chemicals and continues to utilization of the formed degradation products, glucose and levulinic acid (LA), as starch plasticizers. The degradation process and the effect of process parameters on the formed degradation products and residues were carefully fingerprinted by multiple techniques, e.g., NMR, ESI-MS, FTIR imaging, UV-vis, and SEM. The degradation process took place in three steps, proceeding from rupture of starch granules and oligosaccharide formation to further hydrolysis to glucose. Finally, at well-defined time point rapid degradation of glucose to LA and formic acid (FA) was initiated through a 5-hydroxymethyl furfural (5-HMF) intermediate. 5-HMF also participated in carbonization reactions leading to formation of solid carbon spheres. Through selection of processing parameters, LA could be produced in high yield with 9596 selectivity. The results demonstrated that microwave-assisted degradation of starch leads to well-defined controllable degradation products. These products are directly reusable as plasticizers for new starch products, which suggest great opportunities for biomass and starch recycling, opening the door toward potential industrial applications.

Keyword
Hydrothermal degradation, Levulinic acid, Microwave, Plasticizer, Recycling, Starch
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-152562 (URN)10.1021/sc500355w (DOI)000341229100012 ()2-s2.0-84906880167 (ScopusID)
Note

QC 20140929

Available from: 2014-09-29 Created: 2014-09-29 Last updated: 2017-06-02Bibliographically approved
2. From starch to polylactide and nano-graphene oxide: fully starch derived high performance composites
Open this publication in new window or tab >>From starch to polylactide and nano-graphene oxide: fully starch derived high performance composites
2016 (English)In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 6, no 59, 54336-54345 p.Article in journal (Refereed) Published
Abstract [en]

A delicate closed-loop strategy for valorization of starch to value-added products was developed. Carbon sheets, formed of carbon spheres, were obtained by microwave-assisted hydrothermal degradation of starch and then further transformed into nano-sized graphene oxide (nGO, 20 x 30 nm(2)) under oxygen-rich acidic conditions. The synthesized nGO exhibited self-assembly in solution. Furthermore, nGO strongly attached to the surface of starch granules by hydrogen bonding (nGO@ starch, 0.1 wt%) and allowed easy and highly efficient interfacial engineering in PLA/starch composites. After combining with polylactide (PLA), the composites could incorporate up to 30 wt% nGO@ starch, while retaining excellent properties. nGO was capable of facilitating PLA crystallization in the composites by providing a number of nucleation sites. Moreover, the interfacial adhesion between PLA and starch was significantly improved by nGO. Though its content was extremely low, nGO improved the mechanical and barrier properties and thermal stability of the PLA/starch composites. The results demonstrate a facile route to value-added starch-derived nGO and further to fully starch derived high performance PLA/starch biocomposites.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2016
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-189959 (URN)10.1039/c6ra08194k (DOI)000378521400091 ()2-s2.0-84973614832 (ScopusID)
Note

QC 20160727

Available from: 2016-07-27 Created: 2016-07-25 Last updated: 2017-06-02Bibliographically approved
3. Recycling PLA to multifunctional oligomeric compatibilizers for PLA/starch composites
Open this publication in new window or tab >>Recycling PLA to multifunctional oligomeric compatibilizers for PLA/starch composites
2015 (English)In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 64, 126-137 p.Article in journal (Refereed) Published
Abstract [en]

Simple one-pot valorization of poly(lactic acid) (PLA) to green additives was demonstrated. PLA was thermally recycled in the presence of polyols, which accelerated the degradation process by reacting with PLA chains. As a result low molecular weight oligomers with polyols end-groups were formed. The reaction between PLA and multifunctional alcohols i.e. glycerol, sorbitol, glucose and starch were confirmed by FTIR, H-1 NMR, SEC and MALDI-MS. The resulting amphiphilic products were evaluated as compatibilizer candidates for PLA/starch blends. Multiple techniques demonstrated that the obtained oligomers strengthened the interfacial adhesion and improved the compatibility and flexibility of extruded and melt-blended PLA/starch composites. The developed one-pot procedure required no solvent or catalyst offering good possibilities for up-scaling. It was, thus, demonstrated that PLA can be recycled to low molecular weight compatibilizers by simple process of thermal heating in the presence of polyols. This provides profound promise for retaining the material value of old PLA products at the same time as biobased additives are produced.

Keyword
Poly (lactic acid), Starch, Polyol, Composites, Compatibilizer, Recycling
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-163454 (URN)10.1016/j.eurpolymj.2015.01.004 (DOI)000350525100013 ()2-s2.0-84921263297 (ScopusID)
Note

QC 20150408

Available from: 2015-04-08 Created: 2015-04-07 Last updated: 2017-06-02Bibliographically approved

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