Improvement of water sensitivity, mechanical properties and utilization of hemicellulose based polymeric materials

Akkuş, Merve
Hemicelluloses are sustainable resources of biopolymers with a huge potential to be converted into materials substituting petroleum-based products, but their hydrophilic characteristics pose a challenge to their industrial adoption. The main aim of this study is to decrease the water sensitivity of alkaline extracted xylan-based corn cob hemicelluloses (xylans) by heat-treatment and acetylation also by addressing their extrusion processing with sorbitol, glycerol and blends. Heat-treatment resulted in extruded strips with less moisture uptake, less normalized water vapor transfer rate (NWVTR) and enhanced mechanical properties, but without any significant change in their water solubilities. Acetylation was studied by exploiting the potassium acetate (KAc) salt that is formed during the alkaline extraction, which is usually removed. Moisture uptake, water solubility, and NWVTR of KAc containing acetylated xylans decreased significantly, with an increase in mechanical properties and thermal stability, showing that acetylation with KAc is an efficient method without salt purification steps and toxic catalysts like pyridine. Extrusion of xylans with sorbitol and glycerol was studied alternative to the plasticization by moisture conditioning where both plasticizers rendered xylans extrudable. Similar to the effect of KAc, vi acetylation carried out in the presence of sorbitol and glycerol resulted in reduced water solubilities; however the mechanical properties were only enhanced for glycerol containing strips. Xylan-and-polyvinyl alcohol (PVA) blends and their heat treatment and acetylation were also studied to reduce their water sensitivity. Extrusion of xylan/PVA blends was successful which might increase the industrial utilization of xylans, but their heat treatment and acetylation resulted in brittle strips


Environmental transformation and nano-toxicity of engineered nano-particles (ENPs) in aquatic and terrestrial organisms
Abbas, Qumber; Yousaf, Balal; Ullah, Habib; Ali, Muhammad Ubaid; Ok, Yong Sik; Rinklebe, Joerg (2020-12-01)
The rapid development in nanotechnology and incorporation of engineered nano-particles (ENPs) in a wide range of consumer products releasing the massive quantities of ENPs in different environmental compartments. The released ENPs from nano-enabled products during their life cycle raising environmental health and safety issues. This review addresses the recent state of knowledge regarding the ENPs ecotoxicity to various organisms lying at different trophic levels. Studies show that reactive oxygen species (...
Investigation Of Influencing Factors For Biological Hydrogen Production By R. Capsulatus In Tubular Photo-Bioreactors
Boran, E.; Ozgur, E.; Gebicki, J.; van der Burg, J.; YÜCEL, MUSTAFA; Gündüz, Ufuk; Modigel, M.; Eroglu, I. (2009-05-13)
Biological hydrogen production processes are considered as an environmentally friendly way to produce hydrogen. They offer the chance to produce hydrogen from renewable energy sources, like sunlight and biomass. This study aims the process development for a photo-fermentative hydrogen production by photosynthetic purple-non-sulfur bacteria, Rhodobacter capsulatus, in a large scale (80L) tubular photo-bioreactor, in outdoor conditions, using acetate as carbon source. It was shown that Rhodobacter capsulatus ...
Biohydrogen production from barley straw hydrolysate through sequential dark and photofermentation
Ozgur, Ebru; Peksel, Begum (Elsevier BV, 2013-08-01)
Biohydrogen production by sequential operation of dark and photo-fermentation processes is a promising method to produce hydrogen from renewable resources, in a sustainable way. In this study, barley straw hydrolysate (BSEI) dark fermenter effluent (DFE) was used as the biomass feedstock for biohydrogen production through photofermentation. Two different dark fermentation effluents were obtained by performing fermentation with or without addition of yeast extract (YE), using hyperthermophilic dark fermentat...
Novel investigation of pyrolysis mechanisms and kinetics for functional groups in biomass matrix
Liu, Ruijia; Liu, Guijian; Yousaf, Balal; Niu, Zhiyuan; Abbas, Qumber (2022-01-01)
Biomass, as a renewable and sustainable energy resource, can be converted into environmentally friendly and practically valuable biofuels and chemical materials via pyrolysis. However, the process optimization and pyrolysis efficiency are restricted by the limited perception of the complicated mechanisms and kinetics for biomass pyrolysis. Here, to establish an in-depth mechanism model for biomass pyrolysis, we presented a novel investigation for the thermal evolutions and pyrolysis kinetics of the function...
Organic bulk heterojunction solar cells based on benzodithiophene and benzothiadiazole containing conjugated polymers
Toppare, Levent Kamil; Bolayır, Eda; Ünal, Özlem; Çırpan, Ali; Taşkaya Aslan, Sultan (null; 2018-07-06)
Organic photovoltaics (OPVs) or so-called organic solar cells particularly hold promise for manufacturing solar energy due to their advantages in low cost and production processes. In order to understand and improve the performance of OPVs, intense efforts have been dedicated around the world [1]. In particular, conjugated polymers are attractive for OPVs due to the π-conjugated systems in the polymer backbone which generates and transport the charge carriers [2]. Therefore, the design and synthesis of nove...
Citation Formats
M. Akkuş, “Improvement of water sensitivity, mechanical properties and utilization of hemicellulose based polymeric materials,” Ph.D. - Doctoral Program, Middle East Technical University, 2015.