AEROWOOD Wood-based aerogels

Transcription

1 Bodo Saake, University of Hamburg, Centre for Wood Science / WoodWisdom-Net Seminar Edinburgh 4-5 April 2017 AEROWOOD Wood-based aerogels DIO YOU

2 What and why? The AEROWOOD project studied ways to prepare novel highly porous and lightweight aerogel materials derived from all wood components % Lignin 25 35% Lignin 25 35% Hemicelluloses 25 30% Hemicelluloses 40 50% Cellulose 40 50% Cellulose

3 Who? WoodWisdom-Net Seminar Edinburgh 4-5 April 2017 Project partners Partner 1: Prof. Maija Tenkanen, University of Helsinki, Finland (coordinator) Partner 2: Dr. Falk Liebner, BOKU, Austria Partner 3: Dr. Tatiana Budtova, CEMEF, France Partner 4: Prof. Bodo Saake, University of Hamburg, Germany Partner 5: Dr. Uroš Maver, University of Maribor, Slovenia MOBILITIES Funding: COST FP1105 COST FP1205 COST FP1405

4 Project highlights and final results WP1 Material collection, isolation and modification Modification of xylan with cyclic organic carbonates improves gelation and enables crosslinking 2 µm

5 Project highlights and final results WP2 Cellulose- and wood-based aerogels From milled wood chips (poplar, beech) to highly porous and light weight all-wood materials, via green processing (no toxic compound used): Cellulose was used to make porous matrices: - with controlled and various morphologies, - densities g/cm 3 - specific surface areas m 2 /g 2 µm Aerogel from wood Aerogel and cryogel from cellulose Cellulose aerogels are not breaking under compression, even under 80% strain. Before compression After compression

6 Project highlights and final results WP2 Cellulose- and wood-based aerogels Oxidatively modified nanofibrillated cellulose undergoes self-alignment in slightly alkaline medium. Nematic liquid-crystalline orientation can be set by acid-induced gelation. Replacement of water by ethanol and subsequent scco 2 transparent, ultra-lightweight, robust and open-porous aerogels. drying affords Grafting of amino-functionalized carbon dots and quantum dots onto the internal surface of aerogels results in active elements that can be switched from invisible off to luminescent on state by laser beams. The obtained matrices are very promising with regard to the development of cellulose-based static true volumetric displays.

7 Project highlights and final results WP3 Hemicellulose derived hydrogels and aerogels Spruce galactoglucomannans and birch glucuronoxylans were crosslinked to form hydrogels with nanocellulose. Lightweight and strong aerogels with sponge properties were obtained by freeze-drying. Enzymatically crosslinked galactomannan - nanocellulose gels in solvent were scco 2 dried to obtain mesoporous aerogels with high specific surface area. Synchrotron x-ray microtomography used to reveal the 3D inner structure of freezedried aerogels. Addition of nanocellulose decreased the pore size, and adjusting the freezing direction aligned the pores.

8 Shrinkage [%] WoodWisdom-Net Seminar Edinburgh 4-5 April 2017 Project highlights and final results WP4 Lignin-based aquogels, aerogels and carbon aerogels Preparation of self-standing lignin-alginate hydrogels, aerogels and carbogels by physical cross-linking of ammonia lignosulfonate and alginic acid (beads, discs, cylinders) The obtained lightweight aerogels (r B 100 mg cm -3 ) and carbon aerogels feature an open-nanoporous morphology characterized by high specific surface (aerogels: S BET 287 m 2 g -1 ; carbon aerogels (274 m 2 g -1 )....from lignosulfonate alginate (AL) composite hydrogels to aerogels and carbon aerogels Shrinkage during gelation freeze-drying 500 µm scco 2 -drying 0,1M HCl + 0,1M CaCl 2 1M HCl + 0,1M CaCl 2 1M HCl 50 µm SEM picture of carbon aerogels derived from AL=1:2 aerogels A:L ratio coagulation medium 0.1M HCl 1M HCl 1M HCl 0.1M CaCl 2 0.1M CaCl 2

9 Project highlights and final results: WP5 Application potentials of aerogels in packaging and health care Hemicellulose aerogels were tested for active release of hexanal to extend the shelf life of fruit by slowing down ripening and preventing microbial growth. Sunflower oil with enzymes was encapsulated in the aerogels. Constant hexanal production was achieved through enzymatic oxidation. Avocado packaging with aerogel designed by students

10 Project highlights and final results: WP5 Application potentials of aerogels in in packaging and health care Cellulose and hemicellulose aerogels were characterized as biocompatible drug release and cell growth media for wound healing and tissue engineering.

11 Expected impact and target groups The project contributes to the development of bioeconomy by the new technology that exploits wood-based resources. The produced transparent aerogels from cellulose open new fields of applications in biosensing, bioimaging, photovoltaics, thermal superinsulation, and true volumetric displays. Hemicellulose aerogels are promising as active packaging to extend the shelf-life of packed fruit. Substitution of hazardous epoxides by safer cyclic organic carbonates is possible for the derivatization of various biopolymers. The main target groups to be addressed with the project outcomes are pulp and paper companies in the view of biorefinery approach. Other important target groups are the food, packaging, and pharmaceutical industries. Future collaborations with physicists and companies working on display development are intended.

12 Lessons learnt and open questions Wood cellulose, hemicellulose, lignin, and milled wood was reformulated into new lightweight materials, aerogels. Self-aligned nematic phases of nanocellulose can be preserved throughout solvent exchange and scco 2 drying. The low molar mass of hemicelluloses requires a high content of cocomponents to form aerogels. Vinyl-functionalized hemicelluloses can be crosslinked without other co-components. Recycling of ionic liquids needed to dissolve wood is still under development. Can crosslinking of vinyl groups compensate the low molar mass of hemicelluloses Safe, effective and biocompatible crosslinking agents are needed. Can transparency, durability and mechanical properties be further improved by reinforcement / modification strategies For true static volumetric displays, the response of the cellulosic network towards NIR laser irradiation requires thorough investigation. The impact of birefringence of the nematic scaffold on the quality of the created 3D images (resolution) needs to be calculated.