Puu Nanotechnology in Forest Biomaterials. Nanocellulose. Monika Österberg

Transcription

1 Puu Nanotechnology in Forest Biomaterials Nanocellulose Monika Österberg

2 Learning objectives You know the difference between NFC, CNC, BC (and MCC) You are familiar with how nanofibrillated cellulose (NFC) is prepared and the typical properties of NFC Including effect of pretreatments on the properties You are familiar with how CNC is prepared You know application possibilities of NFC You are aware of the challenges of NFC

3 What is nanocellulose? Why is it important? How to produce nanocellulose? What are the applications? How can it be modified?

4 What is nanocellulose? Cellulose fibrils or crystals with a diameter of nm. Nanofibrillar cellulose, cellulose nanofibrils (CNF), microfibrillar cellulose, NFC, MFC, cellulose nanofibrils, microfibrillated cellulose, Cellulose nanocrystals, whiskers, CNC, CNX, Bacterial cellulose, BC, BNC Cellulose nanofibrils 30 nm Cellulose nanocrystals Nata-de-coco Bacterial cellulose 2 % unmodified NFC Relevant reading: Klemm et al Angewandte Chemie (2011) 50:5438, Eichhorn, et al. J. Mater. Sci. (2010) 45:1-33 and Siró et al. Cellulose (2010) 17:

5 Why is nanocellulose important? Artificial blood vessel from (bacterial) nanocellulose Material from the forest will save the world Prof. Paul Gatenholm, Chalmers University of Technology, Chalmers magasin, nr 3, Nanocellulose is biodegradable, produced from renewable resources,... From the pulp and paper industry point of view: nanocellulose - a new product to sell or new paper additive Generally: An interesting biomaterial with vast application possibilities that needs to be explored. Monika Österberg

6 A lot of expectations on nanocellulose Tekniikan maailma 9/2013 Pulp can be disintegrated into many uses Tekniikka &Talous 9/2013 Wood replaces oil, Kalevala The new nanocellulose will help Finnish economy Kemia Kemi 1/2013 Monika Österberg Solut kasvavat kudoksiksi NANOSELLUSSA Cells grow to tissue in nanocellulose Kemia Kemi 7/2013

7 How to produce nanocellulose Bottom-up process: Bacterial cellulose Top-down: Nanofibrillated cellulose (NFC), Cellulose nanocrystals (CNC) Monika Österberg

8 Bacterial cellulose (BC) Produced by Acetobacter xylinum Long individual cellulose fibrils (aspect ratio even longer than for nanofibrillar cellulose from wood Homogeneous, pure, free from lignin, pectin and hemicelluloses Dessert Nata de coco Application possibilities: Wound dressing, bone graft material, scaffold for tissue engineering of cartilage and blood vessels (Klemm et al, 2001, Svensson et al 2005, Bodin 2007 Nanocomposites, Nogi, Yano 2005 A wet microbial cellulose pellicle Artificial blood vessel, Gatenholm et al, BioNews, 2009 a) Flexible transparent nanocomposite reinforced with BC (Yano, 2005), b) luminescence of an OLED depostied onto a transparent BC nanocomposite (Nogi, Yano 2008) Monika Österberg

9 From cellulose (wood) fibres to nanofibrillated cellulose NFC: width~ 5-30 nm, length > 1 µm Microfibril consists of amorphous and crystalline regions Fiber: width~ 30 µm, length 1-3 mm Monika Österberg

10 Two different approaches Nanofibrillar cellulose, NFC, microfibrillar cellulose,mfc, cellulose nanofibrils Cellulose fibres (Microcrystalline cellulose, MCC), whiskers, cellulose nanocrystals Mechanical defibrillation Selective hydrolysis Microfibrillated cellulose MFC, Turbak, 1985 Colloidal cellulose Rånby, 1949 Chemical modification + mechanical treatment Saito, 2007/ Wågberg, 2008 Enzymatic + mechanical treatment Pääkkö, 2007 Microcrystalline cellulose Battista, 1962 Nanofibrillar cellulose, NFC Cellulose Whiskers Gray Monika Österberg

11 Properties of nanocellulose Microcrystalline cellulose MCC Microfibrillated/ Nanofibrillated cellulose, NFC Cellulose nanocrystals, CN Length > 1 µm Diameter> 1µm Aspect ratio (L/d) ~1 NOT nanocellulose 1 µm Focus Length > 1 µm Diameter ~5-30 nm Aspect ratio (L/d) ~ Cellulose I + amorphous cellulose Length > nm Diameter ~2-20 nm Aspect ratio (L/d) ~ Only Cellulose I Monika Österberg

12 Cellulose nanofibrils (CNF)/ Nanofibrillated cellulose (NFC) Cellulose nanocrystals (CNC) spagetti rice Monika Österberg

13 Nanofibrillated cellulose Raw material Typical pretreatments Production methods wood potato Wheat straw Wood, agricultural crops and by products e.g. wheat straw, sugar beet pulp, potato pulp, bagasse, banana rachis Enzymatic- Carboxymethylation TEMPO- oxidation Alkalinepretreatment Masuko colloider Grinding, High pressure homogenization, cryo crushing Monika Österberg

14 The wood fibre wall Fibrous structure: Microfibrils formed by cellulose molecules Matrix: Lignin, a strongly cross-linked, soft polymer Hemicellulose The structure is held together by forces between the microfibrils (van der Waals forces, hydrogen bonds) cellulose/hemicellulose/lignin interactions Monika Österberg

15 The pre-treatments Objectives: 1) Reduce energy consumption 2) Produce NFC with specific properties Alkaline pretreatment: To remove lignin Enzymatic: Low concentration (0.02%) of endoglucanaze facilitates fibrillation (Pääkkö et al. Biomacromol. 8 (2007) 1934) Carboxmethylation: Solvent exchange to ethanol/iso-propanol Treatment with monochloroacetic acid in iso-propanol Anionic fibrils are produced In all pretreatments there is risk for degradation of the cellulose Monika Österberg

16 Pre-treatments cont. TEMPO mediated oxidation: Selective oxidation of mainly the primary hydroxyl groups to carboxylic groups. Stable nitroxyl radical (2,2,6,6,- tetramethylpiperidine-1-oxyl, TEMPO) + NaBr and NaOCl Highly anionic, homogeneous NFC is obtained Saito, Isogai et al in Biomacromolecules 8 (2007) 2485 and Biomacromolecules 10 (2009) earlier publ. Monika Österberg

17 Example of production method of MFC using enzymatic pre-treatment Bleached sulphite pulp Homogenisation in Microfluidizer E-W refiner to 30 SR 3 passes large chambers Pre-treatment Enzymatic treatment 5 passes small chambers E-W refiner to 94 SR MFC Source: Mikael Ankerfors, STFI-Packforsk

18 Principal variables in fibrillation Choice of pulp (Hard wood/softwood/non wood, sulphite/sulphate, hemicellulose content, lignin content, acidic group content) Fibres that are easy to beat are usually also easy to fibrillate (e.g. high hemicelluloses or charge content) Pulp pre-treatments (refining, enzymatic treatment, hydrolysis, polymeric additives etc.) Extent of fibrillation is govern by pre-treatment and design of homogenizer/fluidizer/masuko refiner Monika Österberg

19 Effect of pulp charge on WRV Simple truths about beating of pulps applicable to NFC production Increasing the charge increases fibrillation tendency Salt has negative effect Monika Österberg Laine 1996

20 Effect of charge on fibrillation efficiency Monika Österberg

21 Individual fibrils Cryo-TEM AFM Bleached kraft pulp NFC gel Chemically aided disintegration (TEMPO mediated oxidation) 200 nm NFC gel 200 nm Eronen et al. JCIS 2011

22 Conclusions: Fibrillation easy with increased charge Degradation possible Very homogeneous and thin fibrils invisible for the eye Cationic fibrils in H 2 O 200 nm Anionic fibrils in air 200 nm Monika Österberg

23 Properties of nanofibrillated cellulose

24 Influence of shear rate on the viscosity of different MFC concentrations Source: Mikael Ankerfors, STFI-Packforsk MFC gel has a shear thinning (tixotropic) rheological properties Pääkkö et al. 2007

25 Without chemical modifications NFC suspensions are polydisperse height AFM height image, scan size 5 5 µm, data scale 15 nm. Picture by S. Ahola.

26 AFM topography image of NFC height phase Scan size 1 1 µm, Z-range 40 nm Ahola and Österberg Monika Österberg

27 Effect of fibril size and polymers on water binding of NFC suspensions Solids content, 30s 10 % 8 % 6 % 4 % 2 % 0 % 0.2 % NFC suspension (unmodified NFCF10) F1 F2 F4 F6 F10 Fluidizer passes Solids content, 30s 30 % 20 % 10 % 0 % CS 0 mg/g CS 0.5 mg/g CS 25 mg/g Time (s) The smaller the fibrils the more they bind water dewatering challenging (a question about surface area!) Polyelectrolytes can enhance dewatering Taipale et al., Cellulose 2010 Monika Österberg

28 Effect of ph on drainage of NFC suspensions Drainage time [s] ph Monika Österberg Charge affects water binding Taipale et al Cellulose 2010

29 Nanofibril model surface: Water uptake as an effect of ph and charge density Nanofibril film ph 3.5 ph 5 ph 8 Highly charged nanofibril film ph 3.5 ph 5 ph 8 Increasing swelling ph 10 ph 10 Ahola, S., Salmi, J., Johansson, L.-S., Laine, J. and Österberg, M, Biomacromolecules 9, (2008)

30 Adsorption of polymers on nanofibril model surfaces QCM-D Xyloglucan (100 mg/l in 1mM NaHCO 3 / 1 mm NaCl) PDADMAC (100 mg/l in 1mM NaHCO3 / 1 mm NaCl) Buffer PDADMAC Xyloglucan Xyloglucan Buffer PDADMAC The type of the polymer affects the viscous properties of the fibril layer Ahola et al, Bioresources, 2008

31 Properties Conclusions from last few slides Swelling the more charges on the cellulose the more swelling high ph dissociation of COOH-groups Salt affects the swelling more salt less swelling Interactions with polymers some polymers disperse the nanocellulose some polymers aggregate the nanocellulose Choose the environment according to desired properties

32 Application possibilities Monika Österberg

33 Potential application areas based on properties of nanocelluloses NFC properties Natural and renewable Biodegradable Biocompatible High strength and modulus High surface area High aspect ratio Dimension stability Moisture absorption Thermal stability Chemical functionality (after modification) Possible application Green composites For reinforcement of (bio/nano)composites Construction materials Paper, packaging Rheology modifiers (thickener in food, paints, cosmetics and pharmaceuticals After modification: Functional surfaces, additives Hydrophobic water repellent and selfcleaning material Antimicrobial wound dressing, air filtration Biomedical applications such as drug carrier Monika Österberg

34 Nanofibrillated cellulose (NFC) properties and possibilities NFC binds water and has gel like properties 0.5 % gel NFC thickener in food, paint, etc. NFC forms dense, transparent films NFC forms strong and light composite structures OLED, packaging, NFC has a high surface area and aspect ratio Many sites for functionalization

35 Cellulose nanocrystals Properties: Short, crystalline ordered structures easily obtained Application: nanocomposites, Fleming et al Chem. Eur. J., 2001

36 Cellulose nanocrystals Production: Controlled sulfuric acid degradation of cellulose fibres Introduces sulphate groups, stable colloidal suspensions exhibiting nematic liquid crystalline alignment Also other acids can be used for the hydrolysis: HCl, HBr, less stable suspensions Modification: TEMPO-mediated oxidation ATRP grafting Silylation, esterification,.. Cationification Habibi et al, Chem Rev 110 (2010) 3479

37 The 2013 Marcus Wallenberg Prize is being awarded to Professor Derek Gray of McGill University, Montreal, Canada, for his pioneering study of nanocrystalline cellulose (NCC). Monika Österberg

38 How to modify nanocellulose: A simple model of nanofibrillated cellulose HO HO OH O OH HO O OH OH O n O HO OH O OH HO O OH OH OH O H

39 Different ways to chemically modify cellulose fibrils Chemical treatments using traditional organic chemistry, e.g. carboxymethylation, silylation Enzymatic treatments Irreversible adsorption of polymers, polyelectrolyte mutlilayers (PEM) or polyelectrolyte complexes (PEC) Direct grafting of polymer chains

40 Grafting from Cellulose nanocrystals Poly(N-isopropylacrylamide) brushes grafted from CNC 500nm Responsive nanomaterials Zoppe et al Biomacromolecules 2011, 12 (7) and 2010, 11 (10), Monika Österberg

41 Different parameters affect the adsorption of cationic polyelectrolytes on anionic fibrils (electrostatic interactions) Surface properties of fibrils - surface charge, surface area Structure of polymer - molecular weight, degree of substitution, structure (linear/ branched) Chemical environment - ph, ionic strength

42 Adsorption of PAE and nanofibrils on cellulose model surfaces PAE 100 mg/l Nanofibrils 100 mg/l Ahola, S., Österberg, M. and Laine, J. Cellulose 15(2008)

43 Distribution of PAE and nanofibrils on the cellulose model surfaces AFM height images, scan size 5 5 μm 500 nm Langmuir-Schaefer cellulose model surface 500 nm PAE and nanofibrils adsorbed as layerstructures homogeneous adsorbed film 500 nm PAE and nanofibrils adsorbed as aggregates heterogenic adsorbed film! Ahola et al. 2008

44 Effect of nanofibrils and polyamideamine epichlorohydrin (PAE) on paper strength Layered structure PAE-nanofibril aggregate 3:1 Constant PAE amount (5 mg/g) Ahola, S., Österberg, M. and Laine, J. Cellulose 15(2008) Significant improvements in both wet and dry strength are achieved when nanofibrils are used together with PAE!

45 Paper applications How to increase paper strength without deteriorating dewatering using NFC?? Tensile index [Nm/g] CS+ CMNFC4 CS+ NFCF min CS+ BKP fines Beating time Drainage time [s] CS = cationic starch, CMNFC = NFC from carboxymethylated pulp Taipale et al, Cellulose 2010

46 Novel material based on NFC OLED Transparent films NFC Nogi, Yano, Adv. Mater, 2008 Starch NFC foam Nogi, Adv. Mater, 2009 Ultra strong composites Svagan et al Biobased films with excellent barrier properties Aulin, Cellulose, 2010

47 Different materials and their mechanical properties Monika Österberg Wegst & Ashby, 2004

48 Super tough NFC composites First attempt towards biomimetic NFC composites Strategy Larges weight fraction hard and reinforcing NFC Small weight fraction flexible polymer Wang M., Olszewska A., Walther A., Malho J-M., Schacher F.H., Ruokolainen J., Ankerfors M., Laine J., Berglund L.A., Österberg M., Ikkala O. Biomacromolecules, 2011, 12(6),

49 NFC films H 2 O Oxygen transmission rate (OTR) OTR ( cm-3µmm-2d- 1kPa-1) EVOH 0 NFC 2h press NFC+ impregnation Aulin CMNFC Cellophane NFC/clay (Liu, Ikkala, Relative humidity (%) Berglund et al Advantages of NFC: (Renevable, nontoxic) Good strength (e.g. Young s modulus 13 GPa and tensile strength 232 Mpa) Excellent barrier properties

50 Creating specific surfaces from cellulose nanofibrils Examples of different routes: Variations in the NFC preparation procedure Chemical modifications of fibres prior the preparation of NFC Grafting of polymer chains to the surface of NFC Surface modifications of NFC by polymers, polyelectrolyte multilayers and polyelectrolyte complexes Mixing with other materials = composite structures Surface modification of aerogels (e.g. chemical vapour deposition) The application and modification possibilities are vast BUT remember the natural properties of NFC

51 Investments in NFC production November 2011 UPM started pre-commercial production of fibril cellulose May 28, 2010 World s first pilot unit for producing nanocellulose to be built in Stockholm. (Innventia) August 2012 U.S. Forest Products Laboratory opens pilot plant to produce wood derived renewable materials. Cellulosic nanomaterials can be stronger than Kevlar and provide high strength with low weight May 31, 2011 Stora Enso makes a groundbreaking investment in nanotechnology at Imatra, Finland. Stora Enso is taking a significant step forward in renewable materials innovation by building a pre-commercial plant at Imatra in Finland for the production of microfibrillated cellulose. Monika Österberg

52 Challenges with NFC XPS Where s the NFC? Why does NFC surface appear dirty? 98% H2O How should I get rid of the water? QCM-D Why does it aggregate? Why don t I see the adsorption? Monika Österberg, 4-8 June, 2012

53 How to maintain the nanostructure of NFC?? NFC gel, 98% water Interaction with the media There is an interest to use other solvents than water for surface modification of NFC 200 nm Risk for severe aggregation

54 Effect of media on aggregation of NFC from water No image from toluene-nfc Severe aggregation Individual fibrils were not observed DMA Toluene Well dispersed fibrils Aggregation in toluene Johansson, Tammelin, Campbell, Setälä, Österberg Soft Matter 7 (2011)

55 The media affects modification efficiency Example: Silylation trimethylsilyl cellulose Surface substitution~ 0.9 Surface substitution~0.03 Higher degree of substitution in non-aggregated state

56 Summary Nanocellulose is an renewable material with vast application possibilities The surface properties of nanocellulose has to be controlled to utilize its properties?! Monika Österberg, 4-8 June, 2012