Material processing based on wood nanofibrillated cellulose - PowerPoint PPT Presentation

Material processing based on wood nanofibrillated cellulose Houssine Sehaqui (currently post-doc at EMPA - Switzerland)

Introduction • 100 million tons plastics from petroleum produced annually, 40% used as packaging � waste (not biodegradable) Polymers from renewable resources of interest; abundant, low cost, biodegradable, need good properties and low environmental impact 2

Wood structure 3 components: • Cellulose nanofibrils • Hemicellulose • Lignin 3

Nanofibrillated cellulose 3wt% NFC suspension Diameter of the fibrils is 25 – 100 nm delignification 2wt% NFC suspension 2.enzym Diameter of the fibrils Mechanic. is 10 – 30 nm 1.Turbak et al JAPS (1983) 0.6wt% TEMPO- NFC 2.Pääkko et al Biomacrom. (2007) suspension 2.Henriksson et al Eur. Poly. J. (2007) Diameter of the fibrils 3.Saito et al Biomacromolecules (2007) is 4 – 5 nm

Nanofibrillated cellulose • High modulus about 140 GPa. 1 • High aspect ratio and surface area • Network formation ability through hydrogen bonds and secondary interactions • This can be exploited in materials elaboration and reinforcement in composites 1 Iwamoto et al Biomacromolecules (2009) 5

Materials from NFC Pression Liquid 2 Solid 1 3 Critical point Gas Temperature 1. Evaporation � � NFC nanopaper � � 2. Supercritical drying � � � � NFC aerogel 3. Freeze drying � � NFC foam � �

1. NFC nanopaper by liquid evap. Pression Liquid Solid 1 Critical point Gas Temperature 7

NFC nanopaper • NFC nanopaper: mat of cellulose nanofibrils. • Prepared by vacuum filtration and drying STEP 1 STEP 2 STEP 3 NFC suspension @ 0,2% filtration Carrier board d= 20 cm Woven metal vacuum cloth 0.65µm filter 93°C and 70 mbar membrane for 10 min on a metallic sieve Henriksson et al Biomacrom. (2008) Sehaqui et al Biomacrom. (2010) 8

Nanopaper Structure Surface SEM Cross section SEM 9

Nanopaper properties • Density ~ 1300kg/m 3 , Porosity ~ 15% • Transparent and flexible • Smooth (low surface roughness) • High barrier properties 1 and low surface area • Low thermal expansion 2 1 Liu et al Biomacrom. (2011) 2 Yano et al Adv. Materials (2009)

Mechanical properties in tension E nanopaper = 13 Gpa σ nanopaper = 230 Mpa ε nanopaper = 5 % Toughness= 7.5 MJ/m 3 E paper = 8 Gpa σ paper = 100 Mpa ε paper = 3 % Toughness = 1.7 MJ/m 3 Sehaqui et al, Composites Science and Technology 2011

Improving mechanial properties • Goal: partially aligning the fibrils in the wet gel by stretching DR=L f /L 0 Unstretched Sehaqui et al , DR=1 Stretched ACS Applied Materials and Interfaces 2012 DR=1.6

Degree of orientation by XRD < φ > − 2 (3 cos 1) = f 2 0.8 Hermans orientation parameter: f 0.7 0.6 0.5 Through 0.4 Edge 0.3 Edge 0.2 Drawn direction Through 0.1 0 1 1.1 1.2 1.3 1.4 1.5 1.6 Drawn ratio (%) 13

Tensile Mechanical Properties Drawing ratio 1 1.2 1.4 1.6 Modulus (GPa) 10.3 (0.8) 17.3 (4.0) 24.6 (0.4) 33.3 Strength (MPa) 185 (7.7) 345 (40) 428 (15) 397 Strain at break (%) 5.26 (0.56) 3.55 (1.21) 2.46 (0.23) 1.79 14

2. NFC aerogel by supercritical drying Pression Liquid 2 Solid Critical point Gas Temperature Sehaqui et al Biomacrom. (2011) 15

High surface area nanopaper • Previous NFC nanopaper has a low surface area (0.008m 2 /g). • Goal: preserve the surface area of the nanopaper and study effects on mechanical properties 1/ Vacuum filtration 1 2 2/ Careful drying techniques 16

High surface area nanopaper Direct SC-CO 2 SC-CO 2 drying NFC TEMPO-NFC Density/ Density/ 640 1200 205 kg.m -3 kg.m -3 20 Porosity/ % 56 Porosity/ % 86 Surface area / Surface area / 0.008 482 304 m 2 g -1 m 2 g -1 Fibril Fibril diameter/ - 9.0 5.7 diameter/ nm nm Average pore Average pore - 35.8 12.4 diameter/ nm diameter/ nm 17

High surface area nanopaper TEMPO-NFC nanopaper NFC nanopaper 500 nm SSA=482m 2 /g SSA=304m 2 /g 18

High surface area nanopaper • Mechanical properties ≈ thermoplastics but much lower density • Higher SSA correlates with higher ductility and lower stiffness 19

3. NFC foams by freeze drying Pression Solid 3 Critical point Gas Temperature Sehaqui et al Soft Matter (2010)

NFC foams • Goal: Prepare high-porosity NFC foams of different densities and study the density effect on the mechanical properties. NFC foam Density = 7 -100 kg/m 3 Porosity = 93-99.5% 21

Foam structure • NFC foam: ice templated cellular structure with ”nanopaper” cell wall • Specific surface area 14-42 m 2 /g 22

NFC foams 8 0,3 43 103 79 61 0,2 6 35 43 Stress (MPa) 22 0,1 7 4 0 0 10 20 30 40 2 35 22 7 0 0 10 20 30 40 50 60 70 80 90 100 Strain (%) • NFC foams have wide range of mechanical properties. Ductile with yield behavior. High energy absorption. 23

Conclusion 1 • Different structure can be achieved by different drying of NFC suspension Possible application: 1 Packaging; display Pression application Liquid Possible application: 2 Solid 2 1 3 Filtration, storage, insulation Gas Possible application: Packaging; 3 insulation, Temperature biomedical

NFC in composites 25

NFC composites • NFC as load bearing component in 2 phase system • 3 different methods have been used – Vacuum filtration and high T drying – Vacuum filtration and supercritical drying – Insitu polymerisation

1. NFC composites by filtration and high T. drying Papermaking approach to NFC/HEC dispersion. filtration drying NFC: Nanofibrillated Cellulose HEC: Hydroxyethyl Cellulose

NFC/HEC surface structure • Note porosity in ref nanopaper (left) • NFC embedded in HEC matrix (right) Sehaqui et al Soft Matter (2011) 28

NFC/HEC cross- section 29

NFC/HEC structure

NFC/HEC mechanical properties • Strain-to-failure of 20% and strength of 180MPa • Toughest cellulose composite reported 31

2. NFC composites by vacuum filtration and supercritical drying filtration drying

2. NFC composites by vacuum filtration and supercritical drying Porous membranes of HEC-coated nanofibrils as possible alternative to membranes by electrospinning Structure Mechanical properties 1/ high T 2/ ScCO 2 1/ Sehaqui et al Soft Matter (2011) 2/ Sehaqui et al , Biomac. (2012)

3. NFC composites by in situ polymerisation We start from high surface area nanopaper and graft polycaprolactone onto it. In-situ polymerization NFC: Nanofibrillated Cellulose PCL: Polycaprolactone

NFC PCL Structure Grafting and removal of free PCL Ungrafted nanopaper Grafted nanopaper Up to 80% PCL in the composites Boujemaoui et al , ACS Applied Materials and Interfaces 2012

NFC PCL properties DMA Water uptake NFC NFC NFC/PCL NFC/PCL PCL 50/50 50/50 • High mechanical properties of the composites even at high temperatures due to NFC network • Reduction of moisture uptake of NFC by 60% after PCL grafting

General conclusions

Conclusion NFC widens properties of wood based products 38

Conclusion • Density: 7-1300 kg/m 3 • Porosity range: 15% - 99.5% • Surface area: 0.01-480m 2 /g • Property modification: HEC / PCL coatings • � NFC is a versatile constituent offering numerous possibilities for material engineering

Acknowledgment • Financed by the Swedish center for Biomimetic fiber and engineering ( BIOMIME ) • Supporting funds KTH and WWSC • Supervisors Pr. Lars Berglund and A.Pr. Qi Zhou • Innventia for equipment facilities • All co-authors and co-workers ( Allais M, Melk L, Salajkova M, Liu A, Ikalla O, Ezekiel N, Nishino T, Morimune S, Galland S, Olsson R, Boujemaoui A, Carlmark A, Carlsson L, Lahcini M, Zhou Q, Berglund L ) 40

• Thesis book of the present work available online at: http://www.kth.se/polopoly_fs/1.151406!/Menu/general/column-content/attachment/Thesis%20Houssine%20Sehaqui.pdf

Thank you for your attention 42