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Barrier Properties And Recyclability of Spray Coated Nanocellulose Sheet
- 1. BARRIER PROPERTIES AND RECYCLABILITY OF SPRAY COATED NANOCELLULOSE SHEET S.Kirubanandan Ph.D. Student 17th March 2017, BAMI Industrial Chapter, APPI, Department of Chemical Engineering, Monash University Supervisors: Dr. Warren Batchelor, Prof. Gil Garnier and Dr . Swambabu Varanasi
- 2. Introduction and Background of the research Research Objective Methods Results Conclusion OUTLINE 2/36
- 4. NANOCELLULOSE Hierarchical structure of wood fibers, Network of micro fibrils (Zhu et al., 2014) Bio-degradable Bio-renewable Bio-compatible Characteristics High Specific Strength Thermal stability Hydrophilicity Chemical Modification 4/36
- 5. APPLICATIONS OF NANOCELLULOSE High performance barrier materials Water and Air Filtration Touch Screens (Zhu et al., 2014) Solar Cell (Georgia Tech News, 2013) 5/36
- 7. OVERVIEW OF BARRIER MATERIALS (Aulin and Lindström, Biopolymer Coatings for Paper and Paperboard, John Wiley & Sons, Ltd, 2011, pp. 255-276) 7/36
- 8. NANOCELLULOSE FILMS PREPARATION TECHNIQUES 1. Casting and Solvent evaporation 2. Vacuum filtration Filtration Separation Drying 3. Spray coating followed by Vacuum filtration Processing time – 10 min – 24 hrs Drying time -10 mins Processing Time –10-27 mins Is it possible to scale-up about methods? 8/36
- 9. RESEARCH OBJECTIVE Problem statement: Is it possible to develop a scalable method to prepare nanocellulose films/sheets????.... Research Objectives: • Tailoring barrier properties of spray coated nanocellulose sheet by adjusting the basis weight of nanocellulose films Outcome Spraying could be a suitable alternative method for vacuum filtration 9/36
- 10. SPRAY COATING PROCESS Spray Coating Provided uniform surface on the substrate.(Sanna Tiekstra, 2012, Functional Bio Based Coating for Moulded Pulp Trays, www.cepi.org) A Professional spray gun for performing spray coating process Concept Atomization Nozzle Droplets Disrupted Spray Jet 10/36
- 11. Rapid preparation of nanocellulose sheet using spray coating 11/36
- 12. EXPERIMENTAL SET UP A Professional spray gun for performing spray coating process Experimental Conditions : • Spray distance - 30 cm • Suspension concentration - 1.0 to 2.0 wt % • Velocity of conveyor – 0.25 to 0.62 cm/sec 12/36 517 Spray Gun
- 13. SEM IMAGES OF NANOCELLULOSE SHEET Free surface Spray coated surface 1µm 10 µm 100 µm 1 µm 10 µm 100 µm 13/36
- 14. BASIS WEIGHT AND THICKNESS 14/36 0 50 100 150 200 250 0 50 100 150 200 250 300 Basisweighting/m2 Thickness in µm Influence of Suspension concentration Influence of Velocity of conveyor
- 15. APPARENT DENSITY 15/36 0 100 200 300 400 500 600 700 800 900 1000 0 50 100 150 200 250 ApparentDensityinKg/m3 Basis weight in g/m2 Influence of suspension concentration Influence of Velocity of the conveyor
- 16. 16/36 Uniformity of the spray coated nanocellulose sheet
- 17. 17/36 Reference MFC Sheet 2.0 % MFC Wt. 1.75 Wt. MFC 1.50 Wt.% MFC 1.25 Wt.% MFC 1.00 Wt.% MFC FORMATION TEST –INFLUENCE OF SUSPENSION CONC.
- 18. 18/36 0 0.2 0.4 0.6 0.8 1 1.2 1.4 0.1 1 10 RelativeIndex Components (mm) 2% MFC 1.75% MFC 1.5 Wt% MFC 1.25% MFC 1.00% MFC FORMATION TEST
- 19. 19/36 Barrier Properties of the spray coated nanocellulose sheet
- 20. AIR PERMEABILITY 20/36 • The air permeability of the spray coated nanocellulose sheet is < 0.003 µm/Pa.S • All sheets are highly impermeable sheet Spray coated NC sheet
- 21. 21/36 WATER VAPOUR TRANSMISSION RATE 0 20 40 60 80 100 120 140 0 50 100 150 200 250 Watervaportransmissionrateg/m2day Basis Weight (g/m2) Influence of Velocity of the conveyor Influence of suspension concentration
- 22. Water Vapour PERMEABILITY WaterVapourTransmissionRateofNanocellulosesheetpreparedviaVacuumfiltration: WatervapourtransmissionrateofBHMNanocellulosesheet=33.92±3.5g/m2 day WatervapourpermeabilityofnanocellulosesheetbyBHM=38.15g.µm/m2 dayKpa. 22/36 0 10 20 30 40 50 60 70 80 90 0 50 100 150 200 250 Watervaporpermeabilityg.µm/m2dayKpa. Basis Weight (g/m2) Influence of velocity of the conveyor Influence of suspension concentration BHM NC Sheet = 38.15 g.µm/ m2 day Kpa.
- 23. 23/36 COMPARISON WITH SYNTHETIC POLYMERS LDPE HDPE Oriented Polystyrene EVA Aluminium Foil 2% NC Spray Coated sheet Nanocellulose sheet BHM 0 20 40 60 80 100 120 140 160 180 WVTR gm-2/day A
- 24. 24/36 Recyclability of the spray coated sheet
- 25. 25/36 METHOD Soaking of Spray coated NC Sheet 24 Hrs Disintegration at 75000 RPM Sheet Making using BHM PressingDrying Sheet from Repulped NC Sheet
- 26. 26/36 PROPERTIES OF RECYCLED SHEET Property Value Basis Weight 105.82±7.60 g/m2 Thickness 154.44±12.69 µm Density 690 Kg/m3 Surface Roughness 10.55±0.32 µm Recycled sheet
- 27. CONCLUSION • A rapid technique to prepare the nano-cellulose sheet was developed. • A novel technique to tailor the barrier properties of the NC sheet was developed. • It has recyclability and reprocessability. 27/36
- 28. ACKNOWLEDGEMENT • Dr. Warren Batchelor and Prof. Gil Garnier • Dr. Swambabu Varanasi • Student friends and staff members at BioPRIA 28/36
- 29. Thank you very much 29/36
- 30. 30/36 MFC Sheet Reference 0.59 cm/sec 0.52 cm/sec 0.42 cm/sec MFC Reference Sheet 0.38 cm/sec 0.32 cm/sec 0.25 cm/sec FORMATION TEST- INFLUENCE OF VELOCITY
- 31. 31/36 0 0.2 0.4 0.6 0.8 1 1.2 1.4 0 5 10 15 20 25 30 35 40 45 RelativeIndex Components in mm Nanocellulose sheet -Vaccum Filtration Spray coated sheet at Speed 10 Spray coated sheet at speed 8 Spray coated sheet at speed 6 Spray coated sheet at speed 5 Spray coated sheet at Speed 4 Spray coated sheet at speed 2
Editor's Notes
- Good afternoon everyone, Thanks for attending my presentation on nanocellulose as barrier materials , Thanks Prof Warren for introducing me to Audience , I am working on the research topic on nanocellulose sheet and its composites as barrier materials and developing these materials using spray coating,
- In this confirmation seminor, I would like to talk about Introduction and Background of the research, Research aims , Preliminary research and Proposed research Conclusion of this research work
- Cellulose is the most abundant biopolymer on the earth. Wood fibers are composed of 40–45% cellulose, which is produced in nature via photosynthesis and ubiquitously used in the everyday life.56 The cell wall of natural wood bers has a 3 dimensional (3D) hierarchical structure designed for the metabolic ion transportation and to possess mechanical stability, The microbril bundles are composed of microbril cellulose (MFC) and nanobril cellulose (NFC). MFC is delaminated from wood pulp through mechanical treatments before and/or aer enzymatic or chemical pretreatment, which has a diameter of 5– 60 nm with a length of several micrometers. It has specific characteristics to make many functional sustainable materials Due to its biodegradability, it has good alternative for synthetic polymers It has potential of recyclable It is non –toxic material Due to its biocompatibility, it can be used as base substrate for development of tissue engineering scaffolds It is eco –friendly material
- Nanocellulose widely used in the fabrication of many functional materials High performance barrier materials has low air permeability and water permeability Due to its narrow pore size, it could be used as filters for water and air It has capable to compat with inorganic materails , so it is used in the design of touch screen and solar cell The CNF films have higher entanglements within the film which increased the tortuosity factor or increase the diffusion path [33]. Even though nanocellulose provides a high barrier for oxygen, the water vapor barrier properties are low. This is mainly due to high affinity between water and the nanocellulose film. Nanocellulose is much better water vapor barrier than cellulose fiber. Nanocellulose has a strong reducing effect on water vapor diffusion due to its size, and swelling constraints formed due to rigid network within the films. However, at a high relative humidity these structural organizations can be disrupted due to high swelling and can lose barrier properties for both oxygen and water vapor [34].
- Packaging materials has poor barrier properties due to large pore size . Coating with wax, Aluminium and Plastics could create the problem of recycle and reprocessability.
- Oxygen and water vapour transmission rate are important target properties of the packaging materials. Films are prepared from the biobased materials are good barrier against oils and grease and poor barrier against water vapour due to its hydrophilicity.
- There are few methods available for nanocellulose films for various functionality. Casting of the nanocellulose suspension is the most common technique at laboratory scale and it requires longest drying time for evaporation of solvent in the suspension. Vacuum filtration is the most method for making the films. It requires processing time from 10 mins to 4hours in the nanocellulose film and in the case of nanocomposite, it requires 24 hrs s for dewatering in the filateration process 3. Spray coating is recently reported to replace the filtration process , however after coating , the same filteration is used to removed the excess water formed sheet and it required time which is not reported in the literatue. Therefore, these methods have problem in the scale up , it requires alternative process for fabrication nanocellulose film
- Spray coating is a contactless coating and provides contour coating and possible to coat tear sensitive material and easy to control the coating material. In this coating method, the topography of the substrate has no influence on the coating weight. For example, on uneven surfaces a contour coat can be applied. This could result in a reduction of cost and an improvement of quality. Atomization is the integral part of spray coating , this process is highly governed by the physical property of coating fluid such as density , surface tension and viscosity. Contactless Contour coating Coating of tear sensitive material Controlling the coating material
- The experimental system for a lab scale spray coating system with experimental conditions is shown in Figure 3. The nanocellulose suspension was sprayed on a circular stainless steel plate moving on a variable speed conveyor using a Professional Wagner spray system (Model number 117) at a pressure of 200 bar. The type 517 spray tip gave an elliptical spray jet. The spray jet angle and beam width are 50° and 22.5 cm, respectively. The spray distance is 30.0±1.0 cm from the spray nozzle to the circular steel plate. Conveyor was operated at a constant speed of 0.32 cm/sec for the spraying of MFC on the plate surface. I have also performed the experiment on spray coating
- Figure 4 explains the surface morphology and topography of both sides of the spray coated nano-cellulose film investigated by scanning electron microscopy. The spraying nanocellulose on the stainless steel plate produces a rough and smooth side of the sheet. The rough side of the spray coated sheet is similar to the sheet prepared via vacuum filtration. The surface exposed to atmosphere is called rough surface where the residual cellulose fibres are free and roughness in the surface. The rough surface of the film confirms that the film contains densely packed various size of free fibres and clumps of cellulose fibres and further free from pinhole. The fibres are well connected between different fibres size and forms matrix of different pore size. In the rough side of the sheet, there are free fibres towards the atmospheric and high surface roughness
- This plot explains effect of suspension concentration on the basis weight of the sheet and thickness of the sheet /nanocellulose film prepared using spray coating technique at a constant velocity of 0.32 cm/sec. The stable and homogeneous films with various concentrations of MFC suspension were prepared via spray coating technique as described in the experimental section. The operational range for spraying nanocellulose suspension was between 1.0 wt. % and 2.0 wt. %. Below 1 wt. %, the suspension was too dilute and flowed over the metal surface, producing a highly uneven film that was difficult to peel from the plate after drying. Above 2% wt. of suspension, the suspension become too viscous to spray. The lower and upper limits, corresponded to suspension viscosities of 17 to 32 DIN sec, respectively. Figure 6 shows the effect of nanocellulose suspension concentration on the basis weight of the film and mean thickness of the film. Each point is the average of 4 replicates with the error bars providing the standard deviation. Both sheet basis weight and thickness increased approximately linearly with increasing nanocellulose suspension concentration. Basis weight range from 52.8±7.4 to 193.1±3.4 g/m2 by spraying suspension with concentration of 1.0 and 2.0 wt. %, respectively; film thickness were 83.9±13.9µm and 243.2±6.6 µm for the lowest and highest consistencies.
- The figure explains about the effect of the velocity of the conveyor on the basis weight of the nanocellulose sheet prepared by spray coating process and how it does influence on the spraying time of nanocellulose on the stainless steel plated indirectly and as a consequence, the basis weight of the sheet is varied from 49 to 102 g/m2. The figure confirms that the basis weight of the nanocellulose sheet is controlled by the velocity of the conveyor. Thickness -70 -140 microns
- The uniformity of the nanocellulose sheet would affect the barrier properties and mechanical properties
- The air permeability of the spray coated nanocellulose sheets prepared various concentration of NC suspension are highly impermeable
- A rapid and commercially scalable, economically feasible method for preparing nanocellulose sheet is developed to produce high basis weight and quality nanofiber sheet and to replace the standard method of vacuum filtration. The basis weight is controlled by the spraying time and nanocellulose concentration in the suspension. The processing time for producing the sheet is less than 1 min and the quality of the spray coated sheet is confirmed by the uniformity in thickness of the sheet.
- I would like to thank my supervisor for guiding this work successfully.