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Nanocellulose based functional material using spraying
- 1. DEVELOPMENT OF NANO-CELLULOSE BASED FUNCTIONAL MATERIAL USING SPRAY COATING S.Kirubanandan Ph.D. Student 25th November 2016, PhD Confirmation Seminar, 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 Aims Preliminary Research Proposed Research Conclusion OUTLINE 2/36
- 3. Background and Literature Review 3/36
- 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 GAP Problem statement: Is it possible to develop a scalable method to prepare nanocellulose based films/sheets????.... Research gap: • Tailoring the basis weight of nanocellulose films – Range of coat weight • Mechanical and barrier properties of spray coated nanocellulose sheet • Effect of additives (Nanoclay/nanoparticles) on nanocellulose suspension to make nanocomposite as high performance barrier materials. • Performance of laminates on base sheet 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. RESEARCH AIMS Task 1 • To prepare nanocellulose sheet using spray coating • Mechanical and barrier Properties of nanocellulose sheet Task 2 • To prepare nanoclay/nanocellulose composite Task 3 • To prepare nano particles/nanocellulose composite Task 4 • Coating of nanocellulose on the base sheet 11/36
- 13. Task 1 Rapid preparation of nanocellulose sheet using spray coating 13/36
- 14. EXPERIMENTAL SET UP A Professional spray gun for performing spray coating process Stainless Steel Plate Spray Jet Nano cellulose film Professional Spray Gun 517 Spray Gun Variable Speed Conveyor Experimental Conditions : • Spray distance - 30 cm • Suspension concentration - 1.0 to 2.0 wt % • Velocity of conveyor – 0.25 to 0.62 cm/sec 14/36
- 15. EFFECT OF SUSPENSION CONSISTENCY 0 50 100 150 200 250 300 0 50 100 150 200 250 0.8 1 1.2 1.4 1.6 1.8 2 2.2 BasisWeighting/m2 Concentration of Nanocellulose in wt% Basis Weight Vs Suspension Concentration Thickness Vs Suspension Concentration Thicknessinµm Velocity of conveyor – 0.32 cm/sec 15/36
- 16. 0 20 40 60 80 100 120 140 160 0 20 40 60 80 100 120 0.2 0.3 0.4 0.5 0.6 0.7 BasisWeightofthesheeting/m2 Velocity of the conveyor in cm/sec Suspension concentration – 1.5 wt % EFFECT OF THE VELOCITY OF THE CONVEYOR ThicknessoftheSheetinmicrons 16/36
- 17. THICKNESS MAPPING Surface exposed to atmosphere - rough Surface adjacent to plate - Smooth SprayDirection 17/36
- 18. THICKNESS DISTRIBUTION Spray Coated MFC Sheets MFC Sheet made by Vacuum Filtration 1 2 3 4 1 2 3 4 Region Region 111.0 116.0 121.0 126.0 131.0 136.0 141.0 146.0 151.0 1 2 3 4 1 2 3 4 Region Region 109.0 111.4 113.8 116.1 118.5 120.9 123.3 125.6 128.0 18/36
- 19. SEM IMAGES OF NANOCELLULOSE SHEET Free surface Spray coated surface 1µm 10 µm 100 µm 1 µm 10 µm 100 µm 19/36
- 20. ROUGHNESS OF SHEETS Rough surface Smooth surface 20/36
- 21. SURFACE ROUGHNESS OF THE SHEET Technique used Surface of film RMS Roughness (nm) To make films To measure roughness Spray coating AFM Rough 414.0 nm (10µm x10µm) 51.4 nm (2µm x 2µm) Smooth 81.1 nm (10µm x10µm) 16.7 nm (2µm x 2µm) Spray coating Parker Print Surface Instrument Rough 10.8±0.17µm - Smooth 5.5±1.4 µm - Vacuum filtration Parker Print Surface Instrument Both sides 10.6±0.3 µm 9.9±0.1 µm - 21/36
- 22. Task 4 Spray coating of nanocellulose on the base sheet 22/36
- 23. Preparation of Nanocellulose suspension Spray deposition on base sheet Drying of spray coated base sheet SPRAYING OF NANOCELLULOSE Evaluation of viscosity Of suspension 23/36
- 24. SPRAY COATED BROWN PAPERS 1.5 Wt.% 1.25 Wt.% 1.00 Wt.% 0.75 Wt.% 0.5 Wt.% Uncoated 24/36
- 25. SEM IMAGE OF COATED SURFACE Uncoated Brown Paper 1.25 Wt.% MFC coated Brown Paper 100 µm 100 µm 25/36
- 26. EFFECT OF SUSPENSION CONCENTRATION 0 5 10 15 20 25 30 35 40 0.4 0.6 0.8 1 1.2 1.4 1.6 BasisWeightofcoating/m2 Suspension Consistency in Wt % 26/36
- 27. AIR PERMEABILITY 0 0.5 1 1.5 2 2.5 3 3.5 0 5 10 15 20 25 30 35 AirPermeanceinµm/Pa.s Basis Weight of nanocellulose coating in g/m2 27/36
- 28. SCALE UP OF A SPRAY COATING PROCESS Dow Web Coater for Pilot scale Operation Professional Airless Spray System Professional Spray Gun 28/36
- 29. PROGRESS SO FAR • A rapid technique to prepare the nano-cellulose sheet ultra high smoothness was developed. • The sheet has better uniformity than the sheet prepared via vacuum filtration. • A novel technique to improve the barrier properties of the base sheet was developed. • It is a scalable technology for converting coating process into a continuous process using a Dow web coater. 29/36
- 30. Nanocellulose Sheet and its Characterization Nano clay/Nano celllulose nanocomposite Nanoparticles/Na no-cellulose nanocomposites Coating of NC On a base sheet Task 1 Task 2 Task 3 Task 4 TASK OF MY PHD 30/36
- 31. FUTURE PLAN Task 2 and 3 Objective: Development of Nanocellulose based nanocomposite Methods: • Spraying of nanocellulose mixed with Nano-clay/Inorganic Nanoparticles. • Study surface properties of the nanocomposite. • Study the mechanical and barrier properties of the nanocomposite. Outcome: High performance barrier materials by spray coating method Task 1 • Evaluating barrier properties of spray coated sheet (On going) 31/36
- 32. FUTURE PLAN Task 4 Objective Preparation of nanocellulose barrier layers on the base sheet by spray coating Methods • Spraying nanocellulose on the brown paper using Dow web coater with Professional spray system in a continuous mode • Optimization of the coat weight on the base sheet • Investigating the barrier properties, surface properties and adhesion studies between coating layer and base sheet, Outcome Scalable spray coating process 32/36
- 34. COMMUNICATION OF RESULTS Manuscripts under preparation 1. “Rapid Preparation of ultra-high smoothness Micro-fibrillated cellulose sheets using spray coating” – Completed draft being revised for submission to ACS Applied Materials and Interface. 2. “Strength and Barrier Properties of Spray Coated Micro-fibrillated cellulose” – Paper being written for submission to Cellulose –Springer. Planned Publications 3. Spray coated Nano-clay/Nanocellulose Composite – Mechanical and Barrier Properties – (Planned) 4. Spray Coated Nanocellulose crystal/nanocellulose Composite – Mechanical and Barrier Properties- (Planned) 5. A continuous spray coating of nanocellulose on the base sheet – Mechanical, Surface and Barrier Properties- (Planned) 34/36
- 35. ACKNOWLEDGEMENT • Dr. Warren Batchelor and Prof. Gil Garnier • Dr. Swambabu Varanasi • Mr. Scot Sharman, Mr. Shaun Ang and Ms. Natasha Yeow • Student friends and staff members at BioPRIA 35/36
- 36. Thank you very much 36/36
- 37. MECHANICAL PROPERTIES 10 20 30 40 50 60 70 80 0 50 100 150 200 TensileIndexinNm/g Basis Weight of spray coated sheet g/m2 Effect of suspension concentration Effect of Velocity of Conveyor 30 35 40 45 50 55 60 65 70 75 0.2 0.4 0.6 TensileIndexinNm/g Velocity of conveyor in cm/sec
- 38. 0 2 4 6 8 10 12 14 16 18 20 20 70 120 170 Young'sModulusinGPa Basis weight of the spray coated sheet YOUNG’S MODULUS Effect of Suspension concentration 0 1 2 3 4 5 6 7 8 9 10 0.1 0.2 0.3 0.4 0.5 0.6 0.7 YoungsmodulusinGPa Velocity of the conveyor cm/sec Effect of Velocity of conveyor
Editor's Notes
- Good afternoon everyone, Thanks for attending my confirmation seminor, Thanks Prof Warren for introducing me to Audience , I am working on the research topic on nanocellulose sheet and its composites as barrier 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].
- 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
- Task 1: The spray coated nanocellulose sheet is prepared rapidly by spray coating method. The uniformity and surface topography of the spray coated nanocellulose sheet in comparisions with sheet prepared via vaccume filteration is not understood sofar. Similarly, the barrier and mechanical properties of spray coated nanocellulose sheet in comparsion with the nanocellulose sheet via vaccume fileteration is not understood. In this work, How can the process be controlled to produce sheets to the required properties. How does spraying of different suspension concentration of nanocellulose affect the properties of the sheet. Task 2: The spray coating of nanocellulose on the base sheet to enhance its barrier properties by producing cellulose layers and make this process in a continuous mode. Task 3 and 4, In vaccum filteration, long processing time from 1 -24 hrs for making nanocomposite due to high dewatering time. Therefore, spray coating is an alternative and rapid technique to develpe nanocomposite which will be high performance barrier 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
- 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
- Mapping of thickness of the nanocellulose sheet which diameter of 15.4 cm. The thickness is measured six locations in each region of the sheet. The rectangular section of centre part of the sheet is used for contour plotting.
- The uniformity of the spray coated MFC film is evaluated and compared using contour plot of thickness measured on the various regions of the film and compared with a film made by vacuum filtration. Figure 3 explains the thickness distribution of the 1.5 Wt. % spray coated film at a constant velocity of 0.0032 m/sec. and film made by vacuum filtration method. The basis weight of the sheet prepared by spray coating and vacuum filtration are 100.5±3.4 g/m2 and 95.2±5.2 g/m2 respectively. When compared to the sheet made from vacuum filtration, the spray coated micro –fibrillated cellulose sheet is slightly thicker, even when correcting for the slight difference in basis weight. The apparent density of the spray coated sheet and sheet prepared via vacuum filtration were 793 and 834 kg/m3, respectively. In addition, there is a somewhat wider distribution of thickness for the spray-coated film. The thickness of the MFC film sheet prepared via vacuum filtration process and spray drying were 113.4 (5.4) µm and 127.1 (12.1) µm, respectively. The numbers in brackets give the standard deviation of the distribution of measured thickness.
- 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
- The surface morphology and topography of the nanocellulose sheet evaluated by Atomic force microscopy. The AFM Studies confirms surface roughness of the sheet prepared via Spraying The atomic force microscopy investigation of the spray coated nanocellulose film confirms the surface roughness of both side at nano scale. Figure 4 also shows the surface topography of the rough and glossy side of the cellulose film. The surface roughness of the rough side in root mean square (RMS) is 414.0 nm for 10µm x10µm film area and 51.39 nm for 2µm x 2µm film area where as the surface roughness of the glossy side in root mean square (RMS) is 81.05 nm for 10µm x10µm film area and 16.73 nm for 2µm x 2µm film area. Based on the surface roughness in RMS and AFM image, most of the variations in the surface topography and roughness between rough and glossy side of the cellulose film seems to be caused by residual fibres that produce unevenness at surface of the cellulose film. Moreover, Micro-fibrillated cellulose consists of different size of cellulose fibrils and clumps of cellulose fibres have dimension 5-60 nm with several micrometres in length. In the spraying process, the random deposition of cellulose fibres on the steel plate cause the variations in the surface roughness.
- The results reported in this investigation confirm that a laboratory scale spraying of various concentration of nano-cellulose on a stainless steel could be considered for the rapid preparation of nano-cellulose film with basis weight ranging from 50 to 200g/m2. The basis weight of the sheet is controlled by the concentration of Nano-cellulose sprayed on the stainless steel plate at a constant speed of conveyor. Moreover, the spraying nanocellulose on the stainless steel plate creates a uniform thickness of the cellulose sheet on the base and its uniformity thro thickness mapping compared with the sheet prepared via vacuum filtration. The thickness and mass of the film per unit area evaluated in this spray coating method are comparable to that in the work (Beneventi, Zeno et al. 2015) who reported that the thickness and mass per unit area (grammage) of the micro- fibrillated is 30-90µm and 13.7 -124 g/m2, respectively. (Beneventi, Zeno et al. 2015) reported that the processing time for making MFC sheet on nylon fabric varies from spraying time 15 to 90 s to make sheets with the basis weight of 13.5 and 124 g/m2. Their works lacks about how does spraying produce uniform sheet and thickness mapping of the sheet. In our investigation on spraying, the processing time for 1.5 Wt. % of the nano-cellulose sheet is varied from 25 sec to 63 sec to make sheets with basis weight from 49.11±5.39 g/m2 to 102.24 ±7.53 g/m2. Our work is compared with the work reported by (Varanasi and Batchelor 2013), informed that their processing time is 10 min and achieved basis weight of 56.4 g/m2. Moreover, another laboratory method could produce low mass per unit area of the film , for example,(Syverud and Stenius 2008) reported that the prepared 0.1 MFC film has 17-35 g/m2 with a film thickness of 21 ± 1µm to 33 ± 2 µm. The standard method using British Hand Maker could produce the Nano fibrillated film with a basis weight of 62.4 g/m2 (González, Alcalà et al. 2014). Another comparison with the standard method for Nano fibrillated film (Österberg, Vartiainen et al. 2013) has a processing time of 1-2.5 hrs with a basis weight of 55g/m2. Additionally, this laboratory spray coating could be comparable with conventional paper sheets production via rapid kothen sheet maker to produce the sheet with basis weight of 35g/m2 and 28 g/m2 (Beneventi, Chaussy et al. 2014, Beneventi, Chaussy et al. 2014). It does justify the limitations of conventional paper machine and advantages of the spray coating process in the aspects of basis weight and processing time. The surface morphology of the MFC film characterized by SEM confirms that the presence of difference fibre size and particles . To conclude that the laboratory scale of spray coating to prepare the nano-cellulose sheet is a rapid method and scalable for industrial production.
- 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.