Water-based Modification of Cellulose Nano Fibrils for Packaging Applications Kendra Fein Doug Bousfield William Gramlich 1
Motivation Environmental Plastic Microplastics in oceans centuries to degrade transports plasticizers and flame retardants absorbs contaminants from environment Ingested by wildlife smells like food to fish impacts commercial fishing 2 https://marinedebris.noaa.gov/research/microplastic-ingestion-black-sea-bass-centropristis-striata-assessment-potential-impacts
Motivation Shift in Market Change in demand for biodegradable packaging material NYC banned polystyrene food containers in 2015 bagasse (sugarcane) paper Costa Rica proposed to ban all single-use plastic by 2021 poly(lactic acid) (PLA) PLA-coatedpaper 3
Research Introduction Create competitive bio-based packaging material limited or expensive options available can be difficult to match properties of plastic Modified CNF can offer some film benefits Cellulose nanofibril film 4
What is CNF Highly fibrillated cellulose Process Development Center 1000 kg/day capacity Upscaling potential and simplicity of material process 2 4 mm (Smook 2002) 20 40 µm (Smook 2002) cellulose fibers from wood 5
What is CNF Highly fibrillated cellulose Process Development Center 1000 kg/day capacity Upscaling potential and simplicity of material process 0.5 10 s mm (Moon et al. 2011) 6 10 100 µm (Moon et al. 2011) MFC 5
What is CNF Highly fibrillated cellulose Process Development Center 1000 kg/day capacity Upscaling potential and simplicity of material process 0.5 2 µm (Moon et al. 2011) 7 4 20 nm (Moon et al. 2011) CNF 5
Poor oxygen barrier PAPER Hydrophilic Hygroexpansive Cellulose derived from trees Moisturesensitive Biobased Brittle PLA Typically hydrophobic Heat resistant to only 40 C CNF Good grease and oxygen barrier vs paper 6
Research Objectives Understand relationship between modification and properties Chemically modify CNF to adjust film properties strength hydrophobicity oleophilicity flexibility dispersion Consider up-scaling 7
Step 1: Investigate Unmodified CNF Films Develop repeatable process in lab modify CNF in water with various chemistries generate free standing films test mechanical and barrier properties Films properties affected by: temperature humidity processing drying rates 8
Film Properties to Investigate Mechanical/Structure Instron Tensile stress, strain Scanning Electron Microscope formation, visual analysis Porosity Opacity Barrier Water Contact Angle hydrophilicity Kit Test oleophilicity Water vapor transmission 9
Step 2: Water-based Modification Surface modification in water process developed in Gramlich group Previous methods require several solvent exchange steps Up-scaling potential 10
CNF Purification Steps Dialysis Separation by concentration CNF in dialysis bags Not up-scalable Centrifugation Separation by density Series of water replacement Up-scalable 12
Step 3: Thiol-ene Reaction very versatile + radical initiation highly-reactive double-bond molecule thiol thiolfunctionalized molecule 13
Step 4: Modified CNF Film Analysis Strength vs. flexibility/stretch Barrier properties Optical properties Dimensional stability CNF swells and shrinks testing in TAPPI conditions Biodegradability Recyclability 14
Cellulose Polymer Norbornene- Functionalized Thiol- Functionalized 11
Cellulose Polymer Norbornene- Functionalized Thiol- Functionalized 11
Future Work Evaluate film surface and thickness Improve basis weight measurements Monitor physical, optical, and barrier properties Secondary modification for toughness and/or hydrophobicity Continue PhD proposal 16
Thank you kendra.fein@maine.edu bousfld@maine.edu william.gramlich@maine.edu Project Sponsored by: Paper Surface Science Program (PSSP) P3Nano Collaboration 17
Opacity (%) Opacity Increasing Weight 64 62 CNF CNF CNF 60 58 CNF NaOH CNF CNF CNF CNF 56 2.5x ccnf 54 52 5x ccnf 10x ccnf 10x 10x 10x 50 10 30 50 70 Basis Weight (g/m 2 ) 10x 10x 10x 20
CNF Films Thicknesses Sample Name n Thickness (μm) Approximate Drying Time petri dish 9 33.0 days forced air-dried 9 39.1 hours heated 70 C 16 42.5 20 mins heated 80 C 12 41.4 20 mins heated 90 C 12 42.4 20 mins air-dried samples constrained with a ring shrinking in heated samples less petri dish shrinking at lower basis weights 21
Young's (Elastic) Modulus E = 2,734 MPa Tensile Strain at Break Tensile Stress at Break Area under curve = Tensile Energy Absorption (TEA) = Tensile Toughness 22
Stress (MPa) 70 60 25 g/m 2 Stress-Strain Curves All Drying Types 50 40 30 20 petri dish forced air 70 C 80 C 90 C 10 0 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 Strain (mm/mm) 23
Young s (Elastic) Modulus of Common Materials LDPE PET HDPE unmodified CNFfilms polystyrene (foam) rubber (small strain) PTFE (teflon) polypropylene diatom frustules (silicic acid) polystyrene (solid) nylon medium-density fiberboard 0 1 2 3 4 Young s Modulus (GPa) https://en.wikipedia.org/wiki/young's_modulus 24
Stress at Failure (MPa) 100 90 80 70 Tensile Stress NaOH CNF 2.5x CNF 60 50 40 CNF 5x CNF 10x CNF 30 10 20 30 40 50 60 Basis Weight (g/m 2 ) 25
Toughness (kj/m 3 ) 16 Tensile Toughness 14 12 10 8 2.5x CNF NaOH CNF 6 4 2 5x CNF 10x CNF 0-2 10 20 30 40 50 60 Basis Weight (g/m 2 ) 26
Strain at Failure 0.20 Tensile Strain 0.16 2.5x CNF NaOH CNF 0.12 0.08 CNF 5x CNF 10x CNF 0.04 10 20 30 40 50 60 Basis Weight (g/m 2 ) 27
Young's Modulus (GPa) 2.50 Young s Modulus 2.00 1.50 1.00 1.88 2.02 1.70 1.48 1.57 0.50 0.00 CNF NaOH CNF 2.5x ccnf 5x ccnf 10x ccnf Films 28