Doctor of Philosophy, KTH Royal Institute of Technology, Stockholm, Fiber and Polymer Science (2016)
Master of Technology, Indian Institute of Technology, Roorkee (2011)
Reiner Dauskardt, Postdoctoral Faculty Sponsor
Multiscale Control of Nanocellulose Assembly: Transferring Remarkable Nanoscale Fibril Mechanics to Macroscale Fibers.
Nanoscale building blocks of many materials exhibit extraordinary mechanical properties due to their defect-free molecular structure. Translation of these high mechanical properties to macroscopic materials represents a difficult materials engineering challenge due to the necessity to organize these building blocks into multiscale patterns and mitigate defects emerging at larger scales. Cellulose nanofibrils (CNFs), the most abundant structural element in living systems, has impressively high strength and stiffness, but natural or artificial cellulose composites are 3-15 times weaker than the CNFs. Here, we report the flow-assisted organization of CNFs into macroscale fibers with nearly perfect unidirectional alignment. Efficient stress transfer from macroscale to individual CNF due to cross-linking and high degree of order enables their Young's modulus to reach up to 86 GPa and a tensile strength of 1.57 GPa, exceeding the mechanical properties of known natural or synthetic biopolymeric materials. The specific strength of our CNF fibers engineered at multiscale also exceeds that of metals, alloys, and glass fibers, enhancing the potential of sustainable lightweight high-performance materials with multiscale self-organization.
View details for DOI 10.1021/acsnano.8b01084
View details for PubMedID 29741364
Toward Semistructural Cellulose Nanocomposites: The Need for Scalable Processing and Interface Tailoring.
Cellulose nanocomposites can be considered for semistructural load-bearing applications where modulus and strength requirements exceed 10 GPa and 100 MPa, respectively. Such properties are higher than for most neat polymers but typical for molded short glass fiber composites. The research challenge for polymer matrix biocomposites is to develop processing concepts that allow high cellulose nanofibril (CNF) content, nanostructural control in the form of well-dispersed CNF, the use of suitable polymer matrices, as well as molecular scale interface tailoring to address moisture effects. From a practical point of view, the processing concept needs to be scalable so that large-scale industrial processing is feasible. The vast majority of cellulose nanocomposite studies elaborate on materials with low nanocellulose content. An important reason is the challenge to prevent CNF agglomeration at high CNF content. Research activities are therefore needed on concepts with the potential for rapid processing with controlled nanostructure, including well-dispersed fibrils at high CNF content so that favorable properties are obtained. This perspective discusses processing strategies, agglomeration problems, opportunities, and effects from interface tailoring. Specifically, preformed CNF mats can be used to design nanostructured biocomposites with high CNF content. Because very few composite materials combine functional and structural properties, CNF materials are an exception in this sense. The suggested processing concept could include functional components (inorganic clays, carbon nanotubes, magnetic nanoparticles, among others). In functional three-phase systems, CNF networks are combined with functional components (nanoparticles or fibril coatings) together with a ductile polymer matrix. Such materials can have functional properties (optical, magnetic, electric, etc.) in combination with mechanical performance, and the comparably low cost of nanocellulose may facilitate the use of large nanocomposite structures in industrial applications.
View details for DOI 10.1021/acs.biomac.8b00142
View details for PubMedID 29577729
Nematic structuring of transparent and multifunctional nanocellulose papers
AMER CHEMICAL SOC. 2018
View details for Web of Science ID 000435537702500
Wood Nanotechnology for Strong, Mesoporous, and Hydrophobic Biocomposites for Selective Separation of Oil/Water Mixtures
2018; 12 (3): 2222–30
Tremendous efforts have been dedicated to developing effective and eco-friendly approaches for separation of oil-water mixtures. Challenges remain in terms of complex processing, high material cost, low efficiency, and scale-up problems. Inspired by the tubular porosity and hierarchical organization of wood, a strong, mesoporous, and hydrophobic three-dimensional wood structure is created for selective oil/water separation. A delignified wood template with hydrophilic characteristics is obtained by removal of lignin. The delignified wood template is further functionalized by a reactive epoxy-amine system. This wood/epoxy biocomposite reveals hydrophobic/oleophilic functionality and shows oil absorption as high as 15 g/g. The wood/epoxy biocomposite has a compression yield strength and modulus up to 18 and 263 MPa, respectively, at a solid volume fraction of only 12%. This is more than 20 times that of cellulose-based foams/aerogels reconstructed from cellulose nanofibrils. The favorable performance is ascribed to the natural hierarchical honeycomb structure of wood. Oil can be selectively absorbed not only from below but also from above the water surface. High oil/water absorption capacity of both types of wood structures (delignified template and polymer-modified biocomposite) allows for applications in oil/water separation.
View details for DOI 10.1021/acsnano.8b00005
View details for Web of Science ID 000428972600015
View details for PubMedID 29412639
- Experimental evaluation of anisotropy in injection molded polypropylene/wood fiber biocomposites COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING 2017; 96: 147-154
- Interface tailoring through covalent hydroxyl-epoxy bonds improves hygromechanical stability in nanocellulose materials COMPOSITES SCIENCE AND TECHNOLOGY 2016; 134: 175-183
Strong Surface Treatment Effects on Reinforcement Efficiency in Biocomposites Based on Cellulose Nanocrystals in Poly(vinyl acetate) Matrix
2015; 16 (12): 3916-3924
In this work, the problem to disperse cellulose nanocrystals (CNC) in hydrophobic polymer matrices has been addressed through application of an environmentally friendly chemical modification approach inspired by clay chemistry. The objective is to compare the effects of unmodified CNC and modified CNC (modCNC) reinforcement, where degree of CNC dispersion is of interest. Hydrophobic functionalization made it possible to disperse wood-based modCNC in organic solvent and cast well-dispersed nanocomposite films of poly(vinyl acetate) (PVAc) with 1-20 wt % CNC. Composite films were studied by infrared spectroscopy (FT-IR), UV-vis spectroscopy, dynamic mechanical thermal analysis (DMTA), tensile testing, and field-emission scanning electron microscopy (FE-SEM). Strongly increased mechanical properties were observed for modCNC nanocomposites. The reinforcement efficiency was much lower in unmodified CNC composites, and specific mechanisms causing the differences are discussed.
View details for DOI 10.1021/acs.biomac.5b01245
View details for Web of Science ID 000366616700021
View details for PubMedID 26505077
- Nanostructured biocomposites based on unsaturated polyester resin and a cellulose nanofiber network COMPOSITES SCIENCE AND TECHNOLOGY 2015; 117: 298-306
- Hierarchical wood cellulose fiber/epoxy biocomposites - Materials design of fiber porosity and nanostructure COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING 2015; 74: 60-68
- Cellulose nanofiber network for moisture stable, strong and ductile biocomposites and increased epoxy curing rate COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING 2014; 63: 35-44
- Understanding the Mechanistic Behavior of Highly Charged Cellulose Nanofibers in Aqueous Systems MACROMOLECULES 2018; 51 (4): 1498–1506
- Nanocellulose-Zeolite Composite Films for Odor Elimination ACS APPLIED MATERIALS & INTERFACES 2015; 7 (26): 14254-14262
- Influence of processing routes on morphology and low strain stiffness of polymer/nanofibrillated cellulose composites PLASTICS RUBBER AND COMPOSITES 2015; 44 (3): 81-86
- Nanofibrillated cellulose reinforced acetylated arabinoxylan films COMPOSITES SCIENCE AND TECHNOLOGY 2014; 98: 72-78
- Thermally stable hydrogels from enzymatically oxidized polysaccharides FOOD HYDROCOLLOIDS 2012; 26 (1): 212-220