Introduction

A recent trend in the modern technology development is to “miniaturize” a system. The word “nano” is now added to the dictionary of materials and manufacturing to encompass the area of nano-materials including nanocomposites. To be honest, not many of these “hi-tech” developments could satisfy the “core” concept of sustainability. On way we can address some of the issues related to sustainability is to help develop “miniaturized” materials and manufacturing processes that use renewable resources. The backbone of a plant or tress is a polymeric carbohydrate with abundance of a “tiny” structure entity known as “cellulose fibrils”. These fibrils are comprised of different hierarchical microstructures commonly known as nano-sized microfibrils with high structural strength and stiffness. These nano sized fibrils are again combined of a crystalline and amorphous part and this crystalline part is named nanowhisker. Biopolymers from renewable resources have attracted much attention lately. Renewable sources of polymeric materials offer an answer to maintaining sustainable development of economically and ecologically attractive technology. In recent years, scientists and engineers are working together to use the inherent strength and performance of these nano-fibrils and make out of them a new class nano-materials of renewable nature by technologically combing them with natural green polymers.

The primary focus of our lab is to study 1) bioconversion of agricultural fiber crops into fibrous resources for composite manufacturing; 2) nanotechnology for fiber surface and paper sizing; 3) software development for creep prediction of natural fiber-plastic composites for building, construction and automotive applications. My dissertation has explored several important and under-researched topics on the isolation, characterization and dispersion of renewable biocellulose nanocomposite materials, their manufacturing processes, properties and some potential applications.

Current Work: Dispersion Mechanism of Cellulose Nanofibers in Bionanocomposites

I have two primary research interests: nanotechnology and biopolymer based nanocomposites. Nanotechnology has already triggered revolutions in the areas of engineering, sciences, medicine and environment. There is a growing interest on cellulose nanocomposites in developed and developing countries, especially if the nanocomposites are based totally on renewable raw materials. Cellulose nanofibers embedded in the cell walls, have a great reinforcing potential and it is predicted that nano reinforcements of the polymer matrix, are poised to create the next generation of value-added novel eco-friendly nanocomposites. This new class of renewable nanocomposites is expected to compete with the existing fossil fuel based products in automotive, aerospace, medical device and packaging applications.

One of the key objectives of isolating micro- and nano-cellulosic fibers by biological, chemical and mechanical methods from plant based fibers is to explore their potential to give a quantum leap in performance of composite materials manufactured from them. Cellulose fibrils have a high density of –OH groups on the surface, which have a tendency to form hydrogen bonds with adjacent fibrils, reducing interaction with the surrounding matrix. The cellulose fibers are not compatible with the hydrophobic polymer matrix and agglomerate, deteriorating their reinforcing capability. I have performed several mixing processes including the liquid phase film casting and solid phase melt blending. The properties of nanocomposites based on different biopolymer matrix, namely PLA, PHB and PVA are compared. My research has a certain emphasis on physical chemistry and interface science as well. Different types of surfactant and dispersant have been coated on the surface of cellulose nanofibers. Surface forces apparatus were used to quantify the free surface energy between nanofiber and biopolymer. The mechanical properties of bio-nanofilm demonstrated a 4- to 5-fold increase in tensile strength, as compared to the fiber-reinforced film.

Proposition of Intended Research

My research interests are composite materials from renewable resources with a focus on 1) composite processing; 2) mechanical behavior; 3) micro- and nanostructures of both reinforcements and composites; 4) composites long term properties and 5) biopolymer based nanocomposites.

1. The engineering of bio-composite materials with novel nanostructures and functions
I will concentrate on extending my research on the isolation and study of novel nanomaterials manufactured from renewable resources. An important class of nanomaterials has been nanofibers and fibrils from different cellulose sources and cellulose crystals (whiskers). The cellulose molecules are always biosynthesized in the form of nanosized fibrils; up to 100 glucan chains aggregate together to form cellulose nano-sized microfibrils or nanofibers. These microfibrils can be extracted from the cell walls by three types of isolation processes: simple mechanical methods, a combination of chemical and mechanical methods, or an enzymatic approach. This research program is to develop plant and tree isolated fungi-based biological cellulose and provides essential information to support bioconversion research to develop nano-biofibrils from agro and forest biomass residues. The aim is to modify the fiber surface to render it thermodynamically more compatible to plastics and biopolymers. The separation of nanoreinforcement from natural materials and the processing techniques have been limited to laboratory scale. Therefore, it is important to develop new processing techniques which will be at use in large scale production.

2. Dispersion of cellulose nanofibers in a green polymer and improved manufacturing processes
I will continue my research on dispersion of cellulose nanofibers in a green polymer. This is a logical extension of my dissertation research. Cellulose nanofibers have not been used extensively in common thermoplastics, as poor dispersion of the filler in the matrix of a composite material seriously affects its mechanical properties. Due to their large surface area, nanofibers will take any opportunity to agglomerate. Once that happens, many of the beneficial properties we are targeting are lost. To get around this, chemists have tried to use variations of the dispersion methods that they have used for traditional particles and pigments. This approach just does not work, and in many cases decreases system performance. I am interested in designing a new dispersion method which would improve fiber-matrix adhesion and improve the mechanical performance of the bionanocomposite. This topic offers possibilities to better understand the mechanism of surface thermodynamics and interfacial properties between nanofiber and a polymer matrix. The effect of processing techniques such as extrusion or injection on the properties of nanocomposites needs to be investigated.

3. 100% biodegradable and renewable bionanocomposite applications
My ongoing and prospective research related to bionanocomposite will be focusing on the biocomposite film for packaging application and bio-nanofilm in the ophthalmic industry. The fairly new idea of bionanocomposites, in which the reinforcing material has nanometer dimensions, is emerging to create value-addedmaterials with superior performance and extensive applications. In biocomposites, the biofibers serve as reinforcement by enhancing the strength and stiffness to the resulting composite structures. Fully biodegradable synthetic polymers have been commercially available since 1990, such as poly(vinyl alcohol) (PVA), poly(lactic acid) (PLA), polyhydroxyalkanoates (PHA), poly(ß-hydroxyalkanoate)s (PHB) and polycaprolactone (PCL). When a biodegradable material is obtained completely from renewable resources, we may call it a green polymeric material. Recent work on biocomposites reveals that in most cases the specific mechanical properties of biocomposites are comparable to widely used glass fiber reinforced plastics. Recognizing the growing need for a new approach, nanofilm developed ultra-thin coatings to protect, enhance and condition this new breed of optical surfaces and coatings. My research interest is to launch a new product with ophthalmic coatings as a companion product with eyeglass lenses featuring nanofilm’s coatings