2- Cellulose Based Micro and Nano Composite Technology

Cellulose fibers have well established their reputation as reinforcement to plastics. Because of their wide abundance, their renewable and environmentally benign nature, and their outstanding mechanical properties, a great deal of attention has been paid recently to cellulosic micro- and nano-fibrillar structures as components in composites, which is currently considered one of the most promising areas of scientific and technological development.

In our Bio-Nanocomposite Manufacturing Group, we are focusing on an integrated research project that its scope ranges from the isolation, mass production, to the development of applications of micro- and nano-fibers. In recent years, a unique fungus has been utilized in a novel bio-pretreatment for cellulose fibers that can substantially improve the yield and efficiency of the current mechanical process applied to isolate cellulose microfibrils. The use of agricultural residues for isolation of cellulose nanofibres is another concentration of our group. This opens up the doors for non-wood based fibers in value added products. Micro and nanofibers have been now widely used as a food and rheology additive. In addition, the isolated nanofibers have proven to be strong and transparent as larger diameter fibers have been excluded and fiber distribution has been improved. When combined with high refractive-index polymer, the resulting composites can transmit up to 80% of visible light compare to the pure polymer. This type of cellulosic nanocomposites is excellent materials for making flexible, foldable and optically transparent films. Surface modification and orderly orientation of fibers achieved by chemical treatment and applying magnetic force can enhance mechanical, optical and electrical properties of the composites.

 

Group Research Project:

 

Cellulose Nanofibers Reinforced Epoxy Composites Design and Manufacture
(Peiyu Kuo, Ph.D Candidate)
Epoxy resins are an important class of high performance thermosetting polymers that are widely used in the automotive, construction, electronic and aerospace industries. Nevertheless, epoxy resins do have some disadvantages, like high-cost, relative low modulus and long curing profile. As well, recent awareness of the toxicity of Bisphenol A (BPA), the major component of epoxy resins, combined with the scarcity of fossil resources imply necessary changes in the field of epoxy resins. Therefore, there are two main parts in this research project. First, cellulose nanofibers are introduced into petro-based epoxy resins to get higher mechanical performance. Secondly, utilization of liquefied bark as BPA to study these cured bio-based epoxy resins properties. We expect to achieve bio-epoxy composites with high mechanical performance reinforced by cellulose nanofibers.

Production of cellulose Nano-fiber filtration membranes and its orientation in Nano-sized separation field
(Dr. Xinjin Sui Postdoctoral Fellow)
Cellulose nanofibers are one class of natural fibers that have resulted in structures with remarkable mechanical properties. Cellulose nanofibre membranes were prepared by the casting method with different cellulose nanofibre loadings, which were exposed to tensile test. By employing cellulose nanofiber in conjunction with polymer with appropriate molecular weight cutoff, homogeneous membranes were produced with low cost. The protein complexes or other nano-sized particles were effectively separated from solution. A number of TEM techniques have been used to examine protein fouled filtration membranes.

Cellulose Nanofiber filtration membrane as seen by transmission electron microscopy

Development of Optically Transparent Film of Bacterial Cellulose for the Application of Flexible Organic Light Emitting Diode (OLED) Display
(Dr. Julasak Juntaro Postdoctoral Fellow)
A novel approach to utilize bacterial cellulose nanofibrils in the development of next generation flexible TV screen, computer screen, PDA screen and other advertising display systems is investigated. Optically transparent nanocomposite film of bacterial cellulose and resin is fabricated and used as a substrate for the OLED display. Bacterial cellulose is an extracellular product of Acetobacter xylinum. Its fibril features excellent intrinsic properties due to its high crystallinity and high elastic modulus of 138 GPa. Its fibril has ribbon shape with the diameter ranges from 8 to 50 nm, which is composed of a bundle of much finer microfibrils of 2 to 4 nm in diameter. Its nano-size enables the production of optically transparent film as any element with diameter less than one-tenth of the visible light wavelength is free from light scattering. Bacterial cellulose will also help to restrict the thermal expansion of the nanocomposite film as its coefficient of thermal expansion is as low as that of glass (CTE < 8.5 ppm/K). We expect to achieve substrates with high transparency, high tensile strength, and low thermal expansion that will ultimately lead to a flexible OLED display.

Development of cellulose Nano-fiber reinforced composite substrate for OLED application
(Sarute Ummartyotin, Ph.D Candidate)
New visiting PhD student from Chulalongkorn University Thailand, Sarute, have joined Prof. Sainís research group for one year. He will be working on the cellulose nano-scale fiber reinforced composite substrate for OLED application. In this research, the acrylic UV-curing systems were investigated based on the requirements of optical, thermal, as well as mechanical properties. In addition, he will emphasize on the preparing the conductive polymer layer coated on nano-cellulose composite substrate. Conductive polymer plays an important part to be formed as thin layer acted as the media between anode and cathode for hole and electron transport, respectively. The ink-jet printing will also be emphasized, promising us as high potential technique in order to form epitaxy conductive polymer film growth. Then, the capability as OLED device will be determined.

Development of inkjet printable OLED device on bacterial cellulose film
(Dr. Shawn Wang, Postdoctoral fellow)
Since efficient organic light-emitting device (OLED) was first reported great progress has been made to utilize OLED technology in the field of displays because of its unique properties, such as lightweight, low drive voltage, wide view angle and high resolution. In this proposed project, we aim to find an optimized procedure to prepare the OLED device by inkjet printing on a surface of transparent bacterial cellulose nanocomposite film. A single layer OLED device with a structure of ITO-PEDOT: PSS-Ag paste is employed to characterize the manufacture process and the property of OLED device. The OLED device will be fabricated by a layer by layer printing method with a inkjet printer. The optical properties and the general thermal properties will be characterized and the electrical and luminance properties will also be measured.

 

Surface modification of Nano-cellulose fiber for improving its compatibility to polymers
(Seema Khatr, Ph.D Candidate)
The surface chemistry of Nano fibers is not designed to match surface chemistry of polymers like polyethylene which has high surface energy where as surface energy of cellulose is low. My research project will focus on study of suitable kind of surface energy to make them dispersible.

Isolation of Cellulose Nanofibers: Elucidation of novel approach utilizing enzymatic pretreatment
(Sreekumar Janardhnan, Ph.D)

 

Chemical Modification of Cellulose Fiber and its Orientation in Magnetic Field
(Smith Sundar, Ph.D Candidate)
The objective of this project is to enhance the properties of cellulose based composites by re-defining orientation of cellulose fiber in a biopolymer matrix. This can be achieved by combining concepts of modification of hydroxyl groups with a magnetically susceptible entity such as iron. Such modified fibers can be oriented in a biopolymer matrix when subjected to a magnetic field. It is expected that iron modified cellulose fibers can achieve optimal orientation and dispersion in a biopolymer matrix. Cost effective methods and technology transfer to the industry for commercialization are priorities. A successful outcome of this study will answer real world solution in enhancing mechanical, optical and electrical properties of bio-based composites and commercialization of the concept.

 

Magnetically oriented wood based cellulose fiber as seen by Confocal microscopy

                                

Production and Characterization of Optically Transparent Nnanocomposite Films
(Crystal Wu, M.Sc)
The nano-scaled cellulosic fibers, which are the building fundamentals of plants, have proven to provide effective reinforcement in the composite field. They not only have excellent mechanical properties comparable to steel, but also they transmit most of the light because of their microscopic size. My projects involves using these nanofibres in strengthen the green polymers while sustain the optical transparency to produce optical transparent films.

Comparison of transparency of cellulose composite sheet:

Microfiber Sheet    Nanofiber Sheet   Nanocomposite

Microfiber Sheet                Nanofiber Sheet                Nanocomposite

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