Nanomaterials Nanocellulose

Nanocellulose Introduction

With the continuous progress of society and human civilization, non-renewable resources such as coal and oil are constantly being consumed, the pressure on the earth’s environment is also increasing, and sustainable development has also risen to the national strategic level. The use of renewable resources, especially green bioenergy, will be an important direction for future research and development applications.

Cellulose is abundant in nature. Cellulose is one of the more basic components of plant tissues such as trees that are very common in our lives. In addition to the large reserves in plant tissues, cellulose can also be continuously produced by animals and microorganisms. It is a typical representative of green renewable natural biopolymers. Cellulose has many superior biochemical properties, such as biodegradability, hydrophilicity, chirality, and modifiability. In 1886, scientists first discovered that Acetobacter xylinum can produce a bacterial cellulose (BC), whose particle size can reach tens to one hundred nanometers. Cellulose with nanoscale like BC is called nanocellulose. The source classifies cellulose into bacterial cellulose plant cellulose and animal cellulose and categorizes it according to molecular size function preparation method and main source as microfibrillated cellulose nano-microcrystalline cellulose and bacterial nanocellulose. Nanocellulose shares cellulose features such as renewability and biodegradability alongside hydrophilicity and chemical modifiability while offering superior properties like an extremely high specific surface area together with strong adsorption capacity and high Young’s modulus and reactivity. It can form a specific network nanomolecular structure in solution, and is therefore widely used in papermaking, optoelectronics, food, cosmetics, medicine, life sciences, automobiles and other fields.

Preparation of Nanocellulose

Common methods for preparing nanocellulose include: The biochemical method produces nanocellulose particles which are colloidal and known by various terms including nano whiskers and nanocrystalline cellulose. The nanocellulose produced through physical and mechanical techniques such as microjet high-pressure homogenization and grinding manifests primarily as fibrous structures known as nanocellulose fibers or cellulose microfibrils. Microjet high-pressure homogenization technology has the characteristics of high pressure, uniform force, and strong controllability. Compared with the acid hydrolysis method, the nanocellulose fibers obtained by high-pressure homogenization treatment require a much shorter cycle, and the efficiency is greatly improved. It is more environmentally friendly and energy-saving, and is more suitable for continuous batch industrial production. Compared with other mechanical means such as high shear technology, high-pressure homogenization has a stronger refining effect and a more uniform product. At present, high-pressure homogenization technology is mainly used in the fields of chemistry, pharmaceuticals, special food production, and bioengineering. Some researchers have used high-pressure homogenization technology to prepare starch nanospheres, which have a good spherical morphology and a particle size distribution range of 50-250nm.

Common Application Cases of Nanocellulose

1. Nanocellulose can also be used as various medical materials (drug sustained release, medical implants, biological tissue engineering, antibacterial agents, ), ion adsorption and exchange materials, biofunctional materials (immobilized enzyme carriers, DNA marker biosensors, bioimaging, endotoxin adsorbents), etc., and is expected to prepare cellulose functional materials and cellulose membranes with optical, electrical, magnetic and other properties. Its potential uses are liquid crystal polymers, sensitive elements, intelligent identification systems, bioactive and biocompatible materials, etc.
2. Nanocellulose aqueous suspension can form a stable colloidal liquid under strong shear force or high-pressure homogenization, and can be used as an efficient additive for medicines, foods, cosmetics and cement.
3. Nanocellulose has emulsifying and thickening effects, can withstand high and low temperatures, and looks like cream. It can replace cream to reduce the calories of dairy products and is an ideal weight loss food.
4. Nanocellulose can also be made into lithium batteries together with polyethylene.
5. Introducing groups such as cinnabar, ether, ester, and fluorine on the surface of nanocellulose, after chemical modification, it is used as a new type of fine chemical product in the filling material of liquid chromatography columns.
6. The suspension of nanocellulose will be oriented under the action of magnetic field or low shear force, and this orientation still exists after drying into solid, which makes nanocellulose have the special optical properties of chiral nematic liquid crystal phase. The color of circularly polarized light reflected by this film changes with the angle of incidence. Based on this, nanocellulose can be used for fluorescent color-changing pigments, especially for the manufacture of fluorescent color-changing inks. Nanocellulose offers unique optical properties that resist duplication through printing or photocopying which makes it a valuable material for creating anti-counterfeiting labels, papers and sophisticated color-changing inks.
7. Improved properties of polymer composite materials: Nanocellulose serves as a renewable nanometer-sized reinforcing material which enhances the mechanical properties and transparency of natural polymers including polyhydroxyoctanoate, starch, silk, and butyl acetate cellulose as well as synthetic polymers like polyvinyl chloride (PVC), polylactic acid (PLLA), polypropylene (PP) and polyoxyethylene (POE). The high Young’s modulus and thermal stability of nanocellulose enables the composite material formed when nanocellulose suspension mixes with polyethylene oxide aqueous solution under high pressure to achieve elevated melting points in the dried solid film and gain more than tenfold tensile strength when combined with polyethylene glycol.