Bamboo becomes a treasure house of new material resources
With an area of 7.01 million hectares of bamboo forest, China is the country with the most abundant bamboo resources in the world. The bamboo resources, area and stock are the first in the world. So far, there are 857 species of bamboo plants belonging to 39 genera in China, accounting for 52% of the 1642 species of bamboo in the world.
Bamboo has the advantages of renewable, absorbing carbon dioxide, non-polluting and degradable products, and has a wide range of uses. It can realize the use of all bamboo, almost without waste. From cutlery such as knives, forks, spoons, cups and plates to household daily necessities, automotive interiors, electronic product casings, and even bamboo lattice fillers for cooling towers in industrial fields, bamboo products are gradually entering people's lives.
Maximize the utilization of bamboo resources through scientific and technological innovation, and gradually develop and utilize bamboo as a substitute for wood, plastic, steel and other materials, forming more than 100 series and more than 10000 varieties of reconstituted bamboo, bamboo woven handicrafts, bamboo fiber products, bamboo carbon products, etc., and bamboo processed products have covered all fields of people's production and life. China is the largest country in the production and trade of bamboo products in the world. In 2020, the output value of the national bamboo industry will be nearly 320 billion yuan.
With the increasing demand for personalized decoration of the home environment, there are more and more researches on transforming environmental protection materials such as wood and bamboo into new materials, but few of them directly process raw bamboo into cellulose composites with ideal optical properties.
Due to the low porosity of bamboo, the time for removing lignin and impregnating polymer from bamboo is longer than that of wood with low density such as Basha wood and poplar, so it is a challenge to prepare transparent bamboo with certain thickness.
The team selected 5-year-old phyllostachys pubescens as the raw material, soaked the green bamboo in the mixed solution of hydrogen peroxide and acetic acid, and reacted lignin with peracetic acid to produce trans-dihydroxylation addition products; Then use simple chemical pretreatment to remove the lignin in the original bamboo. Its removal means the disappearance of "adhesive" (connecting cellulose and hemicellulose), leading to the appearance of more pores, which is conducive to the filling of resin with refractive index matching with bamboo cellulose template.
Finally, after rapid curing process, a new transparent bamboo material with excellent optical transmission performance, tensile resistance, surface decoration and aesthetic value came into being.
Compared with other transparent biomass samples prepared by different polymer impregnation methods, the curing time of transparent raw bamboo is very short, so it shows a significant potential for rapid preparation and processing.
Transparent bamboo transformed electromagnetic shielding material
With the rapid development of wireless communication technology and electrical equipment, the convenience of people's life has been increased, but the problems of electromagnetic interference, radiation and electromagnetic leakage have also increased. The deteriorating electromagnetic environment not only endangers people's health, but also interferes with the normal operation of various electronic equipment.
Therefore, it is very necessary to study electromagnetic shielding materials for buildings and homes.
Professor Wu Yan said that the direct processing of raw bamboo into cellulose composite materials not only reduces a lot of energy consumption in mechanical pretreatment steps, but also preserves the complete cellulose skeleton structure of raw bamboo. In this study, they directly formed and processed raw bamboo in its own form, which not only expanded the use of biomass optical transparent materials, but also became more diverse in modeling.
It is reported that the wall thickness of the new transparent bamboo material can reach 6.23 mm, the light transmittance is about 60%, the illumination is 1000 lux, the water absorption mass change rate is less than 4%, the longitudinal tensile strength reaches 46.40 MPa, and the surface performance is 80.2HD (the hardness unit measured by Brinell hardness tester).
The team members formed a composite device of transparent bamboo, transparent bamboo chips and electromagnetic shielding film. "The overall structure is similar to the common honeycomb board," Wu Yan said. Among them, transparent bamboo chips serve as the core skeleton, transparent bamboo chips as the panel, and tin-doped indium oxide film as the functional layer.
After research, Wu Yan's team found that this composite device can show significant heat insulation, thermal insulation and electromagnetic shielding performance, and has broad prospects in the field of home and building decoration materials.
"This method of directly processing raw bamboo into cellulose templates and then synthesizing transparent materials will greatly reduce the steps of mechanical processing of raw materials in the early stage and molding of raw materials in the later stage, not only reducing energy consumption, but also reducing the waste of petrochemical resources," Wu Yan said. At the same time, this method can also be extended to other biomass materials with high density and low porosity.
source:https://www.tnc.com.cn/info/c-001001-d-3729223.html