Add boron ion "package", pulp foam bid farewell to "soft"

It was learned from the Qingdao Institute of Bioenergy and Processes, Chinese Academy of Sciences that the metabolomics research group led by researcher Cui Qiu of the institute adopted the boron ion cross-linking strategy, combined with the synergy of chitosan and a small amount of cationic polyacrylamide (CPAM), A high-strength, fire-resistant, antibacterial pulp foam was developed
.

Porous materials with high porosity, low density and light weight have broad application prospects in the fields of packaging, construction, health care and chemical industry
.
With the enhancement of people's awareness of environmental protection and the demand of "two-carbon" strategy, the use of renewable and biodegradable cellulose to prepare porous materials has become a research hotspot in recent years
.

Pulp foam is an inexpensive and environmentally friendly new porous material
.
It uses pulp fiber as raw material, uses surfactant to foam in pulp fiber dispersion under rapid stirring, prevents fiber flocculation, and forms a uniform porous structure, which is filtered and dried to obtain foam
.
However, the foam materials prepared by using pulp fibers alone have poor strength, are flammable, and are susceptible to bacteria, which cannot meet the requirements of practical applications
.

In fact, the self-supporting effect of plant cell walls is related to the strong interlocking structure of its components
.
Among them, a small amount of boron ions enhances the support of the cell wall by covalent bonding with the oxygen-containing groups of the lignocellulosic components
.
On the other hand, borate is also a commonly used flame retardant
.

Inspired by this, the researchers conducted a proof-of-concept experiment in the early stage.
After the introduction of boron ions during the molding process of pulp foam, the cross-linking effect between boron ions and pulp fibers greatly improved the mechanical strength of pulp foam and its compression.
It is 28 times stronger than boron ion-free pulp foam and imparts some flame retardancy and self-extinguishing properties
.

In order to further improve the mechanical strength and flame retardancy of the pulp foam material, endow it with good antibacterial properties and increase its practicality, the researchers continued to introduce an appropriate amount of chitosan and A small amount of CPAM
.
Studies have confirmed that since boron ions can form strong covalent bonds with the hydroxyl groups of cellulose and chitosan, there are electrostatic bonding and intermolecular hydrogen bonding between cellulose, chitosan and CPAM.
The compressive strength of the pulp foam under 50% strain is 6 times that of the same boron ion cross-linked but without chitosan and CPAM pulp foam, and it is higher than most of the current reports.
Cellulose based porous material
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It is worth mentioning that CPAM with an dosage of only 0.
5% (relative to the dry weight of pulp) can replace chitosan with an dosage of 30%, and a pulp foam with the same mechanical strength can be obtained, which can greatly reduce the preparation cost of pulp foam
.
At the same time, due to the synergistic effect of boron ions, chitosan and CPAM, the pulp foam has excellent fire resistance, heat insulation, antibacterial and sound absorption properties
.
Its low density, high mechanical strength and good thermal insulation are already comparable to common commercial fireproof mineral wool, porous inorganic materials and foam glass products
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In addition, the filtrate produced during the foam preparation process can be completely recovered and reused
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According to reports, the high-performance pulp foam prepared in this study is expected to be applied in the fields of high-quality packaging, heat insulation, photothermal conversion, and sound absorption
.
The related research results were published in "Carbohydrate Polymers"
.