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Low temperature plasma treatment to improve the water resistance of wood bonding strength

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15 Apr,2021

Low temperature plasma treatment to improve the water resistance of wood bonding strength:
Because of its excellent performance and environmental protection factors, wood-based panel plays an important role in furniture, building materials and other fields. However, the wood-based panels made of urea-formaldehyde resin glue, phenolic resin glue and melamine formaldehyde resin glue are widely used at present, which have problems such as large consumption of petroleum resources and continuous release of formaldehyde.

CRF Low temperature plasma treatment
In order to further improve the environmental protection of wood-based panel products, soybean protein adhesive (soybean gum) was modified by physical, chemical or biological methods to make the wood surface have good wettability, which has been widely paid attention in the field of wood adhesive.
However, compared with aldehyde adhesives, bean adhesives still have some shortcomings in terms of water resistance, bonding strength and adhesive quantity. In order to improve the quality of wood-based board, plasma surface modification is one of the effective methods to improve the wettability of glue on board surface.


A large number of polar oxygen-containing functional groups can be formed on the surface of poplar veneer under oxygen RF plasma treatment, and the surface roughness is improved, which is beneficial to adhesive bonding.

Using atmospheric pressure air dielectric barrier discharge plasma technology to treat veneer surface simplifies the process and creates conditions for industrial application. The parameters such as plasma treatment speed and power have obvious effects on the physical and chemical properties of the sheet surface.


Wood was modified by atmospheric plasma to improve its surface wettability. Using nanocellulose (NCC) modified soybean glue as binder, the surface of poplar veneer was treated by atmospheric pressure air dielectric barrier discharge plasma to prepare soybean glue plywood.


After atmospheric plasma treatment, the wood surface was etched, and a large number of polar functional groups were produced, which improved the wettability of the glue on the wood surface, thus increasing the bonding strength of the wood, and further reducing the amount of adhesive.


On the one hand, the surface of poplar veneer is physically etched and micro-nano pores are produced after plasma treatment, which is beneficial to the penetration of modified soybean gum into the veneer surface. On the other hand, the high-energy particles generated by the atmospheric low temperature plasma make the surface of poplar veneer change chemicly, produce more polar functional groups containing oxygen and nitrogen, improve the polar interaction between the glue and wood, and make the glue more easily penetrate into the pores of the veneer surface, forming a deep nail structure.
Therefore, the interfacial bond strength of the plywood treated by low temperature plasma can be significantly improved, and the bond strength of the plywood treated by low temperature plasma can reach 0.78MPa, which is increased by 20% and reaches the national standard. This indicates that the normal pressure and low temperature plasma treatment can reduce the amount of glue and reduce the production cost under the condition that the bonding strength reaches the standard.


The high energy particles in the plasma impact the wood surface at high speed and degrade the polymer in the wood cell wall. These small irregular scratches on the surface of poplar increased the surface roughness, promoted the penetration of modified bean gum into the surface of poplar veneer, and increased the interfacial bonding strength.


The surface of poplar veneer was etched to form a microporous structure, and the surface roughness of veneer was increased, which improved the permeability of nano-cellulose modified soybean gum. After treatment, new free radicals were generated on the surface of poplar veneer, which enhanced the polarity between modified bean gum and veneer surface.

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