阅读说明：本技术 一种碳纳米管/木材复合材料的制备方法 (Preparation method of carbon nano tube/wood composite material ) 是由 张尚 倪竣 丁青锋 于 2021-10-13 设计创作，主要内容包括：本发明公开了一种碳纳米管/木材复合材料的制备方法,包括以下步骤:步骤S1,通过浓H-(2)SO-(4)和浓HNO-(3)对碳纳米管进行处理,得到共价改性的碳纳米管;步骤S2,将所述共价改性的碳纳米管置于聚氨酯稀释液中,超声分散20～30min后得碳纳米管聚氨酯复合组分,将碳纳米管聚氨酯复合组分作为浸渍液,其中,所述聚氨酯通过乙酸丁酯进行稀释；步骤S3,将木材置于步骤S2的浸渍液中,采用满细胞法对其浸渍固化,加入聚氨酯延迟性催化剂,在0.8～1.2MPa压力下保压20～30min,经过保压后的木材在O.06～0.1MPa的环境下真空处理15～20h,然后经过室温固化得碳纳米管复合木材。本发明对碳纳米管进行共价改性,可使碳纳米管分散并固定的在木材内部,得到一种强度高的复合木材。(The invention discloses a preparation method of a carbon nano tube/wood composite material, which comprises the following steps of S1, concentrating H 2 SO 4 And concentrated HNO 3 S2, placing the covalently modified carbon nanotube in a polyurethane diluent, performing ultrasonic dispersion for 20-30 min to obtain a carbon nanotube polyurethane composite component, and taking the carbon nanotube polyurethane composite component as a dipping solution, wherein the polyurethane is diluted by butyl acetate; step S3, putting the wood into the steeping liquor of the step S2, adopting a full cell method to perform steeping and curing on the wood, adding a polyurethane delayed catalyst, maintaining the pressure for 20-30 min under the pressure of 0.8-1.2 MPa, and maintaining the pressureAnd (3) carrying out vacuum treatment on the wood for 15-20 h in an O.06-0.1 MPa environment, and then curing at room temperature to obtain the carbon nano tube composite wood. The invention carries out covalent modification on the carbon nano tube, so that the carbon nano tube can be dispersed and fixed in the wood, and the composite wood with high strength is obtained.)

1. A preparation method of a carbon nano tube/wood composite material is characterized by comprising the following steps: the method comprises the following steps:

step S1, passing through rich H₂SO₄And concentrated HNO₃Processing the carbon nano tube to obtain a covalent modified carbon nano tube;

step S2, placing the covalently modified carbon nano tube in a polyurethane diluent, performing ultrasonic dispersion for 20-30 min to obtain a carbon nano tube polyurethane composite component, and taking the carbon nano tube polyurethane composite component as an impregnation liquid for later use;

and S3, placing the wood into the impregnation liquid obtained in the step S2, impregnating and curing the wood by adopting a full cell method, adding a polyurethane delayed catalyst, maintaining the pressure for 20-30 min under the pressure of 0.8-1.2 MPa, carrying out vacuum treatment on the wood subjected to pressure maintaining for 15-20 h under the environment of O.06-0.1 MPa, and then curing at room temperature to obtain the carbon nano tube composite wood.

2. The method for preparing a carbon nanotube/wood composite material according to claim 1, wherein: in step S1, the rich H₂SO₄And concentrated HNO₃Is 3: 1.

3. The method for preparing a carbon nanotube/wood composite material according to claim 1, wherein: in step S1, the carbon nanotubes are multi-walled carbon nanotubes.

4. The method for preparing a carbon nanotube/wood composite material according to claim 1, wherein: the method for processing the carbon nano tube comprises the following steps:

a, placing the carbon nano tube in concentrated H₂SO₄And concentrated HNO₃In the mixed acid, ultrasonic dispersion is carried out for 30min at room temperature;

b, placing the product obtained in the step a in a three-necked bottle for acidification treatment for 3-6 h, wherein the acidification temperature is only 50-60 ℃;

c, cooling the acidified product to room temperature, diluting the acidified product with distilled water, then performing vacuum filtration, and repeatedly cleaning and filtering the filtrate until the filtrate is neutral;

and d, drying the product obtained in the step c in a vacuum drying oven to obtain the covalent modified carbon nano tube, wherein the drying temperature is 80-100 ℃, and the drying time is 24 hours.

5. The method for preparing a carbon nanotube/wood composite material according to claim 1, wherein: in step S2, butyl acetate is added to the polyurethane to obtain a polyurethane diluent.

6. The method for preparing a carbon nanotube/wood composite material according to claim 5, wherein: the mass ratio of the polyurethane to the butyl acetate is 1: 1.

7. The method for preparing a carbon nanotube/wood composite material according to claim 1, wherein: in step S2, the mass ratio of the carbon nanotubes to the polyurethane diluent is 0.05%.

8. The method for preparing a carbon nanotube/wood composite material according to claim 1, wherein: in step S3, before the wood is added into the impregnation liquid, the wood is placed in an environment of 0.06MPa for vacuum treatment for 20-30 min.

9. The method for preparing a carbon nanotube/wood composite material according to claim 1, wherein: in step S3, the polyurethane delayed action catalyst is model DY-5508 delayed action catalyst.

10. The method for preparing a carbon nanotube/wood composite material according to claim 1, wherein: in step S3, the room temperature curing time is 3 hours, wherein the dipping solution on the surface of the specimen is wiped away with filter paper before the room temperature curing.

Technical Field

The invention relates to the technical field of wood structure composite materials, in particular to a preparation method of a carbon nano tube/wood composite material.

Background

Wood is a sustainable and widely used building material, and many projects, such as the wengowa high-wood building and the japan olympic main arena, use wood as a main building material because it has better economic and environmental benefits than the current building materials such as steel and concrete. The existing wood structure building still faces many challenges, the natural wood cannot meet the mechanical performance requirements advocated by the energy-saving building plan of the housing of the people's republic of China and the urban and rural construction department, and the mechanical strength of the natural wood prevents the natural wood from being applied to middle and high-rise buildings. Therefore, the development of strong, heat-insulating and energy-saving structural materials is very necessary for the wood structure building.

The main bottlenecks in the development of the current heavy wood structure building have the following points; 1) the mechanical property of the wood is low, and the requirements of large span and multi-story high-rise buildings are difficult to meet; 2) wood prices are rising, and additionally trade battles between countries result in restricted import of wood; 3) the performance requirements of the wood structure building materials are difficult to meet due to the poor performance of domestic artificial forests.

The physical and chemical methods are mainly used in academia and industry to modify wood so as to achieve the purpose of improving the physical and mechanical properties of the wood. The former mainly involves physical means such as compression, heat treatment, and surface reinforcement (fibrous material, reinforcing bars, steel), and the latter involves chemical reaction inside the wood by impregnation (acetylation, furfuryl alcohol, resin). These modification methods aim at enhancing or improving the properties of wood, but all have certain drawbacks. Fiber reinforced composites have received attention in the wood field in the early nineties of the last century and some research work has been carried out. The fiber reinforced composite material technology is that FRP is adhered to the outside of wood by using an adhesive and a coupling agent so as to improve the bearing capacity of the material. The fiber reinforced material mainly comprises Glass Fiber (GFRP), Carbon Fiber (CFRP) and Aramid Fiber (AFRP), but the industrialization of the fiber reinforced composite is not realized due to poor bonding process, pretension of the fiber material, compression resistance of the composite material and the like.

Compared with the existing high-performance fibers (GFRP, CFRP and AFRP), the Carbon Nano Tube (CNT) has more excellent comprehensive performance and is an ideal selection reinforcing material for future light high-performance multifunctional composite materials. The carbon atoms in the carbon nano tube are hybridized with SP2 to form C-C covalent bonds, which determines that the CNT has strong mechanical properties, and in addition, the hollow cage structure of the CNT can deform under the strong action of external force, so that the CNT can show good flexibility. Furthermore, bond fracture, plastic deformation fracture or brittle fracture does not occur when the CNT is subjected to tensile and bending strain. Therefore, due to the unique structure of the CNT, the CNT has high elastic modulus and strength and good plasticity, toughness and flexibility. Dispersing carbon nanotubes in a resin matrix to improve the properties of the resin matrix is the most common method for preparing carbon nanotube composites. Achieving high content and high orientation dispersion of carbon nanotubes in a resin, however, remains a significant challenge. The carbon nano tube is assembled into a macroscopic material, and the design and the preparation of the composite material based on the macroscopic material can avoid the challenges, so that the macroscopic material becomes an important way for realizing high-content and high-orientation distribution of the carbon nano tube in the composite material.

In order to improve the performance of wood, the carbon nano tube can be compounded with the wood, but the carbon nano tube compounded wood has the following problems: 1) the carbon nano tube has too large length-diameter ratio, so that the carbon nano tube is easy to curl; the carbon nano tube has the diameter less than 100nm, the length reaching several micrometers or even millimeters, a large length-diameter ratio, extremely large surface area, extremely easy agglomeration and winding, and chemical inertness on the surface, so that the carbon nano tube is difficult to uniformly disperse in any solution; 2) when carbon nanotubes are used as the composite material; how to improve the dispersibility (acidification) of the carbon nanotubes, how to enter the interior of the wood in which the carbon nanotubes enter (impregnation), how to react the carbon nanotubes with the wood (covalent modification of the carbon nanotubes makes the carbon nanotubes have active groups such as hydroxyl groups and the like), how to stably disperse the carbon nanotubes in the interior of the wood (dispersion of the carbon nanotubes in a solution), and how to fix the carbon nanotubes in the interior of the wood (chemical reaction between the covalently modified carbon nanotubes containing hydroxyl groups and the wood to produce hydrogen bonds); 3) how to ensure a bonding interface requires good interfacial bonding to achieve payload transfer through the CNT/wood interface, which is a necessary condition to improve the mechanical properties of the polymer composite. At present, no good solution exists in the market, and the application particularly provides a preparation method of a carbon nano tube/wood composite material.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention discloses a preparation method of a carbon nano tube/wood composite material.

The invention discloses a preparation method of a carbon nano tube/wood composite material, which comprises the following steps:

step S1, passing through rich H₂SO₄And concentrated HNO₃Processing the carbon nano tube to obtain a covalent modified carbon nano tube;

step S2, placing the covalently modified carbon nano tube in a polyurethane diluent, performing ultrasonic dispersion for 20-30 min to obtain a carbon nano tube polyurethane composite component, and taking the carbon nano tube polyurethane composite component as an impregnation liquid for later use;

and S3, placing the wood into the impregnation liquid obtained in the step S2, impregnating and curing the wood by adopting a full cell method, adding a polyurethane delayed catalyst, maintaining the pressure for 20-30 min under the pressure of 0.4-1.2 MPa, carrying out vacuum treatment on the wood subjected to pressure maintaining for 15-20 h under the environment of O.06-0.1 MPa, and then curing at room temperature to obtain the carbon nano tube composite wood.

Further, in step S1, the rich H₂SO₄And concentrated HNO₃Is 3: 1;

further, in step S1, the carbon nanotubes are multi-walled carbon nanotubes;

further, the method for processing the carbon nano tube comprises the following steps:

a, placing the carbon nano tube in concentrated H₂SO₄And concentrated HNO₃In the mixed acid, ultrasonic dispersion is carried out for 30min at room temperature;

b, placing the product obtained in the step a in a three-necked bottle for acidification treatment for 3-6 h, wherein the acidification temperature is only 50-60 ℃;

c, cooling the acidified product to room temperature, diluting the acidified product with distilled water, then performing vacuum filtration, and repeatedly cleaning and filtering the filtrate until the filtrate is neutral;

and d, drying the product obtained in the step c in a vacuum drying oven to obtain the covalent modified carbon nano tube, wherein the drying temperature is 80-100 ℃, and the drying time is 24 hours.

Further, in step S2, butyl acetate is added to the polyurethane to obtain a polyurethane diluted solution.

Further, the mass ratio of the polyurethane to the butyl acetate is 1: 1.

further, in step S2, the mass ratio of the carbon nanotubes to the polyurethane diluent is 0.05%.

Further, in step S3, before the wood is added into the impregnation liquid, the wood is placed in an environment of 0.06MPa for vacuum treatment for 20-30 min.

Further, in step S3, the urethane delayed action catalyst is a delayed action catalyst of DY-5508 type.

Further, in step S3, the room temperature curing time is 3h, wherein the impregnation liquid on the surface of the specimen is wiped away with filter paper before the room temperature curing.

By adopting the technical scheme, the method has the following advantages:

the preparation method of the carbon nano tube/wood composite material firstly adopts concentrated H₂SO₄And concentrated HNO₃The mixed acid is used for carrying out covalent modification on the carbon nano tube, so that the surface of the carbon nano tube or the tail end of the shortened carbon nano tube is opened, the top end of the carbon nano tube contains a certain number of active groups, then the carbon nano tube after the covalent modification is compounded with polyurethane to form impregnation liquid, wood is impregnated in the impregnation liquid by adopting a full cell method, the carbon nano tube can be dispersed and fixed in the wood to form the composite wood, and the composite wood has the performance of the carbon nano tube and has better mechanical property and higher strength compared with the pure wood.

Detailed Description

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.

As described in the background art, the existing carbon nanotubes are difficult to disperse and fix inside wood when they are compounded with wood to improve the mechanical properties of wood. In order to solve the technical problems, the invention discloses a preparation method of a carbon nano tube/wood composite material, which comprises the following steps:

step S1, passing through rich H₂SO₄And concentrated HNO₃Processing the carbon nano tube to obtain a covalent modified carbon nano tube; step S2, placing the covalently modified carbon nano tube in a polyurethane diluent, performing ultrasonic dispersion for 20-30 min to obtain a carbon nano tube polyurethane composite component, and taking the carbon nano tube polyurethane composite component as an impregnation liquid, wherein the polyurethane is diluted by butyl acetate; and S3, placing the wood into the impregnation liquid obtained in the step S2 for impregnation and curing, adding a polyurethane delayed catalyst, maintaining the pressure for 20-30 min under the pressure of 0.8-1.2 MPa, carrying out vacuum treatment on the wood subjected to pressure maintaining for 15-20 h under the environment of O.06-0.1 MPa, and then curing at room temperature to obtain the carbon nano tube composite wood.

In the above-mentioned method firstly making concentrated H₂SO₄And concentrated HNO₃The mixed acid is used for carrying out covalent modification on the carbon nano tube, so that the surface of the carbon nano tube or the tail end of the shortened carbon nano tube is opened, the top end of the carbon nano tube contains a certain number of active groups, and the active functional groups on the surface of the carbon nano tube can improve the hydrophilicity of the carbon nano tube and can be easily dispersed in polar media such as water and the like, so that a foundation is provided for the reaction of the carbon nano tube and other substances or groups, and better composite uniformity and bonding interface strength can be generated with a hydrophilic matrix material; then compounding the carbon nano tube after covalent modification with polyurethane to form impregnation liquid, finally placing the wood in the impregnation liquid for curing, wherein the wood is a porous material, the diameter of a conduit of a needle leaf wood saturated with broad leaf wood is 20-140 micrometers, and the diameter of the carbon nano tube is 2-100 nanometers, so that the carbon nano tube can enter the interior of the wood, the impregnation is carried out by adopting a full cell method, the carbon nano tube can enter the interior of the wood for dispersion and fixation under a pressure-maintaining environment, and the carbon nano tube after covalent modification enters a cell cavity through the conduit or a pore channel of the saturated cell wall to fill the cell cavity, so that the strength of the wood can be improved, and the moisture absorption of the wood can be reduced. The filling of the wood cell cavity by the carbon nano tube can be increasedThe bearing capacity of the material is added, so that the strength of the wood is improved.

In a preferred embodiment, in step S1, the rich H₂SO₄And concentrated HNO₃Is 3: 1;

in a preferred embodiment, in step S1, the carbon nanotubes are multi-walled carbon nanotubes; here, the carbon nanotube is a carbon allotrope such as diamond, graphite or fullerene, and the structure thereof can be regarded as a tube formed by rolling a graphite sheet around a central axis with a certain helicity, and the two ends of the tube are generally sealed by a hemispherical mesh containing pentagons. The carbon nanotubes are classified into single-walled carbon nanotubes and multi-walled carbon nanotubes according to the number of the layers of the curled graphite flakes, the carbon nanotubes formed by curling a single-walled graphite flake are called single-walled carbon nanotubes, and the multi-walled carbon nanotubes are generally formed by stacking a plurality of layers of concentric tubes.

In a preferred embodiment, the method for treating carbon nanotubes comprises the following steps: a, placing the carbon nano tube in concentrated H₂SO₄And concentrated HNO₃In the mixed acid, ultrasonic dispersion is carried out for 30min at room temperature; b, placing the product obtained in the step a in a three-necked bottle for acidification treatment for 3-6 h, wherein the acidification temperature is only 50-60 ℃; c, cooling the acidified product to room temperature, diluting the acidified product with distilled water, then performing vacuum filtration, and repeatedly cleaning and filtering the filtrate until the filtrate is neutral; and d, drying the product obtained in the step c in a vacuum drying oven to obtain the covalent modified carbon nano tube, wherein the drying temperature is 80-100 ℃, and the drying time is 24 hours.

In a preferred embodiment, in step S2, butyl acetate is added to polyurethane to obtain a polyurethane diluent, wherein the mass ratio of the polyurethane to the butyl acetate is 1: 1. the polyurethane is diluted because the viscosity of the polyurethane is high, which brings great difficulty to the subsequent impregnation, and 1: butyl acetate 1 is good at diluting the viscosity of the polyurethane.

In a preferred embodiment, in step S2, the mass ratio of the carbon nanotubes to the polyurethane diluent is 0.05%.

In a preferred embodiment, in step S3, before the wood is added into the impregnation liquid, the wood is placed in an environment of 0.06MPa for vacuum treatment for 20-30 min.

In a preferred embodiment, in step S3, the polyurethane delayed action catalyst is a delayed action catalyst type DY-5508. The polyurethane delayed catalyst is a very special catalyst in polyurethane catalysts, and the catalyst can provide catalytic activity required by polyurethane curing, prolong the service life of a product and provide more operation time for construction. Unlike inhibitors, polyurethane delayed catalysts are relatively delayed rather than absolutely delayed, with low front-end activity compared to conventional catalysts, and comparable overall activity.

In a preferred embodiment, in step S3, the room temperature curing time is 3h, wherein the dipping solution on the surface of the specimen is wiped away with filter paper before the room temperature curing.

The carbon nano tube/wood composite material after room temperature curing is used for judging the quality of the composite material by detecting the weight gain ratio and the creep property of the composite material, wherein the weight gain ratio (WPG) is calculated by the following method:

the above formula M1 is the oven dry mass after the carbon nanotube/wood composite material is compounded, and M2 is the oven dry mass before the carbon nanotube/wood composite material is compounded. After the carbon nano tube/wood composite material is obtained, the carbon nano tube/wood composite material is required to be placed in a drying oven and dried for 24 hours in the environment of 103 ℃, and the oven-dry quality of the carbon nano tube/wood composite material after being compounded can be obtained.

In order to further detect the performance of the carbon nanotube/wood composite material, the creep performance of the carbon nanotube/wood composite material needs to be measured, the continuous load capacity, the static bending creep performance and the creep service resistance of the carbon nanotube/wood composite material can be measured and determined by measuring the creep performance, and the creep performance of the carbon nanotube/wood composite material can be detected and analyzed according to the national standard GB/T31291 evaluation on load duration effect and creep performance of wood and wood-based products and LY/T1975-2011 evaluation on continuous load and creep influence of wood and engineering composite wood. The test is carried out according to an ASTMD 6815-09 four-point bending test method, the loading level of a creep test specimen is 60% of the static bending failure strength of the specimen, a creep deflection, an environment temperature (t) and a Relative Humidity (RH) of the specimen are recorded every 30 minutes by a creep monitoring system and a temperature and humidity monitor, and the load of each specimen is relieved after 90 days.

The creep deflection is equal to a static deflection value actually measured by a creep detection system at each time point, the creep rate refers to the change rate of the creep deflection along with time, and the creep coefficient (FD) is the ratio of the creep deflection of the test piece to the initial creep deflection of the test piece.

The creep rate of the carbon nano tube/wood composite material is qualified, the undamaged creep stress of the carbon nano tube/wood composite material tends to be stable within 90 days of test time, and the requirement of the following formula is met:

in the above-mentioned formula,

D_i-initial creep deflection in millimeters (mm);

D₃₀-specimen creep deflection measured on day 30 in millimeters (mm);

D₆₀-specimen creep deflection measured on day 60 in millimeters (mm);

D₉₀-creep deflection of the specimen measured on day 90 in millimeters (mm).

Determination of qualified creep coefficient (FD) for carbon nanotube/wood composites, the creep coefficient of the undamaged test specimen after 90 days of testing should be less than 2.0, expressed as follows:

in the above formula D₉₀And D_iCreep deflection on day 90 and initially for the test pieces, respectively. The preparation method adopts the applicationThe creep rate and the creep coefficient of the carbon nano tube/wood composite material prepared by the method meet the requirements, so that the problems that the natural wood is low in mechanical strength and cannot be applied to middle and high-rise buildings can be solved, and the carbon nano tube/wood composite material has wide market prospect.

Finally, it should be noted that: the above embodiments are only used to illustrate the present invention and do not limit the technical solutions described in the present invention; thus, while the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted; all such modifications and variations are intended to be included herein within the scope of this disclosure and the present invention and protected by the following claims.