CN111319109A

CN111319109A - Preparation method of flexible hydrophobic reversible photochromic wood and wood prepared by same

Info

Publication number: CN111319109A
Application number: CN202010085652.5A
Authority: CN
Inventors: 孙庆丰; 蔡泰龙; 王超; 李松
Original assignee: Zhejiang A&F University ZAFU
Current assignee: Zhejiang A&F University ZAFU
Priority date: 2020-02-10
Filing date: 2020-02-10
Publication date: 2020-06-23
Anticipated expiration: 2040-02-10
Also published as: CN111319109B

Abstract

The invention relates to a preparation method of flexible hydrophobic reversible photochromic wood and the prepared wood, belonging to the field of wood manufacturing. The method comprises the following steps: removing lignin of the wood sample by using alkali liquor, and then soaking the wood sample into an ethanol solution of a spirooxazine photochromic compound; after blending epoxy resin crystal glue dripping hard glue, injecting the mixed glue into a polytetrafluoroethylene mold, placing plant leaves with natural super-hydrophobicity on the surface layer of the glue solution, standing for 12-24 h at constant temperature in vacuum, and taking down the leaves to obtain the polytetrafluoroethylene mold with a reverse super-hydrophobicity structure; and (3) after the epoxy resin crystal glue dripping soft glue is blended, injecting the mixture into a mold, placing a wood sample on the surface of the glue solution, removing air bubbles in the glue solution and ethanol molecules in the wood sample, standing the wood sample at a constant temperature for 12-24 hours, and peeling the wood sample from the mold to obtain the flexible hydrophobic reversible photochromic wood. The raw materials used in the invention are green and environment-friendly, the method is simple, the reaction conditions are mild, and various shapes can be customized according to the use requirements.

Description

Preparation method of flexible hydrophobic reversible photochromic wood and wood prepared by same

Technical Field

The invention relates to a preparation method of flexible hydrophobic reversible photochromic wood and the prepared wood, belonging to the field of wood manufacturing.

Background

To reduce the dependence on artificial polymers, wood has received attention as a naturally renewable biomass composite. In the field of research on transparent wood, various methods for delignification of wood have been developed, such as a sodium hypochlorite method, a sodium chlorite method, and an alkali method, in which wood loses natural color due to the loss of a large number of chromophoric groups and chromaphoric groups present in lignin, and then delignified wood is glued into transparent wood by using a transparent polymer having a refractive index matched with the cell wall of wood, such as Polydimethylsiloxane (PDMS), polymethyl methacrylate (PMMA), epoxy resin, polyvinyl pyrrolidone (PVP), n-butyl methacrylate, polystyrene, dibutyl phthalate, isobutyl methacrylate, diallyl phthalate, and polyvinyl carbazole. This gives wood great possibilities for further development in terms of optical properties, mechanical properties and functionalization.

The spirooxazine compound is a typical organic photochromic material, can rapidly change color under the irradiation of sunlight or ultraviolet light, has strong fatigue resistance and has great practical application prospect. However, first, the spirooxazine compound is easily lost as a powder in practical use, and even when it is mixed into a paint, the powder is often lost by friction. Secondly, the polymer previously applied to the preparation of the transparent wood has the defects of difficult preparation process, unsatisfactory final performance, short service life, limited practical application and the like due to the defects of low transparency, easy generation of bubbles in the preparation process, yellowing in the use process, low toughness and the like of most of the polymers after curing. Thirdly, many plant leaves in nature such as lotus leaves and the like are natural super-hydrophobic templates, and the transfer printing of the super-microstructure to the surface of the material through the soft printing technology is a relatively mature research method for forming a super-hydrophobic interface. However, this method generally requires additional transfer material as a substrate, and such material is not necessarily compatible with the raw materials, thereby affecting its mechanical strength and aesthetic appearance.

Disclosure of Invention

In order to solve the technical problems, the invention provides a preparation method of flexible hydrophobic reversible photochromic wood and the wood prepared by the preparation method.

The inventor finds that delignification can effectively reduce light absorption in wood and light refraction in cell walls, increase porosity and facilitate impregnation and penetration of the spirooxazine compound. Most of the spirooxazine compounds are white powder, become transparent after being dissolved in an organic solvent, can quickly change color after being irradiated by sunlight or ultraviolet light, can quickly fade after being transferred to a dark environment, and can be hopefully combined with transparent wood to prepare the novel photochromic composite material. The epoxy resin crystal glue drops are relatively mature products developed in the market, have the characteristics of high transparency, self-defoaming, yellowing resistance and the like, can freely select hard glue or soft glue according to the requirements of customers, can overcome some defects in the manufacturing process, and endow the products with the advantage of flexibility. In addition, the epoxy resin crystal glue dripping (hard glue) can be well combined with a polytetrafluoroethylene mold, the properties are stable, the epoxy resin crystal glue dripping (hard glue) can be recycled, meanwhile, the raw material cost and the manufacturing process cost of a transfer printing substrate can be saved, and the transparent wood is endowed with the super-hydrophobic self-cleaning characteristic. With the improvement of living standard, people have to put higher requirements on the transparent wood, and the preparation method realizes the flexibility, the intellectualization and the function integration of the transparent wood. Meanwhile, the raw materials and the manufacturing process selected by the method meet the requirements of saving resources and protecting the environment.

The technical scheme for solving the technical problems is as follows: a preparation method of flexible hydrophobic reversible photochromic wood comprises the following steps:

1) immersing a wood sample into alkali liquor, reacting for 3-8 h at 60-90 ℃, then washing the wood sample, transferring the washed wood sample into a hydrogen peroxide aqueous solution with the concentration of 2-5 mol/L for bleaching for 3-5 h, and finally washing the wood sample;

2) immersing the cleaned wood sample of 1) into an ethanol solution containing 0.01-1 wt% of spirooxazine photochromic compound, and reacting for 1-6 h at constant temperature of 30-55 ℃ in vacuum to obtain a treated wood sample;

3) and (3) mixing the solution A and the solution B of the epoxy resin crystal glue dripping hard glue according to the weight ratio of 3: 1, injecting the mixture into a polytetrafluoroethylene mold after mixing and blending, only covering the bottom surface of the polytetrafluoroethylene mold, placing plant leaves with natural super-hydrophobic property on the surface layer of the glue solution after the glue solution is aged for 10min, standing for 12-24 h under the constant temperature condition of vacuum 30-55 ℃, and then taking down the leaves to obtain the polytetrafluoroethylene mold with the anti-super-hydrophobic structure;

4) liquid A and liquid B of the epoxy resin crystal glue dripping soft glue are mixed according to the proportion of 3: 1, filling the polytetrafluoroethylene mold prepared in the step 3) with the mixture, and placing the wood sample treated in the step 2) on the surface of the glue solution, wherein the wood sample floats on the surface of the glue solution;

5) in order to prevent the glue solution from curing, air bubbles in the glue solution and ethanol molecules in the wood sample are removed within 30min after the glue solution is prepared by the solution A and the solution B of the epoxy resin crystal glue dripping soft glue, and the glue solution is gradually filled into tracheids of the wood sample under the action of gravity and capillary action;

6) and (3) placing the polytetrafluoroethylene mold with the wood sample treated in the step 5) at a constant temperature of 30-55 ℃ for standing for 12-24 h, and peeling off the wood sample from the polytetrafluoroethylene mold to obtain the flexible hydrophobic reversible photochromic wood.

The preparation method of the flexible hydrophobic reversible photochromic wood has the beneficial effects that:

firstly, removing lignin in natural wood by an alkaline method to eliminate the influence of the lignin on the final optical performance of a wood sample, and simultaneously being beneficial to injection of a reagent for modification;

secondly, injecting the spirooxazine photochromic compound dissolved in ethanol into the delignified wood by adopting a vacuum constant-temperature impregnation method;

thirdly, constructing an anti-superhydrophobic structure at the bottom of the polytetrafluoroethylene mold by adopting a soft printing method;

finally, the prepared epoxy resin crystal glue dripping soft glue and a wood sample are sequentially placed into a mold, and after the glue solution is cured at room temperature, the flexible hydrophobic reversible photochromic wood is prepared.

The raw materials used in the invention are green and environment-friendly, the preparation method is simple, the cost is low, the reaction conditions are mild, and the hydrophobic reversible photochromic wood with various flexible shapes can be customized according to the use requirements. The prepared flexible hydrophobic reversible photochromic wood can be applied to the fields of photosensitive switches, intelligent dimming glass, light energy conversion and storage, anti-counterfeiting and the like, and meanwhile, the flexible hydrophobic reversible photochromic wood has the characteristics of flexibility and wearable property and super-hydrophobic self-cleaning performance.

On the basis of the technical scheme, the invention can be further improved as follows.

Further, in 1), the wood sample is any one or more of balsa wood, poplar, birch, cedar and basswood. The wood samples are the preferable samples of the invention, and reasonable tree species can be selected according to the advantages of local natural wood resources or artificial forest resources.

Further, in 1), the alkali solution means an aqueous solution containing 2 to 5mol/L of sodium hydroxide and 0.1 to 1mol/L of anhydrous sodium sulfite. The sodium hydroxide and the anhydrous sodium sulfite are cheap and easy to obtain, and the cost of raw materials is reduced.

If the wood sample is immersed in the alkali liquor, the color of the alkali liquor is changed from colorless to yellow brown in the reaction process, and the alkali liquor is replaced until the alkali liquor is not discolored. The alkali liquor is replaced in time, so that the effectiveness of the delignification agent and the thoroughness of delignification treatment can be maintained.

Further, in 1), the washing means washing with distilled water.

Further, in 2), the spirooxazine photochromic compound is any one of 1, 3, 3-trimethylindolylen straightforward words oxazine and derivatives thereof. The spirooxazine photochromic material selected by the invention has the advantages of fast color change (short photoresponse time), good thermal stability and fatigue resistance, and can obtain different absorption wavelengths by changing the substituent of the compound, thereby having a wide color selection range (yellow, orange, red, purple, blue and the like).

Further, in 3), the plant leaves with natural super-hydrophobic property are any one or more of lotus leaves, taro leaves and rice leaves. The leaves are natural super-hydrophobic templates and rich and diverse resources.

The invention also provides flexible hydrophobic reversible photochromic wood prepared by the method.

The invention also provides a product with photochromic performance and/or flexibility and/or hydrophobicity, and the material of the product comprises the flexible hydrophobic reversible photochromic wood.

Further, the products having photochromic properties and/or flexibility and/or hydrophobicity include photochromic toys, photochromic furniture, photosensitive switches, smart light-adjusting glass, optical information storage elements, decorative and protective packaging materials, building decoration products and anti-counterfeiting products. Wherein, the photochromic toy comprises a jigsaw puzzle, a kite with a photochromic surface and the like; the photochromic furniture comprises a table, a chair, a cabinet and a bed; the anti-counterfeiting products comprise military camouflage products, namely military camouflage products which are used for instruments, instruments and wearable equipment which need to change color under illumination and are matched with the surrounding environment so as to achieve the purpose of being shielded, goggles for preventing blindness caused by laser weapons and the like; the anti-counterfeiting product also comprises substitutes of paper, high polymer, fabric, ceramic and the like which need anti-counterfeiting treatment; the decorative and protective packaging materials include building curtain walls, adhesive films, and the like that can reduce light pollution.

Drawings

FIG. 1 is an electron micrograph of delignified wood obtained in example 1 at 10000 times magnification;

FIG. 2 is an electron micrograph of the flexible hydrophobic reversible photochromic wood prepared in example 1;

FIG. 3 is an electron micrograph of the portion of FIG. 2 at 2000 times magnification;

FIG. 4 is a hydrophobicity display chart of the flexible hydrophobic reversible photochromic wood prepared in example 1;

FIG. 5a is a graph showing photochromic behavior of the flexible hydrophobic reversible photochromic wood prepared in example 1 under dark light;

FIG. 5b is a graph showing photochromic behavior of the flexible hydrophobic reversible photochromic wood prepared in example 1 under 210W xenon illumination;

FIG. 5c is a chart of photochromic conditions of the flexible hydrophobic reversible photochromic wood prepared in example 1 under the irradiation of 280W xenon lamp;

FIG. 6 is a photograph for testing the bendability and elasticity of the transparent wood manufactured in comparative example 1;

FIG. 7 is a photograph for testing the photochromic of the transparent wood prepared in comparative example 1;

fig. 8 is a photograph for testing the hydrophobicity of the transparent wood manufactured in comparative example 1;

FIG. 9a is a graph showing the application of a comparative sample as a light-transmitting glass for a small house under irradiation with a 210W xenon lamp;

FIG. 9b is a graph showing the application of the flexible hydrophobic reversible photochromic wood prepared in example 1 as smart switchable glass for a small house under the irradiation of a 210W xenon lamp;

fig. 9c is a graph showing the application of the flexible hydrophobic reversible photochromic wood prepared in example 1 as smart glass for small houses under the irradiation of a 280W xenon lamp.

Detailed Description

The principles and features of this invention are described below in conjunction with the following drawings, which are set forth by way of illustration only and are not intended to limit the scope of the invention.

The epoxy crystal drip glue hardcoat used in the examples described below was purchased from the Venus Denney flagship store under the trade designation epoxy crystal drip glue (hardcoat) model 806.

The epoxy resin crystal glue dripping soft gum is purchased from Fuxing Denny flagship store, is called epoxy resin crystal glue dripping (soft gum) by trade name, and has the model number of 808.

PDMS (polydimethylsiloxane) and curing agent used in the comparative examples described below were commercially available as commercial packages from Shanghai Deg commercial Co., Ltd., model SYLGARD 184.

Example 1

A balsawood sample with the length of 50mm ×, the width of 50mm × and the height of 2mm is immersed into an aqueous solution containing 2.5mol/L sodium hydroxide and 0.4mol/L anhydrous sodium sulfite to react for 8 hours at the temperature of 80 ℃, then the balsawood sample is washed by distilled water and then transferred into an aqueous hydrogen peroxide solution with the concentration of 2.5mol/L to be bleached for 3 hours, and the balsawood sample is washed by distilled water again, as can be seen from figure 1, after the treatment of the steps, the cell walls (the place where the pores of three cell tubes are attached together is the cell wall) of the delignified wood are cracked, and the pores are increased.

Immersing the treated balsawood sample into an ethanol solution containing 0.05 wt% of 1, 3, 3-trimethylindolylen straightforward words oxazine, and reacting for 4 hours at constant temperature of 45 ℃ in vacuum to obtain the treated balsawood sample;

mixing and blending the solution A and the solution B of the epoxy resin crystal glue dripping hard glue according to the mass ratio of 3: 1, injecting the mixture into a polytetrafluoroethylene mold, only covering the bottom surface of the polytetrafluoroethylene mold, wherein the mold is in a cuboid structure with a rectangular groove, the size of the rectangular groove is 51mm long, × mm wide, 51mm wide, × mm high and 4mm high, after the glue solution is aged for 10min, spreading lotus leaves on the surface layer of the glue solution, standing for 12h under the conditions of vacuum and constant temperature of 45 ℃, and then taking down the lotus leaves to prepare the polytetrafluoroethylene mold with the anti-superhydrophobic structure;

liquid A and liquid B of the epoxy resin crystal glue dripping soft glue are mixed according to the proportion of 3: 1, filling the prepared polytetrafluoroethylene mold, and floating the treated balsawood sample on the surface of glue solution;

removing air bubbles in the glue solution and ethanol molecules in the balsawood sample by using a vacuum pump, and gradually filling the glue solution into tracheids of the balsawood sample under the action of gravity and capillary action within 30min of the prepared glue solution to prevent the glue solution from being solidified;

and standing the treated polytetrafluoroethylene mold for 12 hours at a constant temperature of 45 ℃, and stripping the balsawood sample from the polytetrafluoroethylene mold to obtain the flexible hydrophobic reversible photochromic wood. As can be seen from the figures 2-3, a plurality of protruding super-hydrophobic structures simulating lotus leaves are constructed on the surface of the epoxy resin crystal glue dripping soft glue. As can be seen from fig. 4, the flexible hydrophobic type reversible photochromic wood prepared in example 1 was tested for hydrophobicity, and when the volume of the water drop was 4 μ L, the contact angle was 154 °.

FIGS. 5 a-5 c are graphs showing photochromic behavior of the flexible hydrophobic reversible photochromic wood prepared in example 1 under dark light, 210W xenon lamp irradiation and 280W xenon lamp irradiation. It can be seen from the above fig. 5 a-5 c that the stronger the incident ray, the deeper the blue color, the darkest the blue color of fig. 5c, followed by fig. 5 b. This shows that the stronger the incident light, more spirooxazine molecules change the structure to become blue, and the incident light is absorbed, achieving the effect of adjusting the light intensity.

Comparative example 1

A sample of a balsawood 50mm in length ×, 50mm in width × and 2mm in height was immersed in an aqueous solution containing 2.5mol/L sodium hydroxide and 0.4mol/L anhydrous sodium sulfite, reacted at 80 ℃ for 8 hours, washed with distilled water, transferred to an aqueous solution of hydrogen peroxide at a concentration of 2.5mol/L to be bleached for 3 hours, and washed clean again with distilled water.

Mixing and blending PDMS (polydimethylsiloxane) and a curing agent according to a mass ratio of 10: 1, injecting the mixture into a polytetrafluoroethylene mold, wherein the mold is in a cuboid structure with a rectangular groove, the size of the rectangular groove is 51mm long, × mm wide, × mm wide and 4mm high, and then enabling a balsawood sample to float on the surface of glue solution.

Removing air bubbles in the glue solution and ethanol molecules in the wood sample by using a vacuum pump, gradually filling the glue solution into tracheids of the wood sample under the action of gravity and capillary action, and preventing the glue solution from being solidified within 30min after the glue solution is prepared.

And standing the whole processed mould for 12 hours at the constant temperature of 45 ℃, and peeling off the mould to obtain the transparent wood.

As shown in fig. 6, the transparent wood is a transparent film containing delignified wood, has no flexibility and elasticity, and is easy to scratch human bodies after being crushed. As shown in fig. 7, the transparent wood can guide light, but does not have the ability of photochromism to adjust the light intensity. As shown in fig. 8, the contact angle between the transparent wood and water is 95 °, which is easy to stain and wet, and the definition is reduced accordingly.

Experiment for determining Effect

A simple log cabin is built, the flexible hydrophobic reversible photochromic wood in the embodiment 1 is directly used as intelligent dimming glass and is installed on the ceiling of the log cabin, and the change of the internal light intensity is measured under the irradiation of vertical xenon lamp light. The results are shown in FIGS. 9b and 9 c.

The comparative sample was a sample containing no delignified wood and was prepared in the same manner as in example 1, except that no wood was added and the sample was directly cured with a soft gel to form a transparent sheet. The glass is used as light-transmitting glass and is arranged on the ceiling of a log cabin, and the light intensity change in the log cabin is measured under the irradiation of vertical xenon lamp light. The results are shown in FIG. 9 a.

As shown in FIG. 9a, under the irradiation of a 210W xenon lamp, the light beam directly reaches the bottom surface of the small house, so that the light intensity of the area 1 is 183, and the light intensity of the area 2 is 145, namely, a dead angle exists in the area 2, which is not beneficial to the activity of human beings.

As shown in fig. 9b, the flexible hydrophobic reversible photochromic wood of example 1 is used as smart light-adjusting glass, under the irradiation of a 210W xenon lamp, the smart light-adjusting glass turns blue, and the light beam diverges along the wood guide tube, so that the light intensity of the area 1 is 156, the light intensity of the area 2 is 157, the whole light of the small room is bright, and the movement of human is facilitated.

As shown in fig. 9c, the flexible hydrophobic reversible photochromic wood of example 1 was used as smart glass, the power of the xenon lamp was increased to 280W, and the color of the smart glass was changed to dark blue, so that the light intensity of area 1 was 157 and the light intensity of area 2 was 158. Compared to fig. 9b, the overall brightness of the small room does not change much. Therefore, the flexible hydrophobic reversible photochromic wood has the functions of guiding light and adjusting light intensity as intelligent light adjusting glass.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims

1. A preparation method of flexible hydrophobic reversible photochromic wood is characterized by comprising the following steps:

2. The method of claim 1, wherein in 1), the wood sample is any one or more of balsa wood, poplar, birch, fir and basswood;

the alkali liquor is an aqueous solution containing 2-5 mol/L sodium hydroxide and 0.1-1 mol/L anhydrous sodium sulfite;

the cleaning refers to cleaning with distilled water.

3. The method for preparing flexible hydrophobic reversible photochromic wood as claimed in claim 2, wherein if the wood sample is immersed in the alkali solution, the color of the alkali solution changes from colorless to yellowish brown during the reaction, and the alkali solution should be changed until the alkali solution does not change color.

4. The method for preparing flexible hydrophobic reversible photochromic wood according to claim 1, wherein in 2), the spirooxazine photochromic compound is any one of 1, 3, 3-trimethylindolen straightforward words oxazine and its derivatives.

5. The method for preparing a flexible hydrophobic reversible photochromic wood as claimed in claim 1, wherein in 3), the plant leaves with natural super-hydrophobic property are any one or more of lotus leaves, taro leaves and rice leaves.

6. A flexible hydrophobic reversible photochromic wood prepared according to the process of any one of claims 1 to 5.

7. A product having photochromic properties and/or flexibility and/or hydrophobicity, characterized in that its material comprises the flexible hydrophobic reversible photochromic wood according to claim 6.

8. The photochromic and/or flexible and/or hydrophobic product of claim 7 wherein the photochromic and/or flexible and/or hydrophobic product comprises photochromic toys, photochromic furniture, light-sensitive switches, smart privacy glasses, optical information storage elements, decorative and protective packaging materials, architectural finishing products and anti-counterfeiting products.