阅读说明：本技术 一种仿生木基湿度指示计及其制备方法 (Bionic wood-based humidity indicator and preparation method thereof ) 是由 詹天翼 刘治廷 吕建雄 彭辉 陈凯文 于 2021-07-07 设计创作，主要内容包括：本发明公开了一种仿生木基湿度指示计,包括主动层和被动层,所述主动层和被动层之间设有胶黏剂,所述主动层和被动层均为木质层板,所述主动层沿纵向变形大于被动层。本发明公开了一种仿生木基湿度指示计的制备方法,包括：根据实际使用条件的湿度范围,确定仿生木基湿度指示计的曲率变化范围；根据曲率变化范围,确定指示计中主动层、被动层的初始含水率和厚度比例；分别制备对应的主动层、被动层；分别对主动层、被动层进行调湿,使其达到初始含水率；主动层和被动层施胶并热压,制备得到仿生木基湿度指示计。本发明制备的仿生木基湿度指示剂的原料仅为木材和胶黏剂,成本低,工艺步骤简单,生产效率高,指示方法灵敏、高效、简单,可反复使用。(The invention discloses a bionic wood-based humidity indicator which comprises an active layer and a passive layer, wherein an adhesive is arranged between the active layer and the passive layer, the active layer and the passive layer are both wood laminates, and the deformation of the active layer along the longitudinal direction is larger than that of the passive layer. The invention discloses a preparation method of a bionic wood-based humidity indicator, which comprises the following steps: determining the curvature change range of the bionic wood-based humidity indicator according to the humidity range of the actual use condition; determining the initial water content and the thickness proportion of an active layer and a passive layer in the indicator according to the curvature change range; respectively preparing an active layer and a passive layer; humidifying the active layer and the passive layer respectively to enable the active layer and the passive layer to reach the initial water content; and gluing the active layer and the passive layer, and carrying out hot pressing to prepare the bionic wood-based humidity indicator. The bionic wood-based humidity indicator prepared by the invention only adopts wood and adhesive as raw materials, has low cost, simple process steps and high production efficiency, and the indicating method is sensitive, efficient and simple and can be used repeatedly.)

1. The bionic wood-based humidity indicator is characterized by comprising an active layer and a passive layer, wherein an adhesive is arranged between the active layer and the passive layer, the active layer and the passive layer are both wood laminates, and the active layer deforms longitudinally to be larger than the passive layer.

2. The method for preparing the bionic wood-based humidity indicator according to claim 1, which is characterized by comprising the following steps:

determining the curvature change range of the bionic wood-based humidity indicator according to the humidity range of the actual use condition;

determining the initial water content and the thickness proportion of an active layer and a passive layer in the indicator according to the curvature change range;

respectively preparing an active layer and a passive layer;

humidifying the active layer and the passive layer respectively to enable the active layer and the passive layer to reach the initial water content;

and gluing the active layer and the passive layer, and carrying out hot pressing to prepare the bionic wood-based humidity indicator.

3. The preparation method of the bionic wood-based humidity indicator according to claim 2, wherein the humidity range of actual use conditions is 5-99% relative humidity.

4. The preparation method of the bionic wood-based humidity indicator according to claim 2, wherein the curvature variation range of the bionic wood-based humidity indicator is-15-10 μm^-1。

5. The method of claim 2, wherein the active layer and the passive layer have an initial water content of 0%, 12% or 30%.

6. The method for preparing a bionic wood-based humidity indicator according to claim 5, wherein the humidity conditioning conditions of the active layer and the passive layer are 0%, 69% or 100%.

7. The method for preparing a bionic wood-based humidity indicator according to claim 2, wherein the thicknesses of the active layer and the passive layer are 20-200 μm, and the ratio of the thicknesses of the active layer and the passive layer is 0.1-10.

8. The method as claimed in claim 2, wherein the active layer has an axial stiffness of 10000MPa, and the passive layer has a radial stiffness of 800 MPa.

9. The preparation method of the bionic wood-based humidity indicator according to claim 2, wherein the adhesive is phenolic resin adhesive, and the adhesive application amount is 150-200 g/m²。

10. The preparation method of the bionic wood-based humidity indicator according to claim 2, wherein the hot pressing temperature is 140-160 ℃, the hot pressing time is 1-5 min, and the hot pressing pressure is 0.1-0.3 MPa.

Technical Field

The invention relates to the technical field of wood bionics, in particular to a bionic wood-based humidity indicator and a preparation method thereof.

Background

In the long evolution process of nature, the tissue structure of plants evolves to adapt to climate change. The leaves are stretched in rainy days to absorb water and closed in dry days to reduce loss; the opening degree of the pine nut shell scales changes according to the change of humidity; the wheat and awns are drilled into soil gaps along with the periodic change of humidity in the day and night alternating process; when the bean pods are dehydrated and contracted, the two bean pods are reversely bent to form a spiral shape, so that ejection of the seeds is realized. These behaviors that rely on humidity to actively change shape are high-level survival strategies for plants.

Wood is a capillary limited expansion colloidal material that is hygroscopic because the chemical components of the cell wall contain polar groups. When the air humidity is low, the wood is desorbed, and the internal moisture is diffused to the air; when the air humidity is high, the wood is subject to sorption, absorbing moisture from the air. During sorption or desorption, wood dimensions change, i.e. drying shrinkage and swelling. As an anisotropic material, the wood has different dry shrinkage and wet expansion in different directions, and the dry shrinkage and wet expansion amount in the transverse direction (radial direction and chord direction) is far larger than that in the longitudinal direction. The dry shrinkage and wet expansion may cause defects of cracking, warping and the like of the wood, so that the control of the dry shrinkage and wet expansion of the wood and the improvement of the dimensional stability of the wood are always important fields of wood modification.

Conventional wetness indicators include wet and dry bulb thermometers, hair hygrometers, lithium chloride hygrometers, and the like. The dry-wet bulb thermometer consists of two identical thermometers, one of which is a dry bulb thermometer and the other is a wet bulb thermometer. The temperature indication of the wet bulb thermometer is lower than that of the dry bulb thermometer by utilizing moisture evaporation, so that the relative humidity of air is obtained according to the difference of the wet bulb thermometer and the dry bulb thermometer, but the humidity indicator has low indicating efficiency, is insensitive and is easily influenced by wind speed, so that the indicating accuracy is influenced; the hair hygrometer measures the air humidity by using the change of the length or the volume of the hair after moisture absorption, but has the defects of lagging induction change, easy dust accumulation and unsuitability for long-term repeated use; lithium chloride or aluminum oxide is used as a humidity meter, and humidity is measured according to capacitance and resistance changes after the metal film absorbs water, but the cost is high.

Disclosure of Invention

The technical problem to be solved by the invention is to overcome the defects of the prior art and provide the bionic wood-based humidity indicator and the preparation method thereof, the raw materials of the prepared bionic wood-based humidity indicator are only wood and adhesive, the cost is low, the process steps are simple, the production efficiency is high, the indication method is sensitive, efficient and simple, the indicator can be repeatedly used, and multiple indications can be performed in the humidity range.

In order to solve the technical problems, the invention provides a bionic wood-based humidity indicator which comprises an active layer and a passive layer, wherein an adhesive is arranged between the active layer and the passive layer, the active layer and the passive layer are both made of wood laminates, and the longitudinal deformation of the active layer is larger than that of the passive layer.

In the double-layer structure, a certain difference exists in the longitudinal dimension change of the control active layer and the control passive layer. However, the active layer and the passive layer are bonded into a whole by the adhesive, so that the indicator bends to coordinate the size change difference of the active layer and the passive layer. When the humidity is increased, the indicator bends towards one side of the passive layer; when the humidity is reduced, the bend is restored toward the active layer side.

The invention also provides a preparation method of the bionic wood-based humidity indicator, which comprises the following steps:

determining the curvature change range of the bionic wood-based humidity indicator according to the humidity range of the actual use condition;

determining the initial water content and the thickness proportion of an active layer and a passive layer in the indicator according to the curvature change range;

respectively preparing an active layer and a passive layer;

humidifying the active layer and the passive layer respectively to enable the active layer and the passive layer to reach the initial water content;

and gluing the active layer and the passive layer, and carrying out hot pressing to prepare the bionic wood-based humidity indicator.

Preferably, the humidity range of the actual using condition is 5-99% relative humidity.

Preferably, the curve of the bionic wood-based humidity indicatorThe rate variation range is-15 to 10 μm^-1。

Preferably, the initial water content of the active layer and the passive layer is 0%, 12% or 30%.

Preferably, the humidity conditioning conditions of the active layer and the passive layer are 0%, 69% or 100%.

Preferably, the thickness of the active layer and the passive layer is 20-200 μm, and the ratio of the thickness of the active layer to the thickness of the passive layer is 0.1-10.

Preferably, the length direction of the active layer is the axial direction of the fir wood, the rigidity of the active layer is 10000MPa, the length direction of the passive layer is the radial direction of the fir wood, and the rigidity of the passive layer is 800 MPa.

Preferably, the adhesive is phenolic resin adhesive, and the adhesive application amount is 150-200 g/m²。

Preferably, the hot pressing temperature is 140-160 ℃, the hot pressing time is 1-5 min, and the hot pressing pressure is 0.1-0.3 MPa.

The invention achieves the following beneficial effects:

(1) compared with other humidity indicators, the bionic wood-based humidity indicator prepared by the invention only adopts wood and adhesive as raw materials, and has the advantages of low cost, simple process steps and high production efficiency;

(2) the bionic wood-based humidity indicator prepared by the invention has sensitive, efficient and simple indicating method;

(3) the wood-based humidity indicator can be used repeatedly and can indicate for multiple times in a humidity range;

(4) the bionic wood-based humidity indicator prepared by the invention has the advantages of adjustable breadth size, beautiful finished product and various forms.

Drawings

FIG. 1 is a schematic representation of an exemplary indication of a wood-based wetness indicator provided in accordance with an embodiment of the present invention;

FIG. 2 is a graph showing the relationship between the curvature of a wood-based humidity indicator and the ambient humidity in various embodiments;

FIG. 3 is a graph of curvature of an absolute dry wood-based wetness indicator versus the ratio of active and passive layer thicknesses;

FIG. 4 is a graph of curvature of an oven-dried wood-based moisture indicator as a function of moisture content of the active and passive layers.

Detailed Description

The present invention will be further described with reference to the following examples. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.

As shown in fig. 1, a bionic wood-based humidity indicator comprises an active layer 1 and a passive layer 2, an adhesive 3 is arranged between the active layer 1 and the passive layer 2, the active layer 1 and the passive layer 2 are both wood laminates, and the active layer 1 deforms more than the passive layer 2 along the longitudinal direction. In the double-layer structure, there is a difference in controlling the longitudinal dimensional change of the active layer 1 and the passive layer 2. However, since the active layer 1 and the passive layer 2 are integrally bonded by the adhesive 3, the indication is that the bending occurs in accordance with the difference in the dimensional changes of the active layer 1 and the passive layer 2. When the humidity increases, the indicator bends toward the passive layer 2 side; when the humidity is reduced, the bending is restored toward the active layer 1 side.

Example 1

A bionic wood-based humidity indicator is prepared by the following steps:

step one, determining the actual humidity change range as follows: 50% -90%.

Step two, determining the curvature change range of the wood-based humidity indicator to be-3 μm according to the humidity change range of the step one^-1~3μm^-1。

Step three, determining the initial water content of the active layer to be 12% and the initial water content of the passive layer to be 0% according to the curvature variation range of the step two;

and step four, determining the thickness of the active layer to be 100 μm and the thickness of the passive layer to be 50 μm according to the curvature variation range of the step two.

And step five, according to the initial water content in the step three, the humidity adjusting condition of the active layer is 100%, and the humidity adjusting condition of the passive layer is 0%.

And step six, gluing the active layer and the passive layer which are subjected to the step three to the step five, and assembling in parallel. The glue application amount is 150g/m²。

And step seven, hot pressing. The hot pressing temperature is 140 ℃, the hot pressing time is 5min, and the hot pressing pressure is 0.1 MPa. And after the hot pressing is finished, obtaining the bionic wood-based humidity indicator.

Example 2

A bionic wood-based humidity indicator is prepared by the following steps:

step one, determining the actual humidity change range as follows: 30% -75%.

Step two, determining the curvature change range of the wood-based humidity indicator to be-1 μm according to the humidity change range of the step one^-1~4μm^-1。

Step three, determining the initial water content of the active layer to be 30% and the initial water content of the passive layer to be 0% according to the curvature variation range of the step two;

and step four, determining the thickness of the active layer to be 150 μm and the thickness of the passive layer to be 100 μm according to the curvature variation range of the step two.

And step five, according to the initial water content in the step three, the humidity adjusting condition of the active layer is 100%, and the humidity adjusting condition of the passive layer is 0%.

And step six, gluing the active layer and the passive layer which are subjected to the step three to the step five, and assembling in parallel. The glue application amount is 200g/m²。

And step seven, hot pressing. The hot pressing temperature is 150 ℃, the hot pressing time is 3min, and the hot pressing pressure is 0.2 MPa. And after the hot pressing is finished, obtaining the bionic wood-based humidity indicator.

Example 3

A bionic wood-based humidity indicator is prepared by the following steps:

step one, determining the actual humidity change range as follows: 10% -90%.

Step two, determining the curvature change range of the wood-based humidity indicator to be-2 μm according to the humidity change range of the step one^-1~6μm^-1。

Step three, determining the initial water content of the active layer to be 30% and the initial water content of the passive layer to be 30% according to the curvature variation range of the step two;

and step four, determining the thickness of the active layer to be 100 μm and the thickness of the passive layer to be 100 μm according to the curvature variation range of the step two.

And step five, according to the initial water content in the step three, the humidity adjusting condition of the active layer is 100%, and the humidity adjusting condition of the passive layer is 100%.

And step six, gluing the active layer and the passive layer which are subjected to the step three to the step five, and assembling in parallel. The glue application amount is 170g/m²。

And step seven, hot pressing. The hot pressing temperature is 160 ℃, the hot pressing time is 4min, and the hot pressing pressure is 0.3 MPa. And after the hot pressing is finished, obtaining the bionic wood-based humidity indicator.

Example 4

A bionic wood-based humidity indicator is prepared by the following steps:

step one, determining the actual humidity change range as follows: 40% -60%.

Step two, determining the curvature change range of the wood-based humidity indicator to be-1 μm according to the humidity change range of the step one^-1~4μm^-1。

Step three, determining the initial water content of the active layer to be 30% and the initial water content of the passive layer to be 12% according to the curvature change range of the step two;

and step four, determining the thickness of the active layer to be 60 μm and the thickness of the passive layer to be 40 μm according to the curvature variation range of the step two.

And step five, according to the initial water content in the step three, the humidity adjusting condition of the active layer is 100%, and the humidity adjusting condition of the passive layer is 69%.

And step six, gluing the active layer and the passive layer which are subjected to the step three to the step six, and assembling in parallel. The glue application amount is 185g/m²。

And step seven, hot pressing. The hot pressing temperature is 150 ℃, the hot pressing time is 4min, and the hot pressing pressure is 0.2 MPa. And after the hot pressing is finished, obtaining the bionic wood-based humidity indicator.

Example 5

A bionic wood-based humidity indicator is prepared by the following steps:

step one, determining the actual humidity change range as follows: 35% -85%.

Step two, determining wood according to the humidity change range in the step oneThe range of curvature variation of the humidity indicator was-3 μm^-1~7μm^-1。

Step three, determining the initial water content of the active layer to be 12% and the initial water content of the passive layer to be 12% according to the curvature change range of the step two;

and step four, determining the thickness of the active layer to be 25 μm and the thickness of the passive layer to be 25 μm according to the curvature variation range of the step two.

And step five, according to the initial water content in the step three, the humidity adjusting condition of the active layer is 69%, and the humidity adjusting condition of the passive layer is 69%.

And step six, gluing the active layer and the passive layer which are subjected to the step three to the step five, and assembling in parallel. The glue application amount is 190g/m²。

And step seven, hot pressing. The hot pressing temperature is 145 ℃, the hot pressing time is 3min, and the hot pressing pressure is 0.2 MPa. And after the hot pressing is finished, obtaining the bionic wood-based humidity indicator.

Fig. 2 shows the change of curvature of the wood-based hygrometer of each embodiment during the change of ambient humidity. It can be seen from the figure that in either embodiment, the curvature is approximately linear or exponential with respect to ambient humidity. Namely, the curvature and the ambient humidity have a one-to-one correspondence relationship, but the numerical value of the curvature and the variation amplitude along with the relative humidity of each embodiment have differences. The value of the curvature is related to the total thickness of the wood-based wetness indicator and the ratio of the thicknesses of the active and passive layers. The magnitude of the change in curvature with relative humidity is related to the moisture content of the active/passive layers. Fig. 3 shows the curvature of the absolute dry wood-based gauge as a function of thickness ratio for different total thicknesses. As can be seen from the figure, the absolute value of the absolute dry curvature decreases with increasing thickness ratio and decreases with increasing total thickness. FIG. 4 is a graph showing the variation of the curvature variation range of the active/passive layer under different water content conditions. Therefore, according to the actual humidity change range, a better curvature change range, a corresponding thickness ratio and an initial water content can be determined.

The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.