CN115534039A - A preparation method of in-situ polymerized hydrogel flame-retardant wood - Google Patents

Abstract

The invention discloses a preparation method of in-situ polymerized hydrogel flame-retardant wood, which comprises the following steps: s1, immersing wood in alkali liquor for soaking and carrying out heat treatment; s2, soaking the wood subjected to heat treatment into hydrogel precursor liquid, and obtaining the hydrogel precursor liquidThe body comprises the following components: acrylamide, potassium persulfate, N, N-tetramethylethylenediamine, distilled water and magnesium chloride; and S3, performing heat preservation treatment on the wood infiltrated in the step S2 to ensure that acrylamide monomers in pores of the wood are fully polymerized at high temperature to obtain the in-situ polymerized hydrogel flame-retardant wood. The method comprises the steps of firstly carrying out surface modification on wood, constructing a porous cellulose hydrophilic network, then filling polyacrylamide hydrogel in situ in the cellulose network, wherein the polyacrylamide hydrogel is based on Mg ²⁺ With cellulose, mg ²⁺ The flame-retardant wood composite material with high interface stability is obtained by physical crosslinking with polyacrylamide, cellulose and polyacrylamide, and has the advantages of simple processing technology, low cost and obvious flame-retardant effect.

Description

A preparation method of in-situ polymerized hydrogel flame-retardant wood

technical field

The invention relates to the technical field of wood treatment, in particular to a preparation method of in-situ polymerized hydrogel flame-retardant wood.

Background technique

Wood materials have been widely used in the fields of architecture and interior decoration due to their natural texture, low thermal conductivity, high sound insulation performance, and high compression and earthquake resistance. However, wood materials are flammable materials (the limiting oxygen index is about 18% to 22%), and most indoor fires are related to wood. Therefore, improving the flame retardancy of wood materials is closely related to people's lives and property.

Commonly used flame retardants for wood include halogen-based, boron-based, nitrogen-phosphorus-based, and metal hydroxides. Conventional reagents improve the flame retardancy of wood (the limiting oxygen index is about 30% to 75%) and increase the carbonation rate of wood. However, most of the reagents have weak bonding with wood and are easily eroded by liquid water. Therefore, the development of wood composites with high flame retardancy and high weather resistance is the key.

Contents of the invention

The purpose of the present invention is to provide a preparation method of in-situ polymerized hydrogel flame-retardant wood, which solves the problem of weak interfacial bonding of flame retardants, poor resistance to open flame ignition and easy flame spread caused by the use of existing flame retardants in treating wood The problem.

The present invention realizes through following technical scheme:

A preparation method of in-situ polymerized hydrogel flame retardant wood, comprising the following steps:

S1, immersing the wood in lye for heat treatment;

S2, immerse the heat-treated wood into the hydrogel precursor liquid, the hydrogel precursor liquid includes the following components: acrylamide, potassium persulfate, N,N,N,N-tetramethylethylenediamine, distilled water and magnesium chloride;

S3, heat-insulating the wood soaked in step S2, so that the acrylamide monomer in the wood pores is fully polymerized at high temperature, and the in-situ polymerized hydrogel flame-retardant wood is obtained.

The potassium persulfate in the present invention is an oxidizing agent, the N,N,N,N-tetramethylethylenediamine is a crosslinking agent, and the magnesium chloride is a flame retardant.

In step S1 of the present invention, immersing the wood in lye can remove lignin, so as to obtain a millimeter-scale cellulose porous network on the surface of the wood, and then modify the surface of the wood by heat treatment to construct a porous cellulose hydrophilic network ; Step S2 is to fill (polymerize) polyacrylamide hydrogel in situ in the cellulose network by immersing the wood in the hydrogel precursor liquid, and then make Mg ²⁺ and cellulose, Mg through the heat preservation treatment of step S3 Physical crosslinking occurs between ²⁺ and polyacrylamide, cellulose and polyacrylamide to obtain flame-retardant wood composite materials with high interfacial stability. As we all know, magnesium chloride is a typical flame-retardant agent, which is easy to absorb moisture from humid air However, it turns into an aqueous solution (the critical relative humidity is 32.8% at 25° C.), resulting in the leakage of the flame retardant agent, which reduces the flame retardant performance of the wood composite material. The present invention solves the problem of weak interfacial binding force of the flame retardant caused by the use of magnesium chloride flame retardant reagents in treating wood through physical crosslinking, and solves the problem of weak interfacial binding force of flame retardants caused by the use of existing flame retardants in treating wood, Improves the weatherability of wood composites. More importantly, the wood composite material of the present invention combines multiple flame retardant mechanisms to transform it from a flammable material to a non-combustible material (the limiting oxygen index is about 96% to 100%). Various flame retardant mechanisms are as follows:

1) The polymer hydrogel of the present invention evaporates and absorbs a large amount of heat (the evaporation enthalpy of water at 30°C is about 2.4kJ/g), which reduces the possibility of the wood composite being ignited;

2) The polymer hydrogel expands in volume due to the rapid evaporation of liquid water, forming a protective coating on the wood surface;

3) The coating burns in a high-temperature environment to form a porous fire-resistant flame-retardant layer (composed of magnesium chloride and ash). This means that the wood composite material reported in the present invention cannot be ignited by an open flame, and the phenomenon of flame spread is difficult to occur.

Therefore, the polymer hydrogel of the present invention increases the weather resistance of the wood composite material, prevents magnesium chloride from absorbing moisture in a humid environment and leaks; the polymer hydrogel combines a triple flame-retardant mechanism, and the wood composite material is converted into a non-combustible material ; Solve the problem that the existing flame retardant agent is used to process wood to cause poor ignition performance of open flame and easy flame spread.

Further, in step S1, the lye is a mixed lye of sodium hydroxide and sodium sulfite.

Further, in step S1, the soaking time is 6-48 hours.

Further, in step S1, the temperature of heat treatment is 80-120°C.

Further, in step S2, the mass ratio of acrylamide, potassium persulfate, N,N,N,N-tetramethylethylenediamine, distilled water and magnesium chloride is: 100:0.4:1:500:50-150.

The content of magnesium chloride determines the flame retardancy and bonding strength. Therefore, it is necessary to reasonably control the mass proportion of magnesium chloride.

Further, in step S2, the soaking time is 6-24 hours.

Further, in step S3, the temperature of the heat preservation treatment is 50-70°C.

Further, in step S3, the time for heat preservation treatment is 6-48 hours.

Further, in step S3, an incubator is used for the heat preservation treatment.

Further, the wood includes balsa wood, fir wood, poplar wood or rubber wood.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

1. The present invention firstly modifies the surface of wood to construct a porous cellulose hydrophilic network, and then fills (polymerizes) polyacrylamide hydrogel in situ in the cellulose network, based on Mg ²⁺ and cellulose, Mg ²⁺ and The physical cross-linking between polyacrylamide, cellulose and polyacrylamide obtained flame-retardant wood composites with high interfacial stability.

2. The wood composite material prepared by the preparation method described in this invention has high flame-retardant properties, and the limiting oxygen index (LOI) is greater than 96%; it cannot be ignited by an open flame at 400-500 ° C; it is heated by an open flame for 300 seconds, and its ash rate is almost is zero, and the carbonization length does not exceed 1cm.

3. The invention has simple processing technology, low cost, remarkable flame retardant effect, and is easy to be popularized on a large scale.

Description of drawings

The drawings described here are used to provide a further understanding of the embodiments of the present invention, constitute a part of the application, and do not limit the embodiments of the present invention. In the attached picture:

Fig. 1 is a schematic diagram of the preparation process of the present invention;

Fig. 2 is the SEM photo of embodiment 1 of the present invention flame-retardant wood composite material;

Fig. 3 is the EDS-Mapping photo of embodiment 1 of the present invention flame-retardant wood composite material;

Fig. 4 is the open flame ignition experiment of natural balsa wood and flame-retardant wood composite material in Example 1 of the present invention;

Fig. 5 is the flame retardant mechanism schematic diagram of flame retardant wood composite material of the present invention;

Fig. 6 is the moisture absorption curve of the composite material of Example 2 of the present invention under 90% relative humidity environment;

Fig. 7 is the photograph after being ignited 300s by naked flame of the composite material of embodiment 2 of the present invention;

Fig. 8 is a photo of the large-scale wood composite material in Example 3 of the present invention.

detailed description

In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the examples and accompanying drawings. As a limitation of the present invention.

Example 1:

As shown in Figure 1, a kind of preparation method of in-situ polymerized hydrogel flame retardant wood, comprises the following steps:

S1. Surface modification of wooden materials: immerse balsa wood with a volume of 1cm*1cm*15cm in a mixture of 2.5M sodium hydroxide and 0.4M sodium sulfite, soak at 100°C for 12h, and name it DW;

S2. Configuration of hydrogel precursor solution: Soak the pretreated wood strips in 500ml distilled water, then add 100g acrylamide and 100g magnesium chloride hexahydrate, stir at room temperature for 6h, then add 0.4g potassium persulfate and 1.0 Add ml of N,N,N,N-tetramethylethylenediamine to the solution and stir for several minutes;

S3. Aging of flame-retardant wood composite materials: the wood was transferred to an incubator, the temperature was set at 60° C., and the holding time was 12 hours. The obtained flame-retardant wood was named DW/PAM.

Carry out material characterization and test to a kind of flame-retardant wood DW/PAM of embodiment 1:

1) Field emission scanning electron microscopy (FE-SEM) and EDS-mapping tests were carried out on virgin balsa wood (BW) and DW/PAM wood composites. As shown in Figure 2, the original balsa wood exhibited a closed-cell structure, while the dried DW/PAM samples exhibited dense features. This means that the polyacrylamide polymer hydrogel has been fully filled in the cellulose network. It can be seen from Figure 3 that the flame retardant magnesium chloride is evenly distributed in the wood.

2) The limiting oxygen index test was carried out on the samples of BW and DW/PAM. The limiting oxygen index of natural wood is only 20.4, which is a flammable material. For composite materials, its LOI value is as high as 96%, which is indeed a high flame-retardant material.

3) The open flame ignition experiment was carried out on the BW and DW/PAM samples. As shown in Figure 4, natural wood with a cross-sectional area of 1 ^cm2 is ignited within seconds. After being continuously heated for 300 seconds, a 6.3cm length of wood was reduced to ashes, and the remaining wood was almost completely carbonized. In contrast, DW/PAM samples cannot be ignited by an open flame at 450 °C. The composite wood retained its original shape (no ash) after being exposed to heat for 300 seconds. It can be seen from Figure 4b and c that the carbonization length of wood does not exceed 1cm.

4) Induction of flame retardant mechanism. As shown in Figure 5, from room temperature to 100°C, wood composite materials evaporate and lose water, absorbing a lot of heat. When the ambient temperature exceeds 100°C, the polymer hydrogel expands when heated, covers the wood surface, and forms a flame-retardant layer. When the temperature reaches 200-400°C, the composite wood tends to carbonize with the help of the flame-retardant layer. When the temperature is 400-500°C, the composite wood burns slowly, forming a new flame-retardant layer and a low thermal conductivity layer, so that the composite wood will not burn further.

Example 2:

The effect of different magnesium chloride qualities on the flame retardancy of the DW/PAM wood composite of the present invention was studied.

Put pretreated wood (1cm*1cm*15cm) of the same shape into precursor solutions containing different magnesium chloride masses (0g, 50g, 100g) for in-situ polymerization, and other processing procedures are the same as in Example 1. The flame retardant properties of the prepared composite woods are very different for DW/PAM-0gMgCl ₂ , DW/PAM-50gMgCl ₂ and DW/PAM-100gMgCl ₂ . As shown in Figure 6, when the thoroughly dried natural wood is placed at 25°C and 90% relative humidity, when the adsorption time exceeds 800 minutes, the adsorption amount of balsa wood is still lower than 8.2g water/100g wood. In comparison, the adsorption capacity of the DW/PAM- _0gMgCl2 sample exceeds 15.2g water/100g wood (according to the description added to the attached figure); the adsorption capacity of the DW/PAM- _50gMgCl2 sample is about 22.0g water/100g wood; The adsorption capacity of DW/PAM- _100gMgCl2 sample reached 28.6g water/100g wood. It can be seen from Figure 7 that as the mass of magnesium chloride increases, the flame retardant performance increases significantly.

Example 3:

The difference from Example 1 is that the size of the wood is adjusted to 1cm*6cm*5cm. Others are the same as in Example 1. The comparison before and after treatment is shown in Fig. 8, and the performance of the prepared fire-retardant wood is equivalent to that of Example 1.

Example 4:

The difference from Example 1 is that the wood is poplar, and the others are the same as in Example 1, and the performance of the prepared fire-retardant wood is equivalent to that of Example 1.

In summary, the present invention prepares a wood composite material with high flame retardancy by coupling mixed lye and in-situ polymerization technology; the wood composite material can be stable in the air for a long time, and the filled polymer hydrogel (transparent) does not Affects the texture of wood materials. The limiting oxygen index of wood composite materials is as high as 96%, and it is impossible to be ignited by an open flame. Therefore, the present invention has potential application prospects in the fields of architecture, interior decoration, sculpture, furniture and the like.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the scope of the present invention. Protection scope, within the spirit and principles of the present invention, any modification, equivalent replacement, improvement, etc., shall be included in the protection scope of the present invention.

Claims (10)

1. The preparation method of the in-situ polymerized hydrogel flame-retardant wood is characterized by comprising the following steps:

s1, immersing wood in alkali liquor for soaking and carrying out heat treatment;

s2, soaking the wood subjected to heat treatment into hydrogel precursor liquid, wherein the hydrogel precursor liquid comprises the following components: acrylamide, potassium persulfate, N, N-tetramethylethylenediamine, distilled water and magnesium chloride;

and S3, performing heat preservation treatment on the wood infiltrated in the step S2 to ensure that acrylamide monomers in pores of the wood are fully polymerized at high temperature to obtain the in-situ polymerized hydrogel flame-retardant wood.

2. The method for preparing an in-situ polymerized hydrogel flame-retardant wood as claimed in claim 1, wherein in step S1, the alkali solution is a mixed alkali solution of sodium hydroxide and sodium sulfite.

3. The method for preparing the in-situ polymerized hydrogel flame-retardant wood according to claim 1, wherein the soaking time in the step S1 is 6-48 h.

4. The method for preparing an in-situ polymerized hydrogel flame-retardant wood as claimed in claim 1, wherein the temperature of the heat treatment in step S1 is 80-120 ℃.

5. The method for preparing the in-situ polymerized hydrogel flame-retardant wood according to claim 1, wherein in the step S2, the mass ratio of the acrylamide to the potassium persulfate to the N, N, N, N-tetramethylethylenediamine to the distilled water to the magnesium chloride is as follows: 100.

6. The method for preparing the in-situ polymerized hydrogel flame-retardant wood according to claim 1, wherein the soaking time in the step S2 is 6-24 hours.

7. The method for preparing the in-situ polymerized hydrogel flame-retardant wood according to claim 1, wherein the temperature of the heat preservation treatment in the step S3 is 50-70 ℃.

8. The method for preparing the in-situ polymerized hydrogel flame-retardant wood according to claim 1, wherein the heat preservation time in step S3 is 6-48 h.

9. The method for preparing the in-situ polymerized hydrogel flame-retardant wood as claimed in claim 1, wherein in step S3, an incubator is adopted for the heat preservation treatment.

10. The method as claimed in any one of claims 1 to 9, wherein the wood comprises balsa wood, cedar wood, poplar wood or rubber wood.

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