CN114736348B - Microcrack-resistant coating and preparation method thereof - Google Patents

Abstract

The application discloses an anti-microcrack coating and a preparation method thereof, and relates to the field of coatings. The microcrack-resistant coating comprises a microcrack-resistant prepolymer, white carbon black, methyl silicone oil and a sulfur-containing silane coupling agent; the preparation method of the microcrack-resistant prepolymer comprises the steps of mixing hydroxyl-terminated polydimethylsiloxane, diisocyanate and an organotin catalyst to form a mixture A, dissolving hydroxyl disulfide in tetrahydrofuran, adding the mixture A, and reacting to obtain the microcrack-resistant prepolymer. According to the application, the self-repairing capability of the anti-microcrack coating is realized through the attraction of hydrogen bonds and the reconstruction of disulfide bonds, and the anti-microcrack prepolymer and the coating base material are connected together through chemical reaction, so that a firm three-dimensional network structure can be formed, the anti-microcrack coating is formed as a whole, and the generation of cracks is inhibited.

Description

Microcrack-resistant coating and preparation method thereof

Technical Field

The application relates to the field of coatings, in particular to an anti-microcrack coating and a preparation method thereof.

Background

To prevent the external insulation surface of the power transformation equipment from generating pollution flashover, an anti-pollution flashover coating is often coated. However, as the running time increases, the surface of the paint is aged, micro cracks are generated, the performance of the paint is affected, and the safe and stable running of a power grid is threatened.

In the aspect of preventing the microcracks on the surface of the paint, related researchers prepare self-repairing paint and self-repair the microcracks. At present, in the aspect of overcoming surface microcracks, the related technical means achieve the effect of repairing the cracks through metal coordination bonds, hydrogen bonds, hydrophilic-hydrophobic interactions, imine bonds/acylhydrazone bonds, borate bonds, disulfide bonds and the like. However, for the repair principle of self-repairing materials, most self-repairing coatings rely on a single force, such as a single metal coordination bond, a single hydrogen bond, and the like. On the other hand, most self-repairing coatings are prepared by adding self-repairing filler into a coating substrate, wherein the self-repairing filler and the coating substrate are simply and physically mixed, and the mechanical strength of a repairing structure is insufficient.

Disclosure of Invention

The application provides an anti-microcrack coating and a preparation method thereof, which are used for providing a coating with self-repairing function on microcracks and improving mechanical strength and wear resistance.

In order to solve the technical problems, one of the purposes of the application is to provide a preparation method of an anti-microcrack prepolymer, which comprises the following preparation steps:

(1) Heating hydroxyl-terminated polydimethylsiloxane under vacuum condition to remove water and gas, adding diisocyanate and an organotin catalyst, and stirring under the protection of oxygen-isolated atmosphere to obtain a mixture A;

(2) Dissolving the hydroxy disulfide in tetrahydrofuran at 65-80 ℃, adding the mixture into a container containing the mixture A, and reacting for 30-60 minutes under the protection of oxygen-isolated atmosphere to obtain the microcrack-resistant prepolymer.

The composition comprises the following components in parts by weight:

hydroxy-terminated polydimethylsiloxane: 30-50 parts;

a diisocyanate: 5-8 parts;

organotin catalyst: 0.1 to 0.5 part;

hydroxy disulfide: 5-10 parts;

tetrahydrofuran: 30-50 parts.

Preferably, in the step (1), the diisocyanate is one or more of toluene-2, 5-diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate and tetramethylxylylene diisocyanate.

Preferably, in the step (2), the hydroxydisulfide is bis (4-hydroxyphenyl) disulfide or 3,3' -dihydroxydiphenyl disulfide.

Preferably, in the step (1), the organotin catalyst is stannous octoate, dibutyltin dilaurate or dibutyltin diacetate.

Preferably, in the step (1), the temperature for heating and removing moisture and gas under the vacuum condition of the hydroxyl-terminated polydimethylsiloxane is 65-80 ℃; the stirring time is 1-2h.

Preferably, the viscosity of the hydroxyl-terminated polydimethylsiloxane is 2000-3000cst.

In order to solve the technical problems, the second object of the application is to provide an anti-microcrack coating, which comprises the following components in parts by weight:

microcrack resistant prepolymer: 40-80 parts;

white carbon black: 3-10 parts;

methyl silicone oil: 3-8 parts;

sulfur-containing silane coupling agent: 5-10 parts.

By adopting the scheme, the microcrack-resistant prepolymer of the application generates carbamate through the reaction of the-NCO of diisocyanate and the hydroxyl at the tail end of polydimethylsiloxane and the hydroxyl in hydroxyl disulfide, and meanwhile, the sulfur-containing silane coupling agent can be connected with the hydroxyl-terminated polydimethylsiloxane through chemical reaction, so that a firm three-dimensional network structure can be formed with a coating substrate, and the whole coating can be formed, thereby playing a role of self-inhibiting cracks; in addition, the sulfur-containing silane coupling agent can reconstruct disulfide bonds on the sulfur-containing silane coupling agent and the hydroxyl disulfide, and can carry out self-repairing in a cooperative manner, so that the self-repairing function is improved.

Preferably, the sulfur-containing silane coupling agent is bis (triethoxysilylpropyl) disulfide or bis [3- (triethoxysilylpropyl ] tetrasulfide.

In order to solve the technical problems, the application provides a preparation method of the microcrack resistant coating, which comprises the following steps: adding the microcrack-resistant prepolymer, white carbon black and methyl silicone oil into dispersing equipment for dispersing until the mixture is uniformly mixed to obtain a mixed material, adding a sulfur-containing silane coupling agent into the mixed material, uniformly mixing, and canning to obtain the microcrack-resistant coating.

Preferably, the dispersing time is 30 to 60 minutes.

Compared with the prior art, the embodiment of the application has the following beneficial effects:

1. the paint provided by the application has a self-repairing effect, can repair the micro-cracks, and has self-repairing capability mainly derived from the reconstruction function of dynamic chemical bonds in the paint, namely intermolecular hydrogen bonds and disulfide bonds. Hydroxyl groups on the hydroxyl-terminated polydimethylsiloxane and the hydroxyl disulfide form-COONH-, -COONH-with isocyanate bond on diisocyanate to form hydrogen bond with carbonyl oxygen atom on-COONH-in adjacent molecules, so that self-repairing function is realized. Disulfide bonds on the hydroxyl disulfide and the sulfur-containing silane coupling agent are reconstructed under the actions of temperature, light and the like, and disulfide bonds on the hydroxyl disulfide can be reconstructed with disulfide bonds on the hydroxyl disulfide or the sulfur-containing silane coupling agent to form new molecules, so that a self-repairing function is realized. When microcracks occur, the attractive force of the hydrogen bonds and the disulfide bond reconstruction render the microcrack resistant coating self-healing.

2. The hydroxyl-terminated polydimethylsiloxane, the hydroxyl disulfide, the diisocyanate and the sulfur-containing silane coupling agent are connected together through chemical reaction to form the whole anti-microcrack coating. Compared with partial self-repairing paint or other self-repairing fillers added into paint base materials, the anti-microcrack prepolymer and the paint base materials can form a firm three-dimensional network structure, and the generation of cracks is restrained.

Drawings

Fig. 1: preparing the reaction formula in the step (1) for the microcrack-resistant prepolymer in the preparation example I;

fig. 2: preparing the reaction formula in the step (2) for the microcrack-resistant prepolymer in the preparation example I;

fig. 3: an infrared spectrogram of the microcrack-resistant prepolymer in the preparation example I of the application;

fig. 4: a Raman spectrum diagram of an anti-microcrack prepolymer in the preparation example I of the application;

fig. 5: the repair result is observed by a 3D ultra-depth-of-field microscope for the microcrack-resistant coating in the first embodiment of the application (note: the upper graph is the surface after the sample is cut, and the lower graph is the surface after the sample is cut and healed).

Detailed Description

The following description of the embodiments of the present application will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

Preparation example one

An anti-microcrack prepolymer comprising the following preparation steps:

(1) 30g of hydroxy-terminated polydimethylsiloxane (viscosity 3000 cSt) was placed in a dry flask and heated at 80℃under vacuum for 2 hours to remove moisture and gas, and 5g of isophorone diisocyanate and 0.1g of stannous octoate were added to the flask and stirred under nitrogen for 1 hour to give a mixture A, the reaction formula of which is shown in FIG. 1;

(2) 5g of bis (4-hydroxyphenyl) disulfide was dissolved in 50g of tetrahydrofuran at 65℃and added to a flask containing mixture A, and reacted under nitrogen for 30 minutes to give an anti-microcrack prepolymer of the formula shown in FIG. 2.

As shown in the infrared spectrogram results in FIG. 3, the peak at 1708cm-1 is the stretching vibration of amide C=O, the peak at 1532cm-1 belongs to the amide II band, and the two peaks are characteristic peaks of polyurethane. Peaks at 1260 and 788cm-1 are typical vibrational peaks of C-Si-C on polydimethylsiloxane, and peaks 1082 and 1008cm-1 are telescopic vibrational peaks of Si-O-Si on polydimethylsiloxane backbone, and infrared spectra indicate successful synthesis of microcrack resistant prepolymer.

As shown in the Raman spectrum results in FIG. 4, the peak at 490cm-1 is the vibration of Si-O-Si bond, and the shoulder peak (marked by a circle in FIG. 4) appearing at 527cm-1 is the vibration peak of S-S bond. The peak at 1086cm-1 is the vibrational peak of the C-S bond attached to the benzene ring, and Raman spectrum data indicates successful synthesis of the microcrack resistant prepolymer.

Preparation example two

An anti-microcrack prepolymer comprising the following preparation steps:

(1) 50g of a hydroxyl-terminated polydimethylsiloxane (viscosity 2500 cSt) was placed in a dry flask and heated at 65℃under vacuum for 2 hours to remove moisture and gas, and 8g of toluene-2, 5-diisocyanate and 0.5g of dibutyltin dilaurate were added to the flask and stirred under nitrogen for 2 hours to give a mixture A;

(2) 10g of 3,3' -dihydroxydiphenyl disulfide was dissolved in 50g of tetrahydrofuran at 80℃and added to a flask containing mixture A, and reacted under nitrogen for 40 minutes to obtain an anti-microcrack prepolymer.

Preparation example three

An anti-microcrack prepolymer comprising the following preparation steps:

(1) 40g of hydroxy-terminated polydimethylsiloxane (viscosity 2000 cSt) was placed in a dry flask and heated at 70℃under vacuum for 1 hour to remove moisture and gas, and 6g of hexamethylene diisocyanate and 0.3g of dibutyltin diacetate were added to the flask and stirred under nitrogen for 1 hour to give a mixture A;

(2) 8g of 3,3' -dihydroxydiphenyl disulfide was dissolved in 30g of tetrahydrofuran at 70℃and added to a flask containing mixture A, and reacted under nitrogen for 60 minutes to obtain an anti-microcrack prepolymer.

Example 1

An anti-microcrack coating comprising the following preparation steps: 50g of the microcrack-resistant prepolymer obtained in preparation example I, 3g of white carbon black and 3g of methyl silicone oil are added into a strong dispersing machine to be dispersed for 30 minutes at room temperature until the mixture is uniformly mixed, then 5g of bis (triethoxysilylpropyl) disulfide is added into the mixture, and after the mixture is uniformly mixed, the canning is carried out, thus obtaining the microcrack-resistant coating.

The microcrack resistant paint obtained in the first example was coated on a PVC sheet to a thickness of 0.5mm, and then the surface of the sample was cut by a blade, and in order to more intuitively observe the repair of the wound, the detection was performed by using a 3D super depth microscope, and the repair result was observed for 24 hours, and the result is shown in fig. 5. The material is shown in fig. 5 to have a wound width of 28.5 μm and a depth of 16.54 μm before healing. The wound only keeps a little trace on the surface after self-repairing, and the depth of the wound is basically disappeared, which indicates that the coating has a self-repairing effect.

Example two

An anti-microcrack coating comprising the following preparation steps: adding 60g of the microcrack-resistant prepolymer obtained in the second preparation example, 5g of white carbon black and 5g of methyl silicone oil into a strong dispersing machine, dispersing for 40 minutes at room temperature until the mixture is uniformly mixed to obtain a mixed material, adding 8g of bis [3- (triethoxysilyl) propyl ] tetrasulfide into the mixed material, uniformly mixing, and canning to obtain the microcrack-resistant coating.

Example III

An anti-microcrack coating comprising the following preparation steps: adding 80g of the microcrack-resistant prepolymer obtained in preparation III, 10g of white carbon black and 8g of methyl silicone oil into a strong dispersing machine, dispersing for 60 minutes at room temperature until the mixture is uniformly mixed to obtain a mixed material, adding 10g of bis (triethoxysilylpropyl) disulfide into the mixed material, uniformly mixing, and canning to obtain the microcrack-resistant coating.

Comparative example one

The anti-microcrack coating, the reagents and process parameters used in each step and each step are the same as in example one, except that bis (triethoxysilylpropyl) disulfide is replaced with propyltriethoxysilane.

Comparative example two

The anti-microcrack coating, the reagents and process parameters used in each step are the same as those in example one, except that white carbon black is replaced by carbon black.

Performance test

1. Tear strength: the coatings of examples 1 to 3 and comparative examples 1 to 2 were brushed or sprayed on the surface of the glass insulator, and after 3 days, the coating was completely cured, and the tear strength was measured, and the tear strength (right angle test) of the microcrack-resistant coating was measured according to DL/T627 "room temperature curable silicone rubber anti-fouling flashover coating for insulator" and GB/T529 "measurement of tear strength of vulcanized rubber or thermoplastic rubber (trouser, right angle and crescent test pieces), and the measurement results are shown in table 1.

2. Mechanical breaking strength: the paints of examples 1 to 3 and comparative examples 1 to 2 were brushed or sprayed on the surface of the glass insulator, and after 3 days, the paints were completely cured, and the mechanical breaking strength was measured according to DL/T627 "room temperature curable silicone rubber anti-fouling flashover paint for insulator" and GB/T528 "measurement of tensile stress Strain Properties of vulcanized rubber or thermoplastic rubber", and the measurement results are shown in Table 1.

TABLE 1 Performance test results for examples 1-3 and comparative examples 1-4

Detecting items	Tear strength	Mechanical breaking strength
			Example 1	7.6kN/m	4.3MPa
Example 2	8.2kN/m	5.0MPa
			Example 3	8.3kN/m	4.8MPa
Comparative example 1	5.9kN/m	3.9MPa
			Comparative example 2	5.5kN/m	3.6MPa

As can be seen from the results of table 1, the tear strength and mechanical breaking strength of comparative example 1 are significantly lower than those of example 1, because the disulfide bond of bis (triethoxysilylpropyl) disulfide in example 1 can be reconstructed with the disulfide bond of itself or hydroxydisulfide to form new molecules, thus enhancing the degree of intermolecular crosslinking while achieving self-repairing function, while that of comparative example 1, the bis (triethoxysilylpropyl) disulfide is replaced with propyltriethoxysilane, thus reducing intermolecular crosslinking to some extent, so that the tear strength and mechanical breaking strength are somewhat reduced; the tear and mechanical tear resistance of comparative example 2 is significantly lower than that of example 1 because white carbon black is a nano-sized particle with better dispersibility in the coating matrix than carbon black, and because carbon black is susceptible to agglomeration, the tear and mechanical tear resistance of comparative example 2 is significantly lower than that of example 1, indicating that white carbon black is beneficial for enhancing the coating mechanical properties.

The foregoing embodiments have been provided for the purpose of illustrating the general principles of the present application, and are not to be construed as limiting the scope of the application. It should be noted that any modifications, equivalent substitutions, improvements, etc. made by those skilled in the art without departing from the spirit and principles of the present application are intended to be included in the scope of the present application.

Claims (8)

1. The microcrack resistant coating is characterized by comprising the following components in parts by weight:

microcrack resistant prepolymer: 40-80 parts;

white carbon black: 3-10 parts;

methyl silicone oil: 3-8 parts;

sulfur-containing silane coupling agent: 5-10 parts;

the preparation method of the microcrack-resistant prepolymer comprises the following preparation steps:

(1) Heating hydroxyl-terminated polydimethylsiloxane under vacuum condition to remove water and gas, adding diisocyanate and an organotin catalyst, and stirring under the protection of oxygen-isolated atmosphere to obtain a mixture A;

(2) Dissolving hydroxy disulfide in tetrahydrofuran at 65-80 deg.c, and adding the dissolved hydroxy disulfide into the container with mixture A for reaction in oxygen isolating atmosphere for 30-60 min to obtain micro crack resisting prepolymer;

the sulfur-containing silane coupling agent is bis (triethoxysilylpropyl) disulfide or bis [3- (triethoxysilylpropyl ] tetrasulfide.

2. An anti-microcrack coating as claimed in claim 1, wherein the anti-microcrack prepolymer comprises the following components in parts by weight:

hydroxy-terminated polydimethylsiloxane: 30-50 parts;

a diisocyanate: 5-8 parts;

organotin catalyst: 0.1 to 0.5 part;

hydroxy disulfide: 5-10 parts;

tetrahydrofuran: 30-50 parts.

3. The microcrack resistant coating of claim 1 wherein in step (1) of the microcrack resistant prepolymer preparation process the diisocyanate is one or more of toluene-2, 5-diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate and tetramethylxylylene diisocyanate.

4. An anti-microcrack coating as claimed in claim 1 wherein in step (2) of the method of preparing an anti-microcrack prepolymer, the hydroxydisulfide is bis (4-hydroxyphenyl) disulfide or 3,3' -dihydroxydiphenyl disulfide.

5. An anti-microcrack coating as claimed in claim 1 wherein in step (1) of the method for preparing an anti-microcrack prepolymer, the organotin catalyst is stannous octoate, dibutyltin di (dodecylsulfide) or dibutyltin diacetate.

6. An anti-microcrack coating as claimed in claim 1, wherein in step (1) of the preparation method of the anti-microcrack prepolymer, the temperature at which water and gas are removed by heating under vacuum of the hydroxy-terminated polydimethylsiloxane is 65-80 ℃; the stirring time is 1-2h.

7. An anti-microcrack coating as claimed in claim 1 wherein said hydroxy-terminated polydimethylsiloxane has a viscosity of 2000 to 3000cst.

8. A method of preparing an anti-microcrack coating according to any one of claims 1 to 7, comprising the steps of: adding the microcrack-resistant prepolymer, white carbon black and methyl silicone oil into dispersing equipment for dispersing until the mixture is uniformly mixed to obtain a mixed material, adding a sulfur-containing silane coupling agent into the mixed material, uniformly mixing, and canning to obtain the microcrack-resistant coating.