White carbon black interface crosslinking-based polyurethane rubber composite material and preparation method thereof

Abstract

The invention discloses a polyurethane rubber composite material based on white carbon black interface crosslinking and a preparation method thereof. The prepared blended cross-linked composite material is constructed through the synergistic effect of disulfide bonds and multiple hydrogen bonds, the multiple hydrogen bonds serve as sacrificial units to dissipate energy under the action of external force, and the enhancement effect is achieved. Dynamic bonds (disulfide bonds and multiple hydrogen bonds) in the blended cross-linked composite material have high dynamic characteristics, the material is endowed with good self-repairing performance and excellent recoverability, the service life of the material is effectively prolonged, and the material can be recycled. In the cyclic processing process of the blended cross-linked composite material, disulfide bonds are broken to form sulfur free radicals, the sulfur free radicals and vinyl on a side chain of a polyurethane matrix generate new cross-linking points, the cross-linking density is increased, the mechanical property of the material is improved, and the material is endowed with the recovery self-reinforcing characteristic.

Description

Technical Field

[0001] The invention belongs to the field of functional rubber, and particularly relates to a polyurethane rubber composite material based on silica interfacial cross-linking and a preparation method thereof. Background Art

[0002] The covalently cross-linked network of rubber materials is essential for achieving high elasticity, mechanical strength, and environmental resistance. Conventional vulcanization systems form permanent crosslinks through irreversible C-S / C-C bonds. While this imparts excellent properties to the material, it also makes the cross-linked rubber difficult to recycle. Existing waste rubber treatment technologies, such as incineration and landfilling, pose serious environmental challenges, while desulfurization and regeneration processes significantly degrade mechanical properties due to backbone chain degradation. Against this backdrop, Leibler's Vitrimer concept offers a new approach to reversible crosslinking in rubber—material remodeling through topological rearrangement of dynamic covalent bonds under external stimuli.

[0003] The terminal hydroxyl groups on the backbone of commercially available liquid polyethylene (HTPB) react with isocyanates and, without further treatment, can be used as the raw material for the soft segment of polyurethane rubber materials. Although the urethane and urea groups on the backbone of HTPB-based polyurethane rubber materials form abundant hydrogen bonds, which can improve the mechanical properties and impart certain repair capabilities, the low singlet hydrogen bond energy results in generally weak mechanical and creep resistance in HTPB-based polyurethane rubber materials. To address this issue, constructing effective filler-reinforced systems to achieve high mechanical properties in polymer composites is a common strategy. However, the use of fillers requires consideration of filler agglomeration and the control of the filler-matrix interface, which are crucial for the mechanical properties of polymer materials. Furthermore, the incorporation of fillers may restrict the migration of polymer chains, hinder topological rearrangement during recycling, and adversely affect stress relaxation behavior, ultimately sacrificing the repair and recycling properties of the polymer material. This may explain the limited reports on filler-reinforced, self-healing, and recyclable polyurethane rubber materials.

[0004] Nano-silica has been widely used in the rubber industry due to its significant reinforcing effect and has now become the second largest reinforcing filler after carbon black. For reinforced polyurethane rubber materials, in addition to considering the problems of easy agglomeration of nano-silica in the system and poor compatibility with the polyurethane rubber matrix, how to avoid the reaction of silanol groups on the surface of nano-silica with isocyanate in the reaction system is also a question worth considering. In addition, for recyclable elastomers, there are almost unavoidable side reactions (oxidation, permanent cross-linking) during the heat recovery process, which leads to a decrease in the mechanical properties of the elastomer after reprocessing. Therefore, how to balance the relationship between the mechanical properties of polymer materials and the recyclable processing performance remains a scientific challenge.

[0005] Therefore, it is of great significance to prepare a polyurethane rubber composite with excellent mechanical properties, self-healing and recyclability. Summary of the Invention

[0006] In order to solve the above problems, the present invention provides a polyurethane rubber composite material based on silica interfacial cross-linking and a preparation method thereof, wherein functionalized silica containing urea groups and disulfide bonds is used as a reinforcing agent and cross-linking agent, a disulfide bond and multiple hydrogen bond cross-linking network is constructed at the silica-rubber interface, thereby realizing the repair and recycling functions of the composite material; the cross-linking density of the composite material is adjusted by the content of functionalized silica, thereby improving the mechanical properties of the composite material.

[0007] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a polyurethane rubber composite material based on silica interfacial crosslinking, comprising a blended and crosslinked composition of functionalized silica containing urea groups and disulfide bonds and liquid rubber-based polyurethane; the functionalized silica containing urea groups and disulfide bonds and the liquid rubber-based polyurethane are network crosslinked through disulfide bonds and multiple hydrogen bonds at the silica-polyurethane rubber interface.

[0008] A method for preparing a polyurethane rubber composite material based on silica interfacial crosslinking, comprising the preparation of functionalized silica containing urea groups and disulfide bonds and the preparation of liquid rubber-based polyurethane;

[0009] The preparation process of the functionalized silica containing urea groups and disulfide bonds is as follows:

[0010] 1) After isophorone diisocyanate and 4,4'-diaminodiphenyl disulfide are stirred and reacted at room temperature for 10 to 12 hours, 3-aminopropyltriethoxysilane is added and the reaction is continued for 5 to 8 hours to obtain a silane coupling agent (APDA) containing urea groups and disulfide bonds, the structural formula of which is as follows:

[0011]

[0012] 2) dispersing silica and a silane coupling agent (APDA) containing urea groups and disulfide bonds, reacting the mixture at 70-85° C. with stirring for 6-8 hours, filtering the mixture through anhydrous ethanol, centrifuging the mixture, and vacuum drying the mixture at 55° C. to a constant weight to obtain functionalized silica containing urea groups and disulfide bonds;

[0013] The preparation process of the liquid rubber-based polyurethane is as follows: first, the liquid rubber isocyanate is capped, and then completely reacted with isophorone diisocyanate and 4,4'-diaminodiphenyl disulfide under the action of a catalyst to obtain the liquid rubber-based polyurethane;

[0014] Functionalized white carbon black containing urea groups and disulfide bonds is blended and stirred with liquid rubber-based polyurethane, and then subjected to solvent volatilization and high-temperature curing to form the composite material.

[0015] In step 1), the molar ratio of isophorone diisocyanate, 4,4'-diaminodiphenyl disulfide, and 3-aminopropyltriethoxy is 2:2:1; and in step 2), the mass ratio of white carbon black to the silane coupling agent containing urea groups and disulfide bonds is 2:1.

[0016] The catalyst is dibutyltin dilaurate, and the dosage is 10%-25% of the mass of white carbon black; the reaction time is 10-12 hours, and the reaction temperature is 70-80°C.

[0017] The curing time is 10 to 16 hours, and the curing temperature is 110 to 120°C.

[0018] Compared with the prior art, the blended cross-linked composite material prepared by the present invention is constructed through the synergistic effect of disulfide bonds and multiple hydrogen bonds. The multiple hydrogen bonds act as sacrificial units to dissipate energy under the action of external forces, playing a reinforcing role. The dynamic bonds (disulfide bonds, multiple hydrogen bonds) inside the blended cross-linked composite material of the present invention have highly dynamic characteristics, giving the material good self-repairing properties and excellent recyclability, effectively extending the service life and recycling of the material. During the recycling process of the blended cross-linked composite material of the present invention, the disulfide bonds break to form sulfur free radicals, and new cross-linking points are generated with the vinyl groups on the side chains of the polyurethane matrix, the cross-linking density increases, the mechanical properties of the material are improved, and the material is given the characteristic of self-recycling. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the structure of the polyurethane rubber composite material described in the embodiment;

[0020] Figure 2 This is the infrared spectrum of the functionalized silica described in the examples;

[0021] Figure 3 This is an optical microscope photograph of the self-healing behavior of the polyurethane rubber composite material described in the example;

[0022] Figure 4 This is a picture of repeated processing of the polyurethane rubber composite material described in the example;

[0023] Figure 5 1 is the stress-strain curve of the polyurethane rubber composite material described in Examples and Comparative Examples;

[0024] Figure 6 This is the stress-strain curve of the recycled polyurethane rubber composite material described in Example 3. DETAILED DESCRIPTION

[0025] In order to better explain the present invention, the main contents of the present invention are further illustrated below in conjunction with specific examples, but the contents of the present invention are not limited to the following examples.

[0026] Example 1:

[0027] (1) Preparation of functionalized silica containing urea groups and disulfide bonds: First, accurately weigh 2.67 g of isophorone diisocyanate and 1.5 g of 4,4'-diaminodiphenyl disulfide and dissolve them in 15 mL of acetone solution. Under a nitrogen atmosphere, magnetic stirring is carried out at room temperature for 10 h to obtain a diisocyanate-terminated polyurea prepolymer. Then, weigh 2.67 g of 3-aminopropyltriethoxysilane and dissolve it in 5 mL of acetone. It is slowly added dropwise to the diisocyanate-terminated polyurea prepolymer (the addition time is controlled to be about 15 min). The reaction is continued at room temperature for 6 h. Then, it is placed in a fume hood to evaporate the acetone to dryness to obtain a silane coupling agent containing urea groups and disulfide bonds. Finally, weigh 5.0 g of silica and disperse it in 100 mL of anhydrous ethanol. Then, 6.5 g of the silane coupling agent containing urea groups and disulfide bonds is added and stirred in an oil bath at 75°C for 6 h. The product was then centrifuged to obtain the product, which was finally washed with anhydrous ethanol several times, centrifuged, and placed in a vacuum drying oven at 50° C. to dry to constant weight to obtain functionalized silica.

[0028] (2) Preparation of isocyanate-terminated polybutadiene: 5 g of hydroxyl-terminated polybutadiene rubber and 0.75 g of isophorone diisocyanate were weighed and placed in a sample bottle. The mixture was magnetically stirred at 80° C. for 3 h under a nitrogen atmosphere to prepare isocyanate-terminated polybutadiene.

[0029] (3) Preparation of functionalized silica / polyurethane rubber composites: Weigh 0.5g of functionalized silica and place it in 50mL of toluene for ultrasonic dispersion for 15min, and set aside. Weigh 9.2g of isocyanate-terminated polybutadiene, 0.58g of isophorone diisocyanate and 1.99g of 4,4'-diaminodiphenyl disulfide and dissolve them in 150mL of toluene. Add 0.2-0.5g of dibutyltin dilaurate and react at 70℃ for 12h. Then, add the above functionalized silica solution dropwise to the reaction system, stir evenly for 15min, and ultrasonicate for 30min. Then pour the mixed glue into a polytetrafluoroethylene mold, place it in a fume hood at room temperature to evaporate the solvent, then place it at 70℃ for 3h, and finally cure it in a vacuum oven at 120℃ for 10h.

[0030] Example 2

[0031] The amount of functionalized silica added was 1.0 g. The preparation steps were exactly the same as those in Example 1.

[0032] Example 3

[0033] The amount of functionalized silica added was 1.5 g. The preparation steps were exactly the same as those in Example 1.

[0034] Example 4

[0035] The amount of functionalized silica added was 2.0 g. The preparation steps were exactly the same as those in Example 1.

[0036] Comparative Example 1

[0037] Preparation of polyurethane rubber: 9.2 g of isocyanate-terminated polybutadiene, 0.58 g of isophorone diisocyanate, and 0.48 g of trimethylolpropane were dissolved in 150 mL of toluene. 0.2–0.5 g of dibutyltin dilaurate was added and reacted at 70°C for 12 h. The rubber solution was then poured into a polytetrafluoroethylene mold and placed in a fume hood at room temperature to evaporate the solvent. The mixture was then placed at 70°C for 3 h and finally cured in a vacuum oven at 120°C for 10 h to produce the polyurethane rubber.

[0038] Comparative Example 2

[0039] Preparation of silica / polyurethane rubber composites: Weigh 2.0g of silica and dissolve it in 50mL of toluene under ultrasonication for 15 minutes. Then, weigh 9.2g of isocyanate-terminated polybutadiene, 0.58g of isophorone diisocyanate, and 1.99g of 4,4'-diaminodiphenyl disulfide and dissolve them in 150mL of toluene. Add 0.2-0.5g of dibutyltin dilaurate and react at 70°C for 12 hours. Then, add the silica solution dropwise to the reaction system, stir evenly for 15 minutes, and sonicate for 30 minutes. The resulting mixture is then poured into a polytetrafluoroethylene mold and placed in a fume hood at room temperature to evaporate the solvent. The mixture is then placed at 70°C for 3 hours and cured in a vacuum oven at 120°C for 10 hours.

[0040] according to Figure 5 As can be seen, as the functionalized silica content gradually increases, the tensile strength, modulus, and toughness of the polyurethane rubber composite samples all significantly improve. This is due to the good reinforcing effect of functionalized silica as a reinforcing agent, which effectively enhances the mechanical properties of the material. At the same time, the addition of functionalized silica increases the crosslinking density and multiple hydrogen bond content in the system, which is also an important factor in improving the mechanical properties of the material.

[0041] according to Figure 6 It can be seen that as the number of repeated processing increases, the mechanical properties of the sample show an increasing trend. Compared with the initial sample, after two repeated processing, the tensile strength of the sample increased by 16.2% to 2.96MPa; the elongation at break increased by 9.7% to 342%; the modulus increased by 33.6% to 3.27MPa; and the toughness increased by 34.1% to 5.94MJ / m 3 During the processing, the disulfide bonds are broken to generate sulfur free radicals, which react with the side vinyl groups on the polyurethane rubber molecular chain, forming a denser cross-linked network at high temperature, which ultimately leads to the enhancement of mechanical properties.

Claims

1. A polyurethane rubber composite material based on silica interfacial crosslinking, characterized in that: It includes a cross-linked composition of a blend of functionalized silica containing urea groups and disulfide bonds and liquid rubber-based polyurethane; the functionalized silica containing urea groups and disulfide bonds and the liquid rubber-based polyurethane are cross-linked through disulfide bonds and multiple hydrogen bonds at the silica-polyurethane rubber interface to achieve network cross-linking.

2. The method for preparing a polyurethane rubber composite material based on silica interfacial crosslinking according to claim 1, characterized in that: Including the preparation of functionalized silica containing urea groups and disulfide bonds and the preparation of liquid rubber-based polyurethane; The preparation process of the functionalized silica containing urea groups and disulfide bonds is as follows: 1) After isophorone diisocyanate and 4,4'-diaminodiphenyl disulfide are stirred and reacted at room temperature for 10 to 12 hours, 3-aminopropyltriethoxysilane is added and the reaction is continued for 5 to 8 hours to obtain a silane coupling agent containing urea groups and disulfide bonds, the structural formula of which is as follows: 2) dispersing silica and the silane coupling agent containing urea groups and disulfide bonds obtained in step 1) and mixing them, stirring and reacting at 70-85° C. for 6-8 hours, filtering through anhydrous ethanol, centrifuging, and vacuum drying at 55° C. to constant weight to obtain functionalized silica containing urea groups and disulfide bonds; The preparation process of the liquid rubber-based polyurethane is as follows: first, the liquid rubber isocyanate is capped, and then completely reacted with isophorone diisocyanate and 4,4'-diaminodiphenyl disulfide under the action of a catalyst to obtain the liquid rubber-based polyurethane; Functionalized white carbon black containing urea groups and disulfide bonds is blended and stirred with liquid rubber-based polyurethane, and then subjected to solvent volatilization and high-temperature curing to form the composite material.

3. The method for preparing a polyurethane rubber composite material based on silica interfacial crosslinking according to claim 2, characterized in that: In step 1), the molar ratio of isophorone diisocyanate, 4,4'-diaminodiphenyl disulfide, and 3-aminopropyltriethoxy is 2:2:1; and in step 2), the mass ratio of white carbon black to the silane coupling agent containing urea groups and disulfide bonds is 2:

1.

4. The method for preparing a polyurethane rubber composite material based on silica interfacial crosslinking according to claim 2, characterized in that: The catalyst is dibutyltin dilaurate, and the dosage is 10%-25% of the mass of white carbon black; the reaction time is 10-12 hours, and the reaction temperature is 70-80°C.

5. The method for preparing a polyurethane rubber composite material based on silica interfacial crosslinking according to claim 2, characterized in that: The curing time is 10 to 16 hours, and the curing temperature is 110 to 120°C.

Images