High-strength transparent polyurethane plate based on hydrogen bond and pi-pi stacking synergistic enhancement and preparation method of high-strength transparent polyurethane plate

Abstract

The invention relates to a high-strength transparent polyurethane plate based on hydrogen bond and pi-pi stacking synergistic enhancement and a preparation method of the high-strength transparent polyurethane plate. The high-strength transparent polyurethane plate comprises the following raw material components: polyisocyanate, a polyol chain extender, a cross-linking agent, a solvent and a catalyst, the cross-linking agent contains a plurality of hydroxyl groups. The plate provided by the invention has the comprehensive characteristics of high transparency and good size and thermal stability, shows excellent optical stability and low yellowing tendency in long-term use, and can be widely applied to the fields of high-end transparent structural members, optical covers, protective windows, precise display windows and the like; and the engineering application requirements of high transparency, high strength and stability can be effectively met.

Description

Technical Field

[0001] This invention belongs to the field of polyurethane sheet technology, and specifically relates to a high-strength transparent polyurethane sheet based on the synergistic reinforcement of hydrogen bonding and π-π stacking, and its preparation method. Background Technology

[0002] Traditional transparent structural components are mainly made of acrylic and polycarbonate sheets. Acrylic has poor temperature resistance, and polycarbonate is prone to yellowing, failing to meet the growing demands. In the rail transportation sector, transparent structural components have stringent requirements for material light transmittance, weather resistance, and mechanical strength. Currently, the mainstream polymethyl methacrylate (acrylic, PMMA) and polycarbonate (PC) materials have significant performance bottlenecks: although acrylic has a light transmittance as high as 92%, it is prone to softening and deformation at high temperatures, and its molecular chain rigidity is low, resulting in poor impact resistance; while polycarbonate possesses high mechanical strength and heat resistance, the bisphenol A structure in its molecular chain is easily oxidized and broken under ultraviolet light, heat, oxygen, and humid environments, leading to rapid yellowing. There is an urgent need to develop high-performance new materials to solve these problems.

[0003] In traditional rail transit, transparent structural components such as train windows, platform screen doors, lighting fixtures, and signal display panels are crucial for ensuring passenger safety and enhancing the riding experience due to their combination of light transmission and structural load-bearing capacity. With the increasing prevalence of high-speed trains and subways, these structural components not only need to meet requirements for high light transmittance and high mechanical strength (impact resistance and vibration resistance), but also require stringent performance characteristics. While commonly used polycarbonate (PC) and acrylic resin (PMMA) offer excellent light transmittance, their pure resin properties are poor. Therefore, developing a new high-performance transparent material has become a key technical challenge in addressing the safety and performance bottlenecks of transparent structural components in rail transit. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a high-strength transparent polyurethane sheet material based on the synergistic reinforcement of hydrogen bonding and π-π stacking and its preparation method. The sheet material has comprehensive characteristics of high transparency, good dimensional and thermal stability, and exhibits excellent optical stability and low yellowing tendency in long-term use. It can be widely used in high-end transparent structural components, optical covers, protective windows and precision display windows, etc., and can effectively meet the engineering application requirements of high transparency, high strength and stability.

[0005] This invention provides a high-strength transparent polyurethane sheet material based on the synergistic reinforcement of hydrogen bonding and π-π stacking. The raw material components, by weight, include:

[0006] 1-90 parts of polyisocyanate;

[0007] 1-70 parts of polyol chain extender;

[0008] 1-20 parts of crosslinking agent;

[0009] Solvent: 10-100 parts;

[0010] 0-5 parts of catalyst;

[0011] The crosslinking agent contains multiple hydroxyl groups.

[0012] Preferably, the polyisocyanate includes at least one of 4,4'-methylene bis(phenyl isocyanate), toluene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane-diisocyanate, naphthalene diisocyanate, terephthalic diisocyanate, 1,4-cyclohexane diisocyanate, phenyl dimethylene diisocyanate, tetramethyl isophthalic diisocyanate, dimethyl biphenyl diisocyanate, polymethylene polyphenyl isocyanate, and modified diisocyanate (such as liquefied MDI from Yantai Wanhua).

[0013] Preferably, the polyol chain extender includes p-phenylenediethanol, dihydroxydiphenylsilane, resorcinol, catechol, 2,2-bis(4-hydroxyphenyl)propane, biphenyl, [1,1':4',1''-terphenyl]-4,4''-diol, 4-amino-4-hydroxybiphenyl, 4-(4-hydroxymethylphenyl)phenol, 4,4'-dihydroxydiphenyl sulfone, 4-hydroxythiophenol, [1,1:3,1 One or more of the following: [-terphenyl]-4,4'-diol, 1,5-pentanediol, p-aminophenol, [1,1-bisphenyl]-2,4-diol, p-hydroxybenzyl alcohol, 4,4'-(ethylene-1,1-diyl)biphenol, 4,4'-dihydroxymethylbiphenyl, 1,3-bis(4-hydroxyphenyl)propane, biphenyl-4,4'-dithiol, 2,6-dihydroxynaphthalene, bis(4-hydroxybenzene)1,4-diisopropylbenzene, and 2,7-dihydroxynaphthalene.

[0014] Preferably, the crosslinking agent includes one or more of glycerol, trimethylolethane, trimethylolpropane, 2-aminophenyl-1,4-diol, 1,2,5-pentanetriol, 1,2,3-butanetriol, 1,2,6-hexanetriol, 2-amino-1,3-propanediol, and tris(2-hydroxyethyl)isocyanurate.

[0015] Preferably, the solvent includes one or more of acetone, methyl ethyl ketone, cyclohexanone, tetrahydrofuran, N,N'-dimethylformamide, N,N'-dimethylacetamide, N-methylpyrrolidone, ethyl acetate, butyl acetate, ethylene glycol ethyl ether acetate, and dichloromethane.

[0016] Preferably, the catalyst includes one or more of organometallic catalysts and tertiary amine catalysts.

[0017] This invention also provides a method for preparing a high-strength transparent polyurethane sheet based on the synergistic reinforcement of hydrogen bonding and π-π stacking, comprising the following steps:

[0018] (1) The polyol chain extender was vacuum stirred and dehydrated at 80-100℃ for 1-5h, and then cooled to 50-70℃ to obtain the pretreated product;

[0019] (2) Add the solvent to the above pretreated product, stir evenly under inert protective gas, then add polyisocyanate and react at 50-120℃ for 1-24 hours, then add crosslinking agent and continue to react for 1-5 hours to obtain polyurethane product.

[0020] (3) Apply the polyurethane product onto an iron plate and place it in a vacuum oven at 50-110°C for 2-24 hours. Then, maintain the vacuum state for 2-24 hours to remove the solvent in the reaction system, and a transparent polyurethane board is obtained.

[0021] Beneficial effects

[0022] This invention achieves comprehensive performance through molecular structure regulation and synergistic network design: sterically hindered aromatic diisocyanates and aromatic polyols are selected as the main monomers, and short-chain crosslinking agents are introduced to construct a dense carbamate network. Furthermore, the π–π stacking of aromatic rings is utilized to suppress crystallization and phase separation, forming an amorphous, homogeneous glassy structure. This significantly improves strength and rigidity while maintaining high transmittance and low haze. The resulting sheet material exhibits a combination of high transparency, good dimensional and thermal stability, and demonstrates excellent optical stability and low yellowing tendency during long-term use. It can be widely used in high-end transparent structural components, optical covers, protective windows, and precision display windows, effectively meeting the engineering application requirements that emphasize high transparency, high strength, and stability. Attached Figure Description

[0023] Figure 1 A photograph (a) of the transparent polyurethane sheet prepared for the example under natural ambient light and a transmittance diagram (b) of other transparent materials in ultraviolet light testing.

[0024] Figure 2 Infrared spectrum (a) of the transparent polyurethane sheet prepared for the example and its infrared spectrum in the range of 1750~1625 cm⁻¹ -1 Carbonyl peaks (b) are observed between these peaks.

[0025] Figure 3 The mechanical properties (a), toughness (b), and mechanical properties (c) of the transparent polyurethane sheets prepared for the examples are compared. Detailed Implementation

[0026] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0027] raw material:

[0028] Biphenyl hydroquinone was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., glycerol was purchased from Sinopharm Chemical Reagent Co., Ltd., and 4,4'-methylene bis(phenyl isocyanate) and tris(2-hydroxyethyl) isocyanurate were purchased from Wanhua Chemical Group Co., Ltd.

[0029] Relevant test content:

[0030] Structural characterization: The structures of the crosslinked polyurethane before and after synthesis were characterized using Fourier transform infrared spectroscopy (FTIR). Attenuated total reflectance (ATR) spectroscopy was used for testing, with 32 scans performed and a wavelength range of 4000-400 cm⁻¹. -1 Spectral resolution of 4 cm -1 .

[0031] Transmittance Characterization: The transmittance of cross-linked polyurethane sheets was characterized using a UV-Vis spectrophotometer (model: UV-3600, Shimadzu Corporation). The scanning mode was set to transmission spectroscopy, with 16 scans, a wavelength range of 200-800 nm, a spectral resolution of 1 nm, and a scanning speed of medium (240 nm / min). Air was used as a reference for instrument calibration before testing, and a standard quartz cuvette (10 mm optical path) was used as a blank control. Three different regions of each sample were selected for testing, and the final results were averaged. Data processing and analysis were performed according to GB / T2410-2008 "Determination of transmittance and haze of transparent plastics".

[0032] Characterization of mechanical properties of transparent polyurethane sheets: In the following examples, the mechanical properties of transparent polyurethane sheets were characterized using a universal testing machine. Rectangular strips were cut from the prepared samples, and the mechanical properties of the materials were tested at room temperature. The uniaxial tensile rate was set to 50 mm / min.

[0033] Example 1

[0034] By mass, 70 parts of terephthalic acid were placed under vacuum at 110°C for 2 hours to remove water. Then, 100 parts of tetramethylbenzene dimethyl diisocyanate and 100 parts of dimethylformamide were added and reacted under nitrogen protection at 80°C for 4 hours. Then, 30 parts of glycerol were added and reacted for 1 hour. The mixture was then coated onto an iron plate and placed in a 50°C oven to continue the reaction for 24 hours. After that, the solvent was removed under vacuum at 75°C to obtain a transparent polyurethane board, which was designated as FPU-1.

[0035] Example 2

[0036] By mass, 70 parts of terephthalic acid were placed under vacuum at 110°C for 2 hours to remove water. Then, 100 parts of tetramethylbenzene dimethyl diisocyanate and 100 parts of dimethylformamide were added and reacted under nitrogen protection at 80°C for 4 hours. Then, 30 parts of tris(2-hydroxyethyl) isocyanurate were added and reacted for 1 hour. The mixture was then coated onto an iron plate and placed in a 50°C oven to continue the reaction for 24 hours. After that, the solvent was removed under vacuum at 75°C to obtain a transparent polyurethane board, which was designated as FPU-2.

[0037] Test case

[0038] like Figure 1 Image a shows the material under natural light. The example material achieves high optical transparency in the visible light region, exhibiting beneficial transparency under natural sunlight. Figure 1 a. The transmittance of the sheet material prepared in the example and commercially available transparent materials was tested. Both FPU-1 and FPU-2 exhibited high transparency, with an average transmittance exceeding 90% for a 1 mm thick FPU block sample in the visible light wavelength range of 400-800 nm. Figure 1 (b) Compared with other transparent materials (PMMA, PC, PS, glass), the transmittance at 550 nm is as high as 92.2%, demonstrating high transparency. This indicates that the substrate of this invention has significant application value in optical devices, transparent structural components, and other fields.

[0039] like Figure 2 The infrared spectrum shown in Figure a indicates that the plates prepared in Examples 1 and 2 have an infrared spectrum at a wavelength of 3335 cm⁻¹. -1 The stretching vibration peak of NH was observed in all samples, with a peak at 1698 cm⁻¹. -1 The presence of C=O stretching vibrations indicates the successful synthesis of the carbamate bond, and the vibrations also occurred at 1460-1600 cm⁻¹. -1 The presence of C=C stretching vibrations in the region indicates that the isocyanate reacted with the hydroxyl group to form a carbamate bond, proving that the reaction was complete. At 778 cm⁻¹ -1The region exhibits characteristic out-of-plane bending vibration peaks of CH associated with benzene ring substitution modes. The presence and significant intensity of these benzene ring characteristic vibration peaks, combined with their peak positions and shapes, indicate the presence of numerous benzene ring structures in the polyurethane material prepared in this invention. Furthermore, the peaks at 1625 to 1750 cm⁻¹... -1 The spectral region between them was deconvolved into three distinct peaks. Specifically, such as Figure 2 As shown in b, 1725 cm -1 The peak at 1690 cm⁻¹ (Free C=O) corresponds to the vibrations of free carbamate and carbonyl groups. -1 This represents the carbonyl group that forms an ordered hydrogen bond cluster. 1650 cm -1 The peaks at the peaks are attributed to urethane and carbonyl groups involved in random, disordered hydrogen bonding. The integrated peak area results show that FPU-1 has a high hydrogen-bonded carbonyl ratio of 78.87%, while FPU-2 has a hydrogen-bonded carbonyl ratio of 72%, with the former significantly higher than the latter. This difference stems from the different molecular volumes of the hydroxyl compounds used in the two products—FPU-1 uses glycerol as a raw material, while FPU-2 uses tris(2-hydroxyethyl) isocyanurate. The latter has a larger molecular volume than glycerol, resulting in a less dense packing of hydrogen bonds between the molecules, thus causing the difference in hydrogen bonding effectiveness. These findings indicate that FPU contains a dense hydrogen bond network. This structure endows the sheet with a rigid framework and unique properties, providing a structural basis for its application in optical devices, transparent structural components, and other fields.

[0040] like Figure 3 As shown in the mechanical curves, the mechanical strength of the plates prepared in Examples 1 and 2 both reached over 100 MPa. The Young's modulus of Example 1 reached 2.8 GPa, and the Young's modulus of Example 2 reached 2.2 GPa (as shown in Figure a). Figure 3 b). For example Figure 3 The mechanical performance test diagram shown in Figure c indicates that, compared with conventional transparent materials (such as acrylic 73 MPa and polycarbonate about 68 MPa), the sheet material of this invention achieves a significant improvement in mechanical strength and rigidity while maintaining high light transmittance. Its comprehensive mechanical properties meet or exceed the performance requirements of transparent structural components in aerospace, high-speed transportation and other fields. It has outstanding technical advantages and industrial application prospects in replacing traditional transparent materials.

Claims

1. A high-strength transparent polyurethane sheet material based on the synergistic reinforcement of hydrogen bonding and π-π stacking, characterized in that, According to parts by mass, its raw material components include: 1-90 parts of polyisocyanate; 1-70 parts of polyol chain extender; 1-20 parts of crosslinking agent; Solvent: 10-100 parts; 0-5 parts of catalyst; The crosslinking agent contains multiple hydroxyl groups.

2. The high-strength transparent polyurethane sheet material based on the synergistic reinforcement of hydrogen bonding and π-π stacking according to claim 1, characterized in that, The polyisocyanate includes at least one of 4,4'-methylene bis(phenyl isocyanate), toluene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane-diisocyanate, naphthalene diisocyanate, terephthalic diisocyanate, 1,4-cyclohexane diisocyanate, phenyl diisocyanate, tetramethyl isophthalic diisocyanate, dimethyl biphenyl diisocyanate, polymethylene polyphenyl isocyanate, and modified diisocyanate.

3. The high-strength transparent polyurethane sheet material based on the synergistic reinforcement of hydrogen bonding and π-π stacking according to claim 1, characterized in that, The polyol chain extender includes p-phenylenediamine, dihydroxydiphenylsilane, resorcinol, catechol, 2,2-bis(4-hydroxyphenyl)propane, biphenyl, [1,1':4',1''-terphenyl]-4,4''-diol, 4-amino-4-hydroxybiphenyl, 4-(4-hydroxymethylphenyl)phenol, 4,4'-dihydroxydiphenyl sulfone, 4-hydroxythiophenol, [1,1:3,1 One or more of the following: [-terphenyl]-4,4'-diol, 1,5-pentanediol, p-aminophenol, [1,1-bisphenyl]-2,4-diol, p-hydroxybenzyl alcohol, 4,4'-(ethylene-1,1-diyl)biphenol, 4,4'-dihydroxymethylbiphenyl, 1,3-bis(4-hydroxyphenyl)propane, biphenyl-4,4'-dithiol, 2,6-dihydroxynaphthalene, bis(4-hydroxybenzene)1,4-diisopropylbenzene, and 2,7-dihydroxynaphthalene.

4. The high-strength transparent polyurethane sheet material based on the synergistic reinforcement of hydrogen bonding and π-π stacking according to claim 1, characterized in that, The crosslinking agent includes one or more of glycerol, trimethylolethane, trimethylolpropane, 2-aminophenyl-1,4-diol, 1,2,5-pentanetriol, 1,2,3-butanetriol, 1,2,6-hexanetriol, 2-amino-1,3-propanediol, and tris(2-hydroxyethyl)isocyanurate.

5. The high-strength transparent polyurethane sheet material based on the synergistic reinforcement of hydrogen bonding and π-π stacking according to claim 1, characterized in that, The solvent includes one or more of acetone, methyl ethyl ketone, cyclohexanone, tetrahydrofuran, N,N'-dimethylformamide, N,N'-dimethylacetamide, N-methylpyrrolidone, ethyl acetate, butyl acetate, ethylene glycol ethyl ether acetate, and dichloromethane.

6. The high-strength transparent polyurethane sheet material based on the synergistic reinforcement of hydrogen bonding and π-π stacking according to claim 1, characterized in that, The catalyst includes one or more of organometallic catalysts and tertiary amine catalysts.

7. A method for preparing a high-strength transparent polyurethane sheet based on the synergistic reinforcement of hydrogen bonding and π-π stacking as described in any one of claims 1-6, characterized in that, Includes the following steps: (1) The polyol chain extender was vacuum stirred and dehydrated at 80-100℃ for 1-5h, and then cooled to 50-70℃ to obtain the pretreated product; (2) Add the solvent to the above pretreated product, stir evenly under inert protective gas, then add polyisocyanate and react at 50-120℃ for 1-24 hours, then add crosslinking agent and continue to react for 1-5 hours to obtain polyurethane product. (3) Apply the polyurethane product onto an iron plate and place it in a vacuum oven at 50-110°C for 2-24 hours. Then, maintain the vacuum state for 2-24 hours to remove the solvent in the reaction system, and a transparent polyurethane board is obtained.

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