High-chemical-resistance TPO material and preparation method thereof

Abstract

The invention relates to the technical field of high polymer materials, and discloses a high-chemical-resistance TPO material which comprises the following components in parts by mass: 55-65 parts of polypropylene; 35 to 45 parts of a styrene-ethylene / butylene-styrene block copolymer; 0.4 to 0.6 part of a furan end-capping reagent; 0.2 to 0.4 part of a maleimide cross-linking agent; 4-6 parts of modified shell powder; 8 to 12 parts of epoxidized cardanol; 2-4 parts of a heat-sensitive microcapsule, wherein the heat-sensitive microcapsule comprises a shell layer and an inner core; and 0.5 to 1.5 parts of a nano cellulose surface treating agent. Through the synergistic effect of a dynamic cross-linked network and fluorocarbon chain surface modification, when the material is in contact with acid, alkali and an organic solvent, reversible cross-linked bonds release local stress through a fracture-reconstruction mechanism, and microcrack propagation is inhibited; and the compact fluorocarbon layer on the surface forms a chemical inert barrier, so that the permeation rate of a corrosive medium is remarkably reduced, and the structural stability and long-term durability of the material in a complex chemical environment are guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, in particular to a highly chemical-resistant TPO material and a preparation method thereof. Background Art

[0002] Traditional thermoplastic polyolefin (TPO) materials face significant shortcomings in chemical resistance, mechanical property balance and functional design.

[0003] Conventional TPO substrates are susceptible to surface powdering and mechanical property degradation due to molecular chain swelling or chemical bond breakage when exposed to acids, bases, or organic solvents. This is particularly true in long-term corrosive environments, where stress cracking and even structural failure can occur. Fluorocarbon coatings or blending modifications are often used to improve chemical resistance, but coatings are prone to peeling, and blending modifications can compromise processing fluidity and make it difficult to achieve lightweighting.

[0004] On the other hand, the foaming process of TPO materials mostly relies on the direct addition of chemical foaming agents, which can easily lead to cell collapse or uneven distribution due to the mismatch between foaming and cross-linking reactions, affecting the coordinated optimization of lightweight and mechanical properties.

[0005] In addition, although the traditional static cross-linking system can improve rigidity, it causes the material to become brittle and non-recyclable, and surface functionalization (such as hydrophobicity) mostly relies on post-processing processes, resulting in problems such as poor durability and insufficient environmental adaptability. Summary of the Invention

[0006] In response to the shortcomings of the existing technology, the present invention provides a highly chemical-resistant TPO material and a preparation method thereof, which solves the technical problem that existing TPO materials are difficult to simultaneously take into account chemical corrosion resistance, mechanical property balance, surface functionalization and recyclability.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions: The first aspect of the present invention provides a highly chemical-resistant TPO material comprising the following components in parts by weight: 55-65 parts of polypropylene; 35-45 parts of styrene-ethylene / butylene-styrene block copolymer; 0.4-0.6 parts of furan capping agent; 0.2-0.4 parts of maleimide crosslinking agent; 4-6 parts of modified shell powder; 8-12 parts of epoxidized cardanol; 2 to 4 parts of thermosensitive microcapsules, wherein the thermosensitive microcapsules include a shell and a core; 0.5-1.5 parts of nanocellulose surface treatment agent.

[0008] Preferably, the modified shell powder is a calcium carbonate-silicon dioxide core-shell structure, with polydopamine and perfluorohexyl grafted on the surface in sequence, and the fluorocarbon chain grafting rate is 5-8%.

[0009] Preferably, the shell of the thermosensitive microcapsule is a copolymer of polylactic acid and polycaprolactone, with a mass ratio of 6:4 to 8:2; the core is a mixture of azodicarbonamide and citric acid, with a molar ratio of 1:0.2 to 0.4.

[0010] Preferably, the nanocellulose surface treatment agent is a 2-3 wt% nanocellulose dispersion, and the solvent is a mixture of ethanol and water in a volume ratio of 8:2-9:1.

[0011] The second aspect of the present invention provides a method for preparing the highly chemical-resistant TPO material according to the first aspect of the present invention, comprising the following steps: S1. Preparation of dynamic crosslinked matrix: premix polypropylene, styrene-ethylene / butylene-styrene block copolymer, and epoxidized cardanol, add furan end-capping agent and maleimide crosslinking agent, and form a dynamic crosslinked network by banburying; S2, biomimetic filler modification: calcium carbonate-silica nanoparticles were sequentially grafted with polydopamine and perfluorohexyl; S3, gradient structure co-extrusion molding: the base body of step S1 and the modified filler and microcapsules of step S2 are co-extruded to form a three-layer structure with the surface layer containing the modified filler and the inner layer containing the microcapsules; S4, in-situ foaming-crosslinking integration: triggering the microcapsules to release foaming gas and catalyze the crosslinking reaction in stages; S5. Surface biomimetic treatment: performing laser etching and nanocellulose sol impregnation on the co-extruded material to obtain the highly chemical-resistant TPO material.

[0012] Preferably, the preparation of the dynamic cross-linked matrix in step S1 includes: Premixing conditions: temperature 60-80°C, speed 200-300 rpm, time 5-10 minutes; Mixing conditions: temperature 140-150°C, speed 50-70 rpm, time 12-18 minutes; The residual amount of maleimide groups is controlled to be 0.05-0.1 wt%.

[0013] Preferably, the biomimetic filler modification in step S2 comprises the following steps: Polydopamine grafting: disperse the nanoparticles in a dopamine hydrochloride solution with a pH of 8.0 to 9.0 and react at room temperature for 20 to 28 hours; perfluorohexyl grafting: immerse in a 0.5 to 1.5% perfluorosilane ethanol solution at a temperature of 70 to 90°C and react for 4 to 8 hours.

[0014] Preferably, the gradient structure co-extrusion molding in step S3 includes the following steps: Thickness of three-layer flow channel: surface layer 80-120μm, middle layer 50-80μm, inner layer 200-300μm; Die head temperature layer control: surface layer 165 ~ 175 ℃, middle layer 160 ~ 170 ℃, inner layer 170 ~ 180 ℃.

[0015] Preferably, the in-situ foaming-crosslinking integration in step S4 includes: Foaming trigger zone: temperature 160-180°C, residence time 30-60 seconds; Cross-linking reaction zone: temperature 140-150°C, residence time 20-40 seconds; Screw speed is 20~40rpm.

[0016] Preferably, the surface biomimetic treatment in step S5 includes: Laser etching parameters: wavelength 350-360 nm, energy density 0.8-1.2 J / cm 2 , line width 2~5μm; Dipping and pulling speed: 10-15 mm / s, drying temperature 70-90°C, time 8-12 minutes.

[0017] The present invention provides a highly chemical-resistant TPO material and a preparation method thereof. It has the following beneficial effects: 1. Through the synergistic effect of the dynamic cross-linking network and the surface modification of the fluorocarbon chain, the present invention releases local stress through the reversible cross-linking bond through the fracture-reconstruction mechanism when the material comes into contact with acids, alkalis and organic solvents, thereby inhibiting the propagation of microcracks. The dense fluorocarbon layer on the surface forms a chemically inert barrier, significantly reducing the penetration rate of corrosive media, and ensuring the structural stability and long-term durability of the material in complex chemical environments.

[0018] 2. The present invention is based on a multi-scale design of gradient foaming structure and dynamic cross-linking network. The high modulus area on the surface of the material provides rigid support, and the porous structure in the core disperses impact energy. Combined with the reversible fracture characteristics of the cross-linking bonds, it achieves a balance between tear resistance, bending stiffness and impact toughness, breaking through the technical problem that traditional materials are difficult to achieve both lightweight and high strength.

[0019] 3. The present invention forms a micro-nano multi-level rough structure through laser etching, combined with a nanocellulose coating with directional bonding at the polydopamine interface, to construct a composite hydrophobic system with low surface energy chemical modification and high roughness physical structure, giving the material surface long-term self-cleaning ability, effectively blocking liquid infiltration and pollutant adhesion, and reducing surface maintenance requirements.

[0020] 4. This invention utilizes a dynamic crosslinking network that dissociates at high temperatures to restore melt fluidity, enabling high-precision molding of complex structures. Upon cooling, the crosslinking network reconstructs in situ, ensuring dimensional stability of the finished product. This reversible property enables the material to be recycled and reprocessed multiple times, overcoming the technical limitations of traditional thermoset materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a flow chart of the preparation method of the present invention. DETAILED DESCRIPTION

[0022] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0023] This invention relates to a highly chemical-resistant TPO material. Through multi-component synergy and process innovation, it achieves high stability and functionality in complex chemical environments. The following describes the component composition and synergy mechanism: Please see the attached Figure 1 The TPO material of the present invention is based on polypropylene (PP) and styrene-ethylene / butylene-styrene block copolymer (SEBS), and constructs a multi-scale functional structure by introducing a dynamic cross-linking network, biomimetic modified fillers, thermosensitive microcapsules and surface treatment agents.

[0024] Dynamic crosslinking network: The furan endcapping agent and the maleimide crosslinker form reversible covalent bonds during the mixing process, imparting self-healing capabilities and melt fluidity to the material. The Diels-Alder reaction between the furan groups and the maleimide reversibly dissociates at processing temperatures, enabling real-time reconstruction of the dynamic crosslinking network and resolving the processing difficulties of traditional crosslinking systems.

[0025] Biomimetic filler modification: A calcium carbonate-silica core-shell structure is gradiently grafted with polydopamine and perfluorohexyl groups to form a hydrophobic-adhesive dual-functional interface. The polydopamine layer strengthens the interfacial bond between the filler and the substrate, while the perfluorohexyl chains, through their low surface energy, block the penetration of chemical solvents. The core-shell structure also disperses stress concentration, enhancing the material's resistance to swelling.

[0026] Thermosensitive microcapsules: The polylactic acid / polycaprolactone copolymer shell controls the release sequence of the core foaming agent through temperature response. Citric acid acts as a catalyst to accelerate the decomposition of azodicarbonamide, achieving a synergistic triggering of the foaming and cross-linking reactions. The gradient distribution of the microcapsules creates an inner foaming structure, reducing material density, while the densified surface inhibits the intrusion of chemical media.

[0027] Surface bionic treatment: Laser etching constructs a micron-scale groove structure on the material surface to increase the specific surface area; nanocellulose sol forms a bionic hydrophobic layer through directional impregnation. The two work together to achieve dual protection of surface anti-pollution and chemical corrosion resistance.

[0028] The present invention provides a method for preparing the above-mentioned highly chemical-resistant TPO material, comprising the following steps: S1. Preparation of dynamic cross-linked matrix Low-temperature mixing (60-80°C) during the premixing stage prevents phase separation of the styrene-ethylene / butylene-styrene block copolymer. The dynamic crosslinking network is formed during the mixing process, relying on the reversible reaction of maleimide and furan groups. Coordinated control of the mixing temperature (140-150°C) and the mixing speed (50-70 rpm) ensures a balance between crosslink density and melt flow. Residual maleimide groups (0.05-0.1 wt%) provide active sites for subsequent in-situ crosslinking.

[0029] S2. Bionic filler modification The polydopamine grafted layer forms a uniform adhesion layer through oxidative self-polymerization under alkaline conditions, and its catechol structure is bonded to the substrate through hydrogen bonds; perfluorosilane is hydrolyzed and condensed in an ethanol solution, and the grafting temperature (70-90°C) and reaction time (4-8 hours) regulate the orientation density of the fluorocarbon chain to form a low surface energy barrier.

[0030] S3, gradient structure co-extrusion molding The three-layer flow channel thickness design (surface layer 80-120μm, middle layer 50-80μm, inner layer 200-300μm) combined with the die head temperature layer control (surface layer 165-175℃, middle layer 160-170℃, inner layer 170-180℃) allows the modified filler to be preferentially enriched in the surface layer to form a dense barrier layer. The microcapsules are pre-dispersed in the high-temperature area of the inner layer, providing uniform nucleation points for foaming.

[0031] S4, in-situ foaming-crosslinking integration In the foaming trigger zone (160-180°C), heat conduction melts the microcapsule shell, releasing azodicarbonamide to decompose and produce nitrogen. Simultaneously, citric acid catalyzes the cross-linking reaction of residual maleimide groups. The low temperature of the cross-linking reaction zone (140-150°C) stabilizes the cell structure, while the screw speed (20-40 rpm) controls the gas diffusion rate and prevents cell collapse.

[0032] S5. Surface biomimetic treatment Ultraviolet laser (350-360nm) etching selectively removes surface materials through photothermal effect to form a directional microgroove structure; nanocellulose sol is directionally attached to the groove under the control of pulling speed (10-15mm / s). During the drying process, cellulose hydrogen bonds are reorganized to form a dense hydrophobic layer. The ethanol / water mixed solvent ratio (8:2-9:1) optimizes the sol penetration depth.

[0033] In order to better understand the present invention, the present invention is described in detail below with reference to specific embodiments.

[0034] Example 1: Components and ratio (by weight) Polypropylene (PP): 60 parts Styrene-ethylene / butylene-styrene block copolymer (SEBS): 40 parts Furan blocking agent: 0.5 parts Maleimide crosslinker: 0.3 parts Modified shell powder: 5 parts (calcium carbonate-silicon dioxide core-shell structure, grafted polydopamine + perfluorohexyl, fluorocarbon chain grafting rate 6%) Epoxidized cardanol (ECP): 10 parts Thermosensitive microcapsules: 3 parts (shell polylactic acid / polycaprolactone mass ratio 7:3, core azodicarbonamide / citric acid molar ratio 1:0.3) Nanocellulose surface treatment agent: 1.0 part (2.5 wt% dispersion, ethanol / water volume ratio 8.5:1.5).

[0035] Preparation steps S1. Dynamic crosslinking matrix preparation premix: polypropylene, styrene-ethylene / butylene-styrene block copolymer, and epoxidized cardanol were mixed at 70°C and 250 rpm for 8 minutes; Banburying: Add furan end-capping agent and maleimide cross-linking agent, and banburying for 15 minutes at 145° C. and 60 rpm. The residual maleimide content is 0.08 wt%.

[0036] S2. Bionic filler modification Polydopamine grafting: Calcium carbonate-silica nanoparticles were dispersed in dopamine hydrochloride solution at pH 8.5 and reacted at room temperature for 24 hours; Perfluorohexyl grafting: Immerse in 1.0% perfluorosilane ethanol solution and react at 80°C for 6 hours.

[0037] S3, gradient structure co-extrusion molding Co-extrusion die settings: surface layer thickness 100 μm (temperature 170°C), middle layer 60 μm (temperature 165°C), inner layer 250 μm (temperature 175°C).

[0038] S4, in-situ foaming-crosslinking integration Foaming trigger zone: 170℃ for 45 seconds; Cross-linking reaction zone: 145°C for 30 seconds; The screw speed is 30 rpm.

[0039] S5. Surface biomimetic treatment Laser etching: wavelength 355nm, energy density 1.0J / cm 2 , line width 3μm; Dipping and pulling: 12 mm / s, drying temperature 80°C, time 10 minutes.

[0040] Example 2: Components and ratio (by weight) Polypropylene (PP): 58 parts Styrene-ethylene / butylene-styrene block copolymer: 42 parts Furan blocking agent: 0.55 parts Maleimide crosslinker: 0.25 parts Modified shell powder: 4.5 parts (fluorocarbon chain grafting rate 5.5%) Epoxidized cardanol: 9 parts Thermosensitive microcapsules: 2.5 parts (shell polylactic acid / polycaprolactone mass ratio 6.5:3.5, core azodicarbonamide / citric acid molar ratio 1:0.25) Nanocellulose surface treatment agent: 0.8 parts (2.8 wt% dispersion, ethanol / water volume ratio 8.2:1.8).

[0041] Preparation steps S1. Preparation of dynamic cross-linked matrix Premixing: 65°C, 280 rpm for 7 minutes; Banburying: 142° C., 55 rpm for 14 minutes, the residual maleimide content was 0.07 wt%.

[0042] S2. Bionic filler modification Polydopamine grafting: pH 8.2, reaction time 22 hours; Perfluorohexyl grafting: 0.8% perfluorosilane solution, reaction at 75°C for 5 hours.

[0043] S3, gradient structure co-extrusion molding co-extrusion die head: surface layer 90μm (168℃), middle layer 55μm (162℃), inner layer 220μm (172℃).

[0044] S4, in-situ foaming-crosslinking integration Foaming trigger zone: 165℃ for 35 seconds; Cross-linking reaction zone: 142°C for 25 seconds; The screw speed is 25 rpm.

[0045] S5. Surface biomimetic treatment Laser etching: energy density 0.9J / cm 2 , line width 2.5μm; Dipping and pulling: 11 mm / s, drying temperature 75°C, time 9 minutes.

[0046] Example 3: Components and ratio (by weight) Polypropylene (PP): 63 parts Styrene-ethylene / butylene-styrene block copolymer: 37 parts Furan blocking agent: 0.45 parts Maleimide crosslinker: 0.35 parts Modified shell powder: 5.5 parts (fluorocarbon chain grafting rate 7.5%) Epoxidized cardanol: 11 parts Thermosensitive microcapsules: 3.5 parts (shell polylactic acid / polycaprolactone mass ratio 7.5:2.5, core azodicarbonamide / citric acid molar ratio 1:0.35) Nanocellulose surface treatment agent: 1.2 parts (2.2 wt% dispersion, ethanol / water volume ratio 8.8:1.2) Preparation steps Dynamic cross-linking matrix preparation Premixing: 75°C, 220 rpm for 6 minutes; Banburying: 148° C., 65 rpm for 16 minutes, the residual maleimide content was 0.09 wt%.

[0047] Bionic filler modification Polydopamine grafting: pH 8.8, reaction time 26 hours; Perfluorohexyl grafting: 1.2% perfluorosilane solution, reaction at 85°C for 7 hours.

[0048] Gradient structure co-extrusion molding co-extrusion die head: surface layer 110μm (173℃), middle layer 70μm (168℃), inner layer 280μm (178℃).

[0049] In-situ foaming-crosslinking integration Foaming trigger zone: 175℃ for 50 seconds; Cross-linking reaction zone: 148°C for 35 seconds; The screw speed is 35 rpm.

[0050] Surface biomimetic treatment Laser etching: energy density 1.1J / cm 2 , line width 4μm; Dipping and pulling: 14 mm / s, drying temperature 85°C, time 11 minutes.

[0051] Comparative Example 1: Compared with Example 1, the difference is that the shell powder is not modified by fluorocarbon grafting (only the calcium carbonate-silica core-shell structure is retained, and polydopamine and perfluorohexyl are not grafted), and the other components and preparation steps are the same.

[0052] Comparative Example 2: Compared with Example 1, the difference is that the temperature layering control in the gradient co-extrusion molding is cancelled (the temperature of each layer of the die is unified at 170° C.), and the other components and preparation steps are the same.

[0053] Comparative Example 3: Compared with Example 1, the difference is that the heat-sensitive microcapsules are replaced by ordinary azodicarbonamide foaming agent (uncoated azodicarbonamide is directly added without citric acid and shell structure), and the other components and preparation steps are the same.

[0054] Comparative Example 4: Compared with Example 2, the difference is that no furan end-capping agent is added in the preparation of the dynamic cross-linking matrix (only maleimide cross-linking agent is used), and the other components and preparation steps are the same.

[0055] Comparative Example 5: Compared with Example 2, the difference is that the laser etching step is omitted in the surface biomimetic treatment (only nanocellulose sol impregnation is performed), and the other components and preparation steps are the same.

[0056] Comparative Example 6: Compared with Example 3, the difference is that the staged temperature control is cancelled in the in-situ foaming-crosslinking integration (the temperature of the foaming triggering zone and the crosslinking reaction zone are both 160° C.), and the other components and preparation steps are the same.

[0057] Comparative Example 7: Compared with Example 3, the difference is that: no polydopamine layer is grafted in the bionic filler modification (perfluorohexyl is directly grafted), and the other components and preparation steps are the same.

[0058] Test Example 1: Chemical resistance test Experimental procedures Sample preparation: The TPO materials of Examples 1-3 and Comparative Examples 1, 2, and 5 were cut into pieces of 20×20×2 mm. 3 Standard samples, 3 parallel samples per group.

[0059] The sample surface was wiped with anhydrous ethanol and then dried in vacuum at 60 °C for 4 h.

[0060] Soaking treatment: Acidic environment: Immerse the sample in 10% sulfuric acid solution (constant temperature 60°C) for 48 hours.

[0061] Organic solvent environment: immerse the sample in xylene (constant temperature of 60°C) for 48 hours.

[0062] Performance testing: Mass change rate: After soaking, remove the sample, rinse with deionized water and dry, and calculate the mass change rate:

[0063] Surface swelling degree: Use a digital micrometer to measure the thickness change and calculate the swelling rate:

[0064] The experimental results are shown in Table 1: Table 1 Summary of chemical resistance test data From the experimental results in Table 1, we can get: This experiment verified the synergistic protection mechanism of multi-level functionalized structures in material design by comparing the chemical corrosion resistance of different samples. The fluorocarbon chain grafting modification forms a chemically inert barrier at the filler-matrix interface through the low surface energy characteristics of perfluorohexyl, significantly inhibiting the penetration of acidic media and organic solvents. In Comparative Example 1, the mass change rate of the sample without grafted fluorocarbon chains after immersion in xylene was as high as 15.4%, while the mass change rate of the example group was controlled at 5.3-6.2% due to the hydrophobic interface effect, indicating that the directional arrangement of the perfluorochain effectively blocked the diffusion and erosion of small molecule solvents.

[0065] Gradient structure co-extrusion achieves precise distribution of the dense barrier layer on the surface and the foamed structure on the inner layer through temperature stratification. In Comparative Example 2, uniform die temperature resulted in a loss of barrier function in the surface layer, allowing sulfuric acid solution to penetrate the inner layer, causing the foamed structure to swell (swelling rate of 7.5%). In the Example group, the three-dimensional protection of the gradient structure reduced the swelling rate to 2.9-3.8%. This design, through a spatial zoning strategy, balances material lightweighting with corrosion resistance.

[0066] The synergistic effect of surface laser etching and directional attachment of nanocellulose further enhances the surface protection performance of the material. In Comparative Example 5, the sample that relies solely on nanocellulose impregnation cannot guide the directional filling of the sol due to the lack of a micron-scale groove structure, and the surface hydrophobic layer has insufficient continuity, resulting in a xylene swelling rate (14.5%) that is significantly higher than that of the embodiment group (7.9-9.1%). The bionic microstructure constructed by laser etching not only increases the specific surface area, but also promotes the in-situ self-assembly of nanocellulose through the capillary effect to form a dense composite protective layer. From the three dimensions of interfacial hydrophobic modification, structural gradient design and surface functionalization, the core mechanism of the present invention to improve chemical resistance is revealed, which is in sharp contrast to the performance defects of the comparative example, verifying the innovation and necessity of the technical solution.

[0067] Test Example 2: Foaming structure uniformity test experiment Experimental procedures Sample preparation: The TPO materials of Examples 1-3 and Comparative Examples 3 and 6 were cut into pieces of 10×10×5 mm. 3 Cube specimens, 3 parallel samples per group.

[0068] The sample surface is polished to avoid interference from surface roughness during CT scanning.

[0069] Micro-CT scan: High-resolution micro-CT (resolution 1 μm) was used to perform three-dimensional imaging of the interior of the sample with a scanning voltage of 80 kV and a current of 150 μA.

[0070] After reconstructing the 3D model, the central area (5×5×2mm 3 ) for pore analysis.

[0071] Data Analysis: Cell diameter: The average value of the major and minor axes of all cells in the measurement area was used to calculate the average diameter (μm).

[0072] Coefficient of variation (CV value): Evaluates the degree of dispersion of cell diameter distribution. The calculation formula is: Range: the difference between the maximum cell diameter and the minimum cell diameter (μm).

[0073] The experimental results are shown in Table 2: Table 2 Summary of foaming structure uniformity test data (micro CT scan) Group Average diameter (μm) CV value (%) Range (μm) <![CDATA[Cell density (cells / mm 3 )]]> Example 1 86.3 18.7 142 2350 Example 2 91.5 20.4 158 2180 Example 3 82.7 17.9 136 2470 Comparative Example 3 124.6 38.2 283 1650 Comparative Example 6 102.8 29.5 214 1920 From the experimental results in Table 2, we can get: This experiment revealed the key role of the time-controlled release function of thermosensitive microcapsules and the staged temperature process in the uniformity of the pore structure through micro-CT analysis. The polylactic acid / polycaprolactone copolymer in the microcapsule shell accurately controls the release timing of the core foaming agent through its thermal response characteristics, avoiding the problem of bubble merging caused by premature decomposition of the uncoated foaming agent (Comparative Example 3) at the beginning of processing. The coefficient of variation of the pore diameter of the example group (17.9-20.4%) is significantly lower than that of Comparative Example 3 (38.2%), verifying the key contribution of the shell material to the sustained release of gas. Its mass ratio design (6:4-8:2) achieves dynamic synchronization of gas release and the melting state of the matrix by adjusting the melting temperature of the shell to match the processing conditions.

[0074] The staged temperature triggering process uses the temperature difference between the foaming zone and the cross-linking zone (ΔT = 15-35°C) to ensure that the foaming gas is fully diffused and the cross-linking reaction is immediately started to stabilize the cell structure. In Comparative Example 6, the temperature homogenization caused the cell to collapse (the cell density was reduced to 1920 / mm 3 , Example group 2180-2470 pieces / mm 3 ), indicating that a staged temperature strategy can circumvent the conflict between gas escape and crosslinking lag. The synergistic decomposition of azodicarbonamide and citric acid catalysis further optimizes the gas release rate, keeping the cell size range within 136-158 μm (compared to the range of 283 μm in Comparative Example 3).

[0075] The synergy of the gradient distribution of microcapsules and the dynamic cross-linking network provides a double guarantee for the uniformity of the pores. The preferential dispersion of microcapsules in the high-temperature zone of the inner layer increases the density of nucleation points, while the dynamic cross-linking network inhibits the merging of pores by regulating the melt viscosity. The higher ECP content (11 parts) in Example 3 enhances the cross-linking density and further reduces the average pore diameter to 82.7μm, reflecting the synergistic optimization of components and processes. From the three aspects of microcapsule structure design, staged process control and component synergy, the formation mechanism of pore uniformity is elucidated, which is in direct contrast to the performance defects of the comparative example, verifying the innovative breakthrough of the present invention in lightweighting and structural stability.

[0076] Test Example 3: Dynamic cross-linking effect test experiment Experimental procedures Sample preparation: The TPO materials of Examples 1-3 and Comparative Example 4 were crushed into particles with a diameter of 2-3 mm, with 3 parallel samples in each group.

[0077] The samples were preheated at 120 °C for 10 min to eliminate residual stress.

[0078] Dynamic rheological testing: Use rotational rheometer, test conditions: Temperature: 170°C (simulated processing temperature) Frequency scanning range: 0.1-100rad / s, strain amplitude 1% Record the complex viscosity (η * ) versus frequency curve and calculate the zero shear viscosity (η°).

[0079] Processing cycle test: After injection molding the sample at 170°C, it was crushed and re-injected to test the viscosity change rate after the secondary processing:

[0080] The experimental results are shown in Table 3: Table 3 Summary of dynamic crosslinking effect test data (dynamic rheological test) From the experimental results in Table 3, we can get: This experiment revealed the core role of the reversible properties of the dynamic cross-linked network in the processing performance of the material through dynamic rheological analysis. The reversible reaction of the furan end-capping agent and the maleimide cross-linking agent triggered the dissociation of the Diels-Alder bond during high-temperature processing (170°C), causing the cross-linked network to temporarily break and the melt viscosity to decrease significantly (the viscosity of the embodiment group decreased by 10.3-15.2% in the secondary processing). In Comparative Example 4, no furan end-capping agent was introduced, the cross-linked network was irreversible, the molecular chain entanglement intensified after secondary processing, and the viscosity increased by 25.0%, verifying the key regulatory ability of dynamic covalent bonds on processing fluidity.

[0081] The real-time reconstruction characteristics of the dynamic network are further reflected by the change in storage modulus. The storage modulus of the embodiment group decreased by 19.8-28.1% after secondary processing, indicating that the dissociated cross-linking bonds were partially recombined during the cooling process to form an adaptive network structure. The storage modulus of comparative example 4 only decreased by 5.6%, indicating that the rigid network of the traditional cross-linking system cannot be dynamically reconstructed, resulting in loss of material toughness and deterioration of processability. This reversible cross-linking mechanism not only solves the problem of traditional thermosetting materials being difficult to recycle, but also optimizes the feasibility of complex molding processes through self-regulation of melt viscosity.

[0082] Precise control of the residual amount of maleimide crosslinker ensures the stability of the dynamic network. The higher amount of maleimide (0.35 parts) in Example 3 increases the active site density, so that part of the crosslinked skeleton is retained after dissociation, inhibiting cell collapse (see Experiment 2) and achieving a higher viscosity reduction (-15.2%). This design balances the contradiction between crosslinking density and dynamic reversibility, and reflects the improvement of the overall performance of the material through the coordinated optimization of component ratios and process parameters.

[0083] The above summary illustrates the dual benefits of dynamic cross-linking design on processing fluidity and structural stability from three aspects: reversible cross-linking mechanism, network reconstruction capability, and component synergistic effect. This is in sharp contrast to the defects of Comparative Example 4, highlighting the innovative breakthroughs of the present invention in material recyclability and processing efficiency.

[0084] Test Example 4: Surface hydrophobicity test experiment Experimental procedures Sample preparation: The TPO materials of Examples 1-3 and Comparative Examples 5 and 7 were cut into pieces of 30×30×1 mm. 2 Thin slice specimens, 3 parallel samples per group.

[0085] The samples were ultrasonically cleaned with acetone and deionized water for 10 minutes, and dried with nitrogen.

[0086] Static contact angle test: Using a contact angle meter, 5 μL of deionized water was added, the droplet morphology was recorded, and the contact angle was calculated (the average value of three measurements was taken).

[0087] Roll angle test: The sample was fixed on a tilting platform, the tilt angle was increased at a rate of 0.5° / s, and the critical angle at which the water droplet began to roll was recorded.

[0088] Surface morphology analysis: The micron-scale groove structure and nanocellulose distribution after laser etching were observed by scanning electron microscopy (SEM).

[0089] The experimental results are shown in Table 4: Table 4 Surface hydrophobicity test data From the experimental results in Table 4, we can get: This experiment revealed the synergistic mechanism of laser etching microstructure, polydopamine interface layer and fluorocarbon chain chemical modification through surface hydrophobicity testing and morphology analysis. The micron-scale groove structure constructed by laser etching increases the surface roughness (Ra=1.72-2.03μm in the embodiment group) through physical morphology regulation, providing a structural basis for superhydrophobicity. The unetched sample in Comparative Example 5 has a smooth surface (Ra=0.34μm), resulting in a contact angle of only 122.4°, while the contact angle of the embodiment group reaches 153.6-161.8°, verifying the key role of microgrooves in forming Cassie-Baxter liquid films by trapping air. The optimized design of groove depth and spacing (groove depth of Example 3 ~15μm) further reduces the adhesion of water droplets to 10.9μN, achieving efficient repulsion of low surface energy liquids.

[0090] The biomimetic adhesion properties of the polydopamine interface layer solve the problem of nanocellulose dispersion on hydrophobic surfaces. Although the sample without polydopamine grafted on it was laser etched in Comparative Example 7, the nanocellulose aggregated in the grooves (SEM showed a coverage rate of <40%), and the contact angle was only 138.2°. The embodiment group anchored the nanocellulose through the catechol group of polydopamine to form a continuous and directional nano-scale coating (coverage rate>85%), which reduced the rolling angle to 3.8-5.1°. This multi-level structure (micron grooves + nanofibers) significantly improved the autonomous rolling efficiency of droplets through the synergistic effect of capillary forces.

[0091] The synergistic effect of the chemical modification and physical structure of the fluorocarbon chain further enhances the hydrophobic stability. The high-density grafting of perfluorohexyl groups in Example 3 (grafting rate 7.5%) reduces the surface energy to 12.3 mN / m and the contact angle reaches 161.8°. In Example 1-2, the molecular chain mobility of the dynamic cross-linking network ensures that the fluorocarbon chains migrate and enrich to the surface during processing, maintaining long-term hydrophobicity. The laser-etched groove structure also provides a directional arrangement template for the fluorocarbon chains, forming a composite protective system of low surface energy chemical barriers and high roughness physical barriers, which is in sharp contrast to the performance defects of the comparative group.

[0092] The above summary explains the formation mechanism of superhydrophobic surface from three aspects: physical structure design, bionic interface optimization and chemical-physical synergy, reflecting the innovative breakthrough of the present invention in surface functionalization and durability.

[0093] Test Example 5: Foaming-crosslinking synergy test experiment Experimental procedures Sample preparation: The TPO materials of Examples 1-3 and Comparative Examples 3 and 6 were cut into pieces of 10×10×5 mm. 3 Cube specimens, 3 parallel samples per group.

[0094] The samples were vacuum dried at 80 °C for 6 h to remove residual moisture.

[0095] DSC simultaneous thermal analysis: Differential Scanning Calorimetry (DSC) was used under the following test conditions: Nitrogen atmosphere, heating rate 10℃ / min, temperature range 50-250℃.

[0096] The onset temperature and peak area overlap of the foaming gas release peak (azodicarbonamide decomposition) and the crosslinking reaction peak (ECP crosslinking) were analyzed.

[0097] Foaming ratio and collapse rate test: Foaming ratio: calculated by density method (density after foaming / density of raw material); Collapse rate: Place the foamed sample at 120℃ for 2 hours and measure the thickness change:

[0098] The experimental results are shown in Table 5: Table 5 Foaming-crosslinking synergy test data (DSC and foaming stability analysis) From the experimental results in Table 5, we can get: This experiment reveals the core regulatory mechanism of the time-controlled release of microcapsules and the staged temperature process on the synergy of foaming and cross-linking through thermodynamic analysis and foaming stability testing. The polylactic acid / polycaprolactone copolymer of the microcapsule shell accurately delays the decomposition of the foaming agent through thermal response characteristics, ensuring that the foaming reaction is started after the matrix is fully melted. In Comparative Example 3, the uncoated azodicarbonamide decomposes in advance at 138°C (the trigger temperature of the embodiment group is 155-162°C), causing the gas to escape before the cross-linked network is formed, and the collapse rate is as high as 31.8%. The embodiment group uses gradient melting of the microcapsule shell (polylactic acid is softened first) to make the overlap between the foaming peak and the cross-linking peak reach 89.7-95.2%, and the pore wall is instantly solidified by the dynamic cross-linked network, and the collapse rate is controlled at 6.7-9.6%.

[0099] The ΔT design of the staged temperature process (the temperature difference between the foaming zone and the cross-linking zone is 15-35°C) provides a thermodynamic driving force for the spatiotemporal separation of foaming and cross-linking. In Comparative Example 6, temperature homogenization causes foaming and cross-linking to be triggered simultaneously (159°C). The cell wall cannot resist the gas expansion pressure due to the hysteresis of cross-linking, and the collapse rate rises to 18.4%. The embodiment group, through a staged temperature strategy, quickly activates the cross-linking reaction (cross-linking zone 175-180°C) after the foaming gas is fully diffused (foaming zone 160-165°C), combined with the catalytic effect of citric acid, to achieve efficient and stable cellular structure (foaming ratio 6.8-7.5 times).

[0100] The reversible properties of the dynamic cross-linked network further enhance the adaptability of the foaming structure. The higher ECP content (11 parts) in Example 3 reduces the cross-linking trigger temperature to 170°C by increasing the cross-linking point density, and the peak overlap is increased to 95.2%. The pore walls are quickly reconstructed after gas release, inhibiting collapse and increasing the foaming ratio (7.5 times). The synergistic effect of the gradient distribution of microcapsules and the dynamic network achieves a "self-buffering" effect in the foaming process, which is in sharp contrast to the performance defects of the comparative group, verifying the dual breakthrough of the present invention in lightweighting and structural stability.

[0101] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A highly chemical-resistant TPO material, characterized in that: The composition includes the following parts by weight: 55-65 parts of polypropylene; 35-45 parts of styrene-ethylene / butylene-styrene block copolymer; 0.4-0.6 parts of furan capping agent; 0.2-0.4 parts of maleimide crosslinking agent; 4-6 parts of modified shell powder; 8-12 parts of epoxidized cardanol; 2 to 4 parts of thermosensitive microcapsules, wherein the thermosensitive microcapsules include a shell and a core; 0.5-1.5 parts of nanocellulose surface treatment agent.

2. A highly chemical-resistant TPO material according to claim 1, characterized in that: The modified shell powder is a calcium carbonate-silicon dioxide core-shell structure, with polydopamine and perfluorohexyl grafted on the surface in sequence, and the fluorocarbon chain grafting rate is 5-8%.

3. The highly chemical-resistant TPO material according to claim 1, characterized in that: The shell layer of the thermosensitive microcapsule is a copolymer of polylactic acid and polycaprolactone, with a mass ratio of 6:4 to 8:2; the core is a mixture of azodicarbonamide and citric acid, with a molar ratio of 1:0.2 to 0.

4.

4. A highly chemical-resistant TPO material and a preparation method thereof according to claim 1, characterized in that: The nanocellulose surface treatment agent is a 2-3 wt% nanocellulose dispersion, and the solvent is a mixture of ethanol and water in a volume ratio of 8:2-9:

1.

5. A method for preparing the highly chemical-resistant TPO material according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1. Preparation of dynamic crosslinked matrix: premix polypropylene, styrene-ethylene / butylene-styrene block copolymer, and epoxidized cardanol, add furan end-capping agent and maleimide crosslinking agent, and form a dynamic crosslinked network by banburying; S2, biomimetic filler modification: calcium carbonate-silica nanoparticles were sequentially grafted with polydopamine and perfluorohexyl; S3, gradient structure co-extrusion molding: the base body of step S1 and the modified filler and microcapsules of step S2 are co-extruded to form a three-layer structure with the surface layer containing the modified filler and the inner layer containing the microcapsules; S4, in-situ foaming-crosslinking integration: triggering the microcapsules to release foaming gas and catalyze the crosslinking reaction in stages; S5. Surface biomimetic treatment: performing laser etching and nanocellulose sol impregnation on the co-extruded material to obtain the highly chemical-resistant TPO material.

6. The method for preparing a highly chemical-resistant TPO material according to claim 5, characterized in that: The preparation of the dynamic cross-linked matrix in step S1 includes: Premixing conditions: temperature 60-80°C, speed 200-300 rpm, time 5-10 minutes; Mixing conditions: temperature 140-150°C, speed 50-70 rpm, time 12-18 minutes; The residual amount of maleimide groups is controlled to be 0.05-0.1 wt%.

7. The method for preparing a highly chemical-resistant TPO material according to claim 1, characterized in that: The biomimetic filler modification in step S2 comprises the following steps: Polydopamine grafting: Disperse the nanoparticles in a dopamine hydrochloride solution with a pH of 8.0-9.0 and react at room temperature for 20-28 hours; Perfluorohexyl grafting: Immerse in 0.5-1.5% perfluorosilane ethanol solution at 70-90°C and react for 4-8 hours.

8. The method for preparing a highly chemical-resistant TPO material according to claim 1, characterized in that: The gradient structure co-extrusion molding in step S3 includes the following steps: Thickness of three-layer flow channel: surface layer 80-120μm, middle layer 50-80μm, inner layer 200-300μm; Die head temperature layer control: surface layer 165 ~ 175 ℃, middle layer 160 ~ 170 ℃, inner layer 170 ~ 180 ℃.

9. The method for preparing a highly chemical-resistant TPO material according to claim 1, characterized in that: The in-situ foaming-crosslinking integration in step S4 includes: Foaming trigger zone: temperature 160-180°C, residence time 30-60 seconds; Cross-linking reaction zone: temperature 140-150°C, residence time 20-40 seconds; Screw speed is 20~40rpm.

10. The method for preparing a highly chemical-resistant TPO material according to claim 1, characterized in that: The surface biomimetic treatment in step S5 includes: Laser etching parameters: wavelength 350-360nm, energy density 0.8-1.2J / cm², line width 2-5μm; Dipping and pulling speed: 10-15 mm / s, drying temperature 70-90°C, time 8-12 minutes.

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