Preparation method of elastic material for filling well lid gap

Abstract

The invention provides a preparation method of an elastic material for filling well lid gaps, which comprises the following steps: selecting bio-based polylactic acid and a thermoplastic elastomer as basic materials, combining a nano-carbon reinforced material, a siloxane compound, an ultraviolet light absorber, a heat stabilizer and an anti-corrosion additive, and adopting a green solvent and an environment-friendly process to prepare the elastic material for filling well lid gaps. The prepared well lid gap filling material has excellent elasticity, weather resistance, environmental protection property and multiple functions. The method not only solves the problems of poor weather resistance, insufficient environmental protection property and short service life of the material in the prior art, but also has good adaptability and market application prospect, and especially has excellent performance under extreme environmental conditions.

Description

Technical Field

[0001] This invention relates to the field of municipal road infrastructure technology, specifically to a method for preparing an elastic material for filling gaps in manhole covers. Background Technology

[0002] Manhole cover gap fillers play a crucial role in ensuring traffic safety, reducing noise, and extending the lifespan of infrastructure. Existing manhole cover gap fillers mainly include asphalt-rubber mixtures, polyurethane materials, and rubber / plastic composites, but they have significant shortcomings in practical applications. I. Limitations of Traditional Materials

[0003] Although asphalt-rubber mixtures possess a certain degree of elasticity, they are prone to hardening or cracking under extreme temperature conditions, leading to seal failure. At low temperatures, the material becomes brittle and cracks, accelerating moisture penetration and causing roadbed erosion; at high temperatures, the material softens and flows, creating an uneven road surface and increasing driving hazards.

[0004] Polyurethane materials have good initial abrasion resistance, but they will still age and harden after long-term exposure to outdoor environments. Ultraviolet radiation can cause molecular chain breakage, resulting in surface powdering, loss of elasticity, and an average service life of less than 3 years.

[0005] II. Shortcomings of Modified Materials

[0006] The rubber / plastic composites and nano-reinforced materials developed in recent years have improved compressive strength and temperature resistance to some extent, but systemic bottlenecks still exist:

[0007] Insufficient environmental adaptability: Rubber / plastic composites are prone to phase separation during temperature cycling, with the elastic modulus increasing by more than 300% below -20℃, resulting in loss of buffering function; Although nano-reinforced materials improve mechanical strength, the uneven dispersion of nanoparticles leads to stress concentration, making them prone to microcracks under repeated loading; Degradable materials degrade at an uncontrolled rate in humid and hot environments, with strength decreasing by more than 40% within 6 months.

[0008] Insufficient durability: Existing materials are prone to aging under ultraviolet light and oxidation, with obvious yellowing of polymers and degradation of cross-linked networks, low elastic recovery rate, and significant performance fluctuations in the temperature range of -30℃ to 70℃.

[0009] Insufficient environmental friendliness: Petroleum-based materials such as TPU have a degradation cycle of more than 100 years, and the use of benzene solvents leads to excessive VOC emissions.

[0010] Limited functionality: Existing filling materials mostly adopt a static cross-linking structure, lacking the ability to automatically adjust stiffness according to changes in temperature and humidity, and also lacking multi-functional integration such as anti-pollution and anti-slip properties.

[0011] Construction is challenging: thermosetting materials require long on-site curing times and have high molding shrinkage rates, which can easily lead to secondary cracking in the joints. Modified asphalt or TPE and TPU have improved processability through plasticizers, but low-temperature brittleness still exists, and the use of organotin stabilizers poses an ecotoxicity risk.

[0012] For example, patent CN110387115 A discloses a method for manufacturing a novel composite molding compound manhole cover. This method uses a molding compound paste layer (see figure 2 in the specification) as the adhesive medium between the manhole cover body and the base, serving as a gap-filling agent. This molding compound paste layer is primarily composed of 191 unsaturated polyester resin with added tert-butyl peroxide crosslinking agent. However, this manhole cover gap-filling material suffers from the following inherent defects: extreme temperature failure (the polyester resin's embrittlement temperature is -5℃, leading to a 62% decrease in peel strength at -10℃, and interface cracking in cold winters); thermal deformation at 70℃ causing the adhesive layer to flow; uncontrolled environmental aging (lacking UV-resistant components); and thermal expansion mismatch (the resin's coefficient of thermal expansion differs significantly from the concrete matrix, resulting in a 100% gap regeneration rate after temperature cycling).

[0013] Therefore, there is an urgent need to develop a new type of manhole cover gap filling material with a structural design that combines environmental friendliness, durability, functional integration, and engineering adaptability.

[0014] Therefore, this invention provides a method for preparing a novel elastic material for filling gaps in manhole covers. This material is based on renewable raw materials and can be degraded under industrial composting conditions; it maintains an elastic modulus fluctuation of less than 30% within a temperature range of -30℃ to 70℃; it can automatically adjust its stiffness according to ambient temperature and humidity, with an elastic modulus adjustment range of not less than 50%; it has high molding precision with an error of less than 1mm, and the on-site construction time does not exceed 30 minutes; it also integrates multiple functions such as UV resistance, corrosion resistance, and anti-slip properties, thereby significantly improving road safety and the lifespan of manhole cover infrastructure. Summary of the Invention

[0015] To address the shortcomings of existing technologies, this invention provides a method for preparing an elastic material for filling gaps in manhole covers, thereby solving the problems mentioned in the background section.

[0016] The technical solution of the present invention specifically includes the following steps:

[0017] S1. Raw material preparation: Bio-based polylactic acid (PLA) and thermoplastic elastomer (TPE) are used as base materials; nano-carbon materials are used as reinforcing materials; siloxane compounds are used to enhance the material's UV absorption capacity and antioxidant properties; UV absorbers, heat stabilizers and preservative additives are prepared; plant-derived alcohol ester solvents are selected;

[0018] S2. Blending and Dissolving: Bio-based polylactic acid and thermoplastic elastomer are dissolved in plant-derived alcohol ester solvent and mixed using a high-shear mixer until a homogeneous solution is obtained; nano-carbon materials and dynamic disulfide bond crosslinking agents are added to the polymer solution and dispersed using ultrasound; siloxane compounds are added, and the mixture is heated to 60-90°C and stirred for 30-60 min to allow the siloxane compounds to be uniformly dispersed in the base material to form a compatible phase;

[0019] S3. Functional adjustment: UV absorbers and heat stabilizers are added to the solution and heated and stirred to ensure uniform distribution; corrosion inhibitors are added to the solution to give the reinforcing material corrosion resistance.

[0020] S4. Molding and Curing: Pour the treated solution into a mold and hot-press it to obtain the size and shape suitable for the manhole cover gaps; place the molded material in a cooling device to cool to room temperature, so that it can solidify and maintain its elasticity and toughness;

[0021] S5. Functional coating: A polyurethane-based anti-slip coating containing nano-silica is applied to the surface of the molded material;

[0022] In step S1, the mass ratio of bio-based polylactic acid to thermoplastic elastomer is 4:6 to 5:5.

[0023] The nano-carbon material mentioned in step S1 is graphene with a particle size of 20-50 nm or carbon nanotubes with an aspect ratio of >1000. The amount of nano-carbon material added is 0.5-3 wt% of the total mass of PLA and TPE.

[0024] The siloxane compound mentioned in step S1 is a hydroxyl-functionalized organosilicon resin.

[0025] The ultraviolet absorber mentioned in step S1 is a stilbene compound, the heat stabilizer is a nitrogen heterocyclic compound, and the corrosion inhibitor is a phosphate or molybdate compound. The amount of ultraviolet absorber added is 1-3 wt% of the raw material, and the amount of heat stabilizer added is 0.5-2 wt% of the raw material.

[0026] The dynamic disulfide crosslinking agent mentioned in step S2 is 4,4'-dithiodimorpholine, and the addition amount is 0.5-1.5 phr; wherein, phr represents the mass fraction of crosslinking agent per 100 parts by mass of resin matrix, and the resin matrix is ​​the sum of bio-based polylactic acid and thermoplastic elastomer.

[0027] In step S2, the ultrasonic dispersion power is 800-1200W and the time is 10-20min; in step S4, the hot pressing temperature is 130-150℃, the pressure is 8-12 MPa, and the holding time is 3-5min.

[0028] The plant-derived alcohol ester solvent in step S1 is ethyl lactate.

[0029] This invention provides a method for preparing an elastic material for filling gaps in manhole covers, which has the following significant advantages:

[0030] 1. The material of this invention can maintain excellent flexibility and ductility in low-temperature environments, avoiding the problem of traditional materials being prone to brittleness under severe cold conditions, thus ensuring the reliability of its use.

[0031] 2. The material of this invention has excellent shape retention and creep resistance under high temperature conditions. It is not prone to permanent deformation during long-term use and can continuously maintain the sealing and limiting effect between the manhole cover and the manhole frame.

[0032] 3. This invention constructs a nano-silica-reinforced polyurethane anti-slip coating on the material surface and combines it with a dynamic cross-linking structure design, enabling the material to have stable high friction performance in both dry and wet environments, effectively improving safety during road use.

[0033] 4. The material of this invention has good UV aging resistance. Under long-term outdoor ultraviolet radiation and complex climatic conditions, it can still maintain mechanical properties and appearance stability, significantly extending its service life.

[0034] 5. By introducing heat stabilizers and siloxane modification systems, the materials of this invention exhibit excellent antioxidant properties, which can effectively delay material aging and performance degradation.

[0035] 6. The material of this invention has excellent water resistance and can maintain structural and performance stability even in long-term water contact environments without expansion, delamination or performance degradation, thus ensuring its long-term reliable application in municipal road environments. Attached Figure Description

[0036] Figure 1 This is a schematic diagram illustrating the application of the elastic material for filling gaps in manhole covers according to the present invention in municipal manhole covers. Detailed Implementation

[0037] To enable those skilled in the art to understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort should fall within the scope of protection of the present invention.

[0038] In embodiments of the present invention, such as Figure 1As shown, the elastic material used to fill the gaps in the manhole cover is placed in the annular gap between the manhole cover and the manhole frame. Specifically, the manhole cover has a circular structure in the center, and its outer edge fits into the inner edge of the manhole frame. The manhole frame is fixed at the manhole opening position on the municipal road or ground. Due to long-term use, a certain assembly gap exists between the manhole cover and the manhole frame, which is prone to problems such as abnormal noise, water leakage, or loosening. The elastic material provided by this invention is in the form of annular strips, with its outer diameter fitting against the inner edge of the manhole frame and its inner diameter fitting against the outer edge of the manhole cover, thereby filling the annular gap between the manhole cover and the manhole frame, achieving effective limiting, buffering, and sealing of the manhole cover.

[0039] Through the above structural arrangement, the elastic material of the present invention can be reliably embedded between the manhole cover and the frame without affecting the normal opening and closing of the manhole cover, maintaining a tight fit, thereby improving the stability and service life of the manhole cover operation.

[0040] The present invention will now be described in detail:

[0041] Example 1: This example provides a method for preparing an elastic material for filling gaps in manhole covers. The specific implementation method is as follows:

[0042] 1. Raw material preparation

[0043] Ingredient Category specific chemicals Dosage Bio-based polylactic acid (PLA) NatureWorks Ingeo 4032D 40 g Thermoplastic elastomers (TPE) Kraton G1652 60 g Nanocarbon materials XG Science Grade C100 Graphene Powder 2 g Siloxane compounds Gelest M-1540 3 g UV absorber 2,2'-Dihydroxy-4,4'-stilbene (Tinuvin 328, Ciba patented product) 1.2 g Heat stabilizer 1,3,5-Trimethyl-2,4,6-triazacyclohexane (TMH, CAS 545-92-0) 0.6 g Preservatives Sodium molybdate (Na2MoO4·2H2O) 0.6 g Plant-derived alcohol ester solvents Ethyl lactate (≥99%) 200 mL Crosslinking agent DTDM 1 g

[0044] Table 1

[0045] The PLA used is NatureWorks Ingeo 4032D, which is industrially compostable, has moderate mechanical properties, and can be processed at temperatures below 200℃. The TPE, Kraton G1652, is a styrene-isobutylene-styrene block copolymer, providing elasticity and low-temperature resistance. The nano-carbon material, XG Science C100 graphene powder with a particle size of 30 nm, is easily dispersed and enhances thermal conductivity, wear resistance, and strength. The siloxane compound, Gelest M-1540, is a hydroxyl-functionalized silicone resin that improves the material's UV resistance and oxidation resistance. The UV absorber, Tinuvin 328, is an industrial-grade stilbene compound that effectively absorbs UV-A / B band light. The heat stabilizer, TMH, is a nitrogen-based heterocyclic small-molecule heat stabilizer that inhibits polymer chain thermal degradation. The corrosion inhibitor, Na2MoO4·2H2O, provides salt spray resistance and corrosion protection and is an inorganic, environmentally friendly additive.

[0046] 2. Raw material dissolution and preliminary mixing

[0047] Add 40 g PLA and 60 g TPE to 200 mL of ethyl lactate solvent. Stir at 3000 rpm for 30 min using a high-shear mixer while heating the solution to 80°C to ensure complete dissolution of PLA and TPE, forming a homogeneous and transparent solution. Dissolve 1 g DTDM in 2 mL of ethyl lactate to obtain a homogeneous crosslinking agent solution. Add this crosslinking agent solution to the homogeneous and transparent solution and continue stirring at 80°C for 10 min to ensure uniform dispersion of the dynamic disulfide crosslinking agent in the PLA and TPE matrices.

[0048] 3. Dispersion of nano-carbon materials

[0049] Add 2 g of graphene powder to the solution from step 2. Use an ultrasonic disperser with a power of 1000 W and a pulse mode of 10 s on / 5 s off for 15 min to ensure that the graphene is fully dispersed and does not aggregate. Then use a stirrer to continue stirring for 10 min to maintain uniformity.

[0050] 4. Addition of siloxane compounds and functional additives

[0051] Add 3 g of Gelest M-1540 to the solution from step 3, heat to 85°C, and stir for 15 min to promote fusion with the base polymer; add 1.2 g of UV absorber Tinuvin 328, 0.6 g of heat stabilizer TMH, and 0.6 g of preservative additive Na2MoO4·2H2O respectively, and stir for 20 min to ensure uniform distribution.

[0052] 5. Molding and thermosetting curing

[0053] The homogeneous solution from step 4 is poured into a custom mold, the mold size of which matches the gap in the manhole cover. The mold dimensions are based on a standard municipal manhole cover gap: inner diameter 400mm, outer diameter 440mm, ring width 20mm, and depth 25mm, ensuring the filling material can completely fit the gap after molding. The material is then held in a hot press at 130℃ and 8 MPa for 5 minutes to fully mold and achieve the desired size and shape. After molding, it is allowed to cool naturally to room temperature, and the preliminary elastomer is removed, yielding the manhole cover gap filling material ready for subsequent functional processing.

[0054] 6. Functional coatings

[0055] Purchase commercially available nano-SiO2-reinforced polyurethane coatings and spray them onto the surface of the molded material obtained in step 5. Control the coating thickness to 0.5 mm to ensure sufficient anti-slip and wear-resistant properties without affecting the overall elastic recovery. After coating, allow it to stand at room temperature for 20 minutes to cure into a film, thus obtaining an elastic material for filling gaps in manhole covers with anti-slip properties.

[0056] Explanation of the principle of dynamic cross-linking design:

[0057] In this invention, DTDM (tetramethylthiuram disulfide) is dissolved and dispersed together with the PLA / TPE matrix during the blending stage, forming a dynamic cross-linked network containing disulfide bonds (–S–S–) during the subsequent hot pressing process. These disulfide bonds can undergo reversible breakage and recombination under certain temperature and humidity conditions: when the ambient temperature or humidity increases, some disulfide bonds break, reducing the cross-linking density and increasing the chain segment mobility, resulting in a decrease in elastic modulus and an increase in flexibility; when the ambient temperature or humidity decreases, the broken disulfide bonds recombine, restoring the cross-linking structure, increasing the cross-linking density, and enhancing the material's stiffness.

[0058] Through this dynamic reversible process, the overall elastic modulus of the material can be adaptively adjusted within the range of 0.1–1.5 MPa, enabling it to maintain suitable mechanical properties under different environmental conditions.

[0059] 7. Quality Inspection and Packaging

[0060] The finished product was tested for elasticity, compressive strength, UV aging resistance, oxidation resistance, water resistance, and high temperature resistance.

[0061] Low-temperature elongation at break test: The molded manhole cover gap filler material was cut into standard tensile specimens with dimensions of 50 mm in length, 10 mm in width, and 5 mm in thickness. At least three specimens were prepared for each test group to ensure repeatability of results. The specimens were placed in a low-temperature chamber and allowed to cool completely at -30°C for 30 minutes. Tensile testing was then performed using an Instron 5965 universal testing machine at a tensile rate of 50 mm / min. The tensile displacement at fracture was recorded, and the elongation at break was calculated to ensure that the material retains good elastic properties even at low temperatures. Elongation at break (%) = (Length of specimen after fracture - Original length) / Original length × 100%.

[0062] High-Temperature Compression Set Test: Cylindrical specimens with a diameter of 20 mm and a height of 10 mm were prepared from the manhole cover gap filler material. At least three specimens were prepared for each test group to ensure repeatability of the results. The specimens were preheated in a 70℃ constant temperature chamber for 30 min. Subsequently, a compression testing machine was used to apply 50% compressive strain to the specimens and hold for 30 min, then unloaded. After the specimens were placed at room temperature for 10 min to recover, the final height was measured and compared with the original height. The compression set rate was calculated to verify the material's shape retention ability under high-temperature conditions. Compression set rate (%) = (Original height - Recovered height) / Original height × 100%.

[0063] Dry / Wet Friction Coefficient Test: Cut the manhole cover gap filler material into rectangular sheet specimens, 50mm in length, 50mm in width, and 5mm in thickness. Ensure the specimen surface is flat, without obvious burrs or protrusions to guarantee uniform frictional contact. Prepare at least 3 specimens per group for repeated testing and statistical analysis. Place the manhole cover gap filler material specimen on a sliding friction coefficient tester, equipped with a standard steel ball with a diameter of 10mm as the friction body. Under dry friction conditions, maintain an ambient relative humidity of 20%, apply a vertical load of 5N to the specimen surface, and conduct the friction test at a constant sliding speed. Measure the frictional force and calculate the friction coefficient μ=F. 摩擦力 / F 垂直负荷 Under wet friction conditions, 0.2 mL / cm² of deionized water was first added to the sample surface, and then the above friction test was repeated to verify the anti-slip performance of the material.

[0064] Ultraviolet absorption performance test (tensile property retention rate after UV aging): A 50mm wide, 10mm thick manhole cover gap filling material sample was placed in a UV aging chamber. The UV lamp wavelength was 340nm, the light intensity was 0.76W / m², the temperature was 60℃, and the relative humidity was 50%RH. The sample was continuously irradiated for 500 hours. The tensile strength before and after aging was tested to evaluate the material's UV resistance.

[0065] Oxidation resistance test: A 50mm diameter, 10mm wide, and 5mm thick sample was placed in a 70℃ air aging chamber and aged continuously for 500 hours. The change in tensile strength of the sample before and after aging was measured to verify the material's oxidation resistance.

[0066] Water resistance: In the water resistance test, a 50mm sample with a width of 10mm and a thickness of 5mm was immersed in deionized water at 25℃ for 24 hours. After being taken out, it was allowed to equilibrate naturally for 30 minutes. The change in tensile strength of the sample before and after aging was then measured to verify the water resistance of the material.

[0067] The formulas for calculating the retention rates of the ultraviolet absorption performance test, antioxidant performance test, and water resistance performance test are as follows:

[0068] Retention rate (%) = F 老化后 / F 老化前 ×100%;

[0069] F 老化前 =Tensile strength before aging (MPa);

[0070] F 老化后 = Tensile strength after aging (MPa).

[0071] The measured performance results are shown in the table below:

[0072] Test Project Sample size Test conditions Measured value Low temperature elongation at break 50×10×5 mm -30℃, tensile rate 50mm / min 340% High temperature compression set φ20×10 mm 70℃, compress by 50%, hold for 30 minutes 9.2% dry friction coefficient 50×50×5 mm Relative humidity 20%, vertical load 5N 0.72 wet friction coefficient 50×50×5 mm Add 0.2 mL / cm² of deionized water dropwise, with a vertical load of 5 N. 0.68 UV absorption performance (tensile property retention rate after UV aging) 50×10×5 mm UV 340nm, 0.76W / m², 60℃, 500h 92% Antioxidant properties 50×10×5 mm 70℃ air aging, 500h 89% Water resistance 50×10×5 mm Soak in deionized water at 25℃ for 24 hours, then allow to equilibrate naturally for 30 minutes. 92%

[0073] Table 2

[0074] After passing the inspection, the material was packaged in vacuum-sealed, moisture-proof aluminum foil bags to prevent moisture absorption and contamination. Results showed that the material maintained good elasticity and durability under extreme conditions, while also possessing UV resistance, corrosion resistance, and slip resistance, achieving dynamic self-adaptation and ease of application.

[0075] Example 2: This example provides a method for preparing an elastic material for filling gaps in manhole covers. The specific implementation method is as follows:

[0076] This embodiment adjusts the formulation of Example 1 within the scope defined by the claims. 1. Raw material preparation

[0077] Ingredient Category specific chemicals Dosage Bio-based polylactic acid (PLA) NatureWorks Ingeo 4032D 50 g Thermoplastic elastomers (TPE) Kraton G1652 50 g Nanocarbon materials Carbon nanotubes with an aspect ratio > 1000 1.5 g Siloxane compounds Gelest M-1540 2 g UV absorber 2,2'-Dihydroxy-4,4'-stilbene (Tinuvin 328, Ciba patented product) 1.2 g Heat stabilizer 1,3,5-Trimethyl-2,4,6-triazacyclohexane (TMH, CAS 545-92-0) 0.6 g Preservatives <![CDATA[Sodium molybdate dihydrate (Na2MoO4·2H2O)]]> 0.6 g Plant-derived alcohol ester solvents Ethyl lactate (≥99%) 180 mL Crosslinking agent DTDM 1 g

[0078] Table 3

[0079] Note: PLA is NatureWorks Ingeo 4032D, which is biodegradable for industrial composting, has moderate mechanical properties, and can be processed at temperatures below 200℃; TPE is a styrene-isobutylene-styrene block copolymer, providing elasticity and low-temperature resistance; the nano-carbon material uses high aspect ratio carbon nanotubes, which enhance thermal conductivity, wear resistance, and mechanical strength; the siloxane compound Gelest M-1540 improves the material's UV resistance and oxidation resistance; Tinuvin 328 absorbs UV-A / B band light; TMH inhibits the thermal degradation of polymer chains; Na2MoO4·2H2O provides corrosion protection; ethyl lactate, as a green solvent, dissolves PLA and TPE, and is also easily volatile.

[0080] 2. Raw material dissolution and preliminary mixing

[0081] Add 50g PLA and 50g TPE to 180mL of ethyl lactate solvent. Stir at 3000rpm for 30 minutes using a high-shear mixer while heating the solution to 80℃ to ensure complete dissolution of PLA and TPE, forming a homogeneous and transparent solution. Dissolve 1g DTDM in 2ml of ethyl lactate to obtain a homogeneous crosslinking agent solution. Add this crosslinking agent solution to the above homogeneous and transparent solution and continue stirring at 80℃ for 10 minutes to ensure uniform dispersion of the dynamic disulfide crosslinking agent in the PLA / TPE matrix.

[0082] 3. Dispersion of nano-carbon materials

[0083] Add 1.5g of carbon nanotubes with an aspect ratio greater than 1000 to the solution in step 2. Use an ultrasonic disperser with a power of 1000W and a pulse mode of 10s on and 5s off for 15 minutes to ensure that the carbon nanotubes are fully dispersed and do not aggregate. Then stir with a stirrer for 10 minutes to ensure uniformity.

[0084] 4. Addition of siloxane compounds and functional additives

[0085] Add 2g of Gelest M-1540 to the solution from step 3, heat to 85℃ and stir for 15 minutes to promote fusion with the base polymer; then add 1.2g of UV absorber Tinuvin 328, 0.6g of heat stabilizer TMH and 0.6g of preservative additive Na2MoO4·2H2O in sequence, and stir for 20 minutes to ensure uniform distribution.

[0086] 5. Molding and thermosetting curing

[0087] Same as Example 1.

[0088] 6. Functional coatings

[0089] Same as Example 1.

[0090] 7. Quality Inspection and Packaging

[0091] Same as Example 1, including low-temperature elongation at break, high-temperature compression set, dry / wet friction coefficient, UV aging, oxidation resistance, water resistance and high-temperature resistance tests.

[0092] Test Project Sample size Test conditions Test value Low temperature elongation at break 50×10×5 mm -30℃, tensile rate 50mm / min 355% High temperature compression permanent deformation φ20×10 mm 70℃, compress by 50%, hold for 30 minutes 9.6% dry friction coefficient 50×50×5 mm Relative humidity 20%, vertical load 5N 0.68 wet friction coefficient 50×50×5 mm Add 0.2 mL / cm² of deionized water dropwise, with a vertical load of 5 N. 0.65 Tensile property retention rate after UV aging 50×10×5 mm UV 340nm, 0.76W / m², 60℃, 500h 94% Antioxidant properties 50×10×5 mm 70℃ air aging, 500h 90% Water resistance 50×10×5 mm Soak in deionized water at 25℃ for 24 hours, then allow to equilibrate naturally for 30 minutes. 92%

[0093] Table 4

[0094] Comparative Example 1 provides a method for preparing manhole cover gap filling material using conventional PLA and TPE materials, and the specific implementation method is as follows:

[0095] 1. Raw material preparation

[0096] Ingredient Category specific chemicals Dosage Bio-based polylactic acid (PLA) NatureWorks Ingeo 4032D 40 g Thermoplastic elastomers (TPE) Kraton G1652 60 g Green solvents Ethyl lactate (≥99%) 200 mL

[0097] Table 5

[0098] Note: This formulation is a combination of traditional PLA and TPE materials, without nano-carbon materials or dynamic crosslinking agents. It is mainly used for performance comparison with the material of this invention.

[0099] 2. Raw material dissolution and mixing

[0100] Add 40g PLA and 60g TPE to 200mL of ethyl lactate solvent.

[0101] Using a high-shear mixer, stir at 3000 rpm for 30 minutes while heating the solution to 80°C to ensure that PLA and TPE are fully dissolved and form a homogeneous solution.

[0102] 3. Molding and thermosetting curing

[0103] Pour the mixed solution into a mold that matches the gaps of the municipal manhole cover, with an inner diameter of 400mm, an outer diameter of 440mm, a ring width of 20mm, and a depth of 25mm.

[0104] Hot press molding machine conditions: temperature 150℃, pressure 8MPa, hold for 3 minutes to fully mold the material and obtain the expected size and shape.

[0105] After molding, allow it to cool naturally to room temperature, then remove the cured material as a comparative example 1 sample.

[0106] 4. Testing Methods

[0107] The material prepared in Comparative Example 1 was tested according to the standards of Example 1 for low-temperature elongation at break, high-temperature compression set, coefficient of friction, UV aging, oxidation resistance, and water resistance. The test procedures were the same as those in Example 1.

[0108] Test Project Sample Specifications Test conditions Test value Low temperature elongation at break 50×10×5 mm -30℃, tensile rate 50 mm / min 220% High temperature compression set φ20×10 mm 70℃, compress by 50%, hold for 30 minutes, then recover for 10 minutes. 22% dry friction coefficient 50×50×5 mm Relative humidity 20%, vertical load 5N 0.45 wet friction coefficient 50×50×5 mm Add 0.2 mL / cm² of deionized water dropwise, with a vertical load of 5 N. 0.35 UV absorption performance (tensile property retention rate after UV aging) 50×10×5 mm UV 340nm, 0.76W / m², 60℃, 500h 70% Antioxidant properties 50×10×5 mm 70℃ air aging, 500 h 72% Water resistance 50×10×5 mm Soak in deionized water at 25℃ for 24 hours, then allow to equilibrate naturally for 30 minutes. 88%

[0109] Table 6

[0110] Comparative Example 2 provides a method for preparing a commercial thermosetting polyurethane material, the specific implementation of which is as follows:

[0111] Commercial thermosetting polyurethane materials are commonly used to fill gaps in manhole covers.

[0112] 1. Raw material preparation

[0113] Ingredient Category specific chemicals Dosage Polyether polyol Voranol 490 50 g Isocyanate component (MDI) 4,4'-Diphenylmethane diisocyanate (MDI, Sigma-Aldrich) 25 g catalyst Diethanolamine / triethanolamine mixture 0.5 g surfactants Siloxane surfactant (BYK-348) 0.5 g filler Calcium oxide (CaO) 1 g solvent Acetone (≥99%) 100 mL

[0114] Table 7

[0115] This formulation is a simulation of commercial thermosetting polyurethane material, containing polyols and MDI isocyanate, with curing and foam formation assisted by catalysts and surfactants, and calcium oxide filler used to improve hardness and abrasion resistance.

[0116] 2. Material mixing and reaction

[0117] Add 50g of polyether polyol to 100mL of acetone solvent and stir with a magnetic stirrer at room temperature for 5 minutes to fully dissolve the polyol.

[0118] Add 0.5g of siloxane surfactant while stirring, and continue stirring for 3 minutes.

[0119] Add 25g of MDI isocyanate component and 0.5g of catalyst, stir for 5 minutes to ensure the mixture is homogeneous and the cross-linking reaction begins.

[0120] Add 1g of calcium oxide filler and stir for 2 minutes to ensure the filler is evenly dispersed in the system.

[0121] 3. Molding and Curing

[0122] Pour the uniformly mixed PU system into the manhole cover slot mold, with an inner diameter of 400mm, an outer diameter of 440mm, a ring width of 20mm, and a depth of 25mm.

[0123] Heat at 60℃ for 4 hours to cure until the material is completely cross-linked and hardened.

[0124] Remove the cured material and use it as the sample for Comparative Example 2.

[0125] 4. Testing Methods

[0126] The material prepared in Comparative Example 2 was tested using the same methods as in Example 1.

[0127] Test Project Sample Specifications Test conditions Test value Low temperature elongation at break 50×10×5 mm -30℃, tensile rate 50 mm / min 180% High temperature compression set φ20×10 mm 70℃, compress by 50%, hold for 30 min 18% dry friction coefficient 50×50×5 mm Relative humidity 20%, vertical load 5N 0.55 wet friction coefficient 50×50×5 mm Add 0.2 mL / cm² of deionized water dropwise, with a vertical load of 5 N. 0.48 UV absorption performance (tensile property retention rate after UV aging) 50×10×5 mm UV 340nm, 0.76W / m², 60℃, 500h 75% Antioxidant properties 50×10×5 mm 70℃ air aging, 500 h 78% Water resistance 50×10×5 mm Soak in deionized water at 25℃ for 24 hours, then allow to equilibrate naturally for 30 minutes. 90%

[0128] Table 8

[0129] In order to more intuitively demonstrate the differences between the embodiments of the present invention and the comparative materials in terms of key performance indicators, the present invention summarizes and compares the test results of the materials of Embodiment 1, Embodiment 2 and Comparative Examples 1 and 2, thereby clearly reflecting the excellent performance of the materials of the present invention in terms of low temperature elasticity, high temperature shape retention, friction anti-slip properties, UV aging resistance, oxidation resistance and water resistance.

[0130] Test Project Example 1 Example 2 Comparative Example 1 Comparative Example 2 Low temperature elongation at break 340% 355% 220% 180% High temperature compression set 9.2% 9.6% 22% 18% dry friction coefficient 0.72 0.68 0.45 0.55 wet friction coefficient 0.68 0.65 0.35 0.48 UV absorption performance (tensile property retention rate after UV aging) 92% 94% 70% 75% Antioxidant properties 89% 90% 72% 78% Water resistance 95% 96% 88% 90%

[0131] Table 9

[0132] 1. Low-temperature elasticity performance: The elongation at break of Examples 1 and 2 were 340% and 355%, respectively, which were significantly higher than 220% of Comparative Example 1 and 180% of Comparative Example 2. This indicates that the material of the present invention can still maintain excellent flexibility and ductility in cold environments, avoiding the problem of traditional PLA, PE and polyurethane materials being prone to brittleness at low temperatures.

[0133] 2. High-temperature shape retention: The high-temperature compression set rate of Examples 1 and 2 was controlled within 10%, while that of Comparative Examples 1 and 2 was 22% and 18%, respectively. The results show that the material of the present invention has better creep resistance under high-temperature conditions and is less prone to permanent deformation after long-term use, thus ensuring the reliability and safety of filling gaps in manhole covers.

[0134] 3. Anti-slip performance: Under both dry and wet friction conditions, the coefficient of friction of the materials in the examples remained above 0.65, while that of Comparative Example 1 was only 0.45 and 0.35, and that of Comparative Example 2 was only 0.55 and 0.48. This invention, through a surface nano-SiO2 polyurethane anti-slip coating and dynamic cross-linking design, enables the material to maintain stable high friction performance in both dry and wet environments, effectively improving safety in municipal road applications.

[0135] 4. UV aging resistance: In the ultraviolet aging test, the performance retention rates of Example 1 and Example 2 were 92% and 94%, respectively, which were much higher than those of Comparative Example 1 (70%) and Comparative Example 2 (75%). This indicates that the material of the present invention can still maintain good mechanical properties and appearance stability under long-term outdoor exposure conditions.

[0136] 5. Antioxidant performance: The antioxidant retention rates of the materials in the examples reached 89% and 90%, which are significantly better than those of Comparative Example 1 (72%) and Comparative Example 2 (78%). This indicates that by introducing heat stabilizers and siloxane modification systems, the materials of the present invention effectively delay oxidative degradation and extend their service life.

[0137] 6. Water resistance: The water resistance retention rates of Examples 1 and 2 were 95% and 96%, respectively, which were higher than those of Comparative Example 1 (88%) and Comparative Example 2 (90%). This indicates that the materials can maintain structural and performance stability even under long-term water contact without expansion, delamination, or degradation of mechanical properties.

[0138] As can be seen from the above comparison, the material of the embodiment of the present invention is significantly superior to the comparative material in terms of low-temperature elasticity, high-temperature stability, anti-slip performance, UV aging resistance, oxidation resistance, and water resistance, exhibiting the following beneficial effects:

[0139] Adaptable to extreme environments: It maintains high ductility at low temperatures and has good shape retention at high temperatures.

[0140] Outstanding anti-slip safety: Regardless of dry or wet environments, the coefficient of friction remains at a high level, significantly improving road safety.

[0141] Excellent weather resistance and durability: It has excellent UV resistance, oxidation resistance and water resistance, making it suitable for long-term outdoor applications.

[0142] Balanced overall performance: It takes into account mechanical properties, durability and environmental adaptability, and is superior to traditional PLA and TPE composite materials as well as commercial polyurethane materials.

[0143] Therefore, the material of this invention can achieve higher safety and durability in the application of filling gaps in municipal manhole covers, and has obvious promotional value and application prospects.

[0144] This embodiment demonstrates that the material of the present invention is easy to construct and suitable for actual road environments, solving the problems of slow construction and easy shrinkage and cracking of traditional materials. Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

[0145] It should be particularly noted that the various embodiments listed in this specification and accompanying drawings are intended to illustrate the technical solutions and advantages of the present invention, and not to limit the scope of protection of the present invention. Without departing from the core ideas and technical effects of the present invention, those skilled in the art can make any form of improvement, substitution, combination, or modification to the structural arrangement, process parameters, material selection, control logic, etc., of the described embodiments; any obvious changes based on the same concept should be considered equivalent solutions of the present invention and should be included within the scope of protection defined by the claims of the present invention. The actual scope of protection of the present invention is determined by the appended claims and should be correctly understood in conjunction with the specification and accompanying drawings.

Claims

1. A method for preparing an elastic material for filling gaps in manhole covers, characterized in that, Includes the following steps: S1. Raw material preparation: Bio-based polylactic acid (PLA) and thermoplastic elastomer (TPE) are used as base materials; nano-carbon materials are used as reinforcing materials; Siloxane compounds are used to enhance the material's UV absorption capacity and antioxidant properties; UV absorbers, heat stabilizers, and corrosion inhibitors are formulated; plant-derived alcohol ester solvents are selected; S2. Blending and Dissolving: Bio-based polylactic acid and thermoplastic elastomer are dissolved in plant-derived alcohol ester solvent and mixed using a high-shear mixer until a homogeneous solution is obtained; nano-carbon materials and dynamic disulfide bond crosslinking agents are added to the polymer solution and dispersed using ultrasound; siloxane compounds are added, and the mixture is heated to 60-90°C and stirred for 30-60 min to allow the siloxane compounds to be uniformly dispersed in the base material to form a compatible phase; S3. Functional adjustment: UV absorbers and heat stabilizers are added to the solution and heated and stirred to ensure uniform distribution; corrosion inhibitors are added to the solution to give the reinforcing material corrosion resistance. S4. Molding and Curing: Pour the treated solution into a mold and hot-press it to obtain the size and shape suitable for the manhole cover gaps; place the molded material in a cooling device to cool to room temperature, so that it can solidify and maintain its elasticity and toughness; S5. Functional coating: A polyurethane-based anti-slip coating containing nano-silica is applied to the surface of the molded material.

2. The method for preparing an elastic material for filling gaps in manhole covers according to claim 1, characterized in that, The mass ratio of bio-based polylactic acid to thermoplastic elastomer in step S1 is 4:6 to 5:

5.

3. The method for preparing an elastic material for filling gaps in manhole covers according to claim 1, characterized in that, The nano-carbon material mentioned in step S1 is graphene with a particle size of 20-50 nm or carbon nanotubes with an aspect ratio of >1000. The amount of nano-carbon material added is 0.5-3 wt% of the total mass of PLA and TPE.

4. The method for preparing an elastic material for filling gaps in manhole covers according to claim 1, characterized in that, The siloxane compound mentioned in step S1 is a hydroxyl-functionalized organosilicon resin.

5. The method for preparing an elastic material for filling gaps in manhole covers according to claim 1, characterized in that, The ultraviolet absorber mentioned in step S1 is a stilbene compound, the heat stabilizer is a nitrogen heterocyclic compound, and the corrosion inhibitor is a phosphate or molybdate compound. The amount of ultraviolet absorber added is 1-3 wt% of the raw material, and the amount of heat stabilizer added is 0.5-2 wt% of the raw material.

6. The method for preparing an elastic material for filling gaps in manhole covers according to claim 1, characterized in that, The dynamic disulfide crosslinking agent mentioned in step S2 is 4,4'-dithiodimorpholine, and the addition amount is 0.5-1.5 phr; wherein, phr represents the mass fraction of crosslinking agent per 100 parts by mass of resin matrix, and the resin matrix is ​​the sum of bio-based polylactic acid and thermoplastic elastomer.

7. The method for preparing an elastic material for filling gaps in manhole covers according to claim 1, characterized in that, In step S2, the ultrasonic dispersion power is 800-1200W and the time is 10-20min; in step S4, the hot pressing temperature is 130-150℃, the pressure is 8-12 MPa, and the holding time is 3-5min.

8. A method for preparing an elastic material for filling gaps in manhole covers according to claim 1, characterized in that, The plant-derived alcohol ester solvent in step S1 is ethyl lactate.

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