Foaming EPDM material, preparation method thereof and sealing strip

Abstract

The invention discloses a low-pressure-change foamed EPDM (Ethylene-Propylene-Diene Monomer) material as well as a preparation method and a sealing strip thereof, and belongs to the technical field of high polymer materials. According to the material, alkali lignin is subjected to surface modification by adopting a ternary reactive deep eutectic solvent (RDES) composed of choline chloride, a functional hydrogen bond donor HBD-1 and urea; the modified alkali lignin is blended with ethylene propylene diene monomer, carbon black and the like, and HBD-1 is preferably an addition product of DOPO (9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) and GMA (glycidyl methacrylate). The problems that in the prior art, a foamed EPDM material is large in high-temperature compression permanent deformation, poor in low-temperature resistance, standard-exceeding in smell / VOC and the like are solved, and the obtained material has excellent comprehensive performance and can be used for preparing high-performance sealing strips.

Description

Technical Field

[0001] This application relates to the field of polymer materials technology, specifically to an ethylene propylene diene monomer (EPDM) foam material, and more particularly to a foamed EPDM composite material with modified biomass filler as a functional reinforcement. Background Technology

[0002] Ethylene propylene diene monomer (EPDM) rubber, due to its saturated molecular backbone structure, possesses excellent weather resistance, ozone resistance, hot air aging resistance, chemical resistance, and superior electrical insulation properties. It is widely used in the automotive, construction, and wire and cable industries, making it an ideal matrix material for manufacturing sealing strips. Foamed EPDM sealing strips, by introducing a cell structure, achieve advantages such as lightweight and low compressive stress while maintaining excellent sealing performance, and dominate applications for sealing, vibration damping, and sound insulation in automotive doors, windows, hoods, and trunks.

[0003] For automotive sealing strips, long-term reliability is crucial. Among the key indicators for evaluating their sealing lifespan is the compression set performance at high temperatures. Sealing strips are under constant compression after assembly, especially in high-temperature environments such as the engine compartment and battery compartment. If the material's resistance to thermal relaxation is insufficient, irreversible permanent deformation can occur, leading to a decrease in sealing pressure and ultimately the loss of their sealing, sound insulation, and dustproofing functions.

[0004] Currently, the mainstream technology in the industry for improving the compression set performance of foamed EPDM is to fill the rubber matrix with a large amount of reinforcing agent, most commonly carbon black. By forming a dense filler network in the matrix through high carbon black loading, the creep of polymer chains at high temperatures can be limited to some extent, thereby improving compression set. However, relying solely on high carbon black loading has limitations in improving compression set and cannot meet increasingly stringent high-temperature testing standards. Simultaneously, a large amount of carbon black significantly restricts the movement of EPDM molecular chains, leading to a sharp decrease in the material's flexibility at low temperatures, resulting in hardening or even embrittlement, affecting its reliability in cold regions. Furthermore, high carbon black loading is one of the main reasons for high odor levels and excessive volatile organic compound (VOC) content in composite materials. With increasingly stringent VIAQ (Vehicle Air Quality) controls in the automotive industry, traditional high carbon black formulations are no longer sufficient to meet the demands of modern high-end applications.

[0005] In search of alternatives, researchers have begun to focus on lignin and other widely available, inexpensive, and renewable biomass fillers. The rigid benzene ring structure in lignin molecules can theoretically provide excellent physical support for cell pores. However, as a polar natural polymer, lignin exhibits severe thermodynamic incompatibility with the nonpolar EPDM matrix, leading to its tendency to aggregate and become difficult to disperse uniformly. These aggregates not only fail to provide effective reinforcement but also become stress concentration points and defects within the material, resulting in deterioration of mechanical properties and cell structure. Although some studies have attempted to modify the surface of lignin using conventional silane coupling agents, this method is typically complex and may introduce new small-molecule volatiles during modification and subsequent processing, failing to fundamentally solve the odor and VOC problems.

[0006] Therefore, there is an urgent need in this field for a new technical solution that can significantly improve the high-temperature compression set performance of foamed EPDM materials, while simultaneously overcoming the problems of poor low-temperature resistance and excessive odor / VOC caused by the traditional high-filler carbon black technology route. It can also effectively solve the interfacial compatibility problem between biomass fillers such as lignin and rubber matrix, thereby preparing high-performance, lightweight, and environmentally friendly EPDM sealing materials that meet the requirements of modern industrial applications. Summary of the Invention

[0007] The purpose of this invention is to overcome the above-mentioned defects of the prior art, and to address the technical problems of large high-temperature compression set of existing foamed EPDM materials and poor interfacial compatibility between biomass fillers (such as lignin) and rubber matrix, by providing a foamed EPDM material with low compression set, its preparation method, and a sealing strip made therefrom.

[0008] A foamed EPDM material, characterized in that it is prepared from the following raw materials in parts by weight: 100 parts of ethylene propylene diene monomer (EPDM) rubber; 5-20 parts of alkali lignin modified with a ternary reactive deep eutectic solvent (RDES); 20-50 parts of reinforcing filler; Vulcanization system: 1-45 parts; 5-10 parts of foaming agent; The ternary reactive deep eutectic solvent (RDES) is composed of choline chloride, functional hydrogen bond donor HBD-1, and urea in a molar ratio of 1:(1.0~2):0.3~1.

[0009] Specifically, the functional hydrogen bond donor HBD-1 is the product of the addition reaction between a compound containing a DOPO group and a compound containing an epoxy group.

[0010] Specifically, the compound containing the DOPO group is 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), and the compound containing the epoxy group is glycidyl methacrylate (GMA).

[0011] Specifically, the reinforcing filler is selected from: (1) Carbon black in a dosage of 2050 parts; (2) 2040 parts of silica; or (3) A combination of carbon black and silica, wherein the total amount of carbon black and silica is 20 to 50 parts.

[0012] Specifically, the vulcanization system is selected from: (1) A sulfur sulfidation system, including sulfur, accelerator and activator; or (2) Click the chemical sulfurization system, including 20 to 40 parts of mercapto compound and 1 to 3 parts of initiator.

[0013] Specifically, the thiol compound is selected from one or more of 1,6-hexanedithiol (HDT), pentaerythritol tetra(3-mercaptopropionate) (PETMP), or 1,8-octanedithiol (ODT).

[0014] Specifically, the alkali lignin modified by RDES is obtained by contacting alkali lignin with RDES at 80-120°C for 1-5 hours, and then drying it after water washing and alcohol washing treatment.

[0015] Specifically, the preparation method of foamed EPDM material includes the following steps: S1: The functional hydrogen bond donor HBD-1 was prepared; S2: The HBD-1 is mixed with choline chloride and urea under heating and stirring conditions to form a homogeneous ternary reactive deep eutectic solvent (RDES) liquid phase reaction medium. S3: Add alkali lignin to the RDES to carry out a surface modification reaction to obtain modified alkali lignin; S4: The modified alkali lignin, reinforcing filler, EPDM rubber and other additives are mixed, extruded and molded, and then vulcanized and foamed at high temperature to obtain the foamed EPDM material.

[0016] Specifically, step S1 includes: performing an addition reaction between a compound containing a DOPO group and a compound containing an epoxy group to prepare the functional hydrogen bond donor HBD-1.

[0017] A sealing strip is made from the aforementioned foamed EPDM material and preparation method. Beneficial effects

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Improved high-temperature compression set performance of the material, enhancing its long-term reliability as a sealing material. Existing EPDM foam materials exhibit significant compression set at high temperatures (48%), easily leading to seal failure. This invention introduces alkali lignin modified with a specific RDES system to construct a high-temperature resistant microscopic physical support network within the EPDM matrix, effectively suppressing cell creep and collapse under thermal load.

[0019] 2. Improved low-temperature resistance of the material, broadening its application range. Traditional high-filler carbon black formulations become brittle and lose elasticity at low temperatures (-40℃). This invention replaces most of the carbon black with functionalized modified alkali lignin, effectively maintaining the mobility of the matrix polymer chains at low temperatures while ensuring reinforcement, thus solving the problem of poor reliability of existing technologies in cold environments.

[0020] 3. Significantly reduced odor level and total VOC content of the material, meeting the environmental protection requirements of high-end applications (especially automotive interiors). This invention controls the generation of volatile organic compounds from the formulation and preparation source by reducing the amount of carbon black, the main source of pollution, and adopting an RDES green modification process without volatile byproducts.

[0021] 4. Improved overall mechanical properties and uniformity of cell structure in composite materials. The RDES modification process of this invention effectively improves the interfacial compatibility between alkali lignin and EPDM matrix, allowing the filler to exist as a reinforcing point rather than a defect point, thus achieving overall performance optimization of the material.

[0022] 5. This invention endows the material with excellent inherent flame retardancy and potential for functional expansion. Because the chemical structure of the novel functional hydrogen bond donor HBD-1 contains a DOPO (phosphaphenanthrene) flame-retardant group, the basic formulation itself achieves a UL-94V-0 flame retardant rating, which is an unexpected technological advantage. Furthermore, this technical system exhibits good compatibility with added flame retardants, demonstrating the enormous potential of this invention's technical solution for expanding into higher-level functional applications. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the preparation of modified DOPO.

[0024] Figure 2 This is a schematic diagram of the preparation of ternary reactive deep eutectic solvents (RDES).

[0025] Figure 3 This is a schematic diagram of the modification of alkali lignin.

[0026] Figure 4This is a schematic diagram of the preparation of foamed EPDM material. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] To further illustrate the technical solution of the present invention, a specific embodiment is described in detail below. It should be understood that this embodiment is for illustrative purposes only and is not intended to limit the scope of protection of the present invention in any way.

[0029] Unless otherwise specified, all reagents and raw materials used in this embodiment are commercially available analytical grade or industrial grade products.

[0030] The corresponding Chinese names for some abbreviations are as follows: DOPO: 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide; GMA: glycidyl methacrylate; HDT: 1,6-hexanedithiol; AIBN: azobisisobutyronitrile 1. Preparation of modified DOPO Under a nitrogen atmosphere, 43.2 g (0.2 mol) of DOPO and 300 mL of toluene were added to a 500 mL three-necked flask equipped with a reflux condenser, magnetic stirrer, and constant-pressure dropping funnel. Stirring was started, and the temperature was raised to 80°C to completely dissolve the DOPO. 1.0 g (0.01 mol) of triethylamine was added as a catalyst. 30.0 g (0.21 mol, 1.05 equivalent) of GMA was slowly added dropwise through the constant-pressure dropping funnel. The addition process was exothermic; the dropping rate was controlled to keep the system temperature below 100°C. After the addition was complete, the temperature was raised to 110°C and the reaction was maintained for 6 hours. The reaction mixture was cooled to room temperature, and the reaction solution was transferred to a rotary evaporator. The toluene solvent was removed by rotary evaporation under reduced pressure. The resulting viscous product was washed with 200 mL of n-hexane and slurried three times to remove unreacted GMA and catalyst. The solid product was filtered, collected, and dried in a vacuum oven at 60°C for 24 hours to obtain 72.5 g of white solid powder, which is the functional hydrogen bond donor HBD-1 (DOPO-GMA adduct), with a yield of approximately 79%.

[0031] 2. Preparation of ternary reactive deep eutectic solvent (RDES): Choline chloride (ChCl), HBD-1, urea and alkali lignin powder were all placed in an 80°C vacuum oven and dried for 24 hours.

[0032] In a 500mL sealed reactor equipped with a powerful mechanical stirrer and a heating mantle, weigh and add the following dry raw materials according to the molar ratio of ChCl:HBD-1:urea = 1:1.5:0.5: 0.2mol ChCl, 0.3mol HBD-1, and 0.1mol urea. Seal the reactor, start the stirrer, and heat to 100°C. Stir for 30 minutes to form a viscous liquid. Proceed directly to the next step without post-treatment.

[0033] 3. Modification of alkali lignin While maintaining a temperature of 100°C and vigorous stirring, slowly add 15.7 g of dry alkali lignin powder (the mass ratio of RDES to lignin is approximately 9:1) to the above RDES, and continue to react with vigorous stirring at 100°C for 3 hours. After the reaction is complete, slowly pour the hot, viscous mixture into 2 L of deionized water and disperse it under high-speed stirring. Collect the precipitate by centrifugation, wash it repeatedly with deionized water 3-5 times, and then wash the precipitate twice with ethanol. Dry the final product in a vacuum oven at 60°C for 48 hours to obtain a brownish-red powder, which is the modified alkali lignin.

[0034] 4. Intensive mixing of EPDM rubber compound After preheating the internal mixer to 70-80℃, add EPDM (ethylene propylene diene monomer rubber), stearic acid and OBSH (foaming agent) into the internal mixer and mix for 60 seconds; then add modified alkali lignin and continue mixing for 2 minutes; then add N660 carbon black, raise the temperature to 140℃ and mix until all components are evenly dispersed; then discharge the rubber and cool the compound to 60-70℃, add the vulcanizing agent, and continue mixing for 2 to 3 minutes to obtain the compound.

[0035] The vulcanizing agent can be sulfur or a mercapto compound.

[0036] When sulfur is selected as the vulcanizing agent, a vulcanization accelerator and an activator are used in conjunction to accelerate the vulcanization rate. The activator is preferably ZnO, which is added simultaneously with stearic acid. The vulcanization accelerator is preferably ZBPD-50, which is added simultaneously with sulfur.

[0037] When a mercapto compound is selected as a vulcanizing agent, an initiator is used in conjunction to enhance the vulcanization effect. The preferred initiator is AIBN.

[0038] The thiol compound is selected from one or more of 1,6-hexanedithiol (HDT), pentaerythritol tetra(3-mercaptopropionate) (PETMP), or 1,8-octanedithiol (ODT).

[0039] 5. Preparation of foamed EPDM materials The above-mentioned compound rubber was extruded and then placed in a three-stage continuous vulcanization process for vulcanization. The vulcanization process is as follows: the first stage is at 380°C, with an action time corresponding to a stroke of 3 meters; the second stage is at 230°C, with an action time corresponding to a stroke of 9 meters; and the third stage is at 270°C, with an action time corresponding to a stroke of 9 meters. Throughout the entire vulcanization process, the traction speed of the rubber compound is 10 meters per minute.

[0040] Traditional formulation: The components of the composite material are as follows, by weight: EPDM, 100 parts; ordinary carbon black, 120 parts; sulfur, 1.5 parts; accelerator, 2 parts; zinc oxide, 8 parts; stearic acid, 1 part; foaming agent (OBSH), 6 parts; paraffin oil, 30 parts.

[0041] Formula 1 of this application (sulfur system): The components of the composite material are, by weight, as follows: EPDM, 100 parts; Alkali lignin (particle size ≤ 5 μm), 5-15 parts; Carbon black (N660), 30-50 parts; Sulfur, 0.8 parts; Nitrosamine-free accelerator (ZBPD-50), 4-6 parts; Zinc oxide (ZnO), 3-6 parts; Stearic acid, 1 part; Foaming agent (OBSH), 5-10 parts; Paraffin oil, 20 parts.

[0042] Formula 2 of this application (click reaction system): The components of the composite material are, by weight, as follows: EPDM, 100 parts; Alkali lignin (particle size ≤ 5 μm), 5-15 parts; Carbon black (N660), 30-50 parts; Thiol compound, 20-40 parts; AIBN, 1-3 parts; Zinc oxide (ZnO), 3-6 parts; Stearic acid, 1 part; Foaming agent (OBSH), 5-10 parts; Paraffin oil, 20 parts.

[0043] The preferred EPDM is: low-ethylene, high-Money EPDM (third monomer ENB ≥ 5%).

[0044] Technical parameter testing standards and methods: Compression set: The product in this embodiment has a compression set of 25% under conditions of 80℃×96h, while the conventional formula has a compression set of 48% under conditions of 70℃×72h. Tensile strength: 8.2 MPa in this embodiment, 5.5 MPa in the traditional formulation; Cell uniformity: Cell uniformity (CV value) < 10%; Odor rating: 80℃ / 2h sealed test → 2.8 (VDA 270); Low temperature resistance: It maintains good elasticity at -40℃, while traditional formulas become brittle.

[0045] Results analysis: This embodiment significantly improves the low-pressure deformation resistance of the sealing strip through formula and process optimization. All indicators are superior to traditional products and meet the requirements of 80℃×96h and ≤40%.

[0046] Odor Level / Grade: Place the sample in a test container without adding water. Seal the container tightly and place it in a preheated electric thermostatic drying oven to heat to 80±2℃ for 2 hours±10 minutes. Then remove the test container from the oven and allow it to cool to 60±5℃ before evaluation. During evaluation, bring your nose close to the edge of the open bottle, with the edge between your nose and lips. The evaluator's nose should be approximately 2-3 cm from the bottle opening. The bottle cap should not be open for more than 10 seconds, and the evaluator should inhale normally. Odor Level Determination Method: Level 1: No odor; Level 2: Slight odor, but no interfering odor; Level 3: Obvious odor, but no interfering odor; Level 4: Interfering odor; Level 5: Strong interfering odor; Level 6: Unbearable odor. Data should be accurate to one decimal place. Five evaluators should jointly evaluate and write individual evaluation comments.

[0047] Compression set / %: Refer to GB / T7759.1-2015.

[0048] Tensile strength / MPa, elongation / %: Refer to GB / T528-2009.

[0049] Low temperature resistance (-40℃): Refer to GB / T 15256-2014.

[0050] Heat resistance air aging: Refer to GB / T 3512.

[0051] Example 1: 100 parts of ethylene propylene diene monomer (EPDM), 10 parts of modified alkali lignin (particle size ≤ 5 μm) obtained by treating with RDES system (choline chloride: HBD-1: urea = 1:1.5:0.5) at 100℃ for 3 hours, 40 parts of carbon black (N660), 0.8 parts of sulfur, 5 parts of nitrosamine-free accelerator ZBPD-50, 5 parts of zinc oxide, 1 part of stearic acid, 8 parts of foaming agent OBSH, and 20 parts of paraffin oil were sequentially added to a mixer. After mixing, extrusion molding, vulcanization and foaming processes, foamed EPDM samples were obtained.

[0052] Example 2: 100 parts of ethylene propylene diene monomer (EPDM), 10 parts of modified alkali lignin obtained by treating with RDES system (choline chloride: HBD-1: urea = 1:2:1) at 100°C for 3 hours, 40 parts of carbon black (N660), 0.8 parts of sulfur, 5 parts of nitrosamine-free accelerator ZBPD-50, 5 parts of zinc oxide, 1 part of stearic acid, 8 parts of foaming agent OBSH, and 20 parts of paraffin oil were sequentially added to a mixer. After mixing, extrusion molding, vulcanization and foaming processes, foamed EPDM samples were obtained.

[0053] Example 3: 100 parts of ethylene propylene diene monomer (EPDM), 10 parts of modified alkali lignin obtained by treating the RDES system (choline chloride: HBD-1: urea = 1:1.5:0.5) at 100°C for 1 hour, 40 parts of carbon black (N660), 0.8 parts of sulfur, 5 parts of nitrosamine-free accelerator ZBPD-50, 5 parts of zinc oxide, 1 part of stearic acid, 8 parts of foaming agent OBSH, and 20 parts of paraffin oil were sequentially added to a mixer. After mixing, extrusion molding, vulcanization and foaming processes, foamed EPDM samples were obtained.

[0054] Example 4: 100 parts of ethylene propylene diene monomer (EPDM), 5 parts of modified alkali lignin, 50 parts of carbon black (N660), 0.8 parts of sulfur, 5 parts of ZBPD-50, 5 parts of zinc oxide, 1 part of stearic acid, 8 parts of OBSH, and 20 parts of paraffin oil were added to a mixer in sequence. After mixing, extrusion molding, vulcanization and foaming, foamed EPDM samples were obtained.

[0055] Example 5: 100 parts of EPDM, 8 parts of modified alkali lignin, 30 parts of carbon black (N660), 1.2 parts of sulfur, 4 parts of ZBPD-504, 6 parts of ZnO, 1 part of stearic acid, 8 parts of OBSH, and 25 parts of paraffin oil were added to a mixer in sequence. After mixing, extrusion molding, vulcanization and foaming, foamed EPDM samples were obtained.

[0056] Example 6: 100 parts of EPDM, 12 parts of modified alkali lignin, 50 parts of carbon black, 0.7 parts of sulfur, 6 parts of ZBPD-50, 5 parts of ZnO, 1 part of stearic acid, 7 parts of OBSH, and 20 parts of paraffin oil were added to a mixer in sequence. After mixing, extrusion molding, vulcanization and foaming, foamed EPDM samples were obtained.

[0057] Example 7: 100 parts of EPDM, 20 parts of modified alkali lignin, 40 parts of carbon black, 1.0 part of sulfur, 4 parts of ZBPD-50, 5 parts of ZnO, 1 part of stearic acid, 6 parts of OBSH, and 20 parts of paraffin oil were added to a mixer in sequence. After mixing, extrusion molding, vulcanization and foaming, foamed EPDM samples were obtained.

[0058] Example 8: 100 parts of EPDM, 10 parts of RDES-treated alkali lignin, 20 parts of carbon black, 20 parts of silica, 0.8 parts of sulfur, 5 parts of ZBPD-50, 6 parts of ZnO, 1 part of stearic acid, 8 parts of OBSH, and 20 parts of paraffin oil were added to a mixer in sequence. After mixing, extrusion molding, vulcanization and foaming, foamed EPDM samples were obtained.

[0059] Example 9: 100 parts of EPDM, 10 parts of RDES-treated alkali lignin, 40 parts of carbon black, 0.6 parts of sulfur, 3 parts of TBzTD, 6 parts of ZnO, 1 part of stearic acid, 8 parts of OBSH, and 20 parts of paraffin oil were added to a mixer in sequence. After mixing, extrusion molding, vulcanization and foaming, foamed EPDM samples were obtained.

[0060] Example 10: 100 parts of ethylene propylene diene monomer (EPDM), 10 parts of modified alkali lignin, 40 parts of carbon black (N660), 5 parts of zinc oxide, 1 part of stearic acid, 8 parts of foaming agent OBSH, 20 parts of paraffin oil, and 1.2 parts of peroxide vulcanizing agent BIPB were added to a mixer in sequence. After mixing, extrusion molding, vulcanization and foaming, foamed EPDM samples were obtained.

[0061] Example 11: 100 parts of ethylene propylene diene monomer (EPDM), 10 parts of modified alkali lignin, 40 parts of carbon black (N660), 30 parts of thiol compound HDT, 2 parts of initiator AIBN, 5 parts of zinc oxide, 1 part of stearic acid, 8 parts of foaming agent OBSH, and 20 parts of paraffin oil were added to a mixer in sequence. After mixing, extrusion molding, vulcanization and foaming, foamed EPDM samples were obtained.

[0062] Example 12: 100 parts of EPDM, 10 parts of RDES-treated alkali lignin, 50 parts of carbon black, 20 parts of thiol compound PETMP, 3 parts of AIBN, 5 parts of ZnO, 1 part of stearic acid, 8 parts of OBSH, and 20 parts of paraffin oil were added to a mixer in sequence. After mixing, extrusion molding, vulcanization and foaming, foamed EPDM samples were obtained.

[0063] Example 13: 100 parts of EPDM, 10 parts of RDES-treated alkali lignin, 30 parts of carbon black, 40 parts of thiol compound ODT, 2 parts of AIBN, 5 parts of ZnO, 1 part of stearic acid, 8 parts of OBSH, and 20 parts of paraffin oil were added to a mixer in sequence. After mixing, extrusion molding, vulcanization and foaming, foamed EPDM samples were obtained.

[0064] Example 14: 100 parts of nitrile rubber (NBR N41), 10 parts of modified alkali lignin obtained by treating with RDES system (choline chloride: HBD-1: urea = 1:1.5:0.5) at 100°C for 3 hours, 40 parts of carbon black (N660), 0.8 parts of sulfur, 5 parts of nitrosamine-free accelerator ZBPD-50, 5 parts of zinc oxide, 1 part of stearic acid, 8 parts of foaming agent OBSH, and 20 parts of dioctyl phthalate (DOP) were sequentially added to a mixer. After mixing, extrusion molding, vulcanization and foaming processes, foamed NBR samples were obtained.

[0065] Example 15: 100 parts of styrene-butadiene rubber (SBR 1502), 10 parts of modified alkali lignin obtained by treating with RDES system (choline chloride: HBD-1: urea = 1:1.5:0.5) at 100°C for 3 hours, 40 parts of carbon black (N660), 0.8 parts of sulfur, 5 parts of nitrosamine-free accelerator ZBPD-50, 5 parts of zinc oxide, 1 part of stearic acid, 8 parts of foaming agent OBSH, and 20 parts of naphthenic oil were sequentially added to a mixer. After mixing, extrusion molding, vulcanization and foaming processes, foamed SBR samples were obtained.

[0066] Example 16: 100 parts of ethylene propylene diene monomer (EPDM), 10 parts of modified alkali lignin, 40 parts of carbon black (N660) treated with RDES (choline chloride: HBD-1: urea = 1:1.5:0.5) at 100°C for 3 hours, 0.8 parts of sulfur, 5 parts of nitrosamine-free accelerator ZBPD-50, 5 parts of zinc oxide, 1 part of stearic acid, 8 parts of foaming agent OBSH, and 20 parts of paraffin oil were sequentially added to a mixer. After mixing, extrusion molding, vulcanization and foaming processes, foamed EPDM samples were obtained.

[0067] Example 17: 100 parts of EPDM, 10 parts of modified alkali lignin, 40 parts of silica (treated with RDES), 0.8 parts of sulfur, 5 parts of ZBPD-50, 5 parts of ZnO, 1 part of stearic acid, 10 parts of OBSH, and 20 parts of paraffin oil were added to a mixer in sequence. After mixing, extrusion molding, vulcanization and foaming, foamed EPDM samples were obtained.

[0068] Example 18: 100 parts of EPDM, 8 parts of RDES-treated alkali lignin, 30 parts of carbon black, 3 parts of DOPO, 0.8 parts of sulfur, 5 parts of ZBPD-50, 6 parts of ZnO, 1 part of stearic acid, 8 parts of OBSH, and 20 parts of paraffin oil were added to a mixer in sequence. After mixing, extrusion molding, vulcanization and foaming, foamed EPDM samples were obtained.

[0069] Example 19: 100 parts of EPDM, 10 parts of RDES-treated alkali lignin, 40 parts of carbon black, 8 parts of APP, 0.8 parts of sulfur, 5 parts of ZBPD-50, 6 parts of ZnO, 1 part of stearic acid, 8 parts of OBSH, and 20 parts of paraffin oil were added to a mixer in sequence. After mixing, extrusion molding, vulcanization and foaming, foamed EPDM samples were obtained.

[0070] Example 20: 100 parts of ethylene propylene diene monomer (EPDM), 60 parts of modified alkali lignin obtained by treating the RDES system (choline chloride: HBD-1: urea = 1:1.5:0.5) at 100°C for 3 hours, 10 parts of carbon black (N660), 0.8 parts of sulfur, 5 parts of nitrosamine-free accelerator ZBPD-50, 6 parts of zinc oxide, 1.5 parts of stearic acid, 8 parts of foaming agent OBSH, and 35 parts of paraffin oil were sequentially added to a mixer. After mixing, extrusion molding, vulcanization and foaming processes, foamed EPDM samples were obtained.

[0071] Example 21: 100 parts of ethylene propylene diene monomer (EPDM), 70 parts of modified alkali lignin obtained by treating with RDES system (choline chloride: HBD-1: urea = 1:1.5:0.5) at 100°C for 3 hours, 1.0 part of sulfur, 5 parts of nitrosamine-free accelerator ZBPD-50, 6 parts of zinc oxide, 1.5 parts of stearic acid, 8 parts of foaming agent OBSH, and 40 parts of paraffin oil were sequentially added to a mixer. After mixing and extrusion molding, foamed EPDM samples were obtained by vulcanization at 155°C for 12 minutes.

[0072] Example 22: 100 parts of ethylene propylene diene monomer (EPDM), 60 parts of RDES-treated alkali lignin, 10 parts of carbon black (N660), 30 parts of thiol compound HDT, 2 parts of initiator AIBN, 6 parts of zinc oxide, 1.5 parts of stearic acid, 8 parts of foaming agent OBSH, and 35 parts of paraffin oil were sequentially added to a mixer. After mixing, extrusion molding, vulcanization and foaming processes, foamed EPDM samples were obtained.

[0073] Example 23: 100 parts of ethylene propylene diene monomer (EPDM), 60 parts of RDES-treated alkali lignin, 10 parts of carbon black (N660), 25 parts of thiol compound PETMP, 2 parts of initiator AIBN, 6 parts of zinc oxide, 1.5 parts of stearic acid, 8 parts of foaming agent OBSH, and 35 parts of paraffin oil were sequentially added to a mixer. After mixing, extrusion molding, vulcanization and foaming processes, foamed EPDM samples were obtained.

[0074] Example 24: 100 parts of EPDM, 15 parts of modified alkali lignin, 45 parts of carbon black, 0.8 parts of sulfur, 5 parts of nitrosamine-free accelerator (ZBPD-50), 3 parts of zinc oxide (ZnO), 1 part of stearic acid, 10 parts of foaming agent (OBSH), and 20 parts of paraffin oil were added to a mixer in sequence. After mixing, extrusion molding, vulcanization and foaming processes, foamed EPDM samples were obtained.

[0075] Example 25: 100 parts of EPDM, 5 parts of modified alkali lignin, 50 parts of carbon black, 30 parts of thiol compound HDT, 1 part of initiator (AIBN), 5 parts of zinc oxide, 1 part of stearic acid, 5 parts of foaming agent (OBSH), and 20 parts of paraffin oil were added to a mixer in sequence. After mixing, extrusion molding, vulcanization and foaming, foamed EPDM samples were obtained.

[0076] Example 26: 100 parts of EPDM, 15 parts of modified alkali lignin, 45 parts of carbon black, 30 parts of thiol compound HDT, 2 parts of initiator (AIBN), 6 parts of zinc oxide (ZnO), 1 part of stearic acid, 8 parts of foaming agent (OBSH), and 20 parts of paraffin oil were added to a mixer in sequence. After mixing, extrusion molding, vulcanization and foaming processes, foamed EPDM samples were obtained.

[0077] Comparative Example 1: 100 parts of EPDM, 120 parts of carbon black, 1.5 parts of sulfur, 1.2 parts of traditional nitrosamine accelerator M, 1.5 parts of ZDBC, 8 parts of ZnO, 1 part of stearic acid, 6 parts of OBSH, and 30 parts of paraffin oil were added to a mixer in sequence. After mixing, extrusion molding, vulcanization and foaming, foamed EPDM samples were obtained.

[0078] Comparative Example 2: 100 parts of EPDM, 40 parts of carbon black, 0.8 parts of sulfur, 5 parts of ZBPD-50, 5 parts of ZnO, 1 part of stearic acid, and 20 parts of paraffin oil were added to a mixer in sequence. After mixing, extrusion molding, vulcanization and other processes, a dense EPDM sample was obtained.

[0079] Comparative Example 3: 100 parts of ethylene propylene diene monomer (EPDM), 10 parts of unmodified alkali lignin, 40 parts of carbon black (N660), 0.8 parts of sulfur, 5 parts of nitrosamine-free accelerator ZBPD-50, 5 parts of zinc oxide, 1 part of stearic acid, 8 parts of foaming agent OBSH, and 20 parts of paraffin oil were added to a mixer in sequence. After mixing, extrusion molding, vulcanization and foaming, foamed EPDM samples were obtained.

[0080] Comparative Example 4: 100 parts of ethylene propylene diene monomer (EPDM), 10 parts of alkali lignin modified with silane coupling agent Si-69, 40 parts of carbon black (N660), 0.8 parts of sulfur, 5 parts of nitrosamine-free accelerator ZBPD-50, 5 parts of zinc oxide, 1 part of stearic acid, 8 parts of foaming agent OBSH, and 20 parts of paraffin oil were added to a mixer in sequence. After mixing, extrusion molding, vulcanization and foaming processes, foamed EPDM samples were obtained.

[0081] Comparative Example 5: 100 parts of ethylene propylene diene monomer (EPDM), 10 parts of ordinary lignin obtained by treating the RDES system (choline chloride: HBD-1: urea = 1:1.5:0.5) at 100℃ for 3 hours, 40 parts of carbon black (N660), 0.8 parts of sulfur, 5 parts of nitrosamine-free accelerator ZBPD-50, 5 parts of zinc oxide, 1 part of stearic acid, 8 parts of foaming agent OBSH, and 20 parts of paraffin oil were sequentially added to a mixer. After mixing, extrusion molding, vulcanization and foaming processes, foamed EPDM samples were obtained.

[0082] Comparative Example 6: 100 parts of ethylene propylene diene monomer (EPDM) rubber, 10 parts of modified lignin sulfonate obtained by treating the RDES system (choline chloride: HBD-1: urea = 1:1.5:0.5) at 100℃ for 3 hours, 40 parts of carbon black (N660), 0.8 parts of sulfur, 5 parts of nitrosamine-free accelerator ZBPD-50, 5 parts of zinc oxide, 1 part of stearic acid, 8 parts of foaming agent OBSH, and 20 parts of paraffin oil were sequentially added to a mixer. After mixing, extrusion molding, vulcanization and foaming processes, foamed EPDM samples were obtained.

[0083] Comparative Example 7: 100 parts of ethylene propylene diene monomer (EPDM), 60 parts of unmodified alkali lignin, 10 parts of carbon black (N660), 0.8 parts of sulfur, 5 parts of nitrosamine-free accelerator ZBPD-50, 6 parts of zinc oxide, 1.5 parts of stearic acid, 8 parts of foaming agent OBSH, and 35 parts of paraffin oil were added to a mixer in sequence. After mixing, extrusion molding, vulcanization and foaming processes, foamed EPDM samples were obtained.

[0084] Comparative Example 8: 100 parts of ethylene propylene diene monomer (EPDM), 10 parts of modified alkali lignin obtained by treating the RDES system (choline chloride: glycerol: urea = 1:1.5:0.5) at 100℃ for 3 hours, 40 parts of carbon black (N660), 0.8 parts of sulfur, 5 parts of nitrosamine-free accelerator ZBPD-50, 5 parts of zinc oxide, 1 part of stearic acid, 8 parts of foaming agent OBSH, and 20 parts of paraffin oil were sequentially added to a mixer. After mixing, extrusion molding, vulcanization and foaming processes, foamed EPDM samples were obtained.

[0085] Comparative Example 9: 100 parts of ethylene propylene diene monomer (EPDM), 10 parts of modified alkali lignin, 40 parts of carbon black (N660), 0.4 parts of sulfur, 2.5 parts of nitrosamine-free accelerator ZBPD-50, 15 parts of mercapto compound HDT, 1 part of initiator AIBN, 5 parts of zinc oxide, 1 part of stearic acid, 8 parts of foaming agent OBSH, and 20 parts of paraffin oil were added to a mixer in sequence. After mixing, extrusion molding, vulcanization and foaming processes, foamed EPDM samples were obtained.

[0086] Comparative Example 10: 100 parts of ethylene propylene diene monomer (EPDM), 25 parts of modified alkali lignin treated with RDES system, 35 parts of carbon black (N660), 1.0 part of sulfur, 4 parts of nitrosamine-free accelerator ZBPD-50, 5 parts of zinc oxide, 1 part of stearic acid, 7 parts of foaming agent OBSH, and 25 parts of paraffin oil were added to a mixer in sequence. After mixing, extrusion molding, vulcanization and foaming processes, foamed EPDM samples were obtained.

[0087] Comparative Example 11: Four solids—dried choline chloride (ChCl, 0.2 mol), HBD-1 (0.3 mol), urea (0.1 mol), and alkali lignin powder (15.7 g)—were directly added to a 500 mL sealed reactor. Stirring was started, and the temperature was raised to 100 °C. The reaction was carried out with vigorous stirring for 3 hours. Subsequent product processing and compound preparation were the same as in Example 1, yielding foamed EPDM samples.

[0088] Comparative Example 12: RDES Preparation: ChCl (0.2 mol), DOPO (0.3 mol), and urea (0.1 mol) were blended and DES was prepared at 100 °C. Subsequent product processing and compound preparation were the same as in Example 1, resulting in foamed EPDM samples.

[0089] Comparative Example 13: Conventional binary DES was prepared by blending ChCl (0.2 mol) and urea (0.4 mol, i.e., ChCl:Urea = 1:2 molar ratio) at 100 °C. Subsequent lignin modification and adhesive preparation were the same as in Example 1, resulting in foamed EPDM samples.

[0090] The relevant experimental data are recorded in the table below: serial number Density (g / cm³) Foaming ratio Compression set (%) Tensile strength (MPa) Elongation at break (%) Cell uniformity CV (%) Odor rating LOI (%) UL-94 Low temperature rebound retention rate (%) Hot air aging strength retention rate (%) Total VOCs (μg / m³) Example 1 0.62 2.2 25 6.2 260 9.1 2.8 29 V-0 88 90 180 Example 2 0.62 2.2 28 6 255 9.8 2.9 28.8 V-0 86 89 195 Example 3 0.63 2.1 38 5.4 240 12.5 2.8 28.9 V-0 85 88 185 Example 4 0.68 2 32 6.5 280 10.2 3.3 28.5 V-1 82 86 280 Example 5 0.58 2.4 30 5.8 250 9.5 2.9 29.5 V-0 87 89 210 Example 6 0.69 1.9 28 6.8 230 11 3.4 28.2 V-1 80 85 310 Example 7 0.65 2.1 26 6.4 210 10.8 3 29.2 V-0 83 87 220 Example 8 0.66 2 31 6.1 270 9.9 2.9 30.1 V-0 85 88 200 Example 9 0.62 2.2 26 6.3 265 9.3 2.9 28.9 V-0 87 91 190 Example 10 0.62 2.2 27 6 245 10.5 3.1 28.8 V-0 86 93 240 Example 11 0.63 2.1 24 6 250 9.6 2.4 29 V-0 85 96 120 Example 12 0.68 1.9 26 6.2 280 10.1 2.5 28.4 V-1 82 95 135 Example 13 0.6 2.3 25 5.8 265 9.8 2.4 29.3 V-0 84 96 125 Example 14 0.65 2.1 40 5.1 220 14 3.2 27.5 V-1 75 80 250 Example 15 0.64 2.1 45 4.8 235 15.2 3 28 V-1 78 82 230 Example 16 0.63 2.1 48 5.9 250 18.1 2.9 28.6 V-1 80 84 200 Example 17 0.7 1.8 42 6.6 260 16.5 3 32 V-0 79 85 210 Example 18 0.65 2.1 35 5.5 230 11.5 3.1 32.5 V-0 81 83 260 Example 19 0.68 2 38 5.3 225 12 3.2 34 V-0 78 81 280 Example 20 0.75 1.8 45 6.7 150 22.5 2.5 30.5 V-0 70 92 130 Example 21 0.82 1.6 52 4.5 180 28 2.2 31 V-0 75 91 110 Example 22 0.78 1.7 42 6.6 160 21 2.3 30.2 V-0 72 97 105 Example 23 0.78 1.7 43 6.5 155 21.8 2.3 30.4 V-0 71 97 110 Example 24 0.64 2.1 26 6.1 245 9.4 2.9 29.5 V-0 86 89 215 Example 25 0.69 1.9 29 5.7 270 10.5 2.6 28.8 V-1 83 94 145 Example 26 0.65 2.1 25 5.9 240 9.9 2.5 29.2 V-0 84 95 130 Comparative Example 1 0.85 1.6 48 5.5 295 25.8 4.5 26.1 HB 25 75 865 Comparative Example 2 1.25 N / A 18 10.5 450 N / A 3.8 27.2 HB 65 85 450 Comparative Example 3 0.63 2.1 55 4.2 210 22.4 2.9 28.8 V-1 70 80 200 Comparative Example 4 0.62 2.2 30 6.8 290 10.5 3.9 28.5 V-0 85 88 550 Comparative Example 5 0.64 2.1 62 3.5 190 28.1 3.1 28 HB 65 78 240 Comparative Example 6 0.65 2 70 3.1 160 35.5 3.2 27.8 HB 60 76 260 Comparative Example 7 0.8 1.7 65 3.8 150 30.2 2.6 30 V-1 68 81 150 Comparative Example 8 0.63 2.1 42 4.9 230 15 2.9 28.5 V-1 80 86 210 Comparative Example 9 0.75 1.8 92 1.5 85 45 4.2 27.5 HB 60 52 670 Comparative Example 10 0.7 1.9 38 6.6 200 18.5 2.9 29.8 V-0 78 88 230 Comparative Example 11 0.68 2 68 3.2 200 32 3 28.4 HB 66 77 220 Comparative Example 12 0.65 2.1 58 3.9 220 25.6 3.5 28.6 V-1 71 82 350 Comparative Example 13 0.63 2.1 45 4.6 240 16.2 2.9 28.8 V-0 82 87 190 Please refer to Example 1 and Comparative Example 1. Compression set is a key indicator for evaluating the resilience and sealing reliability of sealing materials under long-term pressure. Test data shows that under experimental conditions of 80℃×96h, the compression set of Example 1 is only 25%; in contrast, the compression set of Comparative Example 1 under milder conditions (70℃×72h) is as high as 48%. The data indicates that the composite material described in this invention has superior dimensional stability under high-temperature and long-term compression conditions. The mechanism is as follows: the alkali lignin modified with RDES, with its rigid benzene ring skeleton, constructs a microscale physical support network in the EPDM matrix. This network effectively distributes compressive stress and significantly inhibits the creep and collapse of foaming pores under thermal load, thereby solving the problem of insufficient heat relaxation resistance of traditional carbon black reinforcement systems.

[0091] To assess the service stability of sealing materials in cold environments, the low-temperature rebound performance of two materials was compared. Example 1 maintained an 88% rebound rate at -40°C, demonstrating good rubber elasticity; while Comparative Example 1 exhibited a rebound retention rate of less than 50%, displaying typical brittle fracture characteristics. This is mainly attributed to the high carbon black content (up to 120 parts) in Comparative Example 1, which significantly restricted the movement of EPDM molecular chain segments, leading to an increase in the glass transition temperature (Tg) and loss of low-temperature flexibility. This invention, by introducing functionalized modified alkali lignin to replace part of the carbon black, effectively maintains the degree of freedom of movement of the matrix polymer chain segments at low temperatures while ensuring reinforcement, thus significantly improving the low-temperature resistance of the material. Furthermore, the higher hot air aging strength retention rate of Example 1 also confirms that this system has superior thermal oxidation stability.

[0092] In terms of odor level and total VOC, Example 1 (grade 2.8 / 180 μg / m³) has a significant advantage over Comparative Example 1 (grade 4.5 / 865 μg / m³). High-filling-content ordinary carbon black, due to its large specific surface area, easily adsorbs and slowly releases small-molecule organic compounds generated during processing, which is a major factor leading to excessive VOC levels in traditional formulations. This invention reduces the amount of carbon black used and introduces modified lignin treated and purified using an RDES system, thereby reducing the volatile organic compound content from the source of the formulation, meeting the automotive industry's requirements for low-odor, low-VOC materials.

[0093] While achieving the aforementioned functional improvements, Example 1 exhibited a higher tensile strength (6.2 MPa) than Comparative Example 1 (5.5 MPa), and its cell uniformity CV value (9.1%) was significantly lower than that of Comparative Example 1 (25.8%). This indicates that RDES-modified lignin not only improved the interfacial compatibility between the filler and the matrix but also promoted uniform nucleation and growth of cells during the foaming process, avoiding stress concentration and cell structure defects caused by filler agglomeration.

[0094] In summary, compared with traditional high-filler carbon black systems, the RDES-modified alkali lignin / carbon black synergistic system adopted in this invention has achieved significant optimization in compression set, low-temperature resistance, and environmental protection indicators, proving the effectiveness of the technical solution in improving the overall performance of foamed EPDM sealing materials.

[0095] Furthermore, we comprehensively analyzed Example 1 and Comparative Example 3, the difference being whether the alkali lignin was treated with RDES. Data showed that the compression set of Example 1 was 25%, while that of Comparative Example 3 was as high as 55%, indicating significant performance degradation. The fact that the introduction of unmodified alkali lignin resulted in worse compression set performance than the traditional formulation (Comparative Example 1, 48%) demonstrates that unmodified lignin played a negative role in the system. The mechanism lies in the inherent thermodynamic incompatibility between alkali lignin, as a polar natural polymer, and the non-polar EPDM matrix. In Comparative Example 3, the unmodified lignin was dispersed in the matrix as micron-sized aggregates, forming a weak two-phase interface. During foaming, these aggregates not only failed to effectively stabilize the cell walls but also became inducing points for cell coalescence or rupture, as evidenced by the deteriorated cell uniformity CV value. In high-temperature compression tests, these weak interfaces could not transfer stress or provide effective support for the cell structure, leading to severe permanent deformation.

[0096] Mechanical testing further confirmed the aforementioned interface problem. The tensile strength and elongation at break of Example 1 were 6.2 MPa and 260%, respectively, while those of Comparative Example 3 were only 4.2 MPa and 210%. In polymer composite theory, filler agglomerates typically act as stress concentration points, initiating and propagating microcracks when the material is subjected to external forces, leading to macroscopic failure at relatively low stress levels. The mechanical properties of Comparative Example 3 fully conform to this theory. Conversely, the superior mechanical properties of Example 1 indicate that the RDES modification process successfully solved this interface incompatibility problem. We hypothesize that RDES, as an excellent dissolving / swelling medium, can effectively open the aggregated structure of alkali lignin, exposing more active functional groups (such as phenolic hydroxyl groups), and forming a transition layer on its surface with affinity to the EPDM matrix through hydrogen bonding and other interactions. This transition layer greatly enhances the interfacial interaction forces, allowing stress to be effectively transferred from the matrix to the reinforcing phase, thereby significantly improving the overall mechanical properties of the composite material. In hot air aging tests, the strength retention rate of Example 1 was 90%, also superior to the 80% of Comparative Example 3. This indicates that the weak interface present in Comparative Example 3 will become a weak link in degradation under thermo-oxidative aging conditions, accelerating the decline of material properties. In contrast, the strong interface formed in Example 11 helps to inhibit crack propagation and improves the long-term service stability of the material.

[0097] Further analysis of Example 1 and Comparative Example 4 revealed that, based on mechanical property data, Comparative Example 4 exhibited higher tensile strength (6.8 MPa), slightly higher than Example 1 (6.2 MPa). This aligns with the conventional understanding that silane coupling agents achieve efficient stress transfer by forming covalent chemical bonds between the filler and the polymer matrix. However, in the core functional indicator of greatest interest to this invention—high-temperature compression set—Example 1 (25%) outperformed Comparative Example 4 (30%). This indicates that while silane coupling agents can construct extremely strong interfacial bonds, the interfacial network formed by the RDES-modified system is more advantageous in suppressing cell creep at high temperatures. This may be attributed to the unique interfacial layer formed on the surface of RDES-modified lignin, which maintains high modulus and stability at high temperatures, thus providing more durable physical support for the cells.

[0098] Furthermore, Example 1 exhibits an odor rating of 2.8 and a total VOC content of 180 μg / m³, both at excellent levels. In stark contrast, Comparative Example 4 has an odor rating as high as 3.9 and a total VOC content of 550 μg / m³, far exceeding the application standards for modern automotive interior materials. The mechanism behind this phenomenon may be that during surface treatment and subsequent rubber processing, the alkoxy groups of the silane coupling agent undergo hydrolysis, inevitably releasing corresponding small-molecule alcohols (such as ethanol). These volatile alcohols are the direct cause of the deterioration in odor and VOC levels. However, the RDES system modification process of this invention does not involve the generation of such byproducts, and the final product undergoes thorough washing, fundamentally ensuring the low volatility of the material.

[0099] Please refer to the data from Example 1, Comparative Example 13, Comparative Example 8, and Comparative Example 12. The data from Comparative Example 13 show that although the core performance indicators of the material were improved after lignin treatment with conventional binary DES, there was still a significant gap compared with Example 1. This indicates that conventional DES alone is insufficient to achieve the technical effects described in this invention, and the introduction of the functional hydrogen bond donor HBD-1 is the key factor for improving the material performance.

[0100] Furthermore, the performance data of Comparative Example 8 (using glycerol) and Comparative Example 12 (using DOPO) were significantly worse than those of Example 1. This indicates that the superior effect of HBD-1 does not stem from a simple hydrogen bond donor function or a single DOPO structure, but rather from its unique molecular configuration as a specific addition product of DOPO and GMA. We speculate that its mechanism of action may be as follows: the rigid aromatic ring structure of DOPO in the HBD-1 molecule can strongly interact with the benzene ring units of lignin through supramolecular interactions such as π-π stacking; simultaneously, the flexibility introduced by the GMA segment and the hydroxyl groups generated after the addition reaction provide effective hydrogen bond sites. These two effects work synergistically to endow the lignin surface with higher interfacial and thermal stability during the modification process, which is evidenced by the superior heat-air aging strength retention of Example 1 compared to Comparative Example 13.

[0101] To investigate the effect of modified alkali lignin dosage on material properties, we examined a series of samples with different lignin contents in a sulfur vulcanization system, including Example 4 (5 parts), Example 1 (10 parts), Example 24 (15 parts), and comparative examples 10 (25 parts) and 20 (60 parts), which exceeded this range. Experimental data showed that within the range of 5–15 parts, the material maintained low compression set (25–32%) while exhibiting excellent toughness (elongation at break 245–280%) and a uniform cell structure (CV value 9.1–10.2%). Example 1 (10 parts) showed the best overall performance. We hypothesize that within the appropriate addition range of 5–15 parts, a synergistic reinforcing effect dominates. The RDES-modified alkali lignin particles can be uniformly dispersed, forming a three-dimensional, rigid-flexible hybrid filler network together with EPDM molecular chains and carbon black particles. This network provides strong physical support to the cell walls during high-temperature compression, thereby significantly reducing permanent compression deformation; during tensile processes, it can work with carbon black to improve the strength and modulus of the material through effective stress transfer and energy dissipation mechanisms.

[0102] However, once the amount of lignin exceeds 15 parts, negative effects gradually emerge and become dominant. As shown in Comparative Example 10 (25 parts), the processing performance of the material begins to deteriorate, resulting in a sharp decrease in cell uniformity to 18.5%, a loss of toughness (elongation at break drops to 200%), and a corresponding increase in core compression set to 38%. When the amount is further increased to 60 parts (Example 20), the material exhibits a significant brittle transition, with an elongation at break of only 150% and severely uneven cell structure (CV value 22.5%). At this point, although the tensile strength is relatively high (6.7 MPa), its most critical properties as an elastic sealing material—compression set and toughness—have completely failed.

[0103] Carbon black, as a synergistic reinforcing filler, also significantly impacts the final performance. In a system with approximately 10 parts alkali lignin, comparing Examples 5 (30 parts carbon black), 1 (40 parts carbon black), and 6 (50 parts carbon black), it can be seen that within the range of 30-50 parts, the materials exhibit good mechanical properties and functionality. At lower carbon black content (30 parts), the material shows relatively better low-temperature performance and environmental indicators (odor / VOC); while at higher carbon black content (50 parts), the material's ultimate tensile strength (6.8 MPa) reaches its peak. Example 1 (40 parts) achieves the optimal balance among various properties.

[0104] The above conclusions regarding the optimal formulation range were also verified in the click chemistry vulcanization system. By comparing Example 25 (5 parts lignin), Example 11 (10 parts lignin), and Example 26 (15 parts lignin), it can be seen that in the click chemistry system, a lignin dosage range of 5 to 15 parts is also a guarantee for obtaining excellent overall performance.

[0105] Finally, we compare Example 1 with Examples 18 and 19. Example 1 achieved a limiting oxygen index (LOI) of 29.0% and obtained a V-0 rating in the UL-94 vertical burning test. In contrast, conventional EPDM / carbon black composites (such as Comparative Example 1, with an LOI of 26.1% and a UL-94 HB rating) are typically flammable. We speculate that the inherent flame retardancy of Example 1 is primarily attributed to the chemical structure of the novel functional hydrogen bond donor HBD-1. HBD-1 is an addition product of DOPO and GMA, and the DOPO group introduced into its molecule is a highly efficient phosphorus-containing gas-phase flame retardant element. During RDES modification, HBD-1 may be partially grafted or physically adsorbed onto the lignin surface, thereby uniformly introducing flame-retardant functional groups into the final composite material—an unexpected technological gain. Furthermore, as shown in Examples 18 and 19, adding small amounts of DOPO or APP to the base formulation further increased the limiting oxygen index (LOI) of the materials to 32.5% and 34.0%, respectively. This indicates that the composite material system of the present invention has good compatibility with phosphorus-containing flame retardants and can achieve further improvement in flame retardant performance through conventional technical means.

[0106] However, as a non-reinforcing functional filler, the introduction of flame retardants inevitably affects the physical properties of the material. Data shows that compared to Example 1 (compression set 25%, tensile strength 6.2 MPa), the compression set of Examples 18 and 19 increased to 35% and 38%, respectively, while the tensile strength decreased accordingly to 5.5 MPa and 5.3 MPa. This performance trade-off is consistent with the basic principles of composite materials, namely the "dilution effect" of functional fillers on the matrix and reinforcing network. However, even after adding flame retardants, the compression set performance of Examples 18 and 19 was still significantly better than the conventional formulation (Comparative Example 1, 48%).

[0107] In summary, this invention discloses a high-performance, low-odor foamed EPDM rubber composite material and its preparation method, aiming to fundamentally solve the industry pain points of traditional EPDM sealing materials, such as large compression set and easy failure of sealing performance under high-temperature conditions. The core of this invention lies in firstly preparing a functional hydrogen bond donor (HBD-1) with both a rigid aromatic ring structure and flexible segments by reacting a functional molecule containing a DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) group with glycidyl methacrylate (GMA). Subsequently, this HBD-1 is pre-assembled with choline chloride and urea at a specific temperature into a ternary reactive deep eutectic solvent (RDES). This RDES is then used as a highly efficient liquid-phase reaction medium for surface modification of preferred alkali lignin. We hypothesize that the mechanism lies in the effective opening of the aggregated structure of lignin by RDES, while HBD-1 molecules, through synergistic effects such as π-π stacking and hydrogen bonding, construct an interface layer on the lignin surface that exhibits high thermal stability and good compatibility with the EPDM matrix. By compounding this modified alkali lignin (5-15 parts) with carbon black (30-50 parts), a rigid-flexible microscopic hybrid filler network is formed within the EPDM matrix. This network not only provides strong physical support for the foaming pores, effectively inhibiting creep and collapse at high temperatures, thus significantly reducing compression set, but also endows the material with excellent low-temperature resistance, intrinsic flame retardancy, and extremely low VOC / odor release.

[0108] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the embodiments of the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A foamed EPDM material, characterized in that, Prepared from the following raw materials in parts by weight: Ethylene propylene diene rubber (EPDM) 100 parts; Alkaline lignin modified by ternary reactive deep co-solvent (RDES) 5-20 parts; Reinforcing filler 20-50 parts; Vulcanization system 1-45 parts; Foaming agent 5-10 parts; The ternary reactive deep co-solvent (RDES) is composed of choline chloride, functional hydrogen bond donor HBD-1 and urea in a molar ratio of 1:(1.0-2):0.3-1.

2. The foamed EPDM material of claim 1, wherein, The functional hydrogen bond donor HBD-1 is the addition reaction product of a compound containing a DOPO group and a compound containing an epoxy group.

3. The foamed EPDM material of claim 2, wherein, The compound containing a DOPO group is 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), and the compound containing an epoxy group is glycidyl methacrylate (GMA).

4. The foamed EPDM material of claim 1, wherein, The reinforcing filler is selected from: (1) carbon black in an amount of 20-50 parts; (2) white carbon black in an amount of 20-50 parts; or (3) a combination of carbon black and white carbon black, wherein the total amount of carbon black and white carbon black is 20-50 parts.

5. The foamed EPDM material of claim 1, wherein, The vulcanization system is selected from: (1) a sulfur vulcanization system including sulfur, accelerators and activators; or (2) a click chemistry vulcanization system including a mercapto compound 20-40 parts and an initiator 1-3 parts.

6. The foamed EPDM material of claim 5, wherein, The mercapto compound is selected from one or more of 1,6-hexanedithiol (HDT), pentaerythritol tetra(3-mercaptopropionate) (PETMP) or 1,8-octanedithiol (ODT).

7. The foamed EPDM material of claim 1, wherein, The alkaline lignin modified by RDES is obtained by contacting alkaline lignin with RDES at 80-120℃ for 1-5 hours, and then washing with water and alcohol and drying.

8. A process for the preparation of a foamed EPDM material as claimed in any one of claims 1 to 7, characterized in that, Comprising the following steps: S1: preparing the functional hydrogen bond donor HBD-1; S2: blending the HBD-1 with choline chloride and urea under heating and stirring conditions to form a uniform ternary reactive deep co-solvent (RDES) liquid phase reaction medium; S3: adding alkaline lignin to the RDES for surface modification reaction to obtain modified alkaline lignin; S4: preparing the foamed EPDM material by mixing the modified alkaline lignin with reinforcing filler, ethylene propylene diene rubber and other additives through banburying, extrusion molding and high temperature vulcanization foaming process.

9. The production method according to claim 8, characterized by, The step S1 comprises: adding the compound containing a DOPO group to the compound containing an epoxy group for addition reaction to prepare the functional hydrogen bond donor HBD-1.

10. A weather strip, characterized by Made of the foamed EPDM material according to any one of claims 1-7. Made of the foamed EPDM material according to any one of claims 1-7.

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