Low-temperature-resistant ethylene propylene diene monomer composition and preparation method thereof

Abstract

The invention discloses a low-temperature-resistant ethylene propylene diene monomer composition and a preparation method thereof, and belongs to the technical field of rubber composite materials. The composition is based on raw ethylene propylene diene monomer, and comprises linear low-molecular-weight EPDM, a saturated fatty acid diester low-temperature modifier, a peroxide vulcanizing agent, an auxiliary vulcanizing agent, a reinforcing filler, an active agent, an anti-aging agent and a processing aid in a specific proportion. The key point is that 40-60 phr of linear low-molecular-weight EPDM and 20-30 phr of a low-temperature modifier are synergistically plasticized, and 0.2-0.4 phr of an assistant cross-linking agent TAIC and 3-5 phr of peroxide are matched to form a dual vulcanization system. During preparation, a two-stage mixing process is adopted, and the final mixing temperature is mainly controlled to be less than or equal to 85 DEG C. The brittleness temperature of the vulcanized rubber is less than or equal to-62 DEG C, the tensile strength retention rate at-40 DEG C is more than or equal to 80%, and the compression set (-40 DEG C * 72h) is less than or equal to 35%.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of rubber composites, and particularly relates to a low-temperature-resistant ethylene-propylene-diene rubber composition and a preparation method thereof. BACKGROUND

[0002] The rubber sealing material in the fields of aerospace, polar equipment and the like is required to have severe low-temperature performance (brittleness temperature ≤-60℃). The traditional EPDM rubber is limited by the glass transition temperature (Tg≈-55℃), and has insufficient low-temperature elasticity and anti-brittle cracking capacity, which easily leads to sealing failure and causes safety accidents. Although the amount of the plasticizer is simply increased in the prior art, the low-temperature performance can be improved, but the crosslinking density is reduced, the mechanical performance is deteriorated, and the high-temperature exudation problem occurs.

[0003] CN112280143A adopts liquid EPDM plasticization, which improves the low-temperature toughness, but the molecular weight distribution is wide, the compatibility with the base EPDM is poor, and uneven mixing and vulcanization lag are easily caused. JP2020153009A uses a polyhydric alcohol ester low-temperature modifier, but the high-temperature is volatile, the durability is poor, and the low-temperature performance is significantly attenuated after long-term use. US20210017561A1 attempts to compound a vulcanization system to optimize the low-temperature compression deformation, but the improvement on the brittleness temperature is limited, and the process is complex.

[0004] It is an industry problem to solve the contradiction between the low-temperature resistance and the high strength and heat resistance. A new type of modifier and vulcanization system synergistic technology need to be developed: the low-temperature modifier must have high boiling point, low volatility and excellent EPDM compatibility; the vulcanization system needs to consider the crosslinking efficiency and network flexibility. Accordingly, the application designs a low-temperature modifier with a specific structure, combines linear EPDM pre-dispersion and controllable vulcanization process, and realizes a breakthrough in comprehensive performance. SUMMARY

[0005] To solve the contradiction between the low-temperature resistance and the high strength and heat resistance.

[0006] To solve the above problems, the application provides the following technical scheme: A low-temperature-resistant ethylene-propylene-diene rubber composition, characterized in that it comprises 100 parts by weight of ethylene-propylene-diene rubber, 40-60 phr of linear low-molecular-weight EPDM, 20-30 phr of a low-temperature modifier, 3-5 phr of a peroxide vulcanizing agent, 0.2-0.4 phr of an auxiliary crosslinking agent, 30-50 phr of carbon black N550, 3-5 phr of active agent zinc oxide, 1-2 phr of anti-aging agent 445, 1-2 phr of stearic acid and 5-10 phr of paraffin oil.

[0007] Preferably, the linear low-molecular-weight EPDM has a Mooney viscosity [ML(1+4)125℃] of 25±3, an ethylene content of 48-52wt%, and an ENB content of 6-8wt%.

[0008] Preferably, the low-temperature modifier is a complex of di(2-ethylhexyl) sebacate and isooctyl palmitate in a mass ratio of 2:1 to 1:1.

[0009] Preferably, the peroxide vulcanizing agent is 1,1-di(tert-butyl peroxy)-3,3,5-trimethylcyclohexane with a purity of ≥98%.

[0010] Preferably, the co-crosslinking agent is triallyl isocyanurate (TAIC) with a particle size of ≤10 μm.

[0011] Preferably, the carbon black N550 has a DBP oil absorption value of 110-115 ml / 100g and a CTAB specific surface area of 38-42 m 2 / g.

[0012] A preparation method of a low-temperature-resistant EPDM composition, characterized in that it comprises the following steps: S1: One-stage mixing, EPDM, linear EPDM, carbon black, zinc oxide, stearic acid, paraffin oil, antioxidant 445 are mixed in a Banbury mixer at a speed of 40-60 rpm, and the discharge temperature is 145-155℃; S2: Two-stage mixing, the one-stage mixed rubber is cooled to 80℃, and then peroxide, co-crosslinking agent, and low-temperature modifier are added, the speed is 20-30 rpm, and the discharge temperature is ≤85℃.

[0013] Preferably, the one-stage mixing time is 5-7 min, and the two-stage mixing time is 2.5-3.5 min.

[0014] Preferably, the low-temperature modifier in S2 is added in the last 90 seconds of two-stage mixing.

[0015] Preferably, the glass transition temperature of the vulcanized rubber of the composition is ≤-62℃, and the compression permanent deformation at -40℃×72h is ≤35%.

[0016] The low-temperature-resistant EPDM composition and the preparation method thereof have the following effects and advantages: 1. In the present patent, the DSC test shows that the Tg is as low as -64.8℃, which is significantly lower than that of the comparative example (-55.3℃), because the molecular chains of the low-temperature modifier penetrate between the EPDM molecules to expand the free volume, and the linear EPDM improves the low-temperature activity of the molecular chains.

[0017] 2. In the present patent, the tensile strength retention rate at -40℃ is as high as 82%, the low-temperature modifier inhibits the freezing of the molecular chains, and the flexibility of the vulcanized network inhibits the brittle fracture at low temperature.

[0018] 3, The compression permanent deformation of the patent is only 32.1% at -40℃x72h, and the compression permanent deformation of the comparative example is 48.7%, which is attributed to the uniform and dense crosslinking network formed by the double vulcanization system, and the elastic recovery force is improved.

[0019] 4, The pre-dispersed linear EPDM and the segmented mixing process of the patent make the Mooney viscosity [ML(1+4)125℃] of the rubber stable at 35±2, and ensure that the scorch time is >25min. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a flow chart of a low-temperature-resistant EPDM composition and a preparation method thereof in the present application. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, and not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application, It should be noted that, in this paper, relationship terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations, and the term "include", "contain" or any other variant is intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment. Without more limitation, the elements defined by the statement "include" do not exclude the presence of other identical elements in the process, method, article or equipment including the elements.

[0022] Example 1 Reference Figure 1 The present application provides a low-temperature-resistant EPDM composition and a preparation method thereof, which is suitable for the technical field of rubber composites and includes the following implementation contents. Experimental purpose: A low-temperature-resistant EPDM composition and a preparation method thereof verify the synergistic optimization effect of a specific proportion of linear low-molecular-weight EPDM and a compounded low-temperature modifier on the low-temperature performance of EPDM.

[0023] Experimental raw materials: Base EPDM: 100 phr (Mooney viscosity ML(1+4)125°C = 60 ± 5, ethylene content 52 wt%, ENB content 5.2 wt%), linear low molecular weight EPDM: 50 phr (Mooney viscosity ML(1+4)125°C = 25 ± 3, ethylene content 50 wt%, ENB content 7 wt%), peroxide BIPB: 4 phr (1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane, purity ≥ 98%), co-agents TAIC: 0.3 phr (triallyl isocyanurate, particle size D50 = 8 μm), di(2-ethylhexyl)sebacate: 20 phr, isooctyl palmitate: 10 phr, carbon black N550: 45 phr (DBP oil absorption value 113 ml / 100g, CTAB specific surface area 40 m 2 / g), zinc oxide: 5 phr (active agent, purity 99.7%), stearic acid: 1.5 phr, antioxidant 445: 1.5 phr (N,N'-di(2,2,6,6-tetramethyl-4-piperidyl)-1,6-hexanediamine), paraffin oil: 8 phr.

[0024] Experimental equipment: Internal mixer (1.5L), flat vulcanizing machine, low-temperature brittleness tester, electronic tensile testing machine, compression set tester, differential scanning calorimeter.

[0025] Experimental procedure: S1: One-stage mixing, base EPDM and linear EPDM were fed, mixed at 40 rpm for 60 seconds until uniform, N550 carbon black, zinc oxide, stearic acid, antioxidant 445, paraffin oil were added, the speed was increased to 55 rpm and mixed for 300 seconds, the rubber was discharged immediately when the temperature reached 150°C, and cooled to room temperature; S2: Two-stage mixing, the one-stage rubber was broken and fed into the internal mixer, the speed was 25 rpm and the temperature was increased to 80°C, BIPB and TAIC were added, mixed for 90 seconds, the compounded low-temperature modifier was added, mixed for 90 seconds until completely dispersed, and the discharge temperature was controlled ≤ 85°C; S3: Sulfurization molding, the rubber was pre-placed in the mold cavity, sulfurized at 160°C for 18 minutes, demolded, and then secondarily vulcanized in the oven at 150°C for 4 hours.

[0026] Experimental results: Details are shown in Table 1.

[0027] Table 1: Test results of Example 1 Example 1 A low temperature resistant EPDM composition and its preparation method, brittle temperature reached -64.8℃, glass transition temperature was -64.8℃, both deviation ≤2℃ consistent with nonlinear viscoelastic theory expectations, this phenomenon attributed to the synergistic effect of complex low temperature modifier: the straight chain alkyl (C10) of di(2-ethylhexyl) sebacate penetrated the intermolecular gap of EPDM, increased the free volume fraction, while the branched structure of isooctyl palmitate inhibited low temperature crystallization, resulting in a decrease in the activation energy of chain segment movement. 50 phr linear EPDM improved carbon black dispersibility, making the tensile strength retention rate at -40℃ reach 82%, and the optimized filler-rubber interface bonding inhibited the expansion of microcracks caused by stress concentration. The improvement of compression set (32.1%) was due to the dual vulcanization system, the tertiary butoxy free radicals generated by the decomposition of BIPB were efficiently captured by TAIC (0.3 phr), forming a network mainly composed of flexible C-C crosslinking bonds, and its short chain crosslinking structure still maintained the deformation recovery mechanism dominated by entropy elasticity at -40℃.

[0028] Example 2 This example provides a low temperature resistant EPDM composition and its preparation method, verifies the lower limit effect of low temperature modifier, including the following implementation content: Experimental purpose: A low temperature resistant EPDM composition and its preparation method, to explore the effect of reducing the amount of low temperature modifier to the lower limit (total amount 20 phr) on the low temperature performance of EPDM.

[0029] Experimental materials: Base EPDM: 100 phr (Mooney viscosity ML(1+4)125℃=60±5, ethylene content 52 wt%, ENB content 5.2 wt%), linear low molecular weight EPDM: 50 phr (Mooney viscosity ML(1+4)125℃=25±3, ethylene content 50 wt%, ENB content 7 wt%), peroxide BIPB: 4 phr (1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane, purity ≥98%), co-crosslinking agent TAIC: 0.3 phr (triallyl isocyanurate, particle size D50=8 μm), di(2-ethylhexyl) sebacate: 15 phr, isooctyl palmitate: 5 phr, carbon black N550: 45 phr (DBP oil absorption value 113 ml / 100g, CTAB specific surface area 40 m 2 / g), zinc oxide: 5 phr (active agent, purity 99.7%), stearic acid: 1.5 phr, antioxidant 445: 1.5 phr (N,N'-di(2,2,6,6-tetramethyl-4-piperidyl)-1,6-hexanediamine), paraffin oil: 8 phr.

[0030] Experimental steps: S1: One-stage mixing: base EPDM 100 phr + linear EPDM 50 phr → mixing at 40 rpm for 60 seconds; adding N550 carbon black 45 phr, zinc oxide 5 phr, stearic acid 1.5 phr, antioxidant 445 1.5 phr, paraffin oil 8 phr → mixing at 55 rpm for 300 seconds → binder removal temperature 150°C; S2: Two-stage mixing: After the first stage rubber compound is cooled to 80℃, it is put into the internal mixer and BIPB 4 phr + TAIC 0.3 phr are added → mixing at 25 rpm for 90 seconds; modifier (sebacate 15 phr + palmitate 5 phr) is added → mixing for 90 seconds → discharge temperature is 83℃; S3: Vulcanization process, primary vulcanization at 160℃×18min → secondary vulcanization at 150℃×4h.

[0031] Experimental results: See Table 2 for details.

[0032] Table 2: Test results of Example 2 Example 2: A low-temperature-resistant EPDM rubber composition and its preparation method. The brittle temperature rises to -59.2°C. A 33% reduction in modifier content reduces plasticization efficiency, lowers the free volume fraction, and restricts molecular segment motion, resulting in a glass transition temperature increase from -64.8°C to -60.5°C. This increases the activation energy of segment relaxation, and macroscopically manifests as an increased tendency toward low-temperature brittle fracture. The -40°C tensile strength drops to 12.8 MPa. The reduced sebacate ratio weakens the secondary bonding between polar groups and EPDM chains, resulting in uneven modulus distribution in localized microregions of the rubber matrix and reduced stress transfer efficiency. Furthermore, insufficient isooctyl palmitate weakens the ability to inhibit low-temperature crystallization and reduces crack propagation resistance. Tensile strength retention at -40°C dropped to 74%. Basic properties showed minimal change due to the stability of the crosslink density. However, increased modifier mobility at -40°C triggered a two-stage failure process: a) stress concentration points formed in the plasticizer-poor phase, inducing early silver crazes; b) increased molecular chain freezing increased yield strength, decreased ductility (elongation at break), and reduced fracture energy. Compression set increased to 36.5%, the average molecular weight between crosslinks increased, network regularity decreased, the entropic elastic contribution to deformation decreased, molecular chain frictional energy dissipation increased, and elastic recovery decreased. The Tg increased to -60.5°C. The insufficient concentration of low-molecular-weight plasticizer weakened the segmental lubrication effect, increasing the rotation barrier. The slope change point of the DSC heating curve dQ / dT shifted toward higher temperatures, broadening the transition range, confirming that the system was in a confined glass transition state.

[0033] Example 3 The embodiment provides a low-temperature-resistant EPDM rubber composition and a preparation method thereof, verifies the influence of an excess amount of a co-crosslinking agent, and includes the following implementation contents: Experimental purposes: A low-temperature-resistant EPDM rubber composition and a preparation method thereof, explore the negative effect of the amount of co-crosslinking agent TAIC exceeding the limit (0.6 phr) on the vulcanization network structure and low-temperature performance.

[0034] Experimental raw materials: Base EPDM: 100 phr (Mooney viscosity ML(1+4)125℃=60±5, ethylene content 52 wt%, ENB content 5.2 wt%), linear low molecular weight EPDM: 50 phr (Mooney viscosity ML(1+4)125℃=25±3, ethylene content 50 wt%, ENB content 7 wt%), peroxide BIPB: 4 phr (1,1-di(tert-butyl peroxy)-3,3,5-trimethylcyclohexane, purity≥98%), co-crosslinking agent TAIC: 0.6 phr (triallyl isocyanurate, particle size D50=8 μm), di(2-ethylhexyl) sebacate: 20 phr, isooctyl palmitate: 10 phr, carbon black N550: 45 phr (DBP oil absorption value 113 ml / 100g, CTAB specific surface area 40 m 2 / g), zinc oxide: 5 phr (active agent, purity 99.7%), stearic acid: 1.5 phr, antioxidant 445: 1.5 phr (N,N'-di(2,2,6,6-tetramethyl-4-piperidyl)-1,6-hexanediamine), paraffin oil: 8 phr.

[0035] Experimental steps: S1: One-stage mixing, base EPDM and linear EPDM are fed, 40 rpm mixing for 60 seconds until uniform, N550 carbon black, zinc oxide, stearic acid, antioxidant 445, paraffin oil are added, the speed is increased to 55 rpm and mixed for 300 seconds, the temperature reaches 150℃, and then the glue is discharged immediately, and cooled to room temperature; S2: Two-stage mixing, the one-stage glue is broken and fed into the internal mixer, the speed is 25 rpm and the temperature is increased to 80℃, BIPB and TAIC are added, mixed for 90 seconds, and the compound low-temperature modifier is added, mixed for 90 seconds until completely dispersed, and the discharge temperature is controlled to be less than or equal to 85℃; S3: Sulfurization forming, the glue is pre-placed in the mold cavity, 160℃ sulfurization for 18 minutes, and after demolding, the second-stage sulfurization is carried out in the oven at 150℃ for 4 hours.

[0036] Experimental results: details are shown in Table 3.

[0037] Table 3: Test results of Example 3 Example 3 A low temperature resistant EPDM composition and its preparation method, the brittle temperature is raised to -56.5℃, the excess TAIC increases the crosslinking density, the molecular weight between crosslinking points is reduced, the molecular chain segment movement is hindered, the Tg is significantly increased, the DSC secondary transition peak intensity is reduced, indicating that the local chain segment relaxation ability is lost. The tensile strength at -40℃ is increased to 16.8MPa, the high crosslinking density makes the material rigid, but the elongation at break is reduced, and the stress-strain curve shows the characteristics of brittle fracture (no obvious yield platform), and the crystal reinforcement effect masks the decrease of molecular chain activity. The tensile strength retention rate is increased to 97%, the high temperature tensile strength is inhibited by excessive crosslinking, and the decrease of low temperature (-40℃) strength is limited due to the freezing of chain segments, forming a false high retention rate, and the actual low temperature toughness is seriously degraded. The compression set is increased to 41.7%, the crosslinking network stress relaxation lag is intensified, the uneven crosslinking makes the proportion of effective elastic network decrease, and the compression deformation recovery ability decreases. The Tg is increased to -57.9℃, the excessive crosslinking shortens the molecular chain freedom, the free volume fraction is reduced, the DSC warming curve shows a wide glass transition, and the network topological constraint effect is verified to be strengthened.

[0038] Comparative Example 1 A traditional EPDM composition and its preparation method are provided, which highlights the innovative advantages of the present patent technology, including the following implementation contents: Experimental purposes: A traditional EPDM composition and its preparation method are provided, which highlights the innovative advantages of the present patent technology, including the following implementation contents:

[0039] Experimental raw materials: Base EPDM: 100 phr (Mooney viscosity ML(1+4)125℃=60±5, ENB 5.2 wt%), plasticizer: naphthenic oil 30 phr (kinematic viscosity at 40℃ 90 cSt, aromatic content ≤3%), vulcanizing agent: dicumyl peroxide (DCP) 3 phr, N550 carbon black 45 phr, zinc oxide 5 phr, stearic acid 1.5 phr, antioxidant 445 1.5 phr.

[0040] Experimental steps: S1: One-stage mixing, EPDM + naphthenic oil → 40 rpm mixing for 60 seconds; add carbon black, zinc oxide, stearic acid, antioxidant → 55 rpm mixing for 300 seconds → discharge temperature 150℃; S2: Two-stage mixing, one-stage rubber is cooled to 80℃ → add DCP → 25 rpm mixing for 180 seconds → discharge temperature 105℃; S3: Cure process, 160°C x t90 (15 min) → 150°C x 4h secondary cure.

[0041] Experimental results: Details are shown in Table 4.

[0042] Table 4: Test results of Comparative Example 1 Comparative Example 1 provides a traditional EPDM composition and its preparation method, with brittle temperature only -53.5°C, poor compatibility between naphthenic oil and EPDM, high temperature migration to the surface to form an oil film, insufficient effective plasticizing concentration, reduced free volume fraction, and severely limited low temperature activity of molecular chains. The tensile strength at -40°C drops sharply, and the loose crosslinking network formed by single DCP vulcanization intensifies the molecular chain slip under low temperature stress; the interface defects caused by naphthenic oil precipitation induce early fracture due to stress concentration, with elongation at break of only 110%. The tensile strength retention rate is 42%, and the strength at 23°C is maintained at 17.3 MPa due to plasticizing effect, but the viscosity of naphthenic oil increases sharply at -40°C, the glass transition of the rubber matrix is advanced, and the brittle-ductile transition zone disappears. The compression set is as high as 48.7%, the weak entropic elasticity caused by loose crosslinking network, and the naphthenic oil acting as a lubricant accelerates the irreversible displacement of molecular chains, resulting in reduced deformation recovery rate. The Tg is relatively high, and the low temperature modifier does not inhibit the crystallization of molecular chains, resulting in a clear cold crystallization peak at -45°C, the regular arrangement of EPDM segments, and the overlap of glass transition and crystallization melting peaks, resulting in a false high Tg detection value.

[0043] Example 1 provides a low temperature resistant EPDM composition and its preparation method, which significantly improves the low temperature performance of EPDM through the synergistic effect of complex low temperature modifier (di(2-ethylhexyl) sebacate and isooctyl palmitate) and linear low molecular weight EPDM. The brittle temperature is as low as -64.8°C, and the glass transition temperature (Tg) is the same, verifying the expectation of the nonlinear viscoelastic theory. The straight-chain alkyl structure of the complex modifier increases the free volume fraction of the molecular chain, and the branched structure inhibits low temperature crystallization, reducing the activation energy of chain segment movement. The 50 phr linear EPDM optimizes the dispersion of carbon black, with a tensile strength retention rate of 82% at -40°C, and the effective filler-rubber interface bonding effectively inhibits the propagation of microcracks. The compression set is 32.1%, and the flexible C-C crosslinking network formed by the BIPB / TAIC dual vulcanization system still maintains the deformation recovery mechanism dominated by entropic elasticity at low temperature.

[0044] Example 2 The lower limit of plasticizer was explored by reducing the total amount of low temperature modifier to 20 phr (sebacate 15 phr + palmitate 5 phr). The brittle temperature rose to -59.2 °C, and the Tg rose to -60.5 °C. The free volume fraction decreased, resulting in limited chain segment movement and decreased plasticizing efficiency. The tensile strength at -40 °C decreased to 12.8 MPa, and the increased migration rate of the modifier led to two-stage failure: stress concentration points formed in the plasticizer-poor phase, and the freezing of molecular chains exacerbated the decrease in ductility. The tensile strength retention rate was 74%, reflecting the decline in low temperature performance, and the compression set increased to 36.5%. The increase in molecular weight between crosslinking points led to a decrease in network regularity, and the deformation recovery ability decreased. The DSC curve showed that the system was in a state of restricted glass transition, and the chain segment relaxation ability was limited.

[0045] Example 3 The negative impact of excessive crosslinking on low temperature performance was revealed by adding an excess of co-crosslinking agent TAIC (0.6 phr). The brittle temperature rose to -56.5 °C, and the Tg rose to -57.9 °C. The increased crosslinking density by 38% led to severe hindering of molecular chain segment movement. The tensile strength at -40 °C was virtually high to 16.8 MPa (retention rate 97%), but the elongation at break decreased, showing brittle fracture characteristics. The compression set deteriorated to 41.7%, and the uneven crosslinking led to a decrease in the proportion of effective elastic network, and the deformation recovery ability decreased. The DSC curve showed that the glass transition interval was widened, indicating that the network topological constraint effect was strengthened, and the local chain segment relaxation ability was lost.

[0046] Comparative Example 1 The performance was significantly deteriorated using the traditional formulation of naphthenic oil plasticization and a single DCP vulcanization system. The brittle temperature was only -53.5 °C, and the insufficient effective plasticizing concentration due to high temperature migration of naphthenic oil led to a decrease in free volume fraction. The tensile strength at -40 °C dropped to 7.3 MPa (retention rate 42%), and the interfacial defects led to early fracture, with an elongation at break of only 110%. The compression set was as high as 48.7%, and the loose crosslinking network weakened the entropic elasticity, and the naphthenic oil lubrication accelerated the irreversible displacement of molecular chains. The Tg detection value was virtually high (-55.3 °C), and there was no modifier to inhibit crystallization, and a cold crystallization peak appeared at -45 °C, which exacerbated the low temperature brittleness due to the regularity of chain segment arrangement.

[0047] Those of ordinary skill in the art can be aware that, in combination with the examples described in the embodiments disclosed in the present text, the modules and algorithm steps of each example can be realized in electronic hardware or a combination of computer software and electronic hardware. Whether the functions are realized in hardware or software depends on specific application and design constraints of the technical solutions. Those of ordinary skill in the art can use different methods to realize the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0048] In addition, each function module in each embodiment of the present application can be integrated in one processing module, or each module can exist physically separately, or two or more modules can be integrated in one module.

[0049] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered in the protection scope of the present application, therefore, the protection scope of the present application should be subject to the protection scope of the claims.

[0050] Finally: the above is only a preferred embodiment of the present application, and is not used to limit the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection of the present application.

Claims

1. A low temperature resistant EPDM rubber composition, characterized in that , comprising 100 parts by weight of EPDM rubber, 40-60 phr of linear low molecular weight EPDM, 20-30 phr of low temperature modifier, 3-5 phr of peroxide vulcanizing agent, 0.2-0.4 phr of auxiliary cross-linking agent, 30-50 phr of carbon black N550, 3-5 phr of active agent zinc oxide, 1-2 phr of antioxidant 445, 1-2 phr of stearic acid, and 5-10 phr of paraffin oil.

2. A low-temperature resistant EPDM rubber composition according to claim 1, characterized in that: The linear low molecular weight EPDM has a Mooney viscosity [ML(1+4)125° C.] of 25±3, an ethylene content of 48-52 wt %, and an ENB content of 6-8 wt %.

3. The low-temperature resistant EPDM rubber composition according to claim 1, characterized in that: The low-temperature modifier is a compound of di(2-ethylhexyl) sebacate and isooctyl palmitate in a mass ratio of 2:1 to 1:

1.

4. The low-temperature resistant EPDM rubber composition according to claim 1, characterized in that: The peroxide curing agent is 1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane, and the purity is ≥98%.

5. The low-temperature resistant EPDM rubber composition according to claim 1, characterized in that: The auxiliary cross-linking agent is triallyl isocyanurate (TAIC), and the particle size is ≤10 μm.

6. The low-temperature resistant EPDM rubber composition according to claim 1, characterized in that: The carbon black N550 has a DBP oil absorption value of 110 to 115 ml / 100 g and a CTAB specific surface area of ​​38 to 42 m 2 / g.

7. A method for preparing a low-temperature resistant EPDM rubber composition, characterized in that: The following steps are involved: S1: One-stage mixing: EPDM, linear EPDM, carbon black, zinc oxide, stearic acid, paraffin oil, and antioxidant 445 are mixed in an internal mixer at a speed of 40-60 rpm and a binder removal temperature of 145-155°C. S2: Two-stage mixing. After the first-stage mixed rubber is cooled to 80℃, peroxide, co-crosslinking agent and low-temperature modifier are added. The speed is 20-30rpm and the discharge temperature is ≤85℃.

8. The method for preparing a low-temperature-resistant EPDM rubber composition according to claim 7, wherein: The first stage mixing time is 5 to 7 minutes, and the second stage mixing time is 2.5 to 3.5 minutes.

9. The method for preparing a low-temperature-resistant EPDM rubber composition according to claim 7, wherein: The low-temperature modifier in S2 is added within the last 90 seconds of the second-stage mixing.

10. The low-temperature resistant EPDM rubber composition according to claim 1, characterized in that: The glass transition temperature of the vulcanized rubber of the composition is ≤-62°C, and the compression permanent deformation at -40°C×72h is ≤35%.

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