Sorbate-enhanced thermoplastic vulcanizate-aluminum alloy hybrid joints, methods of making, and applications thereof

Abstract

The application discloses a sorbate reinforced thermoplastic vulcanized rubber-aluminum alloy heterogeneous joint and a preparation method and application thereof. The heterogeneous joint is prepared by stirring friction spot welding of the sorbate reinforced thermoplastic vulcanized rubber and aluminum alloy welding; the sorbate reinforced thermoplastic vulcanized rubber is prepared by adding a ternary ethylene-propylene-diene rubber into an open mill first, primary plasticizing, uniformly mixing and mulling metal oxide and sorbate to obtain a mixed rubber; then, polypropylene resin and an antioxidant are added into a closed mill first, the mixed rubber is added into the closed mill after the polypropylene resin and the antioxidant are melted, crosslinking agent is added after the mixed rubber is uniformly mixed, and dynamic vulcanization is carried out in a closed state. The sorbate reinforced thermoplastic vulcanized rubber-aluminum alloy heterogeneous joint prepared by the application has excellent mechanical strength, and the implementation process is simple, efficient, fast, green, environmentally-friendly and low in cost. The sorbate reinforced thermoplastic vulcanized rubber-aluminum alloy heterogeneous joint is suitable for replacing aluminum alloy in automobile lightweight manufacturing.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of heterostructures, in particular to a kind of sorbate enhanced thermoplastic vulcanized rubber-aluminum alloy heterogeneous joint and its preparation method, belong to thermoplastic composite and metal connection field. BACKGROUND

[0002] In recent years, with the increasing acceleration of economic development, the consumption of energy is increasing day by day, and the environmental protection work is facing great challenges. As an important part of energy saving and emission reduction in China, the light weight manufacturing of automobile can effectively alleviate the problems faced in the development process. There are many ways to achieve light weight of automobile, one of which is to replace part of the metal components with low-density polymer materials and weld them with metal to form a hybrid heterogeneous structure. The heterogeneous hybrid structure formed by metal material and polymer material can exert the unique advantages of different components, and can further reduce the weight of various parts and structural parts, which helps to achieve light weight.

[0003] Thermoplastic vulcanized rubber (TPV) is a kind of polymer material with high elasticity of rubber and processing characteristics of thermoplastic plastic, which has the characteristics of light weight, shock absorption and repeatable processing, and can be used as an ideal substitute for part of metal components. However, the polarity, linear expansion coefficient and shrinkage rate of TPV are quite different from those of metal, which makes the reactivity between them poor, the interface affinity weak, and it is difficult to connect directly by welding. Therefore, changing the interface properties of TPV, improving the reactivity and interface affinity between TPV and metal is very important to enhance the welding performance of TPV.

[0004] Chinese invention patent CN114410017A discloses a kind of TPV material and its preparation method and application, with EPDM, PP and SEBS as raw materials, dynamic vulcanization is carried out by using vulcanizing agent and vulcanization aid, interface modifier is added to improve interface compatibility, and part of polar resin is also added. The TPV prepared by the invention can be bonded together with polycarbonate (PC) and acrylonitrile-butadiene-styrene plastic (ABS), forming a cladding type heterogeneous structure. But the bonding strength of the TPV is at most 5.9 MPa, and the 300% tensile strength is only 3.2 MPa, which can only be used as the handle covering skin of electric tool polar base material, the covering skin of automobile lamp, etc., and cannot replace part of the metal as automobile structural parts.

[0005] Chinese invention patent CN103497429B discloses a kind of low odor TPV and its preparation method and application with ABS substrate secondary coating forming, with PP, EPDM, thermoplastic polyurethane elastomer as raw material, using vulcanizing agent and vulcanization aid to carry out dynamic vulcanization, also add filling oil and other fillers.The TPV prepared by the invention has the characteristics of low odor, can form heterogeneous structure with ABS secondary coating. SUMMARY

[0006] The present application aims to solve the problems of large difference between PP / EPDM thermoplastic vulcanized rubber material and metal in polarity, linear expansion coefficient and shrinkage, difficulty in direct connection by welding and low heterogeneous structure strength, and provides a sorbate enhanced thermoplastic vulcanized rubber-aluminum alloy heterogeneous joint with good welding performance, and the tensile strength, polarity and joint shear strength of the TPV material are excellent, the shear strength can reach 2.76-7.73 MPa, and the tensile strength can reach 12.83-23.48 MPa.

[0007] Another object of the present application is to provide the application of the sorbate enhanced thermoplastic vulcanized rubber-aluminum alloy heterogeneous joint in the lightweight manufacturing of automobiles instead of aluminum alloy.

[0008] The above technical objects of the present application are achieved by the following technical solutions:

[0009] A sorbate enhanced thermoplastic vulcanized rubber-aluminum alloy heterogeneous joint is characterized by being prepared by friction stir spot welding of sorbate enhanced thermoplastic vulcanized rubber and aluminum alloy; the sorbate enhanced thermoplastic vulcanized rubber is prepared by first adding EPDM in an open mill, preliminarily plasticizing, uniformly mixing metal oxide and sorbic acid, and then adding polypropylene resin and antioxidant in an internal mixer, mixing the rubber compound, adding the rubber compound after melting, uniformly mixing, and then adding crosslinking agent to obtain a dynamic vulcanized product under airtight condition; the raw material formula is composed of, by mass fraction:

[0010]

[0011] To further achieve the objects of the present application, preferably, the EPDM is ethylidene norbornene or dicyclopentadiene.

[0012] Preferably, the polypropylene resin is at least one of random copolymer type, syndiotactic copolymer type and homopolymer type polypropylene.

[0013] Preferably, the metal oxide is one of zinc oxide, magnesium oxide, sodium oxide and potassium oxide.

[0014] Preferably, the antioxidant is one or more of antioxidant 168, antioxidant 1076, antioxidant 1010, antioxidant 2246, antioxidant 1098 and antioxidant DLTP.

[0015] Preferably, the cross-linking agent is a peroxide vulcanizing agent.

[0016] Preferably, the peroxide vulcanizing agent is one or more of t-butyl peroxybenzoate, dicumyl peroxide, dibenzoyl peroxide, di-t-butyl peroxide, 2,4-dichlorobenzoyl peroxide and di-(t-butylperoxy isopropyl) benzene.

[0017] The method for preparing the sorbate reinforced thermoplastic vulcanized rubber-aluminum alloy heterogeneous joint comprises the following steps:

[0018] 1) Rubber mixing: plasticize the rubber on an open mill at room temperature; add sorbic acid and metal oxide, cut the rubber, roll it, and make a triangular package, mix uniformly, and obtain a sheet after cooling;

[0019] 2) Dynamic vulcanization: mix the polypropylene resin and antioxidant, and then add them to the internal mixer, control the temperature of the internal mixer at 180-185°C, and control the rotation speed at 60-90 rpm; melt the mixture, then add the mixed rubber, and mix until uniform; add the cross-linking agent, and dynamically vulcanize for 6-6.5 min in a closed state to obtain the sorbate reinforced thermoplastic vulcanized rubber.

[0020] 3) Stir friction spot welding: place one end of the aluminum alloy above the thermoplastic vulcanized rubber; lower the stir head from above the aluminum alloy; continue to lower the stir head by 0.5-2.5 mm after it contacts the surface of the aluminum alloy plate, maintain the current amount of lowering to spot weld, the process lasts for 10-45 s, and the stir head is raised to the initial position and stopped after the spot welding is completed.

[0021] Preferably, in step 1), the rubber is plasticized on the open mill for 5-14 times; the rubber is cut, rolled, and made into a triangular package for 3-4 times each.

[0022] In step 3), before welding, the one end of the aluminum alloy is placed above the thermoplastic vulcanized rubber and fixed on the operation table using a clamp; the diameter of the stir head is 5-20 mm, and the rotation speed is 1200-2000 rpm; the stir head is lowered from a height of 10-50 mm above the aluminum alloy.

[0023] The sorbate reinforced thermoplastic vulcanized rubber-aluminum alloy heterogeneous joint is used to replace aluminum alloy in the manufacturing of lightweight automobiles.

[0024] Compared with the prior art, the present application has the following advantages:

[0025] (1) The shear strength of the potassium sorbate reinforced thermoplastic vulcanizate-aluminum alloy heterogeneous joint prepared by the present application can reach 2.76-7.73 MPa, which can ensure the strength of the welding interface and the tensile strength of the TPV can reach 12.83-23.48 MPa. Compared with the bonding strength of 3-6 MPa and the tensile strength of 3-8 MPa of the current part of the clad heterogeneous structure, the present application has the characteristics of high specific strength and strong plasticity, which can meet the strength requirements of some automobile structural parts.

[0026] (2) The present application adds polar sorbate to prepare TPV materials, which not only improves the non-polarity and small melt strength of the original thermoplastic vulcanizate, but also enables the prepared TPV materials to be effectively connected together with aluminum alloy, thereby preparing a light thermoplastic-metal structure.

[0027] (3) The present application uses the friction stir spot welding process to prepare a light alloy-thermoplastic vulcanizate efficient heterogeneous joint, which has the advantages of simple welding process, short construction period (only a few minutes) and green environmental protection.

[0028] (4) The present application uses a low-toxic, cheap and easily available unsaturated carboxylic acid-sorbitol and its in-situ reaction formed metal salt as a reinforcing agent, a reaction compatibilizer and a co-crosslinking agent to modify the PP / EDPM thermoplastic vulcanizate with high performance. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a reaction mechanism diagram of the sorbate in-situ reinforced PP / EPDM thermoplastic vulcanizate.

[0030] Figure 2 is a scanning electron microscope (SEM) picture of example 4 after etching with boiling cyclohexane.

[0031] Figure 3 is a scanning electron microscope (SEM) picture of the impact fracture section of example 3.

[0032] Figure 4 is a scanning electron microscope (SEM) picture of the impact fracture section of example 4.

[0033] Figure 5 is a structure schematic diagram of the sorbate reinforced thermoplastic vulcanizate-aluminum alloy heterogeneous joint and the interface thereof in example 5. DETAILED DESCRIPTION

[0034] In order to better understand the present application, the present application will be further described below in combination with the drawings and examples, and it should be noted that the examples do not constitute a limitation on the scope of protection of the present application.

[0035] The application introduces sorbic acid and metal oxide into the process of dynamic vulcanization of PP / EPDM thermoplastic vulcanizate, and generates sorbate in situ. Under the initiation of crosslinking agent, a series of reactions occur between sorbate and PP, EPDM molecular chains, which enhances the crosslinked EPDM particles, improves the interface interaction, and increases the compatibility of PP and EPDM. While giving PP / EPDM thermoplastic vulcanizate excellent mechanical properties, the melt strength, surface polarity and interface compatibility of the elastomer are improved. The PP / EPDM thermoplastic vulcanizate enhanced by sorbate can be directly welded with aluminum alloy through friction stir spot welding to obtain a thermoplastic-metal heterogeneous structure. The obtained TPV can be widely used in the fields of automobiles, building materials and household appliances, especially in the application of replacing aluminum alloy in automobile lightweight manufacturing.

[0036] Example 1

[0037] Firstly, 70 parts by mass of ethylene propylene diene rubber (EPDM4045, Jilin Petrochemical Co., Ltd. of China Petroleum and Chemical Corporation) is plasticized on an open mill for 7 times; secondly, 0.98 parts by mass of potassium oxide powder is added to the ethylene propylene diene rubber, and cutting, rolling and triangle bagging are carried out for three times respectively until the mixing is uniform; then 3.89 parts by mass of sorbic acid powder is added, and the same cutting, rolling and triangle bagging are carried out for three times until the mixing is uniform; finally, the roll gap is adjusted to 0.4 cm to obtain 34.87 parts by mass of EPDM rubber.

[0038] 30 parts by mass of PP resin is mixed with 0.165 parts by mass of antioxidant 1010, and then added to a mixer at a temperature of 180°C and a rotation speed of 90 rpm. After melting, 34.87 parts by mass of EPDM rubber is added. After the two are fully blended, 0.9 parts by mass of DCP is added for dynamic vulcanization, and the mixing is carried out for 6.5 minutes to obtain PP / EPDM thermoplastic vulcanizate reinforced by potassium sorbate. The injection temperature of the single screw injection molding machine is: 180°C for the feeding section, 190°C for the compression section, 190°C for the homogenization section, 200°C for the head die portion, and the screw rotation speed is 90 r / min.

[0039] The sorbate reinforced thermoplastic vulcanizate is welded with aluminum alloy 6061 plate by friction stir spot welding. Before welding, one end of the aluminum alloy 6061 is placed above the TPV and fixed on the operating table with a clamp. During welding, a stirring head with a diameter of 8 mm is selected, and the rotation speed is adjusted to 1600 rpm, starting from a height of about 20 mm above the aluminum alloy. After the stirring head contacts the surface of the aluminum alloy plate, it is further pressed down by 1.5 mm, and then the current pressing amount is kept unchanged for spot welding, the process lasts for 15 s, and after spot welding, the stirring head is lifted back to the initial position and stopped rotating. Each sample is welded twice at the diagonal position of the welding area, and the sorbate potassium reinforced thermoplastic vulcanizate-aluminum alloy heterogeneous joint is obtained after welding.

[0040] Example 2

[0041] Firstly, 30 parts by mass of ethylene propylene diene rubber (EPDM4045, Jilin Petrochemical Co., Ltd. of China Petroleum and Chemical Corporation) was plasticized on an open mill for 10 times; secondly, 0.42 parts by mass of magnesium oxide powder was added into the ethylene propylene diene rubber, and cutting, rolling and triangle bagging were carried out for three times respectively until the mixing was uniform; then 2.34 parts by mass of sorbic acid powder was added, and cutting, rolling and triangle bagging were carried out for three times respectively until the mixing was uniform; finally, the roll gap was adjusted to 0.4 cm to get the sheet, and 33.18 parts by mass of EPDM rubber compound was obtained.

[0042] 70 parts by mass of PP resin and 0.105 parts by mass of antioxidant 1010 were mixed and then added into a mixer at a temperature of 180°C and a rotation speed of 90 rpm, and after melting, 32.76 parts by mass of EPDM rubber compound was added. After the two were fully blended, 0.53 parts by mass of DCP was added for dynamic vulcanization, and the mixing was carried out for 6.5 minutes to discharge, and 3 parts by mass of sorbate magnesium reinforced PP / EPDM thermoplastic vulcanized rubber was obtained. The injection temperature of the single screw injection molding machine was: 180°C for the feeding section, 190°C for the compression section, 190°C for the homogenization section, 200°C for the head die section, and the screw rotation speed was 90 r / min.

[0043] The sorbate reinforced thermoplastic vulcanized rubber was welded with aluminum alloy 6061 plate by friction stir spot welding. Before welding, one end of the aluminum alloy 6061 was placed above the TPV and fixed on the operating table with a clamp. When welding, a stirring head with a diameter of 8 mm was selected, and the rotation speed was adjusted to 1600 rpm, and the stirring head was pressed from a height of about 20 mm above the aluminum alloy. After the stirring head contacted the surface of the aluminum alloy plate, it was pressed down by 1.5 mm, and then the current pressing amount was kept unchanged for spot welding, and the process lasted for 15 s. After spot welding, the stirring head was lifted back to the initial position and stopped rotating. Each sample was welded twice at the diagonal position of the welding area, and the sorbate magnesium reinforced thermoplastic vulcanized rubber-aluminum alloy heterogeneous joint was obtained after welding.

[0044] Example 3

[0045] Firstly, 30 parts by mass of ethylene propylene diene rubber (EPDM4045, Jilin Petrochemical Co., Ltd. of China Petroleum and Chemical Corporation) was plasticized on an open mill for 10 times; secondly, 0.42 parts by mass of magnesium oxide powder was added into the ethylene propylene diene rubber, and cutting, rolling and triangle bagging were carried out for three times respectively until the mixing was uniform; then 2.34 parts by mass of sorbic acid powder was added, and cutting, rolling and triangle bagging were carried out for three times respectively until the mixing was uniform; finally, the roll gap was adjusted to 0.4 cm to get the sheet, and 33.18 parts by mass of EPDM rubber compound was obtained.

[0046] Take 70 parts by mass of PP resin and 0.105 parts by mass of antioxidant 1010 after mixing into the temperature of 180 ℃, the speed of 90 rpm of the internal mixer, melt, add 36.36 parts by mass of EPDM rubber to it. After the two are fully blended, 0.65 parts by mass of DCP is put into it to carry on the dynamic vulcanization, mixes 6.5 minutes and discharges, the PP / EPDM thermoplastic vulcanization rubber of zinc sorbate reinforced is obtained. The injection temperature of the single screw injection molding machine is: the feeding section is 180 ℃, the compression section is 190 ℃, the homogenization section is 190 ℃, the head die part is 200 ℃, and the screw rotation speed is 90 r / min.

[0047] The sorbate reinforced thermoplastic vulcanization rubber is welded with aluminum alloy 6061 plate by friction stir spot welding. Before welding, one end of the aluminum alloy 6061 is placed above the TPV and fixed on the operating table with a clamp. When welding, a stirring head with a diameter of 8 mm is selected, the rotation speed is adjusted to 1600 rpm, and the stirring head is pressed from a height of about 20 mm above the aluminum alloy. After the stirring head contacts the surface of the aluminum alloy plate, it is pressed down by 1.5 mm, then the current pressing amount is kept unchanged for spot welding, the process lasts for 15 s, and after spot welding, the stirring head is lifted back to the initial position and stopped rotating. Each sample is welded twice at the diagonal position of the welding area, and the zinc sorbate reinforced thermoplastic vulcanization rubber-aluminum alloy heterogeneous joint is obtained after welding.

[0048] Example 4

[0049] First, 30 parts by mass of ethylene propylene rubber (EPDM4045, Jilin Petrochemical Co., Ltd.) is plasticized on the open mill for 14 times; secondly, 2.52 parts by mass of sodium oxide powder is added to the ethylene propylene rubber, and cutting, rolling and triangular bagging are carried out respectively for three times until the mixing is uniform; then 7.02 parts by mass of sorbic acid powder is added, and the same cutting, rolling and triangular bagging are carried out for three times until the mixing is uniform; finally, the roll gap is adjusted to 0.4 cm to obtain 39.54 parts by mass of EPDM rubber.

[0050] Take 70 parts by mass of PP resin and 0.105 parts by mass of antioxidant 1010 after mixing into the temperature of 180 ℃, the speed of 90 rpm of the internal mixer, melt, add 36.36 parts by mass of EPDM rubber to it. After the two are fully blended, 0.65 parts by mass of DCP is put into it to carry on the dynamic vulcanization, mixes 6.5 minutes and discharges, the PP / EPDM thermoplastic vulcanization rubber of zinc sorbate reinforced is obtained. Then the sample is crushed into fine and uniform particles by a crusher, and then a standard sample is injection molded by a single screw injection molding machine. The injection temperature of the single screw injection molding machine is: the feeding section is 180 ℃, the compression section is 190 ℃, the homogenization section is 190 ℃, the head die part is 200 ℃, and the screw rotation speed is 90 r / min.

[0051] The sorbate reinforced thermoplastic vulcanizate was welded with aluminum alloy 6061 plate by friction stir spot welding. Before welding, one end of the aluminum alloy 6061 was placed above the TPV and fixed on the operating table with a clamp. When welding, a stir head with a diameter of 8 mm was selected, the rotation speed was adjusted to 1600 rpm, and the stir head was pressed from a height of about 20 mm above the aluminum alloy. After the stir head contacted the surface of the aluminum alloy plate, it was pressed for another 1.5 mm, then the current pressing amount was kept unchanged for spot welding, the process lasted for 15 s, and after spot welding, the stir head was lifted back to the initial position and stopped rotating. Each sample was welded twice at the diagonal position of the welding area, and the sodium sorbate reinforced thermoplastic vulcanizate-aluminum alloy heterogeneous joint was obtained after welding.

[0052] Example 5

[0053] First, 20 parts by mass of ethylene propylene diene rubber (EPDM4045, Jilin Petrochemical Co., Ltd. of China Petroleum and Chemical Corporation) was plasticized on an open mill for 9 times; secondly, 2.52 parts by mass of sodium oxide powder was added to the ethylene propylene diene rubber, and cutting, rolling and triangular bagging were carried out for three times respectively until the mixing was uniform; then 7.02 parts by mass of sorbic acid powder was added, and the same cutting, rolling and triangular bagging were carried out for three times until the mixing was uniform; finally, the roll gap was adjusted to 0.4 cm to obtain 39.54 parts by mass of EPDM rubber.

[0054] 70 parts by mass of PP resin and 0.105 parts by mass of antioxidant 1010 were mixed and then added to a mixer with a temperature of 180°C and a rotation speed of 90 rpm. After melting, 39.54 parts by mass of EPDM rubber was added. After the two were fully blended, 0.55 parts by mass of DCP was added for dynamic vulcanization, and the mixing time was 6.5 minutes. The zinc sorbate reinforced PP / EPDM thermoplastic vulcanizate was obtained. Then the sample was crushed into fine and uniform particles using a crusher, and then a single screw injection molding machine was used to injection mold into a standard sample. The injection molding temperature of the single screw injection molding machine was: feeding section 180°C, compression section 190°C, homogenization section 190°C, nozzle die section 200°C, and screw rotation speed 90 r / min.

[0055] The sorbate reinforced thermoplastic vulcanizate was welded with aluminum alloy 6061 plate by friction stir spot welding. Before welding, one end of the aluminum alloy 6061 was placed above the TPV and fixed on the operating table with a clamp. When welding, a 10 mm diameter stir head was selected, the rotation speed was adjusted to 1800 rpm, and the welding was started by pressing from a height of about 25 mm above the aluminum alloy. After the stir head contacted the surface of the aluminum alloy plate, it was pressed down by 2 mm, then the current pressing amount was kept unchanged for spot welding, the process lasted for 30 s, and after the spot welding was completed, the stir head was lifted back to the initial position and stopped rotating. Each sample was welded twice at the diagonal position of the welding area, and the zinc sorbate reinforced thermoplastic vulcanizate-aluminum alloy heterogeneous joint was obtained after welding.

[0056] Comparative Example 1

[0057] First, 70 parts by mass of ethylene propylene diene rubber (EPDM4045, Jilin Petrochemical Co., Ltd. of China Petroleum and Chemical Corporation) was plasticized on an open mill for 7 times; secondly, 30 parts by mass of PP resin was mixed with 0.105 parts by mass of antioxidant 1010, and then added to a mixer with a temperature of 180°C and a rotation speed of 90 rpm. After melting, 30 parts by mass of EPDM was added. After the two were fully blended, 0.45 parts by mass of DCP was added for dynamic vulcanization, and the mixture was mixed for 6.5 minutes and discharged. The PP / EPDM thermoplastic vulcanizate was obtained. The injection temperature of the single screw injection molding machine was: 180°C for the feeding section, 190°C for the compression section, 190°C for the homogenization section, 200°C for the head die portion, and the screw rotation speed was 90 r / min.

[0058] The PP / EPDM thermoplastic vulcanizate was welded with aluminum alloy 6061 plate by friction stir spot welding. Before welding, one end of the aluminum alloy 6061 was placed above the TPV and fixed on the operating table with a clamp. When welding, a 10 mm diameter stir head was selected, the rotation speed was adjusted to 1800 rpm, and the welding was started by pressing from a height of about 25 mm above the aluminum alloy. After the stir head contacted the surface of the aluminum alloy plate, it was pressed down by 2 mm, then the current pressing amount was kept unchanged for spot welding, the process lasted for 30 s, and after the spot welding was completed, the stir head was lifted back to the initial position and stopped rotating. Each sample was welded twice at the diagonal position of the welding area, and the PP / EPDM thermoplastic vulcanizate-aluminum alloy heterogeneous joint was obtained after welding.

[0059] Comparative Example 2 (TPV formula from Chinese invention patent CN103497429B)

[0060] A low odor TPV coated with ABS substrate by secondary molding and its preparation method and application are composed of the following components in parts by weight: HDPE 10 parts, PP 10 parts, EPDM 19.4 parts, naphthenic oil rubber plasticizer 19.4 parts, thermoplastic polyester elastomer 30 parts, odor removal agent 3 parts, bis-dipentyl crosslinking initiator 0.5 parts, trihydroxy acrylate co-crosslinking agent 1 part, 3000 mesh kaolin 6.5 parts, antioxidant 101 0.2 parts.

[0061] The process method is: first, put polyolefin, rubber component, rubber plasticizer, polyester thermoplastic elastomer, filler, antioxidant and processing aid into the internal mixer, mix at 150-180℃ for 10-30min, then extrude and granulate to prepare a one-step TPV raw material; then uniformly premix the prepared one-step material with peroxide crosslinking initiator, co-crosslinking agent and odor removal agent; finally, put it into a twin-screw extrusion equipment and extrude at 190-230℃ to obtain a low odor TPV coated with ABS substrate by secondary molding.

[0062] The TPV is welded together with aluminum alloy 6061 plate by friction stir spot welding. When welding, a stirrer with a diameter of 8mm is selected, the rotation speed is adjusted to 1600rpm, and the stirrer is pressed from a height of about 20mm above the aluminum alloy; after the stirrer contacts the surface of the aluminum alloy plate, it is pressed down by 1.5mm, then the current pressing amount is kept unchanged for spot welding, the process lasts for 15s, and after spot welding, the stirrer is lifted back to the initial position and stopped rotating. Each sample is welded twice at the diagonal position of the welding area, and the TPV-aluminum alloy heterogeneous joint is obtained after welding.

[0063] Comparative Example 3 (TPV formula from Chinese invention patent CN114410017A)

[0064] A preparation method of a TPV material, comprising the following steps:

[0065] (1) According to the weight fraction, 15.2 parts of EPDM (Dow EPDM NORDEL-3722P), 5.7 parts of PP (Z30S), 14.21 parts of filling oil (brand 150N), 1.9 parts of SEBS (YH-501T), 0.76 parts of vulcanizing agent (DCP), and 0.23 parts of vulcanizing aid (TAIC) are weighed; under the condition of 55℃, the filling oil is added to the EPDM while stirring, then the PP, SEBS, vulcanizing agent and vulcanizing aid (TAIC) are added, and after uniform mixing, it is placed in a parallel co-rotating twin-screw extruder (screw length-diameter ratio L / D is 56), melt extruded at a screw speed of 180rpm, and the screw segments and head temperature is 80, 180, 190, 200, 200, 190, 190, 190, 180, 180, 170, 170, 180℃, then granulated after extrusion to obtain a primary TPV material.

[0066] (2) 16.8 parts of polar resin (WHT-1185), 8 parts of SEBS (YH-501T), 11.9 parts of compatibilizer (Kotem G-1901), 25 parts of tackifying resin (terpene resin), and 0.3 parts of anti-aging agent (containing 0.15 parts of antioxidant BASF168 and 0.15 parts of antioxidant 1010) were weighed by weight fraction; the weighed polar resin, SEBS, compatibilizer, tackifying resin, and anti-aging agent were added to the primary TPV material prepared in step (1), and after being mixed thoroughly, were placed in a parallel co-rotating twin-screw extruder (screw length-diameter ratio L / D was 56), and were melt-extruded at a screw rotation speed of 150 rpm and a screw segment and die head temperature of 80, 180, 190, 200, 200, 190, 190, 190, 180, 180, 180, 180, 180 °C; after extrusion, granulation was performed to obtain a TPV material.

[0067] The TPV was welded together with the aluminum alloy 6061 plate by friction stir spot welding. Before welding, one end of the aluminum alloy 6061 was placed above the TPV and fixed on the operating table by a clamp. During welding, a stirrer with a diameter of 8 mm was selected, and the rotation speed was adjusted to 1600 rpm, and the stirrer was pressed from a height of about 20 mm above the aluminum alloy. After the stirrer contacted the surface of the aluminum alloy plate, it was pressed by 1.5 mm, and then spot welding was performed with the current pressing amount unchanged, the process lasted for 15 s, and after spot welding, the stirrer was lifted to the initial position and stopped rotating. Each sample was welded twice at the diagonal position of the welding area, and the TPV-aluminum alloy heterogeneous joint was obtained after welding.

[0068] Product effect test

[0069] The tensile strength (MPa) and melt index (g / 10 min) of the TPV materials prepared in test examples 1-5 and comparative examples 1-3 were tested. The test standard for tensile strength refers to GB / T1040.4-2006; the test standard for melt index refers to GB / T3682.1-2018.

[0070] The polarity force (mN / m) of test examples 1-5 and comparative example 1 was tested. The polarity force was calculated according to the contact angle by the two-liquid method, and the test standard for the contact angle refers to GB / T 30693-2014.

[0071] The shear strength test was carried out by placing the welded sample at room temperature for 24 h, then clamping the sample with a test clamp, and using a universal testing machine to test the peel strength, and the shear strength with the 6061-T6 aluminum alloy was obtained.

[0072] The properties of examples 1-5 and comparative examples 1-4 are shown in Table 1

[0073] Table 1

[0074]

[0075]

[0076] In the embodiments of the present application, the effect of Example 1 is relatively poor, the effect of Example 5 is the best, and the effect is better and better from Example 1 to Example 5, but even Example 1 has a significant improvement compared with the comparative examples.

[0077] In Example 2 and Example 3, the rubber-plastic ratio is the same, and the same mass of sorbate is theoretically generated. The tensile strength, polar force and joint shear strength are increased from 21.57 MPa, 0.27 mN / m and 3.61 MPa of Example 2 to 21.66 MPa, 0.35 mN / m and 5.42 MPa of Example 3, respectively, and the melt index is reduced from 1.43 g / 10 min to 1.28 g / 10 min. It may be that the reinforcing effect of zinc sorbate on PP / EPDM thermoplastic vulcanized rubber is slightly better than that of magnesium sorbate. In Example 3 and Example 4, the rubber-plastic ratio is the same, and the amount of sorbate in Example 3 and Example 4 is different. The tensile strength of the PP / EPDM thermoplastic vulcanized rubber is increased from 21.66 MPa to 22.87 MPa, the melt index is reduced from 1.28 g / 10 min to 1.05 g / 10 min, the polar force is increased from 0.35 mN / m to 0.71 mN / m, and the joint shear strength is increased from 5.42 MPa to 7.68 MPa, all of which are improved. It may be that the increase of in-situ generated sorbate has no negative effect on the mechanical properties and melt strength of PP / EPDM TPV, and even can improve the crosslinking degree of EPDM phase, so that it not only entangles more seriously with PP molecular chain, but also has better compatibility, lower flowability and higher melt strength. At the same time, the sorbate and the polar groups it carries are grafted onto the PP / EPDM thermoplastic vulcanized rubber, which improves the surface energy of the TPV, and effectively improves the welding strength of the PP / EPDM TPV and aluminum alloy.

[0078] From Table 1, it can be seen that, for Comparative Example 1, the tensile strength of the PP / EPDM thermoplastic vulcanizate is increased from 11.83 MPa to 12.83 MPa, the melt index is decreased from 2.47 g / 10 min to 2.25 g / 10 min, and the polar force is increased from 0.003 mN / m to 0.27 mN / m, while the ratio of rubber to plastic is the same as 70 / 30. After welding, the joint strength of Comparative Example 1 is only 0.12 MPa, while Example 1 can be welded with 6061 aluminum alloy after sorbitate enhancement, and the joint shear strength reaches 2.76 MPa. The introduction of sorbitate significantly improves the mechanical properties of the PP / EPDM thermoplastic vulcanizate, and also improves the melt strength and surface polarity, so that the PP / EPDM thermoplastic vulcanizate can be welded with polar materials, and the deformation during processing is reduced, and the strength of the heterogeneous joint is improved.

[0079] In Comparative Example 1, the polar additives in the system are different, and the tensile strength and melt index of Comparative Example 2 and Comparative Example 3 are obviously not as good as Example 1. Although they have a certain polarity, the deformation during welding is large, the welding effect is poor, and the joint shear strength is lower than 2.76 MPa of Example 1. The introduction of polar sorbitate improves the interfacial compatibility of the PP / EPDM thermoplastic vulcanizate, and the polar groups on the surface also increase the surface energy of the elastomer, thereby improving the welding strength of the PP / EPDM TPV and aluminum alloy.

[0080] Figure 1 The in-situ generation process of sorbitate and the enhancement mechanism of PP / EPDM TPV. During the melt blending process of EPDM rubber and PP, the sorbitate is generated in-situ from sorbic acid and metal oxide under the influence of high temperature. Under the initiation of organic peroxide radicals, the sorbitate polymerizes to form poly-salt particles. Some of the poly-salt particles can aggregate to form larger structures and phase separate from the rubber matrix, forming rigid particles of nanometer size dispersed in the rubber matrix, which have an enhancement effect. At the same time, another part of the poly-salt particles are grafted onto the rubber macromolecular chains, forming a highly ionic crosslinked network with the rubber main chain, which makes the composite material have strong interfacial bonding force. The agglomerates of poly-salt particles intertwine with each other in the interface region, which improves the interaction between the two phases. Under the action of high temperature and external force, the stress transfer efficiency is higher, and the molecular chains are not easy to be disentangled, thereby showing good mechanical properties and melt strength. At the same time, the polar groups on the sorbitate increase the surface energy of the PP / EPDM thermoplastic vulcanizate, and endow the material with the characteristics of being able to be welded with metals and metal alloys.

[0081] Figure 2is the scanning electron microscope picture of Example 3 after etching by boiling cyclohexane, which can dissolve the uncrosslinked EPDM phase, so that the crosslinking degree of EPDM phase can be evaluated to some extent. It can be seen that a lot of holes appear in the PP / EPDM thermoplastic vulcanizate after etching by cyclohexane, which represents the EPDM particles that do not undergo crosslinking reaction. In fact, when the content of EPDM is much less than that of PP, during the blending process, EPDM is mainly dispersed in the continuous PP phase in the form of "droplets", at this time, most of the free radicals generated by the decomposition of DCP are consumed in the PP continuous phase, and the amount of free radicals used to initiate the crosslinking of EPDM is less, so the crosslinking degree of EPDM is not high. However, the in-situ generated free radicals are quickly and effectively captured, and quickly react, thereby promoting the crosslinking reaction process of the EPDM phase.

[0082] Figure 3 and Figure 4 are the scanning electron microscope (SEM) pictures of the low-temperature brittle fracture surfaces of Example 4 and Example 3, respectively. As shown in the figure, the low-temperature brittle fracture surface of Example 3 is gathered with a large number of nanoscale rubber particles and polysorbate agglomerates, which form uneven protrusions on the surface of the PP matrix, and only part of the particles are embedded in the PP matrix. With the increase of the content of polysorbate, there are almost no protrusions on the brittle fracture surface of Example 4, and the fracture surface is very smooth, and a large number of uniform nanoscale rubber particles are completely embedded in the PP continuous phase. Under the action of the polysorbate graft product, the surface of the particles is coated with a thin layer of PP phase, so that the interfacial interaction between the two phases is improved, thereby showing good compatibility.

[0083] Figure 5 is the schematic diagram of the structure of the sorbate reinforced thermoplastic vulcanizate-aluminum alloy heterogeneous joint and the interface thereof in Example 5. As can be seen from the figure, during the welding process of the friction stir lap joint, the pressing of the welded joint makes the surface of the aluminum alloy slightly convex at the welding site, and the molten PP / EPDM thermoplastic vulcanizate at the interface is subjected to the extrusion of the aluminum alloy and will be depressed, forming a mechanical interlocking structure, thereby greatly improving the tensile shear strength of the heterogeneous joint.

[0084] Overall, the sorbate enhances the thermoplastic vulcanized rubber-aluminum alloy heterogeneous joint, the shear strength of the joint is high, and the mechanical properties of the TPV part are more excellent. Among them, the tensile strength, melt strength and surface polarity of the TPV in the thermoplastic vulcanized rubber-aluminum alloy heterogeneous structure prepared in the embodiment of the application are excellent, the shear strength of the joint after welding is greatly improved, which is much higher than that of the comparative example, and such performance can fully meet the mechanical property requirements of part of the automobile structure. The preparation of the heterogeneous structure has low requirements for the shape and size of the TPV, and the two can be welded as long as there is a part of the interface that can be fitted. Therefore, part of the aluminum alloy components can be replaced by TPV materials that meet the mechanical property requirements, and the heterogeneous structure is formed by friction stir spot welding and aluminum alloy welding to realize the lightweight manufacturing of the automobile.

Claims

1. A sorbate-reinforced thermoplastic vulcanizate-aluminum alloy heterojunction, characterized in that: The sorbate-reinforced thermoplastic vulcanizate is obtained by welding it to an aluminum alloy via friction stir spot welding. The sorbate-reinforced thermoplastic vulcanizate is prepared by the following method: the raw material formula is as follows (by weight): 20 parts EPDM rubber, 7.02 parts sorbic acid, 2.52 parts sodium oxide, 70 parts polypropylene resin, 0.105 parts antioxidant, and 0.55 parts dicumyl peroxide. The preparation method includes the following steps: 1) Rubber mixing: Under room temperature conditions, EPDM rubber is plasticized 9 times on a two-roll mill; sodium oxide powder is added, and the rubber is cut, rolled, and formed into triangles 3 times each, and mixed evenly; then sorbic acid powder is added, and the rubber is cut, rolled, and formed into triangles 3 times each, and mixed evenly; finally, the rubber is sheeted to obtain the compound. 2) Dynamic vulcanization: First, mix polypropylene resin and antioxidant 1010 and add them to a mixer. Control the temperature of the mixer to 180℃ and the speed to 90rpm. After melting, add the compound first. After mixing evenly, add dicumyl peroxide. Dynamically vulcanize for 6.5min in a closed state to obtain sorbate-reinforced thermoplastic vulcanizate. 3) Friction stir spot welding: Place one end of the aluminum alloy on top of the thermoplastic vulcanizate and fix it with a clamp; select a 10mm diameter stirring head, adjust the speed to 1800rpm, and start pressing down from a height of 25mm above the aluminum alloy; after the stirring head contacts the surface of the aluminum alloy plate, continue to press down 2mm, keep the current pressing amount unchanged and perform spot welding, the process lasts for 30s, after the spot welding is completed, raise the stirring head to return to the initial position.

2. The sorbate-reinforced thermoplastic vulcanizate-aluminum alloy heterojunction according to claim 1, characterized in that: The EPDM rubber is ethylene-propylene or dicyclopentadiene.

3. The sorbate-reinforced thermoplastic vulcanizate-aluminum alloy heterojunction according to claim 1, characterized in that: The polypropylene resin is at least one of random copolymer, syndiotactic copolymer, and homopolymer polypropylene.

4. The application of the sorbate-reinforced thermoplastic vulcanizate-aluminum alloy heterojunction as described in any one of claims 1-3 in replacing aluminum alloys in automotive lightweight manufacturing.

Images