High-toughness SMC (Sheet Molding Compound) resin and preparation method thereof

Abstract

The invention relates to the technical field of SMC resin, in particular to high-toughness SMC resin and a preparation method thereof. The high-toughness SMC resin is prepared from the following raw materials in parts by weight: 80 to 120 parts of unsaturated resin, 2 to 5 parts of an initiator, 15 to 25 parts of a low shrinkage agent, 0.3 to 1 part of a polymerization inhibitor, 25 to 35 parts of a compound cross-linking agent, 0.5 to 1.5 parts of a silane coupling agent, 25 to 40 parts of chopped glass fiber, 2 to 5 parts of a release agent and 2 to 6 parts of a thickening agent, the compound cross-linking agent is a mixture of a high-molecular cross-linking agent and a small-molecular cross-linking agent, and the high-molecular cross-linking agent is double-end vinyl silicone oil; the method has the advantage that the toughness of the SMC resin can be effectively improved.

Description

Technical Field

[0001] The present application relates to the technical field of SMC resin, and in particular to a high-toughness SMC resin and a preparation method thereof. Background Art

[0002] As a high-performance thermoset composite material, SMC (Sheet Molding Compound) resin holds a key position in industrial applications due to its excellent mechanical properties, corrosion resistance, and ease of molding. In recent years, with increasing environmental protection requirements and the growing demand for lightweighting, the research and application of SMC resin has garnered widespread attention. Due to the high density of SMC materials, the current industry-wide improvement solution is to add low-density fillers. However, the large addition of low-density fillers can affect the material's mechanical properties, particularly its toughness, making it unsuitable for practical applications. Summary of the Invention

[0003] In order to effectively improve the toughness of SMC resin, the present application provides a high-toughness SMC resin and a preparation method thereof.

[0004] In the first aspect, the present application provides a high-toughness SMC resin, which adopts the following technical solution: A high-toughness SMC resin comprises the following raw materials in parts by weight: 80-120 parts of an unsaturated resin, 2-5 parts of an initiator, 15-25 parts of a low-shrinkage agent, 0.3-1 part of a polymerization inhibitor, 25-35 parts of a compound cross-linking agent, 0.5-1.5 parts of a silane coupling agent, 25-40 parts of chopped glass fibers, 2-5 parts of a release agent, and 2-6 parts of a thickener; the compound cross-linking agent is a mixture of a high molecular weight cross-linking agent and a low molecular weight cross-linking agent, and the high molecular weight cross-linking agent is a double-terminated vinyl silicone oil.

[0005] By adopting the above technical solution, the present application mainly compounds the cross-linking agent by mixing a high molecular weight cross-linking agent and a low molecular weight cross-linking agent. The high molecular weight cross-linking agent has a low cross-linking density and the low molecular weight cross-linking density has a high cross-linking density, so that a wavy cross-linking density can be formed inside the SMC resin. The high and low cross-linking density gives the SMC resin a certain elasticity; and the high molecular weight cross-linking agent adopts a double-ended vinyl silicone oil, which has a certain flexibility and can also improve the toughness of the SMC resin; under the action of these two aspects, it can buffer the external force and greatly improve the toughness of the SMC resin; and this scheme, compared with adding an elastic resin or adding an inorganic filler, does not have the problems of phase separation, poor system compatibility, etc. Therefore, the obtained SMC resin has the advantages of high toughness and high strength.

[0006] Preferably, the mass ratio of the polymer cross-linking agent to the small molecule cross-linking agent is 1:(4-6).

[0007] By adopting the above technical solution and limiting their mass ratio, the small molecule cross-linking agent can be in a state of being in a larger amount, so that the overall cross-linking density of the SMC resin can be controlled. In addition, the large amount of small molecule cross-linking agents can also dominate the rapid reaction stage, form dense local cross-linking points, and improve the strength of the initial curing stage; while the polymer cross-linking agent can avoid the brittle fracture caused by pure small molecule cross-linking; through the mutual synergy of the polymer cross-linking agent and the small molecule cross-linking agent, the SMC resin has both rigidity and toughness, and has greater application potential.

[0008] Preferably, the viscosity of the double-ended vinyl silicone oil at 25° C. ranges from 1000 to 3000 cst.

[0009] By adopting the above technical solution and using double-ended vinyl silicone oil in this viscosity range, it is possible to avoid the situation where the molecular weight is too low and the effect is not obvious, and the molecular weight is too high and the dispersion is uneven in the resin system; and the double-ended vinyl silicone oil in this viscosity range can be compounded with small molecule cross-linking agents with better effect, achieving mixed cross-linking and optimizing the network structure within the system.

[0010] Preferably, the small molecule cross-linking agent is one or more of styrene, methylphenylene glycol, tert-butylphenylene glycol, chlorostyrene, methylphenylene glycol, vinylbenzene and methyl methacrylate.

[0011] By adopting the above technical solutions, the technical solutions of the present application are extremely inclusive and can achieve good compounding effects for general small molecule cross-linking agents. In theory, all of them can be realized. Although they are not explored one by one in the examples of the present application, they are all within the scope of protection of the present application.

[0012] Preferably, the SMC resin further comprises 1-2.5 parts by weight of nanoclay.

[0013] By adopting the above technical solution, nanoclay can be dispersed in the resin through intercalation or exfoliation structure, hindering crack propagation and improving tensile strength and toughness. The silane coupling agent added to the system can also modify the surface of nanoclay, enhance the interfacial bonding with the resin, and make the SMC resin more integrated.

[0014] Preferably, the silane coupling agent is a vinyl silane coupling agent.

[0015] By adopting the above technical solution, in addition to reducing the interfacial tension between the inorganic filler and the system, the double bond groups contained in the vinyl silane coupling agent can also participate in the cross-linking of the system, thereby increasing the cross-linking density of the system and the strength of the SMC resin. In addition, the inorganic filler can be cross-linked at its interface, further strengthening its bonding with the system, thereby further alleviating the interfacial stress concentration between the inorganic filler and the resin system and improving the impact toughness.

[0016] Preferably, the vinyl silane coupling agent is one or more of vinyl triethoxysilane, γ-methacryloxypropyl trimethoxysilane, vinyl tributylon oxime silane, 7-octenyl trimethoxysilane, vinyl triisopropoxysilane and acryloxymethyl trimethoxysilane.

[0017] By adopting the above technical solutions, the technical solutions of the present application are extremely inclusive and can achieve good compounding effects on general vinyl silane coupling agents. In theory, all of them can be realized. Although they are not explored one by one in the examples of the present application, they are all within the scope of protection of the present application.

[0018] Preferably, the unsaturated resin is one or more of o-phthalic unsaturated polyester resin, isophthalic unsaturated polyester resin, bisphenol A unsaturated polyester resin, epoxy vinyl ester resin and brominated flame retardant unsaturated polyester resin.

[0019] By adopting the above technical solution, the technical solution of the present application is applicable to the preparation of SMC resins based on various unsaturated resins, and has very wide applicability.

[0020] In a second aspect, the present application provides a method for preparing a high-toughness SMC resin, using the following technical solution: A method for preparing a high-toughness SMC resin comprises the following steps: S1. Add all raw materials into a blender and stir them until they are evenly mixed to obtain a resin paste. Then, the resin paste and chopped glass fibers are impregnated on an SMC unit, and a sheet is obtained by compacting and kneading. S2. Curing the sheet, maintaining the curing temperature between 25-40°C and the curing time between 24-50 hours, and then compression molding the cured sheet at a molding temperature of 140-150°C, a molding pressure of 4-7 MPa, and a molding time of 4-15 minutes to obtain a high-toughness SMC resin.

[0021] By adopting the above technical solution, high-pressure rolling is used to ensure that the resin paste is evenly impregnated into the fiber, and the fiber content is controlled (30-40%), which can avoid bubbles and dry yarn; the pressing and kneading process can eliminate bubbles and form a uniform sheet, providing a stable structural basis for subsequent curing; aging can trigger the pre-polymerization and thickening of the resin to form a thixotropic structure, which is convenient for balancing fluidity and conformality during molding; then, by limiting the molding parameters and matching the decomposition temperature of the initiator, sufficient curing can be ensured, pressure control can expel bubbles and compact the fiber, improve density and dimensional accuracy, and sufficient molding time can avoid brittleness caused by over-curing and retain toughness.

[0022] In summary, this application includes at least one of the following beneficial technical effects: 1. The present application mainly compounds the cross-linking agent by mixing a polymer cross-linking agent and a small molecule cross-linking agent. The polymer cross-linking agent has a low cross-linking density and the small molecule cross-linking density has a high cross-linking density, so that a wavy cross-linking density can be formed inside the SMC resin. The high and low cross-linking density gives the SMC resin a certain elasticity; in addition, the polymer cross-linking agent uses a double-ended vinyl silicone oil, which has a certain flexibility and can also improve the toughness of the SMC resin; under the action of these two aspects, it can buffer the external force and greatly improve the toughness of the SMC resin; and this scheme, compared with adding an elastic resin or adding an inorganic filler, does not have the problems of phase separation and poor system compatibility. Therefore, the obtained SMC resin has the advantages of high toughness and high strength.

[0023] 2. The SMC resin prepared in this application has excellent tensile strength and impact toughness, and its density is also relatively low; its density is between 1.45-1.56g / m 3 The tensile strength is 146MPa and above, and the maximum can reach 167MPa. At the same time, its notched impact strength can reach 88-99kJ / m 2 . DETAILED DESCRIPTION

[0024] The following is a further detailed description of this application in conjunction with the specific content.

[0025] raw material The raw materials used in the examples of the present application are all commercially available products, among which the unsaturated polyester resin is an o-phthalic unsaturated resin purchased from Jinling Petrochemical, product model JLC-800; the polystyrene low shrinkage agent is purchased from Kingfa Technology, product model GF-PS-800, with a molecular weight range of 60,000-80,000; zinc stearate is purchased from Hebei Kuojun Chemical Technology Co., Ltd. and is a general-purpose type; double-ended vinyl silicone oil is purchased from Shenzhen Jipeng Silicon Fluorine Materials Co., Ltd.; magnesium oxide is purchased from Weifang Lihe Powder Technology Co., Ltd., model Y-KB-XMZS / 5. Example

[0026] Example 1 A high-toughness SMC resin, the raw materials and the amounts of the raw materials are shown in Table 1, and the preparation method is as follows: S1. According to the amount in Table 1, each raw material was added to a blender and stirred. After stirring evenly, a resin paste was obtained. The resin paste and chopped glass fibers were then impregnated on an SMC unit, and a sheet was obtained after compaction and kneading. The low shrinkage agent was a polystyrene low shrinkage agent. The compound cross-linking agent was a mixture of bi-terminal vinyl silicone oil and styrene in a mass ratio of 1:5. The viscosity of the bi-terminal vinyl silicone oil was 2000 cst at 25°C. The silane coupling agent was N-propyltrimethoxysilane. The average length of the chopped glass fibers was 35 mm and the diameter was 20 μm. S2. The sheet is cured at a temperature between 25°C and 40°C for 40 hours, and then the cured sheet is compression molded at a temperature of 145°C, a pressure of 5 MPa, and a time of 10 minutes to obtain a high-toughness SMC resin.

[0027] Table 1 Raw materials and amounts of raw materials used in Example 1 (kg) Unsaturated polyester resin 100 Di-tert-butyl peroxide 2.5 Low shrinkage agent 20 p-Benzoquinone 0.5 Compound crosslinking agent 30 Silane coupling agent 1 Chopped glass fiber 30 Zinc stearate 4 magnesium oxide 4 Example 2 A high-toughness SMC resin is different from Example 1 in that the viscosity of its double-ended vinyl silicone oil is 1000 cst at 25° C., and the remaining steps are the same as Example 1.

[0028] Example 3 A high-toughness SMC resin is different from Example 1 in that the viscosity of its double-ended vinyl silicone oil is 3000 cst at 25° C. The remaining steps are the same as Example 1.

[0029] Example 4 A high-toughness SMC resin is different from Example 1 in that the mass ratio of the double-terminated vinyl silicone oil to styrene is 1:4, and the remaining steps are the same as Example 1.

[0030] Example 5 A high-toughness SMC resin is different from Example 1 in that the mass ratio of the double-terminated vinyl silicone oil to styrene is 1:6, and the remaining steps are the same as Example 1.

[0031] Example 6 A high-toughness SMC resin is different from Example 1 in that its raw materials also include 1.4 kg of nanoclay, and the remaining steps are the same as Example 1.

[0032] Example 7 A high-toughness SMC resin is different from Example 6 in that its silane coupling agent is 7-octenyltrimethoxysilane, and the remaining steps are the same as Example 6.

[0033] Comparative Example Comparative Example 1 A high-toughness SMC resin is different from Example 1 in that the double-terminated vinyl silicone oil is replaced with styrene of equal mass in its compound cross-linking agent, and the remaining steps are the same as Example 1.

[0034] Performance testing Detection method / test method High-toughness SMC resins were prepared according to the preparation methods of Examples 1-7 and Comparative Example 1, and then tested according to the following test method. The test results are shown in Table 2.

[0035] Density: tested according to the test method in GB / T1463-2005; Tensile strength: tested by the test method in GB / T1447-2005 "Test method for tensile properties of fiber reinforced plastics"; Impact toughness: tested by the test method in GB / T1451-2005 "Test method for impact toughness of simply supported beam of fiber reinforced plastics".

[0036] Table 2 Test results of Examples 1-7 and Comparative Example 1 It can be seen from the test data of Examples 1-7 and Comparative Example 1, as well as Table 2, that the SMC resin prepared in this application has both excellent tensile strength and impact toughness, and its density is also relatively low; its density is in the range of 1.45-1.56 g / m 3 The tensile strength is 146MPa and above, and the maximum can reach 167MPa. At the same time, its notched impact strength can reach 88-99kJ / m 2 .

[0037] This application mainly compounded the crosslinking agent, using a mixture of a high molecular weight crosslinking agent and a low molecular weight crosslinking agent. The high molecular weight crosslinking agent has a low crosslinking density and the low molecular weight crosslinking agent has a high crosslinking density. This can form a wavy crosslinking density state within the SMC resin. The high and low crosslinking density state gives the SMC resin a certain elasticity. In addition, the high molecular weight crosslinking agent uses a double-ended vinyl silicone oil. The double-ended vinyl silicone oil has a certain flexibility and can also improve the toughness of the SMC resin. Under these two effects, it can buffer the external force and significantly improve the toughness of the SMC resin. This can be verified by the test data of Example 1 and Comparative Example 1.

[0038] It can be seen from the test data of Examples 1-3 that as the viscosity of the double-ended vinyl silicone oil gradually increases, the toughness of its SMC resin first increases and then decreases; analysis shows that this is because the viscosity of the double-ended vinyl silicone oil is too low, the wave-shaped density interlacing formed is not obvious, and the viscosity is too high, and it is unevenly dispersed in the resin system, affecting crosslinking. Therefore, the double-ended vinyl silicone oil in this viscosity range can be better compounded with a small molecule crosslinker, achieving mixed crosslinking and optimizing the network structure within the system.

[0039] It can be seen from the test data of Example 1 and Examples 4-6 that by limiting their mass ratio, the small molecule cross-linking agent can be in a more state, so that the overall cross-linking density of the SMC resin can be controlled, and more small molecule cross-linking agents can also dominate the rapid reaction stage, form dense local cross-linking points, and improve the strength of the initial curing stage; while the polymer cross-linking agent can avoid the brittle fracture caused by pure small molecule cross-linking; through the mutual synergy of the polymer cross-linking agent and the small molecule cross-linking agent, the SMC resin has both rigidity and toughness, and has greater application potential; and by exploring their mass ratio, a mass ratio of the polymer cross-linking agent to the small molecule cross-linking agent of 1:5 is the optimal ratio.

[0040] The test data of Examples 1 and 6 show that nanoclay can be dispersed in the resin through intercalation or exfoliation structure, hindering crack propagation and improving tensile strength and toughness. The silane coupling agent added to the system can also modify the surface of the nanoclay, enhancing the interfacial bonding with the resin, and making the integrity of the SMC resin stronger. In conjunction with Example 7, in addition to reducing the interfacial tension between the inorganic filler and the system, the double bond groups contained in the vinyl silane coupling agent can also participate in the crosslinking of the system, thereby increasing the crosslinking density of the system and the strength of the SMC resin. In addition, the inorganic filler can be crosslinked through its interface, further strengthening its bonding with the system, thereby further alleviating the interfacial stress concentration between the inorganic filler and the resin system and improving impact toughness.

[0041] This specific embodiment is merely an explanation of the present invention and is not intended to limit the present invention. After reading this specification, those skilled in the art may make non-creative modifications to this embodiment as needed. However, as long as such modifications are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A high-toughness SMC resin, characterized by: The invention comprises the following raw materials in parts by weight: 80-120 parts of unsaturated resin, 2-5 parts of initiator, 15-25 parts of low shrinkage agent, 0.3-1 part of polymerization inhibitor, 25-35 parts of compound cross-linking agent, 0.5-1.5 parts of silane coupling agent, 25-40 parts of chopped glass fiber, 2-5 parts of release agent and 2-6 parts of thickener; the compound cross-linking agent is a mixture of a high molecular cross-linking agent and a low molecular cross-linking agent, and the high molecular cross-linking agent is a double-ended vinyl silicone oil.

2. A high-toughness SMC resin according to claim 1, characterized in that: The mass ratio of the polymer cross-linking agent to the small molecule cross-linking agent is 1:(4-6).

3. The high-toughness SMC resin according to claim 1, characterized in that: The viscosity of the double-ended vinyl silicone oil at 25° C. ranges from 1000 to 3000 cst.

4. The high-toughness SMC resin according to claim 1, characterized in that: The small molecule cross-linking agent is one or more of styrene, methylphenylene glycol, tert-butylphenylene glycol, chlorostyrene, methylphenylene glycol, vinylbenzene and methyl methacrylate.

5. The high-toughness SMC resin according to claim 1, characterized in that: The SMC resin further comprises 1-2.5 parts by weight of nanoclay.

6. The high-toughness SMC resin according to claim 5, characterized in that: The silane coupling agent is a vinyl silane coupling agent.

7. The high-toughness SMC resin according to claim 6, characterized in that: The vinyl silane coupling agent is one or more of vinyl triethoxysilane, γ-methacryloxypropyl trimethoxysilane, vinyl tributylon oxime silane, 7-octenyl trimethoxysilane, vinyl triisopropoxysilane and acryloxymethyl trimethoxysilane.

8. The high-toughness SMC resin according to claim 1, characterized in that: The unsaturated resin is one or more of o-phthalic unsaturated polyester resin, isophthalic unsaturated polyester resin, bisphenol A unsaturated polyester resin, epoxy vinyl ester resin and brominated flame retardant unsaturated polyester resin.

9. A method for preparing the high-toughness SMC resin according to any one of claims 1 to 8, characterized in that: It includes the following steps: S1. Add all raw materials into a blender and stir them until they are evenly mixed to obtain a resin paste. Then, the resin paste and chopped glass fibers are impregnated on an SMC unit, and a sheet is obtained by compacting and kneading. S2. Curing the sheet, maintaining the curing temperature between 25-40°C and the curing time between 24-50 hours, and then compression molding the cured sheet at a molding temperature of 140-150°C, a molding pressure of 4-7 MPa, and a molding time of 4-15 minutes to obtain a high-toughness SMC resin.

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