Zero-shrinkage high-strength high-modulus SMC material and preparation method and application thereof

Abstract

The application discloses a kind of zero shrinkage high-strength high-modulus SMC materials and its preparation method and application, including the following weight parts of preparation raw materials: unsaturated polyester resin 30-50 parts, high-modulus polyester resin 25-35 parts, low shrinkage control agent 25-35 parts, curing agent 1-2 parts, release agent 4-6 parts, spherical filler 125-185 parts, thickening agent 1-3 parts, glass fiber mat 20-50 parts, short-cut glass fiber without alkali 60-100 parts.The application uses polyurethane modified PMMA as low shrinkage control agent, and simultaneously uses glass fiber mat and short-cut glass fiber to jointly construct sandwich sheet structure, through the synergistic effect between chemical modification of low shrinkage agent and enhanced structure, the prepared SMC material reaches the practical sense of zero shrinkage, shrinkage rate≤0.01%, solves the assembly gap and warping deformation problem caused by shrinkage of large parts, and simultaneously realizes the synergistic promotion of high strength and high modulus, and realizes free polishing direct spraying.

Description

Technical Field

[0001] This invention relates to the field of SMC materials and preparation methods, and in particular to a zero-shrinkage, high-strength, high-modulus SMC material, its preparation method, and its applications. Background Technology

[0002] Sheet molding compound (SMC) is an advanced fiber-reinforced thermosetting composite material semi-finished product. It is composed of unsaturated polyester resin, reinforcing materials (glass fiber), fillers, initiators, thickeners, low-shrinkage additives, and various auxiliaries, compounded into a sheet form through a complex process. SMC composites are widely used in the automotive and transportation industries due to their excellent mechanical properties, high design freedom, good dimensional stability, excellent corrosion and weather resistance, good electrical insulation properties, and good process economy.

[0003] Modern heavy trucks have transformed from simple transportation tools into "mobile living spaces," and the quality of the cab's exterior directly impacts user choices. High-end models require exterior panels to meet Class A surface standards (orange peel value Ls≤1.2, gloss ≥90) and achieve "zero-step" matching with the metal skin, posing unprecedented challenges to the dimensional accuracy and surface quality of large composite material components.

[0004] Chinese patent CN114316549B discloses a high compression modulus SMC material, which improves the compression modulus and flame retardant properties of the material by selecting vinyl polyester resin, bisphenol A type unsaturated polyester resin, and spherical fillers, making it suitable for transportation rail components. However, this technical solution mainly focuses on the compression modulus and does not address the shrinkage deformation and surface quality issues of large parts.

[0005] Currently, the application of SMC materials in large high-roof trucks both domestically and internationally faces the following technical challenges: 1) High shrinkage rate, resulting in a 1-2mm gap between large components and the windshield and side panels during assembly, posing a risk of leakage; 2) Poor surface quality, with noticeable surface waviness and exposed fibers; 3) Insufficient modulus, leading to significant deflection in the middle of large roofs, which can cause vibration and abnormal noise during driving. These technical bottlenecks have resulted in a long-term reliance on imports for high-end heavy-duty truck SMC exterior components, leading to high costs and potential supply chain security risks.

[0006] Therefore, developing an SMC material with zero shrinkage, high modulus, and excellent surface quality is of great strategic significance for improving my country's independent supporting capabilities for composite material parts for commercial vehicles. Summary of the Invention

[0007] Purpose of the invention: In order to solve the problems existing in the prior art, the present invention provides a zero-shrinkage high-strength and high-modulus SMC material, its preparation method and application, which not only solves the problems of assembly gaps and warping deformation caused by shrinkage in large parts, but also achieves a synergistic improvement in high strength and high modulus, and the rigidity of the product is significantly better than that of traditional SMC materials.

[0008] Technical Solution: To achieve the above objectives, the present invention may adopt the following technical solution: a zero-shrinkage, high-strength, high-modulus SMC material, comprising the following raw materials in parts by weight: 30-50 parts of unsaturated polyester resin, 25-35 parts of high-modulus polyester resin, 25-35 parts of low-shrinkage control agent, 1-2 parts of curing agent, 4-6 parts of release agent, 125-185 parts of spherical filler, 1-3 parts of thickener, 20-50 parts of glass fiber mat, and 60-100 parts of alkali-free chopped glass fiber.

[0009] Furthermore, the low-shrinkage control agent is one or more of PS, PVAC, and polyurethane-modified PMMA resin.

[0010] More preferably, the low-shrinkage control agent is a polyurethane-modified PMMA resin. The specific modification method is as follows: under the action of an initiator, polyurethane acrylate resin (PUMA) as the flexible chain segment is subjected to a free radical copolymerization reaction with the active monomer methyl methacrylate to generate a modified polymethyl methacrylate resin. The initiator is benzoyl peroxide / N,N-dimethyl-p-toluidine as the initiating system. Because the PUMA and MMA active monomers in the PMMA resin undergo a free radical copolymerization reaction under the action of the initiator to form a cross-linked structure, the cross-linking of the molecular chains causes them to interpenetrate and influence each other, resulting in a strong interaction and improving the performance defects of both.

[0011] Furthermore, the glass fiber mat is made of 200g or 400g glass fiber; the glass fiber is 12.5 mm or 25 mm alkali-free chopped glass fiber.

[0012] Combining glass fiber mat and uninterrupted chopped glass fiber can improve the poor flowability of pure glass fiber mat, which can only be fully laid and easily causes air bubbles on the product surface. At the same time, it can improve the uneven distribution of glass fiber content in different parts of the product during the molding process of pure alkali-free chopped glass fiber. This can not only make the performance of the molded product stable, but also achieve a better process effect.

[0013] Furthermore, the unsaturated polyester resin is one or more of phenolic modified vinyl resin, bisphenol A modified vinyl resin, or maleic anhydride type unsaturated resin.

[0014] Furthermore, the high-modulus polyester resin is one or more of isophthalic unsaturated resin, terephthalic unsaturated resin, or bisphenol A unsaturated polyester resin.

[0015] Furthermore, the curing agent is one or more of TBPB and TBPO; the release agent is one or more of zinc stearate or calcium stearate.

[0016] Furthermore, the spherical filler is one or more of spherical aluminum hydroxide or spherical calcium carbonate powder; the thickener is one or more of magnesium oxide, calcium oxide and magnesium hydroxide.

[0017] The preparation method of the above-mentioned zero-shrinkage, high-strength, and high-modulus SMC material includes the following steps: (1) Resin paste preparation: First, disperse unsaturated polyester resin, high modulus polyester resin, low shrinkage control agent, curing agent, release agent and spherical filler into a uniform resin paste using a high-speed disperser, and then add thickener and mix well. (2) Sheet forming: The dispersed resin paste is evenly scraped onto two nylon films through a sheet forming machine, and then continuous glass fiber mat is laid on the lower nylon film. At the same time, alkali-free short-fiber glass fibers are evenly placed on the glass fiber mat. The glass fiber mat and alkali-free short-fiber glass fibers are pressed in the middle by the nylon films coated with resin paste on the top and bottom to form a "sandwich" structure. (3) Curing: The “sandwich” structure is passed through the impregnation zone, and the resin paste and glass fiber are fully squeezed and rolled up. Finally, the sheet is placed in the drying room to cure to the set viscosity to obtain a zero-shrinkage, high-strength, high-modulus SMC material.

[0018] The present invention also discloses the application of the above-mentioned zero-shrinkage, high-strength, high-modulus SMC material in the preparation of large high-roof heavy trucks.

[0019] Beneficial effects: (1) This invention uses polyurethane modified PMMA as a low-shrinkage control agent, and uses glass fiber mat and chopped glass fiber to construct a sandwich chip material structure. Through the synergistic effect between the chemical modification of the low-shrinkage agent and the innovative design of the reinforcing structure, the prepared SMC material achieves zero shrinkage in a practical sense, with a shrinkage rate ≤0.01%, which is more than twice that of the international advanced level (0.02%-0.05%), solving the problem of assembly gaps and warping deformation caused by shrinkage in large parts; (2) The SMC material prepared by this invention has a flexural modulus ≥12GPa, which is 20% higher than the international advanced level (10-11GPa); tensile strength ≥150MPa, which is 15% higher than the international advanced level (130-140MPa), and achieves a synergistic improvement in high strength and high modulus. The rigidity of the product is significantly better than that of traditional SMC materials; (3) The SMC material prepared by this invention has a gloss level of up to 95 and an orange peel value of 0.8, reaching Class The A+ grade mirror finish surpasses international advanced levels (gloss level 88-92), eliminating the need for post-processing steps such as puttying and sanding, and enabling direct spraying without sanding. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to specific embodiments: The sources of raw materials used in the embodiments and comparative examples are as follows: The unsaturated polyester resin used was MR 14029, purchased from Changzhou Aiketan Composite Materials Co., Ltd. The high-modulus polyester resin used was DERAKANE 782, purchased from Changzhou Aiketan Composite Materials Co., Ltd. Polyurethane modified PMMA resin: self-made, the preparation method is as follows: under the action of an initiator, polyurethane acrylate resin PUMA as the flexible chain segment is subjected to free radical copolymerization reaction with active monomer methyl methacrylate to generate modified polymethyl methacrylate resin. The initiator is benzoyl peroxide / N,N-dimethyl-p-toluidine as the initiation system.

[0021] Ordinary PMMA resin, purchased from Jinling Lilians Resin Co., Ltd., H 856-902; The specific usage of the low shrinkage control agent, 870-901, was purchased from Jinling Liliansi Resin Co., Ltd. The curing agent used was TBPB, purchased from Jiangsu Qiangsheng Functional Chemical Co., Ltd. Release agent: Zinc stearate, industrial grade; Spherical filler: Spherical aluminum hydroxide, industrial grade; Thickener: Magnesium oxide, industrial grade; Fiberglass mat: 400g / m², industrial grade; Alkali-free chopped glass fiber: 25mm length, industrial grade.

[0022] The basic preparation methods in the examples and comparative examples are as follows: (1) Resin paste preparation: Unsaturated polyester resin, high modulus polyester resin, curing agent, release agent and spherical filler are put into a high-speed shear mixer and stirred at 1000 rpm for 8 minutes to disperse evenly. Then, magnesium oxide thickener is added and stirred at high speed for 1 minute to obtain resin paste. (2) Sheet forming: The dispersed resin paste is evenly coated onto two nylon films through a sheet forming machine. Then, continuous glass fiber mat is laid on the lower nylon film. At the same time, 25 mm long alkali-free chopped glass fibers are evenly dropped onto the glass fiber mat. The glass fiber mat and chopped fibers are pressed in the middle by the nylon films coated with resin paste on the top and bottom to form a sandwich structure. (3) Curing: The sandwich structure is squeezed and rolled up through the impregnation area and placed in a 50℃ curing chamber for 12 hours to obtain the final product.

[0023] Example 1: A zero-shrinkage, high-strength, high-modulus SMC material, comprising the following raw materials in parts by weight: 40 parts unsaturated polyester resin, 30 parts high-modulus polyester resin, 30 parts polyurethane-modified PMMA resin, 1.5 parts curing agent, 5.5 parts release agent, 160 parts spherical filler, 1.5 parts thickener, 40 parts glass fiber mat, and 80 parts alkali-free chopped glass fiber.

[0024] Example 2: A zero-shrinkage, high-strength, high-modulus SMC material, comprising the following raw materials in parts by weight: 40 parts unsaturated polyester resin, 30 parts high-modulus polyester resin, 30 parts PS, 1.5 parts curing agent, 5.5 parts release agent, 160 parts spherical filler, 1.5 parts thickener, 40 parts glass fiber mat, and 80 parts alkali-free chopped glass fiber.

[0025] Example 3: A zero-shrinkage, high-strength, high-modulus SMC material, comprising the following raw materials in parts by weight: 40 parts unsaturated polyester resin, 30 parts high-modulus polyester resin, 40 parts polyurethane-modified PMMA resin, 1.5 parts curing agent, 5.5 parts release agent, 160 parts spherical filler, 1.5 parts thickener, 40 parts glass fiber mat, and 80 parts alkali-free chopped glass fiber.

[0026] Example 4: A zero-shrinkage, high-strength, high-modulus SMC material, comprising the following raw materials in parts by weight: 40 parts unsaturated polyester resin, 30 parts high-modulus polyester resin, 30 parts PVAC, 1.5 parts curing agent, 5.5 parts release agent, 160 parts spherical filler, 1.5 parts thickener, 40 parts glass fiber mat, and 80 parts alkali-free chopped glass fiber.

[0027] Example 5: A zero-shrinkage, high-strength, high-modulus SMC material, comprising the following raw materials in parts by weight: 40 parts unsaturated polyester resin, 30 parts high-modulus polyester resin, 30 parts polyurethane-modified PMMA resin, 1.5 parts curing agent, 5.5 parts release agent, 180 parts spherical filler, 1.5 parts thickener, 40 parts glass fiber mat, and 80 parts alkali-free chopped glass fiber.

[0028] Comparative Example 1: A zero-shrinkage, high-strength, high-modulus SMC material, comprising the following raw materials in parts by weight: 40 parts unsaturated polyester resin, 30 parts high-modulus polyester resin, 30 parts polyurethane-modified PMMA resin, 1.5 parts curing agent, 5.5 parts release agent, 160 parts spherical filler, 1.5 parts thickener, and 120 parts alkali-free chopped glass fiber. The difference from Example 1 is that it does not contain glass fiber mat.

[0029] Comparative Example 2: A zero-shrinkage, high-strength, high-modulus SMC material, comprising the following raw materials in parts by weight: 40 parts unsaturated polyester resin, 30 parts high-modulus polyester resin, 30 parts ordinary PMMA resin, 1.5 parts curing agent, 5.5 parts release agent, 160 parts spherical filler, 1.5 parts thickener, 40 parts glass fiber mat, and 80 parts alkali-free chopped glass fiber. The difference from Example 1 is that 30 parts of ordinary PMMA resin were used instead of polyurethane-modified PMMA resin.

[0030] The specific raw materials and formulations are shown in Table 1:

[0031] The SMC material sheets prepared in Examples 1-5 and Comparative Examples 1-2 were tested for shrinkage, tensile strength, flexural strength, flexural modulus, impact strength, surface gloss, and orange peel value. The testing standards are as follows: 1. Shrinkage rate testing standard: Refer to standard GB / T 15568-2024. 2. Mechanical strength testing standard: Refer to standard GB / T 23641-2018 3. Surface gloss testing standard: Refer to standard GB / T 9754-2007 4. Orange peel value test standard: Refer to standard GB / T 37358-2019.

[0032] The test results are shown in Table 2:

[0033] The comparison data in Table 2 shows that: 1) The use of different low-shrinkage agents (Example 1 used polyurethane-modified PMMA resin, Example 2 used PS, Example 4 used PVAC, and Comparative Example 2 used ordinary PMMA resin) showed that polyurethane-modified PMMA resin had the best effect. 2) A comparison of different amounts of low shrinkage agent shows that 30 parts (Example 3) is the optimal amount. Increasing the amount does not achieve a lower shrinkage effect, but instead it will precipitate on the product surface, thereby affecting the surface gloss and orange peel value of the product. 3) A comparison of different filler dosages shows that increasing the filler dosage (Example 5) will affect the strength of the material and weaken the interfacial bonding force between the resin phase and the filler. 4) Combining glass fiber mat and uninterrupted glass fiber can improve the stability of molded product performance and achieve better process results. As can be seen from the data comparison of Comparative Example 1, the strength of the material without glass fiber mat is reduced and the values ​​fluctuate greatly, which is not conducive to the stability of the product.

Claims

1. A zero-shrinkage, high-strength, high-modulus SMC material, characterized in that... The preparation materials include the following parts by weight: 30-50 parts unsaturated polyester resin, 25-35 parts high modulus polyester resin, 25-35 parts low shrinkage control agent, 1-2 parts curing agent, 4-6 parts release agent, 125-185 parts spherical filler, 1-3 parts thickener, 20-50 parts glass fiber mat, and 60-100 parts alkali-free chopped glass fiber.

2. The zero-shrinkage, high-strength, high-modulus SMC material according to claim 1, characterized in that: The low-shrinkage control agent is one or more of PS, PVAC, and polyurethane-modified PMMA resin.

3. The zero-shrinkage, high-strength, high-modulus SMC material according to claim 1 or 2, characterized in that: The low-shrinkage control agent is a polyurethane-modified PMMA resin, and the specific modification method is as follows: Under the action of an initiator, polyurethane acrylate resin (PUMA) as the flexible chain segment is subjected to a free radical copolymerization reaction with the active monomer methyl methacrylate to generate modified polymethyl methacrylate resin. The initiator is benzoyl peroxide / N,N-dimethyl-p-toluidine as the initiation system.

4. The zero-shrinkage, high-strength, high-modulus SMC material according to claim 1, characterized in that: The glass fiber mat is made of 200g or 400g glass fiber; the glass fiber is 12.5 mm or 25 mm alkali-free chopped glass fiber.

5. The zero-shrinkage, high-strength, high-modulus SMC material according to claim 1, characterized in that: The unsaturated polyester resin is one or more of phenolic modified vinyl resin, bisphenol A modified vinyl resin, or maleic anhydride type unsaturated resin.

6. The zero-shrinkage, high-strength, high-modulus SMC material according to claim 1, characterized in that: The high-modulus polyester resin is one or more of isophthalic unsaturated resin, terephthalic unsaturated resin, or bisphenol A unsaturated polyester resin.

7. The zero-shrinkage, high-strength, high-modulus SMC material according to claim 1, characterized in that: The curing agent is one or more of TBPB and TBPO; the release agent is one or more of zinc stearate or calcium stearate.

8. The zero-shrinkage, high-strength, high-modulus SMC material according to claim 1, characterized in that: The spherical filler is one or more of spherical aluminum hydroxide or spherical calcium carbonate powder; the thickener is one or more of magnesium oxide, calcium oxide and magnesium hydroxide.

9. A method for preparing a zero-shrinkage, high-strength, high-modulus SMC material according to any one of claims 1-8, characterized in that... Includes the following steps: (1) Resin paste preparation: First, disperse unsaturated polyester resin, high modulus polyester resin, low shrinkage control agent, curing agent, release agent and spherical filler into a uniform resin paste using a high-speed disperser, and then add thickener and mix well. (2) Sheet forming: The dispersed resin paste is evenly scraped onto two nylon films through a sheet forming machine, and then continuous glass fiber mat is laid on the lower nylon film. At the same time, alkali-free short-fiber glass fibers are evenly placed on the glass fiber mat. The glass fiber mat and alkali-free short-fiber glass fibers are pressed in the middle by the nylon films coated with resin paste on the top and bottom to form a "sandwich" structure. (3) Curing: The "sandwich" structure is passed through the impregnation zone, and the resin paste and glass fiber are fully squeezed and rolled up. Finally, the sheet is placed in the drying room to cure to the set viscosity to obtain a zero-shrinkage, high-strength, high-modulus SMC material.

10. The application of the zero-shrinkage, high-strength, high-modulus SMC material as described in any one of claims 1-8 or prepared according to claim 9 in the preparation of large high-roof heavy trucks.

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