Thermal expansion epoxy sheet molding compound and production process and application thereof

Abstract

According to the thermally expandable epoxy sheet molding compound and the production process and application thereof, through synergistic compounding of bisphenol A epoxy resin and methylphenol novolac epoxy resin and optimal combination of loose foaming microspheres and short carbon fibers, the thermal expansion performance and mechanical strength of the material are remarkably improved; the foaming microspheres are uniformly expanded when heated at the temperature of 120 DEG C or above, the volume multiplying power of 3-5 times can be achieved, and the filling requirement of a special-shaped structure is met; the composite use of the short carbon fibers and the glass beads enables the density of a plate product to be reduced to 1.2 g / cm < 3 > or below, which is reduced by 20% or above compared with that of a traditional carbon fiber prepreg, so that the cost of raw materials is effectively reduced; the Tg point of the cured material is greater than 140 DEG C, and the thermal deformation temperature exceeds 150 DEG C, so that the stability of a high-temperature molding process is ensured. In addition, through step-by-step component addition and high-speed shearing and stirring in the kneading process, the problem of non-uniform dispersion of the foaming agent and the resin is solved, and the consistency of the performance of the product is ensured.

Description

Technical Field

[0001] The invention relates to the field of new materials, and in particular to a heat expandable epoxy sheet molding compound and a production process and application thereof. Background Art

[0002] Epoxy molding compounds are widely used in aerospace, automotive and electronic packaging fields due to their excellent mechanical properties, heat resistance and processing adaptability. Traditional epoxy molding compounds are mostly made of a single resin matrix (such as bisphenol A epoxy resin) and fiber reinforcement materials, but they have problems such as insufficient thermal expansion performance, high density and high cost. For example, although existing carbon fiber prepreg composite materials have high strength, their density is generally higher than 1.5g / cm 3 , and a large amount of carbon fiber is required during the preparation process, resulting in high costs. In addition, the thermal expansion ratio of conventional epoxy molding compounds is usually less than 2 times, which makes it difficult to meet the volume expansion requirements in the core filling or co-curing process of special-shaped structural parts.

[0003] In the prior art, some improvement schemes attempt to reduce the density of the material by adding foaming agents or low-density fillers (such as hollow glass microspheres), but the mechanical properties of the products are often significantly reduced due to uneven dispersion of the foaming agent or poor compatibility with the resin. For example, when using a single foaming agent, it is difficult to stably achieve an expansion ratio of more than 3 times, and the heat deformation temperature (HDT) of the foamed material is often lower than 120°C, which cannot meet the requirements of high-temperature molding processes. At the same time, the matching of the curing agent and the accelerator in the traditional formula is insufficient, which can easily cause incomplete curing or uncontrollable reaction rate, affecting production efficiency and product quality.

[0004] Therefore, how to develop an epoxy molding compound that has high expansion ratio, low density, high heat resistance and controllable cost has become a technical problem that needs to be solved urgently in this field. Summary of the invention

[0005] The purpose of the present invention is to provide a heat expandable epoxy sheet molding compound and a production process and application thereof, so as to solve the problems existing in the above-mentioned prior art.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] The invention provides a heat expandable epoxy sheet molding compound, which comprises the following components in percentage by mass: 30-50% of bisphenol A epoxy resin, 30-50% of methylphenol novolac epoxy resin, 6-10% of polyvinyl butyral, 4-6% of dicyandiamide curing agent, 1-2% of modified urea accelerator, 2-6% of Matsumoto foaming microspheres, 15-35% of carbon fiber staple fibers, 10-15% of glass microspheres and 0.5-1% of carbon black.

[0008] Preferably, it comprises components in the following mass percentages: bisphenol A epoxy resin 30%, cresol novolac epoxy resin 30%, polyvinyl butyral 6%, dicyandiamide curing agent 4%, modified urea accelerator 1%, Matsumoto microballoons 2%, short carbon fiber 16.5%, glass microbeads 10%, carbon black 0.5%.

[0009] Preferably, it comprises components in the following mass percentages: bisphenol A epoxy resin 30%, cresol novolac epoxy resin 30%, polyvinyl butyral 6%, dicyandiamide curing agent 4%, modified urea accelerator 1%, Matsumoto microballoons 3%, short carbon fiber 15%, glass microbeads 10%, carbon black 1%.

[0010] Preferably, it comprises components in the following mass percentages: bisphenol A epoxy resin 30%, cresol novolac epoxy resin 30%, polyvinyl butyral 6%, dicyandiamide curing agent 4%, modified urea accelerator 1%, Matsumoto microballoons 2%, short carbon fiber 16%, glass microbeads 10%, carbon black 1%.

[0011] The present invention also provides a production process of a thermally expandable epoxy sheet molding compound, comprising the following steps:

[0012] S1. Melting bisphenol A epoxy resin, cresol novolac epoxy resin and polyvinyl butyral at 140 - 160 °C and carrying out high-speed shearing and stirring to form a homogeneous viscous liquid of mixed resin;

[0013] S2. After cooling the mixed resin to 80 °C, kneading it with dicyandiamide curing agent, modified urea accelerator, carbon black and Matsumoto microballoons in a kneader;

[0014] S3. Adding short carbon fiber and glass microbeads and continuing to knead;

[0015] S4. Pressing the kneaded material into a uniform sheet, cutting it into finished products, and storing it sealed at a temperature below 0 °C.

[0016] Preferably, in step S1, the rotation speed of the shearing and stirring is greater than 1500 revolutions per minute, and the diameter of the stirring disk is greater than 20 cm.

[0017] Preferably, in step S2, the kneading time is 5 minutes.

[0018] Preferably, in step S3, the kneading time is 40 minutes.

[0019] The present invention also provides an application of the thermally expandable epoxy sheet molding compound, which is used as an inner core when molding special-shaped epoxy plates, and the outer skin is carbon fiber prepreg, and they are co-cured into a structural material.

[0020] The present invention also provides an application of the thermally expandable epoxy sheet molding compound, which is used for structural filling of the corners of molded products.

[0021] The present invention has achieved the following beneficial technical effects compared with the prior art:

[0022] In the components of the present invention, bisphenol A epoxy resin is used as the matrix resin to provide the main structure and thermosetting properties of the material; methylphenol novolac epoxy resin acts synergistically with bisphenol A epoxy resin to enhance the high-temperature resistance and thermal expansion characteristics; polyvinyl butyral is used as a toughening agent to improve the flexibility and processing fluidity of the resin system; dicyandiamide curing agent is used to initiate the curing reaction of the epoxy resin; modified urea accelerator accelerates the curing reaction process; Matsumoto microballoons are used as a thermal expander, which expands when heated above 120°C, achieving a 3-5 times increase in the volume magnification of the material; short carbon fiber is used as a reinforcing material to improve the mechanical strength and reduce the density of the final product; glass microspheres are used as fillers to further reduce the density and improve the dimensional stability; carbon black is used to adjust the color and uniformly disperse other components.

[0023] A thermally expandable epoxy sheet molding compound provided by the present invention, its production process and application, through the synergistic compounding of bisphenol A epoxy resin and methylphenol novolac epoxy resin, combined with the optimized combination of Matsumoto microballoons and short carbon fiber, significantly improve the thermal expansion performance and mechanical strength of the material;, Matsumoto microballoons expand uniformly when heated above 120°C, and a volume magnification of 3-5 times can be achieved to meet the filling requirements of special-shaped structures; the combined use of short carbon fiber and glass microspheres reduces the density of the sheet product to 1.2 g / cm 3 The following is more than 20% lower than that of traditional carbon fiber prepreg, effectively reducing the raw material cost; the Tg point of the cured material is greater than 140°C, and the heat distortion temperature exceeds 150°C, ensuring the stability of the high-temperature compression molding process. In addition, by adding components step by step and high-speed shear stirring in the kneading process, the problem of uneven dispersion of the blowing agent and the resin is solved, ensuring the consistency of the product performance. Detailed implementation manners

[0024] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0025] The purpose of the present invention is to provide a thermally expandable epoxy sheet molding compound, its production process and application to solve the problems existing in the prior art.

[0026] In order to make the above objects, features and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with specific implementation manners.

[0027] Example 1:

[0028] This example provides a heat-expandable epoxy sheet molding compound, which includes the following components by mass percentage: bisphenol A epoxy resin 30%, methylphenol phenolic epoxy resin 30%, polyvinyl butyral 6%, dicyandiamide curing agent 4%, modified urea accelerator 1%, Matsumoto microspheres 2%, short carbon fiber 16.5%, glass microspheres 10%, carbon black 0.5%.

[0029] This example also provides a production process for the above heat-expandable epoxy sheet molding compound, including the following steps:

[0030] S1. Melt bisphenol A epoxy resin, methylphenol phenolic epoxy resin and polyvinyl butyral at 150°C for 1.5 hours, and perform high-speed shear stirring. The rotation speed of the shear stirring is greater than 1600 revolutions per minute, and the diameter of the stirring disk is 30 cm to form a homogeneous viscous liquid mixed resin;

[0031] S2. After cooling the mixed resin to 80°C, knead it with dicyandiamide curing agent, modified urea accelerator, carbon black and Matsumoto microspheres in a kneader for 5 minutes;

[0032] S3. Add short carbon fiber and glass microspheres, and continue to knead for 40 minutes;

[0033] S4. Press the kneaded material into a uniform sheet, cut it into finished products with a specification of 50*80, seal it and store it below 0°C.

[0034] Example 2:

[0035] This example provides a heat-expandable epoxy sheet molding compound, which includes the following components by mass percentage: bisphenol A epoxy resin 30%, methylphenol phenolic epoxy resin 30%, polyvinyl butyral 6%, dicyandiamide curing agent 4%, modified urea accelerator 1%, Matsumoto microspheres 3%, short carbon fiber 15%, glass microspheres 10%, carbon black 1%.

[0036] This example also provides a production process for the above heat-expandable epoxy sheet molding compound, including the following steps:

[0037] S1. Melt bisphenol A epoxy resin, methylphenol phenolic epoxy resin and polyvinyl butyral at 150°C for 1.5 hours, and perform high-speed shear stirring. The rotation speed of the shear stirring is greater than 1600 revolutions per minute, and the diameter of the stirring disk is 30 cm to form a homogeneous viscous liquid mixed resin;

[0038] S2. After cooling the mixed resin to 80°C, knead it with dicyandiamide curing agent, modified urea accelerator, carbon black and Matsumoto microspheres in a kneader for 5 minutes;

[0039] S3. Add short carbon fibers and glass microspheres and continue kneading for 40 minutes;

[0040] S4. Press the kneaded material into a uniform sheet, cut it into finished products with a specification of 50*80, seal it and store it below 0°C.

[0041] Example 3:

[0042] This example provides a heat-expandable epoxy sheet molding compound, which includes the following components by mass percentage: 30% of bisphenol A epoxy resin, 30% of methylphenol phenolic epoxy resin, 6% of polyvinyl butyral, 4% of dicyandiamide curing agent, 1% of modified urea accelerator, 2% of Matsumoto foaming microspheres, 16% of short carbon fibers, 10% of glass microspheres, and 1% of carbon black.

[0043] This example also provides the production process of the above heat-expandable epoxy sheet molding compound, including the following steps:

[0044] S1. Melt bisphenol A epoxy resin, methylphenol phenolic epoxy resin and polyvinyl butyral at 150°C for 1.5 hours, and carry out high-speed shearing and stirring. The rotation speed of the shearing and stirring is greater than 1600 revolutions per minute, and the diameter of the stirring disk is 30 cm to form a homogeneous viscous liquid mixed resin;

[0045] S2. After cooling the mixed resin to 80°C, knead it with dicyandiamide curing agent, modified urea accelerator, carbon black and Matsumoto foaming microspheres in a kneader for 5 minutes;

[0046] S3. Add short carbon fibers and glass microspheres and continue kneading for 40 minutes;

[0047] S4. Press the kneaded material into a uniform sheet, cut it into finished products with a specification of 50*80, seal it and store it below 0°C.

[0048] The heat-expandable epoxy sheet molding compounds in the above Examples 1-3 can be used as the inner core when molding special-shaped epoxy plates, and the outer skin is carbon fiber prepreg, and co-cured into a structural material; it can also be used for structural filling of the corners of molded products. The use process is that the molding temperature is greater than 120°C for heat expansion, and the expansion ratio is 3-5 times; after curing, the Tg point is greater than 140°C, and the heat distortion temperature is greater than 150°C, and it can be thermally demolded. The density of the material itself is about 0.9, and the density of the plate product is about 1.2, which is beneficial to reducing the density of carbon fiber molded products, reducing the use of carbon fiber, and reducing costs.

[0049] The present invention uses specific examples to illustrate the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation on the present invention.

Claims

1. A heat-expandable epoxy sheet molding compound, characterized in that: It comprises components in the following mass percentages: bisphenol A epoxy resin 30 - 50%, methylphenol novolac epoxy resin 30 - 50%, polyvinyl butyral 6 - 10%, dicyandiamide curing agent 4 - 6%, modified urea accelerator 1 - 2%, Matsumoto microballoons 2 - 6%, short carbon fiber 15 - 35%, glass microbeads 10 - 15%, carbon black 0.5 - 1%.

2. The heat-expandable epoxy sheet molding compound according to claim 1, wherein: It comprises components in the following mass percentages: bisphenol A epoxy resin 30%, methylphenol novolac epoxy resin 30%, polyvinyl butyral 6%, dicyandiamide curing agent 4%, modified urea accelerator 1%, Matsumoto microballoons 2%, short carbon fiber 16.5%, glass microbeads 10%, carbon black 0.5%.

3. The heat-expandable epoxy sheet molding compound according to claim 1, characterized in that: It comprises components in the following mass percentages: bisphenol A epoxy resin 30%, methylphenol novolac epoxy resin 30%, polyvinyl butyral 6%, dicyandiamide curing agent 4%, modified urea accelerator 1%, Matsumoto microballoons 3%, short carbon fiber 15%, glass microbeads 10%, carbon black 1%.

4. The heat-expandable epoxy sheet molding compound according to claim 1, wherein: It comprises components in the following mass percentages: bisphenol A epoxy resin 30%, methylphenol novolac epoxy resin 30%, polyvinyl butyral 6%, dicyandiamide curing agent 4%, modified urea accelerator 1%, Matsumoto microballoons 2%, short carbon fiber 16%, glass microbeads 10%, carbon black 1%.

5. A production process of a heat-expandable epoxy sheet molding compound, characterized in that: It comprises the following steps: S1. Melt bisphenol A epoxy resin, methylphenol novolac epoxy resin and polyvinyl butyral at 140 - 160 °C and stir at high speed with shearing to form a homogeneous viscous liquid of mixed resin; S2. After cooling the mixed resin to 80 °C, knead it with dicyandiamide curing agent, modified urea accelerator, carbon black and Matsumoto microballoons in a kneader; S3. Add short carbon fiber and glass microbeads and continue kneading; S4. Press the kneaded material into a uniform sheet, cut it into finished products, and store it sealed below 0 °C.

6. The production process of the heat-expandable epoxy sheet molding compound according to claim 5, characterized in that: In step S1, the rotation speed of the shearing and stirring is greater than 1500 revolutions per minute, and the diameter of the stirring disk is greater than 20 cm.

7. The production process of the thermally expandable epoxy sheet molding compound according to claim 5, characterized in that: In step S2, the kneading time is 5 minutes.

8. The production process of the heat-expandable epoxy sheet molding compound according to claim 5, characterized in that: In step S3, the kneading time is 40 minutes.

9. Application of a thermally expandable epoxy sheet molding compound, characterized in that: It is used as the inner core when molding special-shaped epoxy sheets, and the outer skin is carbon fiber prepreg, which is co-cured into a structural material.

10. Application of a thermally expandable epoxy sheet molding compound, characterized in that: It is used for structural filling of the corners of molded products.