Toughened-modified composite material and a layered composite material

Abstract

In order to provide a toughened composite material (100) comprising a main matrix (10), in particular a semi-crystalline matrix, wherein the main matrix (10) comprises an amorphous high-temperature polymer (11), which has a toughening modification and thus reduces embrittlement of the composite material, it is proposed that at least one toughening-modifying additive (12) is incorporated into the amorphous high-temperature polymer (11), wherein the toughening-modifying additive (12) is in particular beta-polypropylene (13).

Description

The invention relates to a toughened composite material. Furthermore, the invention relates to a layered composite material as an electrical insulation material comprising a toughened composite material. Composite materials are known, for example, from EP 3 286 276 B1, DE 10 2016 208 923 A1, EP 4 491 395 A1 and JP 2022 165 638 A. EP 3 286 276 B1 describes a thermally curing, delta-alpha tolerant plastic composition, wherein the adhesive composition contains particles of β-nucleating agent-containing polypropylene and / or β-nucleated polypropylene and the adhesive base consists of epoxy resin. DE 10 2016 208 923 A1 describes a potting compound for electronic components which has a plastic main matrix, wherein polypropylene plastic particles with a beta-crystalline structure are incorporated into the plastic main matrix. EP 4 491 395 A1 relates to a polypropylene composition comprising a highly isotactic homopolymer of polypropylene in a proportion of 70 to less than 95 wt.%, a cyclic olefin polymer composition in a proportion of 5 to less than 30 wt.%, and a nucleating agent in a proportion of 0.0000001 to 1 wt.%. The present invention further relates to a cast film containing the polypropylene composition and a biaxially oriented film containing the polypropylene composition. In addition, a capacitor containing the biaxially oriented film is provided. From JP 2022 165 638 A, the provision of a film with higher dielectric strength and insulation at high temperatures is disclosed. A film is provided that contains a layer of syndiotactic polystyrene, a polyphenylene ether, and an amorphous or atactic polystyrene, and exhibits a peak of approximately 4.9 nm⁻¹ of the wide-angle X-ray scattering profile of the film. German patent DE 10 2024 203 849 A1 describes a material for electrical insulation comprising syndiotactic polystyrene, beta-polypropylene particles and / or beta-polypropylene fibers. Furthermore, an electronic component comprising at least one material for electrical insulation according to the present invention and the use of the material for electrical insulation are disclosed. In composite materials containing high-temperature polymers, aging effects can occur, which, for example, can cause the material to become brittle through post-crystallization. This is particularly relevant for insulation materials used in electric motors, as these can reach operating temperatures of approximately 180 °C. Furthermore, such electric motors contain, for example, electrically insulating oils for cooling, which can also cause aging effects in the insulation materials. The invention is based on the objective of creating a toughened composite material in which embrittlement of the composite material is reduced. To solve the problem underlying the invention, a toughened composite material comprising a main matrix, in particular a semi-crystalline matrix, wherein the main matrix comprises an amorphous high-temperature polymer, is proposed, wherein at least one toughening additive is incorporated into the amorphous high-temperature polymer, wherein the toughening additive is beta-polypropylene. A tough-modified composite material, as understood by those skilled in the art, is a material consisting of several components, wherein at least one component of the composite, which is in particular polymeric, exhibits tough or ductile material behavior. A main matrix, as understood by those skilled in the art, is the primary component that serves as the structural framework or carrier medium of the viscous-modified composite material. The properties of the main matrix include, in particular, high partial discharge resistance and suitability as an electrical insulating material. An amorphous high-temperature polymer is defined here as a polymer that remains stable at high temperatures and does not exhibit a pronounced crystalline structure. This amorphous high-performance polymer has a glass transition temperature preferably of at least 200 °C, making it thermally and mechanically resistant. Due to its amorphous structure, it exhibits isotropic material properties and offers high dimensional stability, i.e., no or only minimal shrinkage. High-temperature polymers also exhibit high resistance to thermal degradation. A toughening additive is a substance that alters the toughness of a material and is sensitive to oxygen. Oxygen sensitivity means that the additive reacts chemically or physically with oxygen, leading to a change in its properties. The advantage of the toughening-modified composite material according to the invention arises from the combination of the individual components. The main matrix tends to recrystallize under thermal stress, resulting in (additional) crystalline components. These (additional) crystalline components cause mechanical stresses, which in the worst case can lead to embrittlement of the material. While these stresses are compensated by the introduction of beta-polypropylene into the main matrix, polypropylene is susceptible to oxidative aging and has a low melting point of approximately 150 °C, which is lower than that of potential main matrices.These disadvantages can be compensated for by incorporating beta-polypropylene into the amorphous high-temperature polymer. For example, little to no oxygen reaches the beta-polypropylene. If the main matrix is, for example, semi-crystalline, there is a risk of cracking and thus also a tendency of the main matrix to become brittle. Preferably, the beta-polypropylene is an isotactic beta-polypropylene, i.e., essentially all methyl groups of the propylene molecules are arranged on the same side with respect to the main chain. Beta-polypropylene has a modified crystal structure with a higher proportion of β-crystallinity, resulting in improved impact strength, ductility, and elasticity—especially at low temperatures. Beta-polypropylene is produced, among other methods, by using beta-nucleating agents, leading to the formation of beta-spherulites. For example, beta-polypropylene is incorporated in fiber and / or particle form. The use of beta-polypropylene in fiber form can contribute to the reduction of crystallization-induced mechanical stresses in the main matrix material and result in higher toughness of the composite material. Beta-polypropylene fibers can support force transmission within the material and increase its toughness. Beta-polypropylene in particle form is particularly easy to incorporate and distributes very evenly, and also increases the toughness of the composite system. Beta-polypropylene fibers and beta-polypropylene particles can therefore be advantageously combined. If the beta-polypropylene is present as a fiber embedded in a polymer matrix, it can be further reduced by the application of mechanical stress or...When a force is introduced from the matrix into the beta-polypropylene fiber, microscopically small pores are formed in the beta-polypropylene fiber, which absorb the generated or released energy under mechanical stress - in accordance with the tough / ductile material behavior. For example, the beta-polypropylene fibers have a length of 1 nm to 100 mm, preferably 0.1 mm to 35 mm, and particularly preferably 1 mm to 20 mm, with a diameter of 1 nm to 10 mm, preferably 0.1 mm to 1 mm, and / or the beta-polypropylene particles have a diameter of 1 nm to 50 mm, preferably 0.1 mm to 35 mm, and particularly preferably 0.1 mm to 2 mm. Shorter fibers, for example, promote more uniform distribution and interaction within the amorphous high-temperature polymer, while longer fibers offer stabilizing properties that increase the toughness of the material. Smaller particles achieve more efficient dispersion within the matrix and thereby promote structural cohesion, while larger particles contribute to additional reinforcement and stability. For example, the beta-polypropylene is phase-separated from the surrounding amorphous high-temperature polymer. Phase-separated, as understood by those skilled in the art, means that the beta-polypropylene and the amorphous high-temperature polymer are present without completely mixing. The phase separation can be pronounced macroscopically or microscopically and affects the physical, chemical, or mechanical properties of the material. Phase separation can occur, for example, at high temperatures of around 180 °C when the beta-polypropylene is liquid and the amorphous high-temperature polymer is solid. According to the invention, the main matrix is ​​selected from a list comprising: polyethylene naphthalate (PEN), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), fluoroethylene propylene (FEP), syndiotactic polystyrene (syndiotactic PS), or a combination thereof. This group of high-temperature polymers can offer individual as well as combined advantages. Polyethylene naphthalate exhibits high thermal resistance and high resistance to chemical or media influences. Cycloolefin copolymer is characterized by high optical clarity and low water absorption, making it suitable for applications requiring these properties, such as electrical insulation materials. Polyethylene terephthalate and polybutylene terephthalate provide further matrix options and offer mechanical stability and thermal resistance. Fluoroethylene propylene offers excellent chemical resistance, while syndiotactic polystyrene has advantages in thermal stability and stiffness. The polymer options can be combined according to the requirements of a specific application to optimize the performance and versatility of the composite material. Polyethylene naphthalate (PEN) is preferably used as the main matrix. For example, the amorphous high-temperature polymer can consist of polyetherimide (PEI), polyphenylene ether (PPE), a polyphenylene ether (PPE) / polystyrene (PS) blend and / or a combination of these. Polyetherimide offers good thermal stability and high mechanical strength, making it suitable for applications with high thermal demands. Polyphenylene ether provides high dimensional stability and low water absorption, which supports the long-term stability of the material structure. A polyphenylene ether / polystyrene blend can combine the advantages of both polymers by uniting the thermal stability and mechanical strength of polyphenylene ether with the processability and impact strength of polystyrene. Such blends offer a beneficial balance of structural integrity and functional properties and are flexible in their application. The composite material exhibits a balanced mix of thermal, chemical, and mechanical resistance and is well-suited for electrical insulation applications. The selection and combination of these polymers allows for customized solutions to meet the requirements of various industrial environments and leverage the functional advantages of the composite material. For example, the toughened composite material comprises at least 50 wt.% of the main matrix, at least 10 wt.% of the amorphous high-temperature polymer and at least 0.1 wt.% beta-polypropylene, preferably at least 64.9 wt.% of the main matrix, at least 10 wt.% of the amorphous high-temperature polymer and at least 0.1 wt.% beta-polypropylene. Preferably, the toughened composite material comprises 50 to 89.9 wt.% of the main matrix, 10 to 35 wt.% of the amorphous high-temperature polymer, and 0.1 to 15 wt.% of beta-polypropylene; more preferably, it comprises 64.9 to 89.9 wt.% of the main matrix, 10 to 35 wt.% of the amorphous high-temperature polymer, and 0.1 to 15 wt.% of beta-polypropylene. The wt.% values ​​are based on the total mass of the toughened composite material. A person skilled in the art can select the ranges such that the upper and lower limits can be combined as desired. In conjunction with the wt.% values, the term "comprising" can also be used to mean "consisting of." Another solution to the underlying problem involves a layered composite material comprising a toughened composite material, wherein the toughened composite material is arranged in a core layer, and the core layer is sandwiched between at least two adhesive layers, which are expandable, particularly by heat. This preserves the insulating properties of the toughened composite material, and the material can be positively integrated into corresponding applications. For example, such a layered composite material can be used as insulation between the slot base and stator windings, thus serving as an additional insulating layer between the stator slot base and the wound conductors. For example, the at least two expandable adhesive layers are each surrounded by a porous top layer. Top layers can protect the sensitive composite material from external influences and thus make it more durable. The invention is explained in more detail below with reference to the accompanying figures. Figure 1 shows a schematic representation of a toughened composite material, and Figure 2 shows a schematic representation of a layered composite material comprising a toughened composite material. Fig. 1 shows a schematic representation of a toughened composite material 100. The toughened composite material 100 comprises the main matrix 10, in which an amorphous high-temperature polymer 11 is incorporated. A toughening additive 12, beta-polypropylene 13, is incorporated into the amorphous high-temperature polymer 11. Polyethylene naphthalate (PEN) is used as the main matrix 10 at a rate of 65 wt%. The amorphous high-temperature polymer 11 incorporated into the main matrix is ​​polyetherimide (PEI) at a rate of 25 wt%. The additive 12 is isotactic beta-polypropylene 13, which has a modified crystal structure with a higher degree of β-crystallinity. Isotactic beta-polypropylene is present in a proportion of 10 wt.%.If the toughened composite material 100 is used, for example, as insulation in a stator, temperatures exceeding 180 °C can occur. This can cause post-crystallization of the PEN matrix of the main matrix 10, leading to mechanical stresses that, in turn, can result in typical aging phenomena such as cracking. To compensate for stresses in the main matrix 10, which arise, for example, from post-crystallization (since crystalline regions have a higher crystallinity compared to amorphous regions), isotactic beta-polypropylene 13 is used. This polypropylene has a relatively low melting point of approximately 150 °C and is phase-separated within the amorphous high-temperature polymer 11. This also protects the isotactic beta-polypropylene 13 from oxidation, as it is completely encapsulated by the high-temperature polymer 11.The use of a combination of isotactic beta-polypropylene fibers 14 with a length of about 10 mm and a diameter of about 0.5 mm, and isotactic beta-polypropylene particles 15 with a diameter of about 1 mm has proven to be particularly efficient. Figure 2 shows a schematic representation of a layered composite material 200 comprising the toughened composite material 100 from Figure 1. The toughened composite material 100 is arranged in a core layer 16. The core layer 16, in turn, is arranged between two expandable adhesive layers 17. This arrangement allows the layered composite material 200 to be inserted into spaces, and the expandable adhesive layers 17 can then be irreversibly expanded, for example, by applying heat. This results in the layered composite material 200 being inserted in a form-fitting manner. This is used, for example, in the insulation of stator slot bases from the stator windings (not shown). The layered composite material 200 can also be further protected by surrounding the expanding adhesive layers 17 on their respective outer surfaces with a porous cover layer 18. Reference symbol list 100 Toughener-modified composite material 200 Layered composite material 10 Main matrix 11 Amorphous high-temperature polymer 12 Toughener-modifying additive 13 Beta-polypropylene 14 Beta-polypropylene fiber 15 Beta-polypropylene particles 16 Core layer 17 Expandable adhesive layers 18 Porous top layer

Claims

Toughness-modified composite material (100) comprising a main matrix (10), in particular a semi-crystalline matrix, wherein the main matrix (10) comprises an amorphous high-temperature polymer (11), characterized in that the main matrix (10) is selected from a list comprising: polyethylene naphthalate (PEN), cyclo-olefin copolymer (COC), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), fluoroethylene propylene (FEP), syndiotactic polystyrene (syndiotactic PS) or a combination thereof, wherein at least one toughness-modifying additive (12) is incorporated into the amorphous high-temperature polymer (11), wherein the toughness-modifying additive (12) is beta-polypropylene (13). Toughener-modified composite material (100) according to claim 1, characterized in that the toughener-modifying additive (12) is a beta-polypropylene (13), wherein preferably the beta-polypropylene (13) is incorporated into the amorphous high-temperature polymer (11) as beta-polypropylene fiber (14) and / or beta-polypropylene particles. Tough-modified composite material (100) according to claim 2, characterized in that the beta-polypropylene fibers (14) have a length of 1 nm to 100 mm, preferably 0.1 mm to 35 mm, particularly preferably 1 mm to 20 mm with a diameter of 1 nm to 10 mm, preferably 0.1 mm to 1 mm and / or the beta-polypropylene particles (15) have a diameter of 1 nm to 50 mm, preferably 0.1 mm to 35 mm, particularly preferably 0.1 mm to 2 mm. Tough-modified composite material (100) according to one of the preceding claims, characterized in that the beta-polypropylene (13) is encapsulated by the amorphous high-temperature polymer (11). Toughened-modified composite material (100) according to one of the preceding claims, characterized in that the amorphous high-temperature polymer (11) consists of polyetherimide (PEI), polyphenylene ether (PPE), a polyphenylene ether (PPE) / polystyrene (PS) blend and / or a combination thereof. Toughened-modified composite material (100) according to one of the preceding claims, characterized in that the toughened-modified composite material (100) comprises at least 50 wt.% of the main matrix (10), at least 10 wt.% of the amorphous high-temperature polymer (11) and at least 0.1 wt.% beta-polypropylene (13), preferably at least 64.9 wt.% of the main matrix (10), at least 10 wt.% of the amorphous high-temperature polymer (11) and at least 0.1 wt.% beta-polypropylene (13). Toughened-modified composite material (100) according to claim 6, characterized in that the toughened-modified composite material (100) comprises 50 to 89.9 wt.% of the main matrix (10), 10 to 35 wt.% of the amorphous high-temperature polymer (11) and 0.1 to 15 wt.% beta-polypropylene (13), preferably 64.9 to 89.9 wt.% of the main matrix (10), 10 to 35 wt.% of the amorphous high-temperature polymer (11) and 0.1 to 15 wt.% beta-polypropylene (13). Layer composite material (200) comprising a toughened composite material (100) according to one of claims 1 to 7, characterized in that the toughened composite material (100) is arranged in a core layer (16) and the core layer (16) is arranged between at least two adhesive layers (17) that are expandable, in particular by heat. Layer composite material (200) according to claim 8, characterized in that the at least two expandable adhesive layers (17) are each surrounded by a porous cover layer (18).

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