A pultruded profile having a foamed core and a method of making the same

Abstract

The present application relates to a kind of pultruded profiles with foamed core and its preparation method, belong to wood plastic profile technical field.The profile includes the fiber reinforced frame formed by continuous fiber and first polymer matrix, and the polymer foamed core material filled in its inside, made of second polymer matrix foaming, and the integrated structure of both.This application "high-strength frame + light foamed core" composite configuration, significantly increase cross-sectional moment of inertia at low density, fundamentally improve the bending stiffness and stability of profile, solve the short board of traditional pultruded profiles in large-span transverse bearing insufficient rigidity.The present application is through material and process innovation, light, high-strength, high-rigid, high-efficiency molding is integrated, provides new ideas for expanding the application of composite materials in load-bearing structure field.

Description

Technical Field

[0001] This invention relates to a pultruded profile, and more particularly to a pultruded profile with a foamed core and its preparation method, belonging to the technical field of wood-plastic profiles. Background Technology

[0002] Profiles, as a common engineering structural material, are typically made of metal materials such as aluminum alloys or light steel and are widely used in construction, transportation, machinery and equipment, and interior and exterior decoration. However, due to fluctuations in international raw material market prices and insufficient supply chain stability, the promotion and application of these metal profiles across borders face many constraints.

[0003] To overcome the aforementioned limitations, the industry is gradually shifting towards the development of non-metallic composite profiles. Among them, fiberglass reinforced profiles have attracted attention due to their lightweight, high strength, and corrosion resistance. For example, Chinese patent CN13524837B discloses a reinforced wood-plastic composite profile with fiberglass reinforcement, the structure of which includes a fiberglass core and an outer coating layer. The core is composed of fiber-reinforced material and synthetic resin, while the coating layer is mainly composed of polyolefin resin with a certain proportion of ion-polymerized resin added. This solution uses an extrusion process to achieve the integral molding of the core and coating layer, utilizing the good interfacial compatibility between fiberglass and polyolefin-based wood-plastic composites to improve the bonding strength between the coating layer and the core, while reducing the overall weight, thus improving to some extent the problems of insufficient bonding and excessive weight of traditional wood-plastic composite metal cores. However, this profile is mainly reinforced with short fibers, and the distribution of fibers in the matrix is ​​discrete, which has limited improvement on the overall mechanical properties, and the production process easily generates dust, resulting in poor environmental friendliness.

[0004] To further improve performance, subsequent research introduced pultrusion molding technology. For example, invention patent application CN120840118A provides a production scheme for anti-slip fiberglass pultruded flooring. This production line arranges continuous fibers on a yarn rack, and through yarn threading, glue injection, and curing, forms a continuous fiberglass pultruded core layer. Then, an anti-slip surface layer is composited onto the surface using a co-extrusion die. This method can achieve the directional arrangement of continuous fibers along the length of the profile, significantly improving the longitudinal tensile strength and elastic modulus of the material, making it particularly suitable for load-bearing structures such as flooring. However, when these pultruded profiles are used as transverse load-bearing components such as beams and trusses, especially under large-span conditions, they still suffer from insufficient bending stiffness, easily undergoing bending deformation under load, thus limiting their application in scenarios with larger spans or higher load-bearing requirements. Summary of the Invention

[0005] To address the aforementioned problems, in a first aspect, the present invention provides a pultruded profile with a foamed core.

[0006] The technical solution of the present invention to solve the above problems is as follows:

[0007] A pultruded profile with a foamed core, comprising:

[0008] A fiber-reinforced framework is formed by curing or plasticizing continuous fibers impregnated with a first polymer matrix;

[0009] The polymer foam core material is made from a second polymer matrix through a foaming process.

[0010] The polymer foam core material fills the hollow structure inside the fiber-reinforced frame, forming an integrated structure.

[0011] This invention provides an innovative solution for pultruded profiles with a foamed core and their preparation method. This solution is not a simple combination of existing pultrusion or extrusion processes, but rather a systematic structural solution based on a profound understanding of the stress characteristics of structural profiles, the integration of material functions, and the inherent relationship between composite processes. It aims to solve the bending deformation problem under large-span lateral loads while simultaneously achieving lightweight, high strength, high stiffness, and process-friendly characteristics. Its fundamental goal is to significantly improve the lateral bending stiffness and overall structural stability of the profile by integrating the core foaming with the frame, while maintaining the axial strength of the continuous fiber reinforcement material. This overcomes the mechanical limitations of traditional hollow pultruded profiles when used as large-span components such as beams and trusses.

[0012] Background technology has clearly pointed out that although continuous fiber reinforced profiles prepared by pultrusion process can significantly improve the axial (longitudinal) strength and modulus of the material through the directional reinforcement of fibers, they still have problems such as insufficient bending stiffness and easy bending deformation when subjected to transverse bending loads, especially as large-span components.

[0013] The pultruded profile with a foamed core of the present invention is a systematic solution to the aforementioned mechanical performance and process bottlenecks. It transforms the structural design of the profile from a "homogeneous or simple composite" approach to a composite structural concept of "rigid-flexible and gradient composite".

[0014] Firstly, the core-frame synergistic reinforcement structure fundamentally improves bending stiffness. This invention creatively designs an integrated composite structure of "fiber-reinforced frame + polymer foam core material." The technical logic lies in optimizing the functional zoning of the profile cross-section: the outer fiber-reinforced frame, composed of continuous fibers impregnated with resin and cured, primarily bears tensile and compressive stresses; the inner polymer foam core material fills its internal cavity, providing continuous support. The direct technical effect is that, with almost no or minimal increase in self-weight, the continuous support of the thin-walled fiber frame by the foam core material significantly increases the effective moment of inertia of the profile cross-section. When subjected to lateral bending loads, the foam core material effectively suppresses local buckling instability of the fiber-reinforced frame, allowing the frame material to more fully utilize its high-strength characteristics, thereby fundamentally and significantly improving the overall bending stiffness and lateral deformation resistance of the profile, making it particularly suitable for lateral load-bearing components requiring large spans and high stiffness.

[0015] Secondly, the efficient integration of continuous-intermittent processes and integrated molding is achieved. The core of the preparation method of this invention lies in the ingenious integration and synchronization of polymer foaming extrusion and fiber pultrusion processes in space and time. The technical logic is to use a continuously prepared polymer foam core material as a moving mandrel, continuously passing through the central channel of the pultrusion-co-extrusion die; simultaneously, within the die, continuous fibers surround the foam core material, are laid up, compacted, and cured, thereby forming an integrated core-frame structure. The ingenuity of this "synchronous pultrusion molding" design lies in: 1) It achieves online, synchronous composite of the foam core and the reinforcing frame, eliminating the interface weakening problem of secondary bonding and ensuring a tight bond and integrity between the core and frame; 2) Using a flexible, compressible foam or a rigid foam as the inner core provides uniform support pressure to the frame during molding, which is beneficial to improving the molding quality and density of the frame; 3) This process is continuous and efficient, suitable for large-scale production, and effectively integrates the advantages of both extrusion and pultrusion processes.

[0016] Thirdly, the invention offers a wide range of options for the multifunctional expansion and performance designability of the material system. In terms of material selection, it provides a broad selection space for fiber reinforcement phases (continuous glass fiber, carbon fiber, etc.), matrix resins (unsaturated polyester, epoxy resin, etc.), and foamed core materials (polyurethane, polyolefin elastomers, etc.). The technical logic lies in the fact that customized design of profile performance can be achieved through different material combinations. For example, using a carbon fiber reinforced frame and a high-performance engineering plastic foam core can yield lightweight structural components with extremely high specific strength and specific stiffness; using corrosion-resistant resin and a closed-cell foam core can produce special profiles suitable for high-humidity and corrosive environments; and using PVC resin and glass fiber can yield cost-effective general-purpose profiles. Furthermore, optional functional surface layers further expand its functionality, such as imparting surface properties like wear resistance, weather resistance, decoration, or special tactile qualities. This highly designable material system allows the profile to flexibly adapt to the diverse needs of different fields such as construction, transportation, and new energy equipment.

[0017] As a preferred embodiment of the above technical solution, the continuous fiber is selected from at least one of glass fiber, aramid fiber, carbon fiber, silicon carbide fiber, basalt fiber, and plant fiber.

[0018] The technical solutions described above provide a wide range of reinforcing material options, enabling profiles to be customized according to requirements for strength, modulus, weight, cost, and special properties (such as high temperature resistance, wave transmission, and environmental friendliness). For example, carbon fiber can achieve the highest specific strength and specific modulus; basalt or plant fibers offer greater cost and environmental advantages.

[0019] As a preferred embodiment of the above technical solution, the first polymer is selected from at least one of polyolefin resin, ion-crosslinked resin of ethylene-(meth)acrylic acid copolymer, polyvinyl chloride resin, acrylonitrile-styrene-acrylate copolymer, acrylonitrile-butadiene-styrene copolymer, polyurethane, phenolic resin, epoxy resin, unsaturated polyester, and polymethyl methacrylate.

[0020] The wide selection of matrix resins allows for precise control over the mechanical properties, corrosion resistance, weather resistance, molding processability (curing temperature and speed), and interfacial compatibility with the core material of fiber-reinforced frames, in order to meet the comprehensive requirements of profile frames for different application environments.

[0021] As a preferred embodiment of the above technical solution, the second polymer is selected from at least one of polyethylene, polyvinyl chloride, polypropylene, polyvinyl acetate, polystyrene, polyurethane, polyterephthalic acid diol ester, polymethacrylamide, and polyolefin elastomer.

[0022] The diverse selection of foam core materials allows for optimization of core density, compressive strength, creep resistance, cushioning energy absorption properties, temperature resistance, and cost. For example, rigid polyurethane (PUR) or polymethacrylamide (PMI) foams can be used to obtain structural core materials with high specific strength; while polyolefin elastomer (POE) foams can provide excellent flexibility and impact resistance.

[0023] As a preferred embodiment of the above technical solution, the profile further includes a functional surface layer disposed on the outer surface of the fiber-reinforced frame.

[0024] By co-extruding or subsequently coating functional surface layers (such as wear-resistant layers, weather-resistant layers, decorative layers, anti-slip layers, tactile layers, etc.), additional surface properties can be given to the profiles without affecting the main load-bearing structure, expanding their application scenarios, reducing the need for subsequent secondary processing, and increasing the added value of the products.

[0025] Secondly, the present invention provides a method for preparing the above-mentioned pultruded profile with a foamed core.

[0026] The technical solution is as follows:

[0027] A method for preparing a pultruded profile with a foamed core includes the following steps:

[0028] S1. Core material molding: The foamable second polymer material is plasticized by an extruder and molded by a foaming mold that is matched with a pultrusion-co-extrusion mold to obtain a continuous length of polymer foam core material.

[0029] S2, Reinforcing Layer Covering: The polymer foamed core material is used as a moving mandrel and guided to continuously pass through the core material channel of the pultrusion-co-extrusion die; at the same time, continuous fibers are introduced into the reinforcing layer cavity of the pultrusion-co-extrusion die and arranged to surround the core material channel;

[0030] S3. Synchronous pultrusion molding: Under the action of the traction device, the polymer foam core material and the continuous fibers impregnated with the first polymer matrix are synchronously passed through the pultrusion-co-extrusion die; in the pultrusion-co-extrusion die, the first polymer matrix is ​​cured or plasticized to form a continuous fiber reinforced frame that completely covers the polymer foam core material inside.

[0031] S4. Post-processing: The formed composite profile is pulled out of the mold, cooled and shaped, and then cut to a fixed length to obtain the pultruded profile with foam core.

[0032] As a preferred embodiment of the above technical solution, in step S2, the core material channel and the reinforcing layer cavity of the pultrusion-co-extrusion die are coaxially sleeved, so that the continuous fiber reinforcing frame uniformly covers the polymer foam core material.

[0033] The coaxial sleeve structure ensures the central positioning of the foamed core material in the fiber-reinforced frame, so that the reinforcing material is evenly distributed and symmetrically bears the load, avoiding anisotropy of mechanical properties or weak links caused by eccentricity, and ensuring the consistency and reliability of the profile structure.

[0034] As a preferred embodiment of the above technical solution, in step S2, the continuous fiber is drawn out from the yarn frame, guided by the yarn guide plate, first passes through the injection mold containing the first polymer matrix, and then exits from the injection mold to form a continuous fiber impregnated with the first polymer matrix.

[0035] By adopting the method of "pre-impregnation with resin and then insertion into the mold", the continuous fibers can be fully and uniformly impregnated with resin before entering the cavity of the reinforcing layer. This is beneficial for the resin to completely encapsulate the fiber bundle, reduce dry yarn and pores, thereby maximizing the reinforcing efficiency of the fibers and improving the mechanical properties of the composite frame.

[0036] As another preferred embodiment of the above technical solution, in step S2, the continuous fiber is drawn out from the yarn frame, guided by the yarn guide plate, and directly fed into the reinforcing layer cavity of the pultrusion-co-extrusion die; the first polymer matrix is ​​injected into the reinforcing layer cavity of the pultrusion-co-extrusion die.

[0037] The "in-mold injection" method results in a shorter process path and potentially a more compact equipment layout. Resin impregnates the fibers under mold pressure, making it suitable for certain resin systems or applications requiring simplified processes, thus offering process flexibility.

[0038] Thirdly, the present invention provides another method for preparing the above-mentioned pultruded profile with a foamed core.

[0039] The technical solution is as follows:

[0040] A method for preparing a pultruded profile with a foamed core includes the following steps:

[0041] S1. Core material molding: The foamable second polymer material is plasticized by an extruder and molded by a foaming mold that is matched with a pultrusion-co-extrusion mold to obtain a continuous length of polymer foam core material.

[0042] S2, Reinforcing Layer Covering: The polymer foam core material is used as a moving mandrel and guided to continuously pass through the core material channel of the pultrusion-co-extrusion die; at the same time, continuous fibers are introduced into the reinforcing layer cavity of the pultrusion-co-extrusion die and arranged around the core material channel to form a fiber-reinforced frame.

[0043] S3, Functional layer co-extrusion coating: At the exit end of the pultrusion-co-extrusion die, the third polymer material used to form the functional surface layer is melt-coated onto the outer surface of the fiber-reinforced frame through an annular extrusion port.

[0044] S4. Synchronous Traction and Shaping: Under the action of the traction device, the polymer foam core material, fiber reinforced frame and functional surface layer arranged from the inside to the outside are passed through the shaping device to solidify or cool and shape the composite profile, forming an integrated three-layer composite profile.

[0045] S5. Post-processing: The formed composite profile is pulled out of the shaping device and then cut to a fixed length after subsequent cooling.

[0046] In summary, the present invention has the following beneficial effects:

[0047] 1. Breakthrough optimization of mechanical properties, especially significantly improved bending stiffness and stability: Through the composite structure of "high-strength fiber reinforced frame + lightweight foam core", the moment of inertia of the section is greatly increased at low density, which fundamentally solves the problem of insufficient bending stiffness of traditional solid or thin-walled pultruded profiles, enabling them to be competent for transverse structural applications with large span and high load, and significantly broadening the application range of pultruded profiles.

[0048] 2. Excellent retention and enhancement of lightweight and high strength characteristics: The introduction of foamed core material significantly increases stiffness, while having a very low density, which has little impact on the overall weight increase of the profile. It perfectly inherits the core advantages of composite materials of "lightweight and high strength" and further amplifies its "high stiffness" characteristics.

[0049] 3. Synergistic improvement of process integration and interface performance: The simultaneous process of foaming molding and pultrusion molding realizes the online composite of core material manufacturing and frame forming, with high interfacial bonding strength; at the same time, the process is continuous and efficient, combining production efficiency and product quality.

[0050] 4. Multifunctional integration and high designability: The diversity of material selection and the optional configuration of functional surfaces enable the profile to be precisely customized in terms of performance and function according to the final use scenario (such as load-bearing structure, corrosion-resistant environment, appearance decoration requirements, etc.), realizing an integrated solution from structural load-bearing to surface protection, resulting in high product added value;

[0051] 5. Excellent balance between overall cost and performance: Compared with pure high-performance fiber reinforcement or metal structure, this solution improves key mechanical properties by filling the interior with low-cost polymer foam, which achieves significant optimization of overall structural efficiency while controlling raw material costs, and has extremely high cost performance and market competitiveness.

[0052] 6. In summary, the pultruded profile with a foamed core and its preparation method of the present invention, starting from the inherent characteristics of structural mechanics, successfully integrates the advantages of lightweight, high strength, high rigidity, and efficient molding through innovative material configuration and process integration. This solution not only effectively solves the key shortcomings of existing pultruded profiles in lateral load-bearing applications, but also provides new design ideas and process paths for the development of high-performance composite profiles. It has important technical value and engineering significance for promoting the wider application of composite materials in large-scale structural fields such as buildings, bridges, transportation vehicles, and wind power. Attached Figure Description

[0053] Figure 1 This is a schematic diagram of the product structure according to Embodiment 1 of the present invention;

[0054] Figure 2 This is a schematic diagram of the pultrusion-co-extrusion die structure according to Embodiment 1 of the present invention;

[0055] Figure 3 This is a cross-sectional view of mold plate D according to Embodiment 1 of the present invention;

[0056] Figure 4 This is a schematic diagram of the product structure according to Embodiment 2 of the present invention;

[0057] Figure 5 This is a schematic diagram of the pultrusion-co-extrusion die structure according to Embodiment 2 of the present invention;

[0058] In the diagram, the component names represented by each number are as follows:

[0059] 1-Polymer foam core material;

[0060] 2-Fiber reinforced framework;

[0061] 3-Functional surface layer;

[0062] 21-Continuous fiber;

[0063] 10-Core material channel of pultrusion-co-extrusion die;

[0064] 20-Reinforcing layer cavity of pultrusion-co-extrusion die;

[0065] 22-Guide hole;

[0066] 30 - Annular extrusion port. Detailed Implementation

[0067] The present invention will be further explained and described below with reference to the accompanying drawings.

[0068] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. Any changes made by those skilled in the art after reading this specification, as long as they fall within the scope of the claims, will be protected by patent law.

[0069] Example 1

[0070] This embodiment provides a pultruded profile with a foamed core, the structure of which is as follows: Figure 1 As shown. The profile has a square, rounded-corner cross-section and consists of two parts from the inside out: a polymer foam core material 1 (rigid PVC foam core material) and a fiber-reinforced frame 2 (wherein the fiber is continuous fiber 21, specifically glass fiber reinforced polyurethane). The fiber-reinforced frame 2 holds the rigid PVC foam core material (density approximately 500~600 kg / m³) together with the fiber-reinforced frame 2. 3 The fiber-reinforced frame 2 is a dense exoskeleton with a square, rounded corner shape and a corresponding internal cavity shape, formed by curing and molding continuous glass fiber reinforced polyurethane resin.

[0071] The above-mentioned method for preparing pultruded profiles with foamed cores employs, as follows: Figure 2 The mold structure shown below has the following specific steps and key technical points:

[0072] Step S1, Core Material Forming: PVC dry mix (a foamable second polymer material) containing a foaming agent (such as AC foaming agent) is added to a conical twin-screw extruder and plasticized and melted at 160~180℃; the uniformly plasticized melt is conveyed to a foaming mold that is matched with a pultrusion-co-extrusion mold, foamed at a precisely controlled temperature, and shaped through a die with a square rounded corner section to form a continuous and uniform rigid PVC foam core material;

[0073] Step S2, Reinforcing Layer Coating Preparation: Multiple bundles of continuous untwisted glass fiber rovings are drawn from the yarn rack, guided by the yarn guide plate, and then further passed through the precisely arranged guide holes 22 on the mold plate D, such as... Figure 3 As shown, these guide holes 22 are uniformly arranged around the core material channel 10 in the circumferential direction; after being guided by this, the fiber bundle is uniformly and orderly introduced into the reinforcing layer cavity 20 of the pultrusion-co-extrusion die; at the same time, the continuous PVC foamed core material formed from the foaming die outlet extends directly into and precisely aligns with the core material channel 10 of the pultrusion-co-extrusion die at its outlet end, and is continuously pulled through the channel as a "moving mandrel".

[0074] Step S3, Synchronous Pultrusion Plasticizing: Under the action of the traction device, the PVC foam core material and the continuous glass fibers arranged around it pass through the pultrusion-co-extrusion mold simultaneously; during this process, the prepared polyurethane matrix material (i.e., the first polymer, which is a castable polyurethane resin) is injected under high pressure into the glass fiber-filled reinforcing layer cavity 20 through the injection port set on the side wall of the reinforcing layer cavity 20; the material is completely cured in the mold heating zone (temperature controlled at 170~190℃), and fully impregnates and wraps the fiber bundles under the mold pressure, while tightly bonding with the surface of the internally moving PVC foam core material; finally, it is compacted and shaped by a die with a square rounded corner cross section to form a plasticized glass fiber reinforced frame that completely covers the foam core material 1.

[0075] Step S4, Post-processing: The formed integrated composite profile is pulled out of the mold, cooled and shaped, and then cut to a fixed length to obtain a pultruded profile with a square cross-section and rounded corners.

[0076] Example 2

[0077] This embodiment provides another pultruded profile with a foamed core. Based on the structure of Embodiment 1, a uniformly thick (approximately 2 mm) ASA functional surface layer 3 is co-extruded onto the outer surface of the glass fiber reinforced frame. Its structure is as follows: Figure 4 As shown. The profile also has a square cross-section with rounded corners, and has an internal polymer foam core 1 (PVC rigid foam core) and a fiber-reinforced frame 2. The outer ASA functional surface layer mainly gives the profile excellent UV resistance, weather resistance and decorative appearance, making it suitable for outdoor environments.

[0078] The above-mentioned method for preparing profiles is an extension of the process in Example 1, and the mold structure involved is as follows: Figure 5 As shown, the main steps include:

[0079] Step S1, Core Material Forming: This step is the same as in Example 1; a continuous PVC rigid foam core material with a square cross-section and rounded corners is prepared.

[0080] Step S2, Reinforcing layer preparation: This step is similar to Example 1; continuous glass fiber is introduced into the reinforcing layer cavity 20 of the pultrusion-co-extrusion die through the guide hole 22 of the yarn guide plate and the mold plate D, and PVC foam core material passes through the core material channel 10; polyurethane matrix material is injected into the reinforcing layer cavity 20 under high pressure through the injection port.

[0081] Step S3, Functional Layer Co-extrusion Coating: An annular extrusion port 30 with a square rounded corner slit is integrated at the outlet end of the reinforcing layer cavity of the pultrusion-co-extrusion die; ASA resin (third polymer material) is plasticized at 220~240℃ through an independent single screw extruder, and then accurately metered and delivered to the annular extrusion port 30; the ASA melt forms a uniform annular melt flow that matches the shape of the product, and directly coats the outer surface of the glass fiber reinforced frame, which is in a semi-plasticized state and has just been formed and discharged from the reinforcing layer cavity 20, at the die outlet;

[0082] Step S4, Synchronous Traction Cooling and Shaping: Under the action of the traction device, the composite structure consisting of PVC foam core material, glass fiber reinforced frame and outer ASA melt layer is synchronously passed through a shaping and cooling mold with a square rounded corner cross section; here, the outer ASA melt is cooled, compacted and firmly bonded to the frame surface to form a uniform thickness (about 2mm) ASA functional surface layer 3.

[0083] Step S5, Post-processing: The shaped integrated three-layer composite profile is pulled out, and after sufficient cooling, it is cut to a fixed length to obtain the product.

[0084] Summary of mold structure and related technical points:

[0085] Mold Integration: The mold structures in Examples 1 and 2 are both integrated units of a foaming mold and a pultrusion-co-extrusion mold. The molding outlet of the foaming mold extends directly into and is precisely aligned with the core material channel 10 of the pultrusion-co-extrusion mold, realizing the "online" continuous preparation and direct delivery of the foamed core material, ensuring process stability and core material positioning accuracy.

[0086] Fiber guidance: such as Figure 3 (Cross-sectional view of mold plate D) As shown, continuous glass fibers must pass through guide holes 22 that are uniformly arranged around the core material channel 10 on the mold plate in the circumferential direction before they can enter the reinforcing layer cavity 20. This design ensures the uniform distribution of fibers around the core material, which is the key to obtaining a reinforcing frame with balanced mechanical properties.

[0087] Resin Injection: In Examples 1 and 2, the matrix resin (first polymer, non-foamed PVC) of the reinforcing frame is injected into the mold using an in-mold injection method. The resin is injected under high pressure through the injection port located on the side wall of the reinforcing layer cavity 20, and the impregnation of the fibers is completed inside the mold. This method has a short process path, makes it easy to control the resin content, and avoids the pollution and volatilization problems that may be caused by open impregnation. In a more optimized method, there are two injection ports, which are symmetrically arranged.

[0088] Functional layer co-extrusion: Die structure of Example 2 ( Figure 5Based on the mold in Example 1, an annular extrusion port 30 is integrated at the exit end for co-extruding the functional surface layer; this structure realizes the online, one-time molding composite of the functional surface layer and the reinforcing frame, with a strong interface bond and high production efficiency.

[0089] The above description is only a preferred embodiment of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A pultruded profile with a foamed core, comprising a fiber-reinforced frame (2) formed by curing or plasticizing continuous fibers (21) impregnated with a first polymer matrix; characterized in that: The profile also includes a polymer foam core material (1), which is made from a second polymer matrix through a foaming process; the polymer foam core material fills the hollow structure inside the fiber-reinforced frame (2) and forms an integrated structure.

2. The pultruded profile with a foamed core according to claim 1, characterized in that: The continuous fiber is selected from at least one of glass fiber, aramid fiber, carbon fiber, silicon carbide fiber, basalt fiber, and plant fiber.

3. The pultruded profile with a foamed core according to claim 1, characterized in that: The first polymer is selected from at least one of polyolefin resin, polyvinyl chloride resin, ion-crosslinked resin of ethylene-(meth)acrylic acid copolymer, acrylonitrile-styrene-acrylate copolymer, acrylonitrile-butadiene-styrene copolymer, polyurethane, phenolic resin, epoxy resin, unsaturated polyester, and polymethyl methacrylate.

4. The pultruded profile with a foamed core according to claim 1, characterized in that: The second polymer is selected from at least one of polyethylene, polyvinyl chloride, polypropylene, polyvinyl acetate, polystyrene, polyurethane, polyterephthalic acid diol ester, polymethacrylamide, and polyolefin elastomer.

5. A pultruded profile with a foamed core according to claim 1, characterized in that: The profile also includes a functional surface layer (3) disposed on the outer surface of the fiber-reinforced frame.

6. A method for preparing a pultruded profile with a foamed core according to any one of claims 1 to 4, comprising the following steps: S1, Core material forming: The foamable second polymer material is plasticized by an extruder and formed by a foaming mold that is matched with a pultrusion-co-extrusion mold to obtain a continuous length of polymer foam core material (1). S2, Reinforcing layer coating: The polymer foam core material (1) is used as a moving mandrel and guided to continuously pass through the core material channel (10) of the pultrusion-co-extrusion die; at the same time, continuous fibers (21) are introduced into the reinforcing layer cavity (20) of the pultrusion-co-extrusion die and the continuous fibers (21) are arranged around the core material channel (10); S3. Synchronous pultrusion molding: Under the action of the traction device, the polymer foam core material (1) and the continuous fiber (21) impregnated with the first polymer matrix are synchronously passed through the pultrusion-co-extrusion mold; in the pultrusion-co-extrusion mold, the first polymer matrix is ​​cured or plasticized to form a continuous fiber reinforced frame (2) that completely covers the polymer foam core material (1) inside. S4. Post-processing: The formed composite profile is pulled out of the mold, cooled and shaped, and then cut to a fixed length to obtain the pultruded profile with foam core.

7. The method for preparing a pultruded profile with a foamed core according to claim 6, characterized in that: In step S2, the core material channel and the reinforcing layer cavity of the pultrusion-co-extrusion die are coaxially fitted, so that the continuous fiber reinforcing frame uniformly covers the polymer foam core material.

8. The method for preparing a pultruded profile with a foamed core according to claim 6, characterized in that: In step S2, the continuous fiber is drawn out from the yarn frame, guided by the yarn guide plate, first passes through the injection mold containing the first polymer matrix, and then exits from the injection mold to form a continuous fiber impregnated with the first polymer matrix.

9. A method for preparing a pultruded profile with a foamed core according to claim 6, characterized in that: In step S2, the continuous fiber is drawn out from the yarn frame, guided by the yarn guide plate, and directly fed into the reinforcing layer cavity of the pultrusion-coextrusion die; the first polymer matrix is ​​injected into the reinforcing layer cavity of the pultrusion-coextrusion die.

10. A method for preparing a pultruded profile with a foamed core according to claim 5, comprising the following steps: S1, Core material forming: The foamable second polymer material is plasticized by an extruder and formed by a foaming mold that is matched with a pultrusion-co-extrusion mold to obtain a continuous length of polymer foam core material (1). S2, Reinforcing layer coating: The polymer foam core material (1) is used as a moving mandrel and guided to continuously pass through the core material channel (10) of the pultrusion-co-extrusion die; at the same time, continuous fibers (21) are introduced into the reinforcing layer cavity (20) of the pultrusion-co-extrusion die and the continuous fibers (21) are arranged around the core material channel (10) to form a fiber-reinforced frame (2). S3, Functional layer co-extrusion coating: At the exit end of the pultrusion-co-extrusion die, the third polymer material used to form the functional surface layer (3) is melt-coated onto the outer surface of the fiber-reinforced frame (2) through an annular extrusion port (30); S4. Synchronous Traction and Shaping: Under the action of the traction device, the polymer foam core material, fiber reinforced frame and functional surface layer arranged from the inside to the outside are passed through the shaping device to solidify or cool and shape the composite profile, forming an integrated three-layer composite profile. S5. Post-processing: The formed composite profile is pulled out of the shaping device and then cut to a fixed length after subsequent cooling.

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