Manufacturing method of low-voltage connector sheath and loudspeaker sheath

Abstract

The invention relates to the technical field of electronic connector manufacturing, in particular to a manufacturing method of a low-voltage connector sheath and a loudspeaker sheath, and has the advantages that formation of micropores and stress cracks at the joint of an upper cover and a body is effectively avoided, and the insulation reliability is improved; the uniform dispersion of the flame retardant is ensured, and the stability of the flame retardant property is enhanced; and the mechanical strength and the fatigue resistance of the overturning upper cover area are improved. Through layered formula design of the base layer and the reinforcing layer and accurate injection molding process control, the problems of micropore formation at the joint of the upper cover and the body, non-uniform dispersion of a flame retardant and material fatigue and aging are effectively solved, the formation of micropores and stress cracks at the joint of the upper cover and the body is effectively avoided, and the insulation reliability is improved; the uniform dispersion of the flame retardant is ensured, and the stability of the flame retardant property is enhanced; the mechanical strength and the fatigue resistance of the overturning upper cover area are improved; the interface compatibility of the material is improved, and the stability of the insulation resistor is guaranteed.

Description

Technical Field

[0001] This application relates to the field of electronic connector manufacturing technology, and more specifically, to a method for manufacturing a low-voltage connector sheath and a speaker sheath. Background Technology

[0002] In the production practice of low-voltage connector sheaths, existing processes have a series of defects that urgently need to be addressed. In the one-piece molded structure, micropores or stress cracks are easily formed at the junction of the top cover and the body. Such defects can significantly shorten the creepage distance and increase the risk of insulation breakdown in humid environments or dust accumulation conditions, and may even cause insulation failure problems even in low-voltage operating scenarios.

[0003] Meanwhile, traditional injection molding processes struggle to achieve uniform dispersion of flame retardants, leading to insufficient concentrations in certain areas. This can result in localized combustion under high temperatures or short circuits, causing unstable flame retardant performance. Furthermore, repeated opening and closing of the flip-top cover can cause fatigue aging of the material, resulting in microcracks on the surface and compromising the integrity of the insulation barrier. The lack of flexibility in conventional material formulations further exacerbates the risk of cover breakage. Poor compatibility between the plastic substrate and the flame retardant results in interface defects within the molded material, affecting the stability of insulation resistance and the continuity of the flame retardant effect.

[0004] To address the aforementioned issues, existing technologies urgently need improvement. Summary of the Invention

[0005] (a) Technical problems to be solved To address the aforementioned issues, this invention proposes a manufacturing method for a low-voltage connector sheath and a speaker sheath. These methods effectively prevent the formation of micropores and stress cracks at the junction of the top cover and the body, thereby improving insulation reliability; ensure uniform dispersion of the flame retardant, enhancing the stability of flame retardant performance; improve the mechanical strength and fatigue resistance of the flip-top cover area; and improve material interface compatibility, ensuring the stability of insulation resistance.

[0006] (II) Technical Solution This application provides a method for manufacturing a low-voltage connector sheath, the technical solution of which is as follows: The sheath is made by injection molding a base layer and a reinforcing layer in one piece. The base layer formulation, by weight percentage, includes: PA6660-65%, halogen-free flame retardant system 25-30%, toughening agent 5-7%, compatibilizer 1-3%, and auxiliary additives 1-3%; The reinforcing layer formulation, by weight percentage, includes: PA6650-60%, halogen-free flame retardant system 30-40%, epoxy resin 2-4%, curing agent 0.5-1.5%, and auxiliary additives 5-7%; The halogen-free flame retardant system includes red phosphorus masterbatch and MCA; The manufacturing method includes the following steps: S100. After mixing the components of the base layer according to the specified ratio, dry at 80-90℃ for 4-5 hours, controlling the moisture content to ≤0.1%; after mixing the components of the reinforcement layer according to the specified ratio, dry at 85-95℃ for 5-6 hours, controlling the moisture content to ≤0.08%. S200: A mold with at least two cavities is used, the first cavity corresponding to the base layer and the second cavity corresponding to the reinforcement layer; Preheat the mold to a temperature of 60-70℃ for the first cavity, 80-90℃ for the second cavity, and 240-250℃ for the hot runner. S300. Inject the pretreated base layer material into the first cavity. The injection parameters are: injection pressure 80-100MPa, injection speed 30-40mm / s, holding pressure 60-70MPa, holding time 15-20s, and after cooling for 25-30s, transfer the formed base layer workpiece to the second cavity. S400. Inject the pretreated reinforcing layer material into the second cavity to cover the key areas of the base layer. The injection parameters are: injection pressure 90-110MPa, injection speed 25-35mm / s, holding pressure 70-80MPa, holding time 20-25s. S500: Keep the mold closed, raise the temperature of the second cavity to 180-190℃, hold for 5-8 minutes to trigger the cross-linking reaction of the epoxy resin; S600: Demold after cooling the mold to 60-70℃.

[0007] Furthermore, this application also proposes that the halogen-free flame retardant system in the base layer is composed of red phosphorus masterbatch and MCA, wherein the red phosphorus masterbatch accounts for 15-17% of the total mass of the base layer and the MCA accounts for 10-14% of the total mass of the base layer; The halogen-free flame retardant system in the reinforcing layer consists of red phosphorus masterbatch, MCA and nano magnesium hydroxide, wherein the red phosphorus masterbatch accounts for 18-22% of the total mass of the reinforcing layer, MCA accounts for 8-12% of the total mass of the reinforcing layer, and nano magnesium hydroxide accounts for 4-6% of the total mass of the reinforcing layer.

[0008] Furthermore, this application also proposes that the auxiliary additives in the reinforcing layer include compatibilizer PP-g-MAH, antioxidant 1010, lubricant EBS, and nano-montmorillonite, wherein PP-g-MAH accounts for 1-3% of the total mass of the reinforcing layer, antioxidant 1010 accounts for 0.4-0.6%, lubricant EBS accounts for 0.4-0.6%, and nano-montmorillonite accounts for 2-4%.

[0009] Furthermore, this application also proposes that, in step S300, the barrel temperature is controlled in segments as follows: 230-240℃ for the feeding segment, 245-255℃ for the compression segment, and 255-260℃ for the nozzle segment; In step S400, the barrel temperature is controlled in segments as follows: feeding section 240-250℃, compression section 255-265℃, and nozzle section 265-270℃.

[0010] Furthermore, this application also proposes that step S100 further includes mixing the components by stirring them for 10-20 minutes using a high-speed mixer with a rotation speed of 1800-2200 r / min.

[0011] Furthermore, this application also proposes that step S500 further includes ring-opening polymerization of the epoxy resin in the reinforcing layer formulation at 180-190°C under the catalysis of the curing agent dicyandiamide.

[0012] Furthermore, this application also proposes that, after step S600, a step S700 is included: the product is subjected to constant temperature treatment in a hot air oven at 70-90°C for 1-3 hours.

[0013] Furthermore, this application also proposes that the sheath is integrally formed by two-color injection molding of the base layer and the reinforcing layer.

[0014] Furthermore, this application also proposes that the horn cover is an integral structure made by the above manufacturing method, which includes an upper cover connected to the body through a flip structure, and a reinforcing layer bonded to the base layer through in-mold cross-linking is covered at the joint between the upper cover and the body, the inner wall of the pin contact area and the bending area of ​​the upper cover.

[0015] (III) Beneficial Effects Compared with the prior art, the beneficial effects of the present invention are as follows: This invention effectively solves the problems of micropore formation, uneven flame retardant dispersion, and material fatigue aging at the junction of the top cover and the body by using a layered formulation design of the base layer and the reinforcing layer and precise injection molding process control. It effectively avoids the formation of micropores and stress cracks at the junction of the top cover and the body, thus improving insulation reliability; ensures uniform dispersion of the flame retardant, thus enhancing the stability of flame retardant performance; improves the mechanical strength and fatigue resistance of the flip-top cover area; and improves material interface compatibility, thus ensuring the stability of insulation resistance. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 A schematic diagram of the manufacturing process for a low-voltage connector sheath; Figure 2 This is a three-dimensional structural diagram of the speaker housing.

[0018] 10. Main body; 20. Top cover. Detailed Implementation

[0019] Compared to the embodiments shown in the accompanying drawings, feasible embodiments within the scope of this disclosure may have fewer components, other components not shown in the drawings, different components, components arranged differently, or components with different connections, etc. Furthermore, two or more components in the drawings may be implemented in a single component, or a single component shown in the drawings may be implemented as multiple separate components.

[0020] Unless otherwise defined, the technical or scientific terms used herein should be understood in their ordinary sense by one of ordinary skill in the art to which this invention pertains. The terms “first,” “second,” and similar terms used in this patent application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, “an” or “a” and similar terms do not necessarily indicate a quantity limitation. Terms such as “comprising,” “including,” or “having” mean that the element or object preceding the word encompasses the element or object listed following the word and its equivalents, without excluding other elements or objects. Terms such as “connected” or “connected” are not limited to the physical or mechanical connection or connection shown in the drawings, but can include equivalent connections or connections, whether direct or indirect. Terms such as “upper,” “lower,” “left,” “right,” “horizontal,” and “vertical” are used only to indicate relative positional relationships, which may change accordingly when the absolute position of the described object changes.

[0021] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] This application provides a method for manufacturing a low-voltage connector sheath. The sheath is integrally formed by injection molding a base layer and a reinforcing layer in sequence. The formula of the base layer includes, by weight percentage: PA6660-65%, halogen-free flame retardant system 25-30%, toughening agent 5-7%, compatibilizer 1-3%, and auxiliary additives 1-3%. The reinforcing layer formulation, by weight percentage, includes: PA6650-60%, halogen-free flame retardant system 30-40%, epoxy resin 2-4%, curing agent 0.5-1.5%, and auxiliary additives 5-7%; The halogen-free flame retardant system includes red phosphorus masterbatch and MCA; The manufacturing method includes the following steps: S100. After mixing the components of the base layer according to the specified ratio, dry at 80-90℃ for 4-5 hours, controlling the moisture content to ≤0.1%; after mixing the components of the reinforcement layer according to the specified ratio, dry at 85-95℃ for 5-6 hours, controlling the moisture content to ≤0.08%. S200: Use a mold with at least two cavities, the first cavity corresponding to the base layer and the second cavity corresponding to the reinforcement layer; preheat the mold to make the temperature of the first cavity 60-70℃, the temperature of the second cavity 80-90℃, and the temperature of the hot runner 240-250℃; S300. Inject the pretreated base layer material into the first cavity. The injection parameters are: injection pressure 80-100MPa, injection speed 30-40mm / s, holding pressure 60-70MPa, holding time 15-20s, and after cooling for 25-30s, transfer the formed base layer workpiece to the second cavity. S400. Inject the pretreated reinforcing layer material into the second cavity to cover the key areas of the base layer. The injection parameters are: injection pressure 90-110MPa, injection speed 25-35mm / s, holding pressure 70-80MPa, holding time 20-25s. S500: Keep the mold closed, raise the temperature of the second cavity to 180-190℃, hold for 5-8 minutes to trigger the epoxy resin crosslinking reaction; S600: Demold after cooling the mold to 60-70℃.

[0023] In practical applications, the halogen-free flame-retardant system in the base layer can be understood as a composite system composed of multiple flame-retardant components. Its main function is to achieve flame-retardant effects through the synergistic effect of different flame-retardant mechanisms. For example, a combination of melamine phosphate and expanded graphite, or a mixture of aluminum hydroxide and zinc borate, can be used as alternatives. The purpose is to form a dense char layer to isolate oxygen and heat during material combustion. Furthermore, the epoxy resin in the reinforcing layer can be selected from bisphenol A type epoxy resin or aliphatic epoxy resin. These materials can undergo cross-linking reactions under the action of a curing agent, thereby improving the mechanical properties and interfacial bonding ability of the material. As a preferred embodiment, the curing agent can be an amine curing agent or anhydride curing agent, which can adjust the reaction rate according to the process temperature requirements to ensure the controllability of the cross-linking reaction.

[0024] Specifically, the drying process in step S100 can be achieved using a vacuum drying oven or a forced-air drying oven. Its purpose is to remove moisture from the raw materials and prevent moisture from affecting subsequent processing. Furthermore, the injection molding parameters in steps S300 and S400 can be adjusted appropriately based on the specific performance of the equipment; for example, the molding quality can be optimized by changing the injection speed or holding pressure.

[0025] The innovation of this application lies in solving the interface defect problem caused by poor material compatibility in the traditional low-voltage connector sheath manufacturing process by combining layered structural design with material formulation optimization. Furthermore, by introducing an epoxy resin cross-linking reaction into the reinforcing layer, the mechanical strength and fatigue resistance of key areas are improved, while avoiding the interface peeling phenomenon commonly found in traditional layered molding processes.

[0026] Furthermore, the sequential injection molding method achieves integrated molding of the base layer and the reinforcing layer, simplifying the production process and improving production efficiency. Therefore, this method not only solves the problem of material fatigue aging after repeated opening and closing of the flip structure, but also effectively suppresses the risk of localized combustion caused by uneven dispersion of flame retardants, ensuring the long-term reliability of the sheath in complex environments.

[0027] Through layered structural design and optimized material formulation, combined with precise process control, the overall manufacturing of low-voltage connector sheaths is achieved. The base layer uses PA66 as the main substrate, along with a halogen-free flame-retardant system, toughening agents, compatibilizers, and auxiliary additives to ensure a balance between structural strength and basic performance.

[0028] The halogen-free flame retardant system consists of red phosphorus masterbatch and MCA, which can be uniformly dispersed in the substrate to avoid the risk of combustion caused by insufficient local flame retardancy; the introduction of toughening agent effectively alleviates stress concentration when the flip structure is repeatedly opened and closed, and inhibits the initiation of microcracks; the compatibilizer strengthens the interfacial bonding between the components and reduces internal defects caused by poor compatibility.

[0029] The reinforcing layer covers key areas above the base layer. Its formulation increases the proportion of halogen-free flame retardant systems and adds epoxy resin and a curing agent to further enhance flame retardancy and mechanical strength. During manufacturing, the components of the base layer are first mixed according to the specified ratio and dried at 80-90℃ for 4-5 hours, with the moisture content strictly controlled to ≤0.1% to avoid the influence of moisture on molding quality. The components of the reinforcing layer are then dried at 85-95℃ for 5-6 hours, with the moisture content controlled to ≤0.08%.

[0030] Subsequently, injection molding is performed using a mold with at least two cavities. The first cavity corresponds to the base layer, and the second cavity corresponds to the reinforcement layer. The mold is preheated to 60-70℃ for the first cavity, 80-90℃ for the second cavity, and 240-250℃ for the hot runner to optimize material flowability and interlayer wettability. After the base layer material is injected into the first cavity, the main structure is ensured to be densely formed by setting parameters such as injection pressure of 80-100MPa, injection speed of 30-40mm / s, holding pressure of 60-70MPa, and holding time of 15-20s.

[0031] After cooling for 25-30 seconds, the formed base layer workpiece is transferred to the second cavity. When the reinforcing layer material is injected into the second cavity, it covers the key areas of the base layer. The injection parameters are adjusted to an injection pressure of 90-110 MPa, an injection speed of 25-35 mm / s, a holding pressure of 70-80 MPa, and a holding time of 20-25 seconds to achieve localized reinforcement.

[0032] Furthermore, while keeping the mold closed, the temperature of the second cavity is raised to 180-190℃ and held for 5-8 minutes to trigger the epoxy resin cross-linking reaction, forming a three-dimensional network structure that significantly enhances the mechanical strength and fatigue resistance of this area. Finally, the mold is cooled to 60-70℃ before demolding, completing the integral molding of the sheath. Thus, the various technical features work closely together, with layered design to define and reinforce specific areas, a formulation that addresses material compatibility and flame retardant dispersion issues, process parameters that ensure molding precision, and a cross-linking reaction that solidifies key structures. These elements work together to eliminate interface defects, uneven flame retardancy, and potential fatigue aging, ensuring the insulation stability and durability of the sheath in complex environments.

[0033] This application further proposes that the halogen-free flame retardant system in the base layer is composed of red phosphorus masterbatch and MCA, wherein the red phosphorus masterbatch accounts for 15-17% of the total mass of the base layer and the MCA accounts for 10-14% of the total mass of the base layer; the halogen-free flame retardant system in the reinforcing layer is composed of red phosphorus masterbatch, MCA and nano-magnesium hydroxide, wherein the red phosphorus masterbatch accounts for 18-22% of the total mass of the reinforcing layer, the MCA accounts for 8-12% of the total mass of the reinforcing layer and the nano-magnesium hydroxide accounts for 4-6% of the total mass of the reinforcing layer.

[0034] Specifically, a halogen-free flame retardant system refers to a combination of flame retardant formulations that do not contain halogen elements. This can be achieved by blending multiple flame retardant components in specific proportions. In practical applications, red phosphorus masterbatch is a flame retardant with red phosphorus as its core component. It exerts its gas-phase flame retardant effect by generating phosphoric acid substances during combustion. MCA refers to melamine cyanurate, which achieves condensed-phase flame retardant function by decomposing to produce melamine and cyanuric acid. Nano-magnesium hydroxide is an inorganic flame retardant with nanoscale particle size. It achieves both physical and chemical flame retardant effects by absorbing heat and cooling down upon thermal decomposition and generating a dense magnesium oxide layer to block oxygen.

[0035] In detail, this solution effectively optimizes the dispersion uniformity and material compatibility of the flame retardant by precisely defining the specific composition and proportion of the halogen-free flame retardant system in the base layer and the reinforcing layer. For the base layer, red phosphorus masterbatch and MCA are mixed at a ratio of 15-17% and 10-14%, respectively, achieving complementary synergistic effects of gas-phase and condensed-phase flame retardancy. This ratio range ensures that, within the framework of a total flame retardant content of 25-30%, it avoids the interfacial stress concentration problem caused by excessive red phosphorus, maintains material toughness, and improves the dispersion uniformity of the flame retardant during injection molding. For the reinforcing layer, nano-magnesium hydroxide is introduced as a key component, and the contents of red phosphorus masterbatch, MCA, and nano-magnesium hydroxide are controlled at ratios of 18-22%, 8-12%, and 4-6%, respectively. This not only enhances the flame retardant performance but also improves the interfacial bonding with epoxy resin through the high specific surface area of ​​nano-magnesium hydroxide, thereby improving the material density and the continuity of insulation resistance.

[0036] Based on this, the above scheme designs differentiated flame retardant system compositions and proportions to address the functional differences between the base layer and the reinforcement layer. The base layer needs to balance flame retardancy, toughness, and formability; therefore, the proportion of red phosphorus is slightly lower, and the proportion of MCA is moderate. The reinforcement layer prioritizes high flame retardancy and high density, hence the increased proportion of red phosphorus, while nano-magnesium hydroxide is introduced to supplement the condensed phase flame retardancy. This gradient proportioning design not only achieves an organic combination of overall basic protection and precise local reinforcement but also takes into account process adaptability and cost control, ultimately solving problems such as uneven flame retardant dispersion, high risk of localized combustion, and internal interface defects caused by imprecise proportion control.

[0037] This application further proposes that the auxiliary additives in the reinforcing layer include compatibilizer PP-g-MAH, antioxidant 1010, lubricant EBS and nano-montmorillonite, wherein PP-g-MAH accounts for 1-3% of the total mass of the reinforcing layer, antioxidant 1010 accounts for 0.4-0.6%, lubricant EBS accounts for 0.4-0.6%, and nano-montmorillonite accounts for 2-4%.

[0038] Specifically, the compatibilizer PP-g-MAH refers to a modified polypropylene material with maleic anhydride groups. It can be achieved by using PP-g-MAH with different molecular weights or grafting rates. Its purpose is to improve the interfacial compatibility between PA66 and the halogen-free flame retardant system through chemical bonding.

[0039] Antioxidant 1010 is a hindered phenolic antioxidant. Its antioxidant effect can be further enhanced by adding different types of auxiliary antioxidants (such as phosphites), aiming to prevent oxidative degradation of materials during injection molding. Lubricant EBS is a fatty acid amide lubricant. Other types of internal lubricants (such as zinc stearate) can be used as alternatives. Its purpose is to improve the dispersibility and flowability of components in highly filled systems. Nano-montmorillonite is a layered silicate material that can be modified through organic intercalation or used in combination with other nanofillers. Its purpose is to form a physical barrier network in the matrix through its layered structure, thereby improving the flame retardant and fatigue resistance of the material.

[0040] In detail, in the manufacturing method of the aforementioned sheath, a clear functional division and proportional compatibility are established among the various additives. The compatibilizer PP-g-MAH, through its maleic anhydride groups, interacts with the surfaces of PA66 and the flame retardant, respectively, constructing a stable ternary interfacial bridging system, thereby significantly reducing the formation of micropores within the material. Antioxidant 1010 captures free radicals under high-temperature processing conditions, protecting the polymer chains from oxidative degradation, while its dosage is consistent with that of lubricant EBS, avoiding the impact of excessive amounts of a single additive on other functions. Lubricant EBS, by reducing melt viscosity, optimizes the pressure and speed matching during the injection process, ensuring the uniform distribution of the flame retardant and other fillers.

[0041] The layered structure of nano-montmorillonite not only fills the micropores inside the material but also forms a composite network with the epoxy resin crosslinking system, further improving the material's density and fatigue resistance. Based on this, the proportions of each additive are precisely matched to the amounts of PA66, halogen-free flame retardant system, and epoxy resin in the reinforcing layer, ensuring a balanced improvement in overall performance.

[0042] Through the above technical solution, the interface defects between the plastic substrate and the flame retardant are effectively improved, the dispersion uniformity of the flame retardant is significantly enhanced, and the fatigue resistance of the material is strengthened, thereby solving the insulation failure problem caused by interface defects and uneven flame retardancy in the critical areas of the sheath. Simultaneously, this solution, combined with the aforementioned formulation design of the base layer and reinforcement layer of the sheath, further optimizes the overall performance of the material, providing reliable insulation and structural stability for low-voltage connector sheaths.

[0043] This application further proposes that in step S300, the barrel temperature is controlled in segments as follows: feeding section 230-240℃, compression section 245-255℃, nozzle section 255-260℃; and in step S400, the barrel temperature is controlled in segments as follows: feeding section 240-250℃, compression section 255-265℃, nozzle section 265-270℃.

[0044] Specifically, segmented barrel temperature control refers to managing the barrel temperature in sections according to the process requirements of different stages in the injection molding process. In practical applications, the feed section temperature can be 230-240℃ or 240-250℃. The purpose is to ensure that the base layer and reinforcing layer materials reach suitable initial melting states, preventing premature decomposition of red phosphorus masterbatch or MCA due to excessively high temperatures, while also preventing insufficient plasticization due to excessively low temperatures. The compression section temperature can be 245-255℃ or 255-265℃. The purpose is to enhance shear mixing through gradual temperature increases, promoting uniform melting of all components and ensuring the dispersion stability of the flame retardant. The nozzle section temperature can be 255-260℃ or 265-270℃. The purpose is to ensure that the melt has sufficient fluidity at high temperatures to fill complex cavities and reduce stress concentration caused by uneven flow resistance.

[0045] In detail, this solution addresses issues such as uneven melting, fluidity fluctuations, and component degradation caused by differences in the composition of the base layer and reinforcing layer materials. It utilizes a differentiated, segmented temperature system to provide a systematic solution. The base layer employs a medium-temperature system: 230-240℃ in the feed section, 245-255℃ in the compression section, and 255-260℃ in the nozzle section, with a 5℃ temperature gradient. This prevents premature decomposition of red phosphorus and maintains PA66 crystallinity at 30-35%, balancing strength and toughness. The reinforcing layer employs a high-temperature system: 240-250℃ in the feed section, 255-265℃ in the compression section, and 265-270℃ in the nozzle section, with a 10℃ temperature gradient. This adapts to the melting requirements of epoxy resin, reduces the viscosity of the high-filler melt, and ensures PA66 crystallinity ≥25%.

[0046] Both layers are 20-30°C lower than the thermal stability temperature of their corresponding functional components to prevent component degradation. The 10°C temperature difference precisely matches the differences in material composition, and the gradient heating enhances the shear mixing effect. The overall temperature strategy optimizes melt uniformity, component stability, and filling density, effectively reducing microporosity and stress cracks at the joints, and ensuring the continuity of insulation resistance and flame retardancy.

[0047] Through the above technical solutions, the melting uniformity of the base layer is improved by 40%, the melt viscosity of the reinforcing layer is reduced by 30%, the uneven dispersion rate of flame retardant is reduced by 70%, and the microporosity at the joint is ≤0.05%. At the same time, the retention rate of effective flame retardant components is ≥95%, the stress cracking rate at the sheath joint is reduced by 80%, and the insulation breakdown voltage is increased by 25% (≥25kV / mm).

[0048] This application further proposes that in the manufacturing method of the above-mentioned low-voltage connector sheath, step S100 also includes mixing the components by stirring them for 10-20 minutes using a high-speed mixer with a rotation speed of 1800-2200 r / min.

[0049] In practical applications, a high-speed mixer refers to a device that uses mechanical rotation to generate shear force to achieve uniform material dispersion. It can be implemented using a horizontal mixer, a vertical mixer, or a double-cone mixer. The selection of a rotation speed of 1800-2200 r / min is to match the particle characteristics of components such as red phosphorus masterbatch, MCA, and nano-magnesium hydroxide, ensuring that agglomerates are broken up without damaging the particle structure. Specifically, a mixing time of 10-20 minutes is used to balance mixing uniformity and frictional heat control within this timeframe. The purpose is to prevent component performance degradation due to excessive temperature while ensuring thorough penetration and bonding of all components.

[0050] In detail, this solution addresses the issue of uneven raw material mixing by introducing a high-speed mixing process with specific parameters. First, a rotation speed range of 1800-2200 r / min generates moderate shear force, effectively breaking up the agglomeration of red phosphorus masterbatch and MCA in the PA66 matrix, while avoiding the risk of material degradation caused by excessively high rotation speeds. Second, a 10-20 minute stirring time window not only ensures sufficient penetration and bonding of each component under high-speed shearing, but also controls frictional heat through time constraints, maintaining the material temperature below 60℃ to prevent hydrolysis of the red phosphorus masterbatch and softening of the toughening agent. Based on this, the synergistic design of rotation speed and time significantly improves the compatibility of the halogen-free flame retardant system with the base resin, reduces the formation of interfacial defects within the material, and provides a highly uniform raw material base for subsequent drying and injection molding steps, thereby enhancing the overall flame retardant continuity and insulation stability of the sheath.

[0051] Furthermore, this mixing process is closely integrated with subsequent drying and injection molding processes. Strict temperature control during mixing ensures that the red phosphorus masterbatch does not hydrolyze due to the high-temperature pretreatment in the subsequent drying step. Simultaneously, the uniform material state reduces uneven moisture distribution during drying, providing a stable raw material foundation for injection molding. Through precise control of these process parameters, localized combustion and microporosity caused by uneven dispersion are effectively avoided, while also mitigating the risk of stress concentration due to insufficient compatibility.

[0052] This application further proposes that step S500 includes ring-opening polymerization of the epoxy resin in the reinforcing layer formulation at 180-190°C under the catalysis of the curing agent dicyandiamide.

[0053] Epoxy resin refers to a polymer compound containing epoxy groups, which can be achieved using bisphenol A type epoxy resin or aliphatic epoxy resin. The purpose is to form a three-dimensional cross-linked network through ring-opening polymerization, thereby improving the mechanical properties and interfacial bonding strength of the material. Dicyandiamide, as a curing agent, is a compound with highly efficient catalytic properties. It can promote the ring-opening reaction of epoxy resin by slowly releasing active groups, ensuring the uniform progress of the cross-linking process. Ring-opening polymerization refers to the process in which epoxy resin molecular chains break and reconnect under specific conditions to form a network structure. Its purpose is to strengthen the bond between the reinforcing layer and the base layer through chemical bonding, while reducing interfacial defects.

[0054] Specifically, this solution effectively addresses the interfacial bonding defect problem by clearly defining the specific mechanisms and conditions of the crosslinking reaction. First, by specifying the epoxy resin in the reinforcing layer formulation as the reactant, the reaction is ensured to be limited to the internal components of the reinforcing layer, avoiding interference from external impurities. This allows the crosslinking process to be precisely focused on key areas, thereby improving the reaction's targeting. Second, dicyandiamide is used as a curing agent for catalysis. Dicyandiamide possesses highly efficient and controllable catalytic properties, promoting the ring-opening polymerization of epoxy resin molecules at a specific temperature. This reaction mechanism forms a more uniform and dense three-dimensional crosslinked network, significantly reducing microporosity and stress concentration at the interface, and strengthening the bond strength between the reinforcing layer and the base layer. Finally, a temperature range of 180-190℃ is defined, closely matching the mold heating steps. This ensures the ring-opening polymerization reaction proceeds fully while preventing excessive temperature from causing material degradation, making the crosslinking process stable and reliable. Ultimately, this eliminates interfacial defects between the reinforcing layer and the base layer, improving the integrity of the overall insulation barrier and the continuity of its flame-retardant properties.

[0055] Furthermore, the hydroxyl groups generated after the ring-opening polymerization of epoxy resin form hydrogen bonds with the amino groups on the PA66 molecular chain in the base layer, and simultaneously form coordination bonds with the surface hydroxyl groups of nano-magnesium hydroxide and nano-montmorillonite in the reinforcing layer, achieving cross-layer chemical bonding between the reinforcing and base layers. This design not only strengthens the interfacial bonding but also encapsulates the flame retardant particles through a three-dimensional cross-linked network, preventing their migration and aggregation, and further enhancing flame retardant continuity. The design of the entire reaction mechanism ensures both the targetedness and sufficiency of the cross-linking process and significantly improves the insulation performance of the sheath in humid or dusty environments, ensuring the performance stability of critical areas of the sheath.

[0056] This application further proposes that after step S600, a step S700 is included, in which the product is subjected to constant temperature treatment in a hot air oven at 70-90°C for 1-3 hours.

[0057] Specifically, a hot air oven is a device that provides a uniform heat field through forced convection, and it can be implemented using either electric heating or steam heating. The choice of a constant temperature treatment time of 1-3 hours is to balance the need for sufficient internal stress release with production efficiency, aiming to ensure the stability of the product's internal structure while avoiding efficiency degradation due to over-treatment. The temperature range of 70-90℃ is a parameter range precisely designed based on material properties, aiming to simultaneously meet the requirements of molecular chain relaxation and epoxy resin post-curing.

[0058] In detail, performing hot air oven treatment immediately after mold cooling and demolding is of significant technological importance. This step can promptly intervene in the instantaneous internal stress caused by the sudden temperature change and mechanical stress release during demolding, preventing its accumulation and formation of micropores in critical areas. The selected temperature range of 70-90℃ is higher than the glass transition temperature of PA66, for example, about 50℃, ensuring that the molecular chains have sufficient mobility to relax stress, while being within the post-curing temperature window of dicyandiamide (70-100℃), effectively activating the residual epoxy groups to continue the reaction. The hot air circulation method provides uniform heat transfer, eliminates local temperature gradients, and ensures consistent post-curing degree in all areas of the reinforcing layer. Through 1-3 hours of isothermal treatment, not only is molecular rearrangement and stress release promoted, but the three-dimensional network structure of the epoxy resin system in the reinforcing layer is also improved, thereby significantly enhancing the structural density and fatigue resistance of weak parts such as the bending area of ​​the top cover.

[0059] Based on this, the proposed solution forms a close technical link with the aforementioned manufacturing method for low-voltage connector sheaths. By introducing a specially designed isothermal treatment step after injection molding, the problem of insufficient release of internal stress after demolding is solved, and the complete cross-linking reaction of the epoxy resin is promoted. This process design specifically targets key areas such as the junction of the top cover and the body, the pin contact area, and the bending area, effectively preventing the generation of micropores and stress cracks, and significantly enhancing the long-term reliability and flame-retardant continuity of the insulation barrier.

[0060] This application further proposes a method for manufacturing the aforementioned low-voltage connector sheath, wherein the sheath is integrally formed by two-color injection molding of a base layer and a reinforcing layer.

[0061] Specifically, two-color injection molding refers to the combination of two different materials through two injection processes within the same mold. This can be achieved using a two-color injection molding machine with two independent barrels and injection devices. One-piece molding refers to the integrated manufacturing of multiple parts or areas in a single molding process, aiming to reduce subsequent assembly steps and improve structural integrity.

[0062] In detail, this manufacturing method first achieves the overall structure of the sheath through step-by-step injection molding of the base layer and the reinforcing layer. In the first stage, the base layer material is injected into the first cavity of the mold, forming the basic structure of the sheath; subsequently, in the second stage, the reinforcing layer material is injected into the second cavity of the mold, covering the critical areas of the base layer. This two-color injection molding process ensures that the reinforcing layer can accurately cover vulnerable areas such as the junction between the top cover and the body, the inner wall of the pin contact area, and the bending area of ​​the top cover, thereby effectively preventing the occurrence of microporosity, stress cracks, and material fatigue aging problems.

[0063] Building upon this, in-mold crosslinking technology is used to tightly bond the reinforcing layer and the base layer. In-mold crosslinking refers to the use of a chemical reaction during injection molding to form a strong bond between the two materials at the interface. This can be achieved through the ring-opening polymerization reaction of epoxy resin under the action of a curing agent. This process not only improves the bonding strength between the two layers but also eliminates interface defects caused by poor compatibility between the plastic substrate and the flame retardant, thereby ensuring the insulation resistance and mechanical strength stability of the overall structure.

[0064] Furthermore, this solution achieves precise protection through targeted reinforcement design of key areas. For example, the microporosity at the joint is significantly reduced, the wear resistance and flame retardant continuity of the pin contact area are improved, and the fatigue resistance of the top cover bending area is greatly improved. At the same time, the thickness of the reinforcement layer is controlled within the range of 0.3-0.5mm, ensuring both reinforcement effect and without affecting the flexibility of the top cover's flipping mechanism, thus solving the problem of the conflict between reinforcement and function in traditional solutions.

[0065] Example 1

[0066] Formula ratio The base layer accounts for 85% of the total. PA66: 62%, relative viscosity 2.8 Halogen-free flame retardant system: 28%, of which red phosphorus masterbatch 16% and MCA 12%. Toughening agent (EPDM-g-MAH, grafting rate 1.2%): 6% Compatibilizer (PP-g-MAH, grafting rate 0.8%): 2% Auxiliary agents: 2%, including antioxidant 10980.5%, lubricant EBS 0.8%, and ultraviolet absorber UV-531 0.7%. Reinforcement layer, 15% of total weight PA66: 55%, relative viscosity 3.0 Halogen-free flame retardant system: 35%, comprising 20% ​​red phosphorus masterbatch, 10% MCA, and 5% nano-magnesium hydroxide. Epoxy resin (E-51): 3% Curing agent (dicyandiamide): 1% Auxiliary agents: 6%, including compatibilizer PP-g-MAH 2%, antioxidant 1010 0.5%, lubricant EBS 0.5%, and nano-montmorillonite 3%.

[0067] like Figure 1 As shown, the process flow S100. Raw material mixing and drying: Each component of the base layer is put into a high-speed mixer, stirred at 2000r / min for 15 minutes, dried at 85℃ for 4 hours, and the moisture content is controlled at 0.08%; Each component of the reinforcing layer is stirred at the same speed for 15 minutes, dried at 90℃ for 5 hours, and the moisture content is controlled at 0.06%.

[0068] S200, Mold preparation: Use a rotary two-color mold. Preheat the first cavity to 65°C, the second cavity to 85°C, and the hot runner temperature to 245°C.

[0069] S300, base layer injection molding: barrel segment temperature (feeding section 235℃, compression section 250℃, nozzle section 258℃), injection pressure 90MPa, injection speed 35mm / s, holding pressure 65MPa, holding time 18s, and after cooling for 28s, transfer to the second cavity.

[0070] S400, Reinforced Layer Injection Molding: Barrel segment temperature (feeding section 245℃, compression section 260℃, nozzle section 268℃), injection pressure 100MPa, injection speed 30mm / s, holding pressure 75MPa, holding time 22s, covering joints, pin insertion area, and bending area.

[0071] S500, In-mold crosslinking: The second cavity is heated to 185℃ and held for 6 minutes to trigger the ring-opening polymerization of epoxy resin.

[0072] S600 Demolding: Cool the mold to 65℃ and open the demolding mechanism.

[0073] S700, constant temperature treatment: 80℃ hot air oven for 2 hours to eliminate internal stress.

[0074] Example 2 (S700 isothermal treatment omitted)

[0075] Formula ratio Completely consistent with Example 1.

[0076] Process Flow Except for omitting step S700, the remaining process parameters are the same as in Example 1, that is, direct inspection after demolding.

[0077] Example 3 (Reinforcing layer without nano-montmorillonite)

[0078] Formula ratio base layer Consistent with Example 1.

[0079] Reinforcement layer, 15% of total weight PA66 (relative viscosity 3.0): 58% Halogen-free flame retardant system: 35%, comprising 20% ​​red phosphorus masterbatch, 10% MCA, and 5% nano-magnesium hydroxide. Epoxy resin (E-51): 3% Curing agent (dicyandiamide): 1% Auxiliary agents: 3%, including compatibilizer PP-g-MAH 2%, antioxidant 1010 0.5%, lubricant EBS 0.5%, nano-montmorillonite removed, and the proportion of PA66 adjusted.

[0080] Process Flow Completely consistent with Example 1.

[0081] Example 4 (Red phosphorus masterbatch ratio in the base layer is below the range)

[0082] Formula ratio The base layer accounts for 85% of the total. PA66 (relative viscosity 2.8): 63% Halogen-free flame retardant system: 28%, including 14% red phosphorus masterbatch and 14% MCA. Toughening agent (EPDM-g-MAH): 6% Compatibilizer (PP-g-MAH): 2% Adjuvants: 2% Enhancement layer Consistent with Example 1.

[0083] Process Flow Completely consistent with Example 1.

[0084] Example 5 (Reinforced layer nozzle temperature out of range)

[0085] Formula ratio Completely consistent with Example 1.

[0086] Process Flow Except for adjusting the temperature of the nozzle section of the S400 reinforced layer to 275℃ (exceeding the range of 265-270℃), the other process parameters are the same as in Example 1.

[0087] Example 6 (High-speed mixing speed below range)

[0088] Formula ratio Completely consistent with Example 1.

[0089] Process Flow Except for adjusting the mixing speed of S100 to 1700 r / min, which is below the range of 1800-2200 r / min, and keeping the stirring time at 15 minutes, the other process parameters are the same as in Example 1.

[0090] Example 7 (Reinforcing layer epoxy resin and curing agent are lower limits)

[0091] Formula ratio base layer Consistent with Example 1.

[0092] Reinforcement layer, 15% of total weight; PA66 (relative viscosity 3.0): 56% Halogen-free flame retardant system: 35%, comprising 20% ​​red phosphorus masterbatch, 10% MCA, and 5% nano-magnesium hydroxide. Epoxy resin (E-51): 2% Curing agent (dicyandiamide): 0.5% Auxiliary agents: 6.5%, including compatibilizer PP-g-MAH 2%, antioxidant 1010 0.5%, lubricant EBS 0.5%, and nano-montmorillonite 3.5%. Process Flow Completely consistent with Example 1.

[0093] Example 8

[0094] Formula ratio The base layer accounts for 85% of the total. PA66 (relative viscosity 2.8): 65% Halogen-free flame retardant system: 25%, of which red phosphorus masterbatch 15% and MCA 10%. Toughening agent (EPDM-g-MAH): 5% Compatibilizer (PP-g-MAH): 3% Adjuvants: 2% Enhancement layer Consistent with Example 1.

[0095] Process Flow Completely consistent with Example 1.

[0096] Example Insulation resistance (Ω·cm) Flame retardant rating (1.6mm) Number of times the top cover is bent (no cracks) Interfacial bonding strength (N / cm) Insulation fluctuations in humid environments Main defects 1 <![CDATA[1.2×10 14 ]]> UL94 V-0 2000 times 62 ±2.1% / 2 <![CDATA[1.1×10 14 ]]> UL94 V-0 800 times 58 ±4.8% Residual internal stress, poor fatigue resistance 3 <![CDATA[0.9×10 14 ]]> UL94 V-0 1200 times 50 ±3.5% Without nano-montmorillonite, the density is insufficient. 4 <![CDATA[1.0×10 14 ]]> UL94 V-1 1800 times 60 ±2.5% Insufficient red phosphorus content results in weak localized flame retardancy. 5 <![CDATA[0.8×10 14 ]]> UL94 V-0 1500 times 45 ±5.2% High temperatures cause slight degradation of flame retardants 6 <![CDATA[0.7×10 14 ]]> UL94 V-1 1000 times 48 ±6.3% Uneven mixing, flame retardant agglomeration 7 <![CDATA[0.9×10 14 ]]> UL94 V-0 1300 times 42 ±3.8% Insufficient cross-linking, weak interfacial bonding 8 <![CDATA[1.0×10 14 ]]> UL94 V-0 1600 times 55 ±2.8% Insufficient toughening agent, resulting in slightly poor toughness. Example 1, as a baseline scheme employing the complete process and standard formulation, achieves an insulation resistance of 1.2 × 10⁻⁶. 14 Ω・cm, flame retardant rating of UL94V-0, no cracks after 2000 bends of the top cover, interface bonding strength of 62N / cm, insulation fluctuation of only ±2.1% in humid environments, and optimal overall performance.

[0097] Example 2 omitted the post-demolding isothermal treatment, resulting in residual internal stress and a significant decrease in fatigue resistance, with the bending cycle reduced to 800 cycles and insulation fluctuation increasing to ±4.8%. Example 3 removed the nano-montmorillonite from the reinforcing layer, leading to insufficient material density and a decrease in insulation resistance and interfacial bonding strength to 0.9 × 10⁻⁶. 14 Ω・cm and 50N / cm; Example 4: The proportion of red phosphorus masterbatch in the base layer was lower than the specified range, the synergistic effect of flame retardancy between the gas phase and condensed phase was weakened, and the flame retardant rating dropped to UL94V-1; Example 5: The nozzle temperature of the reinforcing layer exceeded the reasonable range, causing slight degradation of the flame retardant, and the insulation resistance and interfacial bonding strength were as low as 0.8×10 Ω・cm and 50N / cm; 14 Ω・cm and 45N / cm; In Example 6, the high-speed mixing speed did not meet the requirements, the flame retardant was unevenly dispersed, the insulation fluctuation reached ±6.3%, and the flame retardant level dropped to UL94V-1; In Example 7, the lower limit ratio of epoxy resin to curing agent in the reinforcing layer was used, the crosslinking reaction was insufficient, and the interfacial bonding strength was only 42N / cm; In Example 8, the base layer adopted a combination of PA66 upper limit, flame retardant system and toughening agent lower limit and compatibilizer upper limit. Although the overall performance was slightly lower than that of Example 1, the core indicators such as insulation resistance and flame retardant level still met the usage requirements, which proved the rationality of the formulation ratio range.

[0098] The aforementioned performance differences are all directly related to the variable adjustments in each embodiment, highlighting the crucial role of complete process steps, reasonable formulation components, and parameter ranges in ensuring the insulation stability, flame retardant reliability, and mechanical durability of low-voltage connector sheaths.

[0099] Example 9 like Figure 2 As shown, in another embodiment, this application also discloses a horn cover, which is an integral structure made by the above manufacturing method. It includes an upper cover 20 connected to the body 10 through a flip structure. The upper cover 20 and the body 10 are covered with a reinforcing layer that is bonded to the base layer through in-mold cross-linking at the junction of the upper cover 20 and the body 10, the inner wall of the pin contact area and the bending area of ​​the upper cover 20.

[0100] The core innovation of this embodiment lies in systematically solving the reliability problem of weak parts of the speaker housing by combining an integrated structural design with local reinforcement of key areas. Specifically, the integrated structure eliminates the seam hazards of traditional split designs, reducing the risk of stress concentration as a whole; the flip structure achieves a functional connection between the upper cover 20 and the body 10, while providing a structural basis for repeated opening and closing operations; a reinforcing layer is applied to the joint between the upper cover 20 and the body 10, the inner wall of the pin contact area, and the bending area of ​​the upper cover 20, directly targeting high-risk areas prone to micropores and stress cracks; and through in-mold cross-linking and bonding with the base layer, the reinforcing layer and the base layer are ensured to form a seamless whole, effectively eliminating interface defects.

[0101] These features work synergistically: the integrated structure acts as a whole frame to reduce initial defects, the flipped structure defines functional areas, the reinforcing layer provides local strength support at designated locations, and the in-mold cross-linking technology ensures bonding quality. Together, they suppress the formation of micropores, prevent crack propagation, and improve the fatigue resistance of the material, ultimately improving insulation reliability and structural durability.

[0102] In practical applications, the halogen-free flame-retardant system in the base layer can be understood as a composite system composed of multiple flame-retardant components. Its main function is to achieve flame-retardant effects through the synergistic effect of different flame-retardant mechanisms. For example, a combination of melamine phosphate and expanded graphite, or a mixture of aluminum hydroxide and zinc borate, can be used as alternatives. The purpose is to form a dense char layer during material combustion to isolate oxygen and heat.

[0103] Furthermore, the epoxy resin in the reinforcing layer can be selected from bisphenol A type epoxy resin or aliphatic epoxy resin. These materials can undergo a cross-linking reaction under the action of the curing agent, thereby improving the mechanical properties and interfacial bonding ability of the material. As a preferred embodiment, the curing agent can be selected from amine curing agents or acid anhydride curing agents, which can adjust the reaction rate according to the process temperature requirements to ensure the controllability of the cross-linking reaction.

[0104] Specifically, the drying process in step S100 can be achieved using a vacuum drying oven or a forced-air drying oven. Its purpose is to remove moisture from the raw materials and prevent moisture from affecting subsequent processing. Furthermore, the injection molding parameters in steps S300 and S400 can be adjusted appropriately based on the specific performance of the equipment; for example, the molding quality can be optimized by changing the injection speed or holding pressure.

[0105] The innovation of this application lies in solving the interface defect problem caused by poor material compatibility in the traditional low-voltage connector sheath manufacturing process by combining layered structural design with optimized material formulation. Furthermore, by introducing an epoxy resin cross-linking reaction into the reinforcing layer, the mechanical strength and fatigue resistance of critical areas are improved, while avoiding the interface delamination phenomenon commonly seen in traditional layered molding processes. In addition, the use of sequential injection molding achieves integrated molding of the base layer and the reinforcing layer, simplifying the production process and improving production efficiency. Therefore, this method not only solves the problem of material fatigue aging after repeated opening and closing of the flip structure, but also effectively suppresses the risk of localized combustion caused by uneven dispersion of flame retardants, ensuring the long-term reliability of the sheath in complex environments.

[0106] Through layered structural design and optimized material formulation, combined with precise process control, the overall manufacturing of low-voltage connector sheaths is achieved. The base layer uses PA66 as the main substrate, along with a halogen-free flame-retardant system, toughening agents, compatibilizers, and auxiliary additives to ensure a balance between structural strength and basic performance.

[0107] Specifically, the halogen-free flame retardant system consists of red phosphorus masterbatch and MCA, which can be uniformly dispersed in the substrate to avoid the risk of combustion caused by insufficient local flame retardancy. The introduction of toughening agent effectively alleviates stress concentration during repeated opening and closing of the flip structure and inhibits the initiation of microcracks. Compatibilizer strengthens the interfacial bonding between components and reduces internal defects caused by poor compatibility. The reinforcing layer covers key areas on top of the base layer. Its formulation increases the proportion of the halogen-free flame retardant system and adds epoxy resin and curing agent to further improve flame retardant performance and mechanical strength.

[0108] During the manufacturing process, the components of the base layer are first mixed according to the specified ratio and dried at 80-90℃ for 4-5 hours, with the moisture content strictly controlled to ≤0.1% to avoid the influence of moisture on the molding quality. The components of the reinforcing layer are then dried at 85-95℃ for 5-6 hours, with the moisture content controlled to ≤0.08%. Subsequently, injection molding is performed using a mold with at least two cavities. The first cavity corresponds to the base layer, and the second cavity corresponds to the reinforcing layer. The mold is preheated to 60-70℃ for the first cavity, 80-90℃ for the second cavity, and 240-250℃ for the hot runner to optimize material flowability and interlayer wettability.

[0109] After the base layer material is injected into the first cavity, the main structure is densely molded by setting the injection pressure to 80-100MPa, injection speed to 30-40mm / s, holding pressure to 60-70MPa, and holding time to 15-20s. After cooling for 25-30s, the molded base layer workpiece is transferred to the second cavity. When the reinforcing layer material is injected into the second cavity, it covers the key areas of the base layer. The injection parameters are adjusted to an injection pressure of 90-110MPa, an injection speed of 25-35mm / s, a holding pressure of 70-80MPa, and a holding time of 20-25s to achieve localized reinforcement. Further, the mold is kept closed, and the temperature of the second cavity is raised to 180-190℃ and held for 5-8 minutes to trigger the epoxy resin crosslinking reaction, forming a three-dimensional network structure that significantly enhances the mechanical strength and fatigue resistance of this area. Finally, the mold is cooled to 60-70℃ before demolding, completing the integral molding of the sheath.

[0110] Thus, the various technical features work together closely, with layered design to position and reinforce specific areas, formulations to address material compatibility and flame retardant dispersion issues, process parameters to ensure molding precision, and cross-linking reactions to solidify key structures. Together, these features eliminate interface defects, uneven flame retardancy, and potential fatigue aging hazards, ensuring the insulation stability and durability of the sheath in complex environments.

[0111] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for manufacturing a low-voltage connector sheath, characterized in that, The sheath is integrally formed by injection molding a base layer and a reinforcing layer in sequence. The formulation of the base layer, by weight percentage, includes: 60-65% PA66, 25-30% halogen-free flame retardant system, 5-7% toughening agent, 1-3% compatibilizer, and 1-3% auxiliary additives; The formulation of the reinforcing layer, by weight percentage, includes: 50-60% PA66, 30-40% halogen-free flame retardant system, 2-4% epoxy resin, 0.5-1.5% curing agent, and 5-7% auxiliary additives; The halogen-free flame retardant system comprises red phosphorus masterbatch and MCA; The manufacturing method includes the following steps: S100. After mixing the components of the base layer according to the specified ratio, dry at 80-90℃ for 4-5 hours, controlling the moisture content to ≤0.1%; after mixing the components of the reinforcement layer according to the specified ratio, dry at 85-95℃ for 5-6 hours, controlling the moisture content to ≤0.08%. S200: A mold with at least two cavities is used, the first cavity corresponding to the base layer and the second cavity corresponding to the reinforcement layer; Preheat the mold to a temperature of 60-70℃ for the first cavity, 80-90℃ for the second cavity, and 240-250℃ for the hot runner. S300. Inject the pretreated base layer material into the first cavity. The injection parameters are: injection pressure 80-100MPa, injection speed 30-40mm / s, holding pressure 60-70MPa, holding time 15-20s, and after cooling for 25-30s, transfer the formed base layer workpiece to the second cavity. S400. Inject the pretreated reinforcing layer material into the second cavity to cover the key areas of the base layer. The injection parameters are: injection pressure 90-110MPa, injection speed 25-35mm / s, holding pressure 70-80MPa, holding time 20-25s. S500: Keep the mold closed, raise the temperature of the second cavity to 180-190℃, hold for 5-8 minutes to trigger the cross-linking reaction of the epoxy resin; S600: Demold after cooling the mold to 60-70℃.

2. The method for manufacturing a low-voltage connector sheath according to claim 1, characterized in that, The halogen-free flame retardant system in the base layer consists of red phosphorus masterbatch and MCA, wherein the red phosphorus masterbatch accounts for 15-17% of the total mass of the base layer and the MCA accounts for 10-14% of the total mass of the base layer; The halogen-free flame retardant system in the reinforcing layer consists of red phosphorus masterbatch, MCA and nano magnesium hydroxide, wherein the red phosphorus masterbatch accounts for 18-22% of the total mass of the reinforcing layer, MCA accounts for 8-12% of the total mass of the reinforcing layer, and nano magnesium hydroxide accounts for 4-6% of the total mass of the reinforcing layer.

3. The method for manufacturing a low-voltage connector sheath according to claim 1 or 2, characterized in that, The auxiliary additives in the reinforcing layer include compatibilizer PP-g-MAH, antioxidant 1010, lubricant EBS, and nano-montmorillonite, wherein PP-g-MAH accounts for 1-3% of the total mass of the reinforcing layer, antioxidant 1010 accounts for 0.4-0.6%, lubricant EBS accounts for 0.4-0.6%, and nano-montmorillonite accounts for 2-4%.

4. The method for manufacturing a low-voltage connector sheath according to claim 1, characterized in that, In step S300, the barrel temperature is controlled in segments as follows: feeding section 230-240℃, compression section 245-255℃, nozzle section 255-260℃; In step S400, the barrel temperature is controlled in segments as follows: feeding section 240-250℃, compression section 255-265℃, and nozzle section 265-270℃.

5. The method for manufacturing a low-voltage connector sheath according to claim 1, characterized in that, Step S100 further includes mixing the components by stirring them for 10-20 minutes using a high-speed mixer with a rotation speed of 1800-2200 r / min.

6. The method for manufacturing a low-voltage connector sheath according to claim 1, characterized in that, Step S500 further includes the ring-opening polymerization of the epoxy resin in the reinforcing layer formulation at 180-190°C under the catalysis of the curing agent dicyandiamide.

7. The method for manufacturing a low-voltage connector sheath according to claim 1 or 6, characterized in that, After step S600, step S700 is also included: the product is kept at a constant temperature in a hot air oven at 70-90℃ for 1-3 hours.

8. The method for manufacturing a low-voltage connector sheath according to claim 7, characterized in that, The sheath is made of a base layer and a reinforcing layer integrally formed by two-color injection molding.

9. A speaker cover, characterized in that, The horn cover is an integral structure manufactured by the manufacturing method of any one of claims 1-8, comprising an upper cover connected to the body via a flip structure, wherein the upper cover and the body are joined, the inner wall of the pin contact area and the bending area of ​​the upper cover are covered with a reinforcing layer bonded to the base layer via in-mold cross-linking.

Images