Polyamide composite material as well as preparation method and application thereof

Abstract

The invention belongs to the field of polymer compositions, and particularly relates to a polyamide composite material and a preparation method and application thereof. According to the technical scheme, the polyamide composite material is prepared from the following components in parts by weight: 65 to 85 parts of PA66 resin, 10 to 35 parts of reinforcing filler, 0.5 to 2 parts of lubricating agent and 0 to 5 parts of other auxiliary agents, and the amino-terminated group content of the PA66 resin is 110 to 140 mmol / kg. When the polyamide composite material prepared by selecting the PA66 resin with the amino-terminated group content in the range of 110-140 mmol / kg as the base material is used as the shell material of the PIN connector, the prepared PIN connector has better air tightness. The possible mechanism is that lone pair electrons on an N atom in an amino-terminated group enable the resin and the metal PIN to form a coordinate bond, and macroscopically, the air tightness of the composite material and the metal PIN is good, so that the problem of air leakage of a workpiece is solved.

Description

Technical Field

[0001] This invention belongs to the field of polymer compositions, specifically relating to polyamide composite materials, their preparation methods, and applications. Background Technology

[0002] PIN connectors are a common type of connector, widely used for power and communication connections between electronic devices. They are easy to install and remove and have high reliability, bringing many conveniences to the interconnection and expansion of devices.

[0003] A PIN connector consists of a housing and multiple metal pins. Depending on the operating environment, some connectors, especially high-voltage connectors used in new energy vehicles, need to have good airtightness to meet waterproof requirements. This is to prevent the connector from failing due to moisture or water ingress, thus affecting the normal operation of the equipment and ensuring user safety.

[0004] Existing PIN connector designs can be broadly categorized into two types. One type involves inserting the pins into the housing and then applying adhesive to the pins. In this design, the pins are prone to detaching during soldering, repair, and disassembly, leading to airtightness failure and reducing the connector's lifespan. The other type involves injection molding the pins into the housing. This design carries a risk of airtightness failure, especially when the number of PIN pins is large. The main reason for this risk is that during the injection molding process, there is cooling shrinkage stress between the pins and the molten composite material, resulting in tiny gaps between the pins and the composite material.

[0005] To achieve better airtightness in PIN connectors, common techniques include coating the PIN surface with epoxy or silicone sealant; modifying the PIN structure design; and optimizing the injection molding process, such as gate design and mold temperature adjustment. However, there are currently no reports on improving the airtightness of PIN connectors from the perspective of material formulation design for the connector housing. Summary of the Invention

[0006] To address one of the aforementioned problems in the prior art, the present invention aims to provide a polyamide composite material with good airtightness, its preparation method, and its application, specifically achieved through the following technical solution: Polyamide composite materials, by weight, include the following components: 65-85 parts of PA66 resin, 10-35 parts of reinforcing filler Lubricant 0.5~2 parts, Other auxiliary agents: 0-5 parts The terminal amino content of the PA66 resin is 110~140 mmol / kg.

[0007] Optionally, the reinforcing filler includes: 10-35 parts glass fiber and 0-30 parts mineral powder.

[0008] Optionally, the glass fiber is a long glass fiber or a short glass fiber treated with a silane coupling agent.

[0009] Optionally, the mineral powder is one or more of the following: glass powder, glass microspheres, talc powder, kaolin, wollastonite, mica, montmorillonite, calcium carbonate, alumina, magnesium oxide, magnesium carbonate, barium sulfate, calcium silicate, magnesium silicate, and aluminum silicate.

[0010] Optionally, the lubricant is one or more of fatty acids and their esters, fatty acid amides, and metal soaps.

[0011] Optionally, the other additives are one or more of antioxidants, colorants, release agents, anti-glass fiber exposure agents, and toughening agents.

[0012] This application also provides a method for preparing a polyamide composite material, comprising the following steps: mixing other components except glass fiber and feeding them into a screw extruder as a main feeder and glass fiber as a side feeder, followed by melt extrusion and granulation to obtain a polyamide composite material, wherein the screw extruder temperature is 270~320℃ and the speed is 300~400rpm.

[0013] This application also provides the application of the polyamide composite material according to any of the foregoing claims for improving the airtightness of PIN connectors, wherein the polyamide composite material is used as the raw material for the PIN connector housing and is integrally formed with the PIN pins by an insert injection molding process.

[0014] Experiments have shown that polyamide composite materials prepared using PA66 resin with a terminal amino content in the range of 110~140 mmol / kg as the base material produce PIN connectors with better airtightness when used as the housing material for PIN connectors.

[0015] The possible mechanism is that the lone pair electrons on the N atom in the terminal amino group enable the resin to form a coordinate bond with the metal pin, which macroscopically results in good airtightness between the composite material and the metal pin, thereby solving the problem of air leakage in the part.

[0016] It should be noted that the airtightness of the PIN connector involved in this invention differs from the bonding strength (or adhesive effect) performance indicators between the metal and polyamide composite materials. Bonding strength refers to the strength of a "point," indicating how difficult it is for the two bonded parts to separate; this can be improved by altering the polarity. Airtightness, on the other hand, refers to the integrity of a "surface" or "volume," indicating the degree of gas leakage. Strong bonding strength can ensure the overall structure does not separate, but it cannot eliminate microscopic leakage paths. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure at the pin position in a pin connector. Detailed Implementation

[0018] The specific implementation of this application is described in detail below through examples. However, the specific implementation of this application is not intended to limit the technical solution of this application. Any non-substantial changes, such as replacing common technical solutions in the field, using the technical solutions described in the embodiments of this application are within the protection scope of this application.

[0019] Unless otherwise specified, the experimental methods used in the following examples and comparative examples are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0020] The sources of some of the raw materials in the examples and comparative examples are as follows, but they should not be construed as limiting the scope of this application: PA66 Resin A: Terminal amino content 110 mmol / kg, Zhejiang Huafeng, EP126NH; PA66 resin B: terminal amino content 140mmol / kg, provided by Zhejiang Huafeng; PA66 resin C: terminal amino content 85mmol / kg, Zhejiang Huafeng, EP158NH; PA66 resin D: terminal amino content 180mmol / kg, provided by Zhejiang Huafeng; It should be noted that the content of the above-mentioned terminal amino groups was selected after testing; Fiberglass: ECS10-4.5-568H Jushi Fiberglass; Talc powder: 400 mesh, Guangxi Longguang; Maleic anhydride-grafted PE: IM800, WannaP; Lubricant: Crodamide 212-BE-(HU), Shanghai Shixiang; Black Pearls® 800, Cabot.

[0021] Molding method for PIN connectors used for airtightness testing: Plastic particles prepared using the component materials of the examples and comparative examples are integrally molded using an insert injection molding process. The structure of the PIN connector at the PIN pin position is as follows. Figure 1 As shown, other parts are not involved in airtightness testing and are therefore not shown.

[0022] The performance testing methods are as follows: The content of terminal amino groups in PA66 resin (mmol / kg): Acid-base titration method: 1) Weigh approximately 1 g (W) of sample and dissolve it in 30 ml of phenol-anhydrous ethanol solution; 2) Add 3 drops of thymol blue indicator, then titrate with 0.01 mol / L HCl solution. The titration endpoint is reached when the solution changes from pale yellow to pink. Record the volume of titrant used, V1; 3) Prepare a blank sample without adding any sample and record the volume of titrant used, V0; 4) Calculate the content of terminal amino groups using the following formula: Terminal amino group content (mmol / kg) = (V1-V0)×N×1000 / W Where N: molar concentration of the titrant; W: sample weight / g.

[0023] Air tightness (mL / min): Ten PIN connector samples were selected for air tightness testing. The samples were placed on a fixed fixture, the end with the PIN pins was sealed, and a gas pressure of 1 bar was introduced and maintained for 30 seconds. The gas leakage was detected using an SLF flow air tightness tester. Air tightness judgment rules: a value less than 1 is acceptable, a value greater than 1 indicates leakage, and 999 indicates a large leak.

[0024] Table 1 shows the components and performance test data for the examples and comparative examples. The parts in the components are by weight. It should be noted that the parts of lubricant and black powder are consistent in both the examples and comparative examples, which are 0.5 parts and 0.3 parts respectively, and are not listed in the table.

[0025] Table 1 shows the component and performance test data of the formulations in the examples and comparative examples.

[0026] The data in the table show that in Examples 1-5, PA66 resin components with a terminal amino content of 110-140 mmol / kg were used, and the airtightness of all 10 samples in each example was qualified. In Comparative Example 1, PA66 resin C with a terminal amino content of 85% was used, and the airtightness failed to meet the standard, with all samples experiencing major leaks. In Comparative Example 2, PA66 resin D with a terminal amino content of 180% was used. The material had excessive fluidity, which easily trapped air during the molding process, causing scorching and resulting in poor PIN pin coverage. This led to unstable airtightness, with 5 out of 10 samples experiencing major leaks, and most failing to meet the airtightness requirements.

[0027] Compared to Example 3, Comparative Example 3, which added the polar modifying agent maleic anhydride grafted onto PE, actually exhibited worse airtightness. A possible reason is that some maleic anhydride groups undergo an "amine hydrolysis" reaction with the amino group during extrusion and injection molding, generating maleimide ammonium acid (an intermediate) or further closing the ring to form maleimide. This "consumes" the amino group, reducing the probability of the amino group forming a coordinate bond with the metal, thus leading to a decrease in airtightness.

[0028] It should be noted that the components used in the above embodiments can be selected or replaced by those skilled in the art according to their needs, without exceeding the scope of protection of this application.

Claims

1. A polyamide composite, characterized in that: By weight parts, including the following components: PA66 resin 65~85 parts, Reinforcing filler 10~35 parts, Lubricant 0.5~2 parts, Other additives 0~5 parts, The end amino content of the PA66 resin is 110~140 mmol / kg.

2. The polyamide composite according to claim 1, characterized in that, The reinforcing filler includes: glass fiber 10~35 parts, mineral powder 0~30 parts.

3. The polyamide composite according to claim 2, characterized in that, The glass fiber is silane coupling agent treated long glass fiber or short glass fiber.

4. The polyamide composite of claim 2, wherein, The mineral powder is one or several of glass powder, glass beads, talc, kaolin, wollastonite, mica, montmorillonite, calcium carbonate, alumina, magnesia, magnesium carbonate, barium sulfate, calcium silicate, magnesium silicate, aluminum silicate.

5. The polyamide composite of claim 1, wherein, The lubricant is one or several of fatty acid and its ester, fatty acid amide, metal soap.

6. The polyamide composite of claim 1, wherein, The other additives are one or several of antioxidant, colorant, release agent, anti-glass fiber exposure agent, toughening agent.

7. The method of producing a polyamide composite according to claim 2, characterized in that, Including the following steps: after mixing other components except glass fiber, the main feeding is added to the screw extruder in the way of glass fiber side feeding, and the polyamide composite material is obtained by melting extrusion and granulation, wherein the screw extruder temperature is 270~320℃, and the rotating speed is 300~400 rpm.

8. Use of a polyamide composite according to any one of claims 1 to 6 for improving the air tightness of a pin connector, characterized in that The polyamide composite material is used as the PIN pin connector shell raw material, and is integrally formed with the PIN pin through the insert injection molding process.

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