A method for non-direct contact ultrasonic implantation and welding of plastic

Abstract

A non-direct contact ultrasonic implantation and welding method for plastics belongs to the field of material joining. The method involves: partially clamping a metal implant between the welding areas of two thermoplastic sheets, and continuously applying a pressure of 0.4–0.6 MPa to the surface of the welding area; inserting ultrasonic welding heads with a pressure of 0.2–0.6 MPa on one side of the metal implant not clamped between the welding areas, and placing a pad on the other side; placing temperature measuring devices around the ultrasonic welding heads and the weld to measure heat, and performing ultrasonic welding to obtain a thermoplastic welded joint. This method utilizes the friction between the metal implant and the ultrasonic welding heads on both sides to heat the metal implant. The metal implant acts as a heat transfer medium to achieve interface temperature transfer, effectively providing the heat required for the welding process. When the temperature at the welding interface reaches the melting point of the plastic, the thermoplastic connection is completed under pressure.

Description

Technical Field

[0001] This invention belongs to the field of material joining technology, specifically relating to a method for ultrasonic implantation and welding of plastics using a non-direct contact method. Background Technology

[0002] Welding technology is widely used in the field of metallic materials and has begun to be gradually applied in the field of polymer materials in recent years. However, the application of welding technology to plastic materials is an emerging field. Many traditional joining techniques are being improved for joining plastic materials, and welding technology is a major category among them. Plastic welding technology is mainly used in the joining of thermoplastic plastic structures.

[0003] Thermoplastics are increasingly attracting the attention of researchers in the automotive and aerospace industries due to their superior mechanical properties, good weldability, short production cycles, and potential recyclability. The application rate of thermoplastics has, to some extent, become an indicator of structural progress. Therefore, accelerating research on thermoplastics and improving their assembly techniques are key to advancing the lightweighting of thermoplastics. Ultrasonic welding, as a general welding technology for assembling thermoplastic structures, uses high-frequency, low-amplitude vibrations to provide heat to the welding interface while applying pressure through the welding head. Furthermore, ultrasonic welding is well-suited for automating the connection of long seams (>10 cm) and is widely used in the manufacture and joining of plastic materials such as carbon fiber reinforced polyphenylene sulfide (CF / PPS) composites, carbon fiber reinforced polyether ketone ketone composites, carbon fiber reinforced polyamide 66 (CF / PA66) composites, and polypropylene (PP).

[0004] Chinese invention patent (authorization announcement number: CN108908945B) invented an ultrasonic welding method for multi-layer plastic sheets, but this method is only suitable for thin plastic sheets (single layer less than 1 mm) and will produce pits in the welding area, which will seriously affect the performance of the welded parts.

[0005] Due to the vibration and pressure of traditional ultrasonic welding heads, irreversible damage often occurs at the stress points of the upper substrate. Similar studies have found that indentations formed on the surface of the upper workpiece directly affect the continuity of the laminate and the mechanical properties of the joint, which seems to be an unavoidable problem. Therefore, the development of non-direct contact welding methods has become an inevitable way to avoid substrate damage. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a non-direct contact ultrasonic implantation welding method for plastics. This method utilizes the friction between the metal implant and the ultrasonic welding heads on both sides to heat the metal implant. The metal implant acts as a heat transfer medium, achieving interface temperature transfer and effectively providing the heat required for the welding process. When the temperature at the welding interface reaches the melting point of the plastic, the thermoplastic connection is completed under pressure.

[0007] The present invention provides a method for non-direct contact ultrasonic implantation and welding of plastic, comprising the following steps:

[0008] S1: The metal implant is partially clamped between the welding areas of two thermoplastic sheets, and a pressure of 0.4 to 0.6 MPa is continuously applied to the surface of the welding area; wherein, the metal implant is made of metal mesh;

[0009] S2: An ultrasonic welding head with a pressure of 0.2 to 0.6 MPa is added to one side of the metal inlet body that is not clamped between the welding areas, and a pad is placed on the other side;

[0010] S3: Temperature measuring devices are placed around the ultrasonic welding head and the weld to measure the heat, and ultrasonic welding is performed to obtain a thermoplastic welded joint; wherein, the amplitude and time of ultrasonic welding are determined according to the melting point of the thermoplastic sheet, and the ultrasonic welding frequency used is 15kHz.

[0011] In S1, the thermoplastic is selected from one of polypropylene (PP), polyphenylene sulfide (PPS), polyaryletherketone (PAEK), polyamide 66 (PA66), polyetherimide (PEI), polyvinyl chloride (PVC), and polyethylene (PE), wherein the thickness of the thermoplastic sheet is 3-6 mm.

[0012] In S1, the metal mesh is selected from one of copper mesh, stainless steel mesh, iron-chromium-aluminum alloy mesh, and nickel-copper alloy mesh, preferably copper mesh.

[0013] In S1, the metal mesh is a woven mesh with an aperture of 30–500 μm and a wire diameter of 30–200 μm.

[0014] In S2, the ultrasonic welding head vibrates horizontally.

[0015] In S3, more preferably, the ultrasonic welding amplitude is 5-40 μm and the ultrasonic welding time is 3-15 s.

[0016] In S3, the temperature measuring device is preferably a thermocouple.

[0017] In S3, the method for determining the ultrasonic welding amplitude and ultrasonic welding time based on the melting point of the thermoplastic sheet is as follows: the temperature around the weld is measured by a temperature measuring device. When the temperature measuring device detects that the temperature of the metal implant around the weld has reached the melting point of the thermoplastic sheet, the ultrasonic welding amplitude and ultrasonic welding time are determined. If the temperature measuring device detects that the temperature of the metal implant has not reached the melting point of the thermoplastic sheet, the ultrasonic welding amplitude and / or ultrasonic welding time are increased. By monitoring with a temperature measuring device set in the ultrasonic welding head, the temperature is prevented from being too high (exceeding the thermal decomposition temperature of the thermoplastic) and causing the plastic to decompose.

[0018] In S3, the amplitude determines the intensity of friction. The amplitude affects the cleanliness of the plastic surface, the plastic flow state, and the heating temperature. Because different thermoplastics have different physical properties, the heating rate of the thermoplastic surface varies under ultrasonic waves of different amplitudes. If the amplitude is too small, it is difficult for the thermoplastic to reach its melting temperature in the welding area. Therefore, for each polymer material, there should be an optimal range of welding amplitude, and appropriately increasing the amplitude is beneficial to improving the welding quality.

[0019] In S3, welding time refers to the duration of ultrasonic wave application during the welding process. Insufficient welding time results in insufficient energy generation, preventing the formation of a high-quality weld joint. As welding time increases, the welding interface absorbs more energy, the weld joint temperature rises continuously, the welding interface area increases, and the weld joint strength improves. However, longer welding time is not always better; excessively long welding times can cause thermal decomposition, discoloration, carbonization, and overflow of materials within the welding area, leading to damage.

[0020] The present invention discloses a non-direct contact ultrasonic implantation welding method for plastic, wherein the welded thermoplastic joint has an interfacial tensile strength of 2-50 MPa.

[0021] The present invention provides a non-direct contact ultrasonic implantation welding method for plastics, the advantages of which are as follows:

[0022] 1) Advanced ultrasonic welding equipment can fully control and monitor the welding process and is ideal for automating the connection of long seams (>10 cm).

[0023] 2) The high efficiency of ultrasonic welding technology makes it more productive and less expensive than other joining technologies, and it does not require a special circulation system to remove smoke or cool down.

[0024] 3) The indentations formed on the workpiece surface by traditional ultrasonic welding directly affect the continuity of the laminate and the mechanical properties of the joint, while the non-direct contact ultrasonic implantation welding method can avoid damage to the substrate.

[0025] 4) Indirect contact ultrasonic implantation welding utilizes the friction between the metal implant and the ultrasonic welding head to heat the metal implant, making it a heating medium to achieve interface temperature transfer. This can effectively provide the heat required for the welding process and complete the thermoplastic connection under pressure. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of ultrasonic implantation welding using a non-direct contact method; in the diagram, 1-ultrasonic welding head; 2-metal implant; 3-first thermoplastic; 4-second thermoplastic; 5-clamping device; 6-thermocouple; 7-pad.

[0027] Figure 2 The images show the weld microstructure of polypropylene plastic joints under different ultrasonic welding times: (a) ultrasonic welding time is 3s; (b) ultrasonic welding time is 5s; (c) ultrasonic welding time is 10s. Detailed Implementation

[0028] The specific embodiments of the present invention will be further described below in conjunction with the technical solution.

[0029] In the following embodiments, for different thermoplastic resins and different metal implants, under different welding parameters, the metal implant is heated by friction between the metal implant and the ultrasonic welding heads on both sides, and the metal implant is used as a heat transfer medium to achieve interface temperature transfer. When the temperature at the welding interface reaches the melting point of the thermoplastic, the connection of the thermoplastic is completed under pressure.

[0030] Example 1

[0031] A method for non-direct contact ultrasonic implantation welding of plastics is shown in the schematic diagram below. Figure 1 Specifically, it includes the following steps:

[0032] (1) A portion of a metal implant 2 (a copper mesh in this embodiment) is inserted between a first thermoplastic plastic 3 sheet and a second thermoplastic plastic 4 sheet (both the first thermoplastic plastic 3 sheet and the second thermoplastic plastic 4 sheet in this embodiment are polypropylene (PP) plastic sheets) with a thickness of 3 mm, and a pressure of 0.4 MPa is applied to the surface of the welding area using a clamping device 5, wherein the wire diameter is 35 μm and the aperture is 70 μm.

[0033] (2) An ultrasonic welding head 1 with a pressure of 0.2 MPa is added above both sides of the copper mesh that is not implanted between the polypropylene (PP) plastic sheets, and a pad 7 is placed below it.

[0034] (3) Place thermocouples 6 around the ultrasonic welding head and the weld to measure the heat. Adjust the welding parameters according to the difference between the temperature around the weld and the melting point of the polypropylene (PP) plastic sheet. Observe the temperature at the ultrasonic welding head at any time. When the temperature around the weld is comparable to the melting point of the polypropylene (PP) plastic sheet, perform ultrasonic welding so that the highest temperature in the welding area reaches 184℃. The ultrasonic welding amplitude is 5.2μm, the ultrasonic welding time is 10s, and the welding frequency is 15kHz.

[0035] (4) Observe the weld microstructure using an electron microscope. Figure 2 (c) As can be seen from the figure, there are no pits on the surface, and the implant and molten polymer have been perfectly combined in most areas of the joint center. The universal tensile test was performed on the weldment, and the results showed that the resin and copper mesh in the joint area were well bonded, the weld was strong, and the tensile strength could reach 7.6 MPa.

[0036] Furthermore, based on the change in ultrasonic welding time, ( Figure 2 (ac)), the joint center starts with a large amount of unfilled polymer area, where the polymer is only bonded at the joint edge, then the area of ​​the unwelded area in the center decreases, the area of ​​the edge bonding area increases, and finally the unwelded area almost disappears, and the area is perfectly bonded.

[0037] Example 2

[0038] A method for non-direct contact ultrasonic implantation and welding of plastics specifically includes the following steps:

[0039] (1) A portion of an iron-chromium-aluminum alloy mesh is inserted between polyethylene (PE) plastic sheets with a thickness of 3 mm, and a pressure of 0.4 MPa is applied to the surface of the welding area using an upper clamping device, wherein the wire diameter is 150 μm and the aperture is 100 μm.

[0040] (2) Add an ultrasonic welding head with a pressure of 0.2MPa above both sides of the iron-chromium-aluminum alloy mesh that is not embedded between the polyethylene (PE) plastic sheets, and place a pad below.

[0041] (3) Place thermocouples around the ultrasonic welding head and the weld to measure the heat. Adjust the welding parameters according to the difference between the temperature around the weld and the melting point of the polyethylene (PE) plastic sheet. Observe the temperature at the ultrasonic welding head at any time. When the temperature around the weld is comparable to the melting point of the polyethylene (PE) plastic sheet, perform ultrasonic welding so that the highest temperature in the welding area reaches 125℃. The ultrasonic welding amplitude is 5.2μm, the ultrasonic welding time is 8s, and the welding frequency is 15kHz.

[0042] (4) The weld microstructure was observed using an electron microscope, and the weld was subjected to a tensile test using a universal tensile tester. The results showed that the resin and iron-chromium-aluminum alloy mesh in the joint area were well bonded, the weld was strong, and the tensile strength could reach 9.2 MPa.

[0043] Example 3

[0044] A method for non-direct contact ultrasonic implantation and welding of plastics specifically includes the following steps:

[0045] (1) A portion of stainless steel mesh is embedded between polyvinyl chloride (PVC) plastic sheets with a thickness of 3 mm, and a pressure of 0.4 MPa is applied to the surface of the welding area using an upper clamping device, wherein the wire diameter is 80 μm and the aperture is 400 μm.

[0046] (2) Add ultrasonic welding heads with a pressure of 0.4 MPa above both sides of the stainless steel mesh that is not embedded between the polyvinyl chloride (PVC) plastic sheets, and place pads below.

[0047] (3) Place thermocouples around the ultrasonic welding head and the weld to measure the heat. Adjust the welding parameters according to the difference between the temperature around the weld and the melting point of the polyvinyl chloride (PVC) plastic sheet. Observe the temperature at the ultrasonic welding head at any time. When the temperature around the weld is comparable to the melting point of the polyvinyl chloride (PVC) plastic sheet, perform ultrasonic welding so that the highest temperature in the welding area reaches 210℃. The ultrasonic welding amplitude is 10μm, the ultrasonic welding time is 10s, and the welding frequency is 15kHz.

[0048] (4) The weld microstructure was observed using an electron microscope, and the weld was subjected to a tensile test using a universal tensile tester. The results showed that the resin and stainless steel mesh in the joint area were well bonded, the weld was strong, and the tensile strength could reach 9.8 MPa.

[0049] Example 4

[0050] A method for non-direct contact ultrasonic implantation and welding of plastics specifically includes the following steps:

[0051] (1) Insert the middle part of the nickel-copper mesh between polyetherimide (PEI) plastic sheets with a thickness of 4 mm, and apply a pressure of 0.4 MPa to the surface of the welding area using the upper clamping device, wherein the wire diameter is 200 μm and the aperture is 500 μm.

[0052] (2) An ultrasonic welding head with a pressure of 0.3 MPa is added above both sides of the nickel-copper mesh that is not embedded between the polyetherimide (PEI) plastic sheets, and a pad is placed below.

[0053] (3) Place thermocouples around the ultrasonic welding head and the weld to measure the heat. Adjust the welding parameters according to the difference between the temperature around the weld and the melting point of the polyetherimide (PEI) plastic sheet. Observe the temperature at the ultrasonic welding head at any time. When the temperature around the weld is comparable to the melting point of the polyetherimide (PEI) plastic sheet, perform ultrasonic welding to make the highest temperature in the welding area reach 220℃. The ultrasonic welding amplitude is 18μm, the ultrasonic welding time is 7s, and the welding frequency is 15kHz.

[0054] (4) The weld microstructure was observed using an electron microscope, and the weld was subjected to a tensile test using a universal tensile tester. The results showed that the resin and nickel-copper mesh in the joint area were well bonded, the weld was strong, and the tensile strength could reach 22.5 MPa.

[0055] Example 5

[0056] A method for non-direct contact ultrasonic implantation and welding of plastics specifically includes the following steps:

[0057] (1) Insert the middle part of the copper mesh between polyamide 66 (PA66) plastic sheets with a thickness of 4 mm, and apply a pressure of 0.4 MPa to the surface of the welding area using the upper clamping device, wherein the wire diameter is 35 μm and the aperture is 70 μm.

[0058] (2) Add ultrasonic welding heads with a pressure of 0.3MPa above both sides of the copper mesh that is not embedded between the polyamide 66 (PA66) plastic sheets, and place pads below.

[0059] (3) Place thermocouples around the ultrasonic welding head and the weld to measure the heat. Adjust the welding parameters according to the difference between the temperature around the weld and the melting point of the polyamide 66 (PA66) plastic sheet. Observe the temperature at the ultrasonic welding head at any time. When the temperature around the weld is comparable to the melting point of the polyamide 66 (PA66) plastic sheet, perform ultrasonic welding to make the highest temperature in the welding area reach 260℃. The ultrasonic welding amplitude is 20μm, the ultrasonic welding time is 10s, and the welding frequency is 15kHz.

[0060] (4) The weld microstructure was observed using an electron microscope, and the weld was subjected to a tensile test using a universal tensile tester. The results showed that the resin and copper mesh in the joint area were well bonded, the weld was strong, and the tensile strength could reach 28.3 MPa.

[0061] Example 6

[0062] A method for non-direct contact ultrasonic implantation and welding of plastics specifically includes the following steps:

[0063] (1) A copper mesh is inserted between polyphenylene sulfide (PPS) plastic sheets with a thickness of 6 mm, and a pressure of 0.4 MPa is applied to the surface of the welding area using an upper clamping device, wherein the wire diameter is 35 μm and the aperture is 70 μm.

[0064] (2) Add ultrasonic welding heads with a pressure of 0.3 MPa above both sides of the copper mesh that is not embedded between the polyphenylene sulfide (PPS) plastic sheets, and place pads below.

[0065] (3) Place thermocouples around the ultrasonic welding head and the weld to measure the heat. Adjust the welding parameters according to the difference between the temperature around the weld and the melting point of the polyphenylene sulfide (PPS) plastic sheet. Observe the temperature at the ultrasonic welding head at any time. When the temperature around the weld is comparable to the melting point of the polyphenylene sulfide (PPS) plastic sheet, perform ultrasonic welding so that the highest temperature in the welding area reaches 305℃. The ultrasonic welding amplitude is 31μm, the ultrasonic welding time is 12s, and the welding frequency is 15kHz.

[0066] (4) The weld microstructure was observed using an electron microscope, and the weld was subjected to a tensile test using a universal tensile tester. The results showed that the resin and copper mesh in the joint area were well bonded, the weld was strong, and the tensile strength could reach 35.2 MPa.

[0067] Example 7

[0068] A method for non-direct contact ultrasonic implantation and welding of plastics specifically includes the following steps:

[0069] (1) A copper mesh is inserted between polyaryletherketone (PAEK) plastic sheets with a thickness of 6 mm, and a pressure of 0.4 MPa is applied to the surface of the welding area using an upper clamping device, wherein the wire diameter is 35 μm and the aperture is 70 μm.

[0070] (2) Add ultrasonic welding heads with a pressure of 0.4 MPa above both sides of the copper mesh that is not embedded between the polyaryletherketone (PAEK) plastic sheets, and place pads below.

[0071] (3) Place thermocouples around the ultrasonic welding head and the weld to measure the heat. Adjust the welding parameters according to the difference between the temperature around the weld and the melting point of the polyaryletherketone (PAEK) plastic sheet. Observe the temperature at the ultrasonic welding head at any time. When the temperature around the weld is comparable to the melting point of the polyaryletherketone (PAEK) plastic sheet, perform ultrasonic welding to make the highest temperature in the welding area reach 350℃. The ultrasonic welding amplitude is 40μm, the ultrasonic welding time is 15s, and the welding frequency is 15kHz.

[0072] (4) The weld microstructure was observed using an electron microscope, and the weld was subjected to a tensile test using a universal tensile tester. The results showed that the resin and copper mesh in the joint area were well bonded, the weld was strong, and the tensile strength could reach 46.7 MPa.

[0073] Comparative Example 1

[0074] Similar to Example 1, the difference is that the ultrasonic welding time is 3 seconds, the heat input is insufficient, and the microstructure shows that the resin only adheres to the joint edge, with a large number of unfilled resin areas.

[0075] Comparative Example 2

[0076] Similar to Example 1, except that the ultrasonic welding time is 5 seconds, the edge bonding area is increased, and the unfilled resin area is reduced.

[0077] Comparative Example 3

[0078] Similar to Example 2, the difference is that the ultrasonic welding head acts directly on the upper part of the iron-chromium-aluminum alloy mesh between the polyethylene (PE) plastic sheets and the pressure device is located on the same vertical axis. In this case, the pressure and vibration of the ultrasonic welding head will cause indentation damage to the upper substrate of the polyethylene (PE) and affect the mechanical properties of the joint.

[0079] Comparative Example 4

[0080] Similar to Example 1, the difference is that the ultrasonic welding head is set at one end of the copper mesh, and the other end of the copper mesh is clamped between two polypropylene (PP) plastic sheets. Due to the welding effect of the ultrasonic welding head, the heat is conducted only from one end, and the heat is not evenly distributed, which leads to over-welding or under-welding at one end, resulting in a decrease in the mechanical properties of the joint.

[0081] The above embodiments are merely preferred embodiments of the technical solution of the present invention and do not limit the present invention.

Claims

1. A method of ultrasonic implant welding of plastics by non-direct contact, characterized in that, The method comprises the following steps: S1: locally clamping the metal implant between the welding areas of two thermoplastic plastic plates, and continuously applying a pressure of 0.4-0.6 MPa to the surface of the welding area; wherein the metal implant is a metal mesh; S2: adding an ultrasonic welding head with a pressure of 0.2-0.6 MPa to one side of the two ends of the metal implant not clamped between the welding areas, and placing a pad on the other side; S3: placing a temperature measuring device around the ultrasonic welding head and the weld to measure the temperature, and performing ultrasonic welding to obtain a thermoplastic plastic welded joint; wherein the amplitude and ultrasonic welding time of ultrasonic welding are determined according to the melting point of the thermoplastic plastic plate.

2. The method of non-contact method ultrasonic implant welding plastic according to claim 1, characterized in that, In the S1, the thermoplastic plastic is selected from one of polypropylene, polyphenylene sulfide, polyaryletherketone, polyamide 66, polyetherimide, polyvinyl chloride, and polyethylene.

3. The method of non-contact method ultrasonic implant welding plastic according to claim 1, characterized in that, The thickness of the thermoplastic plastic plate is 3-6 mm.

4. The method of non-contact method ultrasonic implant welding plastic according to claim 1, characterized in that, In the S1, the metal mesh is selected from one of copper mesh, stainless steel mesh, iron-chromium-aluminum alloy mesh, and nickel-copper alloy mesh.

5. The method of non-contact method ultrasonic implant welding plastic according to claim 1, characterized in that, In the S1, the metal mesh is a woven mesh with a pore size of 30-500 μm and a wire diameter of 30-200 μm.

6. The method of non-contact method ultrasonic implant welding plastic according to claim 1, characterized in that, In the S2, the vibration direction of the ultrasonic welding head is horizontal vibration.

7. The method of non-contact method ultrasonic implant welding plastic according to claim 1, characterized in that, In the S3, the welding frequency of the ultrasonic welding is 15 kHz, the amplitude of the ultrasonic welding is 5-40 μm, and the ultrasonic welding time is 3-15 s.

8. The method of non-contact method ultrasonic implant welding plastic according to claim 1, characterized in that, In the S3, the temperature measuring device is a thermocouple.

9. The method of non-contact method ultrasonic implant welding plastic according to claim 1, characterized in that, In the S3, the method for determining the amplitude and ultrasonic welding time of ultrasonic welding according to the melting point of the thermoplastic plastic plate is: measuring the temperature around the weld through the temperature measuring device, when the temperature measuring device detects that the temperature of the metal implant around the weld reaches the melting point of the thermoplastic plastic plate, the amplitude and ultrasonic welding time of ultrasonic welding are determined, if the temperature of the metal implant detected by the temperature measuring device does not reach the melting point of the thermoplastic plastic plate, the amplitude of ultrasonic welding is increased and / or the ultrasonic welding time is increased, and the temperature measuring device arranged on the ultrasonic welding head is monitored to avoid the temperature exceeding the thermal decomposition temperature of the thermoplastic plastic, resulting in decomposition of the plastic.

10. The method of non-contact ultrasonic implant welding of plastics as claimed in any one of claims 1 to 9, wherein, The non-direct contact ultrasonic implant welding plastic method is used to weld the thermoplastic plastic welded joint, and the interfacial tensile strength is 2-50 MPa.

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