A method for improving the strength of ultrasonic welding joints of polymer plates without energy-conducting ribs

Abstract

The present invention discloses a method for improving the strength and stability of ultrasonic welding joints of polymer sheets without energy conducting ribs. Before ultrasonic welding, a small amount of layered inorganic filler (molybdenum disulfide, calcium carbonate, hydroxyapatite, etc.) is added to the polymer sheet without energy conducting ribs (such as carbon fiber reinforced nylon 66 (CF / PA66)), and the thermal stability of the polymer sheet is improved by utilizing the fixing effect of the intercalation structure on the polymer chain. After such treatment, ultrasonic welding is performed, and the sheet is not prone to obvious thermal decomposition, which can avoid the generation of large-area pores, which is beneficial to improving the strength and stability of the joint. Thus, the technical problem of thermal decomposition pore defects caused by the welding energy being easily dissipated inside the sheet in ultrasonic welding of polymer sheets without energy conducting ribs is solved. This method provides theoretical and technical support for the "energy conducting rib-free" ultrasonic welding of polymer sheets, and is also expected to further promote the process of "plastic replacing steel" in automobiles.

Description

Technical Field

[0001] The invention relates to a polymer plate without energy conducting ribs for ultrasonic welding, and in particular to a method for improving the strength of ultrasonic welding joints of a polymer plate without energy conducting ribs. Background Art

[0002] Lightweighting of automobiles is an urgent need of the national energy conservation and emission reduction strategy. For every 10% reduction in automobile weight, fuel consumption and carbon emissions can be reduced by 8%. Polymer materials are low in cost, light in weight, and have good processing performance. They play an increasingly important role in the automotive industry. "Replacing steel with plastic" has become the dominant direction of future automotive development. Ultrasonic welding of polymer sheets without energy-conducting ribs is widely used due to its high efficiency and easy automation. However, it is usually necessary to design and process energy-conducting ribs at the welded parts. The introduction of energy-conducting ribs has problems such as high cost and susceptibility to workpiece size and position restrictions.

[0003] At present, the main problem of ultrasonic welding of polymer sheets without energy-conducting ribs (non-puncture welding, puncture welding can cause surface damage, affecting appearance and performance) is the low joint strength. Wang Xiaolin and other scholars (Wang Xiaolin. Study on Ultrasonic Heat-Deformation Law and Welding Process of Polyetheretherketone [D]. Harbin: Harbin Institute of Technology, 2007.) found that the main reason for this problem is that without energy-conducting ribs to guide and distribute energy on the welding interface, the welding energy is easily dissipated inside the sheet. Under the premise of ensuring the welding area, the joint material is prone to thermal decomposition, resulting in thermal decomposition pore defects, and the joint strength is low, which is only about 50% of the joint with energy-conducting ribs; while reducing the welding energy to avoid pore defects will lead to a decrease in welding area and joint strength.

[0004] In order to solve the problem of low strength of ultrasonic welding joints of polymer plates without energy-conducting ribs, scholars at home and abroad have proposed a variety of different solutions, which can be summarized into the following three aspects:

[0005] (1) Improve joint strength through preheating process. Preheating the plate before welding can not only reduce energy input, but also affect the energy distribution of the weld surface. Wang et al. preheated CF / PA66 plates before welding. The results showed that the welding area, bonding degree and tensile strength of the joint increased with the increase of preheating temperature. This is mainly attributed to the fact that preheating improves the utilization rate of energy on the welding surface, softens the material, concentrates the welding pressure in the center of the overlap area, and reduces the melting area of ​​the plate edge material (within the overlap area). Luo et al. preheated polyetheretherketone (PMMA) without energy-conducting ribs before welding and found that preheating improved the welding surface fusion efficiency and joint strength. Yan Jiuchun's research group at Harbin Institute of Technology proposed a PMMA preheating ultrasonic welding process (Wang Xiaolin, Li Mingyu, Yan Jiuchun, et al. Preheating temperature of polyetheretherketone preheating ultrasonic welding process. Welding, 2011, 10: 52-55+72.). The formation of dense interface holes (porous defects) can be avoided by using a suitable preheating temperature (<300°C), and the joint strength can be increased by more than 20%. The tensile strength of the joint is indeed enhanced compared to the unpreheated joint, but the fatigue strength is also significantly improved. At the same time, pores and joint embrittlement limit the further improvement of the strength of the preheated ultrasonic joint.

[0006] (2) Improve joint strength through secondary welding. The secondary welding process mainly improves joint strength by increasing the welding area. Lu Lei et al. repaired the internal defects of the welded joint by re-welding the welded joint and found that repair welding can improve the stability of joint strength, but the improvement of joint strength is limited. At the same time, the study also found that when ultrasonic waves are applied for the second time, as long as the temperature of the plate is in the appropriate temperature range (95-145°C), its tensile strength does not change much, and the fatigue strength is increased by 18%. The improvement mechanism is similar to that of preheating treatment.

[0007] (3) Adding a "sandwich" between the plates to improve joint performance. In order to solve the problem of concentrated welding energy distribution caused by the lack of energy conductors, many scholars have added a "sandwich" between the upper and lower plates to act as energy conductors to change the energy distribution during welding. Villegas et al. added PEI sheets of different thicknesses when ultrasonically welding carbon fiber reinforced polyetherimide (CF / PEI) plates. The results showed that when the thickness of the PEI sheet was less than 0.06 mm, the joint would decompose the material due to excessive heat concentration, resulting in porous defects. For thicker sheets (0.25 mm and 0.5 mm), the PEI "sandwich" on the welding surface melted before the substrate, and the weld formation process was the melting, spreading, and solidification process of the sandwich material. The presence of the sandwich changed the temperature distribution of the welding surface, reduced the decomposition of the material, and increased the strength of the joint by 16%. Goto et al. placed a 0.3mm thick "PA6 interlayer" between the sheets when ultrasonic welding CF / PA66 without energy-conducting ribs. For twill-woven laminated CF / PA66 sheets, the presence of the interlayer improved the welding efficiency and increased the joint welding area, and the joint strength increased by 26%. However, for orthogonal laminated sheets, the interlayer reduced the welding area and had little effect on the joint strength. As the welding energy increased further, the joint strength decreased due to the thermal decomposition of the sheet.

[0008] In summary, although preheat treatment, secondary welding and adding "interlayer" can reduce the decomposition of materials to a certain extent and inhibit the generation of thermal decomposition pore defects, the effect is not good. Therefore, the improvement of joint strength is limited. At the same time, additional process steps are introduced, which reduces welding efficiency. Summary of the invention

[0009] In view of the technical problem that the welding energy in the existing ultrasonic welding of polymer plates without energy conducting ribs is easily dissipated inside the plate and causes thermal decomposition of the material, the present invention provides a method for improving the strength of ultrasonic welded joints of polymer plates without energy conducting ribs. A small amount of layered inorganic filler is added to the polymer plate without energy conducting ribs to form an intercalated structure with the polymer chain, thereby improving the thermal stability of the polymer plate and achieving the effect of inhibiting the thermal decomposition of the joint to improve the joint strength.

[0010] The technical solution of the present invention is:

[0011] A method for improving the strength of ultrasonic welding joints of polymer plates without energy conducting ribs includes adding layered inorganic fillers to the polymer plates without energy conducting ribs before ultrasonic welding.

[0012] Furthermore, the layered inorganic filler is molybdenum disulfide (MoS 2 ), calcium carbonate (CaCO 3 ), hydroxyapatite (Ca 10 (PO 4 )6 (OH) 2 ), the layered inorganic filler is preferably MoS 2 , MoS 2 It is a two-dimensional layered structure, which is conducive to the insertion of polymer chains to form an intercalated structure. At the same time, the barrier effect brought by its two-dimensional nanostructure is particularly effective in improving the thermal stability of polymer materials.

[0013] Furthermore, the MoS 2 The particle size is 0.8-1.0μm.

[0014] Furthermore, the amount of the inorganic filler is 0.5%-1.5% of the mass of the polymer sheet without energy conducting ribs, preferably 0.8%-1.2%, and more preferably 0.8%-1.0%.

[0015] Furthermore, the polymer sheet without energy conducting ribs is a carbon fiber reinforced nylon 66 composite material (CF / PA66), a carbon fiber reinforced polyetherimide (CF / PEI), a polyetheretherketone (PMMA) without energy conducting ribs, etc., preferably CF / PA66.

[0016] Furthermore, the method of adding inorganic filler to the polymer sheet without energy conducting ribs comprises the following steps:

[0017] (1) Mixing, by mass percentage, 98.5% to 99.5% of a polymer sheet without energy conducting ribs and 0.5% to 1.5% of an inorganic filler to obtain a mixture;

[0018] (2) The mixture is granulated, dried and injection molded to obtain a welding plate.

[0019] Furthermore, in step (1), when the polymer sheet without energy conducting ribs is a composite material, the raw materials before compounding are added. For example, when the polymer sheet without energy conducting ribs is CF / PA66, carbon fiber CF, PA66 particles and MoS 2 The powders are mixed in mass percentages of 25%-32%, 67.5%-74.5% and 0.5%-1.5% (preferably 28%-30%, 68.8%-71.2% and 0.8%-1.2%, more preferably 28%-30%, 69%-71% and 0.8%-1.0%).

[0020] Furthermore, the mass percentage of the polymer sheet without energy conducting ribs and the inorganic filler is preferably 98.8%-99.2% of the polymer sheet without energy conducting ribs and 0.8%-1.2% of the inorganic filler, and more preferably 99%-99.2% of the polymer sheet without energy conducting ribs and 0.8%-1.0% of the inorganic filler.

[0021] When ultrasonic welding is performed on the above-mentioned welding plate, the method adopted is overlapping, the welding power is 2400-2800w (preferably 2600w), the welding pressure is 500-700N (preferably 600N), and the welding time is 1.7s~2.5s. After welding is completed, the overlapping area forms a permanently connected weld.

[0022] Inorganic fillers are layered MoS 2 The effect is better, because MoS 2 The monolayer thickness and thin-sheet structure can significantly improve the thermal stability of polymer materials. 2 When dispersed in a polymer matrix, some polymer / monomer molecules can be inserted into the 2D MoS 2 The interlayer structure is formed. During the thermal decomposition process, this structure can effectively hinder the thermal movement of the polymer chain, thereby effectively delaying the thermal decomposition of the polymer, thereby improving the thermal stability of the polymer sheet during welding.

[0023] Compared with other layered inorganic fillers CaCO 3 , Ca 10 (PO 4 ) 6 (OH) 2 Compared with MoS 2 The effect of improving the thermal stability of polymer materials is more significant, mainly because MoS 2 The barrier effect brought by the two-dimensional nanostructure is quite obvious, which can inhibit the supply of oxygen from the external environment to the polymer and delay the escape of small gas molecules produced during the degradation of gaseous products. 2 The interfacial interaction with the polymer material hinders the thermal motion of the polymer chain, thereby improving the MoS 2 / Thermal stability of polymer systems.

[0024] MoS 2 Inorganic fillers such as MoS can improve the thermal stability of polymer materials while also changing the structure and mechanical properties of the materials. These factors may affect the structure and morphology of the welded joints. 2 For example, it mainly includes the following two aspects:

[0025] (1) Influence of pore defects: MoS 2On the one hand, it can improve the thermal stability of CF / PA66 and other non-energy conductive polymer sheets, and on the other hand, it affects the elastic modulus, loss modulus, glass transition temperature and thermal conductivity of CF / PA66 and other non-energy conductive polymer sheets. The elastic modulus, loss modulus and glass transition temperature determine the distribution of welding heat, and the thermal conductivity will also cause changes in the temperature field, which synergistically affect the welding temperature field. These two aspects jointly determine the morphology and distribution of pore defects.

[0026] (2) Influence of weld structure: MoS 2 There is interaction with carbon fiber, MoS 2 The morphology, size and addition amount of the MoS2+ will affect the melting, spreading and solidification of the sheet during CF / PA66 ultrasonic welding, thus affecting the MoS2+ content in the weld structure. 2 and orientation and distribution of carbon fibers.

[0027] The beneficial effects of the present invention are:

[0028] MoS 2 It is a layered two-dimensional material. MoS 2 The particles are uniformly added to the polymer material, which can make the polymer chain partially inserted into the layered structure to form an intercalation structure. The intercalation structure can significantly improve the thermal stability of the polymer material and reduce the thermal decomposition rate of the polymer material. Adding a small amount (less than 1.5wt%, such as 1wt%) of two-dimensional MoS 2 Thermoplastic polymer sheets (such as CF / PA66, etc.) with particles are not easy to undergo obvious thermal decomposition during high energy (5-10kJ) ultrasonic welding, which can avoid the generation of large-area thermal decomposition pores and help improve the strength and stability of the joint. Therefore, adding a small amount (less than 1.5wt%) of MoS 2 The particles can significantly improve the weldability of polymer materials, improve the porosity defect problem existing in ultrasonic welding of polymer materials, and significantly improve the strength and stability of the joints.

[0029] The present invention can provide theoretical and technical support for expanding the application of polymer materials in the fields of automobile manufacturing, promote the lightweight process of automobiles, and lay the foundation for the implementation of a series of major national strategies such as "energy conservation and emission reduction". BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 for Figure 1 Add 0.8 wt% MoS to Example 1 2 Cf / PA66 sheet and without MoS addition 2 The morphology of the welded surface of Cf / PA66 sheet, where (a) is without addition and (b) is with addition of 0.8wt% MoS 2 .

[0031] Figure 2 Schematic diagram of overlapping ultrasonic welding.

[0032] Figure 3 This is the microscopic morphology of layered molybdenum disulfide powder.

[0033] Figure 4 This is the morphology and schematic diagram of molybdenum disulfide embedded in CF / PA66. It can be seen from the figure that molybdenum disulfide is a multi-layer structure. When added to CF / PA66, it can allow nylon chains to be embedded in the multi-layer structure to form an intercalated structure, which plays a fixing role and increases the thermal decomposition temperature of the board.

[0034] Figure 5 For Cf / PA66 sheet with 0.8wt% MoS 2 Thermogravimetric experimental curve of Cf / PA66 sheet, Figure 5 It can be seen that adding 0.8wt% MoS 2 The thermal decomposition temperature of the Cf / PA66 sheet increased significantly and the decomposition rate decreased after adding 0.8wt% MoS 2 Can improve the thermal stability of Cf / PA66 sheets. DETAILED DESCRIPTION

[0035] The present invention is further described in detail below with reference to specific embodiments, but the present invention is not limited thereto.

[0036] Example 1

[0037] Adding inorganic filler MoS to CF / PA66 polymer sheet without energy-conducting ribs 2 The method comprises the following steps:

[0038] (1) Carbon fiber CF, PA66 particles and MoS 2 The powders were mixed in mass percentages of 30%, 69.2% and 0.8%;

[0039] (2) Put the mixture into the feed port of the plastic granulator and feed it into the main body through the feed wheel. Inside the main body, PA66 will be melted by high temperature and form a uniform melt while stirring and rotating. It will be extruded from the extrusion port to form small plastic particles. The finished plastic particles will be dried and put into the injection molding machine. The plastic particles will melt under the heat, and the composition will be more uniform under the stirring action of the screw, and then extruded into sheets.

[0040] When welding, the plates are overlapped ( Figure 2 ), the welding power is 2600w, the welding pressure is 600N, the end face of the welding head is a circle with a diameter of 18mm, and the welding time is 1.7s~2.5s. After the welding is completed, the overlapping area forms a permanent connection weld ( Figure 1).

[0041] The stretching is carried out on a universal material testing machine. The stretching direction is vertical stretching. The upper and lower clamps clamp the upper and lower plates respectively. The stretching speed is 2mm / min. The stretching is carried out until the weld is pulled apart or the plate breaks. The peak force of the stretching is the tensile load of the welded joint.

[0042] Without adding MoS 2 The powder plate (other operations are the same) is compared, and the experimental results show that:

[0043] No MoS added 2 The tensile load of the Cf / PA66 plate welded joint is 4.09 kN, while adding 0.8 wt% MoS 2 The tensile load of the Cf / PA66 sheet welded joint can reach 5.85kN, and the tensile load is increased by 43%.

[0044] Figure 1 Add 0.8 wt% MoS to Example 1 2 Cf / PA66 sheet and without MoS addition 2 The morphology of the welded surface of Cf / PA66 sheet, where (a) is without addition and (b) is with addition of 0.8wt% MoS 2 .Depend on Figure 1 It can be seen that without adding MoS 2 The Cf / PA66 sheet is easily decomposed by heat during ultrasonic welding to produce porous structure, while the addition of 0.8wt% MoS 2 The Cf / PA66 sheet welding joint does not show obvious porous structure, so it has higher strength.

[0045] Example 2

[0046] Adding inorganic filler MoS to CF / PA66 polymer sheet without energy-conducting ribs 2 The method comprises the following steps:

[0047] (1) Carbon fiber CF, PA66 particles and MoS 2 The powders were mixed in mass percentages of 29%, 70% and 1.0%;

[0048] (2) Put the mixture into the feed port of the plastic granulator and feed it into the main body through the feed wheel. Inside the main body, PA66 will be melted by high temperature and form a uniform melt while stirring and rotating. It will be extruded from the extrusion port to form small plastic particles. The finished plastic particles will be dried and put into the injection molding machine. The plastic particles will melt under the heat, and the composition will be more uniform under the stirring action of the screw, and then extruded into sheets.

[0049] Example 3

[0050] Adding inorganic filler MoS to CF / PA66 polymer sheet without energy-conducting ribs 2 The method comprises the following steps:

[0051] (1) Carbon fiber CF, PA66 particles and MoS 2 The powders were mixed in mass percentages of 26.8%, 72% and 1.2%;

[0052] (2) Put the mixture into the feed port of the plastic granulator and feed it into the main body through the feed wheel. Inside the main body, PA66 will be melted by high temperature and form a uniform melt while stirring and rotating. It will be extruded from the extrusion port to form small plastic particles. The finished plastic particles will be dried and put into the injection molding machine. The plastic particles will melt under the heat, and the composition will be more uniform under the stirring action of the screw, and then extruded into sheets.

[0053] Example 4

[0054] Adding inorganic filler MoS to CF / PA66 polymer sheet without energy-conducting ribs 2 The method comprises the following steps:

[0055] (1) Carbon fiber CF, PA66 particles and MoS 2 The powders were mixed in mass percentages of 28%, 71% and 1%;

[0056] (2) Put the mixture into the feed port of the plastic granulator and feed it into the main body through the feed wheel. Inside the main body, PA66 will be melted by high temperature and form a uniform melt while stirring and rotating. It will be extruded from the extrusion port to form small plastic particles. The finished plastic particles will be dried and put into the injection molding machine. The plastic particles will melt under the heat, and the composition will be more uniform under the stirring action of the screw, and then extruded into sheets.

[0057] Example 5

[0058] Adding inorganic filler MoS to CF / PA66 polymer sheet without energy-conducting ribs 2 The method comprises the following steps:

[0059] (1) Carbon fiber CF, PA66 particles and MoS 2 The powders were mixed in mass percentages of 25%, 74.5% and 0.5%;

[0060] (2) Put the mixture into the feed port of the plastic granulator and feed it into the main body through the feed wheel. Inside the main body, PA66 will be melted by high temperature and form a uniform melt while stirring and rotating. It will be extruded from the extrusion port to form small plastic particles. The finished plastic particles will be dried and put into the injection molding machine. The plastic particles will melt under the heat, and the composition will be more uniform under the stirring action of the screw, and then extruded into sheets.

[0061] Example 6

[0062] Adding inorganic filler MoS to CF / PA66 polymer sheet without energy-conducting ribs 2 The method comprises the following steps:

[0063] (1) Carbon fiber CF, PA66 particles and MoS 2 The powders were mixed in mass percentages of 30%, 68.8% and 1.2%;

[0064] (2) Put the mixture into the feed port of the plastic granulator and feed it into the main body through the feed wheel. Inside the main body, PA66 will be melted by high temperature and form a uniform melt while stirring and rotating. It will be extruded from the extrusion port to form small plastic particles. The finished plastic particles will be dried and put into the injection molding machine. The plastic particles will melt under the heat, and the composition will be more uniform under the stirring action of the screw, and then extruded into sheets.

[0065] Example 7

[0066] Adding inorganic filler MoS into carbon fiber reinforced polyetherimide (CF / PEI) polymer sheet without energy-conducting ribs 2 The method comprises the following steps:

[0067] (1) Carbon fiber CF, PEI particles and MoS 2 The powders were mixed in mass percentages of 30%, 69.2% and 0.8%;

[0068] (2) Put the mixture into the feed port of the plastic granulator and feed it into the main body through the feed wheel. Inside the main body, PEI will be melted by high temperature and form a uniform melt while stirring and rotating. It will be extruded from the extrusion port to form small plastic particles. The finished plastic particles will be dried and put into the injection molding machine. The plastic particles will melt under the heat, and the composition will be more uniform under the stirring action of the screw, and then extruded into sheets.

[0069] Example 8

[0070] Adding inorganic filler MoS into polyetheretherketone (PMMA) without energy-conducting ribs 2 The method comprises the following steps:

[0071] (1) PMMA particles and MoS 2 The powders were mixed in a mass percentage of 99.2% and 0.8%;

[0072] (2) Put the mixture into the feed port of the plastic granulator and feed it into the main body through the feed wheel. Inside the main body, PMMA will be melted by high temperature and form a uniform melt while stirring and rotating. It will be extruded from the extrusion port to form small plastic particles. The finished plastic particles will be dried and put into the injection molding machine. The plastic particles will melt under the heat and the composition will be more uniform under the stirring action of the screw, and then extruded into sheets.

[0073] Example 9

[0074] Adding inorganic filler CaCO to CF / PA66 polymer sheet without energy-conducting ribs 3 The method comprises the following steps:

[0075] (1) Carbon fiber CF, PA66 particles and CaCO 3 The powders were mixed in mass percentages of 30%, 69.2% and 0.8%;

[0076] (2) Put the mixture into the feed port of the plastic granulator and feed it into the main body through the feed wheel. Inside the main body, PA66 will be melted by high temperature and form a uniform melt while stirring and rotating. It will be extruded from the extrusion port to form small plastic particles. The finished plastic particles will be dried and put into the injection molding machine. The plastic particles will melt under the heat, and the composition will be more uniform under the stirring action of the screw, and then extruded into sheets.

[0077] Example 10

[0078] Adding inorganic filler Ca into CF / PA66 polymer sheet without energy-conducting ribs 10 (PO4) 6 (OH) 2 The method comprises the following steps:

[0079] (1) Carbon fiber CF, PA66 particles and Ca 10 (PO4) 6 (OH) 2 The powders were mixed in mass percentages of 30%, 69.2% and 0.8%;

[0080] (2) Put the mixture into the feed port of the plastic granulator and feed it into the main body through the feed wheel. Inside the main body, PA66 will be melted by high temperature and form a uniform melt while stirring and rotating. It will be extruded from the extrusion port to form small plastic particles. The finished plastic particles will be dried and put into the injection molding machine. The plastic particles will melt under the heat, and the composition will be more uniform under the stirring action of the screw, and then extruded into sheets.

[0081] Embodiment 11

[0082] Adding inorganic filler CaCO into polyetheretherketone (PMMA) without energy-conducting ribs 3 The method comprises the following steps:

[0083] (1) PMMA particles and CaCO 3 The powders were mixed in a mass percentage of 99.2% and 0.8%;

[0084] (2) Put the mixture into the feed port of the plastic granulator and feed it into the main body through the feed wheel. Inside the main body, PMMA will be melted by high temperature and form a uniform melt while stirring and rotating. It will be extruded from the extrusion port to form small plastic particles. The finished plastic particles will be dried and put into the injection molding machine. The plastic particles will melt under the heat and the composition will be more uniform under the stirring action of the screw, and then extruded into sheets.

[0085] Example 12

[0086] Adding inorganic filler Ca into polyetheretherketone (PMMA) without energy-conducting ribs 10 (PO4) 6 (OH) 2 The method comprises the following steps:

[0087] (1) PMMA particles and Ca 10 (PO4) 6 (OH) 2 The powders were mixed in a mass percentage of 99.2% and 0.8%;

[0088] (2) Put the mixture into the feed port of the plastic granulator and feed it into the main body through the feed wheel. Inside the main body, PA66 will be melted by high temperature and form a uniform melt while stirring and rotating. It will be extruded from the extrusion port to form small plastic particles. The finished plastic particles will be dried and put into the injection molding machine. The plastic particles will melt under the heat, and the composition will be more uniform under the stirring action of the screw, and then extruded into sheets.

[0089] Embodiment 13

[0090] Adding inorganic filler CaCO into carbon fiber reinforced polyetherimide (CF / PEI) polymer sheet without energy-conducting ribs 3 The method comprises the following steps:

[0091] (1) Carbon fiber CF, PEI particles and CaCO 3 Mix in mass percentages of 30%, 69.2% and 0.8%;

[0092] (2) Put the mixture into the feed port of the plastic granulator and feed it into the main body through the feed wheel. Inside the main body, PEI will be melted by high temperature and form a uniform melt while stirring and rotating. It will be extruded from the extrusion port to form small plastic particles. The finished plastic particles will be dried and put into the injection molding machine. The plastic particles will melt under the heat, and the composition will be more uniform under the stirring action of the screw, and then extruded into sheets.

[0093] Embodiment 14

[0094] Adding inorganic filler Ca into carbon fiber reinforced polyetherimide (CF / PEI) polymer sheet without energy-conducting ribs 10 (PO4) 6 (OH) 2 The method comprises the following steps:

[0095] (1) Carbon fiber CF, PEI particles and Ca 10 (PO4) 6 (OH) 2 The particles were mixed at mass percentages of 30%, 69.2% and 0.8%;

[0096] (2) Put the mixture into the feed port of the plastic granulator and feed it into the main body through the feed wheel. Inside the main body, PEI will be melted by high temperature and form a uniform melt while stirring and rotating. It will be extruded from the extrusion port to form small plastic particles. The finished plastic particles will be dried and put into the injection molding machine. The plastic particles will melt under the heat, and the composition will be more uniform under the stirring action of the screw, and then extruded into sheets.

Claims

1. A method for improving the strength of ultrasonic welding joints of polymer sheets without energy-conducting ribs. It is characterized in that Before ultrasonic welding, a layered inorganic filler is added to the polymer sheet without energy conducting ribs; the layered inorganic filler is molybdenum disulfide with a two-dimensional nano multilayer structure, and the amount thereof is 0.5%-1.5% of the mass of the sheet.

2. The method for improving the strength of ultrasonic welding joints of polymer sheets without energy conducting ribs according to claim 1, It is characterized in that The particle size of the molybdenum disulfide is 0.5-5.0 μm.

3. The method for improving the strength of ultrasonic welding joints of polymer sheets without energy conducting ribs according to claim 1, It is characterized in that The amount of the inorganic filler is 0.8%-1.2% of the mass of the plate.

4. The method for improving the strength of ultrasonic welding joints of polymer sheets without energy conducting ribs according to claim 1, It is characterized in that The amount of the inorganic filler is 0.8%-1.0% of the mass of the plate.

5. The method for improving the strength of ultrasonic welding joints of polymer sheets without energy conducting ribs according to claim 1, It is characterized in that The energy conducting rib-free polymer sheet is a carbon fiber reinforced nylon 66 composite sheet, a carbon fiber reinforced polyetherimide composite sheet or a polyetheretherketone sheet.

6. The method for improving the strength of ultrasonic welded joints of polymer sheets without energy conducting ribs according to any one of claims 1, 2 or 5, It is characterized in that The method of adding a layered inorganic filler to a polymer sheet without energy conducting ribs comprises the following steps: (1) Mixing, by weight percentage, 98.5% to 99.5% of a polymer sheet without energy conducting ribs and 0.5% to 1.5% of a layered inorganic filler to obtain a mixture; (2) The mixture is granulated, dried and injection molded to obtain a sheet.

7. The method for improving the strength of ultrasonic welding joints of polymer sheets without energy conducting ribs according to claim 6, It is characterized in that In step (1), when the polymer sheet without energy conducting ribs is a composite material, the raw materials before compounding are added.

8. The method for improving the strength of ultrasonic welding joints of polymer sheets without energy conducting ribs according to claim 6, It is characterized in that When the energy-conducting rib-free polymer sheet is a carbon fiber reinforced nylon 66 composite sheet, the carbon fiber CF, PA66 particles and MoS 2 The powders are mixed in mass percentages of 25%-32%, 67.5%-74.5% and 0.5%-1.5%.

9. The method for improving the strength of ultrasonic welding joints of polymer sheets without energy conducting ribs according to any one of claims 1 to 5, It is characterized in that The ultrasonic welding adopts an overlapping method, the welding power is 2400-2800W, the welding pressure is 500-700N, the welding time is 1.7s-2.5s, and after the welding is completed, a permanently connected welding point is formed in the overlapping area.

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