Preparation method of high-orientation laminated structure composite film

Abstract

The invention belongs to the field of preparation of composite films, and discloses a preparation method of a high-orientation laminated structure composite film. A self-made preparation device is adopted and comprises a rectangular base, a horizontal cylindrical mold and a heating control system. Left-right strip-shaped guide rails are arranged on the top surfaces of the front side and the rear side of the base correspondingly. A rotating speed adjustable motor is fixedly arranged on the top surface of the right side of the base. Sliding blocks are arranged on the outer sides of the two guide rails respectively, limiting blocks are arranged at the upper ends of the sliding blocks, a mounting plate is fixed between the two limiting blocks, and a mounting base is arranged on the mounting plate; the mold is located over the base, end covers are detachably arranged at the two ends of the mold, air holes are formed in the two end covers, and horizontal supporting shafts are fixed to the centers of the two end covers respectively, rotationally connected with the mounting base and connected with an output shaft of the rotating speed adjustable motor respectively. According to the method, the laminated structure composite film which is high in orientation and compact in stacking can be prepared.

Description

Technical Field

[0001] The invention belongs to the technical field of composite film preparation, and in particular relates to a method for preparing a composite film with a high-orientation layered structure. Background Art

[0002] In recent years, bionic layered composite films derived from the layered structure of shells have become one of the important research directions in many disciplines such as materials, chemistry, and life sciences. Among them, the lightweight, high-strength, and high-toughness layered composite films based on shell biomimetic manufacturing have excellent mechanical properties with a multi-scale, multi-level "brick-mud" stacking structure. The highly oriented and densely stacked low-dimensional functional fillers make the bionic layered composite films have excellent electron / phonon transmission properties. However, composite films prepared by traditional film-forming processes, such as vacuum-assisted filtration, evaporation-induced self-assembly, doctoring, and hot pressing, often have problems such as low orientation and loose stacking. Therefore, it is urgent to develop a method for preparing highly oriented, densely stacked layered composite films. Summary of the invention

[0003] In view of the problems of low orientation and loose stacking in the preparation process of layered composite films in the prior art, the object of the present invention is to provide a method for preparing a highly oriented and densely stacked layered composite film.

[0004] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A method for preparing a highly oriented layered structure composite film, the special features of which are: using a self-made preparation device, the preparation device comprising a rectangular base, a horizontal cylindrical mold and a heating control system; A left-right strip guide rail is fixedly provided on the top surfaces of the front and rear sides of the base, and an adjustable speed motor is fixedly provided at the middle position of the top surface of the right side of the base; The outer sides of the two guide rails are slidably connected with a slider, the upper ends of the sliders are fixedly connected with a limit block, a mounting plate is fixedly connected between the two limit blocks in the front-back direction, and a mounting seat is fixedly connected to the middle position of the mounting plate; The mold is located directly above the base between the two guide rails. Both ends of the mold are detachably provided with end covers, and a number of air holes are evenly arranged on the end covers. A horizontal support shaft is fixedly arranged at the center of each of the end covers, and the right horizontal support shaft is connected to the output shaft of the adjustable speed motor, and the left horizontal support shaft is rotatably connected to the mounting seat. The heating control system includes a heating device, a thermocouple and a temperature controller. The heating device is located directly above, directly below, in front of or behind the mold. The working end of the thermocouple probe is located close to the heated surface of the outer wall of the mold. The thermocouple and the heating device are respectively connected to the temperature controller, which is placed at an idle position on the outer periphery of the base. The preparation steps are as follows: (1) Loosen the limit bolts on the two limit blocks and pull them out of the limit holes. Then remove the connection between the left horizontal support shaft and the mounting seat. Slide the two sliders to the left to make the left horizontal support shaft come out of the mounting seat. (2) Remove the left end cover of the mold and attach a layer of polymer release film to the inner wall of the mold; (3) According to the required ratio of the target product layered composite film, weigh the polymer and the layered filler, add a solvent to prepare a polymer / filler dispersion system to ensure that the polymer concentration is 1-10 wt%, and add the polymer / filler dispersion system into the mold; (4) Install the left end cover of the upper mold, slide the two sliders to the right, insert the limit bolts on the two limit blocks into the limit holes and tighten them, and at the same time rotate the left horizontal support shaft to connect it to the mounting seat; (5) Start the adjustable speed motor and adjust the speed between 1000 and 6000 rpm. At the same time, start the temperature controller and set the temperature that can evaporate the solvent in the polymer / filler dispersion system. The heating device starts to heat the rotating mold. (6) After the mold rotates for 1 to 6 hours and no gas evaporates from the vent holes on the end cover, turn off the temperature controller and the adjustable speed motor; (7) After the temperature of the outer wall of the mold cools down to room temperature, repeat the operation of step (1), remove the left end cover of the mold, take out the polymer release film, and peel off the layered composite film from the polymer release film.

[0005] Preferably, the polymer is one or more of polyvinyl alcohol, polyethylene, polypropylene, chitosan, cellulose and its derivatives, aramid nanofibers, and polyvinylidene fluoride.

[0006] Preferably, the layered filler is one or more of MXene, graphene, boron nitride, molybdenum sulfide, montmorillonite, kaolin, and mica.

[0007] Preferably, the polymer release film is one of polycarbonate, PPSU and PI.

[0008] Furthermore, the heating device is an electric heating tube, an infrared radiation heating lamp, a heater or an electric furnace, and when the heating device is an infrared radiation heating lamp, a heater or an electric furnace, the heating device is fixed directly above, on the front side or on the rear side of the mold by a fixing device; when the heating device is an electric heating tube, the heating device is fixed directly above or directly below the mold by a fixing device.

[0009] Preferably, when the heating device is an electric heating tube, the corresponding fixing device is an arc plate, the curvature of the arc plate is the same as the mold, and the inner arc surface of the arc plate is parallel to the central axis of the mold and fixed with several electric heating tubes; an installation groove is opened on the base directly below the mold, and the arc plate is fixed in the installation groove.

[0010] Furthermore, the mounting groove is a through groove, a strip plate is fixedly provided at the middle position of the bottom of the arc plate along its axis, U-shaped fixing parts are fixed at intervals on the left and right of the strip plate, the opening of the fixing part faces the bottom of the arc plate and the middle part is vertically fixed on the strip plate, and the two side ends of the fixing part are bent outward and fixed to the bottom of the base on both sides of the through groove.

[0011] Furthermore, a first plug is rotatably connected to the top surface of the base on the front side of the through slot, and a first plug is provided on the first plug. The probe of the thermocouple is inserted in the first plug and its working end is close to the heated surface of the outer wall of the mold.

[0012] Preferably, a plurality of limit holes are provided at intervals on the top surfaces of the two guide rails, a bolt hole is provided on the left end or the right end of the limit block, a limit bolt is provided in the bolt hole, and the limit bolt is threadedly connected to the limit hole on the guide rail; such a design makes it convenient to limit the position of the slider when the slider slides to the expected position.

[0013] Preferably, an inverted T-shaped limiting plate is fixed on the top surface of the base at least at the left end of the left and right side ends of the two guide rails; such a design can prevent the slider from sliding out of the guide rail.

[0014] Preferably, a safety cover that matches the size of the mold is provided on the outer side of the cylinder of the mold, the rear end of the safety cover is hinged to the outer side surface of the rear end of the base, the front end of the safety cover is fixedly provided with a handle and a second plug piece that is rotatably connected, and the second plug piece is provided with a second socket; a fixing hole is opened on the outer side surface of the front end of the base, and the fixing hole and the second socket are fixedly connected by bolts; such a design can improve the safety of the device.

[0015] Furthermore, the shape of the safety cover is an arc or polygon that matches the size of the mold.

[0016] Furthermore, a number of heat dissipation holes are evenly arranged on the safety cover; such a design facilitates the dissipation of the mold temperature and increases the safety of the device.

[0017] Furthermore, two end covers matching the sizes of the two ends of the mold are provided at the left and right ends of the mold. The two end covers are respectively matched with the left and right end faces of the safety cover and are integrally formed therewith. Space for the guide rail to extend is reserved at the bottom of the two end covers.

[0018] Beneficial effects: The present invention has a simple structure, is easy to operate, and is efficient in operation. Through the high-speed centrifugal movement of the mold, the liquid or colloidal polymer / filler dispersion system can be evenly spread over the inner wall of the mold. Due to the density difference of the constituent substances of the dispersion system, the internal filler and polymer molecular chains are subjected to the outward centrifugal force, thereby promoting the orderly arrangement and dense stacking of the filler and polymer molecular chains. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 : A three-dimensional structural diagram of one embodiment of the preparation device of the present invention (without a safety cover and omitting the heating control system); Figure 2 : A schematic diagram of the main structure of one embodiment of the preparation device of the present invention; Figure 3 : A schematic diagram of a top view of one embodiment of the preparation device of the present invention; Figure 4 : Schematic diagram of the three-dimensional structure of the arc plate and the electric heating tube; Figure 5 : Schematic diagram of the upward structure in which the curved plate is fixed on the base; Figure 6 : A schematic diagram of the three-dimensional structure of the second embodiment of the preparation device of the present invention (with a safety cover and omitting the heating control system); Figure 7 : WAXD azimuthal integral curves (a, c) and statistics of FWHM and Herman orientation factor f value (b, d) of each sample obtained in Examples 1-9 and Comparative Example 1; Among them, the figure markings are: 1-base; 2-mold; 3-guide rail; 4-motor; 5-slider; 6-limit block; 7-mounting plate; 8-mounting seat; 9-limit plate; 10-limit hole; 11-bolt hole; 12-end cover; 13-horizontal support shaft; 14-mounting groove; 15-safety cover; 16-end cover; 17-heat dissipation hole; 18-arc plate; 19-electric heating tube; 20-strip plate; 21-fixing piece; 22-first plug; 23-first socket. DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described below in conjunction with specific embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the described embodiments, all other embodiments obtained by those skilled in the art without creative work belong to the protection scope of the present invention.

[0021] Example 1

[0022] A method for preparing a highly oriented layered composite film, using a homemade preparation device, such as Figures 1 to 5 As shown, the preparation device includes a rectangular base 1, a horizontal cylindrical mold 2 and a heating control system; a left-right strip guide rail 3 is fixedly provided on the top surface of the front and rear sides of the base 1, and an adjustable speed motor 4 is fixedly provided at the middle position of the right top surface of the base 1; a plurality of limit holes 11 are provided at intervals on the top surfaces of the two guide rails 3, and a slider 5 is slidably connected to the outer sides of the two guide rails 3, and a limit block 6 is fixedly connected to the upper end of the slider 5, and a bolt hole 10 is opened at the left end of the limit block 6, and a limit bolt (not shown) is provided in the bolt hole 10, and the limit bolt is threadedly connected to the limit hole 11 on the guide rail 3 ; A mounting plate 7 is fixedly connected between the two limit blocks 6 in the front-to-back direction, and a mounting seat 8 is fixedly connected to the middle position of the mounting plate 7; an inverted T-shaped limit plate 9 is fixed on the top surface of the base 1 at the left and right ends of the two guide rails 3; the mold 2 is located directly above the base 1 between the two guide rails 3, and the two ends of the mold 2 are detachably provided with end covers 12, and the two end covers 12 are provided with a plurality of air holes (not shown), and a horizontal support shaft 13 is fixedly provided at the center position of each of the two end covers 12, and the right horizontal support shaft 13 is connected to the output shaft of the adjustable speed motor 4, and the left horizontal support shaft 13 is connected to the mounting seat 8 Rotating connection; the heating control system includes a heating device, a thermocouple (not shown) and a temperature controller (not shown), the heating device is located directly below the mold 2, the working end of the thermocouple probe is located close to the heated surface of the outer wall of the mold 2, the thermocouple and the heating device are respectively connected to the temperature controller, and the temperature controller is placed at an idle position on the periphery of the base 1; the heating device is a plurality of electric heating tubes 19, and a mounting groove 14 is provided on the base 1 directly below the mold 2, the mounting groove 14 is a through groove, and an arc plate 18 is fixed in the through groove, and the curvature of the arc plate 18 is the same as that of the mold 2, and the plurality of electric heating tubes 19 are parallel to the mold The central axis of the arc plate 2 is fixed to the inner arc surface of the arc plate 18; a strip plate 23 is fixedly provided at the middle position of the bottom of the arc plate 18 along its axis, and U-shaped fixing members 21 are fixed to the strip plate 23 at intervals on the left and right, the opening of the fixing member 21 faces the bottom of the arc plate 18 and the middle part is vertically fixed on the strip plate 21, and the two side ends of the fixing member 21 are bent outwardly and fixed to the bottom of the base 1 on both sides of the through groove; a first plug sheet 22 is rotatably connected to the top surface of the base 1 on the front side of the through groove, and a first plug sheet 22 is provided with a first plug hole 23, and a probe of the thermocouple is inserted in the first plug hole 23 and its working end is close to the heating surface of the outer wall of the mold 2; The preparation steps are as follows: (1) Loosen the limit bolts on the two limit blocks 6 and pull them out of the limit holes 11, then remove the connection between the left horizontal support shaft 13 and the mounting seat 8, and slide the two sliders 5 to the left to make the left horizontal support shaft 13 disengage from the mounting seat 8; (2) Remove the left end cover 12 of the mold 2 and attach a layer of polycarbonate release film to the inner wall of the mold 2; (3) According to the required ratio of the target product layered composite film, weigh 1 g of PVA particles and 1.5 g of Mxene, add water to prepare a polymer / filler dispersion system (PVA concentration is 1 wt%), and add the polymer / filler dispersion system into mold 2; (4) Install the left end cover 12 of the upper mold 2, slide the two sliders 5 to the right, insert the limit bolts on the two limit blocks 6 into the limit holes 11 and tighten them, and at the same time rotate the left horizontal support shaft 13 to connect it to the mounting seat 8; (5) Start the adjustable speed motor 4, adjust the speed to 4000 rpm, and start the temperature controller at the same time, set the temperature to 100°C, and the heating device starts to heat the rotating mold 2; (6) The polymer / filler dispersion system forms a film on the inner wall of the mold 2 under the high-speed centrifugal force of the mold 2, and the polymer / filler dispersion system gradually evaporates the solvent due to heat while forming the film. After the mold 2 rotates for 1 hour and the solvent is completely evaporated (no gas evaporates from the vent holes on the end cover 12), turn off the temperature controller and the adjustable speed motor 4; (7) After the temperature of the outer wall of the mold 2 naturally cools down to room temperature, repeat the operation of step (1), remove the left end cover 12 of the mold 2, take out the polymer release film (at this time, the layered composite film is attached to it), and peel off the layered composite film from the polymer release film. The sample is recorded as M6P4(1)-4000.

[0023] Example 2

[0024] The difference from Example 1 is that in step (3), the PVA concentration in the prepared polymer / filler dispersion system is 1.5 wt %; the rest is the same as Example 1.

[0025] The sample obtained in this example is recorded as M6P4(1.5)-4000.

[0026] Example 3

[0027] The difference from Example 1 is that in step (3), the PVA concentration in the prepared polymer / filler dispersion system is 2 wt %; the rest is the same as Example 1.

[0028] The sample obtained in this example is recorded as M6P4(2)-4000.

[0029] Example 4

[0030] The difference from Example 1 is that in step (3), the PVA concentration in the prepared polymer / filler dispersion system is 2.5 wt %; the rest is the same as Example 1.

[0031] The sample obtained in this example is recorded as M6P4(2.5)-4000.

[0032] Example 5

[0033] The difference from Example 1 is that in step (3), the PVA concentration in the prepared polymer / filler dispersion system is 3 wt %; the rest is the same as Example 1.

[0034] The sample obtained in this example is recorded as M6P4(3)-4000.

[0035] Example 6

[0036] The difference from Example 1 is that in step (3), the PVA concentration in the prepared polymer / filler dispersion system is 2 wt %, and in step (5), the rotation speed is adjusted to 3000 rpm; the rest is the same as in Example 1.

[0037] The sample obtained in this example is recorded as M6P4(2)-3000.

[0038] Example 7

[0039] The difference from Example 1 is that in step (3), the PVA concentration in the prepared polymer / filler dispersion system is 2 wt %, and in step (5), the rotation speed is adjusted to 2000 rpm; the rest is the same as in Example 1.

[0040] The sample obtained in this example is recorded as M6P4(2)-2000.

[0041] Example 8

[0042] The difference from Example 1 is that in step (3), the PVA concentration in the prepared polymer / filler dispersion system is 2 wt %, and in step (5), the rotation speed is adjusted to 1000 rpm; the rest is the same as in Example 1.

[0043] The sample obtained in this example is recorded as M6P4(2)-1000.

[0044] Example 9

[0045] The difference from Example 1 is that: Figure 6As shown, a polygonal safety cover 15 matching the size of the mold 2 is provided on the outer side of the cylinder of the mold 2, and two end covers 16 matching the sizes of the two ends of the mold 2 are provided on the left and right ends of the mold 2. The two end covers 16 are respectively matched with the shapes of the left and right end faces of the safety cover 15 and are integrally formed therewith, and a space for the guide rail 3 to extend is reserved at the bottom of the two end covers 16; a plurality of heat dissipation holes 17 are evenly provided on the safety cover 15, the rear end of the safety cover 15 is hinged to the outer side surface of the rear end of the base 1, and the front end of the safety cover 15 is respectively fixed with a handle (not shown) and rotatably connected with a second plug sheet (not shown), and the second plug sheet is provided with a second plug hole (not shown); a fixing hole (not shown) is opened on the outer side surface of the front end of the base 1, and the fixing hole and the second plug hole are fixedly connected by bolts.

[0046] The rest is the same as in Example 1.

[0047] Note: When the safety cover 15 needs to be covered, the operator holds the handle to close the safety cover 15, then rotates the second plug piece to align the second plug hole with the fixing hole, and inserts the bolt; when the safety cover 15 needs to be opened, the bolt is removed and pulled out from the fixing hole and the second plug hole, the second plug piece is rotated away from the fixing hole, and the operator holds the handle to rotate the safety cover 15 backward until it is fully opened.

[0048] Comparative Example 1 1 g of PVA particles and 1.5 g of Mxene were weighed and water was added to prepare a polymer / filler dispersion system (PVA concentration was 2 wt%). Then, a single-pass scraping process was used with a scraper height of 800 μm to prepare a composite film with a thickness similar to that of Example 1 as a comparison sample, and the sample was recorded as M6P4(2)-0.

[0049] In order to evaluate the distribution and arrangement of MXene fillers in the composite films obtained in Examples 1-8 and Comparative Example 1, the WAXD azimuthal integral curve, FWHM and Herman orientation factor f value of each sample were statistically analyzed. The results are as follows: Figure 7 As shown. Figure 7 It can be seen that the f values ​​of the samples obtained in Examples 1-8 are significantly higher than those in Comparative Example 1, and the f value of Example 3 can reach 0.794, while the f value of Comparative Example 1 is only 0.681; at the same time, the integral curves of the films obtained in Examples 1-8 are sharper than those in Comparative Example 1, and the FWHM is narrower, indicating that the orientation degree of the layered filler in the composite film obtained by the preparation method provided by the present invention is significantly higher than that of the composite film obtained by the traditional scraping method, and the filler arrangement is more compact.

Claims

1. A method for preparing a highly oriented layered composite film, characterized in that: A self-made preparation device is used, which includes a rectangular base, a horizontal cylindrical mold and a heating control system; A left-right strip guide rail is fixedly provided on the top surfaces of the front and rear sides of the base, and an adjustable speed motor is fixedly provided at the middle position of the top surface of the right side of the base; The outer sides of the two guide rails are slidably connected with a slider, the upper ends of the sliders are fixedly connected with a limit block, a mounting plate is fixedly connected between the two limit blocks in the front-back direction, and a mounting seat is fixedly connected to the middle position of the mounting plate; The mold is located directly above the base between the two guide rails. Both ends of the mold are detachably provided with end covers, and a number of air holes are evenly arranged on the end covers. A horizontal support shaft is fixedly arranged at the center of each of the end covers, and the right horizontal support shaft is connected to the output shaft of the adjustable speed motor, and the left horizontal support shaft is rotatably connected to the mounting seat. The heating control system includes a heating device, a thermocouple and a temperature controller. The heating device is located directly above, directly below, in front of or behind the mold. The working end of the thermocouple probe is located close to the heated surface of the outer wall of the mold. The thermocouple and the heating device are respectively connected to the temperature controller, which is placed at an idle position on the outer periphery of the base. The preparation steps are as follows: (1) Loosen the limit bolts on the two limit blocks and pull them out of the limit holes. Then remove the connection between the left horizontal support shaft and the mounting seat. Slide the two sliders to the left to make the left horizontal support shaft come out of the mounting seat. (2) Remove the left end cover of the mold and attach a layer of polymer release film to the inner wall of the mold; (3) According to the required ratio of the target product layered composite film, weigh the polymer and the layered filler, add a solvent to prepare a polymer / filler dispersion system to ensure that the polymer concentration is 1-10 wt%, and add the polymer / filler dispersion system into the mold; (4) Install the left end cover of the upper mold, slide the two sliders to the right, insert the limit bolts on the two limit blocks into the limit holes and tighten them, and at the same time rotate the left horizontal support shaft to connect it to the mounting seat; (5) Start the adjustable speed motor and adjust the speed between 1000 and 6000 rpm. At the same time, start the temperature controller and set the temperature that can evaporate the solvent in the polymer / filler dispersion system. The heating device starts to heat the rotating mold. (6) After the mold rotates for 1 to 6 hours and no gas evaporates from the vent holes on the end cover, turn off the temperature controller and the adjustable speed motor; (7) After the temperature of the outer wall of the mold cools down to room temperature, repeat the operation of step (1), remove the left end cover of the mold, take out the polymer release film, and peel off the layered composite film from the polymer release film.

2. The method for preparing a highly oriented layered composite film according to claim 1, characterized in that: The polymer is one or more of polyvinyl alcohol, polyethylene, polypropylene, chitosan, cellulose and its derivatives, aramid nanofiber, and polyvinylidene fluoride.

3. The method for preparing a highly oriented layered composite film according to claim 1, wherein: The layered filler is one or more of MXene, graphene, boron nitride, molybdenum sulfide, montmorillonite, kaolin, and mica.

4. The method for preparing a highly oriented layered composite film according to claim 1, wherein: The polymer release film is one of polycarbonate, PPSU and PI.

5. The method for preparing a highly oriented layered composite film according to claim 1, characterized in that: The heating device is an electric heating tube, an infrared radiation heating lamp, a heater or an electric furnace, and when the heating device is an infrared radiation heating lamp, a heater or an electric furnace, the heating device is fixed directly above, on the front side or on the rear side of the mold by a fixing device; when the heating device is an electric heating tube, the heating device is fixed directly above or directly below the mold by a fixing device.

6. The method for preparing a highly oriented layered composite film according to claim 5, characterized in that: When the heating device is an electric heating tube, the corresponding fixing device is an arc plate, the curvature of the arc plate is the same as the mold, and a plurality of electric heating tubes are fixedly installed on the inner arc surface of the arc plate parallel to the central axis of the mold; an installation groove is opened on the base directly below the mold, and the arc plate is fixed in the installation groove.

7. The method for preparing a highly oriented layered composite film according to claim 6, characterized in that: The mounting groove is a through groove, a strip plate is fixedly provided at the middle position of the bottom of the arc plate along its axis, U-shaped fixing pieces are fixed at intervals on the left and right of the strip plate, the opening of the fixing piece faces the bottom of the arc plate and the middle part is vertically fixed on the strip plate, and the two side ends of the fixing piece are bent outward and fixed to the bottom of the base on both sides of the through groove.

8. The method for preparing a highly oriented layered composite film according to claim 1, characterized in that: A plurality of limiting holes are arranged at intervals on the top surfaces of the two guide rails. A bolt hole is opened at the left end or the right end of the limiting block. A limiting bolt is arranged in the bolt hole. The limiting bolt is threadedly connected with the limiting hole on the guide rail.

9. The method for preparing a highly oriented layered composite film according to claim 1, wherein: An inverted T-shaped limiting plate is respectively fixed on the top surface of the base at at least the left end of the left and right side ends of the two guide rails.

10. The method for preparing a highly oriented layered composite film according to claim 1, characterized in that: A safety cover that matches the size of the mold is provided on the outer side of the cylinder of the mold, the rear end of the safety cover is hinged to the outer side surface of the rear end of the base, the front end of the safety cover is fixed with a handle and rotatably connected with a second plug-in piece, and the second plug-in piece is provided with a second socket; a fixing hole is opened on the outer side surface of the front end of the base, and the fixing hole and the second socket are fixedly connected by bolts.

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