AUTOMATIC PRODUCTION APPARATUS FOR HIGH-THERMAL-CONDUCTIVITY FLOCKING PAD

Abstract

An automatic production apparatus for high-thermal-conductivity flocking pad includes a conveyor belt system, a cutting assembly, an electrostatic flocking assembly, a perfusion device and a thermosetting device, wherein the electrostatic flocking assembly is connected to a power supply which is configured for outputting a step-wave voltage through a bottom screen mesh thereof. The polymer matrix is conveyed through the conveyor belt system, and is stretched, flocked in the step-wave electric field, shrunk, poured and dried to form a flocking pad product with high-thermal-conductivity. In this invention, the polymer matrix is stretched and shrunk to make the flocking be dense by regulating and controlling the speed of the conveyor belt system, a step-wave electric field is provided during the flocking process, and meanwhile, the flocking, pouring and curing time is regulated and controlled.

Claims

1. An automatic production apparatus for high-thermal-conductivity flocking pad, comprising: a conveyor system (2) for conveying polymer matrix; an electrostatic flocking assembly (3) for flocking on the polymer matrix; a perfusion device (4) for pouring on the flocked polymer matrix to form a composite; and a thermosetting device (5) for curing the poured polymer matrix; the conveying system (2) comprising at least a first conveyer belt (201), a second conveyer belt (202) and a third conveyer belt (203); the electrostatic flocking assembly (3) being arranged above the second conveyer belt (202), and the perfusion device (4) and the thermosetting device (5) being arranged above the third conveyer belt (203); the polymer matrix being conveyed from the first conveyer belt (201) to the second conveyer belt (202) for flocking, and then conveyed to the third conveyer belt (203) for pouring resin and curing, and rotary speeds of the first conveyer belt (201) and the third conveyer belt (203) both being lower than the rotary speed of the second conveyer belt (202).

2. The automatic production apparatus according to claim 1, wherein the electrostatic flocking assembly (3) comprises a flocking box (301), a high-voltage power supply (302) and a grounded plate (303), the flocking box (301) is configured for accommodating staple fibers and comprises a bottom screen mesh bottom face, the high-voltage power supply (302) comprises a positive output terminal connected to the bottom screen mesh bottom face, and the screen mesh bottom face and the grounded plate (303) are located at two sides of the second conveyer belt (202), respectively.

3. The automatic production apparatus according to claim 2, further comprising a cutting assembly (1) which comprises a cutting blade (101), a fiber reel (102), a draw-off roller (103) and a vibration conveyer plate (105), fibers on the fiber reel (102) being pulled to a cutting area by the draw-off roller (103) and cut into staple fibers by the cutting blade (101), the cut staple fibers being vibrated and dispersed by the vibration conveyer plate (105) and then input to the flocking box (301) of the electrostatic flocking assembly (3).

4. The automatic production apparatus according to claim 3, wherein the vibration conveyer plate (105) comprises a front end located below the cutting blade (101) and a rear end located above the flocking box (301), and is inclined downwardly by 30 degrees from the front end to the rear end.

5. The automatic production apparatus according to claim 4, wherein the output voltage of the high-voltage power supply (302) is a gradually increased step-wave voltage.

6. The automatic production apparatus according to claim 3, wherein the output voltage of the high-voltage power supply (302) is a gradually increased step-wave voltage.

7. The automatic production apparatus according to claim 2, wherein the output voltage of the high-voltage power supply (302) is a gradually increased step-wave voltage.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 is a schematic view of an automatic production apparatus for high-thermal-conductivity flocking pad.

[0026] FIG. 2 is a schematic view of the principle and effect of electrostatic flocking.

[0027] FIG. 3A shows a SEM image of vertical-oriented carbon staple fiber arrays, which are obtained under the condition of: the rotary speed ratio of the conveyer belts a1:a2:a3=1:1:1, and high voltage.

[0028] FIG. 3B shows a SEM image of vertical-oriented carbon staple fiber arrays, which are obtained under the condition of: the rotary speed ratio of the conveyer belts a1:a2:a3=4:6:3, and high voltage.

[0029] FIG. 3C shows a SEM image of vertical-oriented carbon staple fiber arrays, which are obtained under the condition of: the rotary speed ratio of the conveyer belts a1:a2:a3=4:6:3, and a step-wave voltage.

[0030] In the drawings:

[0031] 1 cutting assembly;

[0032] 101 cutting blade;

[0033] 102 fiber reel;

[0034] 103 draw-off roller;

[0035] 104 auxiliary locator;

[0036] 105 vibrating conveyer plate;

[0037] 2 conveyor system;

[0038] 201 first conveyer belt;

[0039] 202 second conveyer belt;

[0040] 203 third conveyer belt;

[0041] 3 electrostatic flocking assembly;

[0042] 301 flocking box;

[0043] 302 high voltage power supply;

[0044] 303 grounded plate;

[0045] 4 perfusion device; and

[0046] 5 thermosetting device.

DESCRIPTION OF THE EMBODIMENTS

[0047] For better illustrating the technical means, creative features, objects and effects of the present invention, detailed description will be given for the embodiments provided by the present invention with reference to the append drawings. It should be understood that the specific embodiments described here are only used to explain the present invention, not to restrict the present invention.

[0048] Referring to FIG. 1, the present invention provides an automatic production apparatus for high-thermal-conductivity flocking pad, which includes: [0049] a conveyor system 2 for conveying a polymer matrix; [0050] an electrostatic flocking assembly 3 for flocking on the polymer matrix; [0051] a perfusion device 4 for pouring on the flocked polymer matrix to form a composite; and [0052] a thermosetting device 5 for curing the poured polymer matrix. [0053] the conveyor system 2 at least includes a first conveyer belt 201, a second conveyer belt 202, and a third conveyer belt 203; the electrostatic flocking assembly 3 is arranged above the second conveyer belt 202, and the perfusion device 4 and the thermosetting device 5 are arranged above the third conveyer belt 203; the polymer matrixes are conveyed from the first conveyer belt 201 to the second conveyer belt 202 for flocking in sequence, and then conveyed to the third conveyer belt 203 for pouring resin and curing, and rotary speeds of the first conveyer belt 201 and the third conveyer belt 203 both are lower than the rotary speed of the second conveyer belt 202.

[0054] The polymer matrix which is stretchable, adhesive, and has a required size is adhered to the first conveyer belt 201, and conveyed to the second conveyer belt 202. The rotary speed of the second conveyer belt 202 is set to be greater than the rotary speed of the first conveyer belt 201, the polymer matrix is stretched when it is conveyed from the first conveyer belt 201 to the second delivery bel 202. The polymer matrix after stretched remains its stretched state, and then electrostatic flocking is performed on the polymer matrix when it passes through the flocking assembly 3. The polymer matrix after flocked is conveyed to the third conveyer belt 203. The rotary speed of the third conveyer belt 203 is set to be less than the rotary speed of the second conveyer belt 202, so that the polymer matrix shrinks when it is conveyed from the second conveyer belt 202 to the third conveyer belt 203, resulting in a dense arrangement of flocked staple fibers. Resin is poured through the perfusion device 4, and then the resin is solidified and molded through the thermosetting device 5.

[0055] Further, a tensile ratio of the stretchable polymer matrix is regulated by the speed ratio of the first conveyer belt 201 to the second conveyer belt 202 of the conveyor system 2. An electrostatic flocking time of the staple fibers is regulated by the speed of the second conveyer belt 202. A curing time of the thermosetting device is regulated by the speed of the third conveyer belt 203.

[0056] In the drawings, the electrostatic flocking assembly 3 includes a flocking box 301, a high-voltage power supply 302, and a grounded plate 303. The flocking box 301 is used to accommodate staple fibers and includes a conductive bottom scree mesh. An output voltage of the high-voltage power supply 302 is a gradually increased step-wave voltage. A positive output terminal of the high-voltage power supply 302 is connected to the bottom scree mesh. The bottom scree mesh and the grounded plate 303 are located at two sides of the conveyer belt, respectively, and cooperatively form a high-voltage electric field, polarizing the staple fibers and inserting them vertically into the stretched polymer matrix for flocking.

[0057] In the drawings, the automatic production apparatus further includes a cutting assembly 1, which includes a cutting blade 101, a fiber reel 102, a draw-off roller 103 , an auxiliary locator 104, and a vibrating conveyer plate 105. The fiber reel 102 is positioned at a lateral side of the cutting blade 101. Fibers on the fiber reel 102 are pulled to a cutting area by the draw-off roller 103, and are cut by the cutting blade 101 to form staple fibers. The cut staple fibers are vibrated and dispersed through the vibrating conveyer plate 105 and then input to the electrostatic flocking box 301 of the electrostatic flocking assembly 3 for standby.

[0058] In the drawings, a plastic sleeve of the auxiliary locator 104 is matched with the fiber bundle in size and is fixed, which is able to prevent the fibers from swinging during the cutting process and in turn prevent uneven size of the fibers.

[0059] In the drawings, addition silicone rubber is used in the perfusion device 4, and components A and B are respectively stirred and mixed evenly before perfusion of the prepared staple fiber array.

[0060] In the drawings, a plurality of polymer matrixes are arranged on the first conveyer belt to realize the continuous production of high-thermal-conductivity flocking pad. Considering issues such as tensile ratios, it is necessary to reasonably design the distance between two neighboring polymer matrixes. Assume that the rotary speed ratio of the first conveyer belt (a1) to the second conveyer belt (a2) is consistent with the tensile ratio of the polymer matrix, and the rotary speed of the third conveyer belt (a3) is less than or equal to the rotary speed of the first conveyer belt (a1). The specific rotary speed (a2) of the second conveyer belt is determined by the flocking time of the fibers. The specific rotary speed (a3) of the third conveyer belt is determined by the curing time of the poured polymer matrix. The relationship between the distance (d) of neighboring polymer matrixes and the length (l) of the polymer matrixes on the first conveyer belt needs to meet the following equation:

[00001]$\frac{l+d}{l}>\frac{a1}{a3}$

[0061] Preferably, the cut staple fibers are conveyed to the flocking box 301 through the vibrating conveyer plate 105. The vibrating conveyer plate 105 has a front end located below the cutting blade 101 and a rear end located above the flocking box 301, and is inclined downwardly by 30 degrees from the head end to the tail end. By means of the vibrating conveyer plate, the fibers are effectively dispersed, which prevents the fibers aggregation and facilitates subsequent flocking process, thereby obtaining a thermal conductive pad with high flocking density, good fiber orientation and high vertical thermal conductivity (22.59 W/mK).

[0062] The process of preparing the thermal conductive pad by the apparatus of FIG. 1 is as follows:

[0063] Embodiment 1

[0064] The apparatus is started, the tensile ratio of the polymer matrix before and after stretching is set to 1:1.5, the speed ratio of the first, second and third conveyer belts are set to a1:a2:a3=4:6:3. Firstly, the polymer matrix which is made of elastic acrylic acid with a size of 3 cm*3 cm is put on a front end of the first belt 201, wherein the distance d between neighboring polymer matrixes is 3.5 mm, and conveyed to the rear end and then conveyed to the second conveyer belt 202. At the same time, the carbon fibers with a diameter of 5 um is pulled from the fiber reel 102 by the draw-off roller 103, passing through the auxiliary locator 104, and cut into staple fibers with a uniform length of 1 mm by the cutting blade 101. The staple fibers will be vibrated and dispersed by the vibrating conveyer plate 105 and then enter the electrostatic flocking device 3. The high-voltage power supply 302 outputs a voltage of 20 kV directly through the positive output terminal to the bottom screen mesh. The elastic acrylic polymer matrix is stretched for the speed difference between the first conveyer belt 201 and the second conveyer belt 202, and then conveyed to a top side of the grounded plate 303 through the second conveyer belt 202. The flocking principle is shown in FIG. 2: the carbon staple fibers are polarized and charged, and inserted vertically into the elastic acrylic polymer matrix which is at the top side of the second conveyer belt 202 when they pass through a high potential difference region of the flocking box 301 formed between the bottom screen mesh and the grounded plate 303. As the second conveyer belt 202 exits the high potential difference region, the maximum flocking density is reached, and a vertical-oriented carbon staple fiber array is prepared. An image of such array obtained by SEM (scan electron microscope) is shown in FIG. 3B. The prepared carbon staple fiber array will be conveyed alongwith the second conveyer belt 202 to the third conveyer belt 203, and will be shrunk for the rotary speed difference between the second conveyer belts 202 and the third conveyer belt 203. Subsequently, in the perfusion device 4, components A and B of addition type silicone gel are fully mixed in 1:1 ratio and then poured into the carbon staple fiber array. After being cured and compounded by the thermosetting device 5, a composite thermal conductive pad with highly aligned carbon fiber is prepared.

[0065] Comparative Example 1

[0066] Compared with embodiment 1, the difference is merely in step 1. After the apparatus is started, the tensile ratio of the polymer matrix before and after stretching is set to 1:1, and the speed ratio of the first, second and third conveyer belts are set to a1:a2:a3=1:6:1. The image of the prepared vertical-oriented carbon staple fiber array obtained by SEM is shown in FIG. 3A.

[0067] Embodiment 2

[0068] The apparatus is started, the tensile ratio of the polymer matrix before and after stretching is set to 1:1.5, the speed ratio of the first, second and third conveyer belts are set to a1:a2:a3=4:6:3. Firstly, the polymer matrix which is made of elastic acrylic acid with a size of 3 cm*3 cm is put on a front end of the first belt 201, wherein the distance d between neighboring polymer matrixes is 3.5 mm, and conveyed to the rear end and then conveyed to the second conveyer belt 202. At the same time, the carbon fibers with a diameter of 5 um is pulled from the fiber reel 102 by the draw-off roller 103, passing through the auxiliary locator 104, and cut into staple fibers with a uniform length of 1 mm by the cutting blade 101. The staple fibers will be vibrated and dispersed by the vibrating conveyer plate 105 and then enter the electrostatic flocking device 3. The high-voltage power supply 302 outputs a step-wave voltage through the positive output terminal to the bottom screen mesh. The specific steps for applying a step electric field are as follows: firstly, an electric field with a voltage of 5 kV is applied, and then the voltage of the electric field is raised to 10 kV after flocking for 5 seconds, and then the voltage of the electric field is raised to 20 kV after flocking for 5 seconds.

[0069] The elastic acrylic polymer matrix is stretched for the speed difference between the first conveyer belt 201 and the second conveyer belt 202, and then conveyed to a top side of the grounded plate 303 through the second conveyer belt 202. The flocking principle is shown in FIG. 2: the carbon staple fibers are polarized and charged, and inserted vertically into the elastic acrylic polymer matrix which is at the top side of the second conveyer belt 202 when they pass through a high potential difference region of the flocking box 301 formed between the bottom screen mesh and the grounded plate 303. As the second conveyer belt 202 exits the high potential difference region, the maximum flocking density is reached, and a vertical-oriented carbon staple fiber array is prepared. An image of such array obtained by SEM (scan electron microscope) is shown in FIG. 3C. The prepared carbon staple fiber array will be conveyed alongwith the second conveyer belt 202 to the third conveyer belt 203, and will be shrunk for the rotary speed difference between the second conveyer belts 202 and the third conveyer belt 203. Subsequently, in the perfusion device 4, components A and B of addition type silicone gel are fully mixed in 1:1 ratio and then poured into the carbon staple fiber array. After being cured and compounded by the thermosetting device 5, a composite thermal conductive pad with highly aligned carbon fiber is prepared.

[0070] The thermal conductivities of the thermal conductive pads prepared by Embodiment 1, Embodiment 2 and Comparative example 1 are tested using ASTM-D5470 as the testing standard.

[0071] The thermal conductivity of the thermal pads obtained in Examples 1 and 2 and Comparative Example 1 was tested, wherein ASTM-D5470 is taken as the detection standard.

TABLE-US-00001 TABLE 1 Thermal conductivities of the thermal conductive pads of Embodiments 1, 2 and Comparative example 1 Thermal conductivity (W/mK) Embodiment 1 14.08 Embodiment 2 22.59 Comparative example 1 10.61

[0072] Combining the data in FIGS. 3A-3C and Table 1, it can be seen that adjusting the speed of the conveyor system to stretch and shrink the flocking polymer matrix to obtain high flocking density, and controlling the output step-wave voltage of the high-voltage power supply can effectively improve the thermal conductivity of the final thermal conductive pads, which has a good application prospect.