PBT (polybutylene terephthalate) composite material as well as preparation method and application thereof

Abstract

The invention relates to a PBT (polybutylene terephthalate) composite material as well as a preparation method and application thereof. The PBT composite material is prepared from the following components in parts by weight: 40 to 55 parts of PBT resin, 1.9 to 5.1 parts of flaky filler, 25 to 35 parts of flat glass fiber and 1.9 to 5.1 parts of epoxy resin. Through cooperation of the flat glass fibers with the specific flatness ratio, the epoxy resin with the specific epoxy equivalent and the flaky filler, the obtained PBT composite material is small in Poisson's ratio, small in Poisson's ratio change at high and low temperatures and good in electric leakage resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer material processing, and more specifically, to a PBT composite material, a preparation method thereof, and an application thereof. Background Art

[0002] In the field of engineering plastics, especially crystalline polyester materials such as polybutylene terephthalate (PBT), due to their excellent electrical properties, mechanical strength, processability, and electrical insulation properties, they are widely used as functional components of electrical components, such as motor housings, relays, connectors, plug sockets, cooling fans, etc. Since these functional components need to provide high load-bearing capacity and vibration characteristics, they are required to have a low Poisson's ratio. On the other hand, when the above functional components are adjusted functionally, the ambient temperature around them may exceed 100 °C. Under the action of high temperature, the Poisson's ratio of the material will change. If the difference in Poisson's ratio between normal temperature and high temperature changes greatly, it will affect the accuracy of functional adjustment, and thus may affect the subsequent operation of the functional components. Therefore, it is necessary to ensure that the difference in Poisson's ratio of the material at different temperatures is small.

[0003] In addition, from the perspectives of short circuit, fire, etc., the leakage resistance performance of the functional components of electrical components also needs to be evaluated, and the current leakage resistance performance of polybutylene terephthalate materials needs to be further improved. Summary of the Invention

[0004] The primary object of the present invention is to overcome the problems of the above existing materials, such as high Poisson's ratio, large difference in Poisson's ratio at different temperatures, and the need for further improvement in leakage resistance performance, and to provide a PBT composite material.

[0005] A further object of the present invention is to provide a preparation method of the above PBT composite material.

[0006] A further object of the present invention is to provide an application of the above PBT composite material in the preparation of functional components of electrical components.

[0007] The above objects of the present invention are achieved by the following technical solutions:

[0008] A PBT composite material, comprising the following components in parts by weight:

[0009]

[0010] The aspect ratio of the flat glass fiber is ≥ 3.5:1; the epoxy equivalent of the epoxy resin is 2500 - 3500 g / eq.

[0011] The inventors of the present invention found through research that by combining flat glass fibers with a specific aspect ratio, epoxy resins with a specific epoxy equivalent, and flake fillers, the obtained PBT composite material has a small Poisson's ratio, a small change in Poisson's ratio at high and low temperatures, and good tracking resistance performance. The reasons are as follows: The glass fibers themselves can play a reinforcing role, and a certain flatness can strengthen the reinforcing effect of the glass fibers in different directions, reducing the longitudinal and transverse strains during the stretching process of the material; the epoxy resin binds the PBT resin and the flat glass fibers more tightly through epoxy functional groups, further playing a positive role in reducing the strain change; the addition of flake fillers can disrupt the arrangement of the flat glass fibers, also playing a positive role in reducing the Poisson's ratio; at the same time, by reducing the longitudinal and transverse strains to reduce the Poisson's ratio, the difference in Poisson's ratio of the PBT composite material at high and low temperatures can also be reduced. In addition, the epoxy resin with a suitable epoxy equivalent enables the flat glass fibers to flow better with the PBT resin during processing, and the flake fillers can reduce the exposure of the flat glass fibers on the surface of the PBT composite material. The combined effects of these two aspects make the surface of the PBT composite material smoother and the CTI value increased.

[0012] If conventional glass fibers (with a circular cross-section) are selected, their reinforcement in different directions when the material is stressed is inconsistent, the Poisson's ratio is large, the difference in Poisson's ratio at high and low temperatures is also large, and they are more likely to be exposed on the surface of the material, resulting in poor tracking resistance performance. If the epoxy equivalent of the epoxy resin is too large and the epoxy content is low, the PBT resin and the flat glass fibers cannot be well combined. If the epoxy equivalent of the epoxy resin is too small, it will cause excessive cross-linking of the PBT resin, reduced fluidity, and poor combination of the glass fibers and the PBT resin. Both will lead to poor performance of the PBT composite material. If other shaped fillers are selected, although they can also reduce the exposure of the flat glass fibers in the material and are helpful to a certain extent in increasing the CTI value, their effect on reducing the Poisson's ratio and the difference in Poisson's ratio at high and low temperatures is significantly inferior to that of flake fillers.

[0013] In the present invention, the PBT resin is used as the main resin, and preferably its content accounts for more than 40 wt% of the PBT composite material.

[0014] In the present invention, the flat glass fiber refers to a glass fiber with an elliptical cross-section, and the aspect ratio refers to the ratio of the longest diameter to the shortest diameter of the ellipse. The aspect ratio of the flat glass fiber can be measured by the optical microscope method, specifically: the longest diameter and the shortest diameter of the cross-sections of 50 flat glass fibers are read by an optical microscope computer with a magnification of 1000 times and a scale scale disk, and the average value is obtained after calculation.

[0015] In the present invention, the aspect ratio of the flat glass fiber can specifically be 3.5:1, 3.6:1, 3.7:1, 3.8:1, 3.9:1, 4.0:1, 4.1:1 or 4.2:1.

[0016] Preferably, the flat glass fiber is an E-glass fiber.

[0017] Preferably, the aspect ratio of the flat glass fiber is 3.5 to 4.2:1.

[0018] If the aspect ratio is further increased, it will affect the Poisson's ratio of the PBT composite material, the change in Poisson's ratio at high and low temperatures, and CTI. By controlling the aspect ratio within the range of 3.5 to 4.2:1, the obtained PBT composite material can have a smaller Poisson's ratio, a smaller change in Poisson's ratio at high and low temperatures, and better leakage resistance performance.

[0019] Preferably, the average minimum diameter of the cross-section of the flat glass fiber is 6 to 10 μm, more preferably 7 to 9 μm.

[0020] In the present invention, the epoxy equivalent of the epoxy resin can specifically be 2500, 2700, 2800, 2900, 3000, 3100, 3200, 3300, or 3500 g / eq. The epoxy equivalent of the epoxy resin of the present invention can be measured according to the method of GB / T4612-2008.

[0021] Preferably, the intrinsic viscosity of the PBT resin is 0.8 to 1.5 dl / g (specifically, it can be 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, or 1.5 dl / g).

[0022] More preferably, the intrinsic viscosity of the PBT resin is 0.82 to 1.25 dl / g.

[0023] Further preferably, the intrinsic viscosity of the PBT resin is 0.82 to 1.10 dl / g.

[0024] When the intrinsic viscosity of the PBT resin is controlled within this range, the PBT composite material has a lower Poisson's ratio and a higher CTI value.

[0025] In the present invention, the intrinsic viscosity of the PBT resin is detected according to Method A (capillary viscometer method) in GB / T14190-2017.

[0026] Preferably, the sheet-like filler is at least one of mica powder, talc powder, or wollastonite.

[0027] Preferably, the average particle size of the sheet-like filler is 2 μm to 20 μm.

[0028] More preferably, the average particle size of the sheet-like filler is 10 μm to 18 μm.

[0029] When the average particle size of the flaky filler is regulated within this range, the properties of the PBT composite material are better.

[0030] In the present invention, the average particle size of the flaky filler can be measured by a particle size analyzer.

[0031] Preferably, the mass ratio of the flat glass fiber to the flaky filler is 5-18:1.

[0032] More preferably, the mass ratio of the flat glass fiber to the flaky filler is 10-15:1.

[0033] When the mass ratio of the flat glass fiber to the flaky filler is regulated within this range, the properties of the obtained PBT composite material are better.

[0034] Preferably, the epoxy resin is at least one of bisphenol A epoxy resin or bisphenol F epoxy resin.

[0035] Preferably, the PBT composite material further comprises 8-15 parts of a flame retardant and 2-4 parts of a flame retardant synergist.

[0036] More preferably, the flame retardant is a brominated flame retardant, and the brominated flame retardant includes but is not limited to at least one of brominated epoxy, brominated polystyrene, brominated polycarbonate, decabromodiphenylethane or pentabromobenzyl acrylate.

[0037] More preferably, the flame retardant synergist is an antimony-containing compound; the antimony-containing compound includes but is not limited to antimony white.

[0038] Preferably, the PBT composite material further comprises 0.3-2 parts of other additives.

[0039] Preferably, the other additives are at least one of a lubricant or an antioxidant.

[0040] Optionally, the lubricant is at least one of aliphatic carboxylic acid esters, erucamide, ethylene bisstearamide, montan esters, polyethylene wax or oxidized polyethylene wax.

[0041] Optionally, the antioxidant is at least one of hindered phenol antioxidants, phosphite antioxidants or organic sulfur antioxidants.

[0042] The preparation method of the above PBT composite material comprises the following steps: mixing the components, melt-extruding, and pelletizing to obtain the PBT composite material.

[0043] Preferably, the temperature of the melt-extrusion is 200-250°C; the screw rotation speed of the extruder for the melt-extrusion is 300-550 revolutions per minute, and the length-diameter ratio of the screw is 30-50:1.

[0044] The application of the above PBT composite material in the preparation of functional components of electrical components is also within the protection scope of the present invention.

[0045] Preferably, the functional component of the electrical component is a relay housing, a fan frame and fan blades of a cooling fan or a connector housing.

[0046] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0047] Through the cooperation of flat glass fibers with a specific aspect ratio, epoxy resins with a specific epoxy equivalent and flaky fillers, the PBT composite material obtained by the present invention has a small Poisson's ratio, a small change in Poisson's ratio at high and low temperatures, and good anti-electric leakage performance. Specific Embodiments

[0048] In order to more clearly and completely describe the technical solution of the present invention, the present invention will be further described in detail below through specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, and various changes can be made within the scope defined by the claims of the present invention.

[0049] Some of the reagents selected in the embodiments and comparative examples of the present invention are described as follows:

[0050] PBT resin 1#: Blue Mountain Tunhe, TH6100, intrinsic viscosity is 1.0 dl / g;

[0051] PBT resin 2#: Blue Mountain Tunhe, TH6082, intrinsic viscosity is 0.82 dl / g;

[0052] PBT resin 3#: Yizheng Chemical Fiber, GL236, intrinsic viscosity is 1.25 dl / g;

[0053] Flame retardant: brominated polystyrene, SR-3010, Shandong Xurui;

[0054] Flame retardant synergist: antimony white, S-05N, Chenzhou Antimony Industry;

[0055] Flat glass fiber 1#: TFG-3.0-T436, aspect ratio 3.5:1, Taishan Fiberglass;

[0056] Flat glass fiber 2#: ECS4F-03-534A, aspect ratio 4.0:1, Jushi Group;

[0057] Flat glass fiber 3#: ECS3F-03-534A, aspect ratio 3.0:1, Jushi Group;

[0058] Ordinary glass fiber 1#: ECS13-4.5-534A, cross-section is circular, average diameter 13 μm, Jushi Group;

[0059] Epoxy resin 1#: YD-019, produced by Guodu Chemical Industry, epoxy equivalent is 2800 g / eq;

[0060] Epoxy resin 2#: YD-019K, produced by Guodu Chemical Industry, epoxy equivalent is 3100 g / eq;

[0061] Epoxy resin 3#: YD-017H, epoxy equivalent is 2200 g / eq;

[0062] Epoxy resin 4#: YD-020, produced by Guodu Chemical Industry, epoxy equivalent is 4000 g / eq;

[0063] Flaky filler 1#: Talc powder, HY-TA05, produced by Shenzhen Haiyang Powder Co., Ltd., particle size D50 is 4.0 μm;

[0064] Flaky filler 2#: Talc powder, HY-TA10, produced by Shenzhen Haiyang Powder Co., Ltd., particle size D50 is 11.2 μm;

[0065] Flaky filler 3#: Mica, GM-6, produced by Anhui Gerui New Material Technology Co., Ltd., particle size D50 is 17.0 μm;

[0066] Other filler 1#: Granular, calcium carbonate, Omya, Omyacarb 5T-JI, particle size D50 is 4.9 μm.

[0067] Other additive 1#: Obtained by mixing antioxidant 1010, antioxidant 168 and pentaerythritol stearate (lubricant) in a mass ratio of 1:1:1. Antioxidant 1010, antioxidant 168 and pentaerythritol stearate are all commercially available products.

[0068] Unless otherwise specified, the components selected in each parallel example and comparative example (such as flame retardants, other additive 1#, etc.) are all the same commercially available products.

[0069] The PBT composites provided in each example and comparative example of the present invention are subjected to performance determination according to the following test methods:

[0070] (1) Poisson's ratio: Using the spline prepared according to the ISO 527-2019 standard, the strain data in the longitudinal and transverse directions of the width surface of the spline is collected by a high-speed vision DIC system. The test temperatures are 23°C and 150°C respectively. The test spline is adjusted for at least 4 hours at the corresponding test temperature. The clamp spacing is 115 mm, the extensometer gauge length is 50 mm, and the test speed is 1 mm / min.

[0071] (2) The Comparative Tracking Index (CTI) is measured according to the IEC 60112-2020 standard. A solution with a conductivity of 395±5 Ω·cm is prepared using ammonium chloride and distilled water or deionized water. The maximum voltage value at which no ignition occurs or the current does not exceed 0.5 A after 50 liquid droplets are dropped is measured using a CTI testing instrument. A 100×100×3.0 mm square plate is used for the test.

[0072] The preparation process of the PBT composites in the examples and comparative examples of the present invention is as follows: First, the PBT resin is dried at 130 °C for 3 hours; then, each component is weighed according to the ratio, mixed, and then melt-extruded and granulated in a twin-screw extruder to obtain the PBT composite. Among them, the temperature of the first zone of the twin-screw extruder is 210 °C, the temperature of the second zone is 210 °C, the temperature of the third zone is 220 °C, the temperature of the fourth zone is 220 °C, the temperature of the fifth zone is 230 °C, the temperature of the sixth zone is 230 °C, the temperature of the seventh zone is 240 °C, the temperature of the eighth zone is 250 °C, the temperature of the ninth zone is 240 °C, the temperature of the die head is 240 °C, the main machine speed is 500 revolutions per minute, and the screw length-diameter ratio is 40:1.

[0073] Examples 1 to 11

[0074] Examples 1 to 11 provide a series of PBT composites, and their formulations are shown in Table 1.

[0075] Table 1 Formulations of Examples 1 to 11 (parts by weight)

[0076]

[0077] Comparative Examples 1 to 7

[0078] Comparative Examples 1 to 7 provide a series of PBT composites, and their formulations are shown in Table 2.

[0079] Table 2 Formulations of Comparative Examples 1 to 7 (parts by weight)

[0080]

[0081]

[0082] The properties of the PBT composites in each example and comparative example are measured according to the above-mentioned test methods, and the test results are shown in Table 3.

[0083] Table 3 Performance test results of the PBT composites in each example and comparative example

[0084]

[0085]

[0086] As can be seen from Table 3:

[0087] The Poisson ratios of the PBT composites of Examples 1 to 11 at 23 °C are all less than or equal to 0.298, the differences in Poisson ratios at 23 °C and 150 °C are all less than or equal to 0.018, and the CTI values are all greater than or equal to 250, indicating that the PBT composites of the present invention have a small Poisson ratio, a small change in Poisson ratio at high and low temperatures, and good leakage resistance performance, and are very suitable for preparing functional components of electrical components with requirements for load-bearing capacity and vibration characteristics.

[0088] The aspect ratio of the flat glass fiber selected in Comparative Example 1 is too small, and the conventional glass fiber is selected in Comparative Example 2. The obtained PBT composite has a large Poisson ratio, a large change in Poisson ratio at high and low temperatures, and the Comparative Example 2 has poor leakage resistance performance. In Comparative Example 3, flat glass fiber is not added, but an equal amount of sheet-shaped filler is used instead. The PBT composite has a large Poisson ratio and a large change in Poisson ratio at high and low temperatures. The epoxy equivalent of the epoxy resin in Comparative Example 4 and Comparative Example 5 is not appropriate, and the properties of the PBT composite are all poor. In Comparative Example 6, sheet-shaped filler is not added, but an equal amount of flat glass fiber is used instead, and the properties of the PBT composite are all poor. In Comparative Example 7, non-sheet-shaped filler is used to replace the sheet-shaped filler, and the PBT composite has a large Poisson ratio and a large change in Poisson ratio at high and low temperatures.

[0089] Obviously, the above-mentioned examples of the present invention are only examples for clearly illustrating the present invention, and are not limitations on the implementation modes of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made on the basis of the above description. It is not necessary and impossible to list all implementation modes here. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A PBT composite material, characterized in that: The composition comprises the following components in parts by weight: The flatness ratio of the flat glass fiber is ≥3.5:1; the epoxy equivalent of the epoxy resin is 2500-3500 g / eq.

2. The PBT composite material according to claim 1, characterized in that: The flatness ratio of the flat glass fiber is 3.5-4.2:

1.

3. The PBT composite material according to claim 1, characterized in that: The intrinsic viscosity of the PBT resin is 0.8 to 1.5 dl / g.

4. The PBT composite material according to claim 1, characterized in that: The flaky filler is at least one of mica powder, talc powder or wollastonite.

5. The PBT composite material according to claim 1, characterized in that: The average particle size of the flake filler is 2 μm to 20 μm.

6. The PBT composite material according to claim 1, characterized in that: The mass ratio of the flat glass fiber to the flake filler is 5 to 18:

1.

7. The PBT composite material according to claim 1, characterized in that: The PBT composite material also includes 8 to 15 parts of a flame retardant and 2 to 4 parts of a flame retardant synergist.

8. The PBT composite material according to claim 1, characterized in that: The PBT composite material also includes 0.3 to 2 parts of other additives.

9. The method for preparing the PBT composite material according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: mixing the components, melt-extruding and granulating to obtain the PBT composite material.

10. Use of the PBT composite material according to any one of claims 1 to 8 in preparing functional parts of electrical components.

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