High-transparency black fiberglass reinforced PBT composite material and preparation method thereof

Abstract

The application discloses a kind of high light transmission welding black glass fiber reinforced PBT composite material and preparation method thereof, belong to high polymer composite material technical field.The composite material is by weight fraction, including: PBT resin 64~70 parts, alkali-free chopped glass fiber 29~33 parts, special near-infrared light transmission black color masterbatch 2.5~4.5 parts, light scattering inhibitor 0.4~0.9 parts, interface compatibility agent 0.6~1.0 parts, laser welding aid 0.3~0.7 parts, composite antioxidant 0.2~0.6 parts, processing lubricant 0.3~0.7 parts.The application is by preferred matrix resin, modified glass fiber, special colorant and multiple auxiliary agent compound, combined with optimization preparation process, so that the light transmittance of material is greater than 55% at 1.5mm thickness, 980nm wavelength, tensile strength is greater than 120MPa, strength retention rate is greater than 80% after laser welding, appearance is pure black uniform, and processing performance is excellent, can be widely used in electronic appliances, automobile sensing, optical communication, laser welding precision parts and other fields.

Description

Technical Field

[0001] This invention belongs to the field of polymer composite material technology, specifically relating to a glass fiber reinforced polybutylene terephthalate (PBT) composite material that combines a black appearance, near-infrared high light transmittance, high mechanical strength and excellent laser welding performance, as well as a method for preparing the material. Background Technology

[0002] Polybutylene terephthalate (PBT), one of the five major general-purpose engineering plastics, possesses excellent mechanical properties, heat resistance, electrical insulation, chemical corrosion resistance, and good processing flowability. PBT-GF30 material, modified with 30% glass fiber reinforcement, exhibits significantly improved mechanical strength, dimensional stability, and heat deformation resistance, and is widely used in precision structural components, sensor accessories, electronic housings, and other fields.

[0003] With the technological iteration in the electronics and automotive industries, high-end precision components place higher demands on PBT-GF30 materials: on the one hand, they need to possess both a pure black appearance and near-infrared light transmittance to adapt to 980nm wavelength laser sensing and signal transmission scenarios, requiring a light transmittance greater than 55% at a thickness of 1.5mm; on the other hand, they need to possess high strength and high toughness, with a tensile strength greater than 120MPa and a notched impact strength greater than 8.5kJ / m. 2 In addition, it must have excellent laser welding performance, with a strength retention rate of more than 80% after welding.

[0004] However, existing black PBT-GF30 materials cannot simultaneously meet the above requirements. Conventional carbon black colorants have a strong blocking effect on near-infrared light, resulting in a transmittance of less than 15% at 980nm wavelength at a thickness of 1.5mm; ordinary modified materials have poor interfacial compatibility and many internal defects, making it difficult to meet mechanical properties. During laser welding, problems such as weak fusion and stress cracking are prone to occur, and the weld strength retention rate is far below 80%.

[0005] Although there are reports on black transparent PBT materials in existing technologies, most of them focus on the visible light band, and there is little research on high glass fiber reinforced systems with near-infrared transmittance of 980nm. Moreover, they generally have defects such as insufficient mechanical properties and poor laser welding compatibility, making it difficult to meet the needs of high-end applications. Summary of the Invention

[0006] The present invention aims to overcome the shortcomings of the prior art and provide a black glass fiber reinforced PBT composite material with high light transmittance, high strength and high laser welding performance and its preparation method, so as to solve the comprehensive shortcomings of traditional materials in terms of near-infrared light transmittance, mechanical properties and laser welding performance.

[0007] The present invention achieves the above objectives through the following technical solutions: A high-transmittance, weld-resistant black glass fiber reinforced PBT composite material, comprising the following components by weight: PBT resin: 64-70 parts; Alkali-free chopped glass fiber: 29-33 parts; Special near-infrared transparent black masterbatch: 2.5~4.5 parts; Light scattering inhibitor: 0.4~0.9 parts; Interface compatibilizer: 0.6~1.0 parts; Laser welding additive: 0.3~0.7 parts; Compound antioxidant: 0.2~0.6 parts; Processing lubricant: 0.3~0.7 parts; The composite material, at a thickness of 1.5 mm, exhibits a light transmittance greater than 55% at a wavelength of 980 nm, a tensile strength greater than 120 MPa, and a notched impact strength of a simply supported beam greater than 8.5 kJ / m. 2 The strength retention rate after laser welding is greater than 80%.

[0008] Furthermore, the intrinsic viscosity of the PBT resin is 0.90~1.05 dL / g, and the end carboxyl group content is ≤25 mol / t.

[0009] Furthermore, the alkali-free chopped glass fiber has a diameter of 9~12μm and a length of 4~7mm, and its surface is pretreated with a silane-titanium ester composite coupling agent.

[0010] Furthermore, in the dedicated near-infrared transparent black masterbatch, the colorant is a compound system of organic black dye and inorganic black pigment, with a compounding ratio of 9~12:1.

[0011] Furthermore, the light scattering inhibitor is a mixture of acrylate light diffusion modifier and surface-modified nano-silica at a mass ratio of 1:1.2; the interface compatibilizer is maleic anhydride-grafted PBT compatibilizer with a grafting rate ≥1.2%.

[0012] Furthermore, the laser welding additive is a near-infrared absorbing compound additive that can absorb 980nm laser energy and promote the fusion bonding of the welding interface.

[0013] Furthermore, the composite antioxidant is a mixture of hindered phenolic antioxidant and phosphite antioxidant in a mass ratio of 1:2.5; the processing lubricant is a mixture of stearate ester and silicone lubricant in a mass ratio of 1:1.

[0014] The present invention also provides a method for preparing the above-mentioned composite material, comprising the following steps: (1) Raw material pretreatment: Place the PBT resin in a vacuum drying oven and dry it at 125~135℃ for 4.5~6.5 hours until the moisture content is ≤0.02%; (2) Premixing: Weigh the dried PBT resin, special near-infrared transparent black masterbatch, light scattering inhibitor, interface compatibilizer, laser welding aid, composite antioxidant and processing lubricant according to the weight parts, add them to the high-speed mixer, stir at 900~1100r / min for 6~9 minutes at room temperature, mix evenly to obtain the premix; (3) Melt extrusion granulation: The premixed material is added to the main feed hopper of the twin-screw extruder, and the alkali-free short-cut glass fiber is added to the melting zone of the middle section of the extruder through the side feeding device; the temperature of each section of the extruder is controlled at 225~250℃, and the screw speed is 260~320r / min; after the material is melt plasticized, dispersed and blended, it is extruded through the die head, water-cooled and shaped, and air-dried and granulated to obtain composite material particles; (4) Drying the finished product: Place the obtained particles in a vacuum drying oven again and dry them at 125°C for 3.5 hours to remove residual moisture. Seal and store to obtain the finished product.

[0015] Beneficial effects Compared with the prior art, the present invention has the following beneficial effects: Excellent near-infrared transmittance: Through the synergistic effect of a dedicated near-infrared transmittance black coloring system, fine-diameter modified glass fiber and light scattering suppression technology, the material has a transmittance of more than 55% at a wavelength of 980nm with a thickness of 1.5mm, which meets the requirements of laser sensing and signal transmission. Excellent mechanical properties: Through the optimization of the bonding between glass fiber and matrix using an interfacial compatibilizer, the material exhibits a tensile strength greater than 120 MPa and a notched impact strength greater than 8.5 kJ / m. 2 To meet the requirements for the use of high-strength structural components; Excellent laser welding performance: The introduction of laser welding additives significantly improves the fusion quality of the welding interface, and the strength retention rate after welding is greater than 80%, ensuring the reliability and sealing of the welded structure; Good appearance and stability: The material has a pure black and uniform appearance, without whitening, color difference or other problems. It has excellent aging resistance and stable performance over long-term use. High process adaptability: The preparation process is simple, requires no special equipment, is suitable for large-scale industrial production, and can be widely used in fields such as electronics, automotive sensing, optical communication, and laser welding of precision parts. Detailed Implementation

[0016] The present invention will be further described in detail below with reference to specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the invention. Both the embodiments and comparative examples use the following general preparation process, with only adjustments made to the component ratios, raw material selection, or process parameters. Performance testing methods are as follows: Transmittance at 980nm wavelength: Tested using a UV-NIR spectrophotometer on a 1.5mm thick injection-molded sheet; Tensile strength: Tested according to GB / T 1040 standard; Notched impact strength of simply supported beams: tested according to GB / T 1043 standard; Laser welding strength retention rate: The ratio of the tensile strength of the weld to the original tensile strength after laser welding of the sample. Heat distortion temperature: tested according to GB / T 1634 standard (1.8MPa); Volume resistivity: tested according to GB / T 1410 standard.

[0017] 1. General preparation method (1) Raw material pretreatment: Place the PBT resin in a vacuum drying oven and dry it at 125-135℃ for 4.5-6.5 hours until the moisture content is ≤0.02%; (2) Premixing: Weigh the dried PBT resin, special near-infrared transparent black masterbatch, light scattering inhibitor, interface compatibilizer, laser welding aid, composite antioxidant and processing lubricant according to the weight parts, add them to the high-speed mixer, stir at 900-1100 r / min for 6-9 minutes at room temperature, mix evenly to obtain the premix; (3) Melt extrusion granulation: The premixed material is added to the main feed hopper of the twin-screw extruder, and the alkali-free short-cut glass fiber is added to the melting zone of the middle section of the extruder through the side feeding device; the temperature of each section of the extruder is set according to the specific embodiment, and the screw speed is set according to the specific embodiment; after the material is melt-plasticized, dispersed and blended, it is extruded through the die head, water-cooled and shaped, and air-dried and granulated to obtain composite material particles; (4) Drying the finished product: Place the obtained particles in a vacuum drying oven again and dry them at 125°C for 3.5 hours to remove residual moisture. Seal and store to obtain the finished product.

[0018] 2. Example Example 1

[0019] Raw material ratio (parts by weight): PBT resin (intrinsic viscosity 0.98 dL / g, end carboxyl group content 20 mol / t): 67 parts Alkali-free chopped glass fibers (10 μm in diameter, 4.5 mm in length, pretreated with silane-titanium ester composite coupling agent): 30 parts Special near-infrared transparent black masterbatch (organic black dye: inorganic black pigment = 10:1): 3.5 parts Light scattering inhibitor (acrylate: nano silica = 1:1.2): 0.6 parts Interface compatibilizer (maleic anhydride grafted PBT, grafting rate 1.3%): 0.8 parts Laser welding additive (near-infrared absorption type compound additive): 0.5 parts Compound antioxidant (hindered phenol: phosphite = 1:2.5): 0.4 parts Processing lubricant (stearate:silicone = 1:1): 0.5 parts Preparation steps: PBT resin was vacuum dried at 130℃ for 5.5h; high-speed mixing was performed for 8min at a speed of 1000r / min; the twin-screw extruder temperature was 230-245℃, the screw speed was 290r / min, and glass fiber was side-fed; after extrusion granulation, the particles were vacuum dried at 125℃ for 3.5h. Example 2

[0020] Raw material ratio: PBT resin (intrinsic viscosity 0.95 dL / g): 66 parts Alkali-free chopped glass fiber: 31 parts Special near-infrared transparent black masterbatch: 4.0 parts Light scattering inhibitor: 0.7 parts Interface compatibilizer: 0.9 parts Laser welding flux: 0.6 parts Compound antioxidant: 0.45 parts Processing lubricant: 0.6 parts Preparation steps: Extrusion temperature 235-250℃, screw speed 300r / min, the rest are the same as in Example 1.

[0021] Example 3 (Lower Limit Combination) Raw material ratio: PBT resin (intrinsic viscosity 0.90 dL / g): 70 parts Alkali-free chopped glass fiber: 29 parts Special near-infrared transparent black masterbatch: 2.5 parts Light scattering inhibitor: 0.4 parts Interface compatibilizer: 0.6 parts Laser welding flux: 0.3 parts Compound antioxidant: 0.2 parts Processing lubricant: 0.3 parts Preparation steps: Extrusion temperature 225-240℃, screw speed 260r / min, the rest are the same as in Example 1.

[0022] Example 4 (Upper Limit Combination) Raw material ratio: PBT resin (intrinsic viscosity 1.05 dL / g): 64 parts Alkali-free chopped glass fiber: 33 parts Special near-infrared transparent black masterbatch: 4.5 parts Light scattering inhibitor: 0.9 parts Interface compatibilizer: 1.0 part Laser welding flux: 0.7 parts Compound antioxidant: 0.6 parts Processing lubricant: 0.7 parts Preparation steps: Extrusion temperature 240-250℃, screw speed 320r / min, the rest are the same as in Example 1.

[0023] Example 5 (Another intermediate point) Raw material ratio: PBT resin (intrinsic viscosity 1.00 dL / g): 68 parts Alkali-free chopped glass fiber: 30 parts Special near-infrared transparent black masterbatch: 3.0 parts Light scattering inhibitor: 0.5 parts Interface compatibilizer: 0.7 parts Laser welding flux: 0.4 parts Compound antioxidant: 0.3 parts Processing lubricant: 0.4 parts Preparation steps: Extrusion temperature 230-240℃, screw speed 280r / min, the rest are the same as in Example 1.

[0024] 3. Comparative Example Comparative Example 1 (Conventional Carbon Black Coloring) The conventional PBT-GF30 black material was used, and the colorant was ordinary carbon black (3.5 parts). No interface compatibilizer or laser welding aid was added. The remaining components were the same as in Example 1, and the preparation process was the same as in Example 1.

[0025] Comparative Example 2 (without laser welding additives) The process is basically the same as in Example 1, except that no laser welding additive is added. The other components and processes are the same as in Example 1.

[0026] Comparative Example 3 (Special color masterbatch replaced with carbon black) The special near-infrared transparent black masterbatch in Example 1 was replaced with an equal amount of ordinary carbon black masterbatch, and the remaining components and processes were the same as in Example 1.

[0027] Comparative Example 4 (without light scattering inhibitors) The process is basically the same as in Example 1, except that no light scattering inhibitor is added. The other components and processes are the same as in Example 1.

[0028] Comparative Example 5 (without interfacial compatibilizer) It is basically the same as Example 1, except that no interface compatibilizer is added, and the other components and processes are the same as in Example 1.

[0029] Comparative Example 6 (Ordinary glass fiber, without composite treatment) The alkali-free chopped glass fibers in Example 1 were replaced with ordinary glass fibers of the same specifications but without pretreatment with composite coupling agent. The remaining components and processes were the same as in Example 1.

[0030] Comparative Example 7 (Excessive Laser Welding Additives) The process is basically the same as in Example 1, except that the amount of laser welding flux is increased to 1.5 parts, and the other components and processes are the same as in Example 1.

[0031] Comparative Example 8 (Extrusion temperature too low) The process is basically the same as in Example 1, except that the extrusion temperature is set to 210-220℃ (lower than the lower limit of the present invention), and the rest of the process is the same as in Example 1.

[0032] Comparative Example 9 (Extrusion temperature too high) The process is basically the same as in Example 1, except that the extrusion temperature is set to 255-265℃ (higher than the upper limit of the present invention), and the rest of the process is the same as in Example 1.

[0033] Comparative Example 10 (Screw speed too low) The process is basically the same as in Example 1, except that the screw speed is set to 200 r / min (lower than the lower limit of the present invention), and the rest of the process is the same as in Example 1.

[0034] Comparative Example 11 (Screw speed too high) It is basically the same as Example 1, but the screw speed is set to 350 r / min (higher than the upper limit of the present invention), and the rest of the process is the same as Example 1.

[0035] Performance test results The materials prepared in the above embodiments and comparative examples were injection molded into standard samples and their performance was tested. The results are summarized in the table below: Results Analysis and Discussion The test results above show that: All properties of Examples 1-5 meet the objectives of the invention: transmittance at 980nm wavelength >55% at a thickness of 1.5mm, tensile strength >120MPa, and notched impact strength >8.5kJ / m. 2 Laser welding strength retention rate >80%, heat distortion temperature >210℃, volume resistivity >1.0×10⁻⁶16 The Ω·cm value and the uniform, pure black appearance indicate that the technical solution of this invention can stably achieve excellent performance over a wide range of compositions and processes.

[0036] The transmittance of Comparative Example 1 (conventional carbon black) and Comparative Example 3 (special masterbatch replaced with carbon black) decreased sharply (<16%), proving that the special near-infrared transparent black masterbatch is the key to achieving high transmittance.

[0037] The weld retention rate of Comparative Example 2 (without laser welding additive) dropped to 72.5%, which is below the 80% threshold, indicating that laser welding additive is indispensable for improving weld strength.

[0038] Comparative Example 4 (without light scattering inhibitor) had a light transmittance of 48.7% and a slightly whitish appearance, indicating that the light scattering inhibitor plays an important role in suppressing scattering and improving light transmittance uniformity.

[0039] Comparative Example 5 (without interfacial compatibilizer) showed a significant decrease in tensile strength and impact strength, demonstrating the contribution of the interfacial compatibilizer to mechanical properties.

[0040] Comparative Example 6 (ordinary glass fiber) showed a decrease in both mechanical properties and light transmittance, indicating that glass fiber pretreated with composite coupling agent is crucial for interfacial bonding and light scattering suppression.

[0041] Comparative Example 7 (excessive laser welding additive) resulted in decreased light transmittance and yellowing of the appearance, indicating that the amount of additive used needs to be controlled within a reasonable range.

[0042] Comparative Examples 8-11 verified the boundaries of the process parameters: Too low a temperature (<225℃) leads to poor plasticization and a general decline in performance; too high a temperature (>250℃) causes yellowing and degradation; too low a rotation speed (<260 r / min) results in poor dispersion; and too high a rotation speed (>320 r / min) causes shear overheating. This demonstrates that the process parameter range defined in this invention is a necessary condition for ensuring performance.

[0043] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A high-transmittance, weld-resistant black glass fiber reinforced PBT composite material, characterized in that, The composite material, by weight, comprises the following components: 64-70 parts PBT resin, 29-33 parts alkali-free chopped glass fiber, 2.5-4.5 parts special near-infrared transparent black masterbatch, 0.4-0.9 parts light scattering inhibitor, 0.6-1.0 parts interface compatibilizer, 0.3-0.7 parts laser welding aid, 0.2-0.6 parts composite antioxidant, and 0.3-0.7 parts processing lubricant. The composite material, at a thickness of 1.5 mm, exhibits a light transmittance greater than 55% at a wavelength of 980 nm, a tensile strength greater than 120 MPa, and a notched impact strength of a simply supported beam greater than 8.5 kJ / m². 2 The strength retention rate after laser welding is greater than 80%.

2. The high-transmittance, weld-resistant black glass fiber reinforced PBT composite material according to claim 1, characterized in that, The intrinsic viscosity of the PBT resin is 0.90–1.05 dL / g, and the end carboxyl group content is ≤25 mol / t.

3. The high-transmittance, weld-resistant black glass fiber reinforced PBT composite material according to claim 1, characterized in that, The alkali-free chopped glass fibers have a diameter of 9–12 μm and a length of 4–7 mm, and their surface is pretreated with a silane-titanium ester composite coupling agent.

4. The high-transmittance, weld-resistant black glass fiber reinforced PBT composite material according to claim 1, characterized in that, In the aforementioned special near-infrared transparent black masterbatch, the colorant is a compound system of organic black dye and inorganic black pigment, with a compounding ratio of 9 to 12:

1.

5. The high-transmittance, weld-resistant black glass fiber reinforced PBT composite material according to claim 1, characterized in that, The light scattering inhibitor is a mixture of acrylate light diffusion modifier and surface-modified nano-silica at a mass ratio of 1:1.2; the interface compatibilizer is maleic anhydride-grafted PBT compatibilizer with a grafting rate ≥1.2%.

6. The high-transmittance, weld-resistant black glass fiber reinforced PBT composite material according to claim 1, characterized in that, The laser welding additive is a near-infrared absorption type compound additive.

7. The high-transmittance, weld-resistant black glass fiber reinforced PBT composite material according to claim 1, characterized in that, The composite antioxidant is a mixture of hindered phenolic antioxidant and phosphite antioxidant in a mass ratio of 1:2.5; the processing lubricant is a mixture of stearate and silicone lubricant in a mass ratio of 1:

1.

8. A method for preparing the high-transmittance, weld-resistant black glass fiber reinforced PBT composite material as described in any one of claims 1 to 7, characterized in that, Includes the following steps: (1) Raw material pretreatment: PBT resin was vacuum dried at 125-135℃ for 4.5-6.5 hours until the moisture content was ≤0.02%; (2) Premixing: Weigh the dried PBT resin, special near-infrared transparent black masterbatch, light scattering inhibitor, interface compatibilizer, laser welding aid, composite antioxidant and processing lubricant according to the weight parts, and stir them in a high-speed mixer at 900-1100 r / min for 6-9 minutes at room temperature until they are evenly mixed to obtain the premix. (3) Melt extrusion granulation: The premixed material is added to the main feed hopper of the twin-screw extruder, and the alkali-free short-cut glass fiber is added to the melting zone of the middle section of the extruder through the side feeding device; the temperature of each section of the extruder is controlled at 225-250℃, and the screw speed is 260-320r / min; after the material is melt-plasticized, dispersed and blended, it is extruded through the die head, water-cooled and shaped, air-dried and granulated to obtain composite material particles; (4) Drying of finished product: The obtained particles are vacuum dried at 125°C for 3.5 hours to remove residual moisture, and then sealed and stored to obtain the finished product.

9. The preparation method according to claim 8, characterized in that, In step (3), the screw speed of the twin-screw extruder is 260-320 r / min and the extrusion temperature is 225-250℃.

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