Black glass fiber reinforced polypropylene composite material suitable for infrared laser welding and preparation method thereof

Abstract

The invention discloses a black glass fiber reinforced polypropylene composite material suitable for infrared laser welding and a preparation method thereof, and belongs to the technical field of polymer composite materials. The composite material is prepared from the following components in parts by weight: 40-60 parts of polypropylene, 20-40 parts of glass fibers, 1-4 parts of laser-transmitting black color master batches, 2-6 parts of a compatilizer and 0.2-2 parts of an antioxidant. The core innovation of the invention is as follows: firstly, the laser-transmitting black color master batch taking a composite inorganic pigment such as copper chromium manganese black as a coloring agent is selected, and the laser-transmitting black color master batch and a maleic anhydride grafted polypropylene (PP-g-MAH) compatilizer form a synergistic interface system, so that the contradiction between high glass fiber content (up to 40 parts) and high near-infrared laser transmittance is successfully solved; the transmittance of a 2mm sample plate under the wavelength of 980nm is greater than or equal to 20%, and meanwhile, excellent mechanical properties (the tensile strength is greater than 75MPa) are kept; 2, through system optimization, it is determined that the optimal adding amount of the laser-transmitting black color master batch is 2 parts by weight, and the optimal balance of cost and performance is achieved.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials technology, specifically to a black glass fiber reinforced polypropylene (PP) composite material suitable for infrared laser welding and its preparation method. Background Technology

[0002] Laser welding, as a non-contact, energy-saving, and environmentally friendly welding method, boasts advantages such as high bond strength, excellent sealing, low product stress, and high welding precision, and has been widely applied in industries such as automotive, biomedical, and satellite machinery manufacturing. While traditional laser welding of plastics, such as PBT and PA, offers excellent performance, it is also costly. Glass fiber reinforced polypropylene (PP) composites, with their relatively lower cost, have become an ideal alternative.

[0003] However, ordinary black glass fiber reinforced PP materials cannot meet the laser transmittance requirements for laser welding. First, ordinary black colorants (such as carbon black) completely absorb near-infrared lasers, making transmission welding impossible. Second, even if laser-transmitting colorants are used, the laser will be severely scattered under high glass fiber filling, and the poor compatibility between inorganic pigments and the PP matrix can easily lead to a decrease in the mechanical properties of the product and unstable laser transmittance.

[0004] Therefore, developing a black glass fiber reinforced PP composite material that can maintain good mechanical properties and has high and stable infrared laser transmittance has become an urgent technical problem to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a black laser-weldable glass fiber reinforced PP composite material and its preparation method. This composite material exhibits high transmittance (≥20% for a 2mm sample) under 980nm wavelength laser light and maintains stable laser transmittance at high temperatures, while also possessing excellent mechanical properties.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A black glass fiber reinforced polypropylene composite material suitable for infrared laser welding is made of the following components in parts by weight:

[0008] Polypropylene: 40-60 parts;

[0009] Fiberglass: 20-40 parts;

[0010] Laser-transmitting black masterbatch: 1-4 parts;

[0011] Compatibilizer: 2-6 parts;

[0012] Antioxidant: 0.2-2 parts.

[0013] The colorant in the laser-transmitting black masterbatch is a composite inorganic pigment with high transmittance to near-infrared light, preferably copper chromium manganese black or iron chromium manganese black.

[0014] The compatibilizer is maleic anhydride-grafted polypropylene (PP-g-MAH).

[0015] The antioxidant is a hindered phenolic antioxidant.

[0016] The present invention also provides a method for preparing the above-mentioned composite material, comprising the following steps:

[0017] 1. Weigh out polypropylene, laser-transparent black masterbatch, compatibilizer and antioxidant according to the proportion, put them into a high-speed mixer and mix for 3-5 minutes to obtain a premix;

[0018] 2. The premix obtained in step 1 is added from the main feed port of the twin-screw extruder, and glass fiber is added from the side feed port. After melt blending, extrusion, cooling and granulation, the composite material is obtained.

[0019] 3. The extrusion processing temperature of the twin-screw extruder is 170-240℃; the screw speed is 170-400rpm.

[0020] The core innovations of this invention are as follows: First, by selecting a laser-transmitting black masterbatch with composite inorganic pigments such as copper chromium manganese black as colorants, and forming a synergistic interface system with maleic anhydride-grafted polypropylene (PP-g-MAH) compatibilizer, the contradiction between high glass fiber content (up to 40 parts) and high near-infrared laser transmittance is successfully resolved. This results in a 2mm sample exhibiting a transmittance ≥20% at 980nm wavelength, while maintaining excellent mechanical properties (tensile strength >75MPa). Second, through system optimization, the optimal addition amount of the laser-transmitting black masterbatch was determined to be 2 parts by weight, achieving an optimal balance between cost and performance. The composite material prepared by this invention exhibits stable laser transmittance and low cost, making it suitable for component manufacturing in industries such as automotive and medical, where laser welding has stringent requirements.

[0021] The beneficial effects of this invention are:

[0022] 1. High laser transmittance: By selecting a special black masterbatch (such as copper chromium manganese black) with high transmittance to 980nm infrared laser and optimizing its ratio with each component, the laser transmittance of the 2mm thick sample can reach more than 20%, which fully meets the process requirements of laser welding.

[0023] 2. Stable performance: The composite material can maintain stable laser transmittance even at high temperatures, ensuring the consistency and reliability of the welding process.

[0024] 3. Excellent mechanical properties: Through the bridging effect of the compatibilizer, the interfacial compatibility between the laser-transmitting masterbatch, glass fiber and PP matrix is ​​effectively improved, so that the material can obtain high laser transmittance while maintaining excellent mechanical properties such as high tensile strength, flexural strength and impact strength.

[0025] 4. Cost advantage: Using lower-cost PP as the main matrix, it replaces expensive engineering plastics, which significantly reduces product costs while meeting the requirements of laser welding, and has broad market application prospects. Detailed Implementation

[0026] The present invention will be further described below with reference to embodiments, but the scope of protection of the present invention is not limited thereto.

[0027] Raw materials used in the examples and comparative examples:

[0028] PP: Y26, Zhenhai Petrochemical, homopolymer polypropylene.

[0029] Fiberglass: 305G, Chongqing International.

[0030] Compatibilizer: PP-g-MAH, Ningbo Nengzhiguang.

[0031] Antioxidant: CHINOX 850, hindered phenolic antioxidant, double bond chemical.

[0032] Laser-transmitting black masterbatch: a commercial masterbatch with copper chromium manganese black as the colorant.

[0033] Carbon black: ordinary pigment carbon black.

[0034] Examples 1-3

[0035] Weigh each raw material according to the proportions shown in Table 1.

[0036] Preparation method:

[0037] 1. Pour PP, laser-transparent black masterbatch, compatibilizer, and antioxidant into a high-speed mixer and mix for 4 minutes.

[0038] 2. Add the premixed material through the main feed port of the twin-screw extruder, and meter the glass fiber through the side feed port.

[0039] 3. Control the temperature of each section of the twin-screw extruder to be 175℃, 185℃, 195℃, 205℃, 205℃, and 215℃, and the screw speed to be 350 rpm for melt extrusion, cooling, pelletizing, and drying.

[0040] 4. The obtained particles were injection molded into standard test strips and 2mm thick color plates for performance testing. The results are shown in Table 2.

[0041] Comparative Examples 1-5

[0042] Compared with Example 1, the amount of laser-transmitting black masterbatch used in Comparative Example 1 was increased to 3 parts.

[0043] Compared with Example 1, Comparative Example 2 used 2 parts of ordinary carbon black to replace the laser-transmitting black masterbatch.

[0044] Compared with Example 1, the amount of compatibilizer in Comparative Example 3 was increased to 3 parts.

[0045] Compared with Example 1, the amount of laser-transmitting black masterbatch used in Comparative Example 4 was reduced to 1 part.

[0046] Compared with Example 1, the amount of laser-transmitting black masterbatch used in Comparative Example 5 was increased to 4 parts.

[0047] The preparation method is the same as in Example 1, and the performance test results are shown in Table 2.

[0048] Table 1: Formulations of Examples and Comparative Examples (parts by weight)

[0049]

[0050]

[0051] Table 2: Performance Test Results

[0052]

[0053] Results analysis:

[0054] As can be seen from Examples 1-5, the mechanical properties of the material are significantly improved with the increase of glass fiber content, while the laser transmittance decreases accordingly. However, even in Example 3, where the glass fiber content is as high as 40 parts, the laser transmittance is still maintained at 20.8%, which meets the welding requirements.

[0055] Compared with Example 1, Comparative Example 1 showed that increasing the amount of laser-transmitting black masterbatch had little effect on mechanical properties and the improvement in laser transmittance was not significant, indicating that there is an effective and economical range for its content, and excessive addition is unnecessary.

[0056] Comparative Example 2 shows that when ordinary carbon black is used, the laser transmittance is zero, making it completely unsuitable for transmission laser welding, thus proving the necessity of selecting specific laser-transmitting masterbatch in this invention.

[0057] Comparative Example 3 shows that appropriately increasing the amount of compatibilizer can slightly improve mechanical properties, but has little effect on laser transmittance, indicating that the two parts of compatibilizer in this formulation system can meet the basic interfacial compatibility requirements.

[0058] Comparative Example 4 shows that the laser transmittance is only 15.2%, which is lower than the basic welding requirement of 20%, indicating that the content of color masterbatch is too low to meet the requirements of laser welding.

[0059] Comparative Example 5 shows that although its laser transmittance is slightly higher than that of Comparative Example 1, the excessive amount of color masterbatch leads to a slight decrease in mechanical properties and an increase in cost.

[0060] In summary, by selecting specific components and optimizing their dosage, this invention has successfully prepared a black laser-weldable glass fiber reinforced PP composite material that combines high laser transmittance, excellent mechanical properties, and good stability.

Claims

1. A black glass fiber reinforced polypropylene composite material suitable for infrared laser welding, characterized in that, It is made from the following components in parts by weight: Polypropylene: 40-60 parts; Fiberglass: 20-40 parts; Laser-transmitting black masterbatch: 1-4 parts; Compatibilizer: 2-6 parts; Antioxidant: 0.2-2 parts.

2. The black glass fiber reinforced polypropylene composite material suitable for infrared laser welding according to claim 1, characterized in that: The colorant in the laser-transmitting black masterbatch is a composite inorganic pigment with high transmittance to near-infrared light.

3. The black glass fiber reinforced polypropylene composite material suitable for infrared laser welding according to claim 1, characterized in that: The laser-transparent black masterbatch described is copper chromium manganese black or iron chromium manganese black.

4. The black glass fiber reinforced polypropylene composite material suitable for infrared laser welding according to claim 1, characterized in that: The compatibilizer is maleic anhydride-grafted polypropylene (PP-g-MAH).

5. A black glass fiber reinforced polypropylene composite material suitable for infrared laser welding according to claim 1, characterized in that: The antioxidant is a hindered phenolic antioxidant.

6. The black glass fiber reinforced polypropylene composite material suitable for infrared laser welding according to any one of claims 1-5, characterized in that: The present invention also provides a method for preparing the above-mentioned composite material, comprising the following steps: 1) Weigh out polypropylene, laser-transparent black masterbatch, compatibilizer and antioxidant according to the proportion, put them into a high-speed mixer and mix for 3-5 minutes to obtain premix; 2) The premix obtained in step 1 is added from the main feed port of the twin-screw extruder, and glass fiber is added from the side feed port. After melt blending, extrusion, cooling and granulation, the composite material is obtained. 3) The extrusion processing temperature of the twin-screw extruder is 170-240℃; the screw speed is 170-400rpm.

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