Radiation modified high flame retardant high strength pbt material and method for preparing the same

Abstract

The application discloses a radiation modified high-flame-retardant high-strength PBT material, which comprises the following components in parts by mass: PBT resin: 30-80 parts, reinforcing fiber: 0-50 parts, crosslinking sensitizer: 0.5-10 parts, stabilizer: 0.5-2 parts, flame retardant: 0-20 parts, antioxidant: 0.1-1 part, and lubricant: 0.1-2 parts. The addition of the flame retardant in the formula can achieve excellent flame-retardant effect with a small amount of the flame retardant, can retain the mechanical strength of the material as much as possible, is beneficial to the realization of thin-wall high-flame-retardant, and can obviously reduce the cost of the material by reducing the amount of the flame retardant. The CTI of the bromine-based flame-retardant system PBT material is obviously improved, and the failure risk of the material in high-humidity or polluted environment is reduced. Compared with a chemical modification mode, the radiation modification is green and environment-friendly, the amount of the flame retardant is reduced, harmful gases such as hydrogen halide are reduced, the requirement of developing green economy is met, and the radiation modification is suitable for large-scale popularization and application in the field of electronic and electrical appliances.

Description

Technical Field

[0001] This invention relates to the field of polymer composite material processing, specifically to a radiation-modified high flame-retardant and high-strength PBT material and its preparation method. Background Technology

[0002] Polybutylene terephthalate (PBT) is one of the five major general-purpose engineering plastics. Most PBT is modified before use. Modified PBT engineering plastics possess excellent mechanical and electrical properties, dimensional stability, ease of processing, and fatigue resistance, making them widely used in the automotive, electronics, and machinery industries. The conventional modification method for PBT is physical melt blending, which can be specifically divided into fiber reinforcement modification, flame retardant modification, and alloy modification. Modification can improve and enhance the mechanical, flame retardant, and electrical properties of PBT materials. However, with technological advancements, the requirements for materials are becoming increasingly stringent, and more demanding requirements are being placed on the performance of PBT materials for certain specific applications or needs.

[0003] PBT is commonly used in the electronics and electrical fields as a key material for manufacturing plastic components such as relays and connectors. When used in these products, PBT must undergo flame-retardant modification. With product upgrades and iterations, the requirements for thin-walled, high-flame-retardant materials have increased. This necessitates the addition of large amounts of flame retardants to the PBT material modification formulation. This not only reduces the mechanical, processing, and long-term performance of PBT materials but also significantly increases material costs due to the high price of flame retardants. Furthermore, when using brominated flame retardants to modify PBT materials, the tracking index (CTI) is relatively low, posing a significant risk when exposed to humid and polluted environments over a long period. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing flame-retardant modification technologies for PBT materials and to provide a radiation-modified high-flame-retardant and high-strength PBT material and its preparation method. A low-flame-retardant PBT material is prepared by conventional physical blending melt extrusion, followed by injection molding and then radiation modification using high-energy rays. Due to the formation of a stable chemical cross-linked structure within the PBT molecule, the flame-retardant and electrical properties of the resin are significantly improved. Only a small amount of flame retardant needs to be added to the formulation to achieve excellent thin-walled, high-flame-retardant effects, while the material still maintains good mechanical strength.

[0005] The above-mentioned objective of this invention is achieved through the following technical solutions: A radiation-modified high flame-retardant and high-strength PBT material, comprising the following raw material components by weight: PBT resin: 30-80 parts Reinforcing fibers: 0-50 parts Crosslinking sensitizer: 0.5-10 parts Stabilizer: 0.5-2 parts Flame retardant: 0-20 parts Antioxidant: 0.1-1 part Lubricant: 0.1-2 parts The intrinsic viscosity of the PBT resin is 0.7-1.2 dL / g, preferably 0.75-1.0 dL / g.

[0006] The reinforcing fiber is selected from at least one of glass fiber, carbon fiber, basalt fiber, and aramid fiber.

[0007] The crosslinking sensitizer is selected from polyvinyl functional group monomers; preferably, it is selected from at least one of triallyl cyanurate, triallyl isocyanurate, trimethylallyl isocyanurate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetraacrylate, and pentaerythritol tetramethacrylate.

[0008] The stabilizer is selected from at least one of di-tert-butyl-p-cresol and p-hydroxyanisole, preferably p-hydroxyanisole.

[0009] The flame retardant is selected from a compound system of bromine-based and synergistic flame retardants, wherein the bromine-based flame retardant is selected from at least one of brominated polystyrene, brominated epoxy resin, decabromodiphenyl ethane, and decabromodiphenyl ether; and the synergistic flame retardant is selected from at least one of antimony trioxide, aluminum hydroxide, and zinc borate.

[0010] The antioxidant is a combination of a primary antioxidant and a secondary antioxidant; the primary antioxidant is selected from at least one of 1098 and 1010; the secondary antioxidant is selected from at least one of 9228, 626, and 168.

[0011] The lubricant is selected from at least one of E wax, silicone powder, and TAF.

[0012] This invention also provides a method for preparing radiation-modified high flame-retardant and high-strength PBT materials, the specific process steps of which include extrusion granulation, injection molding and radiation processing.

[0013] The extrusion granulation is carried out through a twin-screw melt extrusion method. Specifically, PBT resin, flame retardant, antioxidant, and lubricant are mixed evenly using a high-speed mixer and then added to the main feed port. The crosslinking sensitizer and stabilizer are fully mixed and added from the fifth zone side feed port. The reinforcing fibers are added from the eighth zone side feed port. The materials are fed according to the formula, and the temperature of each zone is set to 200~260℃, the screw speed is 200-500rpm, and after melt extrusion, cooling, pelletizing, and drying, PBT composite material particles are obtained.

[0014] The injection molding process involves adding the aforementioned composite material particles into an injection molding machine, setting the temperature of each zone to 210-260℃, the injection pressure to 40-90MPa, and the injection speed to 40-80%, to obtain PBT parts through injection molding.

[0015] The radiation crosslinking is performed by irradiating the PBT component with high-energy rays at a dose of 100-500 kGy. The high-energy rays are selected from gamma rays, electron beams, and X-rays.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1) This invention prepares PBT materials through radiation modification, which can reduce the addition of flame retardants in the formulation. A small amount of flame retardant can achieve excellent flame retardant effect. It not only preserves the mechanical strength of the material as much as possible, but also helps to achieve thin-walled high flame retardancy. In addition, reducing the amount of flame retardant also significantly reduces the cost of the material.

[0017] 2) After radiation, the PBT molecules inside the present invention generate a chemical cross-linking structure, which significantly improves the flame retardancy and electrical properties of the material. In particular, the CTI of the bromine flame retardant PBT material is significantly improved, reducing the risk of material failure when used in high humidity or polluted environments.

[0018] 3) The PBT material of this invention is prepared using conventional extrusion granulation and injection molding methods. Radiation modification is performed after molding, thus not hindering the advantages of PBT material in terms of good processing and easy molding. Compared with chemical modification, radiation modification is green and environmentally friendly, while reducing the amount of flame retardant used and reducing the generation of harmful gases such as hydrogen halides, making it suitable for large-scale application in the electronics and electrical fields. Detailed Implementation

[0019] The following specific embodiments further illustrate the substantive content of the present invention. Operating methods not specifically described in the following embodiments are generally performed under conventional conditions or as recommended by the manufacturer.

[0020] Examples 1-7 The raw material composition of a radiation-modified high flame-retardant and high-strength PBT material, by mass parts, is shown in Table 1.

[0021] Table 1

[0022] Preparation steps and methods of radiation-modified high flame-retardant and high-strength PBT materials in Examples 1-7: First, PBT resin, flame retardant, antioxidant, and lubricant are mixed evenly using a high-speed mixer according to the proportions in Table 1, and then added to the main feed port. The crosslinking sensitizer and stabilizer are thoroughly mixed and added from the fifth zone side feed port. Reinforcing fibers are added from the eighth zone side feed port. Feeding is carried out according to the proportions, with each zone temperature set at 210-250℃ and the screw speed at 300-400 rpm. After melt extrusion, cooling, pelletizing, and drying, PBT composite material particles are obtained. Then, the composite material particles are added to an injection molding machine, with each zone temperature set at 220-250℃, injection pressure at 50-70 MPa, and injection speed at 50-80%. Injection molding yields PBT parts. Finally, the PBT parts are irradiated with gamma rays, with radiation doses shown in Table 1.

[0023] Comparative Examples 1-4 The raw material composition of a modified PBT material, in parts by mass, is shown in Table 1.

[0024] The preparation steps and methods for the modified PBT materials in Comparative Examples 1-4 are the same as those in the Examples.

[0025] Performance Evaluation and Testing The tensile strength, notched impact strength of simply supported beam, flame retardant rating, glow wire flammability index (GWFI), glow wire ignition temperature (GWIT), and comparative tracking index (CTI) of the samples prepared in the above examples and comparative examples were measured. The test results are shown in Table 2.

[0026] Tensile strength: Tested according to GB / T 1040.2 standard, test temperature 23℃, tensile rate 10mm / min; Impact strength of simply supported notched beam: tested according to GB / T 1043.1 standard, test temperature 23℃, impact energy 1J; Flame retardant rating: Tested according to UL 94 standard, thickness 0.4mm; GWFI: Tested according to GB / T 5169.12 standard, thickness 0.8mm; GWIT: Tested according to GB / T 5169.13 standard, thickness 0.8mm; CTI: Tested according to GB / T 4207 standard, thickness 3mm.

[0027] Table 2

[0028] The test results in Table 2 (Examples 1-5) show that the PBT material prepared by radiation modification in this invention only requires the addition of a small amount of flame retardant to achieve excellent thin-walled high flame retardant performance, reaching V-0 flame retardancy at a thickness of 0.4 mm, while maintaining good mechanical and impact strength properties. The CTI value of the radiation-modified brominated flame-retardant PBT material reaches over 300V, a significant improvement over the conventional brominated flame-retardant system's 225V. In particular, the GWIT of the material in Example 6 without added flame retardant reached 775℃, while the GWIT of the conventional non-flame-retardant PBT material was 675℃, indicating that the cross-linking structure generated by radiation modification improves the flame retardant and electrical properties of PBT itself.

[0029] The difference between Comparative Example 1 and the Example is that Comparative Example 1 uses the raw material composition and preparation method of conventional flame-retardant modified PBT. In order to achieve the flame-retardant effect of V-0 level / 0.4mm thin wall, more than 20 parts of flame retardant need to be added. The addition of a large amount of flame retardant significantly reduces the mechanical properties of the material, such as tensile and impact strength.

[0030] The difference between Comparative Example 2 and Example 1 is that Comparative Example 2 was not irradiated. Since no cross-linked structure was formed inside the PBT material, adding only a small amount of flame retardant could not achieve a good flame retardant effect, and the flame retardant level was only V-2.

[0031] The difference between Comparative Example 3 and Example 2 is that the radiation dose of Comparative Example 3 is only 50 kGy. Although the low radiation dose can form a certain cross-linking structure inside the PBT molecule, the degree is low, and the flame retardant grade of the prepared material is V-1.

[0032] The difference between Comparative Example 4 and Example 6 is that Comparative Example 4 did not add a crosslinking sensitizer and was not subjected to radiation treatment. The test results showed that even without the addition of flame retardant to the formulation, the GWFI and GWIT of the radiation-modified PBT material increased by 100°C, while the CTI increased by 125°C.

[0033] The difference between Example 7 and Example 1 lies in the stabilizer. The formula uses p-hydroxyanisole as a stabilizer, resulting in better performance of the radiation-modified PBT material. This is related to the use of a bromine-based flame retardant system in this invention, while a halogen-free flame retardant system has the opposite effect.

[0034] Furthermore, it should be understood that after reading the above description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A radiation-modified high flame-retardant and high-strength PBT material, characterized in that, Based on parts by weight, it contains the following raw material components: PBT resin: 30-80 parts Reinforcing fibers: 0-50 parts Crosslinking sensitizer: 0.5-10 parts Stabilizer: 0.5-2 parts Flame retardant: 0-20 parts Antioxidant: 0.1-1 part Lubricant: 0.1-2 parts.

2. The radiation-modified high flame-retardant and high-strength PBT material according to claim 1, characterized in that, The intrinsic viscosity of the PBT resin is 0.7-1.2 dL / g.

3. The radiation-modified high flame-retardant and high-strength PBT material according to claim 1, characterized in that, The reinforcing fiber is selected from at least one of glass fiber, carbon fiber, basalt fiber, and aramid fiber.

4. The radiation-modified high flame-retardant and high-strength PBT material according to claim 1, characterized in that, The crosslinking sensitizer is selected from polyvinyl functional group monomers; the stabilizer is selected from at least one of di-tert-butyl-p-cresol and p-hydroxyanisole.

5. The radiation-modified high flame-retardant and high-strength PBT material according to claim 1, characterized in that, The flame retardant is selected from a compound system of bromine-based and synergistic flame retardants, wherein the bromine-based flame retardant is selected from at least one of brominated polystyrene, brominated epoxy resin, decabromodiphenyl ethane, and decabromodiphenyl ether; and the synergistic flame retardant is selected from at least one of antimony trioxide, aluminum hydroxide, and zinc borate.

6. The radiation-modified high flame-retardant and high-strength PBT material according to claim 1, characterized in that, The antioxidant is a combination of a primary antioxidant and a secondary antioxidant; the primary antioxidant is selected from at least one of 1098 and 1010; the secondary antioxidant is selected from at least one of 9228, 626, and 168; and the lubricant is selected from at least one of E wax, silicone powder, and TAF.

7. A method for preparing radiation-modified high flame-retardant and high-strength PBT material as described in any one of claims 1 to 6, characterized in that, The specific process steps include extrusion granulation, injection molding, and radiation processing.

8. The method for preparing radiation-modified high flame-retardant and high-strength PBT material according to claim 7, characterized in that, The extrusion granulation is carried out through a twin-screw melt extrusion method. Specifically, PBT resin, flame retardant, antioxidant, and lubricant are mixed evenly using a high-speed mixer and then added to the main feed port. The crosslinking sensitizer and stabilizer are fully mixed and added from the fifth zone side feed port. The reinforcing fibers are added from the eighth zone side feed port. The materials are fed according to the formula, and the temperature of each zone is set to 200~260℃, the screw speed is 200-500rpm, and after melt extrusion, cooling, pelletizing, and drying, PBT composite material particles are obtained.

9. The method for preparing radiation-modified high flame-retardant and high-strength PBT material according to claim 7, characterized in that, The injection molding process involves adding the aforementioned composite material particles into an injection molding machine, setting the temperature of each zone to 210-260℃, the injection pressure to 40-90MPa, and the injection speed to 40-80%, to obtain PBT parts through injection molding.

10. The method for preparing radiation-modified high flame-retardant and high-strength PBT material according to claim 7, characterized in that, The radiation crosslinking is performed by irradiating the PBT component with high-energy rays at a dose of 100-500 kGy. The high-energy rays are selected from gamma rays, electron beams, and X-rays.

Images