Glass fiber reinforced flame-retardant PP material and preparation process thereof

Abstract

The invention relates to the technical field of flame-retardant polypropylene, in particular to a glass fiber reinforced flame-retardant PP material and a preparation process thereof. The glass fiber reinforced flame-retardant PP material is prepared from the following raw materials in parts by mass: 30 to 75 parts of polypropylene, 1 to 3 parts of ethylene-octylene copolymer, 10 to 40 parts of flame retardant, 10 to 50 parts of flame-retardant glass fiber, 1 to 8 parts of compatilizer, 0.1 to 2.0 parts of adsorbent, 0.1 to 2.0 parts of processing aid and 0.1 to 0.5 part of antioxidant, the flame-retardant glass fiber comprises the following raw materials in parts by mass: 5-15 parts of glass fiber, 1-5 parts of tetraethoxysilane, 0.5-1 part of a silane coupling agent and 40-60 parts of a boric acid aqueous solution with the concentration of 0.2-0.6 mol / L. The preparation process is simple, the comprehensive performance of the product is excellent, the problem of poor flame retardance of conventional polypropylene is solved, and the impact resistance and low-temperature toughness of the product can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of flame-retardant polypropylene, in particular to a glass fiber reinforced flame-retardant PP material and a preparation process thereof. Background Art

[0002] Polypropylene (PP) is a thermoplastic resin formed by coordination polymerization of propylene monomers. It features an α-crystal structure and high crystallinity. As one of the five most common plastics, it has a low density and combines excellent chemical resistance, high fatigue resistance, and good processing fluidity. While polypropylene has many advantages, its low oxygen index and flammability significantly limit its application in the electronics, electrical appliances, and automotive sectors.

[0003] In recent years, the country has attached increasing importance to the flame retardancy of plastics, especially for plastic accessories used in industries such as home appliances, aviation, and automobiles, which have put forward different degrees of flame retardancy requirements. However, polypropylene has a low limiting oxygen index and is a flammable material. In vertical burning tests, it often shows the phenomenon of molten droplet combustion. At the same time, polypropylene also has the defects of being brittle and cracking at low temperatures and having poor impact resistance.

[0004] To address these issues, glass fiber reinforcement technology can effectively improve notched impact strength and low-temperature brittleness by introducing glass fibers. However, this technology introduces new technical bottlenecks. Glass fibers can easily lead to reduced melt fluidity. More seriously, the "wick effect" caused by exposed fibers can increase the combustion rate, hindering its application in areas with stringent fire protection requirements. Furthermore, the use of inorganic flame retardants for synergistic modification faces the risk of mechanical property loss due to excessive addition, as well as the environmental risks of halogenated flame retardants.

[0005] Therefore, the development of glass fiber reinforced polypropylene materials with both interface compatibility, flame retardancy and mechanical strength has become a key issue in breaking through the bottleneck of polypropylene applications and needs to be solved urgently. Summary of the Invention

[0006] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a glass fiber reinforced flame retardant PP material and its preparation process.

[0007] A glass fiber reinforced flame retardant PP material, whose raw materials include, by mass, 30-75 parts of polypropylene, 1-3 parts of ethylene-octene copolymer, 10-40 parts of flame retardant, 10-50 parts of flame retardant glass fiber, 1-8 parts of compatibilizer, 0.1-2.0 parts of adsorbent, 0.1-2.0 parts of processing aid, and 0.1-0.5 parts of antioxidant.

[0008] The raw materials of the flame retardant glass fiber include, by mass, 5-15 parts of glass fiber, 1-5 parts of tetraethyl orthosilicate, 0.5-1 part of silane coupling agent KH-550, and 40-60 parts of a boric acid aqueous solution with a concentration of 0.2-0.6 mol / L.

[0009] Preferably, the melt index of the polypropylene is 15-35 g / 10 min.

[0010] Preferably, the flame retardant comprises: ammonium polyphosphate, melamine polyphosphate, and pentaerythritol; the mass ratio of ammonium polyphosphate, melamine polyphosphate, and pentaerythritol is 15-20:3-5:5-10.

[0011] Preferably, the compatibilizer is maleic anhydride grafted polypropylene.

[0012] Preferably, the adsorbent includes at least one of activated carbon, molecular sieve, zeolite powder, and mesoporous silica.

[0013] Preferably, the processing aid is at least one of low molecular weight polyethylene wax, calcium stearate, and vinyl bisstearamide.

[0014] Preferably, the antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and / or tris[2,4-di-tert-butylphenyl]phosphite.

[0015] Preferably, the flame retardant glass fiber is prepared by the following steps: adding glass fiber and ethyl orthosilicate to an ethanol aqueous solution and ultrasonically treating for 10-20 minutes, adjusting the pH value of the system to 4-5, continuing the ultrasonic treatment for 10-20 minutes, adjusting the pH value of the system to 8-9, adding silane coupling agent KH-550 thereto, reflux at 70-80°C for 1-5 hours, cooling to room temperature, vacuum drying, adding to a boric acid aqueous solution, standing at 60-70°C for 2-4 hours, draining, drying, keeping warm at 300-350°C under nitrogen protection for 5-10 minutes, and cooling naturally.

[0016] More preferably, the diameter of a single glass fiber is 5-15 μm.

[0017] More preferably, the ultrasonic treatment frequency is 40-60 kHz.

[0018] The preparation process of the glass fiber reinforced flame retardant PP material comprises the following steps:

[0019] S1. Premix polypropylene, flame retardant, and ethylene-octene copolymer for 2-4 minutes, add compatibilizer, adsorbent, processing aid, and antioxidant, and continue mixing for 1-3 minutes to obtain a premix;

[0020] S2. The premix is fed into the main feed port of the twin-screw extruder, and then the flame-retardant glass fiber is added from the side feed port, and melt-extruded to form pellets.

[0021] Preferably, in S2, the processing temperature of the twin-screw extruder is 190-200°C, the residence time of the mixture in the screw is 1-2 min, and the extrusion pressure is 4-8 MPa.

[0022] Beneficial effects:

[0023] The present invention deposits nano-silica on the surface of glass fiber, aminosilane (KH-550) bonds to the surface hydroxyl groups via amino groups, and boric acid is adsorbed on the surface of the aminosilane layer via hydrogen bonds. During high-temperature treatment, the boric acid is dehydrated to form a boric anhydride (B2O3) deposition layer, which synergistically promotes the densification of the carbon layer with ammonium polyphosphate, resulting in a significant synergistic flame retardant effect. In addition, the nano-silica has good interface stability with the polypropylene matrix, preventing structural damage caused by debonding of the fiber-matrix interface at high temperatures, thereby maintaining the integrity of the carbon layer.

[0024] The invention uses pentaerythritol as a carbonizing agent and ammonium polyphosphate as an acid source and dehydration catalyst. The decomposition generates phosphoric acid to promote the dehydration of pentaerythritol into carbon. Melamine polyphosphate decomposes under heat to release non-combustible gases such as ammonia. The flame-retardant glass fiber and ammonium polyphosphate are compounded to effectively maintain the integrity of the carbon layer. The four cooperate to block heat conduction, hinder heat transfer and oxygen diffusion, and have excellent flame retardant properties.

[0025] The present invention utilizes glass fiber that is processed and compounded with ethylene-octene copolymer to achieve good interface bonding with polypropylene resin, thereby playing the role of reinforcing ribs in the polypropylene matrix, significantly improving the impact resistance and low-temperature toughness of the material, and forming a carbon layer structure in the matrix even in a burning state, thereby further maintaining the mechanical strength of the matrix.

[0026] The present invention not only has a simple preparation process, but also has excellent comprehensive performance of the product. It not only solves the problem of poor flame retardancy of conventional polypropylene, but also improves the impact resistance and low-temperature toughness of the product. Even in the burning state, a carbon layer structure can be compounded on the matrix to further maintain the mechanical strength of the matrix, and is suitable for large-scale promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a comparison chart of the tensile strength, room temperature (23°C) notched impact strength, and -20°C notched impact strength of the glass fiber reinforced flame retardant PP materials obtained in Example 5 and Comparative Examples 1-2.

[0028] Figure 2 This is a comparison chart of the residual carbon rate of the glass fiber reinforced flame retardant PP materials obtained in Example 5 and Comparative Examples 1-2. DETAILED DESCRIPTION

[0029] The present invention will be further explained below with reference to specific embodiments.

[0030] The polypropylene used in the following description is from Yanshan Petrochemical, with the brand name K7726 and a melt index (230°C x 2.16 kg) of 25 g / 10 min.

[0031] The ethylene-octene copolymer used below is from Dow Chemical, USA, with the brand number 8200.

[0032] The maleic anhydride grafted polypropylene used in the following description is from Nengzhiguang and its brand is GPM200A.

[0033] Example 1

[0034] A glass fiber reinforced flame retardant PP material, whose raw materials include: 30g of polypropylene, 1g of ethylene-octene copolymer, 10g of flame retardant, 10g of flame retardant glass fiber, 1g of maleic anhydride grafted polypropylene, 0.1g of activated carbon, 0.1g of polyethylene wax, and 0.1g of tris[2,4-di-tert-butylphenyl]phosphite.

[0035] The flame retardant is composed of ammonium polyphosphate, melamine polyphosphate, and pentaerythritol in a mass ratio of 15:3:5. The flame retardant glass fiber is prepared by the following steps: 5g of glass fiber with a diameter of 5-15μm and 1g of tetraethyl orthosilicate are added to 40g of a 40% ethanol aqueous solution, ultrasonically treated for 10 minutes at a frequency of 40kHz, and the pH value of the system is adjusted to 4-5. The ultrasonic treatment is continued for 10 minutes to adjust the pH value of the system to 8-9. 0.5g of KH-550 coupling agent is added to the solution, and the solution is refluxed at 70°C for 1 hour, cooled to room temperature, vacuum dried, and added to 40g of a 0.2mol / L boric acid aqueous solution. The solution is allowed to stand at 60°C for 2 hours, drained, dried at 80°C, kept at 300°C under nitrogen for 5 minutes, and cooled naturally.

[0036] The preparation process of the glass fiber reinforced flame retardant PP material comprises the following steps:

[0037] S1. Put polypropylene, flame retardant, and ethylene-octene copolymer into a high-speed mixer and premix at a speed of 200 r / min for 3 minutes. Then add maleic anhydride-grafted polypropylene, activated carbon, polyethylene wax, and tris[2,4-di-tert-butylphenyl]phosphite and continue mixing for 1 minute to obtain a premix;

[0038] S2. The premix is fed into the main feed port of a twin-screw extruder, and then flame-retardant glass fiber is added from the side feed port, and melt-extruded into granules; wherein the processing temperature of the twin-screw extruder is 190° C., the residence time of the mixture in the screw is 1 min, and the extrusion pressure is 4 MPa.

[0039] Example 2

[0040] A glass fiber reinforced flame retardant PP material, whose raw materials include: 75g of polypropylene, 3g of ethylene-octene copolymer, 40g of flame retardant, 50g of flame retardant glass fiber, 8g of maleic anhydride grafted polypropylene, 2.0g of molecular sieve, 2.0g of polyethylene wax, and 0.5g of tris[2,4-di-tert-butylphenyl]phosphite.

[0041] The flame retardant is composed of ammonium polyphosphate, melamine polyphosphate, and pentaerythritol in a mass ratio of 4:1:2. The flame retardant glass fiber is prepared by the following steps: 15g of glass fiber with a diameter of 5-15μm and 5g of tetraethyl orthosilicate are added to 60g of a 60% ethanol aqueous solution and ultrasonically treated for 20 minutes at a frequency of 60kHz. The pH value of the system is adjusted to 4-5. The ultrasonic treatment is continued for 20 minutes to adjust the pH value of the system to 8-9. 1g of KH-550 coupling agent is added to the solution, and the mixture is refluxed at 80°C for 5 hours, cooled to room temperature, vacuum dried, added to 60g of a 0.6mol / L boric acid aqueous solution, allowed to stand at 70°C for 4 hours, drained, dried at 100°C, kept at 350°C under nitrogen for 10 minutes, and naturally cooled.

[0042] The preparation process of the glass fiber reinforced flame retardant PP material comprises the following steps:

[0043] S1. Put polypropylene, flame retardant, and ethylene-octene copolymer into a high-speed mixer and premix at 400 r / min for 3 minutes. Then add maleic anhydride-grafted polypropylene, molecular sieves, polyethylene wax, and tris[2,4-di-tert-butylphenyl]phosphite and continue mixing for 3 minutes to obtain a premix;

[0044] S2. The premix is fed into the main feed port of a twin-screw extruder, and then flame-retardant glass fiber is added from the side feed port, and melt-extruded into granules; wherein the processing temperature of the twin-screw extruder is 200°C, the residence time of the mixture in the screw is 2 minutes, and the extrusion pressure is 8 MPa.

[0045] Example 3

[0046] A glass fiber reinforced flame retardant PP material, whose raw materials include: 40g of polypropylene, 2.5g of ethylene-octene copolymer, 20g of flame retardant, 40g of flame retardant glass fiber, 2g of maleic anhydride grafted polypropylene, 1.5g of zeolite powder, 0.5g of calcium stearate, and 0.4g of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

[0047] The flame retardant is composed of ammonium polyphosphate, melamine polyphosphate, and pentaerythritol in a mass ratio of 17:4.5:7. The flame retardant glass fiber is prepared by the following steps: 12g of glass fiber with a diameter of 5-15μm and 2g of tetraethyl orthosilicate are added to 55g of a 45% ethanol aqueous solution and ultrasonically treated for 18 minutes at a frequency of 45kHz. The pH value of the system is adjusted to 4-5. The ultrasonic treatment is continued for 18 minutes to adjust the pH value of the system to 8-9. 0.7g of KH-550 coupling agent is added to the solution, and the solution is refluxed at 77°C for 2 hours, cooled to room temperature, vacuum dried, and added to 55g of a 0.3mol / L boric acid aqueous solution. The solution is allowed to stand at 66°C for 2.5 hours, drained, dried at 95°C, kept at 310°C under nitrogen for 9 minutes, and cooled naturally.

[0048] The preparation process of the glass fiber reinforced flame retardant PP material comprises the following steps:

[0049] S1. Put polypropylene, flame retardant, and ethylene-octene copolymer into a high-speed mixer and premix at a speed of 250 r / min for 3 minutes. Then add maleic anhydride-grafted polypropylene, zeolite powder, calcium stearate, and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and continue mixing for 2 minutes to obtain a premix;

[0050] S2. The premix is fed into the main feed port of a twin-screw extruder, and then flame-retardant glass fiber is added from the side feed port, and melt-extruded into granules; wherein the processing temperature of the twin-screw extruder is 198° C., the residence time of the mixture in the screw is 1.5 min, and the extrusion pressure is 5 MPa.

[0051] Example 4

[0052] A glass fiber reinforced flame retardant PP material, whose raw materials include: 65g of polypropylene, 1.5g of ethylene-octene copolymer, 30g of flame retardant, 20g of flame retardant glass fiber, 6g of maleic anhydride grafted polypropylene, 0.5g of zeolite powder, 1.5g of calcium stearate, and 0.2g of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

[0053] The flame retardant is composed of ammonium polyphosphate, melamine polyphosphate, and pentaerythritol in a mass ratio of 19:3.5:9. The flame retardant glass fiber is prepared by the following steps: 8g of glass fiber with a diameter of 5-15μm and 4g of tetraethyl orthosilicate are added to 45g of a 55% ethanol aqueous solution, ultrasonically treated for 12 minutes at a frequency of 55kHz, and the pH value of the system is adjusted to 4-5. The ultrasonic treatment is continued for 12 minutes to adjust the pH value of the system to 8-9. 0.9g of KH-550 coupling agent is added thereto, and the mixture is refluxed at 73°C for 4 hours, cooled to room temperature, vacuum dried, and added to 45g of a 0.5mol / L boric acid aqueous solution. The mixture is allowed to stand at 64°C for 3.5 hours, drained, dried at 85°C, kept at 330°C under nitrogen for 7 minutes, and cooled naturally.

[0054] The preparation process of the glass fiber reinforced flame retardant PP material comprises the following steps:

[0055] S1. Put polypropylene, flame retardant, and ethylene-octene copolymer into a high-speed mixer and premix at 350 r / min for 3 min. Then add maleic anhydride-grafted polypropylene, zeolite powder, calcium stearate, and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and continue mixing for 2 min to obtain a premix.

[0056] S2. The premix is fed into the main feed port of a twin-screw extruder, and then flame-retardant glass fiber is added from the side feed port, and melt-extruded into granules; wherein the processing temperature of the twin-screw extruder is 192° C., the residence time of the mixture in the screw is 1.5 min, and the extrusion pressure is 7 MPa.

[0057] Example 5

[0058] A glass fiber reinforced flame retardant PP material, whose raw materials include: 50g of polypropylene, 2g of ethylene-octene copolymer, 25g of flame retardant, 30g of flame retardant glass fiber, 4g of maleic anhydride grafted polypropylene, 1g of mesoporous silica, 1g of vinyl bisstearamide, and 0.3g of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

[0059] The flame retardant is composed of ammonium polyphosphate, melamine polyphosphate, and pentaerythritol in a mass ratio of 9:2:4. The flame retardant glass fiber is prepared by the following steps: 10g of glass fiber with a diameter of 5-15μm and 3g of tetraethyl orthosilicate are added to 50g of a 50% ethanol aqueous solution, ultrasonically treated for 15 minutes at a frequency of 50kHz, and the pH value of the system is adjusted to 4-5. The ultrasonic treatment is continued for 15 minutes to adjust the pH value of the system to 8-9. 0.8g of KH-550 coupling agent is added to the solution, and the solution is refluxed at 75°C for 3 hours, cooled to room temperature, vacuum dried, and added to 50g of a 0.4mol / L boric acid aqueous solution. The solution is allowed to stand at 65°C for 3 hours, drained, dried at 90°C, kept at 320°C under nitrogen for 8 minutes, and cooled naturally.

[0060] The preparation process of the glass fiber reinforced flame retardant PP material comprises the following steps:

[0061] S1. Put polypropylene, flame retardant, and ethylene-octene copolymer into a high-speed mixer and premix at 300 r / min for 3 min. Then add maleic anhydride-grafted polypropylene, mesoporous silica, vinyl bisstearamide, and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and continue mixing for 2 min to obtain a premix;

[0062] S2. The premix is fed into the main feed port of a twin-screw extruder, and then flame-retardant glass fiber is added from the side feed port, and melt-extruded into granules; wherein the processing temperature of the twin-screw extruder is 195° C., the residence time of the mixture in the screw is 1.5 min, and the extrusion pressure is 6 MPa.

[0063] Comparative Example 1

[0064] A glass fiber reinforced flame retardant PP material, whose raw materials include: 50g of polypropylene, 2g of ethylene-octene copolymer, 25g of flame retardant, 30g of flame retardant glass fiber, 4g of maleic anhydride grafted polypropylene, 1g of mesoporous silica, 1g of vinyl bisstearamide, and 0.3g of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

[0065] The flame retardant is composed of ammonium polyphosphate, melamine polyphosphate, and pentaerythritol in a mass ratio of 9:2:4. The flame-retardant glass fiber is prepared by the following steps: 10g of glass fiber with a diameter of 5-15μm and 3g of tetraethyl orthosilicate are added to 50g of a 50% ethanol aqueous solution, ultrasonically treated for 15 minutes at a frequency of 50kHz, and the pH value of the system is adjusted to 4-5. The ultrasonic treatment is continued for 15 minutes to adjust the pH value of the system to 8-9. 0.8g of KH-550 coupling agent is added to the solution, and the mixture is refluxed at 75°C for 3 hours, cooled to room temperature, and vacuum dried.

[0066] The preparation process of the glass fiber reinforced flame retardant PP material comprises the following steps:

[0067] S1. Put polypropylene, flame retardant, and ethylene-octene copolymer into a high-speed mixer and premix at 300 r / min for 3 min. Then add maleic anhydride-grafted polypropylene, mesoporous silica, vinyl bisstearamide, and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and continue mixing for 2 min to obtain a premix;

[0068] S2. The premix is fed into the main feed port of a twin-screw extruder, and then flame-retardant glass fiber is added from the side feed port, and melt-extruded into granules; wherein the processing temperature of the twin-screw extruder is 195° C., the residence time of the mixture in the screw is 1.5 min, and the extrusion pressure is 6 MPa.

[0069] Comparative Example 2

[0070] A glass fiber reinforced flame retardant PP material, whose raw materials include: 50g of polypropylene, 2g of ethylene-octene copolymer, 25g of flame retardant, 30g of flame retardant glass fiber, 4g of maleic anhydride grafted polypropylene, 1g of mesoporous silica, 1g of vinyl bisstearamide, and 0.3g of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

[0071] The flame retardant is composed of melamine polyphosphate and pentaerythritol in a mass ratio of 2:4. The flame retardant glass fiber is prepared by the following steps: 10g of glass fiber with a diameter of 5-15μm and 3g of tetraethyl orthosilicate are added to 50g of a 50% ethanol aqueous solution, ultrasonically treated for 15 minutes at a frequency of 50kHz, and the pH value of the system is adjusted to 4-5. The ultrasonic treatment is continued for 15 minutes to adjust the pH value of the system to 8-9. 0.8g of KH-550 coupling agent is added to the solution, and the solution is refluxed at 75°C for 3 hours, cooled to room temperature, vacuum dried, and added to 50g of a 0.4mol / L boric acid aqueous solution. The solution is allowed to stand at 65°C for 3 hours, drained, dried at 90°C, kept at 320°C under nitrogen for 8 minutes, and cooled naturally.

[0072] The preparation process of the glass fiber reinforced flame retardant PP material comprises the following steps:

[0073] S1. Put polypropylene, flame retardant, and ethylene-octene copolymer into a high-speed mixer and premix at 300 r / min for 3 min. Then add maleic anhydride-grafted polypropylene, mesoporous silica, vinyl bisstearamide, and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and continue mixing for 2 min to obtain a premix;

[0074] S2. The premix is fed into the main feed port of a twin-screw extruder, and then flame-retardant glass fiber is added from the side feed port, and melt-extruded into granules; wherein the processing temperature of the twin-screw extruder is 195° C., the residence time of the mixture in the screw is 1.5 min, and the extrusion pressure is 6 MPa.

[0075] Mechanical properties of the glass fiber reinforced flame retardant PP materials obtained in Example 5 and Comparative Examples 1-2 were compared and tested as follows: The tensile strength of the glass fiber reinforced flame retardant PP materials obtained in Example 5 and Comparative Examples 1-2 was tested with reference to GB / T 1040.2-2022, "Determination of Tensile Properties of Plastics - Part 2: Test Conditions for Molded and Extruded Plastics." The notched impact strength at room temperature (23°C) and notched impact strength at -20°C of the glass fiber reinforced flame retardant PP materials obtained in Example 5 and Comparative Examples 1-2 were tested with reference to GB / T 1843-2008, "Plastics - Determination of Izod Impact Strength."

[0076] like Figure 1 As shown, the tensile strength and notched impact strength of the glass fiber reinforced flame retardant PP materials obtained in Example 5 and Comparative Example 2 are significantly higher than those in Comparative Example 1 (P < 0.05), but there is no significant difference between the glass fiber reinforced flame retardant PP materials obtained in Example 5 and Comparative Example 2 (P > 0.05).

[0077] The flame retardant properties of the glass fiber reinforced flame retardant PP materials obtained in Example 5 and Comparative Examples 1-2 were tested, and the results are shown in Table 1:

[0078] Table 1 Flame retardant properties of glass fiber reinforced flame retardant PP materials obtained in Example 5 and Comparative Examples 1-2

[0079] project Test Method Example 5 Comparative Example 1 Comparative Example 2 Flame retardant (3.2mm) UL-94 V-0 V-1 V-1 Oxygen index ASTM D2863 35 30 32

[0080] It can be seen from Table 1 that the flame retardant performance of the glass fiber reinforced flame retardant PP material obtained in Example 5 is better than that of Comparative Examples 1-2.

[0081] The glass fiber reinforced flame retardant PP materials obtained in Example 5 and Comparative Examples 1-2 were tested with reference to GB / T 27761-2011 "Test method for weight loss and residual amount by thermogravimetric analyzer". The temperature was raised to 650°C at a constant rate of 20°C / min under a nitrogen atmosphere, and the residual carbon rate of each group of samples was measured.

[0082] like Figure 2 As shown, the glass fiber-reinforced flame-retardant PP material obtained in Example 5 had the highest carbon residue rate, significantly better than Comparative Examples 1-2 (P < 0.05). This confirms that all three materials can form a dense and stable carbon layer at high temperatures to achieve a flame retardant effect, and the glass fiber-reinforced flame-retardant PP material obtained in Example 5 has the best flame retardant effect.

[0083] Testing was conducted in accordance with GB / T 5169.13-2013, "Fire hazard testing for electrical and electronic products - Part 13: Glow-wire / hot-wire basic test methods - Glow-wire ignition temperature (GWIT) test for materials." A glow-wire was applied to the polypropylene recycled material samples (2 mm) obtained in Example 5 and Comparative Examples 1-2 at the required temperature for 30 seconds. The glow-wire was then removed and the GWIT values were observed and recorded. The GWIT values for Example 5 were greater than 960°C, while those for Comparative Examples 1 and 2 were 750°C and 820°C, respectively.

[0084] The applicant believes that this is because the present invention utilizes glass fiber after treatment and compounded with ethylene-octene copolymer, so that it has good interface bonding with polypropylene resin, which can play the role of reinforcing ribs in the polypropylene matrix, significantly improving the impact resistance and low-temperature toughness of the material. Even in the burning state, it can be compounded in the matrix to form a carbon layer structure, which can further maintain the mechanical strength of the matrix. At the same time, the present invention deposits nano-silica on the surface of the glass fiber, aminosilane (KH-550) bonds with the surface hydroxyl group through the amino group, and boric acid is adsorbed on the surface of the aminosilane layer through hydrogen bonding; when treated at high temperature, the boric acid dehydrates to form a boric anhydride (B2O3) deposition layer, which synergistically promotes the densification of the carbon layer with ammonium polyphosphate, and has a significant synergistic flame retardant effect. In addition, the interface stability with the polypropylene matrix is good, preventing structural damage caused by debonding of the fiber-matrix interface at high temperature, thereby maintaining the integrity of the carbon layer. However, the present invention uses pentaerythritol as a carbonizing agent and ammonium polyphosphate as an acid source and dehydration catalyst. The decomposition produces phosphoric acid to promote the dehydration of pentaerythritol into carbon. Melamine polyphosphate decomposes when heated to release non-combustible gases such as ammonia. The flame-retardant glass fiber and ammonium polyphosphate are compounded to effectively maintain the integrity of the carbon layer. The four work together to block heat conduction, hinder heat transfer and oxygen diffusion, and have excellent flame retardant properties.

[0085] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A glass fiber reinforced flame retardant PP material, characterized in that: The raw materials include, by mass: 30-75 parts of polypropylene, 1-3 parts of ethylene-octene copolymer, 10-40 parts of flame retardant, 10-50 parts of flame retardant glass fiber, 1-8 parts of compatibilizer, 0.1-2.0 parts of adsorbent, 0.1-2.0 parts of processing aid, and 0.1-0.5 parts of antioxidant; The raw materials of the flame retardant glass fiber include, by mass, 5-15 parts of glass fiber, 1-5 parts of tetraethyl orthosilicate, 0.5-1 part of silane coupling agent, and 40-60 parts of 0.2-0.6 mol / L boric acid aqueous solution.

2. The glass fiber reinforced flame retardant PP material according to claim 1, characterized in that: The melt index of polypropylene is 15-35 g / 10 min.

3. The glass fiber reinforced flame retardant PP material according to claim 1, characterized in that the flame retardant include: Ammonium polyphosphate, melamine polyphosphate, pentaerythritol; the mass ratio of ammonium polyphosphate, melamine polyphosphate, pentaerythritol is 15-20:3-5:5-10.

4. The glass fiber reinforced flame retardant PP material according to claim 1, characterized in that: The compatibilizer is maleic anhydride grafted polypropylene.

5. The glass fiber reinforced flame retardant PP material according to claim 1, characterized in that: Adsorbents include: At least one of activated carbon, molecular sieve, zeolite powder, and mesoporous silica.

6. The glass fiber reinforced flame retardant PP material according to claim 1, characterized in that: The processing aid is at least one of low molecular polyethylene wax, calcium stearate and vinyl bisstearamide.

7. The glass fiber reinforced flame retardant PP material according to claim 1, characterized in that: The antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and / or tris[2,4-di-tert-butylphenyl]phosphite.

8. The glass fiber reinforced flame retardant PP material according to claim 1, characterized in that: The flame-retardant glass fiber is prepared by the following steps: adding glass fiber and ethyl orthosilicate to an ethanol aqueous solution and ultrasonically treating the solution for 10-20 minutes, adjusting the pH value of the system to 4-5, continuing the ultrasonic treatment for 10-20 minutes, adjusting the pH value of the system to 8-9, adding a silane coupling agent, refluxing at 70-80°C for 1-5 hours, cooling to room temperature, vacuum drying, adding the solution to a boric acid aqueous solution, standing at 60-70°C for 2-4 hours, draining, drying, keeping the temperature at 300-350°C for 5-10 minutes under nitrogen protection, and naturally cooling.

9. The glass fiber reinforced flame retardant PP material according to claim 8, characterized in that: The ultrasonic treatment frequency was 40-60 kHz.

10. A process for preparing the glass fiber reinforced flame retardant PP material according to any one of claims 1 to 9, characterized in that: The steps include: S1. Premix polypropylene, flame retardant, and ethylene-octene copolymer for 2-4 minutes, add compatibilizer, adsorbent, processing aid, and antioxidant, and continue mixing for 1-3 minutes to obtain a premix; S2. The premix is fed into the main feed port of the twin-screw extruder, and then the flame-retardant glass fiber is added from the side feed port, and melt-extruded to form pellets.

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