Glass fiber reinforced flame retardant PP material and preparation process thereof

Abstract

The application 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 raw materials of the glass-fiber-reinforced flame-retardant PP material include the following in parts by mass: 30-75 parts of polypropylene, 1-3 parts of ethylene-octene copolymer, 10-40 parts of a flame retardant, 10-50 parts of flame-retardant glass fiber, 1-8 parts of a compatilizer, 0.1-2.0 parts of an adsorbent, 0.1-2.0 parts of a processing aid and 0.1-0.5 parts of an antioxidant. The raw materials of the flame-retardant glass fiber include the following in parts by mass: 5-15 parts of glass fiber, 1-5 parts of tetraethyl orthosilicate, 0.5-1 part of a silane coupling agent and 40-60 parts of a boric acid aqueous solution with a concentration of 0.2-0.6 mol / L. The application has the advantages of simple preparation process, excellent comprehensive performance of the product, solved problem of poor flame retardancy of conventional polypropylene and improved impact resistance and low-temperature toughness of the product.

Description

Technical Field

[0001] This invention relates to the field of flame-retardant polypropylene technology, and in particular to a glass fiber reinforced flame-retardant PP material and its preparation process. Background Technology

[0002] Polypropylene (PP) is a thermoplastic resin formed by coordination polymerization of propylene monomers, characterized by its α-crystalline form and high crystallinity. As one of the five major general-purpose plastics, it has low density and possesses excellent chemical resistance, high fatigue resistance, and good processing flowability. Although polypropylene has many advantages, its low oxygen index and flammability significantly limit its applications in the electronics, electrical appliances, and automotive industries.

[0003] In recent years, the country has paid increasing attention to the flame retardancy of plastics, especially for plastic parts used in industries such as household 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 exhibits the phenomenon of molten droplets aiding combustion. At the same time, polypropylene also has defects such as being brittle at low temperatures and having poor impact resistance.

[0004] To address the aforementioned issues, glass fiber reinforcement technology, by introducing glass fibers, can effectively improve notched impact strength and low-temperature brittleness. However, glass fiber reinforcement introduces new technical bottlenecks. Glass fibers can easily lead to decreased melt flowability, and more seriously, the "wick effect" formed by exposed fibers can increase the burning rate, creating application obstacles in fields with stringent fire resistance requirements. Furthermore, using inorganic flame retardants for synergistic modification faces challenges such as mechanical property loss due to excessive addition and the environmental risks associated with halogenated flame retardants.

[0005] Therefore, developing glass fiber reinforced polypropylene materials that combine interfacial compatibility, flame retardancy, and mechanical strength has become a key issue in overcoming the bottlenecks in polypropylene applications and urgently needs to be addressed. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by proposing a glass fiber reinforced flame-retardant PP material and its preparation process.

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

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

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

[0010] Preferably, the flame retardant includes: 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 bis-stearamide.

[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: glass fiber and tetraethyl orthosilicate are added to an ethanol aqueous solution and ultrasonically treated for 10-20 minutes. The pH of the system is adjusted to 4-5, and ultrasonic treatment is continued for 10-20 minutes. The pH of the system is adjusted to 8-9. Silane coupling agent KH-550 is added to the solution, and the mixture is refluxed at 70-80°C for 1-5 hours. After cooling to room temperature, the mixture is vacuum dried. The solution is then added to a boric acid aqueous solution and allowed to stand at 60-70°C for 2-4 hours. The solution is drained, dried, and kept at 300-350°C for 5-10 minutes under nitrogen protection. The solution is then allowed to cool naturally.

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

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

[0018] The preparation process of the above-mentioned glass fiber reinforced flame-retardant PP material includes the following steps:

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

[0020] S2. Feed the premixed material into the main feed port of the twin-screw extruder, and then add the flame-retardant glass fiber from the side feed port for melt extrusion granulation.

[0021] Preferably, in S2, the processing temperature of the twin-screw extruder is 190-200℃, 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] This invention deposits nano-silica on the surface of glass fiber. Aminosilane (KH-550) is bonded to the surface hydroxyl groups through amino groups, while boric acid is adsorbed on the surface of the aminosilane layer through hydrogen bonds. During high-temperature treatment, boric acid dehydrates to form a boric anhydride (B2O3) deposition layer, which synergistically promotes the densification of the char layer with ammonium polyphosphate. The synergistic flame retardant effect is significant, and the interfacial stability with the polypropylene matrix is ​​good, preventing structural damage caused by fiber-matrix interface debonding at high temperatures, thereby maintaining the integrity of the char layer.

[0024] This invention uses pentaerythritol as a char-forming agent and ammonium polyphosphate as an acid source and dehydration catalyst. The decomposition produces phosphoric acid, which promotes the dehydration and char formation of pentaerythritol. Melamine polyphosphate decomposes upon heating to release non-combustible gases such as ammonia. The combination of flame-retardant glass fiber and ammonium polyphosphate effectively maintains the integrity of the char layer. The four components work together to block heat conduction, hinder heat transfer and oxygen diffusion, resulting in excellent flame-retardant performance.

[0025] This invention utilizes treated glass fiber compounded with ethylene-octene copolymer to achieve good interfacial bonding with polypropylene resin. This allows it to act as a reinforcing rib in the polypropylene matrix, significantly improving the material's impact resistance and low-temperature toughness. Even in a combustion state, it can form a carbon layer structure in the matrix, further maintaining the mechanical strength of the matrix.

[0026] This invention not only has a simple preparation process, but also produces products with excellent overall performance. It solves the problem of poor flame retardancy of conventional polypropylene, and can also improve the impact resistance and low-temperature toughness of the products. Even in the combustion state, it can form a carbon layer structure in the matrix, which can further maintain the mechanical strength of the matrix, making it suitable for large-scale promotion and application. Attached Figure Description

[0027] Figure 1 The graph shows a comparison 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 The graph shows a comparison of the char residue of the glass fiber reinforced flame-retardant PP materials obtained in Example 5 and Comparative Examples 1-2. Detailed Implementation

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

[0030] The polypropylene used below is sourced from Yanshan Petrochemical, grade K7726, with a melt index (230℃×2.16kg) of 25g / 10min.

[0031] The ethylene-octene copolymer used below is sourced from Dow Chemical Company, USA, and its brand name is 8200.

[0032] The maleic anhydride-grafted polypropylene used below is sourced from Nengzhiguang, with the brand name GPM200A.

[0033] Example 1

[0034] A glass fiber reinforced flame-retardant PP material, the raw materials of which include: 30g polypropylene, 1g ethylene-octene copolymer, 10g flame retardant, 10g flame-retardant glass fiber, 1g maleic anhydride grafted polypropylene, 0.1g activated carbon, 0.1g polyethylene wax, and 0.1g 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 using 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% (w / w) aqueous ethanol solution and ultrasonically treated for 10min at a frequency of 40kHz. The pH of the system is adjusted to 4-5, and ultrasonic treatment is continued for another 10min, adjusting the pH to 8-9. 0.5g of KH-550 coupling agent is added, and the mixture is refluxed at 70℃ for 1h, cooled to room temperature, and vacuum dried. The mixture is then added to 40g of a 0.2mol / L aqueous boric acid solution, allowed to stand at 60℃ for 2h, drained, dried at 80℃, and held at 300℃ for 5min under nitrogen protection, followed by natural cooling.

[0036] The preparation process of the above-mentioned glass fiber reinforced flame-retardant PP material includes the following steps:

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

[0038] S2. The premixed material is fed into the main feed port of the twin-screw extruder, and then flame-retardant glass fiber is added from the side feed port for melt extrusion granulation. The processing temperature of the twin-screw extruder is 190℃, the residence time of the mixture in the screw is 1min, and the extrusion pressure is 4MPa.

[0039] Example 2

[0040] A glass fiber reinforced flame-retardant PP material, the raw materials of which include: 75g polypropylene, 3g ethylene-octene copolymer, 40g flame retardant, 50g flame-retardant glass fiber, 8g maleic anhydride-grafted polypropylene, 2.0g molecular sieve, 2.0g polyethylene wax, and 0.5g 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 using 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% (w / w) aqueous ethanol solution and ultrasonically treated for 20min at a frequency of 60kHz. The pH of the system is adjusted to 4-5, and ultrasonic treatment is continued for another 20min, adjusting the pH to 8-9. 1g of KH-550 coupling agent is added, and the mixture is refluxed at 80℃ for 5h. After cooling to room temperature, it is vacuum dried and then added to 60g of a 0.6mol / L aqueous boric acid solution. The mixture is allowed to stand at 70℃ for 4h, drained, and dried at 100℃. Under nitrogen protection, it is held at 350℃ for 10min and then allowed to cool naturally.

[0042] The preparation process of the above-mentioned glass fiber reinforced flame-retardant PP material includes the following steps:

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

[0044] S2. The premixed material is fed into the main feed port of the twin-screw extruder, and then flame-retardant glass fiber is added from the side feed port for melt extrusion granulation. The processing temperature of the twin-screw extruder is 200℃, the residence time of the mixture in the screw is 2min, and the extrusion pressure is 8MPa.

[0045] Example 3

[0046] A glass fiber reinforced flame-retardant PP material, the raw materials of which include: 40g polypropylene, 2.5g ethylene-octene copolymer, 20g flame retardant, 40g flame-retardant glass fiber, 2g maleic anhydride-grafted polypropylene, 1.5g zeolite powder, 0.5g calcium stearate, and 0.4g 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 using 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% (w / w) aqueous ethanol solution and ultrasonically treated for 18min at a frequency of 45kHz. The pH of the system is adjusted to 4-5, and ultrasonic treatment is continued for another 18min, adjusting the pH to 8-9. 0.7g of KH-550 coupling agent is added, and the mixture is refluxed at 77℃ for 2h, cooled to room temperature, and vacuum dried. The mixture is then added to 55g of a 0.3mol / L aqueous boric acid solution, allowed to stand at 66℃ for 2.5h, drained, dried at 95℃, and held at 310℃ for 9min under nitrogen protection, followed by natural cooling.

[0048] The preparation process of the above-mentioned glass fiber reinforced flame-retardant PP material includes the following steps:

[0049] S1. Add polypropylene, flame retardant, and ethylene-octene copolymer to a high-speed mixer and premix at 250 r / min for 3 min. 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 the premix.

[0050] S2. The premixed material is fed into the main feed port of the twin-screw extruder, and then flame-retardant glass fiber is added from the side feed port for melt extrusion granulation. The processing temperature of the twin-screw extruder is 198℃, the residence time of the mixture in the screw is 1.5min, and the extrusion pressure is 5MPa.

[0051] Example 4

[0052] A glass fiber reinforced flame-retardant PP material, the raw materials of which include: 65g polypropylene, 1.5g ethylene-octene copolymer, 30g flame retardant, 20g flame-retardant glass fiber, 6g maleic anhydride-grafted polypropylene, 0.5g zeolite powder, 1.5g calcium stearate, and 0.2g 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 using 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% (w / w) aqueous ethanol solution and ultrasonically treated for 12 minutes at a frequency of 55kHz. The pH of the system is adjusted to 4-5, and ultrasonic treatment is continued for another 12 minutes, adjusting the pH to 8-9. 0.9g of KH-550 coupling agent is added, and the mixture is refluxed at 73℃ for 4 hours. After cooling to room temperature, it is vacuum dried and then added to 45g of a 0.5mol / L aqueous boric acid solution. The mixture is allowed to stand at 64℃ for 3.5 hours, drained, and dried at 85℃. Under nitrogen protection, it is held at 330℃ for 7 minutes and then allowed to cool naturally.

[0054] The preparation process of the above-mentioned glass fiber reinforced flame-retardant PP material includes the following steps:

[0055] S1. Add polypropylene, flame retardant, and ethylene-octene copolymer to a high-speed mixer and premix at 350 r / min for 3 min. 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 the premix.

[0056] S2. The premixed material is fed into the main feed port of the twin-screw extruder, and then flame-retardant glass fiber is added from the side feed port for melt extrusion granulation. The processing temperature of the twin-screw extruder is 192℃, the residence time of the mixture in the screw is 1.5min, and the extrusion pressure is 7MPa.

[0057] Example 5

[0058] A glass fiber reinforced flame-retardant PP material, the raw materials of which include: 50g polypropylene, 2g ethylene-octene copolymer, 25g flame retardant, 30g flame-retardant glass fiber, 4g maleic anhydride-grafted polypropylene, 1g mesoporous silica, 1g vinyl bis-stearamide, and 0.3g 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 using 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% (w / w) aqueous ethanol solution and ultrasonically treated for 15min at a frequency of 50kHz. The pH of the system is adjusted to 4-5, and ultrasonic treatment is continued for another 15min, adjusting the pH to 8-9. 0.8g of KH-550 coupling agent is added, and the mixture is refluxed at 75℃ for 3h, cooled to room temperature, and vacuum dried. The mixture is then added to 50g of a 0.4mol / L aqueous boric acid solution, allowed to stand at 65℃ for 3h, drained, dried at 90℃, and held at 320℃ for 8min under nitrogen protection, followed by natural cooling.

[0060] The preparation process of the above-mentioned glass fiber reinforced flame-retardant PP material includes the following steps:

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

[0062] S2. The premixed material is fed into the main feed port of the twin-screw extruder, and then flame-retardant glass fiber is added from the side feed port for melt extrusion granulation. The processing temperature of the twin-screw extruder is 195℃, the residence time of the mixture in the screw is 1.5min, and the extrusion pressure is 6MPa.

[0063] Comparative Example 1

[0064] A glass fiber reinforced flame-retardant PP material, the raw materials of which include: 50g polypropylene, 2g ethylene-octene copolymer, 25g flame retardant, 30g flame-retardant glass fiber, 4g maleic anhydride-grafted polypropylene, 1g mesoporous silica, 1g vinyl bis-stearamide, and 0.3g 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 using 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% (w / w) aqueous ethanol solution and ultrasonically treated for 15min at a frequency of 50kHz. The pH of the system is adjusted to 4-5, and ultrasonic treatment is continued for another 15min, adjusting the pH to 8-9. 0.8g of KH-550 coupling agent is added, and the mixture is refluxed at 75℃ for 3h, cooled to room temperature, and then vacuum dried.

[0066] The preparation process of the above-mentioned glass fiber reinforced flame-retardant PP material includes the following steps:

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

[0068] S2. The premixed material is fed into the main feed port of the twin-screw extruder, and then flame-retardant glass fiber is added from the side feed port for melt extrusion granulation. The processing temperature of the twin-screw extruder is 195℃, the residence time of the mixture in the screw is 1.5min, and the extrusion pressure is 6MPa.

[0069] Comparative Example 2

[0070] A glass fiber reinforced flame-retardant PP material, the raw materials of which include: 50g polypropylene, 2g ethylene-octene copolymer, 25g flame retardant, 30g flame-retardant glass fiber, 4g maleic anhydride-grafted polypropylene, 1g mesoporous silica, 1g vinyl bis-stearamide, and 0.3g 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 using 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% (w / w) aqueous ethanol solution and ultrasonically treated for 15min at a frequency of 50kHz. The pH of the system is adjusted to 4-5, and ultrasonic treatment is continued for another 15min, adjusting the pH to 8-9. 0.8g of KH-550 coupling agent is added, and the mixture is refluxed at 75℃ for 3h. After cooling to room temperature, it is vacuum dried and then added to 50g of a 0.4mol / L aqueous boric acid solution. The mixture is allowed to stand at 65℃ for 3h, drained, and dried at 90℃. Under nitrogen protection, it is kept at 320℃ for 8min and then naturally cooled.

[0072] The preparation process of the above-mentioned glass fiber reinforced flame-retardant PP material includes the following steps:

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

[0074] S2. The premixed material is fed into the main feed port of the twin-screw extruder, and then flame-retardant glass fiber is added from the side feed port for melt extrusion granulation. The processing temperature of the twin-screw extruder is 195℃, the residence time of the mixture in the screw is 1.5min, and the extrusion pressure is 6MPa.

[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 according 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 according to GB / T1843-2008 "Determination of cantilever beam impact strength of plastics".

[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 methods Example 5 Comparative Example 1 Comparative Example 2 Flame retardancy (3.2mm) UL-94 V-0 V-1 V-1 Oxygen Index ASTM D2863 35 30 32

[0080] As shown in Table 1, the flame retardant properties of the glass fiber reinforced flame retardant PP material obtained in Example 5 are better than those 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 according to GB / T 27761-2011 "Test Method for Weight Loss and Residual Amount of Thermogravimetric Analyzer". The residual char rate of each group of samples was measured by heating to 650°C at a uniform rate of 20°C / min under a nitrogen atmosphere.

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

[0083] The tests were conducted according to GB / T 5169.13-2013 "Fire Hazard Testing for Electrical and Electronic Products - Part 13: Glow Wire / Hot Wire Basic Test Method - Glow Wire Ignition Temperature (GWIT) Test of Materials". At the required temperature, a glow wire was applied to the polypropylene recycled material samples (2 mm) obtained in Example 5 and Comparative Examples 1-2 for 30 seconds, after which the glow wire was removed, and the results were observed and recorded. The ignition temperature (GWIT) of Example 5 was greater than 960°C, while that of Comparative Examples 1 and 2 was 750°C and 820°C, respectively.

[0084] The applicant believes that this invention utilizes treated glass fibers compounded with ethylene-octene copolymers, resulting in excellent interfacial bonding with polypropylene resin. This allows the glass fibers to act as reinforcing ribs within the polypropylene matrix, significantly improving the material's impact resistance and low-temperature toughness. Even during combustion, a char layer structure can be formed within the matrix, further maintaining the matrix's mechanical strength. Simultaneously, this invention deposits nano-silica on the glass fiber surface. Aminosilane (KH-550) bonds to surface hydroxyl groups via amino groups, while boric acid is adsorbed onto the aminosilane layer surface via hydrogen bonds. During high-temperature treatment, boric acid dehydrates to form a boric anhydride (B2O3) deposition layer, which synergistically promotes char layer densification with ammonium polyphosphate, resulting in a significant synergistic flame-retardant effect. Furthermore, the good interfacial stability with the polypropylene matrix prevents structural damage caused by fiber-matrix interface debonding at high temperatures, thus maintaining the integrity of the char layer. In this invention, pentaerythritol is used as a char-forming agent and ammonium polyphosphate is used as an acid source and dehydration catalyst. The decomposition produces phosphoric acid, which promotes the dehydration and char formation of pentaerythritol. Melamine polyphosphate decomposes upon heating to release non-combustible gases such as ammonia. The flame-retardant glass fiber and ammonium polyphosphate are combined to effectively maintain the integrity of the char layer. The four components work together to block heat conduction, hinder heat transfer and oxygen diffusion, resulting in excellent flame-retardant performance.

[0085] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A glass fiber reinforced flame-retardant PP material, characterized in that, The raw materials, by weight, include: 30-75 parts polypropylene, 1-3 parts ethylene-octene copolymer, 10-40 parts flame retardant, 10-50 parts flame retardant glass fiber, 1-8 parts compatibilizer, 0.1-2.0 parts adsorbent, 0.1-2.0 parts processing aid, and 0.1-0.5 parts antioxidant. Flame retardants include: ammonium polyphosphate, melamine polyphosphate, and pentaerythritol; the mass ratio of ammonium polyphosphate, melamine polyphosphate, and pentaerythritol is 15-20:3-5:5-10. The processing aid is at least one of low molecular weight polyethylene wax, calcium stearate, and vinyl bis-stearamide; The raw materials for flame-retardant glass fiber, by weight, include: 5-15 parts glass fiber, 1-5 parts tetraethyl orthosilicate, 0.5-1 part silane coupling agent, and 40-60 parts boric acid aqueous solution with a concentration of 0.2-0.6 mol / L. Flame-retardant glass fiber is prepared by the following steps: glass fiber and tetraethyl orthosilicate are added to an ethanol aqueous solution and ultrasonically treated for 10-20 minutes. The pH of the system is adjusted to 4-5, and ultrasonic treatment is continued for 10-20 minutes. The pH of the system is adjusted to 8-9, a silane coupling agent is added, and the mixture is refluxed at 70-80℃ for 1-5 hours. After cooling to room temperature, the mixture is vacuum dried and then added to a boric acid aqueous solution. The mixture is allowed to stand at 60-70℃ for 2-4 hours, drained, dried, and then kept at 300-350℃ for 5-10 minutes under nitrogen protection. Finally, the mixture is allowed to cool naturally.

2. The glass fiber reinforced flame-retardant PP material according to claim 1, characterized in that, The melt flow 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 compatibilizer is maleic anhydride-grafted polypropylene.

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

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

6. The glass fiber reinforced flame-retardant PP material according to claim 1, characterized in that, The ultrasonic treatment frequency is 40-60kHz.

7. A preparation process for a glass fiber reinforced flame-retardant PP material as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Premix polypropylene, flame retardant, and ethylene-octene copolymer for 2-4 minutes, then add compatibilizer, adsorbent, processing aid, and antioxidant and continue mixing for 1-3 minutes to obtain the premix. S2. Feed the premixed material into the main feed port of the twin-screw extruder, and then add the flame-retardant glass fiber from the side feed port for melt extrusion granulation.

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