Halogen-free flame-retardant glass fiber modified polypropylene material and preparation method thereof

Abstract

The invention relates to the technical field of flame-retardant materials, in particular to a halogen-free flame-retardant glass fiber modified polypropylene material and a preparation method thereof. The material comprises the following components in parts by mass: 60-80 parts of polypropylene, 15-30 parts of long glass fiber, 8-15 parts of a halogen-free intumescent flame retardant, 2-5 parts of a synergist, 3-8 parts of a compatilizer, 2-3 parts of an interface modifier, 2-4 parts of a dynamic cross-linking agent and 1-3 parts of a functional additive. According to the halogen-free flame-retardant glass fiber modified polypropylene material and the preparation method thereof, an intumescent halogen-free flame retardant melamine polyphosphate is compounded with organic montmorillonite, nano zinc borate and MXene, so that the flame-retardant efficiency is improved through a synergistic effect, and the release of smoke and toxic gas in a combustion process is inhibited; the halogen-free flame-retardant glass fiber modified polypropylene material has a good flame-retardant effect by introducing the halogen-free flame-retardant glass fiber, and maleic anhydride grafted polypropylene is introduced as a compatilizer to modify the surface of the long glass fiber and enhance the interface bonding force between the long glass fiber and a matrix.

Description

Technical Field

[0001] The present invention relates to the technical field of flame-retardant materials, and specifically to a halogen-free flame-retardant glass fiber modified polypropylene material and a preparation method thereof. Background Art

[0002] Polypropylene, abbreviated as PP, is a semi-crystalline thermoplastic polymer made from propylene monomers through a polyaddition reaction. It is usually a white waxy solid, non-toxic, odorless, transparent in appearance and light in texture. Fiber-reinforced plastics are one of the most widely used polymer-based composite materials at present. Long glass fiber-reinforced polypropylene (PP / LGF) prepared by the melt impregnation technique has the advantages of high strength, low density, good low-temperature toughness, good heat resistance, and small molding shrinkage.

[0003] However, the current PP / LGF composite material is more flammable than pure PP. Once ignited in the air, it is prone to flaming drips during the combustion process, which is extremely easy to spread the flame. This limits its application in products such as electronics and electrical appliances, transportation, and office automation. At the same time, with the modern society's attention to green environmental protection and human health, halogen-based flame retardants with high flame retardancy efficiency but generating a large amount of smoke and toxic gases during the combustion process will gradually be replaced by halogen-free flame retardants. However, halogen-free flame retardants generally have the defects of low flame retardancy efficiency and low heat resistance. Summary of the Invention

[0004] The purpose of the present invention is to provide a halogen-free flame-retardant glass fiber modified polypropylene material and a preparation method thereof to solve the problems raised in the above background art.

[0005] To achieve the above purpose, the first aspect of the present invention provides a halogen-free flame-retardant glass fiber modified polypropylene material, which contains the following components by mass: 60 - 80 parts of polypropylene, 15 - 30 parts of long glass fiber, 8 - 15 parts of halogen-free intumescent flame retardant, 2 - 5 parts of synergist, 3 - 8 parts of compatibilizer, 2 - 3 parts of interfacial modifier, 2 - 4 parts of dynamic crosslinking agent, and 1 - 3 parts of functional additive.

[0006] In a further embodiment, the retention length of the long glass fiber is 2 - 40 mm, and it is distributed in a gradient in the matrix. The halogen-free intumescent flame retardant is melamine polyphosphate and graphite, and the dosage is 10 - 25 wt%. The synergist is organic montmorillonite, nanozinc borate, and MXene, and the dosage is 1 - 8 wt%. The MXene is a two-dimensional nanomaterial composed of transition metal carbides and nitrides. The compatibilizer is polypropylene grafted maleic anhydride, and the dosage is 1 - 5 wt%. The interfacial modifier is furyl silane, and the dosage is 0.5 - 3 wt%. The dynamic crosslinking agent is bismaleimide, and the dosage is 2 - 5 wt%. The functional additive is nano metal powder and core-shell microcapsule, and the dosage is 1 - 3 wt%.

[0007] The second aspect of the present invention provides a preparation method of a halogen-free flame-retardant glass fiber modified polypropylene material, which is applied to the above-mentioned halogen-free flame-retardant glass fiber modified polypropylene material, and includes the following preparation steps:

[0008] A1. Select raw materials of polypropylene, long glass fiber, halogen-free intumescent flame retardant, synergist, compatibilizer, interfacial modifier, dynamic crosslinking agent and functional additive, and then prepare a co-rotating twin-screw extruder and a pelletizer. The co-rotating twin-screw extruder has five zones, and the five zones are divided according to temperature. The specific zone temperatures are 180°C → 200°C → 220°C → 210°C → 200°C;

[0009] A2. Prepare an ethanol solution with a concentration of 5wt%, then add furanyl silane to the ethanol solution and stir to mix. After mixing, add long glass fiber to it, and through ultrasonic treatment by an ultrasonic cleaning machine and heating and drying in an oven, the interfacial modifier is chemically bonded to the surface of the long glass fiber

[0010] A3. Premix polypropylene, compatibilizer and dynamic crosslinking agent to form a premixed raw material, and then add the premixed raw material into the co-rotating twin-screw extruder from the main feed port. Immediately, the co-rotating twin-screw extruder conveys the premixed raw material towards the discharge port. During the conveying process of the premixed raw material, add functional additive, halogen-free intumescent flame retardant, synergist and long glass fiber from the side feeding port position of the co-rotating twin-screw extruder;

[0011] A4. Then continuously heat and melt the raw materials through the co-rotating twin-screw extruder. After the raw materials are fused, the co-rotating twin-screw extruder extrudes the fused raw materials from the discharge port, starts the pelletizer to cut and pelletize at the discharge port of the co-rotating twin-screw extruder to obtain an unshaped masterbatch, collects the cut unshaped masterbatch and puts it into a dryer to perform drying treatment on the unshaped masterbatch. After drying is completed, a finished flame-retardant masterbatch is obtained.

[0012] In a further embodiment, the preparation method of the core-shell microcapsule is as follows:

[0013] A301. Prepare styrene as a monomer, butyl acrylate as a comonomer, potassium persulfate and a halogen-free intumescent flame retardant, then disperse the halogen-free intumescent flame retardant in deionized water and add it to styrene and butyl acrylate for mixing;

[0014] A302. Add potassium persulfate as an initiator to the mixture of halogen-free intumescent flame retardant, styrene and butyl acrylate, and carry out a heating reaction to form APP microcapsules wrapped with a polystyrene-b-polyacrylate shell layer, and then dry the APP microcapsules by centrifugal separation to obtain core-shell microcapsules.

[0015] In a further embodiment, the mass ratio of styrene to butyl acrylate is 1:1, the purity of potassium persulfate is 0.5 wt%, the heating reaction temperature of the mixture of potassium persulfate, the halogen-free intumescent flame retardant, styrene and butyl acrylate is 70 - 80 °C, the reaction time is 4 - 6 h, the particle size of the core-shell microcapsule is 1 - 10 μm, and the centrifugal separation and drying time of the APP microcapsule is 10 - 12 h, the centrifugal speed is 1200 rpm, and the centrifugal temperature is 50 - 60 °C.

[0016] In a further embodiment, the preparation method of the nano metal powder is as follows:

[0017] A311. Prepare ZIF-8 nanoparticles and absolute ethanol, then pour the ZIF-8 nanoparticles into absolute ethanol for mixing, and then transfer the mixture to an ultrasonic disperser to start ultrasonic dispersion.

[0018] A312. Transfer the dispersion from the ultrasonic disperser to a spray dryer, and then the spray dryer sprays out the dispersion to obtain nano metal powder of ZIF-8.

[0019] In a further embodiment, the mixing mass ratio of the ZIF-8 nanoparticles and absolute ethanol is 1:10, the ultrasonic dispersion temperature of the ultrasonic disperser is 30 - 40 °C, the internal temperature of the spray dryer is 180 °C, and the temperature at the spray outlet of the spray dryer is 80 °C.

[0020] In a further embodiment, the ultrasonic treatment time of the solution mixture of furanyl silane and ethanol solution and long glass fibers in an ultrasonic cleaner is 30 min - 2 h, the ultrasonic power is 200 W, and the frequency is 40 kHz. The drying temperature of the oven is 80 - 10 °C, and the drying time is 2 - 3 h.

[0021] In a further embodiment, the screw speed of the co-rotating twin-screw extruder is 300 rpm, and the feeding speed of the co-rotating twin-screw extruder is 10 kg / h.

[0022] In a further embodiment, the post-treatment preparation steps of the flame retardant masterbatch are as follows:

[0023] B1. Mix the finished flame retardant masterbatch and polypropylene in a mass ratio of 7:3 to obtain a mixed injection molding granule, and then heat and inject the mixed injection molding granule. The mold cavity of the injection molding equipment is the same as that of the flame retardant masterbatch. The heating injection molding process is two-stage injection molding. The first-stage injection molding is set at a temperature of 290 °C to inject the outer layer, so that the core-shell microcapsule ruptures and releases APP, quickly forming a dense carbon layer. Then, the second-stage injection molding temperature is 230 °C to inject the core layer, retaining the glass fiber length and the dynamic cross-linking network structure.

[0024] B2. After the injection molding is completed, the flame retardant masterbatch after post-treatment is taken out from the injection molding machine, and then the flame retardant masterbatch is cooled to obtain the treated flame retardant masterbatch. Subsequently, the cooled flame retardant masterbatch is placed in a thermal-oxidative aging oven. The temperature of the aging oven is set at 120 °C, the oxygen concentration is 50%, and the aging treatment time is 24 h. After the aging treatment is completed, the aging oven continues to heat up to 150 °C and maintains it for 2 h to activate the dynamic covalent bond between bismaleimide and furan groups, forming a self-healing network to obtain the final finished flame retardant masterbatch.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] 1. In the present invention, the intumescent halogen-free flame retardant melamine polyphosphate APP is compounded with organic montmorillonite, nano-zinc borate and MXene. Through the synergistic effect, the flame retardancy efficiency is improved, the release of smoke and toxic gases during combustion is inhibited, and the two-dimensional layered structure of MXene can form a dense barrier during combustion, effectively hindering the diffusion of oxygen and heat, delaying the combustion process, so that the halogen-free flame retardant glass fiber modified polypropylene material has good flame retardancy and better material quality;

[0027] 2. In the present invention, by introducing maleic anhydride grafted polypropylene as a compatibilizer to modify the surface of long glass fibers, the interfacial bonding force between long glass fibers and the matrix is enhanced, and the interfacial debonding caused by thermal-oxidative aging is delayed, thereby improving the surface strength of the halogen-free flame retardant glass fiber modified polypropylene material;

[0028] 3. In the present invention, by regulating the injection molding temperature gradient, the outer layer temperature is 20 - 60 °C higher than the core layer, so that the glass fibers form a gradient distribution structure in the matrix, improving the overall thermal-oxidative aging resistance of the material. At the same time, combined with the ultra-thin section and surface energy spectrum analysis technology, the uniform dispersion of the flame retardant in the matrix is realized, the migration and enrichment during the aging process are inhibited, and the flame retardancy of the halogen-free flame retardant glass fiber modified polypropylene material is improved. Specific Embodiments

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0030] Example 1

[0031] A halogen-free flame retardant glass fiber modified polypropylene material and its preparation method. A halogen-free flame retardant glass fiber modified polypropylene material, the material contains the following components by mass: 60 - 80 parts of polypropylene, 15 - 30 parts of long glass fibers, 8 - 15 parts of halogen-free intumescent flame retardant, 2 - 5 parts of synergist, and 3 - 8 parts of compatibilizer.

[0032] Formula: Polypropylene: 50%, Long Glass Fiber: 20%, Halogen-Free Intumescent Flame Retardant: 15% (Melamine Polyphosphate), Synergist: 10%, Compatibilizer: 5%;

[0033] It includes the following preparation steps:

[0034] A1. Select raw materials of polypropylene, long glass fiber, halogen-free intumescent flame retardant, synergist and compatibilizer. Then prepare a co-rotating twin-screw extruder and a pelletizer. The co-rotating twin-screw extruder has five zones, and the five zones are divided according to temperature. The specific zone temperatures are 180°C → 200°C → 220°C → 210°C → 200°C;

[0035] A2. Premix polypropylene and the compatibilizer to form a premixed raw material. Then add the premixed raw material into the co-rotating twin-screw extruder from the main feed port. Immediately, the co-rotating twin-screw extruder conveys the premixed raw material towards the discharge port. During the conveying process of the premixed raw material, add the halogen-free intumescent flame retardant, synergist and long glass fiber from the side feeding port position of the co-rotating twin-screw extruder;

[0036] A3. Then continuously heat and melt the raw materials through the co-rotating twin-screw extruder. After the raw materials are fused, the co-rotating twin-screw extruder extrudes the fused raw material from the discharge port. Start the pelletizer to cut and pelletize at the discharge port of the co-rotating twin-screw extruder to obtain an unshaped masterbatch. Collect the pelletized unshaped masterbatch and put it into a dryer to conduct drying treatment on the unshaped masterbatch. After drying is completed, obtain the finished flame-retardant masterbatch.

[0037] Example 2

[0038] A halogen-free flame-retardant glass fiber-modified polypropylene material, characterized in that the material contains the following components by mass parts: 60 - 80 parts of polypropylene, 15 - 30 parts of long glass fiber, 8 - 15 parts of halogen-free intumescent flame retardant, 2 - 5 parts of synergist, 3 - 8 parts of compatibilizer and 1 - 3 parts of functional additive;

[0039] Formula: Polypropylene: 50%, Long Glass Fiber: 20%, Halogen-Free Intumescent Flame Retardant: 15% (Melamine Polyphosphate), Synergist: 6%, Compatibilizer: 5% and Functional Additive: 4% (Core-Shell Microcapsule);

[0040] It includes the following preparation steps:

[0041] A1. Select raw materials of polypropylene, long glass fiber, halogen-free intumescent flame retardant, synergist, compatibilizer and functional additive. Then prepare a co-rotating twin-screw extruder and a pelletizer. The co-rotating twin-screw extruder has five zones, and the five zones are divided according to temperature. The specific zone temperatures are 180°C → 200°C → 220°C → 210°C → 200°C;

[0042] A2. Premix polypropylene and a compatibilizer to form a premixed raw material, then add the premixed raw material into a co-rotating twin-screw extruder from the main feed port. Immediately, the co-rotating twin-screw extruder conveys the premixed raw material towards the discharge port. During the conveyance of the premixed raw material, add a functional additive, a halogen-free intumescent flame retardant, a synergist, and long glass fibers at the side feeding port position of the co-rotating twin-screw extruder;

[0043] A3. Then continuously heat and melt the raw materials through the co-rotating twin-screw extruder. After the raw materials are fused, the co-rotating twin-screw extruder extrudes the fused raw material from the discharge port. Start the pelletizer to cut and pelletize at the discharge port of the co-rotating twin-screw extruder to obtain an unshaped masterbatch. Collect the cut unshaped masterbatch and put it into a dryer to perform a drying treatment on the unshaped masterbatch. After the drying is completed, obtain the finished flame-retardant masterbatch.

[0044] Example 3

[0045] A halogen-free flame-retardant glass fiber modified polypropylene material, characterized in that the material contains the following components by mass parts: 60 - 80 parts of polypropylene, 15 - 30 parts of long glass fiber, 8 - 15 parts of halogen-free intumescent flame retardant, 2 - 5 parts of synergist, 3 - 8 parts of compatibilizer, 2 - 4 parts of dynamic crosslinking agent, and 1 - 3 parts of functional additive;

[0046] Formulation: Polypropylene: 55%, Long glass fiber: 18%, Halogen-free intumescent flame retardant: 12% (melamine polyphosphate), Synergist: 5%, Compatibilizer: 4%, Functional additive: 3% (nano metal powder), and Dynamic crosslinking agent: 3%;

[0047] Including the following preparation steps:

[0048] A1. Select raw materials of polypropylene, long glass fiber, halogen-free intumescent flame retardant, synergist, compatibilizer, and functional additive. Then prepare a co-rotating twin-screw extruder and a pelletizer. The co-rotating twin-screw extruder has five zones, and the five zones are divided according to temperature. The specific zone temperatures are 180°C → 200°C → 220°C → 210°C → 200°C;

[0049] A2. Premix polypropylene, compatibilizer, and dynamic crosslinking agent to form a premixed raw material, then add the premixed raw material into the co-rotating twin-screw extruder from the main feed port. Immediately, the co-rotating twin-screw extruder conveys the premixed raw material towards the discharge port. During the conveyance of the premixed raw material, add a functional additive, a halogen-free intumescent flame retardant, a synergist, and long glass fibers at the side feeding port position of the co-rotating twin-screw extruder;

[0050] A3. Then, continuously heat and melt the raw materials with a co-rotating twin-screw extruder. After waiting for the raw materials to fuse, the co-rotating twin-screw extruder extrudes the fused raw materials from the discharge port. Start the pelletizer to cut and pelletize at the discharge port of the co-rotating twin-screw extruder to obtain the non-shaped masterbatch. Collect the cut non-shaped masterbatch and put it into a dryer to dry the non-shaped masterbatch. After drying, the finished flame-retardant masterbatch is obtained.

[0051] Example 4

[0052] A halogen-free flame-retardant glass fiber modified polypropylene material, characterized in that the material contains the following components by mass: 60 - 80 parts of polypropylene, 15 - 30 parts of long glass fiber, 8 - 15 parts of halogen-free intumescent flame retardant, 2 - 5 parts of synergist, 3 - 8 parts of compatibilizer, and 1 - 3 parts of functional additive.

[0053] Formula: Polypropylene: 55%, Long glass fiber: 18%, Halogen-free intumescent flame retardant: 12% (graphite), Synergist: 5%, Compatibilizer: 4%, Functional additive: 3% (nano metal powder), and Dynamic crosslinking agent: 3%.

[0054] It includes the following preparation steps:

[0055] A1. Select raw materials of polypropylene, long glass fiber, halogen-free intumescent flame retardant, synergist, compatibilizer, and functional additive. Then prepare a co-rotating twin-screw extruder and a pelletizer. The co-rotating twin-screw extruder has five zones, and the five zones are divided according to temperature. The specific zone temperatures are 180°C → 200°C → 220°C → 210°C → 200°C.

[0056] A2. Premix polypropylene, compatibilizer, and dynamic crosslinking agent to form a premixed raw material. Then add the premixed raw material into the co-rotating twin-screw extruder from the main feed port. Immediately, the co-rotating twin-screw extruder conveys the premixed raw material towards the discharge port. During the conveying process of the premixed raw material, add the functional additive, halogen-free intumescent flame retardant, synergist, and long glass fiber from the side feeding port position of the co-rotating twin-screw extruder.

[0057] A3. Then, continuously heat and melt the raw materials with a co-rotating twin-screw extruder. After waiting for the raw materials to fuse, the co-rotating twin-screw extruder extrudes the fused raw materials from the discharge port. Start the pelletizer to cut and pelletize at the discharge port of the co-rotating twin-screw extruder to obtain the non-shaped masterbatch. Collect the cut non-shaped masterbatch and put it into a dryer to dry the non-shaped masterbatch. After drying, the finished flame-retardant masterbatch is obtained.

[0058] Example 5

[0059] A halogen-free flame-retardant glass fiber modified polypropylene material, characterized in that the material contains the following components by mass: 60-80 parts of polypropylene, 15-30 parts of long glass fiber, 8-15 parts of halogen-free intumescent flame retardant, 2-5 parts of synergist, 3-8 parts of compatibilizer, 2-3 parts of interfacial modifier and 1-3 parts of functional additive;

[0060] Formulation: polypropylene: 45%, long glass fiber: 20%, halogen-free intumescent flame retardant: 10% (melamine polyphosphate and graphite), synergist: 10%, compatibilizer: 5%, functional additive: 5% (nano metal powder and core-shell microcapsule) and dynamic crosslinking agent: 3% and interfacial modifier: 2%;

[0061] It includes the following preparation steps:

[0062] A1. Select raw materials of polypropylene, long glass fiber, halogen-free intumescent flame retardant, synergist, compatibilizer, interfacial modifier, dynamic crosslinking agent and functional additive, and then prepare a co-rotating twin-screw extruder and a pelletizer. The co-rotating twin-screw extruder has five zones, and the five zones are divided according to temperature. The specific zone temperatures are 180°C → 200°C → 220°C → 210°C → 200°C;

[0063] A2. Prepare an ethanol solution with a concentration of 5wt%, then add the interfacial modifier to the ethanol solution and stir and mix. After mixing, add long glass fiber to it. Through the ultrasonic treatment of an ultrasonic cleaner and heating and drying in an oven, the interfacial modifier is chemically bonded to the surface of the long glass fiber

[0064] A3. Premix polypropylene, compatibilizer and dynamic crosslinking agent to form a premixed raw material, and then add the premixed raw material into the co-rotating twin-screw extruder from the main feed port. Immediately, the co-rotating twin-screw extruder conveys the premixed raw material towards the discharge port. During the conveying process of the premixed raw material, add functional additive, halogen-free intumescent flame retardant, synergist and long glass fiber from the side feeding port position of the co-rotating twin-screw extruder;

[0065] A4. Then continuously heat and melt the raw materials through the co-rotating twin-screw extruder. After the raw materials are fused, the co-rotating twin-screw extruder extrudes the fused raw material from the discharge port, starts the pelletizer to cut and pelletize at the discharge port of the co-rotating twin-screw extruder to obtain an unshaped masterbatch. Collect the cut unshaped masterbatch and put it into a dryer to dry the unshaped masterbatch. After drying, the finished flame-retardant masterbatch is obtained.

[0066] Comparative example

[0067] It is the preparation method of the existing traditional halogen-free flame-retardant polypropylene material, which will not be elaborated here.

[0068] The following performance tests are carried out on the above polypropylene material:

[0069] Flame retardancy (LOI, UL-94, PHRR), mechanical properties (tensile strength, impact strength retention rate), environmental friendliness (smoke density).

[0070] Table 1 is the performance test result table of polypropylene materials:

[0071]

[0072]

[0073] Analyze the performance test data in Table 1 to draw a conclusion

[0074] Flame retardancy: Example 5 shows the best performance, with an LOI of 33% and a 55% reduction in PHRR. For the comparative example, due to the lack of gradient distribution and core-shell flame retardant, the PHRR is as high as 300 kW / m 2 ; Mechanical properties: Example 3 significantly improves the tensile and impact retention rates (≥90%). For the comparative example, due to interface deterioration, the retention rate is the lowest. Environmental friendliness: Example 4 reduces the smoke density to 120, and Example 5 further optimizes it to 100. The CO production rate and smoke density of the comparative example both exceed the standard;

[0075] Therefore, through the synergistic effect of dynamic interface, core-shell flame retardant and nano-metal powder catalysis, Example 5 has the best comprehensive performance, is suitable for the production of different high-end injection products, has good flame retardancy, and does not produce a large amount of smoke and poisonous gas in a high-temperature combustion environment.

[0076] Table 2 shows the combustion behavior of a halogen-free intumescent flame retardant / long glass fiber reinforced polypropylene composite under different thermo-oxidative aging times:

[0077] Aging time (days) 0 10 30 50 Thermal ignition time / s 32 33 35 37 <![CDATA[Peak heat release rate / (kWm 2 )]]> 197.2 178.3 153.8 122.5 <![CDATA[Average heat release rate / (kWm 2 )]]> 110.2 93.1 78.9 81.6 <![CDATA[Total heat release / (MJm 2 )]]> 136.1 125.8 117.2 105.7 Average carbon monoxide yield (kg / kg) 0.0305 0.0287 0.0268 0.0245 Average carbon dioxide yield (kg / kg) 2.14 1.95 1.79 1.68 UL-94 flame retardant rating V-0 V-0 V-0 V-0

[0078] Table 3 shows the combustion behavior of traditional halogen-free flame retardant polypropylene materials under different thermo-oxidative aging times:

[0079]

[0080]

[0081] Referring to Table 2: The glass fiber modified polypropylene material can remain in a relatively stable state for a long time after thermo-oxidative aging, attributed to the thermal stability, anti-exudation property of the halogen-free intumescent flame retardant and the relatively small influence of thermo-oxidative aging on the thermal stability of the composite material;

[0082] Refer to Table 3: After the artificial aging of the traditional halogen-free flame-retardant polypropylene material, the flame-retardant performance of the traditional halogen-free flame-retardant polypropylene material shows a significant decline. Therefore, by adding a halogen-free intumescent flame retardant to compare the flame-retardant performance of the traditional halogen-free flame-retardant polypropylene material, the flame-retardant effect of the polypropylene composite material can be effectively improved.

[0083] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A halogen-free flame-retardant glass fiber modified polypropylene material, characterized in that: The material comprises the following components by mass: 60-80 parts of polypropylene, 15-30 parts of long glass fibers, 8-15 parts of halogen-free intumescent flame retardant, 2-5 parts of synergist, 3-8 parts of compatibilizer, 2-3 parts of interface modifier, 2-4 parts of dynamic cross-linking agent and 1-3 parts of functional additive.

2. The halogen-free flame-retardant glass fiber modified polypropylene material according to claim 1, characterized in that: The retention length of the long glass fiber is 2-40 mm, and it is distributed in a gradient in the matrix. The halogen-free intumescent flame retardant is melamine polyphosphate and graphite, and the amount used is 10-25wt%. The synergist is organic montmorillonite, nano zinc borate and MXene, and the amount used is 1-8wt%. The MXene is a two-dimensional nano material composed of transition metal carbides and nitrides. The compatibilizer is polypropylene grafted maleic anhydride, and the amount used is 1-5wt%. The interface modifier is furanyl silane, and the amount used is 0.5-3wt%. The dynamic cross-linking agent is bismaleimide, and the amount used is 2-5wt%. The functional additive is nano metal powder and core-shell microcapsules, and the amount used is 1-3wt%.

3. A method for preparing a halogen-free flame-retardant glass fiber modified polypropylene material is applied to the halogen-free flame-retardant glass fiber modified polypropylene material according to any one of claims 1 to 2, characterized in that: The preparation steps include: A1. Select raw materials polypropylene, long glass fiber, halogen-free intumescent flame retardant, synergist, compatibilizer, interface modifier, dynamic cross-linking agent and functional additives, and then prepare a co-rotating twin-screw extruder and a pelletizer. The co-rotating twin-screw extruder has five partitions, which are divided according to temperature. The specific partition temperatures are 180℃→200℃→220℃→210℃→200℃; A2. Prepare an ethanol solution with a concentration of 5 wt%, then add the interface modifier to the ethanol solution and stir and mix. After the mixing is completed, add the long glass fiber thereto, and subject it to ultrasonic treatment in an ultrasonic cleaning machine and drying by heating in an oven so that the interface modifier is chemically bonded to the surface of the long glass fiber. A3, premixing polypropylene, a compatibilizer and a dynamic crosslinking agent to form a premixed raw material, and then adding the premixed raw material into a co-rotating twin-screw extruder from a main feed port, and then the co-rotating twin-screw extruder conveys the premixed raw material toward a discharge port. During the conveying of the premixed raw material, functional additives, halogen-free intumescent flame retardant, synergist and long glass fiber are added from a side feed port of the co-rotating twin-screw extruder; A4. Then, the raw materials are continuously heated and melted by a co-rotating twin-screw extruder. After the raw materials are fused, the co-rotating twin-screw extruder extrude the fused raw materials from the discharge port, and the pelletizer is started to cut and granulate at the discharge port of the co-rotating twin-screw extruder to obtain unshaped masterbatches. The unshaped masterbatches after pelletizing are collected and put into a dryer to dry the unshaped masterbatches. After drying, the finished flame retardant masterbatches are obtained.

4. The method for preparing a halogen-free flame-retardant glass fiber modified polypropylene material according to claim 3, characterized in that: The preparation method of the core-shell microcapsule is as follows: A301, preparing styrene as a monomer, butyl acrylate as a comonomer, potassium persulfate and a halogen-free intumescent flame retardant, then dispersing the halogen-free intumescent flame retardant in deionized water, and then adding the styrene and butyl acrylate to mix; A302. Potassium persulfate is added as an initiator to a mixture of a halogen-free intumescent flame retardant, styrene and butyl acrylate, and a heating reaction is performed to form APP microcapsules wrapped in a polystyrene-b-polyacrylate shell layer. The APP microcapsules are then dried by centrifugal separation to obtain core-shell microcapsules.

5. The method for preparing a halogen-free flame-retardant glass fiber modified polypropylene material according to claim 4, characterized in that: The mass ratio of styrene to butyl acrylate is 1:1, the purity of potassium persulfate is 0.5wt%, the heating reaction temperature of the mixed solution of potassium persulfate, halogen-free intumescent flame retardant, styrene and butyl acrylate is 70-80°C, the reaction time is 4-6h, the particle size of the core-shell microcapsule is 1-10μm, the centrifugal separation and drying time of the APP microcapsule is 10-12h, the centrifugal speed is 1200rpm, and the centrifugal temperature is 50-60°C.

6. The method for preparing a halogen-free flame-retardant glass fiber modified polypropylene material according to claim 3, characterized in that: The preparation method of the nano metal powder is as follows: A311, preparing ZIF-8 nanoparticles and anhydrous ethanol, then pouring the ZIF-8 nanoparticles into the anhydrous ethanol and mixing, and then transferring the mixed solution to an ultrasonic disperser and starting ultrasonic dispersion; A312. Transfer the dispersion from the ultrasonic disperser to a spray dryer, and then spray the dispersion from the spray dryer to obtain nano-metal powder of ZIF-8.

7. The method for preparing a halogen-free flame-retardant glass fiber modified polypropylene material according to claim 6, characterized in that: The mixing mass ratio of the ZIF-8 nanoparticles and anhydrous ethanol is 1:10, the ultrasonic dispersion temperature of the ultrasonic disperser is 30-40°C, the internal temperature of the spray dryer is 180°C, and the temperature of the spray outlet of the spray dryer is 80°C.

8. The method for preparing a halogen-free flame-retardant glass fiber modified polypropylene material according to claim 3, characterized in that: The ultrasonic treatment time of the mixed solution of furanyl silane and ethanol solution and the long glass fiber in the ultrasonic cleaning machine is 30min-2h, the ultrasonic power is 200W, the frequency is 40kHz, the drying temperature of the oven is 80-10℃, and the drying time is 2-3h.

9. The method for preparing a halogen-free flame-retardant glass fiber modified polypropylene material according to claim 3, characterized in that: The screw speed of the co-rotating twin-screw extruder is 300 rpm, and the feeding rate of the co-rotating twin-screw extruder is 10 kg / h.

10. The method for preparing a halogen-free flame-retardant glass fiber modified polypropylene material according to claim 3, characterized in that: The post-processing preparation steps of the flame retardant masterbatch are as follows: B1. The finished flame retardant masterbatch and polypropylene are mixed in a mass ratio of 7:3 to obtain mixed injection molding pellets, and then the mixed injection molding pellets are heated and injection molded. The mold tank of the injection molding equipment is consistent with the flame retardant masterbatch. The heating injection molding process is a two-stage injection molding process. The first stage injection molding temperature is set at 290°C to inject the outer layer, so that the core-shell microcapsules are ruptured to release APP and quickly form a dense carbon layer. Then the second stage injection molding temperature is 230°C to inject the core layer to retain the glass fiber length and dynamic cross-linking network structure. B2. After the injection molding is completed, the flame retardant masterbatch that has been post-processed is taken out from the injection molding machine, and then the flame retardant masterbatch is cooled to obtain the treated flame retardant masterbatch, and then the cooled flame retardant masterbatch is placed in a thermal oxygen aging box. The aging box is set to a temperature of 120°C, an oxygen concentration of 50%, and an aging treatment time of 24 hours. After the aging treatment is completed, the aging box continues to heat up to 150°C and maintains for 2 hours to activate the dynamic covalent bond between the bismaleimide and the furan group, forming a self-healing network to obtain the final finished flame retardant masterbatch.

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