High-strength flame-retardant plastic and preparation method thereof

Abstract

The invention provides high-strength flame-retardant plastic and a preparation method thereof. The high-strength flame-retardant plastic is prepared from the following components: pre-irradiated polyhedral oligomeric silsesquioxane reinforced polypropylene, a flame retardant compound, a flame-retardant synergist, a lubricant and an antioxidant. Wherein the flame retardant compound is prepared by compounding at least two of a hyperbranched triazine charring agent, ammonium polyphosphate, melamine polyphosphate and antimony trioxide. The prepared high-strength flame-retardant plastic has stable char forming property and mechanical property, polypropylene is reinforced by using pre-irradiated polyhedral oligomeric silsesquioxane, so that free radicals are generated on the surface of the polyhedral oligomeric silsesquioxane and can form chemical bonds with a polypropylene chain, the interface bonding force is enhanced, and the mechanical property loss caused by addition of a flame retardant is counteracted. And on the other hand, the problem of poor thermal stability of polypropylene after irradiation can be solved.

Description

Technical Field

[0001] The present application relates to the technical field of polymer materials, and particularly relates to a high-strength flame-retardant plastic and a preparation method thereof. Background Art

[0002] In recent years, polypropylene (PP) has been widely used in many fields such as construction, home furnishing, and industry due to its advantages of light weight, corrosion resistance, and easy processing. However, PP has a low oxygen index and serious melt dripping during combustion, and cannot meet the usage requirements in the field of live fire prevention, so flame-retardant modification is required. Polypropylene has extremely poor char-forming ability, and its melting point is much lower than the degradation temperature, and a large addition amount is required to obtain satisfactory anti-melt dripping performance, which will reduce its strength. Intumescent flame retardants (IFRs) have low smoke generation, low toxicity, and are more environmentally friendly, and gradually replace bromine-antimony flame retardants to become the mainstream application in the industry. However, traditional IFRs have low flame-retardant efficiency and a large addition amount, and it is difficult to ensure the mechanical properties of polypropylene. Summary of the Invention

[0003] In view of this, in order to solve at least one of the above technical problems, the embodiments of the present application provide a high-strength flame-retardant plastic.

[0004] The embodiments of the present application provide a high-strength flame-retardant plastic, which is composed of the following components in parts by weight: 70-94 parts of pre-irradiated cage-like silsesquioxane reinforced polypropylene, 10-25 parts of a flame retardant composite, 0.5-5 parts of a flame retardant synergist, 0.5-2.1 parts of a lubricant, and 0.4-0.8 parts of an antioxidant. Among them, the flame retardant composite includes at least two of hyperbranched triazine charring agent, ammonium polyphosphate, melamine polyphosphate, and antimony trioxide in a compound form.

[0005] In an embodiment of the present application, the flame retardant composite is composed of hyperbranched triazine charring agent, melamine polyphosphate, and antimony trioxide in a weight ratio of 2:1:1.

[0006] In another embodiment of the present application, the flame retardant composite is composed of hyperbranched triazine charring agent, ammonium polyphosphate, and antimony trioxide in a weight ratio of 3:2:1.

[0007] In some embodiments of the present application, the preparation method of the pre-irradiated cage-like silsesquioxane reinforced polypropylene includes the following steps: drying polypropylene and cage-like silsesquioxane in a vacuum oven at 60°C to 80°C for 10 h to 12 h to remove surface moisture, adding molybdenum salt powder and introducing liquid nitrogen to stir and mix, with a stirring rate of 1000 rpm to 1500 rpm, to obtain a premix. Granulating the premix by melting to obtain a first mixture. Drying the first mixture in a vacuum oven at 60°C to 80°C for 8 h to 10 h, using 60The first mixture is subjected to γ-irradiation treatment with a Co source to obtain the pre-irradiated cage silsesquioxane-reinforced polypropylene.

[0008] In some embodiments of the present application, the irradiation treatment parameters are as follows: the irradiation dose rate is 30 kGy / h to 80 kGy / h, the irradiation dose is 40 kGy to 80 kGy, and the irradiation time is 0.5 h to 2 h.

[0009] In some embodiments of the present application, the weight ratio of the polypropylene to the cage silsesquioxane is 100:(0.8 - 3), and the weight ratio of the polypropylene to the molybdenum salt is 100:(12 - 35).

[0010] In some embodiments of the present application, the molybdenum salt is any one of sodium molybdate, ammonium octamolybdate, and potassium molybdate.

[0011] In some embodiments of the present application, the flame retardant synergist is nanozirconium phosphate.

[0012] In some embodiments of the present application, the melt index of the polypropylene is 1.8 g / min to 3.5 g / min, the isotacticity is 98.5%, the relative molecular mass distribution M w / M n ≥6, and the ash content ≤0.03%.

[0013] In addition, the embodiments of the present application also provide a method for preparing the aforementioned high-strength flame retardant plastic, which includes the following steps: pre-irradiated cage silsesquioxane-reinforced polypropylene, a flame retardant composite, a flame retardant synergist, a lubricant, and an antioxidant are placed in a reaction kettle by weight for blending. The shear rate is 100 rpm to 200 rpm, and the mixture is mixed at 180°C to 220°C for 10 min to 15 min, and then pelletized to obtain the high-strength flame retardant plastic.

[0014] Compared with the prior art, the high-strength flame retardant plastic provided by the embodiments of the present application has stable charring properties and mechanical properties. By using pre-irradiated cage silsesquioxane-reinforced polypropylene, free radicals are generated on the surface of the cage silsesquioxane, which can form chemical bonds with the polypropylene chains, enhancing the interfacial bonding force, thereby offsetting the loss of mechanical properties caused by the addition of the flame retardant. On the other hand, it offsets the problem of poor thermal stability of polypropylene after irradiation. At the same time, the cross-linked network of cage silsesquioxane and polypropylene generated by the irradiation treatment can form a high-thermal-stability graphitized carbon layer structure during the combustion process, thereby protecting the internal matrix and delaying its degradation process. Furthermore, it increases the melt strength, providing a higher shear stress in the subsequent blending stage, forcing the flame retardant composite particles to break and disperse evenly. The hyperbranched triazine charring agent adsorbs other flame retardant components through molecular chain entanglement, further inhibiting agglomeration and ensuring the balance of flame retardancy and mechanical properties. Description of the Drawings

[0015] Figure 1 This is the SEM image of the premix in Comparative Example 2 of the present application.

[0016] Figure 2 This is the SEM image of the premix in Example 1 of the present application. Detailed implementation manners

[0017] The following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments.

[0018] When polypropylene materials burn, the melt flow phenomenon caused by high temperature will lead to molten dripping, exacerbating the spread of fire and increasing the combustion risk. Suppressing the formation of molten droplets has become a key technical challenge for expanding the application of polypropylene in fields with high fire safety requirements. Currently, mainly by introducing flame retardants to promote the formation of a dense carbon layer on the combustion surface, thereby isolating the transfer of heat and oxygen to achieve molten droplet suppression. The intumescent flame retardant system (IFR) shows significant advantages in the field of polypropylene flame retardancy due to its low smoke and low toxicity characteristics during combustion. However, traditional IFR systems generally have problems of poor thermal stability and low flame retardancy efficiency. To achieve an ideal flame retardant effect, a high proportion of addition is often required, resulting in obvious deterioration of the mechanical strength and processing performance of the material. Therefore, developing an efficient IFR system requires maximizing the mechanical properties and thermal stability of the matrix material while ensuring the flame retardant performance. As the core component of IFR, the charring efficiency and the compactness of the char residue structure of the charring agent directly determine the heat insulation performance of the expanded carbon layer, and thus affect the overall flame retardant efficiency.

[0019] Therefore, a high-strength flame retardant plastic provided by an embodiment of the present application is composed of the following components in parts by weight: 70 - 94 parts of pre-irradiated cage-like silsesquioxane reinforced polypropylene, 10 - 25 parts of a flame retardant composite, 0.5 - 5 parts of a flame retardant synergist, 0.5 - 2.1 parts of a lubricant, and 0.4 - 0.8 parts of an antioxidant. Among them, the flame retardant composite includes at least two of a hyperbranched triazine charring agent, ammonium polyphosphate, melamine polyphosphate, and antimony trioxide in a compound form.

[0020] Compared with the prior art, the high-strength flame-retardant plastic provided by the embodiments of the present application has stable charring properties and mechanical properties. By using pre-irradiated cage-like silsesquioxane to reinforce polypropylene, free radicals are generated on the surface of the cage-like silsesquioxane, which can form chemical bonds with the polypropylene chains to enhance the interfacial bonding force, thereby offsetting the loss of mechanical properties caused by the addition of flame retardants. On the other hand, it offsets the problem of poor thermal stability of polypropylene after irradiation. At the same time, the cross-linked network of cage-like silsesquioxane and polypropylene generated by irradiation treatment can form a graphite-like carbon layer structure with high thermal stability during combustion, thereby protecting the internal matrix and delaying its degradation process. Furthermore, it also increases the melt strength, providing a higher shear stress in the subsequent blending stage, forcing the flame retardant composite particles to break and disperse evenly. The hyperbranched triazine charring agent adsorbs other flame retardant components through molecular chain entanglement. Its highly branched three-dimensional structure rapidly cross-links to form a dense carbon layer during combustion, and the pre-irradiated POSS enhances the rigidity of the carbon layer skeleton through chemical cross-linking, making the carbon layer not easily cracked at high temperatures. Further suppressing agglomeration ensures the balance of flame retardancy efficiency and mechanical properties.

[0021] In some embodiments of the present application, the flame retardant composite is composed of a hyperbranched triazine charring agent, melamine polyphosphate, and antimony trioxide compounded in a weight ratio of 2:1:1. The hyperbranched triazine charring agent promotes the formation of a carbon layer at high temperatures, effectively isolating heat and oxygen. Melamine polyphosphate (a phosphorus / nitrogen-based flame retardant) promotes the dehydration and carbonization of the substrate by decomposing to produce phosphoric acid, while releasing non-combustible gases to dilute the oxygen concentration. The efficient carbonization of the hyperbranched triazine and the gas source function of MPP are complementary, forming an expanded carbon layer during combustion. At the same time, when antimony trioxide is compounded with the phosphorus / nitrogen flame retardant, it inhibits the gas-phase combustion chain reaction by generating free radical scavengers such as SbPO4. On the other hand, in combination with the irradiated polypropylene, it can reduce melting and dripping and significantly improve the vertical burning rating.

[0022] In another embodiment of the present application, the flame retardant composite is composed of a hyperbranched triazine charring agent, ammonium polyphosphate, and antimony trioxide compounded in a weight ratio of 3:2:1. The flame retardant performance of polypropylene is enhanced by compounding ammonium polyphosphate, hyperbranched triazine charring agent, and antimony trioxide. The benzene ring and triazine group structures in the triazine charring agent can participate in the formation of the carbon layer and improve the quality of the carbon layer. When antimony trioxide is compounded with the phosphorus / nitrogen flame retardant, it inhibits the gas-phase combustion chain reaction by generating free radical scavengers such as SbPO4.

[0023] In some embodiments of the present application, the flame retardant synergist is nanozirconium phosphate. The catalytic carbonization effect of nanozirconium phosphate improves the quality of the carbon layer of polypropylene, thereby enhancing the inhibitory effect of the carbon layer on the heat and gas flow during the combustion process, and further improving the flame retardancy efficiency of polypropylene. When compounded with ammonium polyphosphate, charring agent, etc., ZrP improves the flame retardancy efficiency through dual mechanisms of catalysis and barrier, while improving the mechanical properties and processing fluidity of polypropylene.

[0024] In some embodiments of the present application, the lubricant is any one of paraffin wax or polyethylene wax, and the antioxidant is any one of antioxidant 1010 or antioxidant 2246.

[0025] In some embodiments of the present application, the preparation method of the pre-irradiated cage-like silsesquioxane reinforced polypropylene comprises the following steps,

[0026] Step S01: Dry polypropylene and cage-like silsesquioxane in a vacuum oven at 60°C to 80°C for 10 h to 12 h to remove surface moisture. It can effectively remove the moisture and low-molecular volatile substances adsorbed on the material surface, reduce the risk of hydrolysis or phase separation caused by residual moisture in subsequent processing, and improve the thermal stability and interfacial bonding strength of the material. Add molybdenum salt powder and introduce liquid nitrogen for stirring and mixing, and the stirring rate is 1000 rpm to 1500 rpm to obtain a premix. The low-temperature mixing by introducing liquid nitrogen into the reaction system can refine the cage-like silsesquioxane particles through the embrittlement effect and reduce the agglomeration caused by polarity differences. This premixing process can also avoid the thermal degradation of cage-like silsesquioxane that may be caused by direct mixing at high temperature, and ensure the integrity of its cage structure, so as to fully play the role of enhancing the interfacial bonding force in the subsequent irradiation cross-linking process. In some embodiments, the particle size of polypropylene is 10 μm to 80 μm. The particle size of cage-like silsesquioxane is 1.5 nm to 3 nm. The particle size of molybdenum salt is 200 nm to 250 nm. Optionally, the cage-like silsesquioxane is octaepoxy cage-like silsesquioxane.

[0027] In some embodiments, the drying temperature can be 60°C, 70°C, and 80°C. The drying time can be 10 h, 11 h, and 12 h. The stirring rate can be 1000 rpm, 1200 rpm, 1300 rpm, and 1500 rpm.

[0028] In some embodiments of the present application, the weight ratio of the polypropylene to the cage-like silsesquioxane is 100:(10 - 20), and the weight ratio of the polypropylene to the molybdenum salt is 100:(12 - 35).

[0029] In some embodiments, the weight ratio of the polypropylene to the cage silsesquioxane can be 100:10, 100:12, 100:15, and 100:20. If the weight ratio of the polypropylene to the cage silsesquioxane is less than 100:10, the enhancement effect is not significant. The weight ratio of the polypropylene to the molybdate can be 100:12, 100:20, 100:32, and 100:35.

[0030] In some embodiments of the present application, the molybdate is any one of sodium molybdate, ammonium octamolybdate, and potassium molybdate. In some embodiments, the molybdate is ammonium octamolybdate. By adding molybdate to the polypropylene irradiation system, the formation of the polypropylene irradiation crosslinked structure is promoted.

[0031] In some embodiments of the present application, the melt index of the polypropylene is 1.8 g / min to 3.5 g / min, the isotacticity is 98.5%, and the relative molecular mass distribution M w / M n ≥6, and the ash content ≤ 0.03%.

[0032] Step S02: Melt and granulate the premix to obtain a first mixture.

[0033] Step S03: Dry the first mixture in a vacuum oven at 60°C to 80°C for 8 h to 10 h, and perform γ-irradiation treatment on the first mixture using a 60 Co source to obtain the pre-irradiated cage silsesquioxane reinforced polypropylene.

[0034] In some embodiments of the present application, the irradiation treatment parameters are as follows: the irradiation dose rate is 30 kGy / h to 80 kGy / h, the irradiation dose is 40 kGy to 80 kGy, and the irradiation time is 1 h - 2 h.

[0035] In some embodiments, the irradiation dose rate can be 30 kGy / h, 40 kGy / h, 60 kGy / h, and 80 kGy / h, the irradiation dose can be 40 kGy, 60 kGy, and 80 kGy, and the irradiation time can be 0.5 h, 1 h, and 2 h.

[0036] In addition, the embodiments of the present application also provide a preparation method of the aforementioned high-strength flame-retardant plastic, which specifically includes the following steps:

[0037] Step S1: Weigh and place the pre-irradiated cage silsesquioxane reinforced polypropylene, flame retardant composite, flame retardant synergist, lubricant, and antioxidant into a reaction kettle for melt blending. The shear rate is 100 rpm to 200 rpm, and the mixture is mixed at a temperature of 180°C to 220°C for 10 min to 15 min.

[0038] Among them, the head temperature is 190 °C, the temperature of zone 1 is 200 °C, the temperature of zone 2 is 210 °C, the temperature of zone 3 is 220 °C, the temperature of zone 4 is 210 °C, and the temperature of zone 5 is 200 °C.

[0039] Step S2. Extrude and pelletize the blend to obtain the high-strength flame-retardant plastic.

[0040] In some embodiments, the shear rate can be 100 rpm, 150 rpm, and 200 rpm. The shear temperature can be 180 °C, 190 °C, and 200 °C. The mixing time can be 10 min, 12 min, 13 min, and 15 min.

[0041] Compared with the prior art, the preparation method of the high-strength flame-retardant plastic provided by the embodiments of the present application has the following

[0042] Beneficial effects:

[0043] This preparation method has a simple and efficient process, which is conducive to the large-scale production of high-strength flame-retardant plastics and has excellent commercial prospects.

[0044] The foregoing high-strength flame-retardant plastic and its preparation method are further described below through specific examples.

[0045] Example 1

[0046] Step 1. Dry polypropylene and octa(epoxypropyl)silsesquioxane in a vacuum oven at 80 °C for 12 h to remove surface moisture according to a weight ratio of 100:10. Add ammonium octamolybdate according to a weight ratio of 100:20 and introduce liquid nitrogen to stir and mix. The stirring rate is 1000 rpm to obtain a premix. Melt and pelletize the premix to obtain a first mixture. Dry the first mixture in a vacuum oven at 80 °C for 8 h, and use 60 a Co source to perform γ-irradiation treatment on the first mixture to obtain the pre-irradiated silsesquioxane-reinforced polypropylene. Among them, the irradiation dose is 40 kGy, and the irradiation dose rate is 80 kGy / h.

[0047] Step 2. Put 78 parts of pre-irradiated silsesquioxane-reinforced polypropylene, 15 parts of flame retardant composite, 1 part of zirconium phosphate nanometer, 1.5 parts of polyethylene wax, and 0.3 part of antioxidant 1010 into a reaction kettle for melt blending. The shear rate is 100 rpm, and the mixture is mixed at 180 °C for 15 min. Extrude and pelletize the blend to obtain the high-strength flame-retardant plastic. Among them, the flame retardant composite is composed of a hyperbranched triazine charring agent, melamine polyphosphate, and antimony trioxide compounded according to a weight ratio of 2:1:1.

[0048] Among them, the head temperature is 190°C, the temperature of the first zone is 200°C, the temperature of the second zone is 210°C, the temperature of the third zone is 220°C, the temperature of the fourth zone is 210°C, and the temperature of the fifth zone is 200°C.

[0049] Example 2

[0050] Step 1: Mix polypropylene and octa(epoxypropyl)silsesquioxane in a weight ratio of 100:10, and dry them in a vacuum oven at 80°C for 12 h to remove surface moisture. Add ammonium octamolybdate in a weight ratio of 100:20 and introduce liquid nitrogen to stir and mix. The stirring rate is 1000 rpm to obtain a premix. Melt and granulate the premix to obtain a first mixture. Dry the first mixture in a vacuum oven at 80°C for 8 h, and use 60 a Co source to perform γ-irradiation treatment on the first mixture to obtain the pre-irradiated silsesquioxane-reinforced polypropylene. Among them, the irradiation dose is 40 kGy, and the irradiation dose rate is 80 kGy / h.

[0051] Step 2: Put 78 parts of pre-irradiated silsesquioxane-reinforced polypropylene, 15 parts of flame retardant composite, 1 part of nanozirconium phosphate, 1.5 parts of polyethylene wax, and 0.3 part of antioxidant 1010 into a reaction kettle for melt blending. The shear rate is 100 rpm, and the mixture is mixed at 180°C for 15 min. Extrude and granulate the blend to obtain a high-strength flame retardant plastic. Among them, the flame retardant composite is composed of a hyperbranched triazine charring agent, ammonium polyphosphate, and antimony trioxide in a weight ratio of 3:2:1.

[0052] Among them, the head temperature is 190°C, the temperature of the first zone is 200°C, the temperature of the second zone is 210°C, the temperature of the third zone is 220°C, the temperature of the fourth zone is 210°C, and the temperature of the fifth zone is 200°C.

[0053] Example 3

[0054] Step 1: Mix polypropylene and octa(epoxypropyl)silsesquioxane in a weight ratio of 100:12, and dry them in a vacuum oven at 80°C for 12 h to remove surface moisture. Add ammonium octamolybdate in a weight ratio of 100:20 and introduce liquid nitrogen to stir and mix. The stirring rate is 1000 rpm to obtain a premix. Melt and granulate the premix to obtain a first mixture. Dry the first mixture in a vacuum oven at 80°C for 8 h, and use 60 a Co source to perform γ-irradiation treatment on the first mixture to obtain the pre-irradiated silsesquioxane-reinforced polypropylene. Among them, the irradiation dose is 40 kGy, and the irradiation dose rate is 80 kGy / h.

[0055] Step 2: Weigh 78 parts of pre-irradiated cage-like silsesquioxane reinforced polypropylene, 15 parts of flame retardant composite, 1 part of nanozirconium phosphate, 1.5 parts of polyethylene wax, and 0.3 part of antioxidant 1010 and place them into a reaction kettle for melt blending. The shear rate is 100 rpm, and the mixture is mixed at 180 °C for 15 min. The blend is extruded and pelletized to obtain the high-strength flame retardant plastic. Among them, the flame retardant composite is prepared by compounding hyperbranched triazine charring agent, melamine polyphosphate, and antimony trioxide according to a weight ratio of 2:1:1.

[0056] Among them, the head temperature is 190 °C, the temperature of the first zone is 200 °C, the temperature of the second zone is 210 °C, the temperature of the third zone is 220 °C, the temperature of the fourth zone is 210 °C, and the temperature of the fifth zone is 200 °C.

[0057] Example 4

[0058] Step 1: Mix polypropylene and octa-epoxy cage-like silsesquioxane in a weight ratio of 100:15 and dry them in a vacuum oven at 80 °C for 12 h to remove surface moisture. Add ammonium octamolybdate in a weight ratio of 100:20 and introduce liquid nitrogen for stirring and mixing. The stirring rate is 1000 rpm to obtain a premix. The premix is melt pelletized to obtain the first mixture. The first mixture is dried in a vacuum oven at 80 °C for 8 h, and the first mixture is subjected to γ-irradiation treatment using 60 a Co source to obtain the pre-irradiated cage-like silsesquioxane reinforced polypropylene. Among them, the irradiation dose is 40 kGy, and the irradiation dose rate is 80 kGy / h.

[0059] Step 2: Weigh 78 parts of pre-irradiated cage-like silsesquioxane reinforced polypropylene, 15 parts of flame retardant composite, 1 part of nanozirconium phosphate, 1.5 parts of polyethylene wax, and 0.3 part of antioxidant 1010 and place them into a reaction kettle for melt blending. The shear rate is 100 rpm, and the mixture is mixed at 180 °C for 15 min. The blend is extruded and pelletized to obtain the high-strength flame retardant plastic. Among them, the flame retardant composite is prepared by compounding hyperbranched triazine charring agent, melamine polyphosphate, and antimony trioxide according to a weight ratio of 2:1:1.

[0060] Among them, the head temperature is 190 °C, the temperature of the first zone is 200 °C, the temperature of the second zone is 210 °C, the temperature of the third zone is 220 °C, the temperature of the fourth zone is 210 °C, and the temperature of the fifth zone is 200 °C.

[0061] Example 5

[0062] Step 1: Polypropylene and octa(epoxypropyl)silsesquioxane are dried in a vacuum oven at 80 °C for 12 h to remove surface moisture in a weight ratio of 100:20. Ammonium octamolybdate is added in a weight ratio of 100:32 and liquid nitrogen is introduced for stirring and mixing at a stirring rate of 1000 rpm to obtain a premix. The premix is melt granulated to obtain a first mixture. The first mixture is dried in a vacuum oven at 80 °C for 8 h and then 60 γ-irradiation treatment of the first mixture is carried out using a

[0063] Co source to obtain the pre-irradiated silsesquioxane-reinforced polypropylene. Among them, the irradiation dose is 40 kGy and the irradiation dose rate is 80 kGy / h.

[0064] Among them, the head temperature is 190 °C, the temperature of zone 1 is 200 °C, the temperature of zone 2 is 210 °C, the temperature of zone 3 is 220 °C, the temperature of zone 4 is 210 °C, and the temperature of zone 5 is 200 °C.

[0065] Example 6

[0066] Step 1: Polypropylene and octa(epoxypropyl)silsesquioxane are dried in a vacuum oven at 80 °C for 12 h to remove surface moisture in a weight ratio of 100:10. Ammonium octamolybdate is added in a weight ratio of 100:35 and liquid nitrogen is introduced for stirring and mixing at a stirring rate of 1000 rpm to obtain a premix. The premix is melt granulated to obtain a first mixture. The first mixture is dried in a vacuum oven at 80 °C for 8 h and then 60 γ-irradiation treatment of the first mixture is carried out using a

[0067] Co source to obtain the pre-irradiated silsesquioxane-reinforced polypropylene. Among them, the irradiation dose is 40 kGy and the irradiation dose rate is 80 kGy / h.

[0068] Among them, the head temperature is 190 °C, the temperature of the first zone is 200 °C, the temperature of the second zone is 210 °C, the temperature of the third zone is 220 °C, the temperature of the fourth zone is 210 °C, and the temperature of the fifth zone is 200 °C.

[0069] Example 7

[0070] Step 1: Polypropylene and octa(epoxypropyl)silsesquioxane are dried in a vacuum oven at 80 °C for 12 h to remove surface moisture in a weight ratio of 100:10. Ammonium octamolybdate is added in a weight ratio of 100:12 and liquid nitrogen is introduced for stirring and mixing. The stirring rate is 1000 rpm to obtain a premix. The premix is melt granulated to obtain a first mixture. The first mixture is dried in a vacuum oven at 80 °C for 8 h, and 60 the first mixture is subjected to γ-irradiation treatment using a Co source to obtain the pre-irradiated silsesquioxane-reinforced polypropylene. Among them, the irradiation dose is 40 kGy and the irradiation dose rate is 80 kGy / h.

[0071] Step 2: 78 parts by weight of pre-irradiated silsesquioxane-reinforced polypropylene, 15 parts of a flame retardant composite, 1 part of zirconium phosphate nanometer, 1.5 parts of polyethylene wax, and 0.3 part of antioxidant 1010 are placed into a reaction kettle for melt blending. The shear rate is 100 rpm and the mixture is mixed at 180 °C for 15 min. The blend is extruded and granulated to obtain a high-strength flame retardant plastic. Among them, the flame retardant composite is prepared by compounding hyperbranched triazine charring agent, melamine polyphosphate, and antimony trioxide in a weight ratio of 2:1:1.

[0072] Among them, the head temperature is 190 °C, the temperature of the first zone is 200 °C, the temperature of the second zone is 210 °C, the temperature of the third zone is 220 °C, the temperature of the fourth zone is 210 °C, and the temperature of the fifth zone is 200 °C.

[0073] Comparative Example 1

[0074] 78 parts by weight of polypropylene, 15 parts of a flame retardant composite, 1 part of zirconium phosphate nanometer, 1.5 parts of polyethylene wax, and 0.3 part of antioxidant 1010 are placed into a reaction kettle for melt blending. The shear rate is 100 rpm and the mixture is mixed at 180 °C for 15 min. The blend is extruded and granulated to obtain the product. Among them, the flame retardant composite is prepared by compounding hyperbranched triazine charring agent, ammonium polyphosphate, and antimony trioxide in a weight ratio of 3:2:1.

[0075] Among them, the head temperature is 190 °C, the temperature of the first zone is 200 °C, the temperature of the second zone is 210 °C, the temperature of the third zone is 220 °C, the temperature of the fourth zone is 210 °C, and the temperature of the fifth zone is 200 °C.

[0076] Comparative Example 2

[0077] Step 1: Polypropylene and octa(epoxypropyl)silsesquioxane are dried in a vacuum oven at 80 °C for 12 h to remove surface moisture in a weight ratio of 100:10. Ammonium octamolybdate is added in a weight ratio of 100:20 and stirred and mixed. The stirring rate is 1000 rpm to obtain a premix. The premix is melt granulated to obtain a first mixture. The first mixture is dried in a vacuum oven at 80 °C for 8 h and irradiated with γ-rays using 60 a Co source to obtain the pre-irradiated silsesquioxane-reinforced polypropylene. The irradiation dose is 40 kGy and the irradiation dose rate is 80 kGy / h.

[0078] Step 2: 78 parts by weight of the pre-irradiated silsesquioxane-reinforced polypropylene, 15 parts by weight of a flame retardant composite, 1 part by weight of zirconium phosphate nanometer, 1.5 parts by weight of polyethylene wax, and 0.3 part by weight of antioxidant 1010 are placed into a reaction kettle for melt blending. The shear rate is 100 rpm and the mixture is mixed at 180 °C for 15 min. The blend is extruded and granulated to obtain a high-strength flame retardant plastic. The flame retardant composite is a super-branched triazine charring agent, melamine polyphosphate, and antimony trioxide compounded in a weight ratio of 2:1:1.

[0079] Among them, the head temperature is 190 °C, the temperature of the first zone is 200 °C, the temperature of the second zone is 210 °C, the temperature of the third zone is 220 °C, the temperature of the fourth zone is 210 °C, and the temperature of the fifth zone is 200 °C.

[0080] Comparative Example 3

[0081] Step 1: Polypropylene and octa(epoxypropyl)silsesquioxane are dried in a vacuum oven at 80 °C for 12 h to remove surface moisture and liquid nitrogen is introduced for stirring and mixing in a weight ratio of 100:10. The stirring rate is 1000 rpm to obtain a premix. The premix is melt granulated to obtain a first mixture. The first mixture is dried in a vacuum oven at 80 °C for 8 h and irradiated with γ-rays using 60 a Co source to obtain the pre-irradiated silsesquioxane-reinforced polypropylene. The irradiation dose is 40 kGy and the irradiation dose rate is 80 kGy / h.

[0082] Step 2: 78 parts by weight of the pre-irradiated silsesquioxane-reinforced polypropylene, 15 parts by weight of a flame retardant composite, 1 part by weight of zirconium phosphate nanometer, 1.5 parts by weight of polyethylene wax, and 0.3 part by weight of antioxidant 1010 are placed into a reaction kettle for melt blending. The shear rate is 100 rpm and the mixture is mixed at 180 °C for 15 min. The blend is extruded and granulated to obtain a high-strength flame retardant plastic. The flame retardant composite is a super-branched triazine charring agent, melamine polyphosphate, and antimony trioxide compounded in a weight ratio of 2:1:1.

[0083] Among them, the head temperature is 190°C, the temperature of zone 1 is 200°C, the temperature of zone 2 is 210°C, the temperature of zone 3 is 220°C, the temperature of zone 4 is 210°C, and the temperature of zone 5 is 200°C.

[0084] Comparative Example 4

[0085] Step 1: Mix polypropylene and octa-epoxycage silsesquioxane in a weight ratio of 100:10, and dry them in a vacuum oven at 80°C for 12 h to remove surface moisture. Add ammonium octamolybdate in a weight ratio of 100:20 and introduce liquid nitrogen for stirring and mixing. The stirring rate is 1000 rpm to obtain a premix. Melt and granulate the premix to obtain the first mixture. Dry the first mixture in a vacuum oven at 80°C for 8 h, and use 60 a Co source to perform γ-irradiation treatment on the first mixture to obtain the pre-irradiated cage silsesquioxane-reinforced polypropylene. Among them, the irradiation dose is 40 kGy, and the irradiation dose rate is 80 kGy / h.

[0086] Step 2: Weigh 78 parts of the pre-irradiated cage silsesquioxane-reinforced polypropylene, 15 parts of hyperbranched triazine charring agent, 1 part of nanozirconium phosphate, 1.5 parts of polyethylene wax, and 0.3 part of antioxidant 1010 into a reaction kettle for melt blending. The shear rate is 100 rpm, and the mixture is mixed at 180°C for 15 min. Extrude and granulate the blend to obtain the high-strength flame-retardant plastic.

[0087] Among them, the head temperature is 190°C, the temperature of zone 1 is 200°C, the temperature of zone 2 is 210°C, the temperature of zone 3 is 220°C, the temperature of zone 4 is 210°C, and the temperature of zone 5 is 200°C.

[0088] Comparative Example 5

[0089] Step 1: Mix polypropylene and octa-epoxycage silsesquioxane in a weight ratio of 100:10, and dry them in a vacuum oven at 80°C for 12 h to remove surface moisture. Add ammonium octamolybdate in a weight ratio of 100:20 and introduce liquid nitrogen for stirring and mixing. The stirring rate is 1000 rpm to obtain a premix. Melt and granulate the premix to obtain the first mixture.

[0090] Step 2: Weigh 78 parts of the first mixture in Step 1, 15 parts of a flame retardant composite, 1 part of nanozirconium phosphate, 1.5 parts of polyethylene wax, and 0.3 part of antioxidant 1010 into a reaction kettle for melt blending. The shear rate is 100 rpm, and the mixture is mixed at 180°C for 15 min. Extrude and granulate the blend to obtain the high-strength flame-retardant plastic. Among them, the flame retardant composite is composed of a hyperbranched triazine charring agent, melamine polyphosphate, and antimony trioxide in a weight ratio of 2:1:1.

[0091] Among them, the head temperature is 190 °C, the temperature of the first zone is 200 °C, the temperature of the second zone is 210 °C, the temperature of the third zone is 220 °C, the temperature of the fourth zone is 210 °C, and the temperature of the fifth zone is 200 °C.

[0092] Comparative Example 6

[0093] Step 1: Dry polypropylene in a vacuum oven at 80 °C for 12 h to remove surface moisture. Add polypropylene and ammonium octamolybdate to the reaction vessel in a weight ratio of 100:20 and introduce liquid nitrogen for stirring and mixing. The stirring rate is 1000 rpm to obtain a premix. Granulate the premix by melt extrusion to obtain the first mixture. Dry the first mixture in a vacuum oven at 80 °C for 8 h, and use 60 a Co source to perform γ-irradiation treatment on the first mixture to obtain the pre-irradiated polypropylene. Among them, the irradiation dose is 40 kGy, and the irradiation dose rate is 80 kGy / h.

[0094] Step 2: Weigh 78 parts of pre-irradiated cage-like silsesquioxane-reinforced polypropylene, 15 parts of flame retardant composite, 1 part of nanozirconium phosphate, 1.5 parts of polyethylene wax, and 0.3 part of antioxidant 1010 into a reaction kettle for melt blending. The shear rate is 100 rpm, and the mixture is mixed at 180 °C for 15 min. Extrude and granulate the blend to obtain the high-strength flame retardant plastic. Among them, the flame retardant composite is composed of a hyperbranched triazine charring agent, melamine polyphosphate, and antimony trioxide in a weight ratio of 2:1:1.

[0095] Among them, the head temperature is 190 °C, the temperature of the first zone is 200 °C, the temperature of the second zone is 210 °C, the temperature of the third zone is 220 °C, the temperature of the fourth zone is 210 °C, and the temperature of the fifth zone is 200 °C.

[0096] Use scanning electron microscope images to characterize the premixes obtained in Example 1 and Comparative Example 2. The results are as Figure 1 and 2 shown. The premix after introducing liquid nitrogen in Example 1 is evenly dispersed, while the premix in Comparative Example 2 shows agglomeration.

[0097] Perform the following performance tests on the high-strength flame retardant plastics in Examples 1-7 and Comparative Examples 1-6:

[0098] 1. The sheet meets the UL-94 / 3.2 mm test requirements, and the fire rating is V0.

[0099] 2. The limiting oxygen index of the flame retardant polypropylene is determined by the oxygen index method according to GB / T 2406.2-2009 for the standard of combustion behavior.

[0100] 3. Impact strength and tensile strength tests.

[0101]

[0102]

[0103] The above results show that:

[0104] In Example 1, the flame retardant is melamine polyphosphate (MPP), and its synergistic effect between the acid source and the gas source is better than that of ammonium polyphosphate (APP) in Example 2. Therefore, the LOI is higher. In Example 2, due to the lower decomposition temperature of APP, the thermal stability may be slightly reduced, resulting in a slightly lower impact strength.

[0105] It can be seen from Example 1 and Comparative Example 1 that when directly using commercially available polypropylene without adding pre-irradiated cage-like silsesquioxane-reinforced polypropylene flame-retardant plastics, there is a lack of nano-reinforcement and interfacial crosslinking, and the matrix strength decreases significantly. Although it can pass the flame retardancy test to reach V-2, its impact strength and tensile strength both decrease significantly.

[0106] Combined with Figure 1 and Figure 2 It can be seen from Example 1 and Comparative Example 2 that without introducing liquid nitrogen for reaction, agglomeration is likely to occur. Due to the different surface energies and particle sizes, friction is likely to occur during the mixing and shearing process, resulting in adhesion and thus agglomeration, leading to poor mechanical strength. On the other hand, poor dispersion leads to a decrease in the synergistic efficiency between the flame retardant and POSS, and an increase in the porosity of the carbon layer.

[0107] It can be seen from Example 1 and Comparative Example 3 that without adding ammonium octamolybdate, the crosslinking degree of polypropylene and cage-like silsesquioxane cannot be improved, and a crosslinked structure cannot be fully formed. Therefore, the mechanical strength and flame retardant performance decrease.

[0108] It can be seen from Example 1 and Comparative Example 4 that without using the flame retardant composite and only using the hyperbranched triazine charring agent, there is a lack of synergy between the acid source (MPP) and the gas source (antimony trioxide), and the expanded carbon layer is incomplete. A single flame retardant cannot form a multi-layer carbon-gas barrier structure, and the flame retardant effect is weakened.

[0109] It can be seen from Example 1 and Comparative Example 5 that without using irradiation and directly pre-mixing, POSS and PP are only physically mixed, the interfacial bonding is weak, and interfacial peeling is likely to occur. A chemical crosslinked network is not formed, and the crack propagation resistance decreases.

[0110] It can be seen from Example 1 and Comparative Example 6 that without adding cage-like silsesquioxane and only irradiating polypropylene and molybdenum salts, the silicon-oxygen skeleton of POSS lacks the strengthening effect on the carbon layer, and the flame retardant efficiency is low. Without the synergistic carbon formation of POSS, the carbon layer is prone to collapse during combustion and cannot inhibit dripping.

[0111] It can be seen that the high-strength flame-retardant plastic provided by the embodiments of the present application has stable charring properties and mechanical properties. By using pre-irradiated cage-like octasiloxane to reinforce polypropylene, free radicals are generated on the surface of the cage-like octasiloxane, which can form chemical bonds with the polypropylene chains, enhancing the interfacial bonding force, thereby offsetting the loss of mechanical properties caused by the addition of the flame retardant. On the other hand, it offsets the problem of poor thermal stability of polypropylene after irradiation. At the same time, the cross-linked network of cage-like octasiloxane and polypropylene generated by the irradiation treatment can form a graphite-like carbon layer structure with high thermal stability during the combustion process, thereby protecting the internal matrix and delaying its degradation process. Furthermore, it also increases the melt strength, providing a higher shear stress in the subsequent blending stage, forcing the flame retardant composite particles to break and disperse evenly. The hyperbranched triazine charring agent adsorbs other flame retardant components through molecular chain entanglement. Its highly branched three-dimensional structure quickly cross-links to form a dense carbon layer during combustion, and the pre-irradiated POSS enhances the rigidity of the carbon layer skeleton through chemical cross-linking, making the carbon layer not easily cracked at high temperatures. Further inhibiting agglomeration ensures the balance of flame retardancy efficiency and mechanical properties.

[0112] It can be understood that the above embodiments are merely exemplary embodiments adopted to illustrate the principles of the present invention. However, the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also regarded as the protection scope of the present invention.

Claims

1. A high-strength flame-retardant plastic, characterized in that: The invention is composed of the following components by weight: 70-94 parts of pre-irradiated cage silsesquioxane reinforced polypropylene, 10-25 parts of flame retardant compound, 0.5-5 parts of flame retardant synergist, 0.5-2.1 parts of lubricant, and 0.4-0.8 parts of antioxidant; The flame retardant compound comprises at least two of a hyperbranched triazine carbon former, ammonium polyphosphate, melamine polyphosphate and antimony trioxide.

2. The high-strength flame-retardant plastic according to claim 1, characterized in that The flame retardant composite is prepared by compounding a hyperbranched triazine carbon former, melamine polyphosphate and antimony trioxide in a weight ratio of 2:1:

1.

3. The high-strength flame-retardant plastic according to claim 1, characterized in that: The flame retardant composite is prepared by compounding a hyperbranched triazine carbon former, ammonium polyphosphate and antimony trioxide in a weight ratio of 3:2:

1.

4. The high-strength flame-retardant plastic according to any one of claims 1 to 3, characterized in that: The preparation method of the pre-irradiated cage-type silsesquioxane reinforced polypropylene, The following steps are included: The polypropylene and the cage-type silsesquioxane are dried in a vacuum oven at 60° C. to 80° C. for 10 to 12 hours to remove surface moisture, and molybdenum salt powder is added and liquid nitrogen is introduced and stirred and mixed at a stirring rate of 1000 rpm to 1500 rpm to obtain a premix; Melting and granulating the premix to obtain a first mixture; The first mixture was dried in a vacuum oven at 60°C to 80°C for 8h to 10h, and then 60 The first mixture is subjected to γ-irradiation treatment using a Co source to obtain the pre-irradiated cage-type silsesquioxane reinforced polypropylene.

5. The high-strength flame-retardant plastic according to claim 4, characterized in that: The irradiation treatment parameters are: irradiation dose rate of 30 kGy / h to 80 kGy / h, irradiation dose of 40 kGy to 80 kGy, and irradiation time of 0.5 h to 2 h.

6. The high-strength flame-retardant plastic according to claim 4, characterized in that: The weight ratio of the polypropylene to the cage-type silsesquioxane is 100:(10-20), and the weight ratio of the polypropylene to the molybdenum salt is 100:(12-35).

7. The high-strength flame-retardant plastic according to claim 4, characterized in that: The molybdenum salt is any one of sodium molybdate, ammonium octamolybdate and potassium molybdate.

8. The high-strength flame-retardant plastic according to claim 7, characterized in that The flame retardant synergist is nano zirconium phosphate.

9. The high-strength flame-retardant plastic according to claim 4, characterized in that: The polypropylene has a melt index of 1.8 g / min to 3.5 g / min, an isotacticity of 98.5%, and a relative molecular mass distribution M w / M n ≥6, ash content ≤0.03%.

10. A method for preparing a high-strength flame-retardant plastic according to any one of claims 1 to 9, characterized in that: The following steps are involved: Pre-irradiated cage-type silsesquioxane reinforced polypropylene, flame retardant compound, flame retardant synergist, lubricant and antioxidant are placed in a reaction kettle and blended by weight. The mixture is mixed at a shear rate of 100 to 200 rpm and a temperature of 180 to 220° C. for 10 to 15 minutes, and granulated to obtain a high-strength flame-retardant plastic.

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