High-performance polypropylene-based low-smoke halogen-free cable material with synergistic flame-retardant effect and preparation method thereof

Abstract

The invention discloses a high-performance polypropylene-based low-smoke halogen-free cable material with a synergistic flame-retardant effect and a preparation method thereof, and belongs to the field of flame retardance of high polymer materials. The invention aims to solve the problems of low flame-retardant efficiency and poor mechanical and physical properties and electrical properties of a polypropylene-based low-smoke halogen-free cable material which is synergistically improved. The cable material is prepared from the following components in percentage by mass: 10%-60% of thermoplastic polypropylene, 0%-30% of maleic anhydride grafted polypropylene, 12%-80% of a flame retardant, 0%-60% of a synergistic flame retardant, 10%-30% of an elastomer and 0.1%-3% of an auxiliary agent. The vertical combustion of the flame-retardant cable material can reach the V-0 level under the UL-94 standard, the LOI reaches 32.6%, the elongation at break reaches 513.04%, and the flame-retardant cable material is environmentally friendly, low in smoke and even free of smoke in the flame-retardant process and relatively excellent in electrical property.

Description

Technical Field

[0001] The present invention belongs to the field of flame retardant polymer materials, and in particular relates to a high-performance polypropylene-based low-smoke halogen-free cable material with a synergistic flame retardant effect and a preparation method thereof. Background Art

[0002] Since the 21st century, green and environmentally friendly concepts have gradually become major goals of social development. Polypropylene has attracted much attention due to its non-toxicity, recyclability, and excellent electrical properties. However, it is highly flammable and has a low limiting oxygen index. Combustion produces molten droplets and thick smoke, threatening personnel safety and limiting its application. Halogen-containing flame retardants were once used to flame-retard PP. While effective, they release large amounts of harmful gases during combustion, leading to their gradual restriction. With technological advances, various halogen-free flame retardants, such as metal hydroxides like aluminum hydroxide (ATH) and magnesium hydroxide (MDH), as well as phosphorus-nitrogen flame retardants, have been widely researched and applied because they produce less smoke and are halogen-free, thus avoiding the production of toxic and harmful gases such as hydrogen halides. These low-smoke, halogen-free flame-retardant materials not only exhibit excellent flame retardancy, effectively preventing the spread of flames, but also maintain mechanical properties while maintaining flame retardancy, facilitating production and application.

[0003] However, the flame retardant effect of a single flame retardant on PP is often unsatisfactory. Take ATH as an example: when used alone as a flame retardant in the ATH flame retardant process, a relatively high content is required to achieve a certain flame retardant grade. Because the surface is rich in polar hydroxyl groups, while the PP matrix is ​​non-polar, the two have poor compatibility. This makes it impossible to melt-blend PP with large amounts of ATH during the melt blending process. Forcibly increasing the ATH addition level, while it can improve flame retardancy to a certain extent, it will destroy the material structure and significantly degrade the material's mechanical properties, resulting in a significant decrease in mechanical indicators such as tensile strength and elongation at break, making it unable to meet actual use requirements. Furthermore, a high ATH content increases the material's viscosity, impairing its fluidity during processing. In processes such as extrusion and injection molding, higher processing temperatures and pressures are required, increasing processing difficulty and energy consumption, and may also cause increased wear on processing equipment.

[0004] To address the problems of low flame retardant efficiency and material performance degradation associated with single flame retardants, a synergistic flame retardant strategy can be adopted. Currently, research on synergistic flame retardants is still at the stage of developing various combinations of flame retardants, with phosphorus-nitrogen flame retardants being the most commonly used. Nitrogen-based flame retardants can release inert nitrogen to dilute the oxygen concentration in the combustion zone, slowing flame propagation in the gas phase. Phosphorus-based flame retardants form a carbonized layer in the condensed phase, blocking oxygen from contact with the fuel and inhibiting the release of toxic gases in the gas phase.

[0005] Although the synergistic flame retardant system has achieved remarkable results in the application of PP-based materials, achieving high flame retardancy at a lower flame retardant content and having little effect on mechanical and electrical properties; however, there is still a problem of poor compatibility between PP and flame retardants. Summary of the Invention

[0006] This invention builds a synergistic flame-retardant system based on PP and ATH. It introduces the phosphorus-based flame retardant piperazine pyrophosphate (PAPP) as a synergistic flame retardant, and PP grafted maleic anhydride (MAH) (PP-g-MAH) as a system compatibility regulator. This further improves the overall performance of the flame-retardant system, aiming to synergistically address the low flame-retardant efficiency and poor mechanical, physical, and electrical properties of polypropylene-based low-smoke, halogen-free cable materials. Overall, this provides a new direction for the development of high-performance PP-based flame-retardant cable materials.

[0007] Based on this, the present invention provides a high-performance polypropylene-based low-smoke halogen-free cable material with a synergistic flame retardant effect, which is made of 10%-60% thermoplastic polypropylene, 0%-30% maleic anhydride grafted polypropylene, 12%-80% flame retardant, 0%-60% synergistic flame retardant, 10%-30% elastomer and 0.1%-3% additives, calculated by mass fraction.

[0008] Preferably, the invention is made of 17.85%-42.85% thermoplastic polypropylene, 0%-30% maleic anhydride grafted polypropylene, 12%-65% flame retardant, 0%-28% synergistic flame retardant, 10%-25% elastomer and 0.1%-0.15% auxiliary agent, calculated by mass fraction.

[0009] More preferably, the composite material is made of 22% thermoplastic polypropylene, 19.85% maleic anhydride grafted polypropylene, 20% flame retardant, 20% synergistic flame retardant, 18% elastomer and 0.15% additive, calculated by mass percentage.

[0010] It is further defined that the flame retardant is aluminum hydroxide flame retardant (ATH).

[0011] It is further defined that the synergistic flame retardant is piperazine pyrophosphate (PAPP).

[0012] It is further defined that the auxiliary agent is an antioxidant.

[0013] It is further defined that the antioxidant is one of antioxidant 1010, antioxidant 1024, and antioxidant 1076.

[0014] It is further defined that the thermoplastic polypropylene is a random copolymer, and its brand is one or more of K8303, K8003, K7002, K4912 and B4808 in any ratio, and K8303 is purchased from Beijing Yanshan Branch of China Petrochemical Corporation.

[0015] It is further defined that the maleic anhydride grafted modified polypropylene is a purchased PP-g-MAH mixture, the grafting rate of the maleic anhydride grafted polypropylene is 1% to 2%, and it is purchased from DuPont Company of the United States, model number Fusabond P353.

[0016] It is further defined that the elastomer is POP, purchased from The Dow Chemical Company, model number is Versify 2200.

[0017] Compared with traditional PP, after MAH grafting, the anhydride groups in MAH react with the hydroxyl groups on the surface of ATH to form ester bonds, which enhances the interfacial adhesion, inhibits the migration of PAPP, improves the dispersion and compatibility of the flame retardant in the PP matrix, avoids the agglomeration of the flame retardant, and thus enhances the overall performance of the material. Compared with traditional single flame retardants, the combination of ATH and PAPP can exert excellent flame retardant effects at a lower addition amount. In polypropylene-based cable materials, PAPP releases polyol esters from the acid source during combustion as an inorganic acid dehydrating agent, which reacts with polyols to form a foamy carbon layer; ATH decomposes to produce aluminum oxide to provide skeleton support for the carbon layer, and the two cooperate with each other to significantly improve the flame retardant performance. The flame retardant cable material of the present invention can reach the V-0 level under the UL-94 standard during vertical combustion, the LOI reaches 32.6%, and the elongation at break reaches 513.04%. The flame retardant process is environmentally friendly, low in smoke or even smokeless, and the electrical properties are relatively excellent.

[0018] The present invention also provides a method for preparing the above-mentioned high-performance polypropylene-based low-smoke halogen-free cable material with synergistic flame retardant effect, which is carried out by the following steps:

[0019] Step 1: Set the temperature of each zone of the torque rheometer between 170°C and 185°C, add thermoplastic polypropylene, maleic anhydride grafted polypropylene and elastomer into the torque rheometer, and mix at a speed of 60 rpm for 3 minutes;

[0020] Step 2: After the torque is balanced, adjust the speed to 30 rpm and add the flame retardant twice. After each addition, mix at 30 rpm for 3 minutes;

[0021] Step 3: Then control the speed of the torque rheometer at 30 rpm, add the synergistic flame retardant powder, and mix at 30 rpm for 3 minutes;

[0022] Step 4: Then control the speed of the torque rheometer at 30 rpm, add the additive, and mix at 30 rpm for 3 minutes;

[0023] Step 5: Finally, adjust the torque rheometer to 60 rpm, mix for 10 minutes, take out the pellets, and the polypropylene flame retardant cable material is prepared;

[0024] The present invention also provides a method for preparing a high-performance polypropylene-based low-smoke halogen-free cable material with a synergistic flame retardant effect. Specifically, the above-mentioned cable material or the cable material prepared by the above-mentioned method is placed in a flat-plate vulcanizer, hot-pressed in a step-by-step pressure-increasing manner, pressurized and cooled using a water-cooled flat-plate vulcanizer, and then vacuum-dried to obtain the flame-retardant material.

[0025] It is further defined that under the temperature condition of 170℃-185℃, the step-by-step pressurization method is to set the pressure to 5MPa, 10MPa, and 15MPa respectively for 5 minutes each.

[0026] The beneficial effects of the present invention are as follows:

[0027] Compared with traditional PP, after adding PP-g-MAH, the anhydride groups in MAH will undergo esterification reaction with the hydroxyl groups in ATH to form ester bonds, effectively enhancing the interfacial adhesion between the matrix resin and the flame retardant system, while inhibiting the migration of ATH and PAPP, and improving the dispersion and compatibility of the flame retardant in the PP matrix, avoiding flame retardant agglomeration, thereby significantly enhancing the comprehensive performance of the material.

[0028] Compared with traditional single flame retardants, the combination of the two can achieve excellent flame retardant effects at lower addition amounts. In polypropylene-based cable materials, PAPP releases polyol esters from the acid source during combustion as an inorganic acid dehydrating agent, which reacts with polyols to form a foamy carbon layer; ATH decomposes to produce aluminum oxide to provide a skeleton support for the carbon layer. The two work together to significantly improve the flame retardant properties. The flame retardant cable material of the present invention can reach the V-0 level under the UL-94 standard during vertical combustion, with an LOI of 32.6% and an elongation at break of 513.04%. The flame retardant process is environmentally friendly, low in smoke or even smokeless, and has relatively excellent electrical properties. DETAILED DESCRIPTION

[0029] The technical solution of the present invention is further described below with reference to the embodiments, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention that does not depart from the spirit and scope of the technical solution of the present invention should be included in the scope of protection of the present invention.

[0030] Example 1:

[0031] In this embodiment, a high-performance polypropylene-based low-smoke zero-halogen cable material with a synergistic flame retardant effect comprises the following components, calculated by mass percentage: 20% polypropylene (PP) (purchased from Beijing Yanshan Branch of Sinopec, model K8303), 19.85% PP-g-MAH (grafting rate 1.5%), 25% ATH, 25% PAPP, 10wt% POP, and 0.15% antioxidant 1035; purchased from DuPont, model Fusabond P353. The specific steps are as follows:

[0032] The temperature of the first, second and third zones of the torque rheometer were all set at 180°C. PP, maleic anhydride grafted polypropylene (PP-g-MAH) and POP were added to the torque rheometer and mixed at 180°C and 60 rpm for 3 minutes.

[0033] After the torque is balanced, the speed is adjusted to 30 rpm, and the flame retardant ATH is added twice. After each addition, the speed is kept at 30 rpm for 3 minutes.

[0034] After the flame retardant is completely added, the torque rheometer speed is controlled at 30 rpm, and then the synergistic flame retardant powder (PAPP) is added and mixed at 30 rpm for 3 minutes;

[0035] Then the torque rheometer speed was controlled at 30 rpm, the auxiliary antioxidant 1035 was added, and the mixture was mixed at 30 rpm for 3 min;

[0036] Finally, the torque rheometer was adjusted to 60 rpm, and the pellets were taken out after mixing for 10 minutes, and the preparation of the polypropylene flame retardant cable material was completed.

[0037] In this embodiment, a method for preparing a high-performance polypropylene-based low-smoke halogen-free cable material with a synergistic flame retardant effect is carried out according to the following steps: the polypropylene flame-retardant cable material is hot-pressed in a flat-plate vulcanizer by a step-by-step pressurization method. Under a temperature of 180°C, the step-by-step pressurization method is to set the pressure to 5 MPa, 10 MPa, and 15 MPa respectively for 5 minutes each. The material is pressurized and cooled using a water-cooled flat-plate vulcanizer and then vacuum dried to obtain a high-performance polypropylene-based flame-retardant material test piece (S-1).

[0038] Example 2:

[0039] In this embodiment, a high-performance polypropylene-based low-smoke zero-halogen cable material with a synergistic flame retardant effect comprises the following components, calculated by mass percentage: 20% polypropylene (PP) (model K8303 purchased from Beijing Yanshan Branch of Sinopec), 19.85% PP-g-MAH (grafting rate 1.5%), 12% ATH, 28% PAPP, 20wt% POP, and 0.15wt% antioxidant 1035; purchased from DuPont, USA, model Fusabond P353. Specifically, the following steps are performed:

[0040] The temperature of the first, second and third zones of the torque rheometer were all set at 180°C. PP, maleic anhydride grafted polypropylene (PP-g-MAH) and POP were added to the torque rheometer and mixed at 180°C and 60 rpm for 3 minutes.

[0041] After the torque is balanced, the speed is adjusted to 30 rpm, and the flame retardant ATH is added twice. After each addition, the speed is kept at 30 rpm for 3 minutes.

[0042] After the flame retardant is completely added, the torque rheometer speed is controlled at 30 rpm, and then the synergistic flame retardant powder (PAPP) is added and mixed at 30 rpm for 3 minutes;

[0043] Then the torque rheometer speed was controlled at 30 rpm, the auxiliary antioxidant 1035 was added, and the mixture was mixed at 30 rpm for 3 min;

[0044] Finally, the torque rheometer was adjusted to 60 rpm, and the pellets were taken out after mixing for 10 minutes, and the preparation of the polypropylene flame retardant cable material was completed.

[0045] In this embodiment, a method for preparing a high-performance polypropylene-based low-smoke halogen-free cable material with a synergistic flame retardant effect is carried out according to the following steps: the polypropylene flame-retardant cable material is hot-pressed in a flat-plate vulcanizer by a step-by-step pressurization method. Under a temperature of 180°C, the step-by-step pressurization method is to set the pressure to 5 MPa, 10 MPa, and 15 MPa for 5 minutes each. The material is pressurized and cooled using a water-cooled flat-plate vulcanizer and then vacuum dried to obtain a high-performance polypropylene-based flame-retardant material test piece (S-2).

[0046] Example 3

[0047] In this embodiment, a high-performance polypropylene-based low-smoke zero-halogen cable material with a synergistic flame retardant effect comprises the following components, calculated by mass percentage: 22% polypropylene (PP) (model K8303 purchased from Beijing Yanshan Branch of Sinopec), 19.85% PP-g-MAH (grafting rate 1.5%), 15% ATH, 25% PAPP, 18% POP, and 0.15wt% antioxidant 1010; purchased from DuPont, USA, model Fusabond P353. Specifically, the following steps are performed:

[0048] The temperature of the first, second and third zones of the torque rheometer were all set at 180°C. PP, maleic anhydride grafted polypropylene (PP-g-MAH) and POP were added to the torque rheometer and mixed at 180°C and 60 rpm for 3 minutes.

[0049] After the torque is balanced, the speed is adjusted to 30 rpm, and the flame retardant ATH is added twice. After each addition, the speed is kept at 30 rpm for 3 minutes.

[0050] After the flame retardant is completely added, the torque rheometer speed is controlled at 30 rpm, and then the synergistic flame retardant powder (PAPP) is added and mixed at 30 rpm for 3 minutes;

[0051] Then the torque rheometer speed was controlled at 30 rpm, the auxiliary antioxidant 1010 was added, and the mixture was mixed at 30 rpm for 3 min;

[0052] Finally, the torque rheometer was adjusted to 60 rpm, and the pellets were taken out after mixing for 10 minutes, and the preparation of the polypropylene flame retardant cable material was completed.

[0053] In this embodiment, a method for preparing a high-performance polypropylene-based low-smoke halogen-free cable material with a synergistic flame retardant effect is carried out according to the following steps: the polypropylene flame-retardant cable material is hot-pressed in a flat-plate vulcanizer by a step-by-step pressure-increasing method. Under the condition of a temperature of 180°C, the step-by-step pressure-increasing method is to set the pressure at 5MPa, 10MPa, and 15MPa respectively, and then pressurize and cool using a water-cooled flat-plate vulcanizer and then vacuum dry to obtain a high-performance polypropylene-based flame-retardant material test piece (S-3).

[0054] Example 4

[0055] In this embodiment, a high-performance polypropylene-based low-smoke zero-halogen cable material with a synergistic flame retardant effect comprises the following components, calculated by mass percentage: 22% polypropylene (PP) (model K8303 purchased from Beijing Yanshan Branch of Sinopec), 19.85% PP-g-MAH (grafting rate 1.5%), 20% ATH, 20% PAPP, 18% POP, and 0.15wt% antioxidant 1010; purchased from DuPont, USA, model Fusabond P353. Specifically, the following steps are performed:

[0056] The temperature of the first, second and third zones of the torque rheometer were all set at 180°C. PP, maleic anhydride grafted polypropylene (PP-g-MAH) and POP were added to the torque rheometer and mixed at 180°C and 60 rpm for 3 minutes.

[0057] After the torque is balanced, the speed is adjusted to 30 rpm, and the flame retardant ATH is added twice. After each addition, the speed is kept at 30 rpm for 3 minutes.

[0058] After the flame retardant is completely added, the torque rheometer speed is controlled at 30 rpm, and then the synergistic flame retardant powder (PAPP) is added and mixed at 30 rpm for 3 minutes;

[0059] Then the torque rheometer speed was controlled at 30 rpm, the auxiliary antioxidant 1010 was added, and the mixture was mixed at 30 rpm for 3 min;

[0060] Finally, the torque rheometer was adjusted to 60 rpm, and the pellets were taken out after mixing for 10 minutes, and the preparation of the polypropylene flame retardant cable material was completed.

[0061] In this embodiment, a method for preparing a high-performance polypropylene-based low-smoke halogen-free cable material with a synergistic flame retardant effect is carried out according to the following steps: the polypropylene flame-retardant cable material is hot-pressed in a flat-plate vulcanizer by a step-by-step pressurization method. Under a temperature of 180°C, the step-by-step pressurization method is to set the pressure to 5 MPa, 10 MPa, and 15 MPa for 5 minutes each. The material is pressurized and cooled using a water-cooled flat-plate vulcanizer and then vacuum-dried to obtain a high-performance polypropylene-based flame-retardant material test piece (S-4).

[0062] Example 5

[0063] In this embodiment, a high-performance polypropylene-based low-smoke zero-halogen cable material with a synergistic flame retardant effect comprises the following components, calculated by mass percentage: 20% polypropylene (PP) (model K8303 purchased from Beijing Yanshan Branch of Sinopec), 29.85% PP-g-MAH (grafting rate 1.5%), 28% ATH, 12% PAPP, 10% POP, and 0.15wt% antioxidant 1076; purchased from DuPont, USA, model Fusabond P353. Specifically, the process is as follows:

[0064] The temperature of the first, second and third zones of the torque rheometer were all set at 180°C. PP, maleic anhydride grafted polypropylene (PP-g-MAH) and POP were added to the torque rheometer and mixed at 180°C and 60 rpm for 3 minutes.

[0065] After the torque is balanced, the speed is adjusted to 30 rpm, and the flame retardant ATH is added twice. After each addition, the speed is kept at 30 rpm for 3 minutes.

[0066] After the flame retardant is completely added, the torque rheometer speed is controlled at 30 rpm, and then the synergistic flame retardant powder (PAPP) is added and mixed at 30 rpm for 3 minutes;

[0067] Then the torque rheometer speed was controlled at 30 rpm, the auxiliary antioxidant 1076 was added, and the mixture was mixed at 30 rpm for 3 min;

[0068] Finally, the torque rheometer was adjusted to 60 rpm, and the pellets were taken out after mixing for 10 minutes, and the preparation of the polypropylene flame retardant cable material was completed.

[0069] In this embodiment, a method for preparing a high-performance polypropylene-based low-smoke halogen-free cable material with a synergistic flame retardant effect is carried out according to the following steps: the polypropylene flame-retardant cable material is hot-pressed in a flat-plate vulcanizer by a step-by-step pressurization method. Under a temperature of 180°C, the step-by-step pressurization method is to set the pressure to 5 MPa, 10 MPa, and 15 MPa for 5 minutes each. The material is pressurized and cooled using a water-cooled flat-plate vulcanizer and then vacuum dried to obtain a high-performance polypropylene-based flame-retardant material test piece (S-5).

[0070] Example 6:

[0071] In this embodiment, a high-performance polypropylene-based low-smoke zero-halogen cable material with a synergistic flame retardant effect comprises the following components, calculated by mass percentage: 20% polypropylene (PP) (model K8303 purchased from Beijing Yanshan Branch of Sinopec), 29.85% PP-g-MAH (grafting rate 1.5%), 15% ATH, 15% PAPP, 20% POP, and 0.15wt% antioxidant 1076; purchased from DuPont, USA, model Fusabond P353. Specifically, the following steps are performed:

[0072] The temperature of the first, second and third zones of the torque rheometer were all set at 180°C. PP, maleic anhydride grafted polypropylene (PP-g-MAH) and POP were added to the torque rheometer and mixed at 180°C and 60 rpm for 3 minutes.

[0073] After the torque is balanced, the speed is adjusted to 30 rpm, and the flame retardant ATH is added twice. After each addition, the speed is kept at 30 rpm for 3 minutes.

[0074] After the flame retardant is completely added, the torque rheometer speed is controlled at 30 rpm, and then the synergistic flame retardant powder (PAPP) is added and mixed at 30 rpm for 3 minutes;

[0075] Then the torque rheometer speed was controlled at 30 rpm, the auxiliary antioxidant 1076 was added, and the mixture was mixed at 30 rpm for 3 min;

[0076] Finally, the torque rheometer was adjusted to 60 rpm, and the pellets were taken out after mixing for 10 minutes, and the preparation of the polypropylene flame retardant cable material was completed.

[0077] In this embodiment, a method for preparing a high-performance polypropylene-based low-smoke halogen-free cable material with a synergistic flame retardant effect is carried out according to the following steps: the polypropylene flame-retardant cable material is hot-pressed in a flat-plate vulcanizer by a step-by-step pressurization method. Under a temperature of 180°C, the step-by-step pressurization method is to set the pressure to 5 MPa, 10 MPa, and 15 MPa respectively for 5 minutes each. The material is pressurized and cooled using a water-cooled flat-plate vulcanizer and then vacuum dried to obtain a high-performance polypropylene-based flame-retardant material test piece (S-6).

[0078] Comparative Example 1

[0079] This comparative example provides a method for preparing a polypropylene-based flame retardant material. The polypropylene flame retardant cable material comprises the following components, calculated by mass fraction: 42.85% PP, 20% ATH, 20% PAPP, 18% POP and 0.15% antioxidant 1010.

[0080] This comparative example is based on a polypropylene-based flame retardant material, and the specific preparation method steps are as follows:

[0081] PP and POP were added to the torque rheometer, the speed was set to 60 rpm, and melt-mixed at 180 ° C for 3 minutes. After the torque was balanced, the speed was adjusted to 30 rpm, and the flame retardant was added twice. After each addition, the mixture was mixed for 3 minutes. After the flame retardant was completely added, the synergistic flame retardant was added and mixed for 3 minutes. Finally, the antioxidant and other additives were added and mixed for 3 minutes. Finally, the speed was adjusted to 60 rpm. After mixing for 10 minutes, the pellets were taken out and the preparation of the polypropylene flame retardant cable material was completed. The polypropylene flame retardant cable material was then pressed into shape in a step-by-step pressure-increasing manner at 5 MPa, 10 MPa, and 15 MPa at 180 ° C in a flat vulcanizer. It was cooled in a water-cooled flat vulcanizer and vacuum-dried for 24 hours to obtain a polypropylene flame retardant material specimen (D-1).

[0082] Comparative Example 2

[0083] This comparative example provides a method for preparing a polypropylene-based flame retardant material. The polypropylene flame retardant cable material comprises the following components, calculated by mass fraction: 17.85% PP, 65% ATH, 18% POP and 0.15% antioxidant 1010.

[0084] This comparative example is based on a polypropylene-based flame retardant material, and the specific preparation method steps are as follows:

[0085] PP and POP were added to the torque rheometer, the speed was set to 60 rpm, and melt-mixed at 180 ° C for 3 minutes. After the torque was balanced, the speed was adjusted to 30 rpm, and the flame retardant was added three times. After each addition, the mixture was mixed for 3 minutes. After the flame retardant was completely added, the antioxidant and other additives were added and mixed for 3 minutes. Finally, the speed was adjusted to 60 rpm. After mixing for 10 minutes, the pellets were taken out and the preparation of polypropylene flame retardant cable material was completed. The polypropylene flame retardant cable material was then pressed into shape in a step-by-step pressure manner at 5 MPa, 10 MPa, and 15 MPa at a pressure of 5 minutes each in a flat vulcanizer at 180 ° C, and cooled in a water-cooled flat vulcanizer and vacuum dried for 24 hours to obtain a polypropylene flame retardant material test piece (D-2).

[0086] Comparative Example 3

[0087] This comparative example provides a preparation method of a polypropylene-based flame retardant material. The polypropylene flame retardant cable material comprises the following components, calculated by mass fraction: 39.85% PP, 35% ATH, 25% POP and 0.15% antioxidant 1010.

[0088] This comparative example is based on a polypropylene-based flame retardant material, and the specific preparation method steps are as follows:

[0089] PP and POP were added to the torque rheometer, the speed was set to 60 rpm, and melt-mixed at 180 ° C for 3 minutes. After the torque was balanced, the speed was adjusted to 30 rpm, and the flame retardant was added three times. After each addition, the mixture was mixed for 3 minutes. After the flame retardant was completely added, the antioxidant and other additives were added and mixed for 3 minutes. Finally, the speed was adjusted to 60 rpm. After mixing for 10 minutes, the pellets were taken out and the preparation of polypropylene flame retardant cable material was completed. The polypropylene flame retardant cable material was then pressed into shape in a step-by-step pressure manner at 5 MPa, 10 MPa, and 15 MPa at a pressure of 5 minutes each in a flat vulcanizer at 180 ° C, and cooled in a water-cooled flat vulcanizer and vacuum dried for 24 hours to obtain a polypropylene flame retardant material test piece (D-3).

[0090] The vertical combustion and LOI tests of the samples from each example and comparative example were performed using a CF-3 horizontal / vertical combustion tester and a JF-3 tester. The results clearly show that in Comparative Example 1, due to the poor compatibility of the unmodified PP with ATH and PAPP, the flame retardant severely agglomerated, preventing effective synergy between ATH and PAPP through interfacial bonding, and thus failing to achieve a proper flame retardant effect. In Comparative Example 2, when the unmodified PP and ATH were flame-retarded alone, the flame retardant effect was good. However, in Comparative Example 3, when the unmodified PP was blended with a small amount of ATH for flame retardant performance, the flame retardant effect was difficult to achieve due to the low amount of flame retardant added. In contrast, Example 4 exhibited the best flame retardant performance, with significantly less ATH added. Its LOI reached 32.6%, and it passed the UL-94 V-0 rating for vertical combustion, significantly outperforming the comparative example and other examples. Its internal mechanism is: ATH decomposes and absorbs heat (heat absorption ≈ 1970 J / g) and forms an AI2O3 barrier, which together construct a dense expanded carbon layer, isolates heat and oxygen, and releases water vapor to dilute combustible gases. PAPP can generate phosphoric acid substances when heated to catalyze dehydration into carbon, and decomposes when heated to produce inert gases to inhibit free radical chain reactions, thereby achieving flame retardancy.

[0091] The samples prepared in each embodiment and comparative example were cut into standard dumbbell-shaped samples and subjected to stress-strain tests in accordance with the standard of GB / T1040.2-2006, with a tensile speed of 50 mm / min. In order to eliminate test errors, each group of materials was tested five times and the average value was taken. It can be seen from comparative examples 2 and 3 that although adding a large amount of single flame retardant has a good flame retardant effect, the addition of a large amount of ATH will destroy the material structure and significantly deteriorate the mechanical properties of the material; it can be seen from comparative examples 1, 2, and 3 that the PP matrix without MAH modification has poor compatibility with the flame retardant and is prone to agglomeration. The agglomerates have weak interface bonding with the polypropylene matrix, resulting in poor mechanical properties of the material. Combining the test results of comparative example 1 and examples 3 and 4, it can be clearly seen that when the total content of the PAPP / ATH synergistic flame retardant is the same (when 40 wt% is added), the mechanical properties of the material are significantly improved. Example 4 achieved the best results, with an elongation at break of 513.04% and a tensile strength of 18.29 MPa. This is attributed to the significant improvement in interfacial compatibility between the substrate and the flame retardant achieved by the MAH grafting. The flame retardant disperses effectively, evenly distributing stress, and the MAH polar groups enhance interfacial bonding, inhibiting crack propagation. This demonstrates that the MAH grafting modification significantly enhances the mechanical properties of the PP substrate and the PAPP / ATH synergistic flame retardant system. Furthermore, excellent mechanical properties are achieved even with relatively low ATH addition levels.

[0092] The samples of each example and comparative example were subjected to volume resistivity and DC breakdown field strength tests in accordance with GB / T 32129-2015. The experiments showed that the electrical properties of comparative examples 1 and 2 were significantly degraded due to interface defects or the addition of a large amount of a single flame retardant. In contrast, examples 3 and 4 exhibited relatively excellent electrical properties due to their uniform dispersion. The volume resistivity of example 4 reached 6.355×10 15 Ω·cm, with a breakdown field strength of 176.9 kV / mm, significantly superior to the other groups. In a matrix containing PP-g-MAH, the synergistic flame retardancy of ATH and PAPP improves filler dispersion in the matrix resin, reducing defects introduced into the polymer by PAPP aggregation and electric field distortion. Furthermore, the low polarity and excellent insulating properties of ATH restrict ion migration paths, enhancing insulation performance. The synergistic flame retardancy of ATH effectively suppresses localized leakage currents caused by the hygroscopicity of PAPP.

[0093] Table 1: Comparative analysis table

[0094]

[0095] In summary, the PAPP synergistic flame retardant system has achieved remarkable results in the application of PP-based materials. It can achieve a high flame retardant grade at a lower flame retardant content and has little effect on mechanical and electrical properties. By grafting MAH, the problem of poor compatibility between PP and flame retardants can be solved. The polar groups introduced can interact with the polar groups on the surface of the flame retardant through chemical bonds, hydrogen bonds, etc., thereby improving the dispersion and compatibility of the flame retardant in the PP matrix and avoiding flame retardant agglomeration, thereby enhancing the comprehensive performance of the material. Among them, Example 4 has the best overall effect. While significantly reducing the amount of ATH, it significantly enhances the comprehensive performance of the material, with an elongation at break of 513.04%, a tensile strength of 18.29 MPa, an LOI of 32.6%, a UL-94 standard of V-0, a volume resistivity of 6.35×1015Ω·cm, and a DC breakdown field strength of 176.9kV / mm at room temperature.

Claims

1. A high-performance polypropylene-based low-smoke halogen-free cable material with synergistic flame retardant effect, characterized in that: Calculated by mass percentage, the invention is prepared from 10%-60% of thermoplastic polypropylene, 0%-30% of maleic anhydride grafted polypropylene, 12%-80% of flame retardant, 0%-60% of synergistic flame retardant, 10%-30% of elastomer and 0.1%-3% of auxiliary agent.

2. The cable material according to claim 1, characterized in that: Calculated by mass percentage, the invention is prepared from 17.85%-42.85% of thermoplastic polypropylene, 0%-30% of maleic anhydride grafted polypropylene, 12%-65% of flame retardant, 0%-28% of synergistic flame retardant, 10%-25% of elastomer and 0.1%-0.15% of auxiliary agent.

3. The cable material according to claim 1, characterized in that: Calculated by mass percentage, the invention is made of 22% thermoplastic polypropylene, 19.85% maleic anhydride grafted polypropylene, 20% flame retardant, 20% synergistic flame retardant, 18% elastomer and 0.15% additive.

4. The cable material according to claim 1, characterized in that: The flame retardant is aluminum hydroxide.

5. The cable material according to claim 1, characterized in that: The synergistic flame retardant is piperazine pyrophosphate.

6. The cable material according to claim 1, characterized in that: The auxiliary agent is an antioxidant, and the antioxidant is antioxidant 1010, antioxidant 1024 or antioxidant 1076.

7. The cable material according to claim 6, characterized in that: The thermoplastic polypropylene is a random copolymer, and its brand is one of K8303, K8003, K7002, K4912 and B4808, or a combination of several of them in any ratio; the grafting rate of maleic anhydride grafted polypropylene is 1% to 2%.

8. The method for preparing a cable material according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step 1: Set the temperature of each zone of the torque rheometer between 170°C and 185°C, add thermoplastic polypropylene, maleic anhydride grafted polypropylene and elastomer into the torque rheometer, and mix at a speed of 60 rpm for 3 minutes; Step 2: After the torque is balanced, adjust the speed to 30 rpm and add the flame retardant twice. After each addition, mix at 30 rpm for 3 minutes; Step 3: Then control the speed of the torque rheometer at 30 rpm, add the synergistic flame retardant powder, and mix at 30 rpm for 3 minutes; Step 4: Then control the speed of the torque rheometer at 30 rpm, add the additive, and mix at 30 rpm for 3 minutes; Step 5: Finally, adjust the torque rheometer to 60 rpm, mix for 10 minutes, take out the pellets, and the preparation of the polypropylene flame-retardant cable material is completed.

9. A method for preparing a high-performance polypropylene-based low-smoke halogen-free cable material with a synergistic flame retardant effect, characterized in that: The cable material according to any one of claims 1 to 7 or the cable material prepared by the method according to claim 8 is placed in a flat-plate vulcanizer, hot-pressed in a step-by-step pressure manner, pressurized and cooled using a water-cooled flat-plate vulcanizer, and then vacuum-dried to obtain the flame-retardant material.

10. The method according to claim 9, characterized in that: Under the condition of temperature of 170℃-185℃, the step-by-step pressurization method is to set the pressure to 5MPa, 10MPa, and 15MPa respectively for 5 minutes each.

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