Low-density high-strength halogen-free flame-retardant burn-through-resistant long glass fiber reinforced polypropylene composite material as well as preparation method and application thereof

Abstract

The invention discloses a low-density high-strength halogen-free flame-retardant burn-through-resistant long glass fiber reinforced polypropylene composite material, which comprises the following components by weight: 40-80 parts of polypropylene; 10 to 30 parts of continuous glass fiber; 2-6 parts of a compatilizer; 0.1 to 2 parts of an antioxidant; 3-8 parts of a triazine charring agent; 5 to 18 parts of ammonium polyphosphate; 10 to 35 parts of focused piperazine phosphate; and 3-15 parts of hollow glass beads. The obtained material can still keep certain mechanical strength during high-temperature combustion, and the stable high-temperature strength retention rate of a prepared workpiece can be ensured.

Description

Technical Field

[0001] The invention relates to the field of polypropylene composite materials, and in particular to a low-density, high-strength, halogen-free, flame-retardant, burn-through-resistant, long glass fiber reinforced polypropylene composite material and a preparation method and application thereof. Background Art

[0002] With the rapid development of the national economy, high-performance thermoplastic resin-based composite materials have been widely used. Adding reinforcing fibers to thermoplastic resins and modifying the resins to prepare fiber-reinforced thermoplastic resin-based composite materials (new structural composite materials, functional composite materials, etc.) is an effective shortcut for the development of new materials. This has become a consensus in the scientific and industrial communities, and it is also the best technical route to achieve the engineering of general plastics, the functionalization of engineering plastics, and the practical application of special engineering plastics.

[0003] Long fiber reinforced polypropylene composite materials (LFT-PP) have mechanical properties that are difficult to achieve with short fiber reinforced polypropylene. Their high tensile strength, bending strength and modulus have realized the engineering of polypropylene general plastics. They have been widely used in the field of automobile manufacturing and have become an ideal material for the automobile industry to achieve the goal of low cost and high efficiency. They are currently one of the most active composite material development varieties in the world. As the flame retardant and fireproof requirements for the surrounding materials of new energy vehicle battery packs are getting higher and higher, traditional flame retardant composite materials still have problems such as flames burning through materials during short-term high-temperature flame burning, affecting pedestrian safety and insufficient escape time in accidents. To solve this problem, materials need to have excellent flame retardant properties and high-temperature burn-through resistance. Currently, commonly used burn-through fireproof materials mainly include metal aluminum and thermosetting materials, but they have disadvantages such as difficult recycling, high density, long molding cycle, complex processing procedures, increased vehicle weight, and reduced cruising range.

[0004] The Chinese invention patent application with publication number CN117866426 A (application number 202311803851.5) discloses a ceramicized burn-through resistant polyamide composite material and a preparation method thereof. The components of the material are as follows by weight: 100 parts of polyamide resin, 12-18 parts of flame retardant, 15-40 parts of chopped glass fiber, 7-16 parts of glassy flame retardant powder, and 20-60 parts of composite ceramic powder. The technical solution is to react the flame retardant to form carbon during combustion, and to add calcium silicate to isolate heat and reduce the combustion rate. The low-melting point glass powder melts at 500-650°C to isolate oxygen, thereby further improving the material's burn-through resistance. The material's burn-through resistance time can reach 620-730s.

[0005] However, in this invention, all components are mixed evenly and melt-extruded in an extruder, which cannot guarantee the mechanical properties of the material. The flame retardant is prone to partial failure due to shear heat, and the material performance is prone to further decline due to high temperature during combustion, and there is a risk of failure due to stress deformation and burn-through resistance. Summary of the invention

[0006] The purpose of the present invention is to overcome the defects of the prior art and provide a low-density, high-strength, halogen-free, flame-retardant, burn-through-resistant long glass fiber reinforced polypropylene composite material and its preparation method and application, which can be applied to the peripheral materials of new energy vehicle batteries.

[0007] To achieve the above object, the present invention adopts the following technical scheme: a low-density, high-strength, halogen-free, flame-retardant, burn-through-resistant, long glass fiber reinforced polypropylene composite material, comprising the following components in parts by weight: Polypropylene 40-80 parts; 10-30 parts of continuous glass fiber; 2-6 parts of compatibilizer; Antioxidant 0.1-2 parts; 3-8 parts of triazine charring agent; 5-18 parts of ammonium polyphosphate; Focus on piperazine phosphate 10-35 parts; 3-15 parts of hollow glass microspheres.

[0008] In the present invention, a triazine carbonizing agent, ammonium polyphosphate, and focused piperazine phosphate composite flame retardant system are used to produce a synergistic effect and provide excellent flame retardant properties. The addition of hollow glass microspheres is beneficial to the internal low thermal conductivity of the hollow glass microspheres during material combustion, further preventing heat from being transferred inward, and the rapid carbonization of the material surface and the inefficient internal heat conduction further improve the material's burn-through resistance time. At the same time, due to the effect of the long glass fiber reinforcement system, a stable glass fiber skeleton structure is formed inside the system, ensuring that the material can still maintain a certain mechanical strength during high-temperature combustion, and ensuring that the prepared parts have a stable high-temperature strength retention rate.

[0009] The following are the preferred technical solutions of the present invention.

[0010] The polypropylene is commercially available, and is preferably a blend of one or more polypropylenes of different grades having a melt mass flow rate of 90-150 g / 10 min.

[0011] The continuous glass fiber is commercially available, preferably one of Taishan EDR240-T838J and Owens Corning SE4805-2400.

[0012] The hollow glass microspheres are commercially available, and the particle size of the hollow glass microspheres is 5-250 μm; the hollow glass microspheres play a role in charring and preventing thermal conduction, preferably 20-150 μm; if the particle size is too small, the thermal conduction prevention effect becomes poor, and if the particle size is too large, the charring effect becomes poor, and 60-100 μm is further preferred.

[0013] The compatibilizer is commercially available and can effectively improve the compatibility of the polymer and the long glass fiber. It is preferably one or more of polypropylene-maleic anhydride graft (PP-g-MAH), polypropylene-acrylic acid graft (PP-g-MAA), and polypropylene-methacrylic acid graft (PP-g-MAA).

[0014] The antioxidant is commercially available, and is preferably one or more (including two) of tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]pentaerythritol, β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanuric acid, 1,3,5-trimethyl-2,4,6-(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, tris[2,4-di-tert-butylphenyl]phosphite, pentaerythritol dodecathiopropyl ester, dilauryl thiodipropionate, distearyl thiodipropionate, and bis(2,4-di-tert-butylphenol)pentaerythritol diphosphite.

[0015] A method for preparing a low-density, high-strength, halogen-free, flame-retardant, burn-through-resistant long glass fiber reinforced polypropylene composite material comprises the following steps: (1) Polypropylene, a compatibilizer, and an antioxidant are uniformly mixed to obtain a mixed material.

[0016] (2) placing the mixed material in step (1) into the feed port of a twin-screw extruder of a long-fiber device for melt extrusion, mixing the triazine carbonizing agent, ammonium polyphosphate, focused piperazine phosphate, and hollow glass microspheres uniformly, placing them into the side feed port of the twin-screw extruder for melt extrusion, introducing the continuous glass fiber into the impregnation die through the glass fiber rack of the long-fiber device for impregnation coating, and obtaining a low-density, high-strength, halogen-free, flame-retardant, and burn-through-resistant long glass fiber reinforced polypropylene composite material through water cooling, pulling, and pelletizing.

[0017] In step (2), the uniform mixing is carried out in a high-speed mixer at a rotation speed of 500-3000 r / min for 5-10 minutes.

[0018] In step (2), the temperatures of the first to eighth zones of the twin-screw extruder processing temperature are set to 100-120°C, 120-140°C, 160-180°C, 180-200°C, 200-220°C, 200-240°C, 200-250°C, and 210-270°C, respectively, and the impregnation die temperature is 250-310°C; The main engine speed of the twin-screw extruder is 300-400 rpm; The length of the obtained low-density, high-strength, halogen-free, flame-retardant, and burn-through-resistant long glass fiber reinforced polypropylene composite material is 8-14 mm.

[0019] Compared with the prior art, the present invention has the following advantages: Compared with the traditional twin-screw extrusion glass fiber reinforced polypropylene, the present invention adopts the impregnation and coating equipment of continuous long fiber reinforced thermoplastic material. In the obtained continuous long glass fiber reinforced polypropylene composite material particles, the long glass fibers are arranged in parallel along the length direction of the composite material particles, and the length of the glass fibers is the same as the length of the particles, which has better mechanical properties and dimensional stability. The triazine carbonizing agent, ammonium polyphosphate, and focused piperazine phosphate composite flame retardant system can produce synergistic effects and provide excellent flame retardant properties. The addition of hollow glass microspheres is beneficial to the internal low thermal conductivity of the hollow glass microspheres when the material burns, further preventing heat from being transferred inward. The rapid carbonization of the material surface and the inefficient internal heat conduction further improve the material's burn-through time, and further cooperate with the three flame retardants. Due to the effect of the long glass fiber reinforcement system, a stable glass fiber skeleton structure is formed inside the system, ensuring that the material can still maintain a certain mechanical strength during high-temperature combustion, and can ensure that the prepared parts have a stable high-temperature strength retention rate. DETAILED DESCRIPTION

[0020] The present invention is further described below with reference to the embodiments.

[0021] Components Manufacturer and brand Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Polypropylene South Korea LG MH7900 34.6 34.6 34.6 34.6 29.6 26.6 26.6 -- 24.6 Polypropylene CNOOC 640V -- -- -- -- -- -- -- 29.6 -- Long glass fiber Taishan Fiberglass EDR240-T838J 20 20 20 20 20 -- 20 20 -- Long glass fiber Owens Corning SE4805-2400 -- -- -- -- -- 20 -- -- 20 Compatibilizer PP-g-MAH, Shanghai Rizhisheng, 9801 5 5 5 5 5 5 5 5 5 Antioxidants Pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 Antioxidants Tris[2,4-di-tert-butylphenyl]phosphite 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 Flame retardants Triazine carbon former 5 5 5 5 5 8 8 5 10 Flame retardants Ammonium Polyphosphate 10 10 10 10 10 10 10 10 10 Flame retardants Focus on Piperazine Phosphate 20 20 20 20 20 20 20 20 20 Hollow glass microspheres 5 5 5 5 10 10 10 10 10 The particle sizes of the hollow glass microbeads in Examples 1 to 9 in Table 1 are 10 μm, 30 μm, 70 μm, 200 μm, 70 μm, 70 μm, 70 μm, 70 μm, and 70 μm, respectively.

[0022] Components Manufacturer and brand Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Polypropylene South Korea LG MH7900 44.6 39.6 36.6 36.6 39.6 Long glass fiber Taishan Fiberglass EDR240-T838J 20 20 20 20 20 Compatibilizer PP-g-MAH, Shanghai Rizhisheng, 9801 5 5 5 5 5 Antioxidants Pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate 0.2 0.2 0.2 0.2 0.2 Antioxidants Tris[2,4-di-tert-butylphenyl]phosphite 0.2 0.2 0.2 0.2 0.2 Flame retardants Triazine carbon former --- 5 8 5 --- Flame retardants Ammonium Polyphosphate 10 10 10 10 10 Flame retardants Focus on Piperazine Phosphate 20 20 20 20 20 Hollow glass microspheres 70μm -- -- -- 3 5 The low-density, high-strength, halogen-free, flame-retardant, and burn-through-resistant long glass fiber reinforced polypropylene composite materials prepared in Examples 1 to 9 and Comparative Examples 1 to 5 were injection molded, and the mechanical properties, 1.6 mm flame retardant grade, and burn-through resistance time (1500°C flame spray gun directly irradiated the sample surface to test the burn-through time) were measured. The results are shown in Tables 3 and 4 Test items Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 <![CDATA[Density g / cm 3 > 1.24 1.24 1.24 1.24 1.24 1.24 1.24 1.24 1.24 Tensile strength MPa 70.5 71.5 71.5 69.5 72.5 71.6 70.1 72.1 71.7 Bending strength MPa 110 116 116 121 119 117 115 118 115 Flexural modulus MPa 6250 6450 6450 6630 6588 6522 6420 6488 6543 1.6mm flame retardant grade V-0 V-0 V-0 V-0 V-0 V-0 V-0 V-0 V-0 Burn-through time 820 870 920 810 1190 1350 1280 1180 1400 Test items Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 <![CDATA[Density g / cm 3 > 1.24 1.24 1.24 1.24 1.24 Tensile strength MPa 70.1 72.1 71.1 70.2 71.9 Bending strength MPa 112 116 113 110 116 Flexural modulus MPa 6050 6150 6272 6285 6420 1.6mm flame retardant grade V-1 V-0 V-0 V-0 V-0 Burn-through time 360 560 650 800 530 The final low-density, high-strength, halogen-free, flame-retardant, burn-through-resistant long glass fiber reinforced polypropylene composite material has an optimal burn-through resistance time of 1400s and a 1.6mm flame retardant grade of V-0.

Claims

1. A low-density, high-strength, halogen-free, flame-retardant, burn-through-resistant long glass fiber reinforced polypropylene composite material, characterized in that: Contains the following components in parts by weight: Polypropylene 40-80 parts; 10-30 parts of continuous glass fiber; 2-6 parts of compatibilizer; Antioxidant 0.1-2 parts; 3-8 parts of triazine charring agent; 5-18 parts of ammonium polyphosphate; Focus on piperazine phosphate 10-35 parts; 3-15 parts of hollow glass microspheres.

2. The low-density, high-strength, halogen-free, flame-retardant, burn-through-resistant long glass fiber reinforced polypropylene composite material according to claim 1, characterized in that: The hollow glass microspheres have a particle size of 20-150 μm.

3. The low-density, high-strength, halogen-free, flame-retardant, burn-through-resistant long glass fiber reinforced polypropylene composite material according to claim 1, characterized in that: The following steps are involved: (1) mixing polypropylene, a compatibilizer, and an antioxidant uniformly to obtain a mixed material; (2) placing the mixed material in step (1) into the feed port of a twin-screw extruder of a long-fiber device for melt extrusion, mixing the triazine carbonizing agent, ammonium polyphosphate, focused piperazine phosphate, and hollow glass microspheres uniformly, placing them into the side feed port of the twin-screw extruder for melt extrusion, introducing the continuous glass fiber into the impregnation die through the glass fiber rack of the long-fiber device for impregnation coating, and obtaining a low-density, high-strength, halogen-free, flame-retardant, and burn-through-resistant long glass fiber reinforced polypropylene composite material through water cooling, pulling, and pelletizing.

4. The method for preparing the low-density, high-strength, halogen-free, flame-retardant, burn-through-resistant long glass fiber reinforced polypropylene composite material according to claim 3, characterized in that In step (2), the uniform mixing is carried out in a high-speed mixer at a rotation speed of 500-3000 r / min for 5-10 minutes.

5. The method for preparing the low-density, high-strength, halogen-free, flame-retardant, burn-through-resistant long glass fiber reinforced polypropylene composite material according to claim 3, characterized in that: In step (2), the temperatures of the first to eighth zones of the twin-screw extruder processing temperature are set to 100-120°C, 120-140°C, 160-180°C, 180-200°C, 200-220°C, 200-240°C, 200-250°C, and 210-270°C, respectively, and the impregnation die temperature is 250-310°C; The main engine speed of the twin-screw extruder is 300-400 rpm; The length of the obtained low-density, high-strength, halogen-free, flame-retardant, and burn-through-resistant long glass fiber reinforced polypropylene composite material is 8-14 mm.