A long-glass-fiber-reinforced flame-retardant ceramicized polypropylene material and a preparation method thereof

Abstract

The application provides a long glass fiber reinforced flame-retardant ceramization polypropylene material and a preparation method thereof. The material comprises the following components in parts by weight: polypropylene 0-20 parts, flame-retardant long glass fiber master batch 30-60 parts, and ceramization master batch 40-70 parts. The application selects a multi-gradient melting point glass powder, a phosphorus flame retardant, four acicular zinc oxide whiskers, and a combination of long glass fibers and ceramic fillers, so that the carbon layer structure is dense and has high structural strength during combustion, and is not damaged under the pressure of the flame; the interlayer structure blocks the heat conduction path, significantly reduces the back surface temperature, and keeps the material from softening and collapsing. The material has the remarkable effects of ablation resistance, good processing, high strength, good flame retardancy, low cost, and light weight.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer materials, in particular to a long glass fiber reinforced flame-retardant ceramicized polypropylene material with high strength and ablation resistance and a preparation method thereof. BACKGROUND

[0002] Ablation-resistant polymer materials, as a new type of efficient fireproof material, gradually enter the field of vision. When exposed to open flame, the surface layer of the composite material can be converted into an ablation-resistant body with self-supporting properties, preventing the spread of fire to the interior of the material, thereby achieving efficient flame retardation.

[0003] The existing technology of ablation-resistant materials mainly focuses on using thermosetting plastics as the matrix or additives, which have excellent ablation resistance, high softening point, and excellent combustion performance, but the materials are difficult to recycle. Among thermoplastic plastics, PPS and PPO currently have good ablation resistance, but they have high cost and insufficient production capacity, making it difficult to be widely applied. Polypropylene is a very practical general-purpose resin with small density and high yield, and the application research of ceramicized polypropylene with ablation resistance is increasingly valuable in economy and society.

[0004] As a material for battery pack covers, it needs to have good large part forming property, excellent mechanical strength, dimensional stability, flame retardation, and ablation resistance. Its ablation resistance includes the ability to resist open flame, temperature (500-1200℃), and pressure (atmospheric pressure and particle impact). To resist open flame, the material needs to have a flame retardant rating of V0 or above. To resist temperature and pressure, the material needs to withstand 1000-1200℃ burning for more than 10 minutes without burning through.

[0005] On the one hand, the material needs sufficient carbon layer strength to resist the direct impact of flame pressure and particles. On the other hand, in many cases, the polypropylene material deforms and collapses, causing the ablation point of the flame to expand, the area of the material under stress to expand, and the material to be pulled and burned through due to insufficient self-supporting. Therefore, the temperature on the back should be as low as possible to maintain the structure of the material.

[0006] Patent CN115322477B discloses a lightweight ablation-resistant polypropylene material and a preparation method thereof, which uses a ceramic filler master batch to effectively reduce the volume fraction of inorganic powder filler. However, the volume fraction of low-melting hollow flux is larger, affecting the processability, and the processing process is prone to breakage, which cannot achieve the expected effect.

[0007] The inorganic flame retardant used in patent CN115322477B, the foaming agent used in patent CN112745549B, and the inorganic magnesium compound used in patent CN112745571B will release a large amount of water vapor and carbon dioxide, making the carbon layer fluffy and low in strength.

[0008] Patent CN112745573B adopts an alloy scheme of polypropylene resin and polyamide resin, and the core layer provides excellent mechanical properties for the alloy material due to the intermolecular hydrogen bonding of the PA phase. However, the use of phosphorus-nitrogen flame retardants causes uncontrollable pore number and pore size of the carbon layer, affecting the strength of the carbon layer.

[0009] Patent CN103865154B discloses a drip-proof ceramicized polyolefin composite material and a preparation method thereof. EVA, high and low softening point glass powder, organic montmorillonite, silane coupling agent, MAH-g-PP are obtained in a two-roll open mill to obtain a sheet, and the surface energy is rapidly converted into a dense ceramicized residue at high temperature. However, no flame retardant is added, and the material is drip-proof only by relying on the dispersion of the filler in the matrix and the fireproof performance after ceramicization, and the flame retardant performance is unstable.

[0010] In addition, some researches focus on boron nitride, silicon nitride whisker and other filler schemes, but the price is expensive and difficult to be applied on a large scale. SUMMARY

[0011] To solve the above problems, the present application provides a long glass fiber reinforced flame-retardant ceramicized polypropylene material, which can have high ablation resistance without affecting the processing performance, and maintain excellent mechanical strength, flame retardant performance and low cost.

[0012] To achieve the above purpose, the present application adopts the following technical scheme:

[0013] A long glass fiber reinforced flame-retardant ceramicized polypropylene material and a preparation method thereof, characterized in that it comprises the following components by weight:

[0014] Polypropylene 0-20 parts

[0015] Flame-retardant long glass fiber masterbatch 30-60 parts

[0016] Ceramicized masterbatch 40-70 parts

[0017] The flame-retardant long glass fiber masterbatch comprises the following components by weight: polypropylene 20-40 parts, long glass fiber 50-60 parts, phosphorus-based flame retardant 10-15 parts, and other additives 1-5 parts. The polypropylene is homopolymer polypropylene; the phosphorus-based flame retardant is at least one of red phosphorus, BDP, RDP, TPP and ADP; and the other additives include a compatibilizer, a dispersant, an antioxidant, a lubricant, a color powder and the like.

[0018] The ceramicized master batch comprises the following components in parts by weight: polypropylene 30 parts, ceramic filler 25-55 parts, four-needle zinc oxide whisker 2-6 parts, glass powder 15-30 parts, and other additives 1-5 parts. The ceramic filler is one or more of kaolin, talcum powder, mica, and wollastonite; the glass powder is a multi-gradient melting point glass powder compounded from glass powder A, glass powder B, and glass powder C; wherein the softening point of glass powder A is 350-400 DEG C, the softening point of glass powder B is 500-600 DEG C, and the softening point of glass powder C is 700-800 DEG C; the ratio of glass powder A:glass powder B:glass powder C is 1:(0.1-0.5):(0.8-2); and the other additives include a compatibilizer, a dispersant, an antioxidant, a lubricant, and color powder.

[0019] The long-glass-fiber-reinforced flame-retardant ceramicized polypropylene material is prepared by the following method:

[0020] (1) polypropylene resin, flame retardant, and other additives are weighed, mixed uniformly in a high-speed machine, and then fed into an impregnation tank through a double-screw extruder, the temperature of the impregnation tank is set to 240-280 DEG C, and the long glass fiber is pulled, cooled, cut, and dried after passing through the impregnation tank to obtain a flame-retardant long-glass-fiber master batch according to the weight ratio;

[0021] (2) polypropylene resin, ceramic filler, four-needle zinc oxide whisker, glass powder, and other additives are weighed, mixed in a high-speed machine, and then fed into a double-screw extruder for granulation, the temperature is 200-240 DEG C, and the rotation speed is 480 rpm, and the ceramicized master batch is obtained after cooling, cutting, and drying;

[0022] (3) polypropylene resin, flame-retardant long-glass-fiber master batch, and ceramicized master batch are weighed, mixed uniformly in a high-speed machine, and the long-glass-fiber-reinforced flame-retardant ceramicized polypropylene material is obtained.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] 1. The present application has the remarkable effects of ablation resistance (not burned through at 1200 DEG C / 10 min, no collapse), good processing, high strength (specific strength > 50), good flame retardance (V0), low cost, and lightweight by selecting a multi-gradient melting point glass powder, a phosphorus-based flame retardant, a four-needle zinc oxide whisker, and a combination of long glass fiber and ceramic filler.

[0025] 2. The three groups of low-melting-point glass powders, after being regulated and proportioned, facilitate the transformation of solid glass powder into a liquid phase layer under different temperature gradients. This results in excellent flow and diffusion capabilities, allowing the glass powder to bond with ceramic fillers and undergo a eutectic reaction to form a "sandwich" structure of ceramic-like carbon layers. The process of constructing this multi-layered structure fills gaps and compensates for defects, resulting in high-strength carbon layers that resist flame pressure without breaking. The interlayer structure blocks heat conduction pathways, exponentially reducing the heat transfer rate, significantly lowering the back-side temperature, preventing material softening, and ensuring the structure does not collapse.

[0026] 3. After screening and proportion control, the four needle-shaped zinc oxide whiskers, due to their unique nano-tip effect and large specific surface area, can be fully enriched around the periphery of the ceramic filler lamellar structure during sintering, and connect with the capillary of the glass molten liquid phase layer. As a bridge, they bond with the ceramic filler and long glass fibers to form a self-supporting structure, forming a eutectic mixture at high temperature, and forming a stable and reliable ceramic-like layer.

[0027] 4. The flame-retardant long glass fiber masterbatch uses phosphorus-based flame retardants, which are added in small amounts, have low density, and high strength. The phosphorus-based flame retardant mechanism terminates free radical chain reactions and promotes carbonization. It does not produce gas and can maintain a dense carbon layer structure with high structural strength.

[0028] 5. Long glass fiber reinforced polypropylene has higher initial properties and a longer glass fiber retention length, which is more conducive to the interlacing of the XYZ three-dimensional directions of the ceramic-like carbon layer "sandwich" structure, forming a stable self-supporting structure.

[0029] 6. The method involves first preparing flame-retardant long glass fiber masterbatch and ceramicized masterbatch, and then mixing them externally. On the one hand, this avoids excessive shearing and collision of multiple components with different properties in the extruder, resulting in minimal performance loss. On the other hand, it allows for flexible selection of different glass fiber contents, such as G15 to G36, for use after mixing, based on the actual part's formability and strength requirements. This provides design freedom and convenient downstream application. Detailed Implementation

[0030] To make the technical solution of this invention clearer and more explicit, the invention will be further described below. Any solution derived by equivalent substitution and conventional reasoning of the technical features of this invention falls within the protection scope of this invention. All materials used in this invention are commercially available.

[0031] The materials used in this invention are as follows:

[0032] Polypropylene: Homopolymer polypropylene resin, melt index 90 g / 10 min, tensile strength 45 MPa

[0033] Long glass fiber: TCR738, linear density 2400 tex

[0034] Short glass fiber: T5380D, diameter 13μm, length 4.5mm

[0035] Glass powder A: softening point 380°C

[0036] Glass powder B: softening point 550°C

[0037] Glass powder C: softening point 780°C

[0038] Four-needle zinc oxide whisker: diameter 1 μm, length 50 μm

[0039] Phosphorus flame retardant: microcapsule coated red phosphorus

[0040] Nitrogen-phosphorus flame retardant: ammonium polyphosphate APP

[0041] Kaolin: 1000 mesh

[0042] Compatibilizer: maleic anhydride grafted polypropylene, grafting rate 1.5%

[0043] Antioxidant: 1010 and 168 compounded

[0044] Dispersant: dendritic polymer

[0045] Lubricant: ultra-high molecular weight silicone masterbatch

[0046] Example 1

[0047] Take 32 parts of polypropylene resin, 14 parts of red phosphorus flame retardant, 3 parts of compatibilizer, 0.5 parts of dispersant, and 0.5 parts of antioxidant, mix them uniformly in a high-speed machine, then pass them through a twin-screw extruder into an impregnation tank, set the temperature of the impregnation tank to 260°C, pass 50 parts of long glass fiber according to the weight ratio through the impregnation tank, then perform drawing, cooling, pelletizing, and drying to obtain flame-retardant long glass fiber masterbatch;

[0048] Take 30 parts of polypropylene resin, 40 parts of kaolin, 10 parts of glass powder A, 4 parts of glass powder B, 10 parts of glass powder C, 3 parts of four-needle zinc oxide whisker, 2 parts of compatibilizer, 0.7 parts of dispersant, and 0.3 parts of antioxidant, mix them in a high-speed machine, then pass them through a twin-screw extruder for pelletizing, the temperature is 220°C, the rotation speed is 480 rpm, and after cooling, pelletizing, and drying, obtain ceramic masterbatch;

[0049] Take 40 parts of flame-retardant long glass fiber masterbatch and 60 parts of ceramic masterbatch, mix them uniformly in a high-speed machine to obtain long glass fiber reinforced flame-retardant ceramic polypropylene material.

[0050] Example 2

[0051] Take polypropylene resin 26 parts, red phosphorus flame retardant 10 parts, compatibilizer 3 parts, dispersant 0.5 parts, antioxidant 0.5 parts, mix evenly in high speed machine, then pass through double screw extruder into the immersion tank, the immersion tank is set to 260℃, according to the weight ratio of 60 parts of long glass fiber after immersion tank for drawing, cooling, cutting, drying to obtain flame retardant long glass fiber masterbatch;

[0052] Take polypropylene resin 30 parts, kaolin 40 parts, 10 parts of glass powder A, 4 parts of glass powder B, 10 parts of glass powder C, four needle zinc oxide whisker 3 parts, compatibilizer 2 parts, dispersant 0.7 parts, antioxidant 0.3 parts, mix in high speed machine, then pass through double screw extruder to granulation, temperature is 220℃, speed is 480rpm, cooling, cutting, drying to obtain ceramic masterbatch;

[0053] Take polypropylene 10 parts, flame retardant long glass fiber masterbatch 50 parts, ceramic masterbatch 40 parts, mix evenly in high speed machine, get long glass fiber reinforced flame retardant ceramic polypropylene material.

[0054] Example 3

[0055] The difference with example 1 is that the ceramic masterbatch: polypropylene resin 30 parts, talc 35 parts, 11 parts of glass powder A, 4 parts of glass powder B, 15 parts of glass powder C, four needle zinc oxide whisker 2 parts, compatibilizer 2 parts, dispersant 0.7 parts, antioxidant 0.3 parts.

[0056] Example 4

[0057] The difference with example 1 is that the ceramic masterbatch: polypropylene resin 30 parts, kaolin 46 parts, 6 parts of glass powder A, 2 parts of glass powder B, 8 parts of glass powder C, four needle zinc oxide whisker 5 parts, compatibilizer 2 parts, dispersant 0.7 parts, antioxidant 0.3 parts.

[0058] Example 5

[0059] The difference with example 1 is that take polypropylene 15 parts, flame retardant long glass fiber masterbatch 30 parts, ceramic masterbatch 55 parts, mix evenly in high speed machine, get long glass fiber reinforced flame retardant ceramic polypropylene material.

[0060] Example 6

[0061] The difference with example 2 is that take flame retardant long glass fiber masterbatch 60 parts, ceramic masterbatch 40 parts, mix evenly in high speed machine, get long glass fiber reinforced flame retardant ceramic polypropylene material.

[0062] Comparative example 1

[0063] The difference with example 1 is that there is no glass powder, the content of kaolin increases accordingly.

[0064] Comparative Example 2

[0065] The difference from Example 1 is that there is no four-needle-shaped zinc oxide whisker, and the content of kaolin is correspondingly increased.

[0066] Comparative Example 3

[0067] The difference from Example 1 is that the red phosphorus flame retardant is replaced by a nitrogen-phosphorus flame retardant.

[0068] Comparative Example 4

[0069] The difference from Example 1 is that long glass fibers are replaced by short glass fibers. There is no impregnation tank process, and Cai Yun-gong twin-screw extruder is used for granulation.

[0070] Comparative Example 5

[0071] The difference from Example 1 is that 50 parts of polypropylene, 20 parts of flame-retardant long glass fiber masterbatch, and 30 parts of ceramic masterbatch are weighed, and then stirred and mixed uniformly in a high-speed machine to obtain a long glass fiber reinforced flame-retardant ceramic polypropylene material.

[0072] Comparative Example 6

[0073] The difference from Example 4 is that 53 parts of kaolin, 4 parts of glass powder A, 2 parts of glass powder B, and 4 parts of glass powder C are used.

[0074] Comparative Example 7

[0075] The difference from Example 1 is that 28 parts of kaolin, 12 parts of glass powder A, 12 parts of glass powder B, and 12 parts of glass powder C are used.

[0076] Comparative Example 8

[0077] The difference from Example 1 is that 12 parts of glass powder A and 12 parts of glass powder C are used, and no glass powder B is used.

[0078] Comparative Example 9

[0079] The difference from Example 1 is that 42 parts of kaolin, 5 parts of glass powder A, 12 parts of glass powder B, and 5 parts of glass powder C are used.

[0080] Comparative Example 10

[0081] The difference from Example 2 is that 70 parts of flame-retardant long glass fiber masterbatch and 30 parts of ceramic masterbatch are weighed, and then stirred and mixed uniformly in a high-speed machine to obtain a long glass fiber reinforced flame-retardant ceramic polypropylene material.

[0082] Product performance test method:

[0083] The particles obtained in the examples and comparative examples are injection molded into samples at a temperature of 230-260°C, with the mold temperature controlled at about 60°C. The relevant performance tests are carried out according to the following test methods.

[0084] (1) Density: according to ISO 1183-1 method, sample size 20*10*4mm;

[0085] (2) Tensile strength: according to ISO 527 method, sample size 170*10*4mm, test speed 5mm / min;

[0086] (3) Specific strength: the ratio of tensile strength / density;

[0087] (4) Flame retardant grade: sample size 125*13*1.6mm, tested according to UL-94 standard;

[0088] (5) Backfire surface temperature: using butane high-speed flame spray gun, pressure 0.5MPa, outer flame temperature 1200℃, flame spraying on the center of the vertically placed 150mm*100mm*2mm plate sample for 10min, the backfire surface temperature is measured in real time online by a φ30mm patch thermocouple sensor, when the temperature is >1000℃, the test is stopped, unit: ℃;

[0089] Table 1 performance test results of each example

[0090]

[0091]

[0092] Table 2 performance test results of each comparative example

[0093]

[0094] From the performance test results of examples 1-6 in Table 1 and comparative examples 1-9 in Table 2, it can be clearly seen that the ablation resistance effect of the present application is remarkable, 1200℃ / 10min is not burned through, does not collapse, the initial performance is high, the specific strength is >50. In comparative example 1, no glass powder is added, in comparative example 2, no four acicular zinc oxide whiskers are added, it is difficult to quickly build a ceramic layer, and it is burned through after 2min of burning, and it collapses. In comparative example 3, the nitrogen-phosphorus flame retardant produces irregular pores, in comparative example 4, the short glass fiber, in comparative example 10, the master batch ratio is not properly matched, although it can withstand burning for 2min, but with the extension of time, the heat and pressure of the flame break through the carbon layer, leading to burning through. Comparative example 5 is entirely on fire. Comparative examples 6-9 cannot meet the burning through and collapse after the flame severity is upgraded.

Claims

1. A long-glass-fiber-reinforced flame-retardant ceramified polypropylene material, characterized in that The composition comprises the following components by weight: Polypropylene 0-20 parts; Flame-retardant long glass fiber masterbatch 30-60 parts; Ceramization masterbatch 40-70 parts; The flame-retardant long glass fiber masterbatch comprises the following components by weight: polypropylene 20-40 parts, long glass fiber 50-60 parts, phosphorus-based flame retardant 10-15 parts, and other additives 1-5 parts; The ceramization masterbatch comprises the following components by weight: polypropylene 30 parts, ceramic filler 25-55 parts, four-needle zinc oxide whisker 2-6 parts, glass powder 15-30 parts, and other additives 1-5 parts; wherein the glass powder is a multi-gradient melting point glass powder, which is compounded by glass powder A, glass powder B, and glass powder C; wherein the softening point of the glass powder A is 350-400℃, the softening point of the glass powder B is 500-600℃, and the softening point of the glass powder C is 700-800℃; the ratio of the glass powder A:glass powder B:glass powder C is 1:(0.1-0.5):(0.8-2).

2. The long glass fiber reinforced flame retardant ceramified polypropylene material according to claim 1, characterized in that: The polypropylene in the flame-retardant long glass fiber masterbatch is homopolymer polypropylene.

3. The long glass fiber reinforced flame retardant ceramified polypropylene material according to claim 1, characterized in that: The phosphorus-based flame retardant is at least one of red phosphorus, BDP, RDP, TPP, and ADP.

4. The long glass fiber reinforced flame retardant ceramified polypropylene material according to claim 1, characterized in that: The ceramic filler is one or more of kaolin, talcum powder, mica, and wollastonite.

5. The long glass fiber reinforced flame retardant ceramified polypropylene material according to claim 1, characterized in that: The other additives in the flame-retardant long glass fiber masterbatch and the ceramization masterbatch include one or more of a compatibilizer, a dispersant, an antioxidant, a lubricant, and a color powder.

6. The process for the preparation of long glass fiber reinforced flame retardant ceramified polypropylene material according to any one of claims 1 to 5, characterized in that, The steps are as follows: (1) Weigh the polypropylene resin, the phosphorus-based flame retardant, and other additives, mix them uniformly in a high-speed machine, then pass them through a double-screw extruder into an impregnation tank, set the temperature of the impregnation tank to 240-280℃, and pass the long glass fiber according to the weight ratio through the impregnation tank, then perform drawing, cooling, granulation, and drying to obtain the flame-retardant long glass fiber masterbatch; (2) Weigh the polypropylene, the ceramic filler, the four-needle zinc oxide whisker, the glass powder, and other additives, mix them in a high-speed machine, then pass them through a double-screw extruder for granulation, the temperature is 200-240℃, and the rotation speed is 480 rpm, then perform cooling, granulation, and drying to obtain the ceramization masterbatch; (3) Weigh the polypropylene, the flame-retardant long glass fiber masterbatch, and the ceramization masterbatch, mix them uniformly in a high-speed machine to obtain the long glass fiber reinforced flame-retardant ceramization polypropylene material.

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