Continuous fiber reinforced polypropylene ablation-resistant prepreg tape material and preparation method thereof

Abstract

The invention discloses a continuous fiber reinforced polypropylene ablation-resistant prepreg tape material which can be used in the field of medium and high temperature protection, and the continuous fiber reinforced polypropylene ablation-resistant prepreg tape material comprises the following raw materials in parts by weight: 100-300 parts of polypropylene, 200-500 parts of continuous fiber, 50-90 parts of inorganic filler, 30-50 parts of titanium aluminum carbide, 5-25 parts of compatilizer, 1-10 parts of antioxidant and 0.5-5 parts of lubricant. The inorganic filler is at least one of calcined kaolin, wollastonite, expanded vermiculite and diatomite. Through systematic processes of pre-dispersion-dynamic yarn spreading, forced melting-stable conveying and preheating-delayed dipping and a titanium aluminum carbide high-temperature compact protection layer, the core problem that continuous fibers are difficult to dip in a high-filling polypropylene system is successfully solved; the prepared prepreg tape material has excellent ablation resistance, mechanical properties and processability, is low in cost, and is suitable for thermal protection occasions sensitive to cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of polypropylene thermoplastic composites, in particular to a continuous fiber reinforced polypropylene ablative resistant prepreg tape material and a preparation method thereof. BACKGROUND

[0002] Ablation resistant materials are widely used in aerospace, military, new energy vehicles, fire fighting and high temperature industrial equipment fields. Traditional ablative resistant materials such as phenolic resin-based composites have problems such as high brittleness, toxic in processing and difficult to recycle. Polypropylene, as a general-purpose plastic with low price, good processing performance and excellent chemical resistance, is a potential advantage as an ablative resistant matrix. However, polypropylene itself has a low limiting oxygen index and is prone to decomposition and flow at high temperatures, and its ablative resistance is very poor.

[0003] Introducing continuous fibers and a large amount of inorganic fillers into the polypropylene matrix is an effective way to improve its ablative resistance. However, this brings new technical challenges: 1) the melt viscosity increases sharply under high filler content, making it extremely difficult to impregnate the fibers; 2) polypropylene has poor interfacial compatibility with non-polar fibers and inorganic fillers, affecting the final performance. In the prior art, there are few reports on the successful preparation of high-performance continuous fiber reinforced polypropylene-based ablative resistant composites. SUMMARY

[0004] The present application aims to overcome the shortcomings of the prior art and provide a continuous fiber reinforced polypropylene ablative resistant prepreg tape material and a preparation method thereof. The material significantly improves the ablative resistance and mechanical strength while maintaining the cost advantage of polypropylene.

[0005] To achieve the above-mentioned purpose, the present application realizes the following technical solutions: Formulation design: high flow PP is used to ensure the processability of high filler systems; high grafting rate PP-g-MAH is used as a compatibilizer to strongly bridge PP with fibers and fillers; kaolin, wollastonite, expanded vermiculite and diatomite are optimally selected as composite fillers to form a dense and strong carbon silicate protective layer during combustion; titanium aluminum carbide is also introduced to form a dense protective layer of α-Al2O3 and TiO2 at high temperatures, filling the gaps in the carbon silicate protective layer and blocking the oxidation reaction.

[0006] Process optimization: water and low molecular weight substances in the system are removed by vacuum extraction with a twin screw, reducing air pores; the processing temperature is precisely controlled to be low to prevent PP degradation; the preheating and impregnation temperatures are optimized to ensure that the melt is fully impregnated with fibers within the viscosity window.

[0007] A continuous fiber reinforced polypropylene ablative resistant prepreg tape material, by weight, the raw material composition includes: Polypropylene 100-300 parts; Continuous fiber 200-500 parts; Inorganic filler 50-90 parts; Titanium aluminum carbide 10-30 parts; Compatibility agent 5-25 parts; Antioxidant 1-10 parts; Lubricant 0.5-1 parts.

[0008] As preferred, the polypropylene is high flow polypropylene, which has a melt index of 30-150 g / 10 min at 230°C under a load of 2.16 kg.

[0009] The continuous fiber is at least one of continuous glass fiber, basalt fiber, and the fiber linear density is 600-2400 Tex.

[0010] The compatibility agent is high flow polypropylene-maleic anhydride graft (PP-g-MAH), which has a maleic anhydride grafting grafting rate of not less than 0.8%, and a melt index of >5 g / 10 min.

[0011] The antioxidant is one or more of hindered phenol, phosphite, or sulfide antioxidant, and is preferably one or more of antioxidant 1010, antioxidant 412s, antioxidant 168, and antioxidant 1076.

[0012] The inorganic filler is at least one or more of calcined kaolin, wollastonite, expanded vermiculite, and diatomite, the kaolin has a particle size of 1-10 μm, and the wollastonite has an aspect ratio of greater than 10:1.

[0013] The lubricant is at least one of calcium stearate and ethylene bis-stearamide.

[0014] The application also provides a preparation method of the continuous fiber reinforced polypropylene ablative resistant pre-impregnated tape material, which adopts a melt impregnation process and includes the following steps: (1) Pretreatment of titanium aluminum carbide: titanium aluminum carbide powder is added into 1-3 wt% dilute hydrochloric acid solution at a ratio of 5-10 g / 100 mL, and ultrasonic treatment is performed for 30-60 minutes, after reaction, centrifugal cleaning is performed with deionized water (rotation speed of 8000-10000 rpm, 5 minutes each time), until the pH value of the supernatant is neutral (about 5-7 times), and finally, drying is performed in an oven at 80-100°C for 6-12 hours.

[0015] (2) Coupling agent coating of titanium aluminum carbide: silane coupling agent is weighed at 1.0-2.5% of the mass of titanium aluminum carbide powder, dissolved in anhydrous ethanol (coupling agent: ethanol volume ratio is about 1:9). Stir and add a small amount of deionized water (1-2% of the volume of the coupling agent), hydrolyze at room temperature for 15-30 minutes to form a clear solution.

[0016] The titanium aluminum carbide powder obtained in step (1) is added to the hydrolysis solution obtained in step (2) above, and the solid-liquid ratio is kept at 1 g:10-15 mL. The reaction is carried out in a constant temperature water bath at 70-80°C with a mechanical stirring rate of 300-500 rpm for 2-4 hours. Finally, the residual solvent is removed to obtain a dry and usable modified powder.

[0017] (3) Raw material premixing: The titanium aluminum carbide powder prepared in step (2) is mixed with polypropylene, inorganic filler, compatibilizer, antioxidant, lubricant at a high speed for 5-10 minutes at 60-80°C to obtain a pre-dispersed resin mixture, which is then put into the main bin of the loss-in-weight weighing scale; (4) Forced melting, dispersion and devolatilization: The mixture of step (3) is melted and mixed in a co-rotating parallel twin screw extruder at 170-230°C, and the vacuum degree is not less than -0.07 MPa by opening the vacuum exhaust in the middle section of the screw; (5) Melt conveying and pressure stabilization: The melt treated in step (4) is conveyed stably to the impregnation die through a gear melt pump; (6) Preheating and dynamic spreading of fibers: After tension adjustment, the continuous fibers are preheated through an oven, and then non-contact dynamic spreading is carried out through a hot air knife box; (7) High pressure, delayed impregnation: The spreaded fibers and the melt of step (5) converge in the impregnation die, which is provided with multiple impregnation rollers, and the fibers and the melt travel along a zigzag path; (8) Cooling, shaping and winding: The impregnated composite material is cooled, shaped, pulled and wound to obtain the continuous fiber reinforced polypropylene ablative resistant pre-impregnated tape material and the preparation method thereof In step (5), the twin screw extruder is a high torque co-rotating twin screw extruder, the length-diameter ratio of the screw is (40-52):1, the temperature of each zone of the twin screw extruder is set to 170-230°C, the main machine speed of the twin screw extruder is 200-500 r / min, and the specific torque is >11 Nm / cm3; The heating temperature of the film coating head is 180-250°C; The heating temperature of the impregnation die is 200-260°C.

[0018] The structure of the impregnation die: multiple (usually 4-6) impregnation rollers are arranged in the die. The fibers and the melt pass through these rollers in the die to form a zigzag "S" shaped path.

[0019] The preheating device is a ceramic heating device, and the heating temperature is 120-220°C.

[0020] The yarn spreading device is a non-contact dynamic yarn spreading device: the fiber tows are made more dispersed under the action of air flow after passing through the up-and-down staggered air knives, so that better yarn spreading effect is obtained; the air knife air pressure is 0.15-0.30 MPa, and the hot air temperature is 80-200 DEG C.

[0021] Compared with the prior art, the main advantages of the present application include: High-end ablation-resistant composite materials usually use polyether ether ketone (PEEK), polyimide (PI) or phenolic resin as the matrix, these resin raw materials are expensive, and the processing conditions are harsh (extremely high processing temperature is required), resulting in high production cost, which limits its application in large-scale or cost-sensitive fields. The present application successfully improves the low-cost material polypropylene to a level that can meet the requirements of high-temperature ablation protection by a unique formula and process design, realizes "plastic instead of expensive", and provides customers with a cost-effective solution.

[0022] The present application successfully solves the problem of rapid rise of melt viscosity, poor flowability, difficulty in effectively infiltrating dense continuous fiber tows, and easy production of defects such as "dry yarn" and "white yarn" in the PP system with high filling inorganic filler, which leads to a large decrease in the mechanical properties and ablation resistance of the composite material.

[0023] "Pre-dispersion-dynamic yarn spreading" technology: non-contact yarn spreading by hot air knife, fully spreading the fiber tows under the premise of avoiding fiber damage, increasing the specific surface area that can be contacted by the melt.

[0024] "Force melting-stable conveying" technology: high-torque double screws with special screw configuration are used to realize strong shearing and dispersion of high fillers, and a melt pump is used to provide stable and high-pressure melt flow to provide continuous power for forced impregnation.

[0025] "Preheating-delayed impregnation" technology: preheating of the fibers to prevent the front of the melt from cooling; and the impregnation path is prolonged by the multi-roller design in the impregnation mold, increasing the contact time of the fibers and the melt under high temperature and high pressure; and every time the fiber tows pass through the impregnation rollers, the bending deformation of the fiber tows will produce a small "pumping" effect inside the fiber tows, and the melt pressure changes sharply at the roller gap, forming a strong pressure difference, like using multiple "small rollers" to repeatedly and strongly "squeeze" and "pump" the melt into every gap in the fiber tows. This combined process ensures that the resin can fully and uniformly impregnate the fibers even under high filling conditions, which is the most core technical breakthrough of the present application.

[0026] The present application forms a dense protective layer of α-Al2O3 and TiO2 at high temperature after pretreatment of titanium aluminum carbide, fills the gaps of the carbon silicate protective layer, blocks the oxidation reaction, and further improves the ablation resistance of the material; meanwhile, the addition of titanium aluminum carbide can reduce the amount of inorganic fillers added, and improve the mechanical properties of the material. DETAILED DESCRIPTION

[0027] Examples 1-3, Comparative Examples 1-4, the component ratio and the shaping process of each example and comparative example are shown in Table 1.

[0028] Table 1 Component ratio of each example and comparative example Components Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Polypropylene 200 220 240 305 215 170 200 Continuous glass fiber 400 400 400 400 400 400 400 Calcined kaolin 90 70 50 0 90 120 90 Titanium aluminum carbide 15 15 15 0 0 15 15 Compatibilizer 20 20 20 20 20 20 20 Antioxidant 5 5 5 5 5 5 5 Lubricant 2 2 2 2 2 2 2

[0029] Example 1 The 200 parts of polypropylene have a melt index of 100 g / 10 min; The 400 parts of continuous glass fibers are continuous untwisted roving E glass treated by a coupling agent with a linear density of 1200 tex; The 90 parts of calcined kaolin have a particle size of 5 μm; The 20 parts of titanium aluminum carbide are titanium aluminum carbide powder treated by dilute hydrochloric acid and a silane coupling agent; The 15 parts of the compatibilizer are high-flow polypropylene-maleic anhydride grafts; The antioxidant is 3 parts of antioxidant 1010 and 2 parts of antioxidant 168; The 2 parts of lubricant are ethylene bis-stearamide; According to the published preparation method and processing technology, the continuous fiber reinforced high polypropylene ablation-resistant prepreg tape with a thickness of 0.25±0.02 mm and a width of 800±10 mm is prepared. The prepared prepreg tape is tested, and the test results are shown in Table 2. Example 2

[0030] The 220 parts of polypropylene have a melt index of 100 g / 10 min; The 400 parts of continuous glass fibers are continuous untwisted roving E glass treated by a coupling agent with a linear density of 1200 tex; The 70 parts of calcined kaolin have a particle size of 5 μm; The 15 parts of titanium aluminum carbide are titanium aluminum carbide powder treated by dilute hydrochloric acid and a silane coupling agent; The 20 parts of the compatibilizer are high-flow polypropylene-maleic anhydride grafts; The antioxidant is 3 parts of antioxidant 1010 and 2 parts of antioxidant 168; The 2 parts of lubricant are ethylene bis-stearamide; The continuous fiber reinforced high polypropylene ablation resistant prepreg tape prepared according to the disclosed preparation method and processing technology has a thickness of 0.25±0.02 mm and a width of 800±10 mm. The prepared prepreg tape is tested, and the test results are shown in Table 2. Example 3

[0031] The 240 parts of polypropylene have a melt index of 100 g / 10 min; The 400 parts of continuous glass fibers are continuous untwisted roving E glass treated by a coupling agent and have a linear density of 1200 tex; The 50 parts of calcined kaolin have a particle size of 5 μm; The 15 parts of titanium aluminum carbide are titanium aluminum carbide powder treated by dilute hydrochloric acid and a silane coupling agent; The 20 parts of the compatibilizer are high flow polypropylene-maleic anhydride grafts; The antioxidants are 3 parts of antioxidant 1010 and 2 parts of antioxidant 168; The 2 parts of lubricant are ethylene bis-stearamide; The continuous fiber reinforced high polypropylene ablation resistant prepreg tape prepared according to the disclosed preparation method and processing technology has a thickness of 0.25±0.02 mm and a width of 800±10 mm. The prepared prepreg tape is tested, and the test results are shown in Table 2.

[0032] Comparative Example 1 No inorganic fillers are contained.

[0033] Comparative Example 2 No titanium aluminum carbide is contained.

[0034] Comparative Example 3 The total amount of inorganic fillers exceeds (120 parts of kaolin).

[0035] Comparative Example 4 Unpretreated titanium aluminum carbide is added.

[0036] The test results are shown in Table 2.

[0037] Table 2: Comparison of mechanical properties of each example and comparative example Test item Tensile strength Flexural strength Surface quality Ablation rate Interlaminar shear strength Unit MPa MPa / (mm / s) MPa Test standard ISO 527-4 ISO 14125 Visual GJB 323A-96 ASTM D2344 Example 1 630 496 Good 0.096 23.5 Example 2 680 515 Good 0.112 24.1 Example 3 730 525 Good 0.169 24.3 Comparative Example 1 860 490 Good 0.769 26.8 Comparative Example 2 640 455 Good 0.193 22.8 Comparative Example 3 395 320 Fiber exposure 0.092 17.8 Comparative Example 4 459 352 Small amount of fiber exposure 0.103 18.4

[0038] As can be seen from the table: 1. Examples 1-3: The ablation rates of all examples are significantly lower than that of Comparative Example 1, proving that the formula of the present application can effectively improve the ablation resistance of the PP-based composite material. At the same time, they maintain acceptable mechanical properties and use surface quality.

[0039] 2. Example 3: Compared with Comparative Example 2, the addition of titanium aluminum carbide can effectively reduce the amount of inorganic fillers, which is beneficial to the improvement of the mechanical properties of the prepreg tape.

[0040] 2. Comparative Example 1 (without filler): The ablation resistance was extremely poor and the ablation rate was high, proving that inorganic fillers are the key to giving PP ablation resistance.

[0041] 3. Comparative Example 2 (without titanium aluminum carbide): The ablation rate was higher than that of Example 1, demonstrating that titanium aluminum carbide can improve the ablation resistance of PP.

[0042] 4. Comparative Example 3 (Excessive Filler): The mechanical properties deteriorated significantly, and the surface fibers were exposed, indicating that there is an upper limit to the amount of filler added in the PP system. Excessive filler will seriously damage the continuity and processability of the matrix.

[0043] Comparative Example 4 (Titanium Aluminum Carbide without pretreatment): Compared with Example 1, the mechanical properties decreased significantly, and a small amount of exposed fibers were found on the surface, indicating that untreated titanium aluminum carbide affects the impregnation effect of fibers and reduces the mechanical properties of the material.

[0044] This invention successfully develops a continuous fiber-reinforced ablation-resistant composite material based on polypropylene, which offers significant cost advantages and provides a new, competitive material solution for medium- and low-temperature thermal protection. Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of this invention and are not intended to limit it. Any modifications, substitutions, and improvements made based on the concept of this invention should be included within the scope of protection of this invention.

Claims

1. A continuous fiber reinforced polypropylene ablation-resistant prepreg tape material, comprising, by weight, the following raw materials: 100-300 parts of polypropylene; Continuous fiber 200-500 parts; 50-90 parts of inorganic filler; 10-30 parts of titanium aluminum carbide; 5-25 parts compatibilizer; Antioxidant 1-10 parts; 0.5-1 part lubricant.

2. The continuous fiber reinforced polypropylene ablation-resistant prepreg tape material according to claim 1, characterized in that, The polypropylene is a high-flow polypropylene with a melt index of 30~150g / 10min at 230℃ and 2.16kg load.

3. The continuous fiber reinforced polypropylene ablation-resistant prepreg tape material according to claim 1, characterized in that, The continuous fiber is at least one of continuous glass fiber and basalt fiber, and the fiber linear density is 600~2400Tex.

4. The continuous fiber reinforced polypropylene ablation-resistant prepreg tape material according to claim 1, characterized in that, The inorganic filler is at least one of calcined kaolin, wollastonite, expanded vermiculite, and diatomaceous earth. The kaolin has a particle size of 1~10μm and a loss on ignition of no more than 0.5%. The wollastonite has an aspect ratio greater than 10:

1.

5. The continuous fiber reinforced polypropylene ablation-resistant prepreg tape material according to claim 1, characterized in that, The titanium aluminum carbide needs to be pretreated according to the following process: Step (1): Add titanium aluminum carbide powder to a 1-3 wt% dilute hydrochloric acid solution at a ratio of 5-10 g / 100 mL and sonicate for 30-60 minutes. After the reaction, wash with deionized water by centrifugation (8000-10000 rpm, 5 minutes each time) until the pH of the supernatant is neutral (about 5-7 times). Finally, dry thoroughly in an oven at 80-100°C for 6-12 hours. Step (2) Weigh 1.0-2.5% of the silane coupling agent according to the mass of titanium aluminum carbide powder, dissolve it in anhydrous ethanol (coupling agent: ethanol volume ratio is about 1:9); stir and add a small amount of deionized water (accounting for 1-2% of the coupling agent volume), hydrolyze at room temperature for 15-30 minutes to form a clear solution; Step (3): Add the titanium aluminum carbide powder obtained in step (1) to the hydrolysate obtained in step (2) above, and keep the solid-liquid ratio at 1g:10-15mL; react for 2-4 hours in a constant temperature water bath at 70-80°C with a mechanical stirring rate of 300-500 rpm.

6. The continuous fiber reinforced polypropylene ablation-resistant prepreg tape material according to claim 1, characterized in that, The compatibilizer is maleic anhydride-grafted polypropylene, with a maleic anhydride grafting rate of not less than 0.8% and a melt index of not less than 5 g / 10 min.

7. The continuous fiber reinforced polypropylene ablation-resistant prepreg tape material according to claim 1, characterized in that, The antioxidant is at least one of antioxidant 1010, antioxidant 412s, antioxidant 168, and antioxidant 1076.

8. The continuous fiber reinforced polypropylene ablation-resistant prepreg tape material according to claim 1, characterized in that, The lubricant is at least one of calcium stearate and ethylene bis-stearamide.

9. The method for preparing the continuous fiber reinforced polypropylene ablation-resistant prepreg tape material according to any one of claims 1 to 8, characterized in that, The melt impregnation process includes the following steps: (1) Raw material pretreatment and precise metering: Polypropylene, inorganic filler, compatibilizer, antioxidant and lubricant are mixed at high speed at 60-80℃ for 5-10 minutes to obtain pre-dispersed resin mixture, and then put into the main material bin of loss-in-weight weighing scale; (2) Forced melting, dispersion and devolatilization: The mixture in step (1) is melted and mixed at 170~230℃ using a co-rotating parallel twin-screw extruder, with vacuum exhaust in the middle section of the screw, and the vacuum degree is not lower than -0.07MPa; (3) Melt delivery and pressure stabilization: The melt processed in step (2) is stably delivered to the impregnation mold through a gear melt pump; (4) Preheating and dynamic yarn spreading of fibers: After tension adjustment, continuous fibers are preheated at 100~180℃, and then non-contact dynamic yarn spreading is carried out through a hot air knife box. The hot air temperature is 180~220℃ and the air pressure is 0.15~0.30MPa. (5) High pressure and delayed impregnation: The unfolded fibers and the melt from step (3) are combined in the impregnation mold. Multiple impregnation rollers are installed in the mold. The fibers and melt travel along a tortuous path. The mold heating temperature is 190~230℃. (6) Cooling and shaping and winding: The impregnated composite material is cooled and shaped, and then wound up to obtain the prepreg tape material.

10. The method for preparing the continuous fiber reinforced polypropylene ablation-resistant prepreg tape material according to claim 9, characterized in that, The number of impregnation rollers in the impregnation mold is 4-6.