A fluorine-containing small molecule liquid crystal flow modifier and its preparation method and application

Abstract

The invention discloses a kind of fluorine-containing small molecule liquid crystal flow modifier and its preparation method and application;The preparation method is under nitrogen protection, 4,4 '-biphenyl diphenol is added to an organic solvent, after solid is completely dissolved, transferred to an ice bath, acid binding agent is added, p-trifluoromethylbenzoyl chloride is added dropwise under stirring, and room temperature reaction 16 24h after completion of dropwise addition;After reaction terminates, precipitation is separated out, suction filtration, washing, drying, and fluorine-containing small molecule liquid crystal flow modifier is obtained. The fluorine-containing small molecule liquid crystal flow modifier provided by the present invention has a good improvement effect on the processing fluidity of glass fiber reinforced polymer blending system, and 1wt% of the flow modifier is added into glass fiber reinforced nylon 66 blending system, and the equilibrium torque of the blending system decreases by 76.3%.The modifier can also effectively improve the rigidity and toughness of glass fiber reinforced polymer composite material.

Description

Technical Field

[0001] The present invention relates to a flow modifier, in particular to a fluorine-containing small molecule liquid crystal flow modifier and its preparation method and application. The flow modifier is used to improve the processing fluidity of a glass fiber reinforced polymer blend system and enhance the rigidity and toughness of the resulting composite material. Background Art

[0002] Glass fiber reinforced polymer composites have the advantages of low cost, excellent mechanical and heat resistance, and are widely used in the fields of electronics, aerospace, automobiles, etc. However, the addition of glass fiber will increase the viscosity of the polymer blend system and cause poor processing fluidity. Moreover, the greater the amount of glass fiber used, the more difficult it is to disperse in the matrix, the greater the breakage rate, and the resulting polymer composite has many internal structural defects and poor mechanical strength. By adding flow-modifying processing aids to the blend system, the viscosity can be reduced and the dispersion state of the glass fiber can be significantly improved. Liang Yeyun et al. (Preparation of nylon / glass fiber composites with high glass fiber content by hyperbranched polyester, Functional Materials, 2018, 49(06): 6103-6106+6113) used the low entanglement and low viscosity of hyperbranched polymers to play a flow-modifying role. When 1 wt% hyperbranched polyester (DCHP) was added to a 50 wt% glass fiber reinforced nylon 6 blend system, the flow-modifying effect was significant. The melt index of the resulting composite increased by 107%, the tensile strength increased by about 9%, and the flexural strength remained basically unchanged. However, because DCHP weakens intermolecular interactions when it penetrates PA6 molecular chains, the composite's impact strength drops by nearly 16%. Chinese invention patent CN201711446307.4 applies 1wt% of a montmorillonite derivative (RC-620) as a flow modifier to a 50wt% glass fiber-reinforced high-temperature nylon blend. By suppressing intermolecular forces in nylon, RC-620 doubles the melt index of the resulting composite, increasing tensile strength and flexural strength by 15% and 7%, respectively. However, the tensile modulus, flexural modulus, and impact strength remain unchanged.

[0003] Thermotropic liquid crystal polymers (TLCPs), due to their liquid crystal state within the processing temperature range, can promote the disentanglement of matrix polymer chains, effectively reducing melt viscosity. Furthermore, they easily align under external forces to form microfibers, which act as reinforcement. Consequently, they have attracted attention for improving the processing fluidity of glass fiber-reinforced polymer blends. Chinese invention patent CN201010218363.4 incorporates TLCP as a flow modifier into a glass fiber-reinforced nylon blend, effectively improving the processing fluidity of the system. However, the high addition level of TLCP does not significantly improve the mechanical properties of the composite. At a 15wt% TLCP addition, the composite's tensile strength, flexural strength, and flexural modulus only increase by 4.5%, 2.6%, and 1.0%, respectively.

[0004] It can be seen that existing flow-modifying processing aids often reduce the mechanical properties of materials while improving the processing fluidity of glass fiber reinforced polymer blends. Therefore, the development of a flow modifier with low preparation cost, mild reaction conditions, wide application range, and the ability to improve the processing fluidity of glass fiber reinforced polymer blends while improving the rigidity and toughness of composite materials has extremely important industrial value and academic significance. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a fluorine-containing small molecule liquid crystal flow modifier and its preparation method, which has the ability to disperse glass fibers in a glass fiber reinforced polymer blend system, improve the processing fluidity of the system, and improve the rigidity and toughness of the composite material.

[0006] Another object of the present invention is to provide an application of the fluorine-containing small molecule liquid crystal flow modifier in a glass fiber reinforced polymer blend system.

[0007] In order to achieve the above object of the invention, the technical solution of the present invention is as follows:

[0008] A fluorine-containing small molecule liquid crystal flow modifier having the following structural formula:

[0009]

[0010] To further achieve the purpose of the present invention, preferably, the fluorine-containing small molecule liquid crystal flow modifier is a white powder at room temperature and exhibits a liquid crystal state between 246 and 320°C.

[0011] Preferably, under nitrogen protection, 4,4'-biphenyldiphenol is added to an organic solvent. After the solid is completely dissolved, the mixture is transferred to an ice bath, an acid binding agent is added, and p-trifluoromethylbenzoyl chloride is added dropwise with stirring. After the addition is complete, the mixture is reacted at room temperature for 16-24 hours. After the reaction is completed, the precipitate is separated, filtered, washed, and dried to obtain a fluorine-containing small molecule liquid crystal flow modifier.

[0012] Preferably, the organic solvent is one of pyridine, tetrahydrofuran, dichloromethane and chloroform; the organic solvent is treated with molecular sieves to remove water in advance; and the acid binding agent is pyridine or triethylamine.

[0013] Preferably, when pyridine is used as the organic solvent, no additional acid binding agent is needed, as pyridine acts as the acid binding agent.

[0014] Preferably, the molar ratio of 4,4'-biphenol to p-trifluoromethylbenzoyl chloride is 1:2-3; the amount of the organic solvent is 9-12 times the total mass of 4,4'-biphenol and p-trifluoromethylbenzoyl chloride; and the molar number of the acid binding agent is 2.5-4 times that of 4,4'-biphenol.

[0015] Preferably, the dropwise addition of trifluoromethylbenzoyl chloride is completed within 30 to 60 minutes; and the stirring rate is 200 to 250 r / min.

[0016] Preferably, the precipitation is achieved by pouring the obtained reaction solution into a hydrochloric acid aqueous solution; and the washing is achieved by washing the obtained precipitate with a NaHCO3 aqueous solution and deionized water respectively.

[0017] Preferably, the drying is vacuum drying, the drying temperature is 80-100° C., and the drying time is 16-24 h; the concentration of the hydrochloric acid aqueous solution is 1-5 wt %, and the concentration of the NaHCO 3 aqueous solution is 3-8 wt %.

[0018] The invention discloses an application of the fluorine-containing small molecule liquid crystal flow modifier in a glass fiber reinforced polymer blend system. The glass fiber, polymer, fluorine-containing small molecule liquid crystal flow modifier and antioxidant are weighed according to a proportion, mixed evenly, and then added to a twin-screw extruder for melting, extrusion and granulation to obtain a glass fiber reinforced polymer composite material. The amount of the glass fiber is between 30wt% and 60wt%. The polymer is any one with a processing temperature within the range of 246°C to 320°C, such as nylon 6, nylon 66, and polybutylene terephthalate. The amount of the fluorine-containing small molecule liquid crystal flow modifier is 0.25wt% to 1wt%. The amount of the antioxidant is 0.2wt%.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The fluorine-containing small molecule liquid crystal flow modifier provided by the present invention has a good effect on improving the processing fluidity of the glass fiber reinforced polymer blend system. When 1 wt% of the flow modifier is added to the glass fiber reinforced nylon 66 blend system, the equilibrium torque of the blend system decreases by 76.3%.

[0021] (2) The fluorine-containing small molecule liquid crystal flow modifier provided by the present invention can effectively improve the rigidity and toughness of glass fiber reinforced polymer composites. When 1 wt% of the fluorine-containing small molecule liquid crystal flow modifier is added to a glass fiber reinforced nylon 66 blend system, compared with the prior art, the impact strength of the composite material is increased by 19.3%, the elongation at break is increased by 26.3%, the tensile strength is increased by 18.4%, and the flexural strength and flexural modulus are increased by 28.0% and 29.8%, respectively, thereby achieving simultaneous improvement in the rigidity and toughness of the composite material.

[0022] (3) The fluorine-containing small molecule liquid crystal flow modifier provided by the present invention has a simple preparation method, mild reaction conditions, is easy to add, matches the processing temperature of common engineering plastics such as nylon 6, nylon 66, polybutylene terephthalate, etc., has high application value, can be used for large-scale industrial production, and has better effects than the flow modifiers in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 FT-IR spectrum of the fluorinated small molecule liquid crystal flow modifier PPF obtained in Example 1;

[0024] Figure 2 is the H NMR spectrum of the fluorinated small molecule liquid crystal flow modifier PPF obtained in Example 1 ( 1 H NMR) spectra;

[0025] Figure 3 STA curve of the fluorinated small molecule liquid crystal flow modifier PPF obtained in Example 1 at a heating rate of 10°C / min;

[0026] Figure 4 These are polarizing microscope (POM) images of the fluorine-containing small molecule liquid crystal flow modifier PPF obtained in Example 1 at 250° C. and 280° C., respectively. DETAILED DESCRIPTION

[0027] To better support the present invention, the present invention is further illustrated in the following examples, but the embodiments of the present invention are not limited thereto.

[0028] Example 1

[0029] Under nitrogen protection, 0.01 mol of 4,4'-biphenyldiphenol and 60 g of pyridine were added to a 150 mL three-necked flask. After the solid was completely dissolved, it was transferred to an ice bath and, under magnetic stirring, 0.02 mol of trifluoromethylbenzoyl chloride was added dropwise within 60 min at a stirring rate of 200 r / min. The reaction was carried out at room temperature for 16 h. After the reaction, the resulting solution was poured into 420 g of a 1 wt% aqueous hydrochloric acid solution. A precipitate was precipitated and filtered. The precipitate was washed with 420 g of a 3 wt% NaHCO3 aqueous solution and 420 g of deionized water, respectively, and filtered. Finally, the product was dried in a vacuum oven at 80 ° C for 24 h. The obtained white powder was PPF with a yield of 96.8%.

[0030] Take a small amount of product for FT-IR test, the results are as follows Figure 1 , 1735cm in the picture -1 It is the stretching vibration peak of C=O in the ester group, 1332cm -1is the stretching vibration peak of CF in trifluoromethyl, 1496 cm -1 and 1587cm -1 The peak of benzene ring skeleton stretching vibration is 802 cm -1 is the out-of-plane bending vibration peak of CH on the benzene ring; 1 H NMR test, the solvent is deuterated chloroform, the results are as follows Figure 2 As shown, there are four types of hydrogen atom peaks in the spectrum. The peaks at chemical shifts δ = 7.66 ppm and δ = 8.35 ppm correspond to the hydrogen atoms (H1 and H2) on the benzene ring of the original trifluoromethylbenzoyl chloride, and the peaks at chemical shifts δ = 7.32 ppm and δ = 7.80 ppm correspond to the hydrogen atoms (H3 and H4) on the benzene ring of the original 4,4'-biphenyldiphenol. The above infrared spectra and H NMR spectra well prove the synthesis of PPF.

[0031] The liquid crystallinity of the obtained PPF was characterized by STA and POM. Figure 3 and Figure 4 , three endothermic peaks appeared on the STA curve, corresponding to peak temperatures of 246°C, 256°C, and 320°C. Under a polarizing microscope, when the temperature rose to 246°C, the PPF was observed to enter a molten state, the field of view became brighter, and a mosaic structure was presented, which was a high-order smectic phase (SmX) (such as Figure 4 a), and when the temperature is continued to rise to 256℃, the texture changes significantly, showing a focal cone fan-shaped texture (SmC phase) (such as Figure 4 b), the temperature continues to rise, the texture remains unchanged, when the temperature reaches 320℃, the field of view becomes dark, the birefringence disappears, and it becomes isotropic. Figure 3 From the STA curve, we can see that the melting point of PPF (T m ) is 246℃, the clearing point (T i ) is 320℃, and its liquid crystal range is 246℃-320℃.

[0032] Example 2

[0033] Under nitrogen, 0.01 mol of 4,4'-biphenyldiphenol and 65 g of dichloromethane were added to a 150 mL three-necked flask. After the solids completely dissolved, the flask was transferred to an ice bath and 0.025 mol of triethylamine was added. Under magnetic stirring, 0.025 mol of p-trifluoromethylbenzoyl chloride was added dropwise over 40 minutes at a stirring rate of 210 rpm. The reaction was allowed to proceed at room temperature for 20 hours. After the reaction, the resulting solution was poured into 650 g of a 3 wt% aqueous hydrochloric acid solution. A precipitate formed, which was filtered. The precipitate was then washed with 650 g of a 5 wt% aqueous NaHCO solution and 650 g of deionized water, followed by precipitation and filtration. The resulting product was dried in a vacuum oven at 90°C for 20 hours. The resulting white powder was PPF (polypropylene glycol fluoride) with a yield of 95.7%. The structure of the resulting PPF was consistent with that in Example 1.

[0034] Example 3

[0035] Under nitrogen, 0.01 mol of 4,4'-biphenyldiphenol and 90 g of dichloromethane were added to a 150 mL three-necked flask. After the solids completely dissolved, the flask was transferred to an ice bath, 0.04 mol of pyridine was added, and 0.03 mol of p-trifluoromethylbenzoyl chloride was added dropwise over 50 min under magnetic stirring at 220 rpm. The reaction was allowed to proceed at room temperature for 20 h. After the reaction, the resulting solution was poured into 540 g of a 5 wt% aqueous hydrochloric acid solution. A precipitate formed, which was filtered. The precipitate was then washed with 540 g of an 8 wt% aqueous NaHCO solution and 540 g of deionized water, followed by precipitation and filtration. The resulting product was dried in a vacuum oven at 100°C for 16 h. The resulting white powder was PPF (polypropylene glycol fluoride) with a yield of 95.1%. The structure of the resulting PPF was consistent with that in Example 1.

[0036] Example 4

[0037] Under nitrogen, 0.01 mol of 4,4'-biphenyldiphenol and 70 g of tetrahydrofuran were added to a 150 mL three-necked flask. After the solids completely dissolved, the flask was transferred to an ice bath, 0.03 mol of triethylamine was added, and 0.02 mol of p-trifluoromethylbenzoyl chloride was added dropwise over 30 minutes under magnetic stirring at 250 rpm. The reaction was allowed to proceed at room temperature for 20 hours. After the reaction, the resulting solution was poured into 630 g of a 1 wt% aqueous hydrochloric acid solution. A precipitate formed, which was filtered. The precipitate was then washed with 630 g of a 3 wt% aqueous NaHCO solution and 630 g of deionized water, followed by precipitation and filtration. The resulting product was dried in a vacuum oven at 80°C for 24 hours. The resulting white powder was PPF (polypropylene glycol fluoride) with a yield of 96.4%. The structure of the resulting PPF was consistent with that in Example 1.

[0038] Example 5

[0039] Under nitrogen, 0.01 mol of 4,4'-biphenyldiphenol and 70 g of chloroform were added to a 150 mL three-necked flask. After the solids completely dissolved, the flask was transferred to an ice bath, 0.035 mol of pyridine was added, and 0.025 mol of p-trifluoromethylbenzoyl chloride was added dropwise over 50 min under magnetic stirring at 230 rpm. The reaction was allowed to proceed at room temperature for 24 h. After the reaction, the resulting solution was poured into 560 g of a 3 wt% aqueous hydrochloric acid solution. A precipitate formed, which was filtered. The precipitate was then washed with 560 g of a 5 wt% aqueous NaHCO solution and 560 g of deionized water, followed by precipitation and filtration. The resulting product was dried in a vacuum oven at 90°C for 20 h. The resulting white powder was PPF (polypropylene glycol fluoride) with a yield of 94.5%. The structure of the resulting PPF was consistent with that in Example 1.

[0040] Example 6

[0041] Under nitrogen, 0.01 mol of 4,4'-biphenyldiphenol and 97 g of pyridine were added to a 150 mL three-necked flask. After the solids completely dissolved, the flask was transferred to an ice bath. Under magnetic stirring, 0.03 mol of p-trifluoromethylbenzoyl chloride was added dropwise over 40 minutes at a stirring rate of 240 rpm. The reaction was allowed to proceed at room temperature for 24 hours. After the reaction, the resulting solution was poured into 485 g of a 5 wt% aqueous hydrochloric acid solution. A precipitate was filtered and washed with 485 g of an 8 wt% aqueous NaHCO solution and 485 g of deionized water, followed by precipitation and filtration. The resulting product was dried in a vacuum oven at 100°C for 16 hours. The resulting white powder was PPF (polypropylene glycol fluoride) with a yield of 96.0%. The structure of the resulting PPF was consistent with that in Example 1.

[0042] Application Examples

[0043] The fluorinated small molecule liquid crystal flow modifier PPF prepared in Example 1 was used to modify the glass fiber (Chongqing International Composite Materials Co., Ltd., ECS301HP-3-H) reinforced nylon 66 (Huafeng Group Co., Ltd., EP158) blend system, and the raw material ratio (as shown in Table 1) was changed to obtain 1 to 3 application examples. The specific preparation process was as follows: glass fiber, nylon 66, fluorinated small molecule liquid crystal flow modifier PPF and antioxidant (Suzhou Kaibaoli New Materials Co., Ltd.) were weighed according to the ratio. Co., Ltd., tetrakis(2,4-di-tert-butyl)-4,4'-biphenyl diphosphite (PEPQ)) was mixed uniformly and then added to a twin-screw extruder (Model LTE26 / 40, LabTech, Germany) for melting, extrusion, and pelletization to obtain glass fiber reinforced nylon 66 composite pellets. The resulting pellets were dried in a blast oven for 12-24 hours and then injection molded into standard specimens on an injection molding machine (Model EC75N, Toshiba, Japan). The twin-screw extruder barrel temperature was: 265°C for the first zone, 270°C for the second zone, 270°C for the third zone, 275°C for the fourth zone, 280°C for the fifth zone, 285°C for the sixth zone, 285°C for the seventh zone, 275°C for the eighth zone, and 265°C for the ninth zone. The die head was 260°C and the main engine speed was 110 r / min. The temperatures of each zone of the injection molding machine screw are: 270°C for the first zone, 275°C for the second zone, 285°C for the third zone, 280°C for the fourth zone, and 280°C for the nozzle. The mold temperature is maintained between 70 and 90°C during the sample preparation process.

[0044] The fluorine-containing small molecule liquid crystal flow modifier of the present invention contains a fluorine group at the end of the molecule and has a low surface energy. When added to a glass fiber reinforced polymer blend system, the flow modifier tends to be distributed at the interface between the glass fiber and the polymer matrix, reducing the agglomeration of the glass fiber and reducing the friction resistance between the glass fibers and between the glass fibers and the matrix. Compared with thermotropic liquid crystal polymers (TLCPs), the flow modifier not only has the orientation viscosity reduction characteristics of liquid crystals, but also has a low molecular weight, which makes it easier to penetrate between polymer chains, promote the disentanglement of molecular chains, and more effectively improve the processing rheology of the blend system. In addition, the fluorine-containing small molecule liquid crystal flow modifier can improve the dispersion, retention length and orientation of the glass fiber in the matrix of the glass fiber reinforced polymer blend system, increase the contact area between the glass fiber and the matrix, thus ensuring the effective transmission of external stress, thereby improving the rigidity and toughness of the resulting composite material. Specific explanations are as follows:

[0045] Comparative Example 1 used 60 wt% glass fiber reinforced nylon 66 without the addition of the fluorinated small molecule liquid crystal flow modifier PPF. Comparative Example 2 used 60 wt% glass fiber reinforced nylon 66 modified with the commonly used commercially available dendritic nylon flow modifier CYD-701 (Weihai Chenyuan Molecular New Materials Co., Ltd.) as a flow modifier. The raw material ratios are shown in Table 1.

[0046] The equilibrium torque of the blending system was tested by simply mixing the raw materials according to the formula in Table 1 using a RTOI-55 / 20 torque rheometer produced by Guangzhou Putong Experimental Analytical Instrument Co., Ltd. at a temperature of 270°C, a rotation speed of 50 r / min, and a test time of 10 min. The tensile properties of the composite materials were tested according to GB / T 1040.2-2006 using a BTI-FR010TH.A50 tensile testing machine from Zwick Roell, Germany, with sample dimensions of 120 mm × 10 mm × 4 mm and a tensile rate of 50 mm / min. The flexural properties were tested according to GB / T 9341-2008 using a universal materials testing machine from Shimadzu, Japan, with sample dimensions of 80 mm × 10 mm × 4 mm, a simply supported beam lower span of 64 mm, and a test rate of 10 mm / min. The impact properties were tested according to ISO 178:2003 using a cantilever beam impact testing machine from Zwick, Germany, with sample dimensions of 80 mm × 10 mm × 4 mm and a notch depth of 2.54 mm.

[0047] The impact strength, elongation at break, tensile strength, flexural strength and flexural modulus of the composite materials obtained by applying the balanced torque of the blending systems of Examples 1 to 3 and Comparative Examples 1 to 2 are shown in Table 2.

[0048] Table 1 Raw material ratios of application examples 1 to 3 and comparative examples 1 to 2

[0049]

[0050] Table 2 Equilibrium torque of the blending system of the application example and the comparative example and the mechanical properties of the obtained composite materials

[0051]

[0052] As shown in Table 2, for Example 3, which employs the fluorinated small molecule liquid crystal flow modifier PPF of the present invention and 60 wt% glass fiber reinforced nylon 66, the equilibrium torque of the blend is reduced by 76.3% compared to Comparative Example 1, which does not include the flow modifier. Furthermore, the resulting composite material exhibits increases in impact strength, elongation at break, tensile strength, flexural strength, and flexural modulus by 16.7%, 35.1%, 16.9%, 18.4%, and 13.3%, respectively. Compared to Comparative Example 2, which employs the commercially available dendritic nylon flow modifier CYD-701, not only does the equilibrium torque of the blend decrease to a similar degree, but the resulting composite material also exhibits increases in impact strength, elongation at break, tensile strength, flexural strength, and flexural modulus by 19.3%, 26.3%, 18.4%, 28.0%, and 29.8%, respectively. It shows that the fluorine-containing small molecule liquid crystal flow modifier PPF of the present invention not only has the same excellent flow modification effect as the prior art, but also the impact strength, elongation at break, tensile strength, flexural strength and flexural modulus of the resulting composite material are better, and the comprehensive performance advantages are obvious.

[0053] In summary, the fluorinated small molecule liquid crystal flow modifier PPF of the present invention has the liquid crystal orientation viscosity reduction properties and the lubricating properties of the small molecules, which greatly promotes the improvement of the processing fluidity of the glass fiber reinforced nylon 66 blend system, reduces the processing difficulty of the blend system, and improves the impact strength, elongation at break, tensile strength, flexural strength and flexural modulus of the composite material by improving the dispersion, retention length and orientation of the glass fiber in the matrix along the direction of the external force. It is a flow modifier with good comprehensive performance and has great application value in glass fiber reinforced polymer blending modification.

[0054] The embodiments of the present invention are not limited thereto, and any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention shall be considered as equivalent replacement methods and shall be included in the scope of protection of the invention.

Claims

1. A fluorine-containing small molecule liquid crystal flow modifier, characterized in that It has the following structural formula: 。 2. The fluorine-containing small molecule liquid crystal flow modifier according to claim 1, characterized in that: The fluorine-containing small molecule liquid crystal flow modifier is a white powder at room temperature and exhibits a liquid crystal state between 246 and 320 degrees Celsius.

3. The method for preparing the fluorinated small molecule liquid crystal flow modifier according to claim 1, characterized in that: Under nitrogen protection, 4,4'-biphenol is added to an organic solvent. After the solid is completely dissolved, the mixture is transferred to an ice bath, an acid-binding agent is added, and p-trifluoromethylbenzoyl chloride is added dropwise with stirring. After the addition is complete, the mixture is reacted at room temperature for 16-24 hours. After the reaction is complete, the precipitate is separated, filtered, washed, and dried to obtain a fluorinated small molecule liquid crystal flow modifier. The molar ratio of the 4,4'-biphenol to p-trifluoromethylbenzoyl chloride is 1:2-3; the molar number of the acid-binding agent is 2.5-4 times that of the 4,4'-biphenol; and the addition of p-trifluoromethylbenzoyl chloride is completed within 30-60 minutes.

4. The method for preparing the fluorinated small molecule liquid crystal flow modifier according to claim 3, wherein: The organic solvent is one of pyridine, tetrahydrofuran, dichloromethane and chloroform; the organic solvent is treated with molecular sieve to remove water in advance; and the acid binding agent is pyridine or triethylamine.

5. The method for preparing the fluorinated small molecule liquid crystal flow modifier according to claim 4, characterized in that: When pyridine is used as the organic solvent, there is no need to add an acid binding agent, as pyridine acts as the acid binding agent.

6. The method for preparing the fluorinated small molecule liquid crystal flow modifier according to claim 3, characterized in that: The amount of the organic solvent used is 9 to 12 times the total mass of 4,4'-biphenol and p-trifluoromethylbenzoyl chloride.

7. The method for preparing the fluorinated small molecule liquid crystal flow modifier according to claim 3, characterized in that: The stirring speed is 200~250 r / min.

8. The method for preparing the fluorinated small molecule liquid crystal flow modifier according to claim 3, characterized in that: The precipitation is achieved by pouring the obtained reaction solution into a hydrochloric acid aqueous solution; and the washing is achieved by washing the obtained precipitate with a NaHCO3 aqueous solution and deionized water respectively.

9. The method for preparing the fluorinated small molecule liquid crystal flow modifier according to claim 8, characterized in that: The drying is vacuum drying, the drying temperature is 80-100° C., and the drying time is 16-24 h; the concentration of the hydrochloric acid aqueous solution is 1-5 wt %, and the concentration of the NaHCO 3 aqueous solution is 3-8 wt %.

10. Use of the fluorinated small molecule liquid crystal flow modifier according to claim 1 or 2 in a glass fiber reinforced polymer blend system, characterized in that: Glass fiber, polymer, fluorine-containing small molecule liquid crystal flow modifier and antioxidant are weighed according to a proportion, mixed evenly, and then added to a twin-screw extruder for melting, extrusion and granulation to obtain a glass fiber reinforced polymer composite material; the amount of the glass fiber is between 30wt% and 60wt%; the polymer is nylon 6, nylon 66 or polybutylene terephthalate; the amount of the fluorine-containing small molecule liquid crystal flow modifier is 0.25wt% to 1wt%; and the amount of the antioxidant is 0.2wt%.

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