A method of enhancing liquid crystalline polyarylate nanofibers

Abstract

The present application relates to a kind of methods for enhancing liquid crystal state polyarylate nanofiber, it includes the following steps: S1.Liquid crystal state polyarylate nanofiber is added to high-boiling organic solvent, stirring dispersion is formed fiber suspension;S2.Under vacuum or inert gas environment, fiber suspension is carried out preliminary heat treatment;S3.In inert gas environment, high-boiling organic solvent in fiber suspension is removed by rotary evaporation under reduced pressure, and rotary evaporation process is the second heat treatment to liquid crystal state polyarylate nanofiber;S4.In inert gas environment, the nanofiber obtained in S3 is carried out third heat treatment, and the temperature gradient of three consecutive heat treatments increases.The advantage is, the present application improves the orientation degree, crystallinity and molecular weight of liquid crystal state polyarylate nanofiber by progressive heat treatment step, so that nanofiber shows excellent performance at high temperature, and the mechanical properties are enhanced, and the present application provides new possibility for the performance optimization and multi-field application of liquid crystal state polyarylate nanofiber.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of nanofibers, and particularly relates to a method for reinforcing liquid crystal state polyarylate nanofibers. BACKGROUND

[0002] Liquid crystal state polyarylate fibers are high-performance fibers prepared by a melt spinning method, have the advantages of low cost and less environmental pollution, and do not need to use complicated process steps such as post-drawing in the preparation process. When the molecular weight of polyarylate is large, the problems of increased melting point and melt spinning difficulty are caused, and therefore, a polyarylate chip with a lower molecular weight is usually used for melt spinning. The fiber prepared in this way has a small molecular weight, and thus has poor application performance. Continuous liquid crystal state polyarylate fibers can be treated by a heat treatment process to significantly improve their thermal and mechanical properties. However, when liquid crystal state polyarylate nanofibers are treated by a conventional heat treatment process, due to the small size and large surface area of the nanofibers, the nanofibers are more easily affected by heat at high temperatures, and the nanofibers are prone to melt and adhere to lose the nanoscale characteristics, and even cause decomposition reactions. SUMMARY

[0003] The technical problem to be solved by the application is to provide a method for reinforcing liquid crystal state polyarylate nanofibers, so as to effectively improve the mechanical properties of the liquid crystal state polyarylate nanofibers and overcome the above-mentioned deficiencies in the prior art.

[0004] The technical solution of the application for solving the above technical problem is as follows: a method for reinforcing liquid crystal state polyarylate nanofibers, comprising the following steps:

[0005] S1. Liquid crystal state polyarylate nanofibers are added to a high-boiling organic solvent, stirred and uniformly dispersed to form a fiber suspension;

[0006] S2. The fiber suspension is subjected to primary heat treatment under vacuum or an inert gas environment, the temperature of the primary heat treatment is not higher than 150 DEG C, and the treatment time is not longer than 120 min;

[0007] S3. The high-boiling organic solvent in the fiber suspension after the primary heat treatment is removed by rotary evaporation under reduced pressure in an inert gas environment, the rotary evaporation process is the second heat treatment of the liquid crystal state polyarylate nanofibers, the temperature of the second heat treatment is higher than that of the primary heat treatment and not higher than 280 DEG C, and the treatment time is not longer than 120 min;

[0008] S4. The liquid crystal state polyarylate nanofibers obtained in S3 are subjected to third heat treatment in an inert gas environment, the temperature of the third heat treatment is higher than that of the second heat treatment and not higher than 500 DEG C, the treatment time is not longer than 3200 min, and the reinforced liquid crystal state polyarylate nanofibers are obtained after the treatment is completed.

[0009] On the basis of the above technical solutions, the application can further have the following specific choices.

[0010] Specifically, the fiber diameter of the liquid crystal state polyarylate nanofiber in S1 is 100-300 nm, and the dosage ratio of the liquid crystal state polyarylate nanofiber in S1 to the high-boiling organic solvent is 0.1 g: 100-400 mL.

[0011] Specifically, the high-boiling organic solvent in S1 is one or more of ethylene glycol monomethyl ether, octane, butyl acetate, chlorobenzene, N,N-dimethylformamide, cyclohexanone, dimethyl sulfoxide, ethylene glycol, N-methyl pyrrolidone, benzyl alcohol, dimethyl carbonate, ethyl benzoate, and dodecane.

[0012] Specifically, the inert gas environment in S2, S3 and S4 is composed of one or more of nitrogen, neon, argon, krypton and xenon.

[0013] Specifically, the first heat treatment and the second heat treatment adopt a hot bath heating method, and the third heat treatment is to expose the sample to a high-temperature inert gas for treatment.

[0014] Specifically, the hot bath temperature of the first heat treatment is 60-150 DEG C, and the hot bath time is 30-120 min.

[0015] Specifically, in the second heat treatment, the pressure condition is 1.3-2.0 kpa, the hot bath temperature is 150-280 DEG C, and the hot bath time is 30-120 min.

[0016] Specifically, the temperature of the third heat treatment is 280-500 DEG C, and the treatment time is 1200-3200 min.

[0017] Compared with the prior art, the application has the following beneficial effects:

[0018] The present application improves the orientation degree, crystallinity and molecular weight of liquid crystal state polyarylate nanofiber through progressive heat treatment steps. The liquid crystal state polyarylate nanofiber is uniformly dispersed in an organic solution, which avoids the agglomeration or aggregation of the nanofiber, is beneficial to subsequent processing and handling processes, and the progressive high-temperature treatment gradually improves the crystallinity of the nanofiber, reduces the fiber adhesion and thermal decomposition of the nanofiber in high-temperature treatment. At high temperature, the molecular chain movement of the fiber is active, which helps the directional arrangement of the molecular chain, thereby improving the fiber orientation degree, and the macromolecular structure is further improved, thereby improving the fiber crystallinity. At the same time, under high temperature conditions, the liquid crystal state polyarylate fiber performs solid phase polycondensation, the terminal group continues to react, the molecular chain grows, and the molecular weight is improved. This optimization makes the nanofiber perform well at high temperature, and enhances the mechanical properties. The improved nanofiber has potential applications in the fields of nanocomposites, nanofilms, biomedical materials, sensors, optical materials, flexible electronic devices and textiles. The disclosed enhancement method provides new possibilities for performance optimization and multi-field application of liquid crystal state polyarylate nanofiber. DETAILED DESCRIPTION

[0019] The present application will be further described in detail below in combination with specific examples, and the examples are only used to explain the present application and are not used to limit the scope of the present application.

[0020] For the sake of brevity, the solvents or the remaining raw materials used in the following examples are all commercially available products if not specifically stated, and the methods used are all conventional methods in the art if not specifically stated.

[0021] Example 1

[0022] A method for enhancing liquid crystal state polyarylate nanofiber, comprising the following steps:

[0023] S1. 0.1 g of liquid crystal state polyarylate nanofiber (fiber diameter of 100-300 nm) is added to 100 mL of high-boiling organic solvent ethylene glycol, stirred for 35-37 min to uniformly disperse, forming a fiber suspension;

[0024] S2. The fiber suspension is subjected to primary heat treatment under an inert gas environment formed by nitrogen, the heating bath temperature of the primary heat treatment is 70-75℃, and the treatment time is 45-47 min;

[0025] S3. The high-boiling organic solvent in the fiber suspension after the primary heat treatment is removed by rotary evaporation under reduced pressure under the inert gas environment formed by nitrogen, the rotary evaporation process is the second heat treatment of the liquid crystal state polyarylate nanofiber, the pressure condition is 1.3-1.4 kPa during the rotary evaporation under reduced pressure, the heating bath temperature of the second heat treatment is 130-132℃, and the treatment time is 70-75 min;

[0026] S4. In an inert gas environment formed by nitrogen, the liquid crystal state polyarylate nanofiber obtained in S3 is subjected to a third heat treatment, the temperature of the third heat treatment is 280-290℃, the processing time is 2160-2220min, and the reinforced liquid crystal state polyarylate nanofiber is obtained after the processing is completed.

[0027] It is detected that the breaking strength of the prepared reinforced liquid crystal state polyarylate nanofiber is 1.5-1.6Gpa, and the decomposition temperature is 520-525℃.

[0028] Example 2

[0029] A method for reinforcing liquid crystal state polyarylate nanofiber, comprising the following steps:

[0030] S1. 0.1g of liquid crystal state polyarylate nanofiber (fiber diameter is 100-300nm) is added into 300mL high-boiling organic solvent ethyl benzoate, stirred for 45-50min to uniformly disperse, and a fiber suspension is formed;

[0031] S2. In an inert gas environment formed by nitrogen, the fiber suspension is subjected to a first heat treatment, the heating bath temperature of the first heat treatment is 108-110℃, and the processing time is 98-100min;

[0032] S3. In an inert gas environment formed by nitrogen, the high-boiling organic solvent in the fiber suspension after the first heat treatment is removed by rotary evaporation, the rotary evaporation process is a second heat treatment of the liquid crystal state polyarylate nanofiber, the pressure condition during the rotary evaporation is 1.4-1.5kPa, the heating bath temperature of the second heat treatment is 210-213℃, and the processing time is 100-102min;

[0033] S4. In an inert gas environment formed by nitrogen, the liquid crystal state polyarylate nanofiber obtained in S3 is subjected to a third heat treatment, the temperature of the third heat treatment is 280-290℃, the processing time is 2160-2220min, and the reinforced liquid crystal state polyarylate nanofiber is obtained after the processing is completed.

[0034] It is detected that the breaking strength of the prepared reinforced liquid crystal state polyarylate nanofiber is 1.7-1.8Gpa, and the decomposition temperature is 530-532℃.

[0035] This example uses a higher-boiling organic solution, increases the amount of organic solvent, prolongs the time of the two heating baths and increases the processing temperature, which helps the molecular chain movement of the nanofiber, the rearrangement and integration of the molecular structure, the formation of a more ordered crystal structure, the reduction of the adhesion and decomposition of the nanofiber during the high-temperature treatment in the inert gas, and the improvement of the breaking strength and decomposition temperature of the nanofiber.

[0036] Example 3

[0037] A method for reinforcing liquid crystal state polyarylate nanofiber, comprising the following steps:

[0038] S1. 0.1 g of liquid crystal state polyarylate nanofiber (fiber diameter 100-300 nm) is added into 300 mL of high-boiling organic solvent ethyl phenylacetate, stirred for 45-50 min to uniformly disperse, to form a fiber suspension;

[0039] S2. The fiber suspension is subjected to primary heat treatment under an inert gas environment formed by nitrogen, the heating bath temperature of the primary heat treatment is 108-110°C, and the treatment time is 98-100 min;

[0040] S3. The high-boiling organic solvent in the fiber suspension after the primary heat treatment is removed by rotary evaporation under reduced pressure under an inert gas environment formed by nitrogen, the rotary evaporation process is the second heat treatment of the liquid crystal state polyarylate nanofiber, the pressure condition during the rotary evaporation under reduced pressure is 1.7-1.8 kPa, the heating bath temperature of the second heat treatment is 210-213°C, and the treatment time is 100-102 min;

[0041] S4. The liquid crystal state polyarylate nanofiber obtained in S3 is subjected to third heat treatment under an inert gas environment formed by nitrogen, the temperature of the third heat treatment is 356-360°C, the treatment time is 2160-2220 min, and the reinforced liquid crystal state polyarylate nanofiber is obtained after the treatment is completed.

[0042] It is detected that the breaking strength of the prepared reinforced liquid crystal state polyarylate nanofiber is 2.5-2.6 Gpa, and the decomposition temperature is 540-545°C.

[0043] This embodiment increases the temperature of the nanofiber high-temperature treatment in the inert gas, increases the activity of the molecular chain end groups in the amorphous region of the nanofiber, accelerates the solid-phase polycondensation rate, greatly increases the molecular weight, and is beneficial to improving the breaking strength and decomposition temperature of the nanofiber.

[0044] Example 4

[0045] A method for reinforcing liquid crystal state polyarylate nanofiber, comprising the following steps:

[0046] S1. 0.1 g of liquid crystal state polyarylate nanofiber (fiber diameter 100-300 nm) is added into 300 mL of high-boiling organic solvent ethyl phenylacetate, stirred for 45-50 min to uniformly disperse, to form a fiber suspension;

[0047] S2. Under the inert gas environment formed by nitrogen, the fiber suspension is subjected to primary heat treatment, the heating bath temperature of the primary heat treatment is 108-110℃, and the treatment time is 98-100 min;

[0048] S3. Under the inert gas environment formed by nitrogen, the high-boiling organic solvent in the fiber suspension after the primary heat treatment is removed by rotary evaporation under reduced pressure using a rotary evaporator, the rotary evaporation process is the second heat treatment of the liquid crystalline polyarylate nanofiber, the pressure condition is 1.7-1.8 kPa during the rotary evaporation under reduced pressure, the heating bath temperature of the second heat treatment is 210-213℃, and the treatment time is 100-102 min;

[0049] S4. Under the inert gas environment formed by neon, the liquid crystalline polyarylate nanofiber obtained in S3 is subjected to third heat treatment, the temperature of the third heat treatment is 356-360℃, the treatment time is 2880-2940 min, and the reinforced liquid crystalline polyarylate nanofiber is obtained after the treatment is completed.

[0050] It is detected that the breaking strength of the prepared reinforced liquid crystalline polyarylate nanofiber is 2.9-3.0 Gpa, and the decomposition temperature is 567-570℃.

[0051] The embodiment prolongs the time of high-temperature treatment of the nanofiber in the inert gas, increases the crystallinity of the nanofiber, increases the grain size, and improves the crystallization, and increases the solid-phase polycondensation time and the molecular weight, which is beneficial to improve the breaking strength and the decomposition temperature of the nanofiber.

[0052] Example 5

[0053] A method for reinforcing liquid crystalline polyarylate nanofiber, comprising the following steps:

[0054] S1. 0.1 g of liquid crystalline polyarylate nanofiber (fiber diameter is 100-300 nm) is added into 300 mL of high-boiling organic solvent ethyl benzoate, stirred for 45-50 min to uniformly disperse, and a fiber suspension is formed;

[0055] S2. Under the inert gas environment formed by nitrogen, the fiber suspension is subjected to primary heat treatment, the heating bath temperature of the primary heat treatment is 108-110℃, and the treatment time is 98-100 min;

[0056] S3. Under the inert gas environment formed by nitrogen, the high-boiling organic solvent in the fiber suspension after the primary heat treatment is removed by rotary evaporation under reduced pressure using a rotary evaporator, the rotary evaporation process is the second heat treatment of the liquid crystalline polyarylate nanofiber, the pressure condition is 1.7-1.8 kPa during the rotary evaporation under reduced pressure, the heating bath temperature of the second heat treatment is 210-213℃, and the treatment time is 100-102 min;

[0057] S4. In the inert gas environment formed by neon, the liquid crystal state polyarylate nanofiber obtained in S3 is subjected to third heat treatment, the temperature of the third heat treatment is 356-360℃, the processing time is 3120-3180 min, and the reinforced liquid crystal state polyarylate nanofiber is obtained after the processing is completed.

[0058] It is detected that the breaking strength of the prepared reinforced liquid crystal state polyarylate nanofiber is 3.0-3.1 Gpa, and the decomposition temperature is 572-575℃.

[0059] This example again prolongs the time of high-temperature treatment of the nanofiber in the inert gas. The orientation degree, crystallization and molecular weight of the nanofiber change significantly in the early stage of high-temperature treatment, so that after the high-temperature treatment for a long time, the increase of the high-temperature treatment time has little effect on the breaking strength and decomposition temperature of the nanofiber.

[0060] Example 6

[0061] A method for reinforcing liquid crystal state polyarylate nanofiber, comprising the following steps:

[0062] S1. 0.1 g of liquid crystal state polyarylate nanofiber (fiber diameter is 100-300 nm) is added into 300 mL of high-boiling organic solvent ethyl benzoate, stirred for 45-50 min to uniformly disperse, and a fiber suspension is formed;

[0063] S2. In the inert gas environment formed by nitrogen, the fiber suspension is subjected to primary heat treatment, the heating bath temperature of the primary heat treatment is 108-110℃, and the processing time is 98-100 min;

[0064] S3. In the inert gas environment formed by nitrogen, the high-boiling organic solvent in the fiber suspension after the primary heat treatment is removed by rotary evaporation under reduced pressure using a rotary evaporator, the rotary evaporation process is the second heat treatment of the liquid crystal state polyarylate nanofiber, the pressure condition is 1.7-1.8 kPa during the rotary evaporation under reduced pressure, the heating bath temperature of the second heat treatment is 210-213℃, and the processing time is 100-102 min;

[0065] S4. In the inert gas environment formed by neon, the liquid crystal state polyarylate nanofiber obtained in S3 is subjected to third heat treatment, the temperature of the third heat treatment is 480-490℃, the processing time is 3120-3180 min, and the reinforced liquid crystal state polyarylate nanofiber is obtained after the processing is completed.

[0066] It is detected that the breaking strength of the prepared reinforced liquid crystal state polyarylate nanofiber is 2.8-2.9 Gpa, and the decomposition temperature is 550-555℃.

[0067] The embodiment again increases the temperature of high-temperature treatment of the nanofiber in inert gas. If the temperature is too high, the long-range order of the molecular chain in the nanofiber is destroyed, but the short-range order is still retained, the orientation degree and the crystallinity are reduced, and thus the breaking strength and the decomposition temperature of the nanofiber are affected.

[0068] The breaking strength of the liquid crystal state polyarylate nanofiber used in each of the above embodiments is averagely between 0.7-0.9 Gpa, and the decomposition temperature is between 513-518℃. As known from each of the above embodiments, the breaking strength of the reinforced liquid crystal state polyarylate nanofiber obtained after the reinforcing treatment provided by the application is between 1.2-3.2 Gpa, and the decomposition temperature is between 520-580℃, and the reinforcing effect is obvious.

[0069] The above only describes the preferred embodiments of the application and is not intended to limit the application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the application shall be included in the protection scope of the application.

Claims

1. A method for reinforcing liquid crystal polyarylate nanofibers, characterized in that: The following steps are involved: S1. The liquid crystal polyarylate nanofibers are added to a high boiling point organic solvent and stirred to form a fiber suspension; S2. Performing a primary heat treatment on the fiber suspension in a vacuum or inert gas environment, wherein the temperature of the primary heat treatment does not exceed 150°C and the treatment time does not exceed 120 minutes; S3. Under an inert gas environment, a rotary evaporator is used to remove the high-boiling-point organic solvent from the fiber suspension after the initial heat treatment. The rotary evaporation process is a second heat treatment of the liquid crystal polyarylate nanofibers. The temperature of the second heat treatment is higher than the temperature of the initial heat treatment and does not exceed 280°C. The treatment time does not exceed 120 min. S4. Under an inert gas environment, the liquid crystal polyarylate nanofibers obtained in S3 are subjected to a third heat treatment. The temperature of the third heat treatment is higher than the temperature of the second heat treatment and does not exceed 500°C. The treatment time does not exceed 3200 minutes. After the treatment is completed, the reinforced liquid crystal polyarylate nanofibers are obtained.

2. The method for reinforcing liquid crystal polyarylate nanofibers according to claim 1, wherein: The fiber diameter of the liquid crystal polyarylate nanofiber in S1 is 100-300 nm, and the usage ratio of the liquid crystal polyarylate nanofiber in S1 to the high boiling point organic solvent is 0.1 g:100-400 mL.

3. The method for reinforcing liquid crystal polyarylate nanofibers according to claim 1, wherein: The high-boiling point organic solvent in S1 is one or more of ethylene glycol monomethyl ether, octane, butyl acetate, chlorobenzene, N,N-dimethylformamide, cyclohexanone, dimethyl sulfoxide, ethylene glycol, N-methylpyrrolidone, benzyl alcohol, diformate, ethyl benzoate, and dodecane.

4. The method for reinforcing liquid crystal polyarylate nanofibers according to claim 1, wherein: The inert gas environment in S2, S3 and S4 is composed of one or more of nitrogen, neon, argon, krypton and xenon.

5. The method for reinforcing liquid crystal polyarylate nanofibers according to any one of claims 1 to 4, characterized in that: The first heat treatment and the second heat treatment are both performed by hot bath heating, and the third heat treatment is performed under exposure to high temperature inert gas.

6. The method for reinforcing liquid crystal polyarylate nanofibers according to claim 5, characterized in that: The heating bath temperature of the initial heat treatment is 60-150°C, and the heating bath time is 30-120 minutes.

7. The method for reinforcing liquid crystal polyarylate nanofibers according to claim 5, characterized in that: During the second heat treatment, the pressure condition is 1.3-2.0 kPa, the heat bath temperature is 150-280° C., and the heat bath time is 30-120 min.

8. The method for reinforcing liquid crystal polyarylate nanofibers according to claim 1, characterized in that: The temperature of the third heat treatment is 280-500°C, and the treatment time is 1200-3200 minutes.