CN114716617B - A highly hydrophilic PVDF material and its preparation method - Google Patents

Abstract

The invention discloses a highly hydrophilic PVDF material and a preparation method thereof. It is prepared by high-temperature melt-grafting of maleic anhydride (MAH) to polyvinylidene fluoride (PVDF). The present invention introduces MAH to graft and modify PVDF, and utilizes the reactivity of the anhydride group on the MAH monomer and the polarity of MAH to effectively enhance the hydrophilicity of PVDF and its miscibility with other polymers, which enables the expansion of PVDF applications are possible.

Description

A highly hydrophilic PVDF material and its preparation method

Technical field

The invention relates to the technical field of polymer composite material grafting, and specifically relates to a highly hydrophilic PVDF material and its preparation method and application.

Background technique

Polyvinylidene fluoride (PVDF) is an important semi-crystalline fluoropolymer. Due to its excellent heat resistance, weather resistance, processability and radiation resistance, PVDF has attracted widespread attention from academia and industry. PVDF is composed of -(CH2-CF2)-repeating units, with a relative density of 1.75-1.78g/cm ³ and a long-term use temperature of -40~150°C. High-performance PVDF composite materials can be obtained by blending PVDF with other polymers. An economical and simple strategy. However, overall improvements are limited due to poor miscibility between PVDF and these polymers.

In addition, the surface energy of PVDF membrane is very low, resulting in strong hydrophobicity of the membrane and poor adhesion of PVDF to metal substrates. Therefore, this not only limits the application of PVDF in membranes but also limits the development of PVDF coatings. Maleic anhydride (MAH) is a polar compound containing many functional groups, especially unsaturated double bonds, and can easily polymerize with other polymers by adding some reagents or by irradiation. Anhydride groups can also react with hydroxyl, carboxyl, amine and other functional groups. Therefore, MAH functionalization of some non-polar polymers is beneficial to increase their compatibility with polar polymers, improve material adhesion and filler-polymer interaction. Obviously, using MAH to modify PVDF is an effective strategy to prepare highly hydrophilic PVDF materials. At the same time, the miscibility of modified PVDF with other polymers can also be improved accordingly. However, it has rarely been used in the past few decades. Report on MAH modified PVDF.

Contents of the invention

Based on the problems existing in the above-mentioned prior art, the present invention provides a highly hydrophilic PVDF material and a preparation method thereof, aiming to graft PVDF with MAH of reactive groups, thereby improving the hydrophilicity of PVDF and its interaction with Miscibility with other polymers.

In order to achieve the above objects, the present invention adopts the following technical solutions:

A method for preparing a highly hydrophilic PVDF material, which is characterized in that the highly hydrophilic PVDF material is prepared by high-temperature melt grafting of maleic anhydride MAH to polyvinylidene fluoride PVDF, which specifically includes the following steps:

S1. Dry MAH and PVDF in the oven;

S2. Open the torque rheometer and set the required parameters (reaction temperature and rotation speed); after the parameters of the torque rheometer reach the set value, place the dried MAH and PVDF in the torque rheometer. in, and add initiator and anthracene free radical stabilizer to it to carry out the reaction; after the reaction is completed, turn off the torque rheometer, take out the reaction product and cool it;

S3. Crush the cooled reaction product into powder and purify it to obtain the target product of highly hydrophilic PVDF material.

Further, the molecular weight of the PVDF is 80,000-200,000, and the PVDF is in the form of particles or powder.

Further, the drying temperature in step S1 is 50-80°C, and the drying time is 12-24 hours.

Further, the reaction temperature in step S2 is 190-210°C, the reaction time is 5-7 min, and the rotation speed of the torque rheometer is 40-60 rpm.

Further, in step S2, the initiator is at least one of benzoyl peroxide (BPO), dicumyl peroxide (DCP), benzoyl tert-butyl peroxide (BPB) and methyl ethyl ketone peroxide. species, the anthracene free radical stabilizer is at least one of divinylanthracene, nonaethylanthracene and distyrylanthracene.

Further, in step S2, the mass ratio of PVDF to MAH is 90 to 97%: 10% to 3%, the initiator accounts for 0.1% to 0.5% of the total mass of PVDF and MAH, and the anthracene free radical stabilizer Accounting for 0.1% to 0.5% of the total mass of PVDF and MAH.

Furthermore, the crushing described in step S3 is cryogenic crushing, and the equipment used is a cryogenic crusher. Because the reaction product is a plastic material, conventional crushers cannot fully crush it.

Further, the purification method described in step S3 is: adding N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO) or N,N-dimethylacetamide (DMAC) to the reaction product. ) in an oil bath at 40-60°C for 2 hours to dissolve the reaction product; then pour the solution into excess ethanol to precipitate, let it stand, filter with suction, wash thoroughly with acetone, and dry.

The beneficial effects of the present invention are reflected in:

The present invention grafts PVDF by introducing MAH under the action of anthracene free radical stabilizer, and utilizes the reactivity of the anhydride group on the MAH monomer and the polarity of MAH to effectively enhance the hydrophilicity of PVDF and its interaction with The miscibility of other polymers makes it possible to expand the application of PVDF.

Description of the drawings

Figure 1 is a water contact angle diagram of the products obtained in Example 1 and Comparative Example 1 of the present invention, in which (a) is pure PVDF, (b) is PVDF/MAH obtained in Comparative Example 1, (c) is PVDF- obtained in Example 1 g-MAH;

Figure 2 is a tensile test chart of the products obtained in Example 1 and Comparative Example 1 of the present invention;

Figure 3 is an XRD pattern of the product obtained in Example 1 and Comparative Example 1 of the present invention;

Figure 4 is the Fourier transform infrared spectrum of the products obtained in Example 1 and Comparative Example 1 of the present invention.

Detailed ways

The following is a detailed description of the embodiments of the present invention. This embodiment is implemented based on the technical solution of the present invention and provides detailed implementation modes and specific operating processes. However, the protection scope of the present invention is not limited to the following implementations. example.

Example 1

In this example, the PVDF-g-MAH material is prepared according to the following steps:

S1. Dry MAH and PVDF (molecular weight 150,000, particles) in an oven at 80°C for 20 hours to remove excess moisture in the material.

S2. Open the torque rheometer and set the required parameters (reaction temperature 200°C and rotation speed 50rpm); after the parameters of the torque rheometer reach the set value, combine the dried MAH (2g) and PVDF ( 20g) was placed in a torque rheometer, and DCP (0.05g), BPO (0.05g) and 9-vinylanthracene (0.05g) were added to it, and the reaction was carried out at 200°C for 6 minutes; after the reaction was completed, Turn off the torque rheometer, take out the reaction product and cool it.

(3) Put the cooled reaction product into a cryogenic crusher for full crushing to make powder; add the powder into a round-bottomed flask and stir it in an oil bath at 50°C for 2 hours to dissolve the reaction product ; Then pour the solution into excess ethanol to precipitate, let it stand, filter with suction, wash thoroughly with acetone, and dry to obtain the target product highly hydrophilic PVDF material, recorded as PVDF-g-MAH.

Comparative example 1

In this comparative example, the MAH and PVDF blend material was prepared according to the following steps:

S1. Dry MAH and PVDF (molecular weight 150,000, particles) in an oven at 80°C for 20 hours to remove excess moisture in the material.

S2. Open the torque rheometer and set the required parameters (reaction temperature 200°C and rotation speed 50rpm); after the parameters of the torque rheometer reach the set value, combine the dried MAH (2g) and PVDF ( 20g) was placed in a torque rheometer and reacted at 200°C for 6 minutes; after the reaction, turn off the torque rheometer, take out the reaction product and cool it.

(3) Put the cooled reaction product into a cryogenic crusher for full crushing to make powder; add the powder into a round-bottomed flask and stir it in an oil bath at 50°C for 2 hours to dissolve the reaction product ; Then pour the solution into excess ethanol to precipitate, let it stand, filter with suction, wash thoroughly with acetone, and dry to obtain a blend material of MAH and PVDF, recorded as PVDF/MAH.

Figure 1 is a water contact angle diagram of the products obtained in Example 1 and Comparative Example 1, in which (a) is pure PVDF, (b) is PVDF/MAH obtained in Comparative Example 1, (c) is PVDF-g- obtained in Example 1 MAH. It can be seen from the figure that the hydrophilicity of PVDF-g-MAH is much better than that of PVDF/MAH, which shows that grafting MAH to PVDF can significantly improve the hydrophilicity of PVDF.

A tensile test was performed on the samples obtained in Example 1 and Comparative Example 1, and the results are shown in Figure 2. It can be seen that the elongation at break of PVDF-g-MAH obtained in Example 1 is 502.1MPa, and the elongation at break of PVDF/MAH obtained in Comparative Example 1 is 353.4MPa. It can be seen that compared with direct blending, the elongation at break of the grafted material is significantly increased.

Figure 3 is the XRD pattern of the product obtained in Example 1 and Comparative Example 1. It can be seen from the figure that MAH grafting has no effect on the crystal form of PVDF, while the crystal form of PVDF in the blend of PVDF and MAH is affected to a certain extent. influence, but no crystalline form of MAH appears.

Figure 4 is the Fourier transform infrared spectrum of the product obtained in Example 1 and Comparative Example 1. It can be seen from the figure that compared with PVDF/MAH, PVDF-g-MAH has obvious differences at around 1783cm ^-1 and 1850cm ^-1 The absorption peak, which is the characteristic absorption peak of MAH, further indicates that MAH is successfully grafted on PVDF.

The above are only exemplary embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the present invention. within.

Claims (6)

1. A method for improving the hydrophilicity of PVDF, characterized by: the maleic anhydride MAH is subjected to high-temperature melt grafting to polyvinylidene fluoride PVDF so as to improve the hydrophilicity of the PVDF and obtain a high-hydrophilicity PVDF material, which comprises the following steps:

s1, drying MAH and PVDF in an oven;

s2, placing the dried MAH and PVDF in a torque rheometer, adding an initiator and an anthracene free radical stabilizer into the torque rheometer, and reacting at 190-210 ℃ for 5-7min at 40-60rpm; after the reaction is finished, the torque rheometer is closed, and the reaction product is taken out and cooled;

the initiator is at least one of benzoyl peroxide, dicumyl peroxide, tert-butyl benzoyl peroxide and methyl ethyl ketone peroxide, and the anthracene free radical stabilizer is at least one of divinyl anthracene, nonaethyl anthracene and distyryl anthracene;

the mass ratio of PVDF to MAH is 90-97%: 10 to 3 percent of initiator accounting for 0.1 to 0.5 percent of the total mass of PVDF and MAH, and 0.1 to 0.5 percent of anthracene free radical stabilizer accounting for the total mass of PVDF and MAH;

s3, crushing the cooled reaction product into powder and purifying to obtain the target product high-hydrophilicity PVDF material.

2. The method according to claim 1, characterized in that: the molecular weight of PVDF is 80000-200000, and PVDF is particles or powder.

3. The method according to claim 1, characterized in that: the drying temperature in the step S1 is 50-80 ℃ and the drying time is 12-24h.

4. The method according to claim 2, characterized in that: the crushing in the step S3 is cryogenic crushing.

5. The method according to claim 2, characterized in that: the purification method in the step S3 is as follows: adding the reaction product into DMF, DMSO or DMAC, and stirring for 2 hours at 40-60 ℃ in an oil bath pot to dissolve the reaction product; and then pouring the solution into excessive ethanol for precipitation, standing, filtering, fully washing with acetone, and drying.

6. A PVDF material of high hydrophilicity obtained by the method of any one of claims 1 to 5.