Polyvinylidene fluoride / polar polymer composite material and preparation method thereof

Abstract

The invention relates to the technical field of high polymer materials, and discloses a polyvinylidene fluoride / / polar polymer composite material and a preparation method thereof. The preparation method comprises the following steps: mixing a polar polymer, polyvinylidene fluoride, a modified monomer and a compound initiator, adding the mixture into an extruder, controlling the reaction temperature of a first zone of the extruder to be 175-185 DEG C and the reaction temperature of a second zone to be 205-215 DEG C, cooling the obtained material, granulating, and drying. Two initiators with different decomposition temperatures are compounded according to a certain proportion, so that the compounded initiator is slowly decomposed in a first region of an extruder to generate primary free radicals, and then modified monomers are initiated to be quickly grafted in a second region, so that the free radical concentration is remarkably increased, the activity time is remarkably prolonged, the grafting reaction activation energy is reduced, and the grafting efficiency is improved. The controllable grafting of the modified monomer on the polyvinylidene fluoride is realized, and the grafting rate is increased, so that the problem of interfacial compatibility between the polar polymer and the polyvinylidene fluoride can be effectively improved.

Description

Technical Field

[0001] The present application relates to the technical field of polymer materials, and in particular to a polyvinylidene fluoride / polar polymer composite material and a preparation method thereof. Background Art

[0002] As energy demand grows, the safety and durability of oil and gas pipelines become key challenges. Polyamide (PA), a commonly used barrier material, possesses excellent mechanical properties and chemical stability, but it is susceptible to hydrolysis under high-temperature and high-pressure environments, leading to pipeline performance degradation. To improve barrier performance, polyvinylidene fluoride (PVDF) can be added to the inner layer of PA pipelines. PVDF's hydrolysis and chemical resistance effectively compensate for the shortcomings of PA.

[0003] However, the interfacial compatibility between PVDF and PA is a prominent issue. Due to their significant polarity differences, the blended materials are prone to delamination. Traditional physical blending methods struggle to achieve molecular-level dispersion, while grafting modification offers new avenues for interfacial optimization. Studies have shown that techniques such as ionizing radiation grafting and solution grafting typically require additional post-processing steps, resulting in complex processes and demanding conditions. However, existing melt grafting methods suffer from low grafting yields (<5%).

[0004] Therefore, how to improve the interfacial compatibility between polymers, such as PVDF / PA, and thus develop PVDF / polar polymer composite materials with high compatibility, high hydrophilicity and high strength is very necessary to meet the needs of oil and gas barriers, pipeline transportation and other fields. Summary of the Invention

[0005] In view of this, the primary purpose of the present application is to provide a method for preparing a PVDF / polar polymer composite material to effectively improve the interfacial compatibility between PVDF and polar polymers.

[0006] Another object of the present application is to provide a PVDF / polar polymer composite material with good hydrophilicity and high strength.

[0007] According to an embodiment of the present application, in a first aspect, a method for preparing a PVDF / polar polymer composite material is provided, comprising the following steps:

[0008] S1, mixing PVDF, polar polymer, modified monomer and compound initiator to form a mixed material;

[0009] Wherein, the composite initiator comprises a first initiator and a second initiator in a mass ratio of 1 to 3:1, and the decomposition temperature T1 (t 1 / 2 =0.1h) is not less than 110°C, the decomposition temperature T2 (t 1 / 2=0.1h) is less than 110°C;

[0010] S2, adding the mixture obtained in S1 to an extruder, and reacting in the first zone and the second zone of the extruder in sequence, controlling the reaction temperature of the first zone to be 175° C. to 185° C., and the reaction temperature of the second zone to be 205° C. to 215° C.;

[0011] S3. Cooling the material obtained in S2, granulating it, and drying it to obtain a PVDF / polar polymer composite material.

[0012] It should be noted that the existing melt grafting technology uses a high-temperature initiator to perform melt grafting at 170°C to 190°C. The initiator has a long half-life, slow decomposition efficiency, low active free radical concentration, low grafting rate, and limited improvement in interface compatibility. If the concentration of the high-temperature initiator is increased, the product will have a high degree of cross-linking, affecting product performance.

[0013] Therefore, the present application compounds a first initiator and a second initiator with different decomposition temperatures in a certain proportion, so that the compounded initiator slowly decomposes in the first zone (i.e., the low-temperature zone) of the extruder to produce primary free radicals, triggering a preliminary reaction, and then rapidly decomposes in the second zone (i.e., the high-temperature zone) to produce a large number of free radicals, which synergistically trigger the rapid grafting of the modified monomer, significantly increasing the free radical concentration and active time, reducing the activation energy of the grafting reaction, and increasing the grafting rate, thereby effectively improving the interface compatibility problem of the composite material.

[0014] The present application study found that if the mass ratio of the first initiator to the second initiator is too small (less than 1:1), the concentration of active free radicals will be low, thereby reducing the grafting rate. On the contrary, when the mass ratio of the first initiator to the second initiator is too large (greater than 3:1), due to the high reaction temperature, the first initiator will decompose and become ineffective too quickly, which will also affect the grafting rate. In addition, monomers with poor heat resistance are also prone to decomposition at higher temperatures. For example, sulfonic acid groups easily absorb water at high temperatures and hydrolyze into sulfate groups, which is not conducive to improving the interfacial compatibility problem.

[0015] In this application, the term " 1 / 2 " is the half-life of the initiator, which refers to the time required for the initiator to decompose to half of its initial concentration at a certain temperature. It is used to measure the activity of the initiator or the reaction rate. The term "t 1 / 2 =0.1h" means that the time required for the initiator to decompose to half of the initial concentration at a certain temperature is 0.1h, and the above temperature is called the decomposition temperature of the initiator. That is, the decomposition temperature in this application is the temperature corresponding to the half-life of the initiator is 0.1h.

[0016] In this application, the term "polar polymer" refers to other polymer materials with permanent dipole properties, excluding PVDF, such as at least one of polyamide (PA), polycarbonate (PC), and polyethylene terephthalate (PET).

[0017] In some optional embodiments, the weight percentage of the compounded initiator in the mixture is 0.1% to 0.5%, which ensures the quality and performance of the grafted product. If the mass concentration of the compounded initiator is too high, the probability of free radical collisions increases, leading to more side reactions, increasing the crosslinking degree of the grafted product and reducing the grafting rate. Conversely, if the mass concentration of the compounded initiator is too low, the polymerization reaction rate is slow, which also leads to a reduced grafting rate.

[0018] Exemplarily, the first initiator can be, for example, dicumyl peroxide (DCP, 1 / 2 = 0.1h when the corresponding decomposition temperature is 150±5℃), di-tert-butyl peroxide (DTBP, t 1 / 2 =0.1h when the corresponding decomposition temperature is 160±5℃), benzoyl peroxide (BPO, t 1 / 2 =0.1h when the corresponding decomposition temperature is 115±5°C); the second initiator can be, for example, dimethyl azobisisobutyrate (AIBME, t 1 / 2 = 0.1h when the corresponding decomposition temperature is 100 ± 5 ° C), azobisisobutyronitrile (AIBN, t 1 / 2 =0.1h when the corresponding decomposition temperature is 100±5°C).

[0019] In some optional embodiments, the modified monomer includes sodium α-olefin sulfonate, and the mass proportion of the sodium α-olefin sulfonate in the mixed material is 5% to 10%. Sodium α-olefin sulfonate uses the olefin group in its chemical structure to graft onto the main chain of PVDF. At the same time, the sulfonic acid group can form hydrogen bonds with the polar groups in the polar polymer, thereby improving the interfacial compatibility between the polar polymer and PVDF. If the amount of modified monomer used is too small, the improvement effect on the interfacial compatibility of the composite material is not obvious. Conversely, if the amount of modified monomer used is too large, a large amount of monomer will remain, affecting product quality.

[0020] For example, the sodium α-olefin sulfonate may be at least one of sodium methyl propylene sulfonate (SMAS), sodium propylene sulfonate, and sodium ethylene sulfonate.

[0021] In some optional embodiments, the mass ratio of the polar polymer to the PVDF is 1 to 3:2. The polar polymer has poor resistance to hydrolysis, while PVDF is resistant to hydrolysis. By compounding the two, the composite material can have better resistance to hydrolysis and oil and gas barrier capabilities.

[0022] Exemplarily, the polar polymer includes at least one of polyamide (PA), polycarbonate (PC), and polyethylene terephthalate (PET). Specifically, the polyamide can be at least one of PA6, PA66, PA46, PA56, PA612, PA610, PA1010, PA12, PA1212, PA1012, PA11, PA510, PA512, PA6T, PA5T, PA9T, PA10T, PA11T, PA12T, PA61, MXD6, MXD10, PPTA, and aramid 1313. The present application adopts a combination of a composite initiation system and a segmented temperature control technology to significantly increase the free radical concentration and activity time, improve the grafting rate, and be compatible with different brands of PA, achieving better melt grafting to improve interfacial compatibility.

[0023] In some optional embodiments, the weight-average molecular weight of the PVDF is 200,000 to 400,000, thereby ensuring appropriate melt viscosity and strength, thereby ensuring product quality and performance. If the molecular weight of the PVDF is too large, the melt viscosity and strength are too high, making it unsuitable for extruder operation. When the molecular weight of the PVDF is too small, the melt viscosity and strength are correspondingly too low, resulting in low strength of the final product, affecting product performance.

[0024] In some optional embodiments, the mixture of S1 further includes a stabilizer, wherein the stabilizer accounts for 0.1% to 0.45% by mass of the mixture. Thus, the acidic substances produced as by-products of the grafting reaction can be consumed by acid-base neutralization to promote the smooth progress of the grafting reaction, while preventing the decomposition of the polymer under acidic catalysis and free radical capture, thereby reducing the ineffective termination of free radicals. If the amount of stabilizer used is too large, a large amount of stabilizer will remain in the PVDF / polar polymer composite material, thereby affecting the strength and apparent properties of the composite material.

[0025] Exemplarily, the stabilizer includes at least one of urea, calcium carbonate, and sodium carbonate.

[0026] In some optional embodiments, the reaction time in S2 is 5 to 10 minutes to ensure an appropriate grafting rate. If the grafting reaction time is too long, it will lead to excessive crosslinking, affecting product quality and further reducing processing performance and toughness. Conversely, if the reaction time is too short, the grafting rate will be affected, which is not conducive to improving the interfacial compatibility of the composite material.

[0027] In some optional embodiments, the extruder may be a twin-screw extruder, which can achieve continuous production and make it possible to expand the application of PVDF.

[0028] According to an embodiment of the present application, in a second aspect, a PVDF / polar polymer composite material prepared by the method described in the first aspect is provided.

[0029] In some optional embodiments, the polyvinylidene fluoride / polar polymer composite material is a PVDF / PA composite material or a PVDF / PC composite material.

[0030] In some optional embodiments, the grafting rate of the polyvinylidene fluoride / polar polymer composite material is not less than 5.3%, thereby effectively improving the interfacial compatibility between PVDF and the polar polymer.

[0031] In some optional embodiments, the peeling force between the polyvinylidene fluoride / polar polymer composite material and the polar polymer is not less than 4.2 N / 15 mm.

[0032] In some optional embodiments, the water contact angle of the polyvinylidene fluoride / polar polymer composite material is no greater than 81.4°.

[0033] The technical solution of this application has the following advantages:

[0034] The preparation method of the PVDF / polar polymer composite material provided in the present application is to adjust the decomposition temperature (t 1 / 2 =0.1h) not less than 110℃ first initiator and decomposition temperature (t 1 / 2 =0.1h) and a second initiator with a temperature less than 110°C are compounded in a certain proportion, so that the compounded initiator slowly decomposes in the first zone (i.e., the low-temperature zone) of the extruder to generate primary free radicals, and then initiates the rapid grafting of the modified monomer in the second zone (i.e., the high-temperature zone), significantly improving the free radical concentration and activity time, reducing the activation energy of the grafting reaction, achieving controllable grafting of the modified monomer on PVDF, and improving the grafting rate, thereby effectively improving the interfacial compatibility problem between PVDF and polar polymers.

[0035] Additional aspects and advantages of the embodiments of the present application will be described and shown in part in the subsequent description, or explained through the implementation of the embodiments of the present application. DETAILED DESCRIPTION

[0036] The following is a clear and complete description of the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0037] In the following examples and comparative examples, if no specific experimental steps or conditions are specified, the experiments were carried out according to the conventional experimental steps or conditions described in the literature in the field. The reagents or instruments used, if the manufacturer is not specified, are all commercially available conventional reagents.

[0038] Sources of main raw materials:

[0039] PVDF is produced by Wanhua itself;

[0040] PA is produced by Wanhua;

[0041] SMAS Maclean analytical grade;

[0042] Urea was of analytical grade from Inokane;

[0043] DCP was analytically pure from Inokane;

[0044] AIBN Aladdin analytical grade;

[0045] AIBME Aladdin analytical grade;

[0046] BPO Inotech analytical grade;

[0047] DTBP was analytically pure from Inotech;

[0048] Sodium vinyl sulfonate was of Maclean analytical grade.

[0049] Example 1

[0050] The method for preparing the PVDF / PA composite material in this embodiment includes the following steps:

[0051] S1, PVDF (molecular weight 300000), modified monomer SMAS, compound initiator, urea, and PA were mixed in the proportions shown in Table 1;

[0052] Table 1

[0053]

[0054]

[0055] S2. Turn on the twin-screw extruder and set the required parameters: feeding section 170°C, first zone (low-temperature grafting section) 180°C, second zone (high-temperature grafting section) 210°C, discharge section 190°C; after the parameters of the twin-screw extruder reach the set values, place the blend in the discharge barrel and control the mixture to stay in the screw for 8 minutes by adjusting the speed to 50 rpm;

[0056] S3. Obtain a reaction product by water-cooled strand granulation, and dry the reaction product in an oven at 80° C. for 24 h to obtain the target product, PVDF / PA composite material.

[0057] Example 2

[0058] The process is basically the same as Example 1, except for the amount of each raw material used. Please see Table 2 for details.

[0059] Table 2

[0060] PVDF PA SMAS urea DCP AIBN Dosage (g) 800 1200 200 10 6.65 3.35 Mass ratio 9％ 0.45％ 0.30％ 0.15％

[0061] Example 3

[0062] The process is basically the same as Example 1, except for the amount of each raw material used. Please see Table 3 for details.

[0063] Table 3

[0064] PVDF PA SMAS urea DCP AIBN Dosage (g) 800 1200 200 10 7.5 2.5 Mass ratio 9％ 0.45％ 0.34％ 0.11％

[0065] Example 4

[0066] The method for preparing the PVDF / PA composite material in this embodiment includes the following steps:

[0067] S1. PVDF (molecular weight 400,000), modified monomer SMAS, compound initiator, urea, and PA were mixed in the proportions shown in Table 4;

[0068] Table 4

[0069]

[0070]

[0071] S2. Turn on the twin-screw extruder and set the required parameters: feeding section 175°C, first zone (low-temperature grafting section) 185°C, second zone (high-temperature grafting section) 205°C, discharge section 195°C; after the parameters of the twin-screw extruder reach the set values, place the blend in the discharge barrel and control the residence time of the mixture in the screw for 5 minutes by adjusting the speed to 100 rpm;

[0072] S3. Obtain a reaction product by water-cooled strand granulation, and dry the reaction product in an oven at 80° C. for 24 h to obtain the target product, PVDF / PA composite material.

[0073] Example 5

[0074] The method for preparing the PVDF / PA composite material in this embodiment includes the following steps:

[0075] S1. PVDF (molecular weight 200,000), modified monomer SMAS, compound initiator, urea, and PA were mixed in the proportions shown in Table 5;

[0076] Table 5

[0077] PVDF PA SMAS urea DTBP AIBME Dosage (g) 800 1200 222 2.5 5 2.5 Mass ratio 10％ 0.1％ 0.2％ 0.1％

[0078] S2. Turn on the twin-screw extruder and set the required parameters: feeding section 165°C, first zone (low-temperature grafting section) 180°C, second zone (high-temperature grafting section) 215°C, discharge section 185°C; after the parameters of the twin-screw extruder reach the set values, place the blend in the discharge barrel and control the mixture to stay in the screw for 10 minutes by adjusting the speed to 30 rpm;

[0079] S3. Obtain a reaction product by water-cooled strand granulation, and dry the reaction product in an oven at 80° C. for 24 h to obtain the target product, PVDF / PA composite material.

[0080] Example 6

[0081] The method for preparing the PVDF / PA composite material in this embodiment includes the following steps:

[0082] S1. PVDF (molecular weight 300,000), modified monomer SMAS, compound initiator, urea, and PA were mixed in the proportions shown in Table 6;

[0083] Table 6

[0084]

[0085]

[0086] S2. Turn on the twin-screw extruder and set the required parameters: feeding section 170°C, first zone (low-temperature grafting section) 175°C, second zone (high-temperature grafting section) 210°C, discharge section 190°C; after the parameters of the twin-screw extruder reach the set values, place the blend in the discharge barrel and control the residence time of the mixture in the screw for 8 minutes by adjusting the speed to 50 rpm;

[0087] S3. Obtain a reaction product by water-cooled strand granulation, and dry the reaction product in an oven at 80° C. for 24 h to obtain the target product, PVDF / PA composite material.

[0088] Example 7

[0089] The method for preparing the PVDF / PC composite material in this embodiment includes the following steps:

[0090] S1. PVDF (molecular weight 350,000), modified monomer sodium vinyl sulfonate, composite initiator, NaCO3, and PC were mixed in the proportions shown in Table 7;

[0091] Table 7

[0092] PVDF PC monomer <![CDATA[NaCO3]]> DCP AIBME Dosage (g) 1347 673 180 10 6.65 3.35 Mass ratio 8.1％ 0.45％ 0.30％ 0.15％

[0093] S2. Turn on the twin-screw extruder and set the required parameters: feeding section 165°C, first zone (low-temperature grafting section) 180°C, second zone (high-temperature grafting section) 215°C, discharge section 185°C; after the parameters of the twin-screw extruder reach the set values, place the blend in the discharge barrel and control the mixture to stay in the screw for 10 minutes by adjusting the speed to 30 rpm;

[0094] S3. Obtain a reaction product by water-cooled strand granulation, and dry the reaction product in an oven at 80° C. for 24 h to obtain the target product, PVDF / PC composite material.

[0095] Example 8

[0096] The process is basically the same as Example 2, except for the amount of each raw material used. Please see Table 8 for details.

[0097] Table 8

[0098] PVDF PA SMAS urea DCP AIBN Dosage (g) 800 1200 196.68 10 8.88 4.44 Mass ratio 8.9％ 0.45％ 0.4％ 0.2％

[0099] Example 9

[0100] The process is basically the same as Example 2, except for the amount of each raw material used. Please see Table 9 for details.

[0101] Table 9

[0102] PVDF PA SMAS DCP AIBN Dosage (g) 800 1200 210 6.65 3.35 Mass ratio 9.5％ 0.30％ 0.15％

[0103] Example 10

[0104] The process is basically the same as Example 2, except for the amount of each raw material used. Please see Table 10 for details.

[0105] Table 10

[0106] PVDF PA SMAS urea DCP AIBN Dosage (g) 774 1160 266 10 6.65 3.35 Mass ratio 12％ 0.45％ 0.30％ 0.15％

[0107] Comparative Example 1

[0108] The PVDF / PA composites were prepared as follows:

[0109] S1, 800g PVDF (molecular weight 300000) and 1200g PA were mixed;

[0110] S2. Turn on the twin-screw extruder and set the required parameters: feeding section 170°C, first zone (low temperature section) 180°C, second zone (high temperature section) 210°C, discharge section 190°C; after the parameters of the twin-screw extruder reach the set values, place the blend in the discharge barrel and control the residence time of the mixture in the screw to 8 minutes by adjusting the speed to 50 rpm;

[0111] S3. A blend is obtained by water-cooled strand granulation, and the blend is dried in an oven at 80° C. for 24 h to obtain the target product, PVDF / PA composite material.

[0112] Comparative Example 2

[0113] The PVDF / PA composites were prepared as follows:

[0114] S1. PVDF (molecular weight 300,000), modified monomer SMAS, initiator AIBN, urea, and PA were mixed in the proportions shown in Table 11;

[0115] Table 11

[0116]

[0117]

[0118] S2. Turn on the twin-screw extruder and set the required parameters: feeding section 170°C, grafting section 180°C, discharge section 190°C; after the parameters of the twin-screw extruder reach the set values, place the blend into the discharge barrel and adjust the speed to 50 rpm to control the mixture to stay in the screw for 8 minutes;

[0119] S3. Obtain a reaction product by water-cooled strand granulation, and dry the reaction product in an oven at 80° C. for 24 h to obtain the target product, PVDF / PA composite material.

[0120] Comparative Example 3

[0121] The PVDF / PA composites were prepared as follows:

[0122] S1. PVDF (molecular weight 300,000), modified monomer SMAS, initiator DCP, urea, and PA were mixed in the proportions shown in Table 12;

[0123] Table 12

[0124] PVDF PA SMAS urea DCP Dosage (g) 800 1200 200 10 10 Mass ratio 9％ 0.45％ 0.45％

[0125] S2. Turn on the twin-screw extruder and set the required parameters: feeding section 170°C, grafting section 210°C, discharge section 190°C; after the parameters of the twin-screw extruder reach the set values, place the blend into the discharge barrel and adjust the speed to 50 rpm to control the mixture to stay in the screw for 8 minutes;

[0126] S3. Obtain a reaction product by water-cooled strand granulation, and dry the reaction product in an oven at 80° C. for 24 h to obtain the target product, PVDF / PA composite material.

[0127] Comparative Example 4

[0128] The PVDF / PA composites were prepared as follows:

[0129] S1. PVDF (molecular weight 300,000), modified monomer SMAS, compound initiator, urea, and PA were mixed in the proportions shown in Table 13;

[0130] Table 13

[0131] PVDF PA SMAS urea DCP AIBN Dosage (g) 800 1200 200 10 8 2 Mass ratio 9％ 0.45％ 0.36％ 0.09％

[0132] S2. Turn on the twin-screw extruder and set the required parameters: feeding section 170°C, first zone (low-temperature grafting section) 180°C, second zone (high-temperature grafting section) 210°C, discharge section 190°C; after the parameters of the twin-screw extruder reach the set values, place the blend in the discharge barrel and control the mixture to stay in the screw for 8 minutes by adjusting the speed to 50 rpm;

[0133] S3. Obtain a reaction product by water-cooled strand granulation, and dry the reaction product in an oven at 80° C. for 24 h to obtain the target product, PVDF / PA composite material.

[0134] Comparative Example 5

[0135] The PVDF / PA composites were prepared as follows:

[0136] S1. PVDF (molecular weight 300,000), modified monomer SMAS, compound initiator, urea, and PA were mixed in the proportions shown in Table 14;

[0137] Table 14

[0138] PVDF PA SMAS urea DCP BPO Dosage (g) 800 1200 200 10 5 5 Mass ratio 9％ 0.45％ 0.225％ 0.225％

[0139] S2. Turn on the twin-screw extruder and set the required parameters: feeding section 170°C, low-temperature grafting section 180°C, high-temperature grafting section 210°C, and discharge section 190°C; after the parameters of the twin-screw extruder reach the set values, place the blend in the discharge barrel and control the residence time of the mixture in the screw for 8 minutes by adjusting the speed to 50 rpm;

[0140] S3. Obtain a reaction product by water-cooled strand granulation, and dry the reaction product in an oven at 80° C. for 24 h to obtain the target product, PVDF / PA composite material.

[0141] Comparative Example 6

[0142] The process is basically the same as Example 1, except that maleic anhydride of equal mass is used instead of SMAS.

[0143] Test Case

[0144] Grafting rate test: Place the PVDF / polar polymer composite material in DMSO solution and dissolve it in an 80℃ oven for 8h. Pour the liquid into a nuclear magnetic tube with a liquid level of 4-5cm. Test the sample. 1 H spectrum, 13 C spectrum, and the grafting rate was calculated by the area ratio of its characteristic peaks.

[0145] Water contact angle test: Place the PVDF / polar polymer film in a flat vulcanizer and press it into a sheet at 200°C for 10 minutes. The sheet thickness is 0.1-0.3mm. Cut a 50mm×50mm square specimen and use a German OCA20 surface contact angle tester for testing. Under ambient temperature and humidity, measure the static contact angle of water at different positions on the film surface. The droplet volume is 3μl, and the arithmetic average of at least 5 reading points is taken.

[0146] Peel Strength Test: PVDF / PA film and PA substrate were laminated in a flatbed vulcanizer and pressed at 200°C for 10 minutes. The sheet thickness was 0.1-0.3mm. The two-layer composite material was cut into a standard size of 15mm x 150mm. The PVDF / PA film and PA substrate were pre-peeled 50mm along the length of the specimen. The specimen was then mounted on a ZWICK 54 universal testing machine and the peel speed was set at 50mm / min. T-peel strength was measured. For PVDF / PC film, the test was performed after lamination with the PC substrate.

[0147] Tensile Strength Test: Prepare PVDF / polar polymer film tensile specimens 150 mm long, 10.0 ± 0.2 mm wide, and 4.0 ± 0.2 mm thick according to the test standard. Test using a universal electronic tensile testing machine. The test temperature is 23°C ± 2°C, the tensile speed is 20 ± 1 mm / min, the specimen clamping distance is 40.00 mm, and the upper and lower clamps are placed symmetrically. Clamp the specimen in the clamps of the tensile testing machine, ensuring that the longitudinal axis of the specimen coincides with the centerline of the clamps. Start the testing machine and stretch at the set speed until the specimen breaks. Record the maximum tensile strength at the time of fracture.

[0148] Please see Table 15 for the above test results, where “ / ” indicates that the content does not exist.

[0149] Table 15

[0150]

[0151]

[0152] As can be seen from Table 15, compared to Comparative Examples 1-5, the grafting rate of the PVDF / polar polymer composites produced in all Examples was significantly improved, resulting in improved hydrophilicity and increased peel force between the PVDF / polar polymer film and the substrate, indicating good interfacial compatibility between PVDF and the polar polymer. Furthermore, the PVDF / polar polymer composites produced in this application also possess excellent mechanical strength, meeting the needs of applications such as oil and gas isolation and pipeline transportation.

[0153] Comparative Examples 1-3 show that when the mass ratio of the first initiator to the second initiator is 2:1, the grafting rate of the composite material is the highest, the hydrophilicity is correspondingly the best, and the peeling force between the PVDF / PA film and the PA substrate is the largest.

[0154] In Comparative Example 1, PVDF and PA were directly mixed and extruded. Due to the lack of grafting modification, the hydrophilicity of the PVDF / PA composite decreased. In Comparative Example 2, only AIBN was used as the initiator; in Comparative Example 3, only DCP was used as the initiator; in Comparative Example 4, DCP and AIBN were used in a 4:1 mass ratio; and in Comparative Example 5, DCP and BPO were used in a 1:1 mass ratio. All of these resulted in decreased grafting efficiency, poorer hydrophilicity, and reduced peel strength. In Comparative Example 6, maleic anhydride was used instead of SMAS as the modifying monomer, which affected the hydrophilicity and peel strength of the PVDF / PA composite.

[0155] It should be noted that there is no adhesion between the PVDF / PA film prepared in Comparative Example 1 and the PA substrate, and the film separates when pulled during testing on a machine. Therefore, the peeling force data of Comparative Example 1 in Table 15 is shown as " / ".

[0156] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of this application.

Claims

1. A method for preparing a polyvinylidene fluoride / polar polymer composite material, characterized in that: The steps include: S1. mixing a polar polymer, polyvinylidene fluoride, a modified monomer and a compound initiator to form a mixed material; Wherein, the composite initiator comprises a first initiator and a second initiator in a mass ratio of 1 to 3:1, and the decomposition temperature T1 (t 1 / 2 =0.1h) is not less than 110°C, the decomposition temperature T2 (t 1 / 2 =0.1h) is less than 110°C; S2, adding the mixture obtained in S1 to an extruder, and reacting in the first zone and the second zone of the extruder in sequence, controlling the reaction temperature of the first zone to be 175° C. to 185° C., and the reaction temperature of the second zone to be 205° C. to 215° C.; S3. Cooling the material obtained in S2, granulating it, and drying it to obtain a polyvinylidene fluoride / polar polymer composite material.

2. The method for preparing the polyvinylidene fluoride / polar polymer composite material according to claim 1, wherein: The mass proportion of the compound initiator in the mixed material is 0.1% to 0.5%; And / or, the first initiator includes at least one of dicumyl peroxide, di-tert-butyl peroxide, and benzoyl peroxide; And / or, the second initiator includes at least one of dimethyl azobisisobutyrate and azobisisobutyronitrile.

3. The method for preparing the polyvinylidene fluoride / polar polymer composite material according to claim 1 or 2, characterized in that: The modified monomer includes sodium α-olefin sulfonate, and the mass proportion of the sodium α-olefin sulfonate in the mixed material is 5% to 10%; And / or, the sodium α-olefin sulfonate includes at least one of sodium methacrylate sulfonate, sodium propylene sulfonate, and sodium ethylene sulfonate.

4. The method for preparing the polyvinylidene fluoride / polar polymer composite material according to claim 1 or 2, characterized in that: The mass ratio of the polar polymer to polyvinylidene fluoride is 1 to 3:2; And / or, the polar polymer includes at least one of polyamide, polycarbonate, and polyethylene terephthalate; And / or, the weight average molecular weight of the polyvinylidene fluoride is 200,000 to 400,000.

5. The method for preparing the polyvinylidene fluoride / polar polymer composite material according to claim 1 or 2, characterized in that: The mixed material of S1 further includes a stabilizer, and the mass proportion of the stabilizer in the mixed material is 0.1% to 0.45%; And / or, the stabilizer includes at least one of urea, calcium carbonate, and sodium carbonate.

6. The method for preparing the polyvinylidene fluoride / polar polymer composite material according to claim 1, characterized in that: The reaction time in S2 is 5 to 10 minutes.

7. A polyvinylidene fluoride / polar polymer composite material prepared by the method according to any one of claims 1 to 6.

8. The polyvinylidene fluoride / polar polymer composite material according to claim 7, characterized in that: The polyvinylidene fluoride / polar polymer composite material is a polyvinylidene fluoride / polyamide composite material or a polyvinylidene fluoride / polycarbonate composite material.

9. The polyvinylidene fluoride / polar polymer composite material according to claim 8, characterized in that: The grafting rate of the polyvinylidene fluoride / polar polymer composite material is not less than 5.3%.

10. The polyvinylidene fluoride / polar polymer composite material according to claim 8 or 9, characterized in that: The peeling force between the polyvinylidene fluoride / polar polymer composite material and the polar polymer is not less than 4.2N / 15mm; And / or, the water contact angle of the polyvinylidene fluoride / polar polymer composite material is no greater than 81.4°.

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