Polymer nanosheet material and method of preparation

Abstract

The application relates to the technical field of high polymer materials, and particularly relates to a polymer nanosheet material and a preparation method thereof. The polymer nanosheet material comprises a base polymer and polymer nanosheets, and the polymer nanosheets are uniformly distributed in the base polymer; the polymer nanosheets account for 5-30 wt% of the blend; the polymer nanosheets are at least one of nylon 6, polyethylene terephthalate, polycarbonate and polymethyl methacrylate; and the base polymer is polyethylene, isotactic polypropylene or random polystyrene. The polymer nanosheet material and the preparation method thereof are prepared by a low-cost and high-efficiency extruder, the polymer nanosheets are uniformly distributed in the base polymer, have various morphologies, the prepared polymer nanosheets can provide nucleation sites for the crystallization of the base polymer, a good interfacial crystallization structure is formed, and the polymer nanosheet material has high mechanical properties.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer materials, and particularly relates to a polymer nanosheet material and a preparation method. BACKGROUND

[0002] In a common polymer / filler system, fillers can be divided into three types according to their morphology: one-dimensional fillers such as carbon nanotubes, glass fibers and other fibrous fillers; two-dimensional fillers such as graphene, boron nitride, montmorillonite and mica; and three-dimensional fillers such as carbon black and silicon dioxide. According to the differences in the morphology of fillers, products with different performance requirements can be prepared, for example, the tensile strength of a substrate in the orientation direction is significantly improved when one-dimensional fillers are added to the substrate, two-dimensional materials can be used to prepare heat-conducting and barrier materials after being added to the substrate, and the impact strength of the substrate can be improved by adding three-dimensional materials. For a polymer mixture, current research mainly focuses on systems in which the morphology of the dispersed phase is spherical or fibrous, that is, one-dimensional and three-dimensional morphologies of the dispersed phase; the lack of two-dimensional sheet-like polymer reinforcing phases when the polymer is used as a dispersed phase limits the performance improvement of products in terms of reinforcement and barrier materials, and cannot meet market demand.

[0003] In an incompatible polymer mixture, the morphology of the dispersed phase is generally spherical or ellipsoidal, and the structure is island-like. Studies have shown that the morphology of the dispersed phase can be changed from spherical to fibrous or sheet-like through the action of a special external field, which can improve the interfacial interaction with the substrate and improve the performance of the product. The currently reported methods for preparing two-dimensional polymer nanosheets mainly include in-situ fiber formation followed by high-temperature and high-pressure method, electrochemical exfoliation method and soft-template oxidation polymerization.

[0004] Shields et al. obtained plate-like, cigar-like and micro-fibrous PET in a PE / PET mixture by controlling the external field (SHIELDS R J et al. Composites Part A Applied Science & Manufacturing, 39 (2008): 940-949.). However, the thickness of the PET plate prepared in this process is obviously in the micron level, and the performance improvement of the substrate is very limited.

[0005] Xie et al. prepared degradable nanolayered polybutylene succinate (PBS) in a PLA / PBS in-situ nanofiber composite material in a PLA film (Xie, Lan, et al. ACS Applied Materials & Interfaces, 7 (2015): 8023-8032.).

[0006] Xu in the preparation of PLA / PBS microfiber mixture, by applying 10 MPa high pressure at 160 ℃ to complete the transformation of PBS fiber to PBS nanosheet; but this method is discontinuous, not conducive to large-scale preparation.

[0007] Xu Zhi strategy, etc. reported a two-dimensional polymer wrapped around the conductive metal wire as the working electrode, by applying a selected voltage, and then stripping from the two-dimensional polymer to obtain two-dimensional polymer nanosheet material, such as a two-dimensional polymer nanosheet material electrochemical exfoliation method and two-dimensional polymer nanosheet material disclosed in Chinese patent (CN114316295A); but the preparation method selected is carried out in solution, there are high cost, low yield, environmental pollution and other problems;

[0008] In summary, most of the reported preparation of polymer nanosheet material is carried out in solution, and the existing melt processing forming method is also a non-continuous preparation, multiple high-temperature melt processing is not conducive to the performance of the material itself and future large-scale production. SUMMARY

[0009] Therefore, it is necessary to provide a polymer nanosheet material and a preparation method for solving the technical problems raised in the background art.

[0010] In order to solve the above technical problems, the present application adopts the following technical scheme:

[0011] A polymer nanosheet material, comprising a base polymer and a polymer nanosheet, the inside of the base polymer uniformly distributed with polymer nanosheets.

[0012] As a preferred embodiment of the polymer nanosheet material provided by the present application, the polymer nanosheet accounts for 5-30wt% of the blend.

[0013] As a preferred embodiment of the polymer nanosheet material provided by the present application, the polymer nanosheet is at least one of nylon 6, polyethylene terephthalate, polycarbonate, and polymethyl methacrylate.

[0014] As a preferred embodiment of the polymer nanosheet material provided by the present application, the base polymer is polyethylene or isotactic polypropylene or random polystyrene.

[0015] A preparation method of a polymer nanosheet material, for any one of the above, the steps are as follows:

[0016] S1: mixing high-density polyethylene and polycaprolactam in a mass ratio of 9:1 to form a mixture;

[0017] S2: the mixture prepared in S1 is obtained into PA6 nanosheets by methods of extrusion, hot stretching, roller pressing and air cooling.

[0018] As a preferred embodiment of the preparation method of the polymer nanosheet material, in S1, the mixture is prepared by melt blending of a twin-screw extruder, the rotation speed of the screw is 180 r / min, and the temperature from the barrel to the die is 140, 180, 220, 250, 250 and 240 DEG C respectively; and the granulation by a granulator is performed to ensure sufficient drying.

[0019] As a preferred embodiment of the preparation method of the polymer nanosheet material, the extrusion is performed by a single-screw extruder.

[0020] The hot stretching is achieved by the difference between the extrusion speed of the single-screw extruder and the collection speed of the winding device.

[0021] The roller pressing is performed by extruding the extrudate through a three-roller winding device.

[0022] The air cooling is performed by rapidly cooling the nanosheet blend after the roller pressing in an air knife.

[0023] As a preferred embodiment of the preparation method of the polymer nanosheet material, the extrusion of the prepared mixture by a single-screw extruder is performed as follows:

[0024] The die size of the single-screw extrusion is 2 mm in thickness and 30 mm in width, the plasticizing temperature is 245 DEG C, and the rotation speed of the screw is 30 r / min.

[0025] As a preferred embodiment of the preparation method of the polymer nanosheet material, the hot stretching is achieved by the difference between the extrusion speed of the single-screw extruder and the collection speed of the winding device, and the steps are as follows:

[0026] When the winding speed is greater than the screw extrusion speed, an extrusion-hot stretching action field is formed.

[0027] As a preferred embodiment of the preparation method of the polymer nanosheet material, the roller pressing is performed by extruding the extrudate through a three-roller winding device, and the steps are as follows:

[0028] A special pressure field is generated between the upper and lower rollers of the three-roller winding device through which the extrudate passes.

[0029] The distance between the upper and lower rollers is about 300 μm, and the temperature of the rollers is 80 DEG C.

[0030] It can be seen without doubt that the above technical solutions of the application can certainly solve the technical problems to be solved by the application.

[0031] Meanwhile, through the above technical solutions, the application at least has the following beneficial effects:

[0032] The application provides a polymer nanosheet material and a preparation method thereof, and the target polymer nanosheet is prepared in a base polymer at one time through an extrusion-thermal stretching-roller pressing-quenching method; the polymer nanosheet is continuously prepared and uniformly distributed in the base polymer, and the size of the polymer nanosheet can be controlled and the polymer nanosheet has a good interfacial interaction with the base polymer.

[0033] The application provides a simple and continuous method for preparing a polymer nanosheet, the polymer nanosheet is uniformly distributed in a base polymer, has various morphologies, and can provide nucleation sites for crystallization of the base polymer, so that a good interfacial crystallization structure is formed, and the polymer nanosheet material has high mechanical properties.

[0034] The polymer nanosheet is continuously prepared by using an extruder with low cost and high efficiency without using organic reagents and templates.

[0035] The polymer nanosheet has various sizes and morphologies, has a good interfacial interaction with the base polymer, and has good mechanical properties.

[0036] The raw materials of the preparation method are all commercial products and are easy to obtain. DETAILED DESCRIPTION

[0037] In order to more clearly illustrate the technical solutions of the embodiments of the application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0038] Figure 1 The cross-sectional morphology of the polymer nanosheet material prepared by the application is shown in the horizontal direction of the stretching flow direction.

[0039] Figure 2 The morphology of the polymer nanosheet obtained by washing away the base polymer by the application is shown in the horizontal direction of the stretching flow direction.

[0040] Figure 3 The crystallization morphology of the general base polymer material and the polymer nanosheet material prepared by the method of the application is shown in the horizontal direction of the stretching flow direction.

[0041] Figure 4The stress-strain curve of the general base polymer material and the polymer nanosheet material of the present application. DETAILED DESCRIPTION

[0042] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application.

[0043] In order to make the persons skilled in the art better understand the technical solutions of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings.

[0044] It should be noted that the embodiments in the present application and the features and technical solutions in the embodiments can be combined with each other without conflict.

[0045] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0046] Embodiment one

[0047] A polymer nanosheet material, comprising a base polymer and polymer nanosheets, the polymer nanosheets being uniformly distributed in the interior of the base polymer, the polymer nanosheets having a thickness of 100-500 nanometers and a shape of a long strip, containing a single end, multiple ends (similar to petal shape) and various morphologies, being uniformly distributed in the base polymer, the polymer nanosheets accounting for 5-30 wt% of the blend.

[0048] The polymer nanosheets have the ability to induce heterogeneous nucleation, induce the base polymer to form a hybrid lamellar structure through interfacial crystallization on the surface of the target polymer nanosheets, form a good interfacial bonding effect, and the polymer nanosheet material exhibits good mechanical properties.

[0049] The polymer nanosheets are commercial polymer products, and at least one of nylon 6, polyethylene terephthalate, polycarbonate or polymethyl methacrylate is selected.

[0050] The base polymer is one of polyethylene, isotactic polypropylene or random polystyrene.

[0051] Further, the weight average molecular weight of the polymer is between 200,000 and 600,000.

[0052] Embodiment two

[0053] On the basis of the above-mentioned embodiment one, a preparation method thereof is disclosed, and the steps are as follows:

[0054] S1: mixing high-density polyethylene and polycaprolactam in a mass ratio of 9:1 to form a mixture;

[0055] In the S1 step, the high-density polyethylene is (HDPE 6098, weight average relative molecular mass (Mw) is about 1.63*105 g / mol, molecular weight distribution is 4.1, density is 0.930 g / cm 3 , melting point is about 130℃), and the polycaprolactam (PA6 B24, density is about 1.13 g / cm 3 , melting point is about 220℃).

[0056] In the S1 step, the mixture is prepared by a HDPE / PA6 blend prepared by a twin-screw extrusion melt blending, so that the PA6 is directly mixed with the HDPE granules, and then melt blending is realized by a twin screw, the rotation speed of the screw is 180 r / min, and the temperature from the barrel to the die is 140, 180, 220, 250, 250, 240℃ respectively; after granulation by a cutting machine, the next step of the sample preparation is carried out after ensuring sufficient drying;

[0057] In the S2 step, the mixture prepared in the S1 step is obtained by an extrusion, heat stretching, roller pressing and air cooling method to obtain PA6 nanosheets;

[0058] The prepared mixture is extruded by a single-screw extruder, the die size of the single-screw extrusion is 2 mm*30 mm (thickness*width), the plasticizing temperature is 245℃, and the rotation speed of the screw is 30 r / min;

[0059] In other embodiments, the plasticizing temperature is 160-260℃, and the screw speed is controlled at 30-60 r / min.

[0060] The heat stretching is realized by the difference between the extrusion speed of the single-screw extruder and the collection speed of the winding device, and when the winding speed is greater than the screw extrusion speed, an extrusion-heat stretching action field is formed;

[0061] The roller pressing is to extrude the extrudate by a three-roller winding device, and a special pressure field occurs between the upper and lower rollers through which the extrudate passes; the distance between the two rollers is about 300 μm, and the temperature of the rollers is controlled at 80℃;

[0062] In other embodiments, the distance between the two rollers is about 300-1000 μm, and the temperature of the rollers is controlled at 30-80℃.

[0063] The air cooling is to rapidly cool the nanosheet blend after the roller pressing in the air knife.

[0064] Example Three

[0065] Reference Figures 1-4PA6 nanosheets formed by the processing of Example 2 were compared;

[0066] Pure high density polyethylene: the preparation method of Example 2 was adopted, except that PA6 was not added, and "extrusion-heat stretching-rolling-air cooling" was used to form;

[0067] Performance test:

[0068] The cross section of the polymer nanosheet and the crystal morphology, and the mechanical properties of the polymer nanosheet were tested as follows:

[0069] The polymer nanosheet was soaked in liquid nitrogen for 1 h, and then brittle fractured along the stretching flow direction. A scanning electron microscope of Japan JEOL Company JSM-5900LV was used to observe the cross section morphology of the sample, analyze the morphology and distribution of PA6 phase in the HDPE phase, and the acceleration voltage was 20 kV. It can be found from Figure 1 that the PA6 phase in the polyethylene is in the form of sheet, the thickness is in the nanometer level, and is uniformly distributed in the HDPE, and there is no obvious gap at the interface of the two phases.

[0070] Further, the polymer nanosheet sample was etched in a xylene solvent at 140°C for 48 h to remove the HDPE in the mixture. After the etching, the sample was repeatedly cleaned with ethanol and dried at 40°C for 12 h to obtain the morphology of the pure PA6 nanosheet, as shown in Figure 2 .

[0071] The length and width of the PA6 sheet have a large difference, there are single sheets, and there are also "petal-shaped" PA6 sheets containing multiple ends, and the average thickness of the PA6 sheet is about 200-500 nm. Further analysis of the interfacial crystallization between the PA6 nanosheet and the HDPE, the sample to be observed outside the quenched sample in liquid nitrogen was wrapped with a protective material, and then etched in a mixed solution of concentrated sulfuric acid (H2SO4), concentrated nitric acid (HNO3), and potassium permanganate (KMNO4) at a specific temperature, and then sequentially rinsed with dilute sulfuric acid, distilled water, and acetone, and then dried in a vacuum oven for more than 12 h.

[0072] In Figure 3 (a), the typical shish-kebab structure in the pure HDPE sample can be observed. The interfacial crystallization morphology of the PA6 nanosheet and the HDPE is shown in Figure 3 (b), there is highly oriented lamellar growth on both sides of the PA6 nanosheet, forming a hybrid lamellar structure (when the PE amorphous region is etched away by the mixed solution of strong acid, the PA6 phase will also be dissolved by the acid, leaving a hollow. Therefore, the shape of the hollow can be considered as the morphology of the PA6 phase).

[0073] The mechanical properties of the samples were tested using a universal tensile tester (model 5967) from Instron Corporation, USA. The tensile speed was 50 mm / min, and the results are as follows: Figure 4 As shown. From Figure Four It can be observed that the yield strength of pure HDPE material is 79.05 MPa, and the elongation at break is 63.82%. After undergoing a "thermal stretching-compression" field, the molecular chains in the HDPE product undergo a certain degree of orientation, generating a highly oriented crystal structure. This increases the yield strength of the HDPE product along the orientation direction (which is also the tensile direction during mechanical property testing), resulting in a significant decrease in the elongation at break. However, the introduction of PA6 nanosheet material in Example 2 increases the yield strength of HDPE to 87.97 MPa and the elongation at break to 110.57%. Compared with the pure HDPE product prepared under the same conditions, the yield strength is increased by 11%, and the elongation at break is increased by 73%.

[0074] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A polymer nanosheet material, characterized in that, It includes a matrix polymer and polymer nanosheets, wherein the polymer nanosheets are uniformly distributed inside the matrix polymer; The polymer nanosheets are nylon 6; The matrix polymer is polyethylene; The polymer nanosheets are 100-500 nanometers thick and have a long, narrow shape. The polymer nanosheets comprise 5-30 wt% of the blend; High-density polyethylene and polycaprolactam are mixed in a mass ratio of 9:1 to form a mixture; The prepared mixture was processed by extrusion, hot stretching, rolling and air cooling to obtain PA6 nanosheets; Thermal stretching is achieved by the difference between the extrusion speed of a single screw extruder and the collection speed of the winding device. When the winding speed is greater than the screw extrusion speed, an extrusion-thermal stretching action field is formed.

2. A method for preparing the polymer nanosheet material according to claim 1, characterized in that, The steps are as follows: The mixture is formed by melt blending through twin-screw extrusion at a speed of 180 r / min, with temperatures from the barrel to the die being 140, 180, 220, 250, 250, and 240ºC, respectively. The mixture is then granulated using a pelletizer to ensure thorough drying.

3. The method for preparing polymer nanosheet materials according to claim 2, characterized in that, Extrusion refers to the extrusion of the prepared mixture through a single-screw extruder; Roller extrusion is the process of pressing the extruded material through a three-roller winding device. Air cooling is used to rapidly cool the rolled nanosheet blend in an air knife.

4. The method for preparing polymer nanosheet materials according to claim 3, characterized in that, The mixture prepared by extruding it through a single-screw extruder is described in the following steps: The die size for single-screw extrusion is 2mm thick × 30mm wide, the plasticizing temperature is 245ºC, and the screw speed is 30r / min.

5. The method for preparing polymer nanosheet materials according to claim 4, characterized in that, The roller pressing process involves extruding the extrudate through a three-roller winding device, and the steps are as follows: A special pressure field is generated between the upper and lower rollers of the extruder as it passes through the three-roll winding device. The distance between the upper and lower rollers is 300μm, and the roller temperature is 80ºC.

Images