Polypropylene composite material based on graphene modification and preparation method thereof

Abstract

The invention relates to the field of modified polypropylene composite materials, and provides a polypropylene composite material based on graphene modification and a preparation method of the polypropylene composite material in order to solve the problem that the air permeability is poor while the antibacterial filtering performance of the polypropylene composite material is improved. Performing ultrasonic dispersion, filtering and drying to obtain a modified fiber body; adding graphene into the polypropylene melt, and blending to obtain a modified matrix; and dispersing the modified fiber body into the modified matrix, and preparing the polypropylene composite material through a forming process. The graphene is positioned in the airflow channel, so that the gas blocked by the graphene is easily guided to the airflow channel, the blockage of the airflow in the flowing process is reduced, and the air permeability is improved. Due to the fact that the flowing path of most airflow is guided to the airflow channel, and the airflow channel is just the gathering place of the graphene, the sterilization effect of the material in the airflow flowing process can also be improved.

Description

Technical Field

[0001] The present invention relates to the field of modified polypropylene composites, and more particularly, to a graphene-modified polypropylene composite material and a preparation method thereof. Background Art

[0002] Graphene is a two-dimensional material composed of a single layer of carbon atoms closely arranged, with excellent electrical conductivity, thermal conductivity, and mechanical strength. Polypropylene is a commonly used polymer material with excellent chemical corrosion resistance and mechanical properties. Both have broad application prospects in the field of materials, so it is of great significance to study their composites.

[0003] In the prior art, graphene or graphene oxide is often blended with polypropylene materials to obtain composite materials with the advantages of both. However, the addition amount of graphene or graphene oxide affects antibacterial properties and breathability. Under the mutual limitation of antibacterial and breathability, the dosage of graphene is also limited. In the case of requiring strong protective performance, the breathability of composite products will be sacrificed, resulting in a decrease in the comfort of using polypropylene composites. Summary of the Invention

[0004] The purpose of the present invention is to provide a graphene-modified polypropylene composite material and a preparation method thereof, so as to solve the problem of poor breathability of polypropylene composites while improving antibacterial filtration performance.

[0005] The embodiments of the present invention are realized through the following technical solutions:

[0006] A preparation method of a graphene-modified polypropylene composite material includes:

[0007] Adding polypropylene fibers and graphene oxide to deionized water, and obtaining a modified fiber body after ultrasonic dispersion, filtration, and drying;

[0008] Adding graphene to polypropylene melt and blending to obtain a modified matrix;

[0009] Dispersing the modified fiber body in the modified matrix, and obtaining a polypropylene composite material through a forming process;

[0010] The polypropylene fibers have at least hollow channels extending along their axial directions;

[0011] The melting temperature of the modified fiber body is higher than that of the modified matrix.

[0012] Graphene is a two-dimensional material composed of a single layer of carbon atoms closely arranged, with excellent electrical conductivity, thermal conductivity, and mechanical strength. Polypropylene is a commonly used polymer material with excellent chemical corrosion resistance and mechanical properties. Both have broad application prospects in the field of materials, so studying their composites is of great significance.

[0013] In the prior art, graphene or graphene oxide is often blended with polypropylene materials to obtain composite materials with the advantages of both. Hereinafter, graphene or graphene oxide is collectively referred to as graphene. Among them, composite materials utilizing the antibacterial and filtering properties of graphene are widely used in fields such as medical protection, air filtration, furniture products, and industrial adsorption. Currently, the technical difficulty in compounding graphene with polypropylene lies in the relatively high specific surface area of graphene and the strong van der Waals force, which easily leads to agglomeration phenomena. It is difficult to achieve uniform dispersion of graphene in the polymer matrix, which will in turn affect the performance of the final product. The direct binding force between graphene and polypropylene is weak, and the prior art usually modifies graphene to solve the above problems. However, when the modified graphene composite material is used as a medical protection material, its breathability problem will seriously affect the use comfort, such as protective clothing, protective caps, gloves, bedding, examination towels, and nursing pads made of graphene-polypropylene composite materials. When aiming to improve the antibacterial effect, the dosage of graphene should theoretically be increased. However, the increased dosage of graphene will not only affect the breathability of the product but also increase the possibility of graphene agglomeration. Thus, under the mutual restriction of antibacterial property and breathability, the dosage of graphene will also be limited. In the case of requiring strong protection performance, the composite material products will sacrifice a large amount of breathability.

[0014] The applicant expects to improve the air permeability of the material as much as possible while ensuring the material's protective and antibacterial properties. In this invention, hollow polypropylene fibers are used as the carrier of graphene, and graphene adheres to the inner and outer walls of the fibers. Then, the polypropylene fibers are mixed with the polypropylene matrix. Since the compatibility between the two is good, the polypropylene fibers are well dispersed in the matrix, and thus the graphene attached to the polypropylene fibers can also be evenly dispersed in the matrix. Due to the small diameter of the hollow channels of the polypropylene fibers, the matrix melt is difficult to enter the hollow channels, so the hollow structure of the polypropylene fibers can be retained, which can not only reduce the weight of the composite product but also increase the softness and air permeability of the material. Regarding air permeability, since the position of graphene is in the air flow channels, the gas blocked by it is easily guided to the nearby air flow channels, and the resistance during the air flow is greatly reduced, thus increasing the air permeability. Regarding antibacterial properties, since most of the air flow paths are guided to the air flow channels, which are exactly the gathering places of graphene, the bactericidal effect of the material during the air flow can also be improved. To increase the guidance of the air flow, after the polypropylene fibers are attached with graphene oxide, a certain amount of graphene is also mixed in the polypropylene matrix, making the air permeability of the matrix part poor, and thus the air flow tends more towards the hollow channels.

[0015] During the preparation process of the modified matrix, a dispersant or surfactant can be added to improve the dispersion of graphene in the melt, such as polyethylene glycol, sodium dodecyl benzene sulfonate, and polyoxyethylene ether.

[0016] The forming process can adopt extrusion granulation.

[0017] Preferably, graphene oxide and a coupling agent are added to deionized water, and after mixing and reacting, a mixed solution is obtained; after the polypropylene fibers are treated by a radiation process, they are added to the mixed solution, and after reacting for 1 h - 3 h in an ultrasonic environment, the modified fiber body is obtained through filtration, washing, and drying; the dosage of the coupling agent is 1 wt% - 2 wt% of the graphene oxide.

[0018] In order to maintain the morphology of the polypropylene fibers during the forming process, the applicant expects to improve the preparation process of the modified fiber body so that the melting temperature and / or solubility of the modified fiber body are different from those of the modified matrix. For example, the melting temperature of the modified fiber body is higher than that of the modified matrix, or the solubility of the modified fiber body in the solvent is lower than that of the modified matrix. This invention preferentially selects the melting temperature of the modified fiber body being higher than that of the modified matrix as the core of the improvement and regulates the process parameters. At the same time, the bonding degree between graphene oxide and the polypropylene fibers is also improved. To further increase the difference between the modified fiber body and the modified matrix, it can also be achieved by making the polymerization degree and / or crystallinity of the polypropylenes selected for the two different, or by using homopolymers and copolymers respectively.

[0019] The coupling agent can be KH550. Reacting graphene oxide with the coupling agent first and then with polypropylene fibers can improve the dispersibility when graphene oxide reacts with polypropylene fibers.

[0020] Preferably, the time of the radiation process is 20 min - 30 min, the radiation source is cobalt-60γ, and the dose is 5 kGy / h - 20 kGy / h.

[0021] Preferably, the forming process includes: dispersing the modified fiber body in the modified matrix melt, applying an electrostatic field, and cooling to obtain a polypropylene composite material; the length of the modified fiber body is 0.1 mm - 0.3 mm, the thickness of the modified matrix melt is 1.3 times - 1.5 times the length of the modified fiber body; the electric field strength is 800 V / cm - 1500 V / cm, and the direction of the electric field is the thickness direction of the modified matrix melt.

[0022] The amount of graphene oxide used in the modification of polypropylene fibers is also related to the forming process so that the modified fiber bodies can be oriented uniformly under the action of the electric field. When the polypropylene fibers are oriented uniformly and along the thickness direction of the melt, the guiding property of the air flow during the flowing process is stronger, the path is shorter, and the resistance is less, thereby improving the air permeability. At the same time, the mechanical properties of the composite material are also improved.

[0023] When making a film of the polypropylene composite material, the existing melt-stretching method can be used, and unidirectional stretching or bidirectional stretching can be adopted.

[0024] Preferably, after the modified fiber body is dispersed in the modified matrix melt, it flows to the carrier bearing surface in a direction perpendicular to the carrier, the flow rate is 40 m / min - 80 m / min, and the extrusion pressure is 50 Mpa - 100 Mpa.

[0025] The carrier can be a mold, a film substrate, a textile substrate, etc. The carrier can be in a moving state during the process of bearing the melt. The substrate can be separated from the polypropylene composite material at the end of the process or not. For example, a hydrophobic film substrate is used in combination with the polypropylene composite material, and a physical barrier is made through the outer hydrophobic layer, combined with the antibacterial filtration effect of the inner layer to enhance the protection effect. Of course, a skin-friendly innermost layer can also be added to improve the use comfort.

[0026] Due to the certain viscosity of the melt, it is difficult to control the orientation of the fibers in the melt. For example, a higher electric field strength is required, but too high an electric field strength may also affect the morphological stability of part of the modified matrix or the modified fiber body itself. Therefore, the applicant first makes the modified fiber body be preliminarily oriented along the flow direction during the flowing process by controlling the flow rate and extrusion pressure, and then fine-tunes it through the electric field to simplify the control of the orientation process.

[0027] Preferably, the forming process includes: dispersing the modified fiber body in the modified matrix melt, and then preparing a non-woven fabric made of a polypropylene composite material through an electrospinning process; the melt temperature is 160°C - 220°C, and the spinning voltage is 35 kV - 45 kV.

[0028] A polypropylene composite material prepared by the preparation method, in parts by weight, includes: 80 - 100 parts of a polypropylene matrix, 4 - 8 parts of a functional filler, and 20 - 40 parts of polypropylene fibers; the functional filler includes graphene and graphene oxide;

[0029] Part of the graphene oxide is located in the hollow channel.

[0030] The polypropylene matrix refers to the substance obtained after the solidification of the polypropylene melt in the preparation method.

[0031] Preferably, the graphene accounts for 30 wt% - 50 wt% of the functional filler.

[0032] In order to ensure the overall air permeability and antibacterial property of the composite material product, the distribution amounts of graphene oxide and graphene at specific positions are confirmed through experiments, avoiding excessive graphene in the matrix part, which is difficult to disperse. At the same time, relatively less gas passes through the matrix part, which will also reduce the utilization rate of graphene in antibacterial. Too little graphene in the matrix part will reduce the antibacterial property of the matrix.

[0033] Preferably, the polypropylene fiber also has a number of radial through-holes.

[0034] The existence of the radial through-holes can accelerate the dispersion of graphene in the hollow channel and further improve the air permeability.

[0035] Preferably, the length of the polypropylene fiber is 0.1 mm - 3 mm, the pore diameter of the polypropylene fiber is 0.1 μm - 0.5 μm, and the diameter of the polypropylene fiber is 1 μm - 3 μm.

[0036] The present invention has at least the following beneficial effects:

[0037] In the present invention, the hollow polypropylene fiber is used as the carrier of graphene oxide, and graphene oxide adheres to the inner and outer walls of the fiber. Then, the polypropylene fiber is mixed with the polypropylene matrix. Since the compatibility between the two is good, the polypropylene fiber has good dispersibility in the matrix, and thus the graphene oxide attached to the polypropylene fiber can also be evenly dispersed in the matrix.

[0038] Since the diameter of the hollow channel of the polypropylene fiber is very small, it is difficult for the matrix melt to enter the hollow channel. Therefore, the hollow structure of the polypropylene fiber can be retained, which can not only reduce the weight of the composite material product, but also increase the softness and air permeability of the material.

[0039] Regarding breathability, since graphene is located near the air flow channels, the blocked gas is easily guided to the nearest air flow channels, greatly reducing the resistance during the air flow, thus increasing the breathability.

[0040] Regarding antibacterial properties, since the flow paths of most of the air flow are guided to the air flow channels, and the air flow channels happen to be the gathering places of graphene oxide, the bactericidal effect of the material during the air flow can also be improved. In order to increase the guidance of the air flow, after attaching graphene oxide to the polypropylene fibers in the present invention, a certain amount of graphene is also mixed in the polypropylene matrix, making the permeability of the air flow in the matrix part poor, and thus the air flow tends more towards the hollow channels.

[0041] The preparation process of the modified fiber body can not only improve the binding degree of graphene oxide and polypropylene fibers, but also make the heat resistance of the modified fiber body different from that of the modified matrix and the modified fiber body has a certain coating layer, and the morphology of the modified fiber body in the molding process is preserved, thereby realizing the improvement of the breathability and antibacterial properties of the composite material. Specific embodiments

[0042] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention.

[0043] Embodiment 1: A polypropylene composite material, in parts by weight, includes: 80 - 100 parts of a polypropylene matrix, 4 - 8 parts of a functional filler, and 20 - 40 parts of polypropylene fibers; the functional filler includes graphene and graphene oxide;

[0044] The polypropylene fibers have at least hollow channels extending along their axial directions;

[0045] Part of the graphene oxide or graphene is located in the hollow channels.

[0046] In the specific implementation process, the preparation method of the hollow polypropylene fibers is a prior art, which can be prepared by oneself or directly purchase existing products. For the specific preparation method, reference can be made to the patent with the application number 202110101849.8 and the patent name "A hollow polypropylene fiber for non-woven fabrics and its preparation method".

[0047] Embodiment 2: An improvement based on Embodiment 1. In this embodiment, the graphene accounts for 30wt% - 50wt% of the functional filler.

[0048] In the specific implementation process, when calculating the mass percentage, the denominator is the total mass of graphene oxide and graphene.

[0049] Example 3: An improvement is made on the basis of Example 1. In this example, the polypropylene fiber further has a number of radial through-holes.

[0050] During the spinning process, when the polymer solution jet is stretched by an electric field in high-humidity air, the solvent quickly volatilizes, and water vapor in the air condenses on the surface of the jet to form water droplets. After the fiber dries, radial through-holes are formed. The PP spinning solution can use organic solvents such as toluene.

[0051] Example 4: An improvement is made on the basis of Examples 1-3. In this example, the length of the polypropylene fiber is 0.1 mm - 3 mm, the pore diameter of the polypropylene fiber is 0.1 μm - 0.5 μm, and the diameter of the polypropylene fiber is 1 μm - 3 μm.

[0052] In the specific implementation process, when the orientation of the polypropylene fiber is not restricted by the material thickness, the length of the polypropylene fiber can be increased.

[0053] Example 5: A method for preparing a polypropylene composite material, comprising:

[0054] By weight, 20 parts of polypropylene fiber and 70 wt% of graphene oxide are added to 50 parts of deionized water, ultrasonically dispersed for 1 h, filtered, and dried to obtain a modified fiber body;

[0055] The polypropylene fiber has at least a hollow channel extending along its axial direction, the polypropylene fiber further has a number of radial through-holes, the length of the polypropylene fiber is 0.1 mm, the pore diameter of the polypropylene fiber is 0.1 μm, and the diameter of the polypropylene fiber is 1 μm;

[0056] 30 wt% of graphene is added to 80 parts of polypropylene melt and blended to obtain a modified matrix.

[0057] After the modified fiber body is dispersed in the modified matrix, a polypropylene composite material is prepared through a forming process.

[0058] The forming process includes: after the modified fiber body is dispersed in the modified matrix melt, an electrostatic field is applied, and after cooling, a polypropylene composite material is obtained; the thickness of the modified matrix melt is 1.3 times the length of the modified fiber body; the electric field strength is 800 V / cm, and the direction of the electric field is the thickness direction of the modified matrix melt. After the modified fiber body is dispersed in the modified matrix melt, it flows towards the carrier bearing surface in a direction perpendicular to the carrier, with a flow rate of 40 m / min and an extrusion pressure of 50 Mpa.

[0059] Example 6: A method for preparing a polypropylene composite material, comprising:

[0060] By weight, 40 parts of polypropylene fibers and 50 wt% of graphene oxide are added to 50 parts of deionized water, ultrasonically dispersed for 3 h, filtered, and dried to obtain a modified fiber body;

[0061] The polypropylene fibers have at least a hollow channel extending along their axial direction, the polypropylene fibers also have a number of radial through-holes, the length of the polypropylene fibers is 0.3 mm, the pore diameter of the polypropylene fibers is 0.5 μm, and the diameter of the polypropylene fibers is 3 μm;

[0062] 50 wt% of graphene is added to 100 parts of polypropylene melt and blended to obtain a modified matrix.

[0063] After dispersing the modified fiber body in the modified matrix, a polypropylene composite material is prepared by a forming process.

[0064] The forming process includes: after dispersing the modified fiber body in the modified matrix melt, applying an electrostatic field, and cooling to obtain a polypropylene composite material; the thickness of the modified matrix melt is 1.5 times the length of the modified fiber body; the electric field strength is 1500 V / cm, and the direction of the electric field is the thickness direction of the modified matrix melt. After the modified fiber body is dispersed in the modified matrix melt, it flows towards the carrier bearing surface in a direction perpendicular to the carrier at a flow rate of 80 m / min, and the extrusion pressure is 100 Mpa.

[0065] Example 7: A method for preparing a polypropylene composite material, including:

[0066] By weight, 30 parts of polypropylene fibers and 60 wt% of graphene oxide are added to 50 parts of deionized water, ultrasonically dispersed for 2.5 h, filtered, and dried to obtain a modified fiber body;

[0067] The polypropylene fibers have at least a hollow channel extending along their axial direction, the polypropylene fibers also have a number of radial through-holes, the length of the polypropylene fibers is 0.2 mm, the pore diameter of the polypropylene fibers is 0.3 μm, and the diameter of the polypropylene fibers is 1 μm;

[0068] 40 wt% of graphene is added to 90 parts of polypropylene melt and blended to obtain a modified matrix.

[0069] After dispersing the modified fiber body in the modified matrix, a polypropylene composite material is prepared by a forming process.

[0070] The forming process includes: dispersing the modified fiber body in the modified matrix melt, applying an electrostatic field, and cooling to obtain a polypropylene composite material; the thickness of the modified matrix melt is 1.4 times the length of the modified fiber body; the electric field strength is 1200 V / cm, and the direction of the electric field is the thickness direction of the modified matrix melt. After the modified fiber body is dispersed in the modified matrix melt, it flows towards the carrier bearing surface in a direction perpendicular to the carrier, with a flow rate of 60 m / min and an extrusion pressure of 75 Mpa.

[0071] Example 8: A method for preparing a polypropylene composite material, comprising:

[0072] By weight, 60 wt% of graphene oxide and KH550 are added to 50 parts of deionized water, and after mixing and reacting, a mixed solution is obtained; 30 parts of polypropylene fibers are treated by a radiation process and then added to the mixed solution. After reacting for 2.5 h in an ultrasonic environment, the modified fiber body is obtained through filtration, washing, and drying; the dosage of the coupling agent is 1 wt% of graphene oxide. The time of the radiation process is 20 min, the radiation source is cobalt-60γ, and the dose is 5 kGy / h.

[0073] The polypropylene fiber has at least a hollow channel extending along its axial direction, and the polypropylene fiber also has a number of radial through holes. The length of the polypropylene fiber is 0.2 mm, the pore diameter of the polypropylene fiber is 0.3 μm, and the diameter of the polypropylene fiber is 1 μm;

[0074] 40 wt% of graphene is added to 90 parts of polypropylene melt and blended to obtain a modified matrix.

[0075] After dispersing the modified fiber body in the modified matrix, a polypropylene composite material is prepared through a forming process.

[0076] The forming process includes: dispersing the modified fiber body in the modified matrix melt, applying an electrostatic field, and cooling to obtain a polypropylene composite material; the thickness of the modified matrix melt is 1.4 times the length of the modified fiber body; the electric field strength is 1200 V / cm, and the direction of the electric field is the thickness direction of the modified matrix melt. After the modified fiber body is dispersed in the modified matrix melt, it flows towards the carrier bearing surface in a direction perpendicular to the carrier, with a flow rate of 60 m / min and an extrusion pressure of 75 Mpa.

[0077] Example 9: A method for preparing a polypropylene composite material, comprising:

[0078] By weight, 60 wt% graphene oxide and KH550 are added to 50 parts of deionized water, and after mixing and reacting, a mixed solution is obtained; 30 parts of polypropylene fibers are treated by a radiation process and then added to the mixed solution. After reacting for 2.5 h under an ultrasonic environment, the modified fiber body is obtained through filtration, washing, and drying; the dosage of the coupling agent is 2 wt% of the graphene oxide. The time of the radiation process is 30 min, the radiation source is cobalt-60γ, and the dose is 20 kGy / h.

[0079] The polypropylene fiber has at least a hollow channel extending along its axial direction, the polypropylene fiber also has a number of radial through holes, the length of the polypropylene fiber is 0.2 mm, the pore diameter of the polypropylene fiber is 0.3 μm, and the diameter of the polypropylene fiber is 1 μm;

[0080] 40 wt% of graphene is added to 90 parts of polypropylene melt and blended to obtain a modified matrix.

[0081] After the modified fiber body is dispersed in the modified matrix, a polypropylene composite material is prepared through a forming process.

[0082] The forming process includes: after the modified fiber body is dispersed in the modified matrix melt, an electrostatic field is applied, and after cooling, a polypropylene composite material is obtained; the thickness of the modified matrix melt is 1.4 times the length of the modified fiber body; the electric field strength is 1200 V / cm, and the direction of the electric field is the thickness direction of the modified matrix melt. After the modified fiber body is dispersed in the modified matrix melt, it flows towards the carrier bearing surface in a direction perpendicular to the carrier, with a flow rate of 60 m / min and an extrusion pressure of 75 Mpa.

[0083] Example 10: A method for preparing a polypropylene composite material, comprising:

[0084] By weight, 60 wt% graphene oxide and KH550 are added to 50 parts of deionized water, and after mixing and reacting, a mixed solution is obtained; 30 parts of polypropylene fibers are treated by a radiation process and then added to the mixed solution. After reacting for 2.5 h under an ultrasonic environment, the modified fiber body is obtained through filtration, washing, and drying; the dosage of the coupling agent is 1.6 wt% of the graphene oxide. The time of the radiation process is 24 min, the radiation source is cobalt-60γ, and the dose is 10 kGy / h.

[0085] The polypropylene fiber has at least a hollow channel extending along its axial direction, the polypropylene fiber also has a number of radial through holes, the length of the polypropylene fiber is 0.2 mm, the pore diameter of the polypropylene fiber is 0.3 μm, and the diameter of the polypropylene fiber is 1 μm;

[0086] 40 wt% of graphene is added to 90 parts of polypropylene melt and blended to obtain a modified matrix.

[0087] After dispersing the modified fiber body in the modified matrix, a polypropylene composite material is obtained through a forming process.

[0088] The forming process includes: dispersing the modified fiber body in the modified matrix melt, applying an electrostatic field, and obtaining the polypropylene composite material after cooling; the thickness of the modified matrix melt is 1.4 times the length of the modified fiber body; the electric field strength is 1200 V / cm, and the direction of the electric field is the thickness direction of the modified matrix melt. After the modified fiber body is dispersed in the modified matrix melt, it flows towards the carrier bearing surface in a direction perpendicular to the carrier, with a flow rate of 60 m / min and an extrusion pressure of 75 Mpa.

[0089] Example 11: A method for preparing a polypropylene composite material, including:

[0090] By weight, 60 wt% graphene oxide and KH550 are added to 50 parts of deionized water, and after mixing and reacting, a mixed solution is obtained; 30 parts of polypropylene fibers are treated by a radiation process and then added to the mixed solution. After reacting for 2.5 h in an ultrasonic environment, the modified fiber body is obtained through filtration, washing, and drying; the dosage of the coupling agent is 1.6 wt% of the graphene oxide. The time of the radiation process is 24 min, the radiation source is cobalt-60γ, and the dose is 10 kGy / h.

[0091] The polypropylene fiber has at least a hollow channel extending along its axial direction, and the polypropylene fiber also has a number of radial through holes. The length of the polypropylene fiber is 0.2 mm, the pore diameter of the polypropylene fiber is 0.3 μm, and the diameter of the polypropylene fiber is 1 μm;

[0092] 40 wt% of graphene is added to 90 parts of polypropylene melt and blended to obtain a modified matrix.

[0093] After dispersing the modified fiber body in the modified matrix, a polypropylene composite material is obtained through a forming process.

[0094] The forming process includes: dispersing the modified fiber body in the modified matrix melt, and obtaining a non-woven fabric made of the polypropylene composite material through an electrospinning process; the melt temperature is 160 °C, and the spinning voltage is 35 kV.

[0095] Example 12: A method for preparing a polypropylene composite material, including:

[0096] By weight, 60 wt% graphene oxide and KH550 are added to 50 parts of deionized water, and after mixing and reacting, a mixed solution is obtained; 30 parts of polypropylene fibers are treated by a radiation process and then added to the mixed solution. After reacting for 2.5 h under an ultrasonic environment, a modified fiber body is obtained through filtration, washing, and drying; the dosage of the coupling agent is 1.6 wt% of the graphene oxide. The time of the radiation process is 24 min, the radiation source is cobalt-60γ, and the dose is 10 kGy / h.

[0097] The polypropylene fiber has at least a hollow channel extending along its axial direction, and the polypropylene fiber also has a number of radial through holes. The length of the polypropylene fiber is 0.2 mm, the pore diameter of the polypropylene fiber is 0.3 μm, and the diameter of the polypropylene fiber is 1 μm;

[0098] 40 wt% of graphene is added to 90 parts of polypropylene melt and melt-blended to obtain a modified matrix.

[0099] After dispersing the modified fiber body in the modified matrix, a polypropylene composite material is prepared through a forming process.

[0100] The forming process includes: after dispersing the modified fiber body in the modified matrix melt, a non-woven fabric made of a polypropylene composite material is prepared through an electrospinning process; the melt temperature is 220 °C, and the spinning voltage is 45 kV.

[0101] Example 13: A method for preparing a polypropylene composite material, comprising:

[0102] By weight, 60 wt% graphene oxide and KH550 are added to 50 parts of deionized water, and after mixing and reacting, a mixed solution is obtained; 30 parts of polypropylene fibers are treated by a radiation process and then added to the mixed solution. After reacting for 2.5 h under an ultrasonic environment, a modified fiber body is obtained through filtration, washing, and drying; the dosage of the coupling agent is 1.6 wt% of the graphene oxide. The time of the radiation process is 24 min, the radiation source is cobalt-60γ, and the dose is 10 kGy / h.

[0103] The polypropylene fiber has at least a hollow channel extending along its axial direction, and the polypropylene fiber also has a number of radial through holes. The length of the polypropylene fiber is 0.2 mm, the pore diameter of the polypropylene fiber is 0.3 μm, and the diameter of the polypropylene fiber is 1 μm;

[0104] 40 wt% of graphene is added to 90 parts of polypropylene melt and melt-blended to obtain a modified matrix.

[0105] After dispersing the modified fiber body in the modified matrix, a polypropylene composite material is prepared through a forming process.

[0106] The forming process includes: dispersing the modified fiber body in the modified matrix melt, and then obtaining a non-woven fabric made of polypropylene composite material through the electrospinning process; the melt temperature is 170 °C, and the spinning voltage is 40 kV.

[0107] Comparative Example 1: The difference from Example 10 is that the polypropylene fiber is a solid fiber.

[0108] Comparative Example 2: The difference from Example 10 is that after the modified fiber body is dispersed in the modified matrix melt, it is coated on the carrier bearing surface.

[0109] Comparative Example 3: The difference from Example 10 is that no electrostatic field is applied in the forming process.

[0110] Comparative Example 4: The difference from Example 10 is that after the polypropylene fiber is treated by the radiation process, it is added to deionized water together with graphene oxide and coupling agent.

[0111] Comparative Example 5: The difference from Example 10 is that the electric field strength is 2000 V / cm.

[0112] In Examples 5 - 13 and Comparative Examples 1 - 5, the mass percentages of graphene oxide and graphene both refer to their percentages in the functional filler.

[0113] Test 1: The composites prepared by the preparation methods provided in Examples 5 - 13 and Comparative Examples 1 - 5 were subjected to antibacterial property testing (timed exposure method) and air permeability testing (differential pressure method), and the test results are shown in Table 1.

[0114] Table 1

[0115] Example 5 Example 6 Example 7 Example 8 Example 9 Bacteriostatic rate 81.2% 83.4% 83.9% 91.6% 93.7% Air permeability 105 112 120 179 186 Example 10 Example 11 Example 12 Example 13 Comparative example 1 Bacteriostatic rate 94.5% 88.4% 89.1% 89.7% 76.2% Air permeability 192 215 222 229 104 Comparative example 2 Comparative example 3 Comparative example 4 Comparative example 5 Bacteriostatic rate 84.3% 86.8% 86.0% 82.7% Air permeability 164 178 176 161

[0116] The antibacterial rate test was carried out using Escherichia coli. The unit of air permeability is Pa.

[0117] From the test results of Examples 5 - 13, it can be seen that the polypropylene composite material prepared by the preparation method provided by the present invention has good air permeability and antibacterial rate. Among them, on the basis of Example 7, the air permeability of Example 8 has been greatly improved, but the antibacterial rate has also been improved, indicating the importance of improving the preparation process of the modified fiber body.

[0118] From the comparison of the data results between Comparative Example 1 and Example 10, it can be seen that the use of a hollow structure for polypropylene fiber is not only beneficial to the improvement of air permeability but also beneficial to the improvement of antibacterial property.

[0119] From the comparison of the data results between Comparative Examples 2 - 3, Comparative Example 5 and Example 10, it can be seen that the forming process affects the performance of the polypropylene composite material.

[0120] From the comparison of the data results of Comparative Example 4 and Example 10, it can be seen that after graphene oxide reacts with the coupling agent and then reacts with polypropylene fibers, the air permeability and antibacterial properties of the polypropylene composite material can be improved to a certain extent.

[0121] Experiment 2: The composite materials prepared by the preparation methods provided in Examples 5-13 and Comparative Examples 1-5 were subjected to mechanical property tests, and the test results are shown in Table 2.

[0122] Table 2

[0123] Example 5 Example 6 Example 7 Example 8 Example 9 Tensile strength 33.4 34.1 35.3 37.0 37.9 Elongation at break 32.6% 31.5% 33.4% 36.1% 37.0% Example 10 Example 11 Example 12 Example 13 Comparative example 1 Tensile strength 38.6 36.5 36.6 37.1 39.1 Elongation at break 37.8% 40.6% 40.0% 41.3% 36.7% Comparative example 2 Comparative example 3 Comparative example 4 Comparative example 5 Tensile strength 29.5 38.2 30.1 35.7 Elongation at break 32.6% 36.7% 35.4% 36.0%

[0124] The unit of tensile strength is MPa.

[0125] From the data results of Examples 5-13, it can be seen that the polypropylene composite material prepared by the preparation method provided by the present invention has good mechanical properties.

[0126] From the comparison of the data results of Comparative Example 1 and Example 10, it can be seen that the mechanical properties of the polypropylene composite material prepared with hollow polypropylene fibers are comparable to those prepared with solid polypropylene fibers, and the elongation at break has a slight increase.

[0127] From the comparison of the data results of Comparative Examples 2-5 and Example 10, it can be seen that both the forming process and the preparation process of the modified fiber body affect the mechanical properties of the polypropylene composite material.

[0128] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a graphene-modified polypropylene composite material, characterized in that, Comprising: Adding polypropylene fiber and graphene oxide into deionized water, and obtaining a modified fiber body after ultrasonic dispersion, filtration and drying; Adding graphene into a polypropylene melt and blending to obtain a modified matrix; Dispersing the modified fiber body in the modified matrix, and preparing a polypropylene composite material through a forming process; The polypropylene fiber has at least a hollow channel extending along its axial direction; The melting temperature of the modified fiber body is higher than that of the modified matrix.

2. The preparation method according to claim 1, characterized in that, Adding graphene oxide and a coupling agent into deionized water, and obtaining a mixed solution after mixing and reacting; after the polypropylene fiber is treated by a radiation process, adding it into the mixed solution, reacting for 1 h - 3 h under an ultrasonic environment, and obtaining a modified fiber body through filtration, washing and drying; the dosage of the coupling agent is 1 wt% - 2 wt% of the graphene oxide.

3. The preparation method according to claim 2, characterized in that, The time of the radiation process is 20 min - 30 min, the radiation source is cobalt-60γ, and the dose is 5 kGy / h - 20 kGy / h.

4. The preparation method according to claim 2, wherein, The forming process includes: dispersing the modified fiber body in the modified matrix melt, applying an electrostatic field, and obtaining a polypropylene composite material after cooling; the length of the modified fiber body is 0.1 mm - 0.3 mm, the thickness of the modified matrix melt is 1.3 times - 1.5 times the length of the modified fiber body; the electric field strength is 800 V / cm - 1500 V / cm, and the direction of the electric field is the thickness direction of the modified matrix melt.

5. The preparation method according to claim 4, wherein After the modified fiber body is dispersed in the modified matrix melt, it flows to the carrier bearing surface in a direction perpendicular to the carrier, the flow rate is 40 m / min - 80 m / min, and the extrusion pressure is 50 Mpa - 100 Mpa.

6. The preparation method according to any one of claims 1-5, characterized in that, The forming process includes: dispersing the modified fiber body in the modified matrix melt, and preparing a non-woven fabric made of a polypropylene composite material through an electrospinning process; the melt temperature is 160°C - 220°C, and the spinning voltage is 35 kV - 45 kV.

7. A polypropylene composite material prepared by the preparation method according to any one of claims 1-6, characterized in that, By weight, comprising: 80 - 100 parts of a polypropylene matrix, 4 - 8 parts of a functional filler, and 20 - 40 parts of polypropylene fiber; the functional filler includes graphene and graphene oxide; Part of the graphene oxide is located in the hollow channel.

8. The polypropylene composite material according to claim 7, wherein, The graphene accounts for 30 wt% - 50 wt% of the functional filler.

9. The polypropylene composite material according to claim 7, wherein, The polypropylene fiber also has a number of radial through holes.

10. The polypropylene composite material according to any one of claims 7-9, characterized in that The length of the polypropylene fiber is 0.1 mm - 3 mm, the pore diameter of the polypropylene fiber is 0.1 μm - 0.5 μm, and the diameter of the polypropylene fiber is 1 μm - 3 μm.