High-barrier-property high-density polyethylene modified composite material and preparation method thereof

Abstract

The invention relates to a high-barrier-property high-density polyethylene modified composite material and a preparation method thereof, a blend uses HDPE as a matrix, the content of PA6 accounts for 10%-15%, and the content of PE-g-MAH accounts for 10%-15% by weight. The materials are prepared through a double-screw extruder, the temperature, the rotating speed and the vacuum degree in the preparation process are set, and the temperature setting specifically comprises the steps that the temperature of a first area of the temperature of a discharging opening is controlled to range from 180 DEG C to 200 DEG C; the second area to the sixth area are plasticizing sections, and the temperature of the plasticizing sections is controlled to be 230-240 DEG C; the seventh area to the tenth area are shearing sections, and the temperature of the shearing sections is controlled to be 220-230 DEG C. And the rotating speed is set to be 60-70% of the upper rotating speed limit of the experiment machine. The HDPE / PA6 / PE-g-MAH blend prepared by the method provided by the invention has good mechanical properties, thermal properties and gas barrier properties. Specifically, the tensile strength is 18MPa, the elongation at break is 494%, the thermal deformation temperature is 45.9 DEG C, and the helium permeability coefficient is 1.44 * 10 <-13 > cm < 3 >. Cm / cm < 2 >. Pa.s. The modified material has good gas barrier property, and promotes the development of HDPE in the field of IV type gas cylinder research.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen storage materials, and in particular to a high-barrier high-density polyethylene modified composite material and a preparation method thereof. Background Art

[0002] High-density polyethylene is a thermoplastic polymer with the advantages of light weight, wide sources, easy processing and molding, and fatigue resistance. It is widely used in food packaging, electronic appliances, fluid transportation, automobile manufacturing and other fields. In recent years, with the development and utilization of hydrogen energy, the hydrogen fuel cell vehicle industry has developed rapidly, and type IV gas cylinders (plastic liners) as hydrogen storage equipment are becoming a research hotspot around the world. HDPE has excellent mechanical properties, processability and fatigue resistance, and has gradually become the mainstream choice for type IV gas cylinder liner materials. However, the gas barrier properties of high-density polyethylene are poor, which greatly limits its application. Therefore, there is an urgent need to modify the gas barrier properties of high-density polyethylene.

[0003] PA6 is a thermoplastic engineering plastic with good mechanical properties, wear resistance, corrosion resistance, and good processability. It has been widely used in various aspects of life and production. The molecular chain of PA6 contains amide bonds (-NHCO-) ​​and is a polar polymer. 2 , O 2 PA6 has good barrier properties against non-polar gas molecules, and adding PA6 to HDPE can improve the gas barrier properties of HDPE. However, HDPE and PA6 are thermodynamically incompatible systems. Summary of the invention

[0004] According to the technical problems raised above, a high-barrier high-density polyethylene modified composite material and a preparation method thereof are provided.

[0005] The technical means adopted by the present invention are as follows:

[0006] The invention discloses a high-barrier high-density polyethylene modified composite material, which is a ternary blend of HDPE / PA6 / PE-g-MAH with HDPE as the matrix.

[0007] Furthermore, in terms of weight percentage, the blend is based on HDPE, the PA6 content accounts for 10% to 15%, and the PE-g-MAH content accounts for 10% to 15%.

[0008] Furthermore, HDPE and PA6 are firstly mixed uniformly according to a certain proportion, and then the HDPE / PA6 premix particles are uniformly mixed with PE-g-MAH.

[0009] The present invention also discloses a specific preparation method of the high-barrier high-density polyethylene modified composite material, comprising the following steps:

[0010] Mix HDPE and PA6 evenly according to the proportion, and then evenly mix the HDPE / PA6 premix particles with PE-g-MAH;

[0011] The above materials are prepared by a twin-screw extruder, and the temperature, speed and vacuum degree are set during the preparation process.

[0012] Among them, the temperature setting is specifically as follows: the temperature of zone 1 of the feeding port is controlled at 180℃~200℃; zones 2 to 6 are plasticizing sections, and the temperature of the plasticizing sections is controlled at 230℃~240℃; zones 7 to 10 are shearing sections, and the temperature of the shearing sections is controlled at 220℃~230℃.

[0013] Furthermore, the temperature at the die head is generally not less than 240°C.

[0014] Furthermore, the rotation speed is set to 60-70% of the upper limit of the rotation speed of the test machine.

[0015] Furthermore, the vacuum degree of the twin-screw extruder is <-0.09MPa.

[0016] The HDPE / PA6 / PE-g-MAH blend prepared based on the method of the present invention has good gas barrier properties and can be used in Type IV gas cylinders.

[0017] Compared with the prior art, the present invention has the following advantages: the HDPE / PA6 / PE-g-MAH blend prepared by the present invention has good mechanical properties, thermal properties and gas barrier properties. Specifically, the tensile strength is 18MPa, the elongation at break is 494%, the heat deformation temperature is 45.9℃, the helium permeability coefficient is 1.44×10 -13 cm 3 cm / cm 2 ·Pa·s. This modified material has good gas barrier properties and promotes the development of HDPE in the field of Type IV gas cylinder research. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0019] Figure 1 Schematic diagram of the mixing sequence of the ternary blend of the present invention. DETAILED DESCRIPTION

[0020] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0021] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0023] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, the numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be clear that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship. The technology, methods and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be regarded as part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar numbers 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 discussed in subsequent drawings.

[0024] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention: the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0025] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below their position devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0026] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0027] like Figure 1 As shown, the embodiment of the present invention discloses a high-barrier high-density polyethylene modified composite material, with HDPE as the matrix, PA6 content accounting for 10wt% to 15wt%, and PE-g-MAH content accounting for 10wt% to 15wt%. First, HDPE and PA6 are evenly mixed in proportion, and then the HDPE / PA6 premix particles are evenly mixed with PE-g-MAH to obtain a HDPE / PA6 / PE-g-MAH ternary blend.

[0028] The specific preparation process is as follows:

[0029] The equipment used to prepare high barrier materials is a twin-screw extruder. The main process parameters include temperature, speed and vacuum degree. The extruder parameters are set as follows:

[0030] Temperature setting: The extruder temperature is divided into ten zones in total. Different material categories have different set temperature ranges due to differences in melting and plasticizing temperatures. For example, the melting temperature of HDPE is generally between 180 and 200°C, and the melting point of PA6 is around 220°C to 240°C. For the same material, the set temperature is different due to the different structures of different zones of the twin-screw extruder. The temperature of the feed port is generally not set too high to prevent the material from melting quickly, sticking to the feed port, and affecting production capacity. Therefore, the temperature of the first zone that controls the feed port temperature can be controlled at 180°C to 200°C; the second to sixth sections are plasticizing sections, which require a slightly higher temperature to allow the material to melt quickly. The temperature of the plasticizing section can be controlled at 230°C to 240°C; the seventh to tenth sections are shearing sections. The material has almost melted in the previous plasticizing section, and the three materials are mixed under the action of shear force, which will generate more heat, so the temperature can be slightly lowered. The temperature of the shearing section can generally be controlled at 220℃~230℃; the temperature at the die head is relatively high. Increasing the temperature of the die head is to increase production capacity and make the drawing smoother, so the temperature at the die head is generally not lower than 240℃.

[0031] Speed ​​setting: The speed range of the test machine is 0-600rpm. For materials in the initial exploration stage, it is generally set at 60-70% speed, that is, 360-420rpm, and further adjustments are made depending on the specific production conditions. Increasing the speed helps to improve the extruder's shearing, mixing, and dispersing capabilities of the material; reducing the speed prolongs the material's residence time in the machine, which helps to fully plasticize the material.

[0032] Vacuum setting: The vacuum degree of the twin-screw extruder is <-0.09. During the melting process, plastic materials will more or less decompose to produce some small molecules, which need vacuum negative pressure to discharge. Otherwise, it will cause abnormal appearance of the injection molded parts at the back end (air entrapment, bonding lines, light and shadow, etc.), and the particles will be porous and fluffy, and the extrusion process will not be able to draw strips.

[0033] Example 1: A high-barrier high-density polyethylene modified composite material, by weight percentage, PA6 10%, PE-g-MAH 12%, the rest is HDPE, extrusion temperature zone 1 180°C, zone 2 to zone 6 240°C, zone 7 to zone 10 220°C, die head 240°C. Rotation speed 360rpm, vacuum degree -0.09MPa.

[0034] Example 2: A high-barrier high-density polyethylene modified composite material, by weight percentage, PA6 11%, PE-g-MAH 13%, the rest is HDPE, extrusion temperature zone 1 190°C, zone 2 to zone 6 240°C, zone 7 to zone 10 220°C, die head 240°C. Rotation speed 360rpm, vacuum degree -0.09MPa.

[0035] Example 3: A high-barrier high-density polyethylene modified composite material, by weight percentage, PA6 12%, PE-g-MAH 15%, the rest is HDPE, extrusion temperature zone 1 200°C, zone 2 to zone 6 240°C, zone 7 to zone 10 230°C, die head 240°C. Rotation speed 400rpm, vacuum degree -0.09MPa.

[0036] At present, the liner materials of Type IV gas cylinders reported internationally are mainly HPDE and PA6. However, using HDPE or PA6 alone as the liner material has its shortcomings. HDPE is easy to process and shape, but HDPE has poor high temperature resistance and is not very suitable for He and H 2 , O 2 PA6 has good high temperature resistance and is resistant to He, H 2 , O 2 The barrier property of HDPE / PA6 / PE-g-MAH is good, but its low temperature resistance is not as good as that of HDPE. Therefore, mixing the two together can effectively make up for the shortcomings. This time, a two-step method is used to mix HDPE / PA6 / PE-g-MAH. Compared with the one-step mixing, the two-step method helps to evenly distribute the dispersed phase in the matrix, thereby improving the material performance.

[0037] The mechanical properties, thermal properties and gas barrier properties of the HDPE / PA6 / PE-g-MAH blends prepared in the above examples were tested.

[0038] Mechanical test: The tensile test specimens were prepared according to the requirements of GB / T 1040. The tensile strength of the HDPE / PA6 / PE-g-MAH blend was measured by a tensile testing machine to be 18 MPa and the elongation at break was 494%.

[0039] Thermal test: Heat deformation temperature test specimens were prepared according to the requirements of GB / T1634, and the heat deformation temperature of HDPE / PA6 / PE-g-MAH blend was measured to be 45.9°C.

[0040] Gas barrier test: First, put the HDPE / PA6 / PE-g-MAH blend particles on a flat vulcanizer and heat-press them into 0.2mm thick and 50mm diameter discs, and then put the discs into a differential pressure gas permeometer for testing. Under the conditions of 0.1MPa and 15℃, the helium permeability coefficient of the HDPE / PA6 / PE-g-MAH blend is 1.44×10 -13 cm 3 cm / (cm 2 ·Pa·s).

[0041] Considering that hydrogen is a flammable and explosive gas, there are great safety risks in testing with hydrogen. Therefore, helium, whose molecular size is smaller than hydrogen, is used to test the gas permeability coefficient of the material. The specific test data of the helium permeability coefficient are shown in Table 1. Substituting the gas permeability in the table into the formula P = Q·d, the gas permeability coefficient of the material can be calculated. In the formula, P is the gas permeability coefficient, and the unit is cm 3 cm / (cm 2 ·s·Pa); Q is the gas permeation rate, unit is cm 3 / (m 2 ·day·0.1MPa); d is the sample thickness, in mm.

[0042] Table 1 Helium permeability test results of HDPE / PA6 / PE-g-MAH blends

[0043]

[0044] In summary, the present invention discloses a high barrier HDPE modified material, which mainly contains three components: HDPE, PA6, and PE-g-MAH. The two-step method is used for mixing, first premixing HDPE and PA6, and then blending the HDPE / PA6 premix with the compatibilizer PE-g-MAH. The molecular size of helium is smaller than that of hydrogen and has high safety, so helium is used instead of hydrogen for permeation test. The helium permeability test results show that the helium permeability coefficient of the HDPE / PA6 / PE-g-MAH blend is 1.44×10 -13 cm 3 cm / (cm 2 ·Pa·s), and has good gas barrier properties. In the future, HDPE / PA6 / PE-g-MAH modified materials can be used as liner materials for Type IV hydrogen storage cylinders.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-barrier high-density polyethylene modified composite material, characterized in that: It is a ternary blend of HDPE / PA6 / PE-g-MAH based on HDPE.

2. The high barrier high density polyethylene modified composite material according to claim 1, characterized in that: Calculated by weight percentage, the blend is based on HDPE, the content of PA6 accounts for 10% to 15%, and the content of PE-g-MAH accounts for 10% to 15%.

3. The high barrier high density polyethylene modified composite material according to claim 1, characterized in that: First, mix the HDPE and PA6 materials evenly according to the proportion, and then evenly mix the HDPE / PA6 premix particles with PE-g-MAH.

4. A method for preparing the high-barrier high-density polyethylene modified composite material according to claim 1, characterized in that: The steps include: Mix HDPE and PA6 evenly according to the proportion, and then evenly mix the HDPE / PA6 premix particles with PE-g-MAH; The above materials are prepared by a twin-screw extruder, and the temperature, speed and vacuum degree are set during the preparation process. Among them, the temperature setting is specifically as follows: the temperature of zone 1 of the feeding port is controlled at 180℃~200℃; zones 2 to 6 are plasticizing sections, and the temperature of the plasticizing sections is controlled at 230℃~240℃; zones 7 to 10 are shearing sections, and the temperature of the shearing sections is controlled at 220℃~230℃.

5. The method according to claim 4, characterized in that The temperature at the die of the die head shall not be lower than 240℃.

6. The method according to claim 4, characterized in that The rotation speed is set to 60 to 70% of the upper limit of the rotation speed of the testing machine.

7. The method according to claim 4, characterized in that The vacuum degree of the twin-screw extruder is <-0.09MPa.

8. The high-barrier high-density polyethylene modified composite material prepared by the method of claim 4 is applied to type IV gas cylinders and has good gas barrier properties.

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