Preparation method of high-density polyethylene attapulgite composite material

Abstract

This invention relates to the field of packaging materials technology, and more particularly to a method for preparing a high-density polyethylene (HDPE) attapulgite composite material. The method uses HDPE as the base material, MATT as the reinforcing filler, and MPE as the compatibilizer. The composite material is obtained through raw material pretreatment, melt blending, and secondary molding. MATT is prepared by grafting and modifying ATT using a hydrothermal method, and MPE is introduced to improve interfacial compatibility. The composite material exhibits optimal overall performance when the MATT addition is 0.4%. This method is simple, easily industrialized, and the resulting composite material shows significant improvements in mechanical properties, thermal stability, hydrophobicity, and barrier properties. It solves the performance defects of traditional HDPE and the agglomeration problem of ATT, making it suitable for food packaging, pipeline transportation, and other fields.

Description

Technical Field

[0001] This invention relates to the field of packaging materials technology, and in particular to a method for preparing a high-density polyethylene attapulgite composite material. Background Technology

[0002] High-density polyethylene (HDPE), as a widely used general-purpose plastic, occupies an important position in many fields such as food packaging, pipeline transportation, medical devices, and agricultural films due to its lightweight, low cost, non-toxicity, and excellent moisture resistance. With the development of the market economy and the improvement of people's living standards, the performance requirements for HDPE materials are becoming increasingly stringent, especially in terms of mechanical strength, heat resistance stability, and gas and water vapor barrier properties. Traditional HDPE can no longer meet the needs of high-end application scenarios.

[0003] To improve the performance defects of HDPE, the industry generally adopts the method of adding nanofillers for modification. Attapulgite (ATT) has become a highly promising inorganic nano-reinforcing filler due to its advantages such as abundant reserves, low price, large specific surface area and excellent physicochemical properties. However, there are several problems to be solved in the current technology of modifying HDPE with ATT: First, ATT is rich in polar silanol groups on its surface, while HDPE is a non-polar polymer. The poor interfacial compatibility between the two leads to the easy aggregation of ATT in the HDPE matrix, which cannot give full play to the nano-reinforcing effect. In fact, the agglomerates may even form stress weak points, reducing the mechanical properties of the composite material. Second, relying solely on physical blending is not enough to effectively improve the interfacial bonding between ATT and HDPE, resulting in limited improvement in the thermal stability of the composite material, and the improvement in gas and water vapor barrier properties is not as expected. Third, in the existing modification methods, the modification of ATT is mostly limited to simple surface treatment, failing to endow it with more functional groups through precise grafting modification to enhance the interaction with the polymer matrix. At the same time, the lack of synergistic effect of efficient compatibilizers limits the further improvement of the comprehensive performance of the composite material.

[0004] These problems make it difficult for existing HDPE / ATT composite materials to meet the requirements of high-end packaging, precision devices and other fields in terms of mechanical strength, heat resistance and barrier properties, thus restricting the expansion of their application scope. Therefore, developing a method for preparing high-density polyethylene / attapulgite composite materials that can solve the above defects has important practical significance and application value. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing high-density polyethylene attapulgite composite material.

[0006] To address the above problems, the present invention provides a method for preparing a high-density polyethylene attapulgite composite material, comprising the following steps: (1) Preparation of modified attapulgite MATT: The purified attapulgite ATT was added to distilled water and magnetically stirred at 45°C for 24 h until uniformly dispersed. Maleic anhydride MAH was added, and after magnetic stirring at 60°C, it was ultrasonically crushed and dried at 80°C into flakes. The flake product was added to distilled water and stirred at room temperature. Diethylamine DEA was added at 90°C and stirred. After ultrasonic crushing, it was dried at 80°C and pulverized. After washing with distilled water, it was dried again to obtain MATT. (2) Raw material pretreatment: High-density polyethylene (HDPE), carboxyl-modified polyethylene (MPE) and MATT prepared in step (1) were placed in an 80℃ oven and dried at a constant temperature for 8 hours. (3) Melt blending: Pretreated HDPE, MPE and MATT were added to the Hacker rheometer in proportion and melt blended for 5 min at a melting temperature of 170℃ and a rotor speed of 200 r / min to prepare the composite material precursor. (4) Secondary molding: The composite material precursor is placed in a flat vulcanizing machine, heated to 160°C until completely melted, and then molded. The pressure is increased to 15MPa. The mold is opened and closed 2-3 times to release the air. After holding the pressure for 10 minutes, it is naturally cooled to room temperature. After demolding, it is cut to obtain high-density polyethylene attapulgite composite material; wherein, the mass fraction of MATT in the composite material is 0.2%-0.8%.

[0007] Preferably, in step (1), the mass ratio of ATT to MAH is 2:1, and the mass ratio of MAH to DEA is 1:1.

[0008] Preferably, in step (1), the ultrasonic crushing treatment time is 1 hour.

[0009] Preferably, in step (3), the mass fraction of MATT in the composite material is 0.4%.

[0010] Preferably, in step (1), the purification process of ATT is as follows: ATT is added to an aqueous solution of sodium hexametaphosphate, magnetically stirred for 2 hours, ultrasonically crushed for 1 hour, centrifuged at 5500 rpm for 15 minutes, and the intermediate layer product is dried at 80°C and then pulverized and ground.

[0011] Compared with the prior art, the present invention has the following advantages: 1. Solves the problems of poor interface compatibility and agglomeration, significantly improving mechanical properties. This invention modifies ATT using a hydrothermal grafting method. The carboxyl groups generated from MAH hydrolysis react with the hydroxyl groups on the ATT surface, while simultaneously introducing amino groups from DEA, to prepare MATT with multiple functional groups, providing it with sites for interaction with the polymer matrix. Simultaneously, carboxyl-containing MPE is introduced as a compatibilizer. The carboxyl groups of MPE can chemically react with the hydroxyl and amino groups on the MATT surface to form stable ester and amide bonds, acting as a "bridge" between HDPE and MATT, effectively improving their interfacial compatibility. This design fundamentally solves the problem of ATT easily agglomerating in the HDPE matrix in existing technologies, allowing MATT to be uniformly dispersed in the HDPE matrix at an addition amount of 0.2%-0.4%, avoiding stress weak points formed by agglomerates and significantly improving the mechanical properties of the composite material. Experiments show that when the amount of MATT added is 0.4%, the tensile strength of the composite material can reach 32.6 MPa and the elongation at break can reach 915.72%, which significantly improves the mechanical properties compared with pure HDPE and composite materials without compatibilizer.

[0012] 2. Enhances interfacial bonding and improves thermal stability. The addition of MPE promotes the chemical bonding between MATT and HDPE, forming a denser internal structure of the composite material and reducing the probability of molecular chain breakage during thermal degradation. Simultaneously, MATT, as a rigid inorganic filler, effectively blocks heat transfer and slows down the thermal motion of HDPE molecular chains due to its uniform dispersion. Compared to existing composite materials prepared by simple physical blending, the composite material prepared in this invention exhibits a significantly higher thermal degradation initiation temperature, reaching 478.5℃ under a nitrogen atmosphere. This significantly improves thermal stability, overcoming the limitation of limited improvement in thermal stability in existing technologies and broadening its application scenarios in high-temperature environments.

[0013] 3. Optimize internal structure to improve barrier performance The uniform dispersion and tight bonding of MATT in the HDPE matrix result in a continuous, dense structure within the composite material. Simultaneously, the fibrous morphology of MATT elongates the permeation paths of gas and water vapor molecules. Furthermore, the chemical interaction between MPE, MATT, and HDPE further reduces porosity and defects within the composite material, minimizing gas and water vapor permeation channels. Experimental results show that when the MATT addition is 0.4%, the oxygen permeability coefficient of the composite material decreases to 4.15 × 10⁻⁴. -14 The water vapor permeability coefficient is significantly reduced, and the barrier performance is greatly improved compared with pure HDPE and existing modified composite materials. It effectively solves the problem of poor barrier performance improvement of composite materials in existing technologies, and can better meet the stringent requirements for barrier performance in food packaging and other fields.

[0014] 4. Process optimization, balancing practicality and economy. In the preparation method of this invention, the process parameters of each step are clearly defined and controllable. The melt blending and secondary molding processes are mature technologies in the field of polymer processing, requiring no special or complex equipment and facilitating industrial-scale production. Furthermore, ATT is abundant and inexpensive, and the MAH, DEA, and MPE used in the modification process are all conventional chemical raw materials, ensuring controllable raw material costs. Compared to existing complex modification processes, the method of this invention combines practicality and economy, reducing production costs while ensuring high performance of the composite material, thus facilitating market promotion and application. Attached Figure Description

[0015] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0016] Figure 1 This is a process flow diagram of the preparation method of the present invention; Figure 2 The infrared spectrum of MATT and its composite material according to the present invention; Figure 3 These are the test results of the mechanical properties of the MHDPE / MATT composite material of the present invention; Figure 4 This is a SEM image of the MHDPE / MATT composite material of the present invention; Figure 5 X-ray diffraction patterns of the MHDPE and MHDPE / MATT composite materials of the present invention; Figure 6 The TGA test curve of the MHDPE / MATT composite material of the present invention; Figure 7 Differential scanning calorimetry curve of the MHDPE / MATT composite material of the present invention; Figure 8 This is a water absorption diagram of the MHDPE / MATT composite material of the present invention; Figure 9 This is a diagram showing the contact angle data of the MHDPE / MATT composite material of the present invention; Figure 10 This is a diagram illustrating the oxygen molecule blocking effect of the MHDPE / MATT composite material of the present invention. Detailed Implementation

[0017] I. Implementation Cases (I) Introduction to Raw Materials (II) Instruments and Equipment (III) A method for preparing a high-density polyethylene attapulgite composite material (1) Preparation of modified attapulgite MATT: 3g of purified ATT was added to 100ml of distilled water and stirred magnetically at 45℃ for 24h until uniformly dispersed. 1.5g of MAH was added, and after stirring magnetically at 60℃, it was ultrasonically crushed for 1h and dried at 80℃ into flakes. The flake product was added to 100mL of distilled water, stirred at room temperature, and then 1.5g of DEA was added at 90℃. Stirring and ultrasonic crushing were continued for 1h, and the product was dried at 80℃, pulverized and ground, washed with distilled water and dried again to obtain MATT.

[0018] The ATT purification steps are as follows: 20g of ATT is added to 400ml of distilled water containing 0.6g of sodium hexametaphosphate, and the mixture is magnetically stirred for 2 hours. After ultrasonic disruption for 1 hour, the mixture is centrifuged at 5500rpm for 15 minutes. The intermediate layer product is then dried in an oven at 80℃ and pulverized to obtain purified ATT.

[0019] (2) Raw material pretreatment: HDPE, MPE and MATT were placed in an 80℃ oven and dried at a constant temperature for 8 hours to remove moisture.

[0020] (3) Melt blending: Weigh the pretreated HDPE, MPE and MATT in proportion, wherein HDPE ranges from 93.248% to 94%, MPE ranges from 5.952% to 6%, and the mass fractions of MATT in the composite material are 0%, 0.2%, 0.4%, 0.6% and 0.8%, respectively. Add them to the Hacker rheometer and melt blend for 5 min at 170℃ and 200r / min to obtain the composite material precursor.

[0021] (4) Secondary molding: Weigh the appropriate composite material precursor with an electronic balance and place it in the center of the mold of the flat vulcanizing machine. Heat it to 160°C until it is completely melted and then close the mold. Increase the pressure to 15MPa, open and close the mold 2-3 times to release the air, hold the pressure for 10 minutes and then cool it naturally to room temperature. After demolding, cut it into standard samples for later use.

[0022] II. Performance Testing The above embodiments of the present invention use HDPE as the base material, MATT as the reinforcing filler, and MPE as the compatibilizer to prepare five MHDPE / MATT composite materials with different contents through melt composite method. Simultaneously, the infrared spectra, mechanical properties, microstructure, X-ray diffraction, thermal stability, melting temperature and crystallinity, water absorption, contact angle, and barrier properties of these five composite materials were tested and studied. The testing process, results, and analysis are as follows: (a) Infrared spectroscopy test Test procedure: Fourier transform infrared spectrometer was used, at 4000-500 cm⁻¹ -1 Operating in transmission mode across the wavelength range, with a resolution of 1 cm. -1MATT, MHDPE, and MHDPE99.6MATT0.4 composite materials were ground into powders, mixed evenly with potassium bromide (KBr), and then pressed into circular thin sheets for infrared spectroscopy testing.

[0023] Test Results and Analysis: Reference Figure 2 The infrared spectra of MATT and its composites are shown. In the figure, a) is the Fourier transform infrared spectrum of MATT, MHDPE and MHDPE99.6MATT0.4, and b) and c) are magnified views.

[0024] In the infrared spectrum of MHDPE, 3435 cm⁻¹ -1 The characteristic peaks nearby correspond to the -OH groups of the carboxyl groups in MHDPE. At 2923 cm⁻¹... -1 The characteristic peak appearing near the 1789 cm⁻¹ is the stretching vibration peak of -CH₂-. Compared with the infrared spectrum of MHDPE, the infrared spectrum of the MHDPE99.6ATT0.4 composite material, in addition to the characteristic peaks of MHDPE and MATT, also shows a peak at 1789 cm⁻¹. -1 The characteristic peak of C=O in the ester bond appeared nearby. This could be due to the reaction between the -OH group on the ATT surface and the -COOH group on the MHDPE surface, or it could be due to the reaction between the -COOH group produced by MAH hydrolysis and the -OH group on the ATT surface. Furthermore, at 1647 cm⁻¹... -1 The characteristic peak intensity also became stronger and sharper, which may be due to the formation of an amide group (-CONH) after the reaction of -NH2 in MATT and -COOH in MHDPE. At approximately 783 cm⁻¹... -1 Peaks also appeared near the location, which may be characteristic peaks of the NH2 amine group grafted onto DEA by MATT. In summary, theoretically, MATT can be used as a nanofiller to modify MHDPE, and the carboxylic acid groups of MHDPE can have good compatibility with MATT, effectively enhancing the compatibility between the filler and the substrate.

[0025] (ii) Mechanical property testing Testing Procedure: The composite material after secondary molding was cut into dumbbell-shaped tensile test strips, approximately 115 mm in length, 4.3 mm in width, and 1 mm in thickness. According to GB / T1040-2006 standard, a computer-controlled electronic universal testing machine was used to conduct the test at a tensile speed of 50 mm / min. Six specimens were selected for each group, and the tensile strength and elongation at break were calculated.

[0026] Test Results and Analysis: Reference Figure 3The mechanical property test results of the MHDPE / MATT composite are shown in the figure. It is clearly observed from the figure that adding a small amount of MATT significantly improves the tensile strength and elongation at break of the composite. The tensile strength and elongation at break reach their maximum values ​​(32.6 MPa and 915.72%) when the MATT content is 0.4%. This not only demonstrates that the addition of MATT can improve the mechanical properties of the composite, but also proves that HDPE and MATT are good compatibility agents. With further increases in the addition amount, the tensile strength and elongation at break of the composite both decrease significantly. The reason for the decrease in tensile properties is that the high MATT content causes the agglomeration of nanomaterials, which alters the original orderly arrangement structure of MHDPE, thus leading to a decrease in mechanical properties.

[0027] MATT and HDPE are inherently incompatible and readily form aggregates. Previous studies showed that an addition of 0.4% resulted in optimal performance of the HDPE composite material. In this study, MPE with -COOH groups was selected to modify HDPE, demonstrating that this is an effective way to enhance the mechanical properties of HDPE.

[0028] (III) Microscopic morphology test Test procedure: The fracture surface of the tensile fractured sample was adhered to conductive adhesive and fixed on an aluminum sample nail for gold sputtering treatment (gold sputtering time 30s). The cross-sectional morphology was observed at different magnifications using a scanning electron microscope under the conditions of working current 5mA, test voltage 15kV and scanning acceleration voltage 3kV.

[0029] Test Results and Analysis: Reference Figure 4 The SEM images of the MHDPE / MATT composites shown are in (a)-e), corresponding to MATT additions of 0%, 0.2%, 0.4%, 0.6%, and 0.8%, respectively. As can be seen from the images, pure MHDPE exhibits an unentangled fibrous structure. The addition of MATT significantly increases the density of the MHDPE morphology, mainly due to the reaction between the -NH2 group of MATT and the -COOH group of MHDPE. When the addition amount is 0.2% and 0.4%, MATT is uniformly dispersed, with no defects on the tensile fracture surface and consistent fracture direction. As the addition amount continues to increase, the composite gradually exhibits the fibrous structure of pure HDPE, while the tensile strength and elongation at break also decrease significantly, and MATT aggregation occurs in the composite. This indicates that MPE can maintain a certain dispersion effect of MATT in HDPE, but excessively high MATT content still leads to poor compatibility with HDPE. Therefore, as the MATT content continues to increase, the mechanical properties of the material gradually decrease.

[0030] (iv) X-ray diffraction test Testing procedure: The composite material sample was cut into pieces approximately 1 cm in size. 2 The cube was heat-treated in an oven at 105℃ for 1 hour to eliminate thermal history. Cu-Kα diffraction (λ=0.154nm) was performed using an X-ray diffractometer at 40KV voltage and 40mA current, with data recorded every 0.02s to analyze the crystal structure.

[0031] Test Results and Analysis: Reference Figure 5 The X-ray diffraction patterns of MHDPE and the MHDPE / MATT composite are shown. It is directly observable from the images that there are distinct diffraction peaks at 21.5° and 23.9°. Furthermore, no new diffraction peaks appear in the overall composite spectrum; only the characteristic diffraction peaks of HDPE are present. This indicates that the addition of MATT does not alter the original crystal morphology of MHDPE; the crystal structure of the MHDPE / MATT composite remains orthorhombic, and the composite is a product of effective physical mixing of MATT and MHDPE. The XRD curves show that the characteristic peak intensity is lowest when the MATT addition is 0.4%. This is attributed to the fact that MATT may form the most uniform dispersion in the MHDPE matrix, leading to better nucleation efficiency and further reducing grain size. The large addition of MATT may restrict the movement of MHDPE macromolecular chains, thereby increasing the crystallinity of the MHDPE / MATT composite. On the other hand, at 2θ = 21.5° and 23.9°, except for a very slight leftward shift of the characteristic peak of the MHDPE99.6MATT0.4 composite sample, the other samples were essentially the same as those of MHDPE. This may be because MATT has better dispersion and is more distributed in the matrix, resulting in the highest nucleation density and the smallest inter-crystal distance. The above results further support the conclusion that MATT = 0.4% is the optimal addition amount.

[0032] (v) Thermal stability performance test Test procedure: Weigh 10mg of composite material sample and place it in a crucible. Using a comprehensive thermal analyzer, under nitrogen protection, heat the sample from room temperature to 750℃ at a heating rate of 10℃ / min. Record the mass change curve with temperature (TGA curve) and the first derivative curve of mass change (DTG curve) to analyze the thermal degradation behavior.

[0033] Test results and analysis: Figure 6 The TGA test curves of the MHDPE / MATT composite material are shown. a) and b) are the TGA and DTG curves of the MHDPE / MATT composite material measured in a nitrogen atmosphere, respectively. The obtained data are listed in Table 1.

[0034] Table 1. Relationship between thermogravimetric changes and temperature of MHDPE / MATT composite materials. From Figure a), we can clearly see that when the amount of MATT added is between 0.2% and 0.4%, the thermal degradation temperature of the composite material increases, indicating that the appropriate addition of MATT can improve the thermal stability of the composite material. In Figure b), the lowest point of the curve represents the temperature corresponding to the maximum degradation rate of the material. The maximum degradation rate temperatures are 496.89, 493.52, 494.44, 495.92, and 494.49 °C. Compared with pure MHDPE, the maximum thermal degradation rate temperature of the composite material decreases after the addition of MATT nanomaterials. This may be because the organic compounds grafted with MATT or the amide bonds formed between MATT and MHDPE are more prone to accelerated chain scission at high temperatures.

[0035] (vi) Thermal effect and crystallinity test Test procedure: A differential scanning calorimeter was used in a nitrogen atmosphere to raise the temperature from room temperature to 200°C at a rate of 10°C / min. After holding the temperature for 3 minutes, the temperature was lowered to room temperature, and then raised to 200°C again at a rate of 10°C / min. The temperature rise and fall curves were recorded, and the crystallization temperature (Tc), melting temperature (Tm), and enthalpy of fusion were calculated. Hm) and crystallinity (Xc), where Xc = ( Hm / ( Hm ×WHDPE))×100%, Hm 100% crystallization melting enthalpy of HDPE (293 J / g), WHDPE is the mass fraction of HDPE in the sample.

[0036] Test results and analysis: Figure 7 Differential scanning calorimetry (DSC) curves of the MHDPE / MATT composite material are shown, specifically the first cooling curve (a) and the second heating curve (b). The obtained data are listed in Table 2.

[0037] Table 2 Melting and Crystallization Behavior Data As shown in the figure, the Tc and Xc of pure MHDPE are 112.3℃ and 53.07%, respectively. The Tc of the composite material with added MATT is higher than that of pure MHDPE, which is a result of the heterogeneous nucleation effect of MATT. When the MATT content is 0.8%, the Tc value decreases, which is due to the poor compatibility caused by excessive MATT, restricting the movement of molecular chains and affecting crystal formation. Combined with mechanical properties, this indicates that a MATT content of 0.4% is the optimal addition amount. Appropriate MATT can be well dispersed in the matrix and acts as a good nucleating agent, resulting in finer crystals, which may lower the crystallization temperature of the composite material. This result is similar to the trend of the XRD analysis results.

[0038] Meanwhile, the Tm of composite materials is higher than that of HDPE. Generally speaking, the higher the crystallization temperature, the thicker the crystals and the higher the melting point. This is because a higher crystallization temperature increases the mobility of the chain segments, resulting in more complete crystals.

[0039] (vii) Water absorption performance test Test procedure: The composite material sample was dried in an oven at 105℃ for 8 hours until constant weight was reached. The weight was recorded as W. Then it was soaked in deionized water for 48 hours. After taking it out, the surface moisture was absorbed with filter paper and the weight was recorded as W0. The water absorption rate was calculated according to the formula WA=(W0-W) / W×100%.

[0040] Test results and analysis: Figure 8 The graph shows the water absorption of the MHDPE / MATT composite material. Water absorption rate is a test method used to characterize the compactness of the internal structure of composite materials, and it can further demonstrate the compactness of the internal structure of the MHDPE / MATT composite material due to reactions. As can be seen from the graph, the water absorption rate of MHDPE is very high. After adding MATT nanomaterials, the water absorption rate of the composite material shows a significant decrease. This is partly due to the reaction between the -COOH of MHDPE and the -OH on the surface of MATT, and partly because the -COOH of MHDPE also reacts with the -NH2 of MATT to form strong chemical bonds. This makes the MHDPE / MATT composite material more compact, making it less likely for water molecules to penetrate into the interior of the composite material, thus reducing its water absorption.

[0041] (viii) Hydrophilicity test Test procedure: The composite material sample was dried in an oven at 105℃ for 8 hours, placed on the sample platform of the contact angle measuring instrument, and 2μL of deionized water was automatically dripped in. The contact angle data was recorded by computer software.

[0042] Test results and analysis: Figure 9The contact angle data of the MHDPE / MATT composite material is shown in the figure. It can be seen that the contact angle value of the MHDPE / MATT composite material is significantly larger than that of pure MHDPE. This is because the -COOH groups on MHDPE can react with the -NH2 and OH groups on MATT to form a dense network structure, thereby enhancing the interfacial bonding force between MHDPE and MATT, making the composite material more compact. Furthermore, the COOH groups of MHDPE themselves have a certain degree of hydrophilicity, reacting with the OH and NH2 groups of MATT to form relatively hydrophobic ester and amide groups, respectively. Therefore, as the MATT content increases, the MHDPE / MATT contact angle becomes higher, exhibiting increasingly hydrophobic properties. These results indicate that the addition of MATT can improve the hydrophobicity of MHDPE.

[0043] (ix) Oxygen Barrier Effect Test Test procedure: The composite material sample was cut into a circle with a radius of 48 mm and placed on the test platform of the differential pressure gas permeation instrument. After the upper and lower chambers were sealed, one side was evacuated for 2 hours to remove gas. On the other side, nitrogen was first introduced to remove other gases, and then oxygen was introduced. Under the conditions of 25℃ and 50% humidity, the pressure change on the low-pressure side was monitored in real time, and the oxygen permeation coefficient was calculated.

[0044] Test results and analysis: Figure 10 The oxygen barrier effect of the MHDPE / MATT composite material is shown, specifically the oxygen permeability coefficient variation curve. As can be seen from the figure, the oxygen permeability coefficient of MHDPE is 10.12E-14. With the addition of nanomaterials, the oxygen permeability coefficients are 7.67E-14, 4.15E-14, 8.37E-14, and 9.51E-14, respectively, showing a trend of first decreasing and then increasing. This suggests that adding a small amount of MATT is beneficial to enhancing the oxygen barrier performance of the composite membrane, because MATT can react better with MHDPE to form a dense network structure. After adding 0.6% MATT, the oxygen permeability coefficient increases. This is because MATT agglomerates due to poor compatibility at higher concentrations, which may also create defects between the substrate and MATT. Therefore, the oxygen permeability through the composite material is shortened. Nevertheless, the oxygen barrier performance of the composite material is significantly improved even at low concentrations.

[0045] (x) Performance Test Summary (1) MATT can be uniformly dispersed in MHDPE matrix, changing the microstructure of composite material and significantly enhancing the mechanical properties of HDPE. When 0.4% is added, the tensile strength and elongation at break increase by 10.17 MPa and 443.55%, respectively. The introduction of a large amount of MATT will also cause agglomeration and destroy the original regular structure of HDPE, thereby reducing the mechanical properties of composite material.

[0046] (2) The introduction of COOH groups can effectively improve the interfacial compatibility between MATT and HDPE, enhance the interfacial bonding force between them, and reduce the probability of agglomeration.

[0047] (3) Nanomaterials can act as heterogeneous nucleation agents, lowering the melting temperature and increasing the crystallization temperature. Furthermore, the barrier effect of composite materials is greatly improved after the introduction of MPE and MATT. In summary, the addition of MATT significantly improves the tensile strength and elongation at break of HDPE. MATT-reinforced HDPE composites exhibit excellent mechanical properties, superior heat resistance, and lower water absorption. When the mass fraction of MATT in the composite is 0.4%, the MHDPE / MATT composite exhibits the best overall performance, with maximum tensile strength and elongation at break, and optimal thermal stability, hydrophobicity, and oxygen barrier properties. The addition of MPE effectively improves the compatibility between MATT and HDPE, reducing agglomeration. The heterogeneous nucleation effect of MATT optimizes the crystalline structure. The synergistic effect of both significantly enhances the composite's mechanical, thermal, and barrier properties, meeting the needs of high-end packaging and other applications.

[0048] The technical solution provided by this invention has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make several improvements and modifications to this invention without departing from the principles of this invention, and these improvements and modifications also fall within the protection scope of the claims of this invention.

Claims

1. A method for preparing a high-density polyethylene attapulgite composite material, characterized in that, Includes the following steps: (1) Preparation of modified attapulgite MATT: The purified attapulgite ATT was added to distilled water and magnetically stirred at 45°C for 24 h until uniformly dispersed. Maleic anhydride MAH was added, and after magnetic stirring at 60°C, it was ultrasonically crushed and dried at 80°C into flakes. The flake product was added to distilled water and stirred at room temperature. Diethylamine DEA was added at 90°C and stirred. After ultrasonic crushing, it was dried at 80°C and pulverized. After washing with distilled water, it was dried again to obtain MATT. (2) Raw material pretreatment: High-density polyethylene (HDPE), carboxyl-modified polyethylene (MPE) and MATT prepared in step (1) were placed in an 80℃ oven and dried at a constant temperature for 8 hours. (3) Melt blending: Pretreated HDPE, MPE and MATT were added to the Hacker rheometer in proportion and melt blended for 5 min at a melting temperature of 170℃ and a rotor speed of 200 r / min to prepare the composite material precursor. (4) Secondary molding: The composite material precursor is placed in a flat vulcanizing machine, heated to 160°C until completely melted, and then molded. The pressure is increased to 15MPa. The mold is opened and closed 2-3 times to release the air. After holding the pressure for 10 minutes, it is naturally cooled to room temperature. After demolding, it is cut to obtain high-density polyethylene attapulgite composite material; wherein, the mass fraction of MATT in the composite material is 0.2%-0.8%.

2. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of ATT to MAH is 2:1, and the mass ratio of MAH to DEA is 1:

1.

3. The preparation method according to claim 1, characterized in that, In step (1), the ultrasonic crushing treatment takes 1 hour.

4. The preparation method according to claim 1, characterized in that, In step (3), the mass fraction of MATT in the composite material is 0.4%.

5. The preparation method according to claim 1, characterized in that, In step (1), the purification process of ATT is as follows: ATT is added to sodium hexametaphosphate aqueous solution, magnetically stirred for 2 hours, ultrasonically crushed for 1 hour, centrifuged at 5500 rpm for 15 minutes, and the intermediate layer product is dried at 80°C and then pulverized and ground.

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