Morphological control and preparation method of iPP / HDPE (ipropene polymer / high-density polyethylene) blended oriented material

Abstract

The invention provides an application of a die drawing method in preparation of an iPP / HDPE blended orientation material and regulation and control of the morphology of the iPP / HDPE blended orientation material. The paper-like plastic blends with different microtopographies and macroscopic textures are prepared by regulating and controlling the blending ratio of the isotactic polypropylene with the specific melt index to the high-density polyethylene and carrying out die drawing processing at the specific temperature. According to the preparation method of the iPP / HDPE die drawing material provided by the invention, a compatilizer does not need to be added, and a series of oriented materials with different macroscopic morphologies and enhanced mechanical properties can be stably prepared by selecting iPP and HDPE with a specific melt index ratio, controlling the blending ratio of the iPP and the HDPE and combining a specific die drawing temperature; cooperative regulation and control of macroscopic morphology and performance of the material are realized.

Description

Technical Field

[0001] This invention belongs to the field of morphology control technology for blended orientation materials, and relates to the application of the die-drawing method in the preparation of iPP / HDPE blended orientation materials while controlling the morphology of iPP / HDPE blended orientation materials, a preparation method of iPP / HDPE blended orientation materials and its application, and particularly relates to the morphology control of iPP / HDPE blended orientation materials and its preparation method. Background Technology

[0002] Polypropylene (PP) and polyethylene (PE), as the most widely produced general-purpose plastics, have long been a research hotspot in both industry and academia for their blending modification. However, due to the thermodynamic incompatibility between isotactic polypropylene (iPP) and high-density polyethylene (HDPE), iPP and HDPE are typical incompatible polymer systems, and their simple blends often suffer from poor mechanical properties due to weak interfacial adhesion. A conventional approach to this problem is to add compatibilizers, but this not only increases costs but may also introduce other uncertainties.

[0003] Therefore, finding a more suitable way to solve the above-mentioned problems of existing blended materials is also one of the problems that many front-line researchers and R&D-oriented production enterprises in the industry urgently need to solve. Summary of the Invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide the application of the die-drawing method in the preparation of iPP / HDPE blended oriented materials while controlling the morphology of iPP / HDPE blended oriented materials, a method for preparing iPP / HDPE blended oriented materials and its application, and in particular, a method for preparing paper-like iPP / HDPE blended products. The present invention does not require the addition of compatibilizers. By selecting iPP and HDPE with specific melt index ratios and controlling their blending ratio, combined with specific die-drawing temperatures, a series of oriented materials with distinct microstructures, paper-like macrostructures, and enhanced mechanical properties can be stably prepared. This achieves synergistic control of the macroscopic morphology and properties of the materials and clarifies the critical ratio leading to processing failure.

[0005] This invention provides the application of the die-drawing method in the preparation of iPP / HDPE blend oriented materials while simultaneously controlling the morphology of iPP / HDPE blend oriented materials;

[0006] The iPP includes isotactic polypropylene with a specific melt index;

[0007] The HDPE includes high-density polyethylene with a specific melt index;

[0008] The melt index of the high-density polyethylene is greater than that of isotactic polypropylene.

[0009] Preferably, the die-drawing method specifically involves drawing the hot-pressed blank through a hot mold under the action of an external tensile force;

[0010] No compatibilizer is added in the preparation of the iPP / HDPE blend oriented material;

[0011] The molding process specifically involves molding at a specific temperature;

[0012] The application also includes using a die-stretching method to adjust the addition ratio of isotactic polypropylene and high-density polyethylene, thereby controlling the morphology of the iPP / HDPE blend oriented material.

[0013] Preferably, the application is specifically in the use of the die-drawing method to form a blended oriented material with enhanced mechanical properties by combining an incompatible system of iPP and HDPE without a compatibilizer.

[0014] The specific temperature is 80~150℃;

[0015] The regulation includes: increasing the melt index and / or molding temperature of HDPE, increasing the degree of morphological change of blended orientation materials with different blending ratios, and / or increasing the range of blending ratios that cannot form blended orientation materials.

[0016] The regulation includes: reducing the melt index and / or molding temperature of HDPE, reducing the degree of morphological change of blended orientation materials with different blending ratios, and / or reducing the range of blending ratios that cannot form blended orientation materials.

[0017] The morphology includes macroscopic morphology and / or microscopic morphology.

[0018] This invention also provides a method for preparing an iPP / HDPE blend oriented material, comprising the following steps:

[0019] 1) After melt blending isotactic polypropylene with a specific melt index and high-density polyethylene with a specific melt index, the mixture is hot-pressed and cooled to obtain the initial sheet.

[0020] 2) The initial sheet obtained in the above steps is subjected to unidirectional die stretching at a constant temperature to obtain iPP / HDPE blend oriented material.

[0021] Preferably, the melt index of the isotactic polypropylene with the specific melt index is 5~20 g / 10 min, and the test conditions are: 230℃ / 2.16 kg;

[0022] The melt index of the high-density polyethylene with the specified melt index is 15~30 g / 10 min, and the test conditions are 230℃ / 2.16 kg.

[0023] The melt index of the high-density polyethylene is greater than that of isotactic polypropylene.

[0024] The mass ratio of isotactic polypropylene to high-density polyethylene is (1~99):(99~1).

[0025] Preferably, the blending device includes a torque rheometer;

[0026] The mixing speed is 10~200 rpm;

[0027] The blending temperature is 170~220℃;

[0028] The blending time is 4 to 15 minutes.

[0029] Preferably, the hot pressing temperature is 180~220℃;

[0030] The pressure for hot pressing is 5~20MPa;

[0031] The hot pressing time is 5-10 minutes;

[0032] The cooling method is water cooling.

[0033] Preferably, the constant temperature is 80~150℃;

[0034] The unidirectional die stretching rate is 2~200mm / min;

[0035] The stretching ratio of the unidirectional die stretching is 2~8;

[0036] No compatibilizer is added during the preparation process.

[0037] Preferably, the iPP / HDPE blend oriented material is a sheet with a thickness of 0.5~5mm;

[0038] The preparation method is specifically a method for preparing iPP / HDPE blend oriented materials with adjustable morphology;

[0039] The preparation method further includes the following steps:

[0040] By adjusting the addition ratio of isotactic polypropylene and high-density polyethylene, iPP / HDPE blend oriented materials with different morphologies can be obtained.

[0041] The morphology includes macroscopic morphology and / or microscopic morphology;

[0042] The macroscopic morphology includes one or more of the following: a silky luster with texture along the stretching direction; a smooth surface with uniform translucency; a wood-like and / or shell-like layered pattern; and a dense surface with a uniform milky white color.

[0043] The present invention also provides the application of iPP / HDPE blend oriented materials in any of the above-described technical solutions, or the iPP / HDPE blend oriented materials prepared by any of the above-described technical solutions, in paper-like plastic products that are rewritable, have variable macroscopic morphology, and variable microscopic morphology.

[0044] This invention provides the application of the die-pulling method in the preparation of iPP / HDPE blend oriented materials while simultaneously controlling the morphology of these materials. The iPP comprises isotactic polypropylene with a specific melt index; the HDPE comprises high-density polyethylene with a specific melt index; and the melt index of the high-density polyethylene is greater than that of the isotactic polypropylene. Compared with existing technologies, this invention suggests that finding a simple and effective method to controllably prepare iPP / HDPE die-pulled materials with specific macroscopic morphology and enhanced properties without the addition of compatibilizers through simple formulation design is a feasible research direction. Die-pulling is a solid-state processing method that pulls a sample from a specially designed mold to achieve shaping and improve the orientation of molecular chains, significantly enhancing the mechanical properties of polymers. However, this technology is currently mostly applied to single polymers or systems with good compatibility. For typical incompatible systems like iPP / HDPE, during die-pulling, due to the inconsistent deformation behavior of the two phases, stress concentration at the phase interface easily occurs, leading to failure and making it difficult to obtain high-performance oriented products.

[0045] Based on this, this invention creatively applies the die-drawing method to prepare iPP / HDPE blend oriented materials while simultaneously controlling the morphology of these materials. This invention also specifically provides a method for preparing iPP / HDPE blend oriented materials, a method for preparing paper-like iPP / HDPE blend products. This method offers controllable morphology and texture: under specific melt flow index raw materials and specific die-drawing conditions (such as temperature), this invention can stably obtain various micromorphologies by changing the iPP / HDPE ratio, achieving effective control over the solid-state orientation structure of incompatible blend systems. It can stably obtain a series of paper-like plastics with different transparency and roughness, which are rewritable and whose mechanical properties can be adjusted according to requirements, achieving control between tear resistance and easy tearing. This invention clarifies that under specific conditions, there exists a critical ratio that leads to processing failure, revealing the nonlinear relationship between the phase structure and processing stability of iPP / HDPE blends during solid-state orientation, providing clear process guidance for industrial production and avoiding trial-and-error costs. The iPP / HDPE blend oriented material prepared by this invention exhibits synergistic performance enhancement. Mechanical property tests show that the tensile strength and elastic modulus of all drawn samples are significantly improved compared to the undrawn blend sheet, indicating that this invention achieves synergistic enhancement of mechanical properties without the need for a compatibilizer.

[0046] This invention prepares paper-like plastic blends with different microstructures and macrostructures by controlling the blending ratio of isotactic polypropylene (iPP) and high-density polyethylene (HDPE) with specific melt indices and performing molding processing at specific temperatures. The method for preparing iPP / HDPE molding materials provided by this invention does not require the addition of compatibilizers. By selecting iPP and HDPE with specific melt index ratios and controlling their blending ratio, combined with specific molding temperatures, a series of oriented materials with distinct macrostructures and enhanced mechanical properties can be stably prepared. This achieves synergistic control of the material's macrostructure and properties and clarifies the critical ratio leading to processing failure.

[0047] This invention prepares paper-like plastic blends with different microstructures and macrostructures by controlling the blending ratio of isotactic polypropylene (iPP) and high-density polyethylene (HDPE) with specific melt indices and performing molding at specific temperatures. The preparation method provided by this invention is simple and low-cost. The entire process requires no compatibilizers and utilizes only two commercially available plastics. Through simple physical blending and molding processes, it is possible to achieve differentiation in the microstructure and macroscopic properties of the materials. The process is simple and highly suitable for industrial production.

[0048] This invention also provides the application of preparing iPP / HDPE blended oriented materials in rewritable, reversible, and texture-adjustable paper-like plastic products. Attached Figure Description

[0049] Figure 1 These are comparison images of the macroscopic morphology of the molded samples obtained in Examples 1-4 and Comparative Examples 2-3 of the present invention;

[0050] Figure 2 This is a diagram showing the "stringing" fracture that occurred during the die-drawing process of Comparative Example 1 of the present invention (iPP / HDPE=3:7);

[0051] Figure 3 These are scanning electron microscope (SEM) images of the samples obtained in Examples 1-4 and Comparative Examples 1-3 of the present invention;

[0052] Figure 4 This is a comparison curve of the elongation at break of the samples obtained in Examples 1-4 and Comparative Examples 1-3 of the present invention;

[0053] Figure 5 This is a comparison curve of the elastic modulus of the samples obtained in Examples 1-4 and Comparative Examples 1-3 of the present invention;

[0054] Figure 6 This is a comparison curve of the tensile strength of the samples obtained in Examples 1-4 and Comparative Examples 1-3 of the present invention;

[0055] Figure 7 These are macroscopic morphology comparison images of the molded samples obtained in Example 5 of the present invention;

[0056] Figure 8 Here is a physical image of the die-drawing equipment used in this invention;

[0057] Figure 9 This is a schematic diagram illustrating the working principle of the die-drawing method provided by the present invention;

[0058] Figure 10 Macroscopic morphology photographs of the iPP / HDPE blend oriented material prepared for this invention and appearance photographs of other types of paper samples. Detailed Implementation

[0059] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims.

[0060] There are no particular restrictions on the source of any raw materials used in this invention; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0061] There are no particular restrictions on the purity of any raw materials used in this invention. However, this invention preferably uses analytical grade or the purity requirements conventional in the field of iPP / HDPE blends.

[0062] All raw materials of this invention are conventional in the field, and each brand name and abbreviation is clear and distinct in its relevant application. Those skilled in the art can purchase them from the market or prepare them by conventional methods based on the brand name, abbreviation and corresponding application.

[0063] This invention provides the application of the die-drawing method in the preparation of iPP / HDPE blend oriented materials while simultaneously controlling the morphology of iPP / HDPE blend oriented materials;

[0064] The iPP (isotactic polypropylene) includes isotactic polypropylene with a specific melt index;

[0065] The HDPE (high-density polyethylene) includes high-density polyethylene with a specific melt index;

[0066] The melt index of the high-density polyethylene is greater than that of isotactic polypropylene.

[0067] In this invention, the preferred method is to draw the hot-pressed blank through a hot mold under the action of an external tensile force.

[0068] In this invention, it is preferable not to add any compatibilizer in the preparation of the iPP / HDPE blend oriented material.

[0069] In this invention, the molding process is preferably performed at a specific temperature.

[0070] In this invention, the preferred application is the use of the die-drawing method to form an incompatible system of iPP and HDPE into a blended oriented material with enhanced mechanical properties under conditions without compatibilizer.

[0071] In this invention, the application preferably includes using a die-stretching method to adjust the addition ratio of isotactic polypropylene and high-density polyethylene, thereby controlling the morphology of the iPP / HDPE blend oriented material.

[0072] In this invention, the regulation preferably includes: increasing the melt index and / or temperature of HDPE, increasing the degree of morphological change of blended orientation materials with different blending ratios, and / or increasing the range of blending ratios that cannot form blended orientation materials.

[0073] In this invention, the regulation preferably includes: reducing the melt index and / or temperature of HDPE, reducing the degree of morphological change of blended orientation materials with different blending ratios, and / or reducing the range of blending ratios that cannot form blended orientation materials.

[0074] In this invention, the morphology preferably includes macroscopic morphology and / or microscopic morphology, more preferably macroscopic morphology or microscopic morphology.

[0075] This invention provides a method for preparing an iPP / HDPE blend oriented material, comprising the following steps:

[0076] 1) After melt blending isotactic polypropylene with a specific melt index and high-density polyethylene with a specific melt index, the mixture is hot-pressed and cooled to obtain the initial sheet.

[0077] 2) The initial sheet obtained in the above steps is subjected to unidirectional die stretching at a constant temperature to obtain iPP / HDPE blend oriented material.

[0078] The present invention first melt-blends isotactic polypropylene with a specific melt index and high-density polyethylene with a specific melt index, then hot-presses and cools to obtain an initial sheet.

[0079] In this invention, the melt index of the isotactic polypropylene with the specific melt index is preferably 5~20 g / 10 min (test conditions: 230℃ / 2.16 kg), more preferably 8~18 g / 10 min, more preferably 10~15 g / 10 min, more preferably 12~14 g / 10 min, and specifically 13 g / 10 min.

[0080] In this invention, the melt index of the high-density polyethylene with a specific melt index is preferably 15~30 g / 10min (test conditions: 230℃ / 2.16kg), more preferably 16~28 g / 10min, more preferably 17~25 g / 10min, more preferably 18~22 g / 10min, and specifically 20 g / 10min.

[0081] In this invention, the melt index of the high-density polyethylene is greater than that of isotactic polypropylene.

[0082] In this invention, the preferred mass ratio of isotactic polypropylene to high-density polyethylene is (1~99):(99~1), which can be (20~80):(80~20), or (40~60):(60~40). Specifically, it can be (30~99):(70~1), or (35~99):(65~1), or (40~99):(60~1). It can also be (1~30):(99~70), or (1~25):(99~75), or (1~20):(99~80).

[0083] In this invention, the blending device preferably includes a torque rheometer.

[0084] In this invention, the mixing speed is preferably 10~200 rpm, more preferably 30~180 rpm, more preferably 50~150 rpm, more preferably 80~130 rpm, and specifically 120 rpm.

[0085] In this invention, the blending temperature is preferably 170~220℃, more preferably 175~210℃, even more preferably 180~200℃, and specifically 180℃.

[0086] In this invention, the blending time is preferably 4 to 15 minutes, more preferably 5 to 13 minutes, even more preferably 5 to 10 minutes, and specifically 5 minutes.

[0087] In this invention, the temperature of the hot pressing is preferably 180~220℃, more preferably 185~215℃, even more preferably 190~210℃, and specifically 200℃.

[0088] In this invention, the pressure of the hot pressing is preferably 5~20MPa, more preferably 7~18MPa, more preferably 10~15MPa, and specifically 10MPa.

[0089] In this invention, the hot pressing time is preferably 5 to 10 minutes, more preferably 5 to 8 minutes, more preferably 5 to 6 minutes, and specifically 5 minutes.

[0090] In this invention, the cooling method is preferably water cooling.

[0091] Finally, the initial sheet obtained by the above steps is subjected to unidirectional die stretching at a constant temperature to obtain an iPP / HDPE blend oriented material.

[0092] In this invention, the constant temperature is preferably 80~150℃, more preferably 90~140℃, even more preferably 100~130℃, even more preferably 110~120℃, and specifically can be 120℃ or 115℃.

[0093] In this invention, the unidirectional stretching rate is preferably 2~200 mm / min, more preferably 5~100 mm / min, even more preferably 10~80 mm / min, even more preferably 20~50 mm / min, and specifically 30 mm / min.

[0094] In this invention, the stretching ratio of the unidirectional die stretching is preferably 2 to 8, more preferably 2.5 to 6, even more preferably 3 to 5, and specifically 3.

[0095] In this invention, it is preferable that no compatibilizer is added during the preparation process.

[0096] In this invention, the iPP / HDPE blend oriented material is preferably a sheet with a thickness of 0.5-5 mm, more preferably a sheet with a thickness of 1.5-4 mm, and even more preferably a sheet with a thickness of 2.5-3 mm.

[0097] In this invention, the preparation method is preferably a method for preparing iPP / HDPE blend oriented materials with adjustable morphology.

[0098] In this invention, the preparation method preferably further includes the following steps:

[0099] By adjusting the addition ratio of isotactic polypropylene and high-density polyethylene, iPP / HDPE blend oriented materials with different morphologies can be obtained.

[0100] In this invention, the morphology preferably includes macroscopic morphology and / or microscopic morphology, more preferably macroscopic morphology or microscopic morphology.

[0101] In this invention, the macroscopic morphology preferably includes one or more of the following: a silky luster with texture along the stretching direction, a smooth surface with uniform translucency, a wood and / or shell-like layered pattern, and a dense surface with uniform milky white color. More preferably, it is one of the following: a silky luster with texture along the stretching direction, a smooth surface with uniform translucency, a wood and / or shell-like layered pattern, and a dense surface with uniform milky white color.

[0102] This invention provides the application of iPP / HDPE blended oriented materials, or iPP / HDPE blended oriented materials prepared by any of the above-described technical solutions, in paper-like plastic products that are rewritable, have variable macroscopic and microscopic morphologies. Specifically, the macroscopic morphology can exhibit the fibrous morphology of paper materials or the fibrous morphology of paper materials when torn.

[0103] This invention provides a complete and refined overall technical solution to better guarantee the comprehensive performance and macro- and micro-morphological characteristics of iPP / HDPE blended oriented materials, and further improves the stability and controllability of iPP / HDPE blended oriented materials prepared by the die-drawing method.

[0104] This invention provides a method for preparing a rewritable, reversible, and texture-adjustable paper-like plastic product:

[0105] 1. Raw material preparation: Isotactic polypropylene (iPP) with a melt index of 0.1-200 g / 10 min (test conditions: 230℃ / 2.16 kg) and high-density polyethylene (HDPE) with a melt index of 0.1-200 g / 10 min (test conditions: 230℃ / 2.16 kg) are selected. The melt index of HDPE is higher than that of iPP.

[0106] 2. Melt blending and tableting: Melt blend iPP and HDPE in one of the following mass ratios: 9:1, 7:3, 5:5, 3:7, or 1:9. The blending equipment is a torque rheometer, the blending temperature is 170-220℃, the speed is 10-200 rpm, and the time is 4-15 minutes.

[0107] 3. Hot pressing: The blend is hot-pressed at 180-220℃ and 5-20MPa pressure for 5-10 minutes, and then quenched in ice water to obtain the initial sheet.

[0108] 4. Die-stretching orientation: After the initial sheet is cut to a suitable width, it is placed in a die-stretching device and unidirectionally stretched at a constant temperature of 80-150℃ and a rate of 2-200mm / min, with a stretching ratio of about 2-8.

[0109] Furthermore, a method for controlling the macroscopic morphology of iPP / HDPE molded materials specifically includes the following steps:

[0110] 1. Raw material preparation: Isotactic polypropylene (iPP) with a melt index of 13 g / 10 min (test conditions: 230℃ / 2.16 kg) and high-density polyethylene (HDPE) with a melt index of 20 g / 10 min (test conditions: 230℃ / 2.16 kg) were selected. The melt index of HDPE is higher than that of iPP.

[0111] 2. Melt Blending and Tableting: iPP and HDPE are melt blended at one of the following mass ratios: 9:1, 7:3, 5:5, 3:7, or 1:9. The blending equipment is a torque rheometer, the blending temperature is 180℃, the blending speed is 120 rpm, and the blending time is 5 minutes.

[0112] 3. Hot pressing: The blend is hot-pressed at 200℃ and 10MPa for 5 minutes, and then quenched in ice water to obtain the initial sheet.

[0113] 4. Die-stretching orientation: After the initial sheet is cut to a suitable width, it is placed in a die-stretching device and unidirectionally stretched at a constant temperature of 120℃ or 115℃ at a rate of 30mm / min, with a stretching ratio of approximately 3.

[0114] Under molding temperatures of 120°C or 115°C, blends of iPP / HDPE with different proportions exhibit distinctly different yet repeatable processing behaviors and macroscopic morphologies, and their mechanical properties are enhanced.

[0115] When the iPP / HDPE ratio is 9:1, the sample exhibits a distinct silky luster and fine texture along the stretching direction.

[0116] When the iPP / HDPE ratio is 7:3, the sample appears uniformly translucent with a smooth surface.

[0117] When the iPP / HDPE ratio is 5:5, the sample exhibits a unique layered peeling structure, with macroscopically visible layered patterns resembling wood or seashells.

[0118] When the iPP / HDPE ratio is 3:7, the sample with this ratio will experience necking at the mold opening during die pulling and will immediately break, making it impossible to obtain a complete sample.

[0119] When the iPP / HDPE ratio is 1:9, the sample appears as a uniform milky white color with a dense texture.

[0120] This invention, under specific melt flow index raw material and temperature molding conditions, can stably obtain a variety of macroscopic morphologies by changing the iPP / HDPE ratio, achieving effective control over the solid-state orientation structure of incompatible blends, thereby realizing controllability of morphology and texture. This invention can stably obtain a series of paper-like plastics with different transparency and roughness. These paper-like plastics are rewritable, and their mechanical properties can be adjusted according to requirements, achieving control between tear resistance and easy tearing. This invention also provides a critical ratio, clarifying that under specific conditions, a 3:7 ratio is a critical ratio leading to processing failure. This reveals the nonlinear relationship between the phase structure and processing stability of iPP / HDPE blends during solid-state orientation.

[0121] See Figure 8 , Figure 8 This is a physical image of the die-drawing equipment used in this invention.

[0122] See Figure 9 , Figure 9 This is a schematic diagram illustrating the working principle of the die-drawing method provided by the present invention.

[0123] This invention provides the application of the die-drawing method in the preparation of iPP / HDPE blend oriented materials while simultaneously controlling the morphology of these materials, a method for preparing iPP / HDPE blend oriented materials, and their applications. This invention utilizes the die-drawing method to prepare iPP / HDPE blend oriented materials while simultaneously controlling their morphology. Furthermore, this invention specifically provides a method for preparing iPP / HDPE blend oriented materials, which is a method for preparing paper-like iPP / HDPE blend products. This method offers controllability in morphology and texture: under specific melt flow index raw materials and specific die-drawing conditions (such as temperature), this invention can stably obtain various microstructures by changing the iPP / HDPE ratio, achieving effective control over the solid-state orientation structure of incompatible blend systems. It can stably obtain a series of paper-like plastics with different transparency and roughness, which are rewritable and whose mechanical properties can be adjusted according to requirements, achieving control between tear resistance and easy tearing. This invention clarifies that under specific conditions, there exists a critical ratio that leads to processing failure. This reveals the nonlinear relationship between the phase structure and processing stability of iPP / HDPE blends during solid-state orientation, providing clear process guidance for industrial production and avoiding trial-and-error costs. The iPP / HDPE blend orientation materials prepared by this invention exhibit synergistic performance enhancement. Mechanical property tests show that the tensile strength and elastic modulus of all drawn samples are significantly improved compared to the undrawn blend sheets, indicating that this invention achieves synergistic enhancement of mechanical properties without the need for compatibilizers.

[0124] This invention prepares paper-like plastic blends with different microstructures and macrostructures by controlling the blending ratio of isotactic polypropylene (iPP) and high-density polyethylene (HDPE) with specific melt indices and performing molding processing at specific temperatures. The method for preparing iPP / HDPE molding materials provided by this invention does not require the addition of compatibilizers. By selecting iPP and HDPE with specific melt index ratios and controlling their blending ratio, combined with specific molding temperatures, a series of oriented materials with distinct macrostructures and enhanced mechanical properties can be stably prepared. This achieves synergistic control of the material's macrostructure and properties and clarifies the critical ratio leading to processing failure.

[0125] This invention prepares paper-like plastic blends with different microstructures and macrostructures by controlling the blending ratio of isotactic polypropylene (iPP) and high-density polyethylene (HDPE) with specific melt indices and performing molding at specific temperatures. The preparation method provided by this invention is simple and low-cost. The entire process requires no compatibilizers and utilizes only two commercially available plastics. Through simple physical blending and molding processes, it is possible to achieve differentiation in the microstructure and macroscopic properties of the materials. The process is simple and highly suitable for industrial production.

[0126] This invention also provides the application of preparing iPP / HDPE blended oriented materials in rewritable, reversible, and texture-adjustable paper-like plastic products.

[0127] To further illustrate the present invention, the following describes in detail, with reference to embodiments, the application of the die-drawing method provided by the present invention in the preparation of iPP / HDPE blend oriented materials and the control of iPP / HDPE blend oriented materials morphology, a method for preparing iPP / HDPE blend oriented materials and its application. However, it should be understood that these embodiments are implemented under the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operating procedures, only to further illustrate the features and advantages of the present invention, and not to limit the scope of protection of the claims of the present invention. The scope of protection of the present invention is not limited to the following embodiments.

[0128] Examples 1-4 and Comparative Examples 1-3

[0129] 1. Raw material preparation: Isotactic polypropylene (iPP) with a melt index of 13 g / 10 min (test conditions: 230℃ / 2.16 kg) and high-density polyethylene (HDPE) with a melt index of 20 g / 10 min (test conditions: 230℃ / 2.16 kg) were selected. The melt index of HDPE is higher than that of iPP.

[0130] 2. Melt blending and tableting: iPP and HDPE are melt blended at one of the following mass ratios: 9:1, 7:3, 5:5, 3:7, or 1:9. The blending equipment is a torque rheometer, the blending temperature is 180℃, the blending speed is 120 rpm, and the blending time is 5 minutes.

[0131] 3. Hot pressing: The blend is hot pressed at 200℃ and 10MPa pressure for 5 minutes, and then quenched in ice water to obtain the initial sheet.

[0132] 4. Die-stretching orientation: After the initial sheet is cut to a suitable width, it is placed in a die-stretching device and unidirectionally stretched at a constant temperature of 120℃ or 115℃ at a rate of 30mm / min, with a stretching ratio of approximately 3.

[0133] When the iPP / HDPE ratio is 9:1, the sample exhibits a distinct silky luster and fine texture along the stretching direction.

[0134] When the iPP / HDPE ratio is 7:3, the sample appears uniformly translucent with a smooth surface.

[0135] When the iPP / HDPE ratio is 5:5, the sample exhibits a unique layered peeling structure, with macroscopically visible layered patterns resembling wood or seashells.

[0136] When the iPP / HDPE ratio is 3:7, the sample exhibits a "string-like" necking at the die opening during molding and immediately breaks, making it impossible to obtain a complete sample. (Comparative Example 1)

[0137] When the iPP / HDPE ratio is 1:9, the sample appears as a uniform milky white color with a dense texture.

[0138] Examples 1-4

[0139] The samples were melt-blended and hot-pressed at iPP / HDPE mass ratios of 9:1, 7:3, 5:5, and 1:9, respectively, and then die-stretched at 120℃ (9:1, 7:3, 5:5) and 115℃ (1:9). All samples were successfully obtained as complete oriented samples with different macroscopic morphologies.

[0140] Comparative Example 1

[0141] Repeat the above steps with an iPP / HDPE mass ratio of 3:7. When the sample was drawn at 120°C, it necked and broke at the die opening, resulting in an incomplete sample.

[0142] Comparative Examples 2-3 (Pure Component Control)

[0143] When pure iPP and pure HDPE are molded under the same conditions (120℃), the pure iPP sample is macroscopically transparent and glossy, while the pure HDPE sample is macroscopically milky white.

[0144] See Figure 1 , Figure 1 These are macroscopic morphology comparison images of the molded samples obtained in Examples 1-4 and Comparative Examples 2-3 of the present invention. Wherein, a: Comparative Example 2 (pure iPP); b: Example 1 (9:1); c: Example 2 (7:3); d: Example 3 (5:5); e: Example 4 (1:9); f: Comparative Example 3 (pure HDPE).

[0145] See Figure 2 , Figure 2 This is a diagram showing the "stringing" fracture that occurred during the die-drawing process of Comparative Example 1 of the present invention (iPP / HDPE=3:7).

[0146] See Figure 3 , Figure 3 These are scanning electron microscope (SEM) images of the samples obtained in Examples 1-4 and Comparative Examples 1-3 of this invention. Wherein, a: Example 1 (9:1); b: Example 2 (7:3); c: Example 3 (5:5); d: Example 4 (1:9); e: Comparative Example 1 (3:7); f: Comparative Example 2 (pure iPP); g: Comparative Example 3 (pure HDPE).

[0147] Figure 3 Examples 1-4 and Comparative Examples 1-3 illustrate the microphase morphology of the prepared samples.

[0148] See Figure 4 , Figure 4 This is a comparison curve of the elongation at break of the samples obtained in Examples 1-4 and Comparative Examples 1-3 of the present invention.

[0149] See Figure 5 , Figure 5 This is a comparison curve of the elastic modulus of the samples obtained in Examples 1-4 and Comparative Examples 1-3 of the present invention.

[0150] See Figure 6 , Figure 6 This is a comparison curve of the tensile strength of the samples obtained in Examples 1-4 and Comparative Examples 1-3 of the present invention.

[0151] Example 5

[0152] The preparation process is the same as in the example, except that the molding temperature is 140°C.

[0153] See Figure 7 , Figure 7 These are macroscopic morphology comparison images of the molded samples obtained in Example 5 of the present invention. Wherein, a: iPP / HDPE (9:1); b: iPP / HDPE (7:3); c: iPP / HDPE (5:5).

[0154] See Figure 10 , Figure 10 Macroscopic morphology photographs of the iPP / HDPE blend oriented material prepared for this invention and appearance photographs of other paper-like samples. Wherein, a: unmolded sample and paper-like samples with different transparency; b: sample prepared for this invention that can be torn like paper; c: images of writing, erasing, and rewriting on the paper-like sample prepared for this invention.

[0155] The foregoing has provided a detailed description of the morphology control and preparation method of an iPP / HDPE blend orientation material provided by the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are merely for the purpose of helping to understand the method and core ideas of the present invention, including the best mode, and also to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements that are not different from the textual description of the claims, or if they include equivalent structural elements that are not substantially different from the textual description of the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. Application of the die-drawing method in the preparation of iPP / HDPE blend oriented materials and the control of iPP / HDPE blend oriented materials morphology; The iPP includes isotactic polypropylene with a specific melt index; The HDPE includes high-density polyethylene with a specific melt index; The melt index of the high-density polyethylene is greater than that of isotactic polypropylene.

2. The application according to claim 1, characterized in that, The die-drawing method specifically involves drawing the hot-pressed blank through a hot mold under the action of an external tensile force. No compatibilizer is added in the preparation of the iPP / HDPE blend oriented material; The molding process specifically involves molding at a specific temperature; The application also includes using a die-stretching method to adjust the addition ratio of isotactic polypropylene and high-density polyethylene, thereby controlling the morphology of the iPP / HDPE blend oriented material.

3. The application according to claim 2, characterized in that, The specific application is the use of the die-drawing method to form a blended oriented material with enhanced mechanical properties by combining an incompatible system of iPP and HDPE without compatibilizers. The specific temperature is 80~150℃; The regulation includes: increasing the melt index and / or molding temperature of HDPE, increasing the degree of morphological change of blended orientation materials with different blending ratios, and / or increasing the range of blending ratios that cannot form blended orientation materials. The regulation includes: reducing the melt index and / or molding temperature of HDPE, reducing the degree of morphological change of blended orientation materials with different blending ratios, and / or reducing the range of blending ratios that cannot form blended orientation materials. The morphology includes macroscopic morphology and / or microscopic morphology.

4. A method for preparing an iPP / HDPE blend oriented material, characterized in that, Includes the following steps: 1) After melt blending isotactic polypropylene with a specific melt index and high-density polyethylene with a specific melt index, the mixture is hot-pressed and cooled to obtain the initial sheet. 2) The initial sheet obtained in the above steps is subjected to unidirectional die stretching at a constant temperature to obtain iPP / HDPE blend oriented material.

5. The preparation method according to claim 4, characterized in that, The melt index of the isotactic polypropylene with the specified melt index is 5~20 g / 10 min, and the test conditions are: 230℃ / 2.16 kg. The melt index of the high-density polyethylene with the specified melt index is 15~30 g / 10 min, and the test conditions are 230℃ / 2.16 kg. The melt index of the high-density polyethylene is greater than that of isotactic polypropylene. The mass ratio of isotactic polypropylene to high-density polyethylene is (1~99):(99~1).

6. The preparation method according to claim 4, characterized in that, The blending device includes a torque rheometer; The mixing speed is 10~200 rpm; The blending temperature is 170~220℃; The blending time is 4 to 15 minutes.

7. The preparation method according to claim 4, characterized in that, The hot pressing temperature is 180~220℃; The pressure for hot pressing is 5~20MPa; The hot pressing time is 5-10 minutes; The cooling method is water cooling.

8. The preparation method according to claim 4, characterized in that, The constant temperature is 80~150℃; The unidirectional die stretching rate is 2~200mm / min; The stretching ratio of the unidirectional die stretching is 2~8; No compatibilizer is added during the preparation process.

9. The preparation method according to claim 4, characterized in that, The iPP / HDPE blend oriented material is a sheet with a thickness of 0.5~5mm; The preparation method is specifically a method for preparing iPP / HDPE blend oriented materials with adjustable morphology; The preparation method further includes the following steps: By adjusting the addition ratio of isotactic polypropylene and high-density polyethylene, iPP / HDPE blend oriented materials with different morphologies can be obtained. The morphology includes macroscopic morphology and / or microscopic morphology; The macroscopic morphology includes one or more of the following: a silky luster with texture along the stretching direction; a smooth surface with uniform translucency; a wood-like and / or shell-like layered pattern; and a dense surface with a uniform milky white color.

10. The application of the iPP / HDPE blend oriented material in any one of claims 1 to 3, or the iPP / HDPE blend oriented material prepared by any one of claims 4 to 9, in paper-like plastic products that are rewritable, have variable macroscopic morphology, and variable microscopic morphology.

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