High haze HDPE composite and method for making the same

Abstract

The application relates to the technical field of composite materials, and particularly discloses a high-haze HDPE composite material and a preparation method thereof, which comprises the following components in parts by weight: 100 parts of a base material, 5-10 parts of polypropylene, 20-40 parts of monomers, 10-20 parts of small-molecule amorphous substances and 0.1-0.5 parts of an antioxidant; the base material is compounded by low-crystallinity HDPE and HDPE, and the weight proportion of the low-crystallinity HDPE in the base material is 5-20%. The high-haze HDPE composite material is obtained by studying the structural characteristics of high-density polyethylene, adding small-molecule amorphous substances and introducing monomers to modify the high-density polyethylene, increasing the branching degree of the high-density polyethylene to adjust the haze and improve the mechanical properties, so that the haze is increased and the mechanical properties of the material are not reduced.

Description

Technical Field

[0001] This invention relates to the field of composite material technology, specifically to a high-haze HDPE composite material and its preparation method. Background Technology

[0002] With the development of industry, people are using more and more plastic products in their daily lives. At the same time, people's requirements for plastic products are also getting higher and higher. More and more people are starting to pursue products with more texture and artistry. Among them, high haze plastic is very popular because it can provide a hazy and blurred visual effect and can effectively scatter light to make the light more evenly distributed, creating a specific aesthetic atmosphere and enhancing the appearance and grade of the product.

[0003] However, existing methods for preparing high-haze plastics mainly achieve light scattering by adding inorganic fillers or light diffusing agents. However, this method has certain drawbacks, such as deteriorating the tensile strength and light transmission of the plastic. It requires the addition of a large amount of additives to enhance the plastic, which increases costs and easily causes pollution. This method does not meet the requirements of modern energy conservation and environmental protection. Therefore, technological improvements are needed to overcome these drawbacks.

[0004] Compared to linear low-density polyethylene (LLDPE) and low-density polyethylene (LDPE), high-density polyethylene (HDPE) exhibits superior tensile and flexural mechanical properties. HDPE also possesses excellent chemical resistance and electrical insulation, making it widely used in various fields. However, the higher the flowability of HDPE, the lower the haze; lower HDPE content also results in lower haze, leading to less than ideal light scattering. Traditional linear HDPE, in its molten state, has a lower degree of molecular chain entanglement, causing fluid flow instability during production. Therefore, the haze of polyethylene materials can be increased by adjusting the crystallinity of polyethylene. One method is to increase the branching degree of polypropylene, introducing long branches to reduce the crystallinity of polyethylene and thus increase haze. Another method is to add small-molecule amorphous substances to form more amorphous substances in the polyethylene material, thereby reducing the crystallinity and increasing haze. However, reduced crystallinity of polyethylene leads to decreased mechanical strength, and toughness and heat resistance are also affected.

[0005] Therefore, the key to solving the problem lies in how to increase the crystallinity of polyethylene (HDPE or LLDPE) with high mechanical properties and make it have both high haze and excellent mechanical properties. Summary of the Invention

[0006] The purpose of this invention is to provide a high-haze HDPE composite material and its preparation method, aiming to solve the problem that HDPE cannot simultaneously achieve high haze and excellent mechanical properties.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution: This invention provides a high-haze HDPE composite material, which comprises the following components in parts by weight: 100 parts matrix material, 5-10 parts polypropylene, 20-40 parts monomer, 10-20 parts small molecule amorphous substance, and 0.1-0.5 parts antioxidant. The matrix material is composed of low-crystallinity HDPE and HDPE, and the weight percentage of low-crystallinity HDPE in the matrix material is 5-20%.

[0008] Specifically, the high-haze HDPE composite material provided by this invention benefits from the study of the structural characteristics of high-density polyethylene (HDPE) itself. By adding small-molecule amorphous substances and introducing monomers to modify HDPE, the branching degree of HDPE is increased to adjust the haze and improve the mechanical properties, thus achieving the effect of increasing haze without reducing the mechanical properties of the material.

[0009] Furthermore, a high-haze HDPE composite material: the monomer is selected from one or more of trimethylolpropane triacrylate (TMPTA), tripropylene glycol diacrylate (TPGDA), ethylene glycol dimethacrylate (EGDMA), diethylene glycol diacrylate (DEGDM), trivinylbenzene (TEB), divinylbenzene (DVB), and N,N'-methylenebisacrylamide (MBAAm).

[0010] Furthermore, a high-haze HDPE composite material: the small molecule amorphous substance is selected from one or more of ethylene, n-hexane, and isopentane.

[0011] Furthermore, a high-haze HDPE composite material: the antioxidant is selected from one or more of antioxidants DLTP, TPP, TNP, CA, 330, 164, 1010, and 1076.

[0012] This invention also provides a method for preparing a high-haze HDPE composite material, the method comprising the following steps: S1. Irradiation treatment: HDPE is irradiated to obtain pre-irradiated polyethylene; S2. Preparation of branched polyethylene: Pre-irradiated polyethylene is immersed in a monomer solution, taken out and reacted at the first temperature, then filtered, washed and dried to obtain branched polyethylene. S3. Preparation of low-crystallinity HDPE: Under vacuum conditions, small-molecule amorphous substances are introduced into a reaction vessel containing the branched polyethylene in the form of vapor to carry out the reaction, thereby obtaining low-crystallinity HDPE. S4. After uniformly mixing the low-crystallinity HDPE, HDPE, polypropylene and antioxidant, the mixture is melt-extruded and granulated to obtain a high-haze HDPE composite material.

[0013] Specifically, the core idea of ​​the preparation method of this high-haze HDPE composite material is to combine irradiation grafting technology with small molecule intercalation technology to reduce crystallinity, so as to prepare a special low-crystallinity HDPE functional component and cleverly utilize its incompatibility with polypropylene (PP) to construct a multi-layer light scattering structure inside the composite material to improve haze. That is, first modify the crystallization characteristics of the matrix resin to obtain low-crystallinity HDPE, and then use its incompatibility with another polymer (PP) to synergistically enhance the effect and achieve high haze.

[0014] Furthermore, a method for preparing a high-haze HDPE composite material: In step S1, HDPE is irradiated with γ-rays, wherein the γ-ray source is... 60 Co, energy 3–5 MeV, beam current 100 A, dose rate 0–360 kGy / h, intensity 5.55 x 10⁻⁶ 11 Bq, where the atmosphere is air, oxygen, vacuum, or an inert gas.

[0015] Furthermore, a method for preparing a high-haze HDPE composite material: in step S2, the soaking time is 12-36 hours, the first reaction temperature is 100-150℃, and the reaction time is 15-20 minutes.

[0016] Furthermore, a method for preparing a high-haze HDPE composite material: In step S3, a small molecule amorphous substance is heated in a water bath to form vapor, the reaction temperature is 50-200℃, and the reaction time is 1-3 hours.

[0017] The beneficial effects of this invention are: The high-haze HDPE composite material provided by this invention uses a matrix material composed of low-crystallinity HDPE prepared by a specific method and ordinary HDPE. The low-crystallinity HDPE itself has a large number of grain boundary defects due to imperfect crystallization, which can scatter light. The HDPE / PP incompatible system will generate a large number of phase interfaces, which serve as the main light scattering source. Introducing low-crystallinity HDPE into the HDPE / PP system can make the compatibility between the two phases worse or the phase morphology more irregular, thereby further increasing the scattering interface and improving the haze effect.

[0018] Traditional methods for improving the haze of plastics mainly rely on adding inorganic fillers (such as calcium carbonate and talc) or blending with incompatible polymers (light diffusing agents). However, these methods often come at the cost of sacrificing the material's mechanical properties, processing flowability, or transparency. The high-haze HDPE composite material provided by this invention abandons the traditional approach of relying on additives to improve haze. Instead, it constructs a light-scattering structure within the HDPE matrix through precise physical and chemical modification, ensuring a high haze effect while avoiding a reduction in the material's mechanical properties. The process route of this invention involves first irradiating HDPE to generate active sites, then grafting specific monomers to form a branched structure, followed by intercalation of small-molecule amorphous substances to disrupt crystallization, and finally melt blending with polypropylene to complete the process loop. The entire process aims to actively create a large number of micro-phase interfaces from the molecular chain structure to the phase state level. These micro-phase interfaces can serve as light scattering centers, thereby achieving efficient light scattering and exhibiting a high haze effect on a macroscopic scale.

[0019] The preparation method provided by this invention involves first irradiating HDPE to generate stable peroxides or free radicals, then contacting the irradiated HDPE with monomers or small molecules outside a radiation field, and performing a copolymerization reaction under heating conditions in air or vacuum. This method improves the utilization rate of the radiation source, avoids the formation of large amounts of homopolymer, prevents monomer waste, and reduces the need for washing away homopolymer. The process of this invention prepares long-chain branched polyethylene from the polyethylene structure and adds small molecules to reduce crystallinity, thereby improving the material's haze without deteriorating its mechanical properties; in fact, it improves them. This avoids the need for large amounts of additives (such as matting agents and light stabilizers), reducing pollution, protecting the environment, and expanding the application range.

[0020] The high-haze HDPE composite material provided by this invention improves the hardness and strength of polyethylene by adding a small amount of polypropylene to polyethylene, taking advantage of the high heat resistance and good mechanical properties of polypropylene. In particular, it improves the impact strength at low temperatures, reduces the possibility of deformation and breakage, and broadens the application range of the material. Detailed Implementation

[0021] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0022] Example 1

[0023] This embodiment 1 provides a high-haze HDPE composite material, which comprises the following components in parts by weight: 100 parts matrix material, 5 parts polypropylene, 20 parts monomer, 12 parts small molecule amorphous substance and 0.2 parts antioxidant; the matrix material is composed of 5 parts low crystallinity HDPE and 95 parts HDPE. The preparation method of this high-haze HDPE composite material includes the following specific steps: S1. Irradiation treatment: High-density polyethylene (HDPE) is subjected to gamma ray irradiation treatment to obtain pre-irradiated polyethylene; S2. Preparation of branched polyethylene: Pre-irradiated polyethylene was immersed in a monomer solution (obtained by dissolving trimethylolpropane triacrylate in alcohol) and sealed for 24 hours. Then it was taken out and placed in a high-temperature reactor and reacted at the first temperature (120°C) and under air conditions for 15 minutes. After the reaction was completed, it was filtered, washed and dried to obtain branched polyethylene. S3. Preparation of low crystallinity HDPE: Branched polyethylene is placed in a reaction vessel and vacuumed. Small molecule amorphous substance (n-hexane) is heated in a water bath to form vapor and introduced into the gas inlet pipe connected to the reaction vessel. The temperature is raised to 100°C and the gas inlet pipe is opened at the same time to allow the vapor to contact the branched polyethylene particles and react for 2 hours to obtain low crystallinity HDPE. S4. By weight, low-crystallinity HDPE, HDPE, polypropylene (PP) and antioxidant (antioxidant 1010) are mixed evenly and then added to a twin-screw extruder for melt extrusion granulation. The temperatures of each zone of the twin-screw extruder are 150℃, 155℃, 160℃, 160℃, 160℃, 165℃, 165℃, 165℃, 170℃, and 170℃, and the die head temperature is 170℃. After the product is pre-plasticized, cooled and granulated, the preparation process is completed, and high-haze HDPE composite material is obtained.

[0024] Specifically, the method for preparing this high-haze HDPE composite material provided by the present invention includes the following steps: Step S1 involves pre-irradiating HDPE with gamma rays to generate free radical active sites on its molecular chains, laying the foundation for subsequent grafting reactions; Step S2 involves immersing the irradiated HDPE in a specific multifunctional monomer solution, where these monomers can undergo graft polymerization at the active sites, introducing long branches into the HDPE chains. This makes the polymer chains loose and irregular, creating conditions for the next step of disrupting crystallization; and then Step S3 involves vaporizing small-molecule amorphous substances under vacuum and heating conditions. In this process, these small molecules can penetrate into the loosely structured amorphous regions of HDPE after grafting, partially inserting into the lattice boundaries, effectively interfering with and disrupting the regular arrangement of polyethylene chains, and significantly reducing its crystallinity. In the final step S4, the prepared low-crystallinity HDPE is blended with polypropylene and ordinary HDPE. Since HDPE and PP are incompatible, a large number of phase interfaces will be formed during the melt blending process. The presence of low-crystallinity HDPE makes the phase region size and interface morphology more complex and finer. These numerous tiny phase interfaces become light scattering centers, thus exhibiting a high haze effect on a macroscopic scale.

[0025] Example 2

[0026] This embodiment 2 provides a high-haze HDPE composite material, which includes the following components in parts by weight: 100 parts matrix material, 10 parts polypropylene, 38 parts monomer, 19 parts small molecule amorphous substance and 0.5 parts antioxidant; the matrix material is composed of 10 parts low crystallinity HDPE and 90 parts HDPE. The preparation method of this high-haze HDPE composite material includes the following specific steps: S1. Irradiation treatment: High-density polyethylene (HDPE) is subjected to gamma ray irradiation treatment to obtain pre-irradiated polyethylene; S2. Preparation of branched polyethylene: Pre-irradiated polyethylene was immersed in a monomer solution (obtained by dissolving tripropylene glycol diacrylate in ether) and sealed for 35 hours. Then it was taken out and placed in a high-temperature reactor and reacted at the first temperature (130°C) and under air conditions for 20 minutes. After the reaction was completed, it was filtered, washed and dried to obtain branched polyethylene. S3. Preparation of low crystallinity HDPE: Branched polyethylene is placed in a reaction vessel and vacuumed. Small molecule amorphous substance (isopentane) is heated in a water bath to form vapor and introduced into the gas inlet pipe connected to the reaction vessel. The temperature is raised to 150°C and the gas inlet pipe is opened at the same time to allow the vapor to contact the branched polyethylene particles and react for 3 hours to obtain low crystallinity HDPE. S4. By weight, low-crystallinity HDPE, HDPE, polypropylene (PP) and antioxidant (antioxidant DLTP) are mixed evenly and then added to a twin-screw extruder for melt extrusion granulation. The temperatures of each zone of the twin-screw extruder are 150℃, 155℃, 160℃, 160℃, 160℃, 165℃, 165℃, 170℃, and 170℃, and the die head temperature is 170℃. After the product is pre-plasticized, cooled and pelletized, the preparation process is completed, and high-haze HDPE composite material is obtained.

[0027] Example 3

[0028] This embodiment 3 provides a high-haze HDPE composite material, which comprises the following components in parts by weight: 100 parts matrix material, 7 parts polypropylene, 25 parts monomer, 14 parts small molecule amorphous substance and 0.3 parts antioxidant; the matrix material is composed of 15 parts low crystallinity HDPE and 85 parts HDPE. The preparation method of this high-haze HDPE composite material includes the following specific steps: S1. Irradiation treatment: High-density polyethylene (HDPE) is subjected to gamma ray irradiation treatment to obtain pre-irradiated polyethylene; S2. Preparation of branched polyethylene: Pre-irradiated polyethylene was immersed in a monomer solution (obtained by dissolving N,N'-methylenebisacrylamide in water) and sealed for 18 hours. After that, it was taken out and placed in a high-temperature reactor and reacted at the first temperature (100°C) and under air conditions for 16 minutes. After the reaction was completed, it was filtered, washed, and dried to obtain branched polyethylene. S3. Preparation of low crystallinity HDPE: Branched polyethylene is placed in a reactor and vacuum is drawn. Small molecule amorphous substance (ethylene) is heated in a water bath to form vapor and introduced into the air inlet pipe connected to the reactor. The temperature is raised to 70°C and the air inlet pipe is opened at the same time to allow the vapor to contact the branched polyethylene particles and react for 1.5 hours to obtain low crystallinity HDPE. S4. By weight, low-crystallinity HDPE, HDPE, polypropylene (PP) and antioxidant (antioxidant TNP) are mixed evenly and then added to a twin-screw extruder for melt extrusion granulation. The temperatures of each zone of the twin-screw extruder are 150℃, 155℃, 160℃, 160℃, 160℃, 165℃, 165℃, 170℃, and 170℃, and the die head temperature is 170℃. After the product is pre-plasticized, cooled and pelletized, the preparation process is completed, and high-haze HDPE composite material is obtained.

[0029] Example 4

[0030] This embodiment 4 provides a high-haze HDPE composite material, which comprises the following components in parts by weight: 100 parts matrix material, 8.5 parts polypropylene, 33 parts monomer, 17 parts small molecule amorphous substance and 0.4 parts antioxidant; the matrix material is composed of 20 parts low crystallinity HDPE and 80 parts HDPE. The preparation method of this high-haze HDPE composite material includes the following specific steps: S1. Irradiation treatment: High-density polyethylene (HDPE) is subjected to gamma ray irradiation treatment to obtain pre-irradiated polyethylene; S2. Preparation of branched polyethylene: Pre-irradiated polyethylene was immersed in a monomer solution (obtained by dissolving diethylene glycol diacrylate in ketone) and sealed for 12 hours. Then it was taken out and placed in a high-temperature reactor and reacted at the first temperature (110°C) and under air conditions for 18 minutes. After the reaction was completed, it was filtered, washed and dried to obtain branched polyethylene. S3. Preparation of low crystallinity HDPE: Branched polyethylene is placed in a reaction vessel and vacuumed. Small molecule amorphous substance (n-hexane) is heated in a water bath to form vapor and introduced into the gas inlet pipe connected to the reaction vessel. The temperature is raised to 180°C and the gas inlet pipe is opened at the same time to allow the vapor to contact the branched polyethylene particles and react for 1 hour to obtain low crystallinity HDPE. S4. By weight, low-crystallinity HDPE, HDPE, polypropylene (PP) and antioxidant (antioxidant 1076) are mixed evenly and then added to a twin-screw extruder for melt extrusion granulation. The temperatures of each zone of the twin-screw extruder are 150℃, 155℃, 160℃, 160℃, 160℃, 165℃, 165℃, 170℃, and 170℃, and the die head temperature is 170℃. After the product is pre-plasticized, cooled and pelletized, the preparation process is completed, and high-haze HDPE composite material is obtained.

[0031] Comparative Example 1

[0032] The difference between Comparative Example 1 and Example 2 is that the matrix material in Comparative Example 1 is all ordinary HDPE. Apart from that, the selection and amount of other raw materials are the same as in Example 2, and the preparation method and conditions are the same as in Example 2.

[0033] Comparative Example 2

[0034] The difference between Comparative Example 2 and Example 2 is that no polypropylene (PP) is added to the composite material component of Comparative Example 2. Otherwise, the selection and amount of other raw materials are the same as those in Example 2, and the preparation method and conditions are the same as those in Example 2.

[0035] Comparative Example 3

[0036] The difference between Comparative Example 3 and Example 2 is that Comparative Example 3 does not add small molecule amorphous substances during the preparation of low crystallinity HDPE (equivalent to directly mixing branched polyethylene with HDPE, polypropylene and antioxidant). Apart from that, the selection and amount of other raw materials are the same as in Example 2, and the preparation method and conditions are the same as in Example 2.

[0037] Comparative Example 4

[0038] The difference between Comparative Example 4 and Example 2 is that no monomer is added in the preparation process of low crystallinity HDPE in Comparative Example 4 (equivalent to directly reacting pre-irradiated polyethylene with small molecule amorphous substance vapor). Apart from this, the selection and amount of other raw materials are the same as in Example 2, and the preparation method and conditions are the same as in Example 2.

[0039] Comparative Example 5

[0040] The difference between Comparative Example 5 and Example 2 is that Comparative Example 5 does not add monomers and small molecule amorphous substances during the preparation of low crystallinity HDPE. Apart from this, the selection and amount of other raw materials are the same as in Example 2, and the preparation method and conditions are the same as in Example 2.

[0041] Comparative Example 6

[0042] The difference between Comparative Example 6 and Example 2 is that Comparative Example 6 does not irradiate HDPE during the preparation of low crystallinity HDPE. Apart from that, the selection and amount of other raw materials are the same as in Example 2, and the preparation method and conditions are the same as in Example 2.

[0043] Performance testing: After drying the HDPE composite materials obtained in Examples 1-4 and Comparative Examples 1-6 at 100°C for 24 hours, they were injection molded into specimens according to the experimental requirements using an injection molding machine at a temperature of 185-205°C. Subsequently, notched impact strength, tensile strength, elongation at break, haze, and light transmittance were tested, and the results are shown in Table 1 below.

[0044] Table 1 shows the performance test results of the HDPE composite materials in Examples 1-4 and Comparative Examples 1-6.

[0045] In Table 1, the notched impact strength at 23℃ and -20℃ were tested according to standard GB / T 1043; the tensile strength and elongation at break were tested according to standard GB / T 1040, with a tensile rate of 20 mm / min; the haze and transmittance were tested according to standard GB / T 2410, with sample sizes of 2.0 mm × 100 mm × 100 mm and 1.0 mm × 100 mm × 100 mm square plates.

[0046] The above-described preferred embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of the invention. Any obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A high-haze HDPE composite material, characterized in that, The composite material comprises the following components in parts by weight: 100 parts matrix material, 5-10 parts polypropylene, 20-40 parts monomer, 10-20 parts small molecule amorphous substance, and 0.1-0.5 parts antioxidant. The matrix material is composed of low-crystallinity HDPE and HDPE, and the weight percentage of low-crystallinity HDPE in the matrix material is 5-20%.

2. The high-haze HDPE composite material according to claim 1, characterized in that, The monomer is selected from one or more of trimethylolpropane triacrylate, tripropylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, trivinylbenzene, divinylbenzene, and N,N'-methylenebisacrylamide.

3. The high-haze HDPE composite material according to claim 1, characterized in that, The small molecule amorphous substance is selected from one or more of ethylene, n-hexane, and isopentane.

4. The high-haze HDPE composite material according to claim 1, characterized in that, The antioxidant is selected from one or more of the following: antioxidant DLTP, antioxidant TPP, antioxidant TNP, antioxidant CA, antioxidant 330, antioxidant 164, antioxidant 1010, and antioxidant 1076.

5. A method for preparing a high-haze HDPE composite material according to any one of claims 1 to 4, characterized in that, The method includes the following steps: S1. Irradiation treatment: HDPE is irradiated to obtain pre-irradiated polyethylene; S2. Preparation of branched polyethylene: Pre-irradiated polyethylene is immersed in a monomer solution, taken out and reacted at the first temperature, then filtered, washed and dried to obtain branched polyethylene. S3. Preparation of low-crystallinity HDPE: Under vacuum conditions, small-molecule amorphous substances are introduced into a reaction vessel containing the branched polyethylene in the form of vapor to carry out the reaction, thereby obtaining low-crystallinity HDPE. S4. After uniformly mixing the low-crystallinity HDPE, HDPE, polypropylene and antioxidant, the mixture is melt-extruded and granulated to obtain a high-haze HDPE composite material.

6. The method for preparing a high-haze HDPE composite material according to claim 5, characterized in that, In step S1, HDPE is irradiated with gamma rays.

7. The method for preparing a high-haze HDPE composite material according to claim 5, characterized in that, The soaking time in step S2 is 12 to 36 hours, the first reaction temperature is 100 to 150°C, and the reaction time is 15 to 20 minutes.

8. The method for preparing a high-haze HDPE composite material according to claim 5, characterized in that, In step S3, the small molecule amorphous substance is heated in a water bath to form vapor. The reaction temperature is 50-200℃ and the reaction time is 1-3 hours.

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