Flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foaming material and preparation method thereof

Abstract

The present application relates to a kind of flame-retardant anti-shrinkage PBAT / bamboo powder supercritical foaming material and its preparation method, belong to degradable foaming material technical field.To solve the problem that PBAT system introduces bamboo powder and flame retardant causes foaming material cell structure uneven, density uneven, mechanical property drops, the present application provides a kind of flame-retardant anti-shrinkage PBAT / bamboo powder supercritical foaming material, component includes PBAT, bamboo powder and flame retardant, melt extrusion granulation after being placed in airtight container, fills in supercritical gas and is foamed to be prepared.The present application improves the anti-shrinkage and flame-retardant performance of PBAT foaming material by the addition of bamboo powder and flame retardant;By optimizing the injection amount of supercritical gas, foaming temperature and pressure, reduce foaming instability, effectively offset the adverse effects of bamboo powder and flame retardant on cell growth, obtain uniform cell structure and density, further improve the mechanical property of material.

Description

Technical Field

[0001] This invention belongs to the field of biodegradable foam materials technology, and particularly relates to a flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foam material and its preparation method. Background Technology

[0002] High-performance polybutylene adipate (PBAT) is a thermoplastic, fully biodegradable plastic that can be broken down by microorganisms in the natural environment, ultimately reducing it to carbon dioxide and water, effectively reducing plastic pollution. PBAT foam is an ideal alternative to traditional petroleum-based foams in packaging, construction, and other applications. However, the linear structure and low molecular weight of PBAT cause it to shrink easily after foaming, and the severe shrinkage and flammability issues of PBAT foam limit its applications.

[0003] To address the shrinkage issue of PBAT foam, inorganic fillers can be added to enhance its rigidity and reduce shrinkage. Bamboo powder, a natural, renewable, and widely available material, has been incorporated into the PBAT system. The addition of bamboo powder not only partially replaces petroleum-based raw materials, reducing costs, but its porous structure and natural fiber properties also inhibit foam shrinkage to some extent. Adding flame retardants is the primary method for improving the flame retardancy of PBAT foam. However, the addition of bamboo powder and flame retardants affects the melt flowability and cell stability of PBAT, adversely impacting the foaming process and leading to problems such as uneven cell structure, uneven density, and decreased mechanical properties in the foamed material. Summary of the Invention

[0004] To address the issues of uneven cell structure, uneven density, and decreased mechanical properties in foamed materials caused by the introduction of bamboo powder and flame retardants into the PBAT system, this invention provides a flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foamed material and its preparation method.

[0005] The technical solution of the present invention:

[0006] A flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foam material comprises the following components in parts by weight: 80-100 parts PBAT, 5-20 parts bamboo powder, and 20-50 parts flame retardant.

[0007] Furthermore, the PBAT has a melt index of 2.5~5g / 10min and a melting point of 115~123℃; the bamboo powder has a particle size of 1000~1200 mesh; and the flame retardant is aluminum hypophosphite or magnesium hypophosphite hexahydrate.

[0008] A method for preparing a flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foaming material, comprising the following steps:

[0009] Step 1: After drying PBAT, bamboo powder and flame retardant, mix them, melt extrude and granulate to obtain blended granules;

[0010] Step 2: Hot press the blended granules obtained in Step 1 into a block of blended material;

[0011] Step 3: Place the blended block obtained in Step 2 into a sealed container, fill it with supercritical gas, and complete the foaming under certain temperature and pressure. After depressurization, cool it to obtain flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foamed material.

[0012] Furthermore, the drying process described in step one is carried out at a temperature of 60-80°C for 6-12 hours.

[0013] Furthermore, in step one, a twin-screw extruder is used for melt extrusion. The temperature of the twin-screw extruder is 135~165℃, the main extruder speed is 30~50rpm, and the feeder speed is 20~40rpm.

[0014] Furthermore, in step two, the hot pressing pressure is 10 MPa, the hot pressing temperature is 165°C, and the hot pressing time is 10 min.

[0015] Furthermore, the thickness of the blend block obtained in step two is 4~10mm, the length is 10~30mm, and the width is 10~30mm.

[0016] Furthermore, the sealed container in step three is a high-pressure reactor, the supercritical gas is supercritical carbon dioxide, and the charging amount of supercritical carbon dioxide is 8~25 MPa.

[0017] Furthermore, in step three, the foaming temperature is 80~120℃, the foaming pressure is 8~16MPa, and the foaming time is 30~120min.

[0018] Furthermore, the depressurization time described in step three is 2-5 seconds.

[0019] The beneficial effects of this invention are:

[0020] This invention synergistically enhances the shrinkage resistance and flame retardant properties of PBAT foam materials through the addition of bamboo powder and flame retardants, achieving both physical and chemical improvements. Supercritical carbon dioxide, as a foaming agent, exhibits high solubility and rapid diffusion in polymers, allowing it to uniformly penetrate the interface between bamboo powder and flame retardant particles, effectively reducing its localized interference with the polymer melt flowability. Simultaneously, during supercritical carbon dioxide foaming, the porous structure and natural fiber properties of bamboo powder contribute to the uniform distribution and rapid diffusion of CO2, while the presence of the flame retardant forms a denser carbon layer structure during foaming, further improving the foam's flame retardant properties and achieving a synergistic performance enhancement.

[0021] This invention, by adjusting and optimizing the injection amount of supercritical carbon dioxide, foaming temperature, and pressure, avoids the damage to the thermal stability of flame retardants and the structure of bamboo powder fibers caused by high temperature and high pressure environments. This reduces foaming instability caused by changes in material properties, effectively offsets the adverse effects of the bamboo powder fiber network and flame retardants on cell growth, and obtains a uniform cell structure and density, further improving the mechanical properties of the material. This provides strong support for the preparation of high-performance, environmentally friendly PBAT foam materials.

[0022] The supercritical carbon dioxide foaming process used in this invention leaves no residue, is environmentally friendly, and the CO2 is recyclable, reducing production costs. This aligns with the renewable nature of bamboo powder and the environmental requirements of halogen-free flame retardants, and conforms to the concept of green and sustainable development. Attached Figure Description

[0023] Figure 1 The images show the appearance of Example 2 before foaming, immediately after foaming, and after being placed at room temperature and pressure for 7 days. a is before foaming, b is immediately after foaming, and c is after being placed for 7 days.

[0024] Figure 2 The images show the appearance of Comparative Example 1 before foaming, immediately after foaming, and after being placed at room temperature and pressure for 7 days. a is before foaming, b is immediately after foaming, and c is after being placed for 7 days.

[0025] Figure 3 SEM image of the foamed material prepared in Example 2;

[0026] Figure 4 SEM image of the foamed material prepared in Comparative Example 1;

[0027] Figure 5 The image shows a vertical combustion diagram of the foamed material prepared in Comparative Example 2.

[0028] Figure 6 The image shows a vertical combustion diagram of the foamed material prepared in Example 2.

[0029] Figure 7 The image shows a vertical combustion diagram of the foamed material prepared in Example 3.

[0030] Figure 8 The image shows a vertical combustion diagram of the foamed material prepared in Example 4.

[0031] Figure 9 The image shows the carbon residue after combustion of the foamed material prepared in Example 2 using a cone calorimeter.

[0032] Figure 10 The image shows the carbon residue after combustion of the foamed material prepared in Comparative Example 2 using a cone calorimeter. Detailed Implementation

[0033] The technical solution of the present invention will be further described below with reference to embodiments, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention. In the following embodiments, the process equipment or apparatus not specifically specified are all conventional equipment or apparatus in the art. Unless otherwise specified, the raw materials used in the embodiments of the present invention are all commercially available; unless otherwise specified, the technical means used in the embodiments of the present invention are all conventional means well known to those skilled in the art.

[0034] Example 1

[0035] This embodiment provides a flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foaming material, which is made of 85g PBAT, 15g bamboo powder and 20g flame retardant aluminum hypophosphite.

[0036] The PBAT used in this embodiment was purchased from Xinjiang Lanshan Tunhe Technology Co., Ltd., with the brand name TH801T, a melt index of 2.5~5g / 10min, and a melting point of 115~123℃; the bamboo powder was purchased from Sichuan Green Bamboo Plant Fiber Co., Ltd., with a particle size of 1000-1200 mesh; the flame retardant aluminum hypophosphite was purchased from Guangdong Baishi Chemical Technology Co., Ltd.; and the carbon dioxide gas was purchased from Harbin Qinghua Gas Industry Co., Ltd., with a concentration of 99.99%.

[0037] The preparation method of the flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foaming material in this embodiment is as follows:

[0038] Step 1: After drying PBAT, bamboo powder and flame retardant at 80℃ for 6 hours, mix them, melt extrude and pelletize them using a twin-screw extruder. The temperature of the twin-screw extruder is 150℃, the main machine speed is 50 rpm, and the feeder speed is 40 rpm to obtain blended granules.

[0039] Step 2: The blended granules obtained in Step 1 are hot-pressed for 10 min at a pressure of 10 MPa and a hot-pressing temperature of 165℃ using a flat vulcanizing apparatus to obtain a blended block with a thickness of 4 mm, a length of 20 mm, and a width of 20 mm.

[0040] Step 3: Place the blended block obtained in Step 2 into a high-pressure reactor, fill it with 15MPa supercritical carbon dioxide, and foam it at 100℃ and 15MPa for 60 min. Depressurize and cool within 3s to obtain flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foamed material.

[0041] Example 2

[0042] This embodiment provides a flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foaming material, which is made of 85g PBAT, 15g bamboo powder and 30g flame retardant aluminum hypophosphite.

[0043] The PBAT used in this embodiment was purchased from Xinjiang Lanshan Tunhe Technology Co., Ltd., with the grade TH801T, a melt index of 2.5~5g / 10min, and a melting point of 115~123℃; the bamboo powder was purchased from Sichuan Green Bamboo Plant Fiber Co., Ltd., with a particle size of 1000-1200 mesh; the flame retardant was aluminum hypophosphite from Guangdong Baishi Chemical Technology Co., Ltd.; and the carbon dioxide gas was purchased from Harbin Qinghua Gas Industry Co., Ltd., with a concentration of 99.99%.

[0044] The preparation method of the flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foaming material in this embodiment is as follows:

[0045] Step 1: After drying PBAT, bamboo powder and flame retardant at 80℃ for 6 hours, mix them, melt extrude and pelletize them using a twin-screw extruder. The temperature of the twin-screw extruder is 150℃, the main machine speed is 50 rpm, and the feeder speed is 40 rpm to obtain blended granules.

[0046] Step 2: The blended granules obtained in Step 1 are hot-pressed for 10 min at a pressure of 10 MPa and a hot-pressing temperature of 165℃ using a flat vulcanizing apparatus to obtain a blended block with a thickness of 4 mm, a length of 20 mm, and a width of 20 mm.

[0047] Step 3: Place the blended block obtained in Step 2 into a high-pressure reactor, fill it with 15MPa supercritical carbon dioxide, and foam it at 100℃ and 15MPa for 60 minutes. Depressurize and cool within 3 seconds to obtain flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foamed material.

[0048] Example 3

[0049] This embodiment provides a flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foaming material, which is made of 85g PBAT, 15g bamboo powder and 40g flame retardant aluminum hypophosphite.

[0050] The PBAT used in this embodiment was purchased from Xinjiang Lanshan Tunhe Technology Co., Ltd., with the grade TH801T, a melt index of 2.5~5g / 10min, and a melting point of 115~123℃; the bamboo powder was purchased from Sichuan Green Bamboo Plant Fiber Co., Ltd., with a particle size of 1000-1200 mesh; the flame retardant was aluminum hypophosphite from Guangdong Baishi Chemical Technology Co., Ltd.; and the carbon dioxide gas was purchased from Harbin Qinghua Gas Industry Co., Ltd., with a concentration of 99.99%.

[0051] The preparation method of the flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foaming material in this embodiment is as follows:

[0052] Step 1: After drying PBAT, bamboo powder and flame retardant at 80℃ for 6 hours, mix them, melt extrude and pelletize them using a twin-screw extruder. The temperature of the twin-screw extruder is 150℃, the main machine speed is 50 rpm, and the feeder speed is 40 rpm to obtain blended granules.

[0053] Step 2: The blended granules obtained in Step 1 are hot-pressed for 10 minutes under a pressure of 10MPa and a hot-pressing temperature of 165℃ using a flat vulcanizing apparatus to obtain a blended block with a thickness of 4mm, a length of 20mm, and a width of 20mm.

[0054] Step 3: Place the blended block obtained in Step 2 into a high-pressure reactor, fill it with 15MPa supercritical carbon dioxide, and foam it at 100℃ and 15MPa for 60 minutes. Depressurize and cool within 3 seconds to obtain flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foamed material.

[0055] Example 4

[0056] This embodiment provides a flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foaming material, which is made of 85g PBAT, 15g bamboo powder and 50g flame retardant aluminum hypophosphite.

[0057] The PBAT used in this embodiment was purchased from Xinjiang Lanshan Tunhe Technology Co., Ltd., with the brand name TH801T, a melt index of 2.5~5g / 10min, and a melting point of 115~123℃; the bamboo powder was purchased from Sichuan Green Bamboo Plant Fiber Co., Ltd., with a particle size of 1000-1200 mesh; the flame retardant aluminum hypophosphite was purchased from Guangdong Baishi Chemical Technology Co., Ltd.; and the carbon dioxide gas was purchased from Harbin Qinghua Gas Industry Co., Ltd., with a concentration of 99.99%.

[0058] The preparation method of the flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foaming material in this embodiment is as follows:

[0059] Step 1: After drying PBAT, bamboo powder and flame retardant at 80℃ for 6 hours, mix them, melt extrude and pelletize them using a twin-screw extruder. The temperature of the twin-screw extruder is 150℃, the main machine speed is 50 rpm, and the feeder speed is 40 rpm to obtain blended granules.

[0060] Step 2: The blended granules obtained in Step 1 are hot-pressed for 10 minutes under a pressure of 10MPa and a hot-pressing temperature of 165℃ using a flat vulcanizing apparatus to obtain a blended block with a thickness of 4mm, a length of 20mm, and a width of 20mm.

[0061] Step 3: Place the blended block obtained in Step 2 into a high-pressure reactor, fill it with 15MPa supercritical carbon dioxide, and foam it at 100℃ and 15MPa for 60 minutes. Depressurize and cool within 3 seconds to obtain flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foamed material.

[0062] Example 5

[0063] This embodiment provides a flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foaming material, which is made of 85g PBAT, 15g bamboo powder and 50g flame retardant aluminum hypophosphite.

[0064] The PBAT used in this embodiment was purchased from Xinjiang Lanshan Tunhe Technology Co., Ltd., with the brand name TH801T, a melt index of 2.5~5g / 10min, and a melting point of 115~123℃; the bamboo powder was purchased from Sichuan Green Bamboo Plant Fiber Co., Ltd., with a particle size of 1000-1200 mesh; the flame retardant aluminum hypophosphite was purchased from Guangdong Baishi Chemical Technology Co., Ltd.; and the carbon dioxide gas was purchased from Harbin Qinghua Gas Industry Co., Ltd., with a concentration of 99.99%.

[0065] The preparation method of the flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foaming material in this embodiment is as follows:

[0066] Step 1: After drying PBAT, bamboo powder and flame retardant at 80℃ for 6 hours, mix them, melt extrude and pelletize them using a twin-screw extruder. The temperature of the twin-screw extruder is 150℃, the main machine speed is 50 rpm, and the feeder speed is 40 rpm to obtain blended granules.

[0067] Step 2: The blended granules obtained in Step 1 are hot-pressed for 10 minutes under a pressure of 10MPa and a hot-pressing temperature of 165℃ using a flat vulcanizing apparatus to obtain a blended block with a thickness of 4mm, a length of 20mm, and a width of 20mm.

[0068] Step 3: Place the blended block obtained in Step 2 into a high-pressure reactor, fill it with 15MPa supercritical carbon dioxide, and foam it at 80℃ and 15MPa for 60 min. Depressurize and cool within 3s to obtain flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foamed material.

[0069] Example 6

[0070] This embodiment provides a flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foaming material, which is made of 85g PBAT, 15g bamboo powder and 50g flame retardant aluminum hypophosphite.

[0071] The PBAT used in this embodiment was purchased from Xinjiang Lanshan Tunhe Technology Co., Ltd., with the brand name TH801T, a melt index of 2.5~5g / 10min, and a melting point of 115~123℃; the bamboo powder was purchased from Sichuan Green Bamboo Plant Fiber Co., Ltd., with a particle size of 1000-1200 mesh; the flame retardant aluminum hypophosphite was purchased from Guangdong Baishi Chemical Technology Co., Ltd.; and the carbon dioxide gas was purchased from Harbin Qinghua Gas Industry Co., Ltd., with a concentration of 99.99%.

[0072] The preparation method of the flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foaming material in this embodiment is as follows:

[0073] Step 1: After drying PBAT, bamboo powder and flame retardant at 80℃ for 6 hours, mix them, melt extrude and pelletize them using a twin-screw extruder. The temperature of the twin-screw extruder is 150℃, the main machine speed is 50 rpm, and the feeder speed is 40 rpm to obtain blended granules.

[0074] Step 2: The blended granules obtained in Step 1 are hot-pressed for 10 minutes under a pressure of 10MPa and a hot-pressing temperature of 165℃ using a flat vulcanizing apparatus to obtain a blended block with a thickness of 4mm, a length of 20mm, and a width of 20mm.

[0075] Step 3: Place the blended block obtained in Step 2 into a high-pressure reactor, fill it with 15MPa supercritical carbon dioxide, and foam it at 90℃ and 15MPa for 60 minutes. Depressurize and cool within 3 seconds to obtain flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foamed material.

[0076] Example 7

[0077] This embodiment provides a flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foaming material, which is made of 85g PBAT, 15g bamboo powder and 50g flame retardant aluminum hypophosphite.

[0078] The PBAT used in this embodiment was purchased from Xinjiang Lanshan Tunhe Technology Co., Ltd., with the brand name TH801T, a melt index of 2.5~5g / 10min, and a melting point of 115~123℃; the bamboo powder was purchased from Sichuan Green Bamboo Plant Fiber Co., Ltd., with a particle size of 1000-1200 mesh; the flame retardant aluminum hypophosphite was purchased from Guangdong Baishi Chemical Technology Co., Ltd.; and the carbon dioxide gas was purchased from Harbin Qinghua Gas Industry Co., Ltd., with a concentration of 99.99%.

[0079] The preparation method of the flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foaming material in this embodiment is as follows:

[0080] Step 1: After drying PBAT, bamboo powder and flame retardant at 80℃ for 6 hours, mix them, melt extrude and pelletize them using a twin-screw extruder. The temperature of the twin-screw extruder is 150℃, the main machine speed is 50 rpm, and the feeder speed is 40 rpm to obtain blended granules.

[0081] Step 2: The blended granules obtained in Step 1 are hot-pressed for 10 minutes under a pressure of 10MPa and a hot-pressing temperature of 165℃ using a flat vulcanizing apparatus to obtain a blended block with a thickness of 4mm, a length of 20mm, and a width of 20mm.

[0082] Step 3: Place the blended block obtained in Step 2 into a high-pressure reactor, fill it with 15MPa supercritical carbon dioxide, and foam it at 110℃ and 15MPa for 60 minutes. Depressurize and cool within 3 seconds to obtain flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foamed material.

[0083] Example 8

[0084] This embodiment provides a flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foaming material, which is made of 85g PBAT, 15g bamboo powder and 50g flame retardant aluminum hypophosphite.

[0085] The PBAT used in this embodiment was purchased from Xinjiang Lanshan Tunhe Technology Co., Ltd., with the brand name TH801T, a melt index of 2.5~5g / 10min, and a melting point of 115~123℃; the bamboo powder was purchased from Sichuan Green Bamboo Plant Fiber Co., Ltd., with a particle size of 1000-1200 mesh; the flame retardant aluminum hypophosphite was purchased from Guangdong Baishi Chemical Technology Co., Ltd.; and the carbon dioxide gas was purchased from Harbin Qinghua Gas Industry Co., Ltd., with a concentration of 99.99%.

[0086] The preparation method of the flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foaming material in this embodiment is as follows:

[0087] Step 1: After drying PBAT, bamboo powder and flame retardant at 80℃ for 6 hours, mix them, melt extrude and pelletize them using a twin-screw extruder. The temperature of the twin-screw extruder is 150℃, the main machine speed is 50 rpm, and the feeder speed is 40 rpm to obtain blended granules.

[0088] Step 2: The blended granules obtained in Step 1 are hot-pressed for 10 minutes under a pressure of 10MPa and a hot-pressing temperature of 165℃ using a flat vulcanizing apparatus to obtain a blended block with a thickness of 4mm, a length of 20mm, and a width of 20mm.

[0089] Step 3: Place the blended block obtained in Step 2 into a high-pressure reactor, fill it with 15MPa supercritical carbon dioxide, and foam it at 120℃ and 15MPa for 60 minutes. Depressurize and cool within 3 seconds to obtain flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foamed material.

[0090] Comparative Example 1

[0091] This comparative example provides a pure PBAT foam material made from 100g of PBAT.

[0092] The PBAT used in this comparative example was purchased from Xinjiang Lanshan Tunhe Technology Co., Ltd., with the grade TH801T, a melt index of 2.5~5g / 10min, and a melting point of 115~123℃.

[0093] The preparation steps of pure PBAT foam material are as follows:

[0094] Step 1: After drying PBAT at 80℃ for 6 hours, mix it, melt extrude it using a twin-screw extruder, and then pelletize it. The temperature of the twin-screw extruder is 150℃, the main extruder speed is 50 rpm, and the feeder speed is 40 rpm to obtain pellets.

[0095] Step 2: The granules obtained in Step 1 are hot-pressed for 10 minutes under a pressure of 10MPa and a hot-pressing temperature of 165℃ using a flat vulcanizing apparatus to obtain a block material with a thickness of 4mm, a length of 20mm, and a width of 20mm.

[0096] Step 3: Place the block material obtained in Step 2 into a high-pressure reactor, fill it with 15MPa supercritical carbon dioxide, and foam it at 110℃ and 15MPa for 60 minutes. Depressurize and cool within 3 seconds to obtain pure PBAT supercritical foam material.

[0097] Comparative Example 2

[0098] This comparative example provides a PBAT / bamboo powder foam material made of 85g PBAT and 15g bamboo powder.

[0099] The PBAT used in this comparative example was purchased from Xinjiang Lanshan Tunhe Technology Co., Ltd., with the grade TH801T, a melt index of 2.5~5g / 10min, and a melting point of 115~123℃; the bamboo powder was purchased from Sichuan Green Bamboo Plant Fiber Co., Ltd., with a particle size of 1000-1200 mesh.

[0100] The preparation steps of this comparative example PBAT / bamboo powder foam material are as follows:

[0101] Step 1: After drying PBAT and bamboo powder at 80℃ for 6 hours, mix them, melt extrude and pelletize them using a twin-screw extruder. The temperature of the twin-screw extruder is 150℃, the main machine speed is 50 rpm, and the feeder speed is 40 rpm to obtain blended granules.

[0102] Step 2: The blended granules obtained in Step 1 are hot-pressed for 10 minutes under a pressure of 10MPa and a hot-pressing temperature of 165℃ using a flat vulcanizing apparatus to obtain a blended block with a thickness of 4mm, a length of 20mm, and a width of 20mm.

[0103] Step 3: Place the blended block obtained in Step 2 into a high-pressure reactor, fill it with 15MPa supercritical carbon dioxide, and foam it at 100℃ and 15MPa for 60 minutes. Depressurize and cool within 3 seconds to obtain PBAT / bamboo powder supercritical foamed material.

[0104] Comparative Example 3

[0105] This comparative example provides a flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foam material, made of 85g PBAT, 15g bamboo powder and 60g flame retardant aluminum hypophosphite.

[0106] The PBAT used in this comparative example was purchased from Xinjiang Lanshan Tunhe Technology Co., Ltd., with the grade TH801T, a melt index of 2.5~5g / 10min, and a melting point of 115~123℃; the bamboo powder was purchased from Sichuan Green Bamboo Plant Fiber Co., Ltd., with a particle size of 1000-1200 mesh; the flame retardant aluminum hypophosphite was purchased from Guangdong Baishi Chemical Technology Co., Ltd.; and the carbon dioxide gas was purchased from Harbin Qinghua Gas Industry Co., Ltd., with a concentration of 99.99%.

[0107] The preparation method of this comparative flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foam material is as follows:

[0108] Step 1: After drying PBAT, bamboo powder and flame retardant at 80℃ for 6 hours, mix them, melt extrude and pelletize them using a twin-screw extruder. The temperature of the twin-screw extruder is 150℃, the main machine speed is 50 rpm, and the feeder speed is 40 rpm to obtain blended granules.

[0109] Step 2: The blended granules obtained in Step 1 are hot-pressed for 10 minutes under a pressure of 10MPa and a hot-pressing temperature of 165℃ using a flat vulcanizing apparatus to obtain a blended block with a thickness of 4mm, a length of 20mm, and a width of 20mm.

[0110] Step 3: Place the blended block obtained in Step 2 into a high-pressure reactor, fill it with 15MPa supercritical carbon dioxide, and foam it at 100℃ and 15MPa for 60 minutes. Depressurize and cool within 3 seconds to obtain flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foamed material.

[0111] The performance of the foamed materials prepared in Examples 1-8 and Comparative Examples 1-3 was tested. The test methods and test conditions are as follows:

[0112] The foaming ratio of the material is calculated using the following formula:

[0113]

[0114] In the formula, ρ is the density of the material before foaming (g / cm³). 3 ), ρ f Density of the material after foaming (g / cm³) 3 ).

[0115] Cell morphology analysis: The morphology of the cells inside the foamed material was observed using a scanning electron microscope (SEM). Observations were performed at an accelerating voltage of 5 kV. The cell size was calculated from the SEM images using ImageJ software, and the cell density was calculated using the following formula.

[0116]

[0117] In the formula, N0 is the cell density (cells / cm²). 3 ), where n is the number of bubbles in the statistical region, and A is the area of ​​the statistical region (cm²). 2 ).

[0118] Compression performance test: The foam sample size was 10 mm × 10 mm × 10 mm, the compression rate was 5 mm / min, the maximum deformation was 50%, and the cycle was 10 times.

[0119] UL94 Vertical Burning Test: Foam sample size is 130 mm × 13 mm × 3.2 mm.

[0120] Limiting Oxygen Index (LOI) Test: The test standard is ASTM D2863, and the foam sample size is 100 mm × 10 mm × 10 mm.

[0121] Cone calorimetry test: The foam sample size was 100 mm × 100 mm × 10 mm, and the thermal radiation was 50 kW / m². 2 .

[0122] Test results are as follows Figures 1-10 As shown in Table 1.

[0123] Table 1

[0124]

[0125] from Figure 1 As can be seen from the data, in Example 2, the addition of bamboo powder and aluminum hypophosphite resulted in better foaming of the material, and the foamed material did not show significant shrinkage after being placed at room temperature and pressure for 7 days. Figure 2 It can be seen that Comparative Example 1 uses supercritical carbon dioxide to foam pure PBAT. When the foaming is just completed, the pure PBAT foam has a good appearance, but after 7 days, the surface wrinkles and the overall shrinkage is severe, with a shrinkage rate as high as 70.71%, making it impossible to measure the mechanical properties.

[0126] from Figure 3 It can be seen that Example 2 achieves a uniform cell structure. From Figure 4 It can be seen that the cell structure obtained in Comparative Example 1 has greater shrinkage. Furthermore, according to Table 1, the shrinkage rate and compressive strength results of Examples 1, 3, 4, Comparative Example 1, and Comparative Example 2 show that with the increase of the amount of flame retardant aluminum hypophosphite added, the foam shrinkage rate is significantly lower than that of Comparative Example 2, and is controlled within 2%, while the compressive strength of the foam increases. This indicates that bamboo powder and aluminum hypophosphite did not cause foaming instability due to changes in material composition during the foaming process, thus not adversely affecting cell growth. Simultaneously, the addition of bamboo powder and aluminum hypophosphite synergistically improves the shrinkage resistance and compressive strength of the PBAT foam material.

[0127] from Figure 5 As can be seen from the data, Comparative Example 2 was completely burned after only the first ignition during the vertical burning test, and had no flame retardant rating. Figure 6 Example 2 Figure 7 Example 3 and Figure 8 In the vertical combustion test, the foaming material of Example 4 was able to self-extinguish within 10 seconds after being ignited for the first and second time. Figure 9 The foamed material in Example 2 formed a dense layer of residual carbon after cone calorimetry testing, while Figure 10 The foamed material in Comparative Example 2 was almost completely burned off after the cone calorimetry test. Further analysis based on the corresponding limiting oxygen index and UL94 results in Table 1 indicates that the presence of flame retardant forms a denser char layer structure during the foaming process, further improving the flame retardant performance of the foam. However, excessive flame retardant can affect the foam expansion ratio, as seen in Comparative Example 3.

[0128] As shown in Table 1, in Examples 4-8, compared to Comparative Example 2, the foaming temperature has a significantly greater impact on the foam expansion ratio. This indicates that excessively high or low temperatures are detrimental to improving the foam expansion ratio. By adjusting and optimizing the injection amount of supercritical carbon dioxide, the foaming temperature, and the pressure, the damage to the thermal stability of the flame retardant and the bamboo fiber structure caused by the high-temperature and high-pressure environment was avoided, thereby obtaining foam with better overall performance.

[0129] The beneficial effects of this invention lie in the comprehensive improvement of PBAT foam material's shrinkage resistance, mechanical properties, and flame retardant properties achieved through the synergistic effect of bamboo powder and flame retardant, combined with supercritical carbon dioxide foaming technology. The specific synergistic mechanism and corresponding data phenomena are explained below:

[0130] 1. Synergistic anti-shrinkage and reinforcing mechanism of bamboo powder and flame retardant

[0131] The function of bamboo powder: Its porous structure and natural fiber properties help CO2 to be evenly distributed and diffused quickly, promote the formation of a uniform cell skeleton, and inhibit cell collapse.

[0132] The role of flame retardants: to promote the formation of a dense char layer during foaming, enhance the strength of the foam wall, and jointly resist shrinkage stress.

[0133] Data support: Comparative Example 1 (pure PBAT) had a shrinkage rate as high as 70.71%, while Examples 1-4 (with added bamboo powder and aluminum hypophosphite) had shrinkage rates controlled within 2%, and the compressive strength was significantly improved, proving that the two work together to stabilize the cell structure and enhance mechanical properties.

[0134] 2. Synergistic flame-retardant mechanism of bamboo powder and flame retardant

[0135] Physical barrier: The bamboo powder fiber and the flame retardant carbon layer form a dual physical barrier, which slows down the diffusion of pyrolysis gases.

[0136] Chemical flame retardants: Flame retardants generate phosphoric acid compounds at high temperatures, which catalyze the formation of char and isolate oxygen.

[0137] Data support: Comparative Example 2 has no flame retardant rating, while Examples 2-4 all achieve self-extinguishing upon removal of flame (UL94 V-0 rating). Furthermore, in the cone calorimetry test, Example 2 formed dense char residue. (See...) Figure 9 Comparative example 2 was almost completely burned out, see Figure 10 This demonstrates the synergistic flame-retardant effect.

[0138] 3. Process optimization ensures synergistic efficiency.

[0139] By controlling the amount of supercritical CO2 injected, temperature, and pressure, the high temperature and high pressure are avoided from damaging the bamboo powder fiber structure and the stability of the flame retardant, thus ensuring a stable foaming process.

[0140] Data support: Examples 4-8 show that foaming temperature has a significant impact on the expansion ratio. After optimization, a high expansion ratio and uniform cell structure are obtained. (See...) Figure 3 In contrast, the proportion of flame retardant in Comparative Example 3 decreased due to excessive flame retardant, highlighting the crucial role of process parameters in the synergistic effect.

[0141] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foaming material, characterized in that, The product comprises the following components in parts by weight: 80-100 parts PBAT, 5-20 parts bamboo powder, and 20-50 parts flame retardant; the PBAT has a melt flow index of 2.5-5 g / 10 min and a melting point of 115-123℃; the bamboo powder has a particle size of 1000-1200 mesh; and the flame retardant is aluminum hypophosphite or magnesium hypophosphite hexahydrate. The preparation method of the flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foaming material includes the following steps: Step 1: After drying PBAT, bamboo powder and flame retardant, mix them, melt extrude and granulate to obtain blended granules; Step 2: Hot press the blended granules obtained in Step 1 into a block of blended material; Step 3: Place the blended block obtained in Step 2 into a sealed container, fill it with 8~25MPa supercritical carbon dioxide, and complete the foaming at a temperature of 80~120℃ and a pressure of 8~16MPa for 30~120min. After depressurization for 2~5s, cool it to obtain flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foamed material.

2. The flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foaming material according to claim 1, characterized in that, The drying process described in step one is carried out at a temperature of 60-80℃ for 6-12 hours.

3. The flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foaming material according to claim 2, characterized in that, Step 1 involves melt extrusion using a twin-screw extruder. The temperature of the twin-screw extruder is 135~165℃, the main extruder speed is 30~50rpm, and the feeder speed is 20~40rpm.

4. The flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foaming material according to claim 3, characterized in that, The hot pressing pressure in step two is 10 MPa, the hot pressing temperature is 165°C, and the hot pressing time is 10 min.

5. The flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foaming material according to claim 4, characterized in that, The thickness of the blend block obtained in step two is 4~10mm, the length is 10~30mm, and the width is 10~30mm.

6. The flame-retardant and shrinkage-resistant PBAT / bamboo powder supercritical foaming material according to claim 5, characterized in that, The sealed container mentioned in step three is a high-pressure reactor.

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