Polymer foamed sheet material and method of making and use thereof

Abstract

The application discloses a kind of polymer foamed sheet and its preparation method and application, it is related to foamed material technical field.The preparation method of polymer foamed sheet provided in the application, first make the specific morphology of polymer microparticle mixing, hot-pressing sintering obtains the sheet with certain porosity, subsequently again foaming, the porosity in the sheet formed by sintering accelerates the diffusion of supercritical fluid, so that the present application can realize the rapid and efficient preparation of polymer foamed sheet, and the obtained foamed polymer sheet has abundant and size, distribution all has high uniformity bubble, and foaming ratio can reach more than 8.3 times, density is low, lightweight characteristics is excellent, with the prospect of large-scale application, simultaneously has good heat insulation characteristics, thermal conductivity is not higher than 0.09 W m ‑1 K ‑1 .

Description

Technical Field

[0001] This invention relates to the field of foamed materials technology, specifically to a polymer foamed board, its preparation method, and its application. Background Technology

[0002] Microporous foamed polymers hold an important position in the field of thermal insulation due to their ability to reduce heat convection through their internal pore structure. Among the many forms of foamed polymer materials, sheets are an extremely important type. After further processing, foamed polymer sheets can be used in sub-fields such as structural materials and cushioning materials.

[0003] Supercritical fluid foaming is a commonly used process for preparing foamed polymer sheets, offering advantages such as mild conditions and environmentally friendly processing. However, using supercritical fluid as a foaming agent requires impregnation of the polymer with the supercritical fluid before foaming. Supercritical fluid has a low diffusion rate in polymer sheets, requiring a long impregnation time. For example, Chinese patent CN 115124786A discloses that 50 mm thick PP sheets require 5 hours of supercritical fluid pressure impregnation before foaming. This significantly reduces the processing efficiency of the foamed sheets. Furthermore, the severely limited diffusion of supercritical fluid in polymer materials leads to common problems in existing polymer foamed sheets, such as uneven cell size and distribution, insufficient cell density, and inadequate expansion ratio. Uneven cell size and distribution can lead to decreased product consistency and difficulties in commercial application, while insufficient cell density can increase the density of the foamed material, potentially even resulting in a loss of lightweight properties. Insufficient expansion ratio has a significant negative impact on the thermal insulation performance of the resulting foamed sheets. Therefore, there is an urgent need to provide a new preparation process that enables the polymer foamed board to have good cell density, distribution and size uniformity, and excellent foaming ratio, while taking into account the foaming effect and having good thermal insulation performance. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for preparing polymer foamed boards. First, polymer microparticles with specific morphologies are mixed and hot-pressed to obtain a board with a certain porosity. Then, foaming is performed. The pores inside the sintered board accelerate the diffusion of supercritical fluid, resulting in the foamed polymer board obtained by this invention having abundant pores with high uniformity in size and distribution. At the same time, it has an excellent foaming ratio and good thermal insulation properties.

[0005] Another object of the present invention is to provide a polymer foamed board.

[0006] Another object of the present invention is to provide an application of polymer foamed board.

[0007] The above-mentioned objective of this invention is achieved through the following technical solution:

[0008] A method for preparing a polymer foamed board includes the following steps:

[0009] S1. Hot-pressing and sintering polymer rod-shaped microparticles to obtain a sintered plate; the diameter of the polymer rod-shaped microparticles is 0.3~2.8 mm, and the aspect ratio is 1~3; the hot-pressing and sintering temperature is T1 and satisfies T1-T2=10~50℃, where T2 is the Vicat softening temperature of the polymer rod-shaped microparticles; the porosity of the sintered plate is 3~25%;

[0010] S2. Place the sintered board obtained in step S1 into a mold, inject supercritical fluid for impregnation, and then depressurize and foam to obtain a polymer foamed board; the length of the sintered board in any three-dimensional direction is ≥0.1:1 to the length of the mold in the corresponding direction.

[0011] The method for preparing polymer foamed boards provided by this invention involves first hot-pressing and sintering polymer rod-shaped microparticles of a specific morphology into sintered boards with a porosity of 3-25% at a temperature not exceeding 50°C above the Vicat softening point. The pores in the sintered board accelerate the diffusion of supercritical fluid, thereby significantly reducing the impregnation time of the supercritical fluid and improving processing efficiency. This results in a foamed board with abundant pores and highly uniform pore distribution and size, while also increasing the foaming ratio of the polymer foamed board. Increasing the foaming ratio effectively enhances the thermal insulation performance of polymer foamed materials because a higher foaming ratio means a lower solid phase ratio and a higher gas phase ratio in the polymer foamed material, while the thermal conductivity of polymers typically exceeds 200 mW / m². -1 K -1 The thermal conductivity of air is only 26 mW / m. -1 K -1 Therefore, the polymer foamed board prepared by this invention can have lower thermal conductivity and better thermal insulation performance. At the same time, by limiting the size of the rod-shaped raw material particles, the cell size can be limited; smaller cell sizes can better block airflow, which also contributes to the reduction of thermal conductivity. Furthermore, the uniformity of cell size and distribution gives the foamed board prepared by this invention excellent consistency, which is beneficial for further applications, while the abundant and dense cells result in lower density and better lightweight properties.

[0012] Through extensive experimental research, the inventors of this application discovered that the morphology of the polymer particles before hot-pressing sintering and the hot-pressing sintering temperature in step S1 both play a crucial role in the foaming quality and expansion ratio. Specifically, the morphology of the polymer rod-shaped particles affects the shape of the internal pores of the board after the particles are stacked and hot-pressed to form a board. Therefore, if the size of the polymer rod-shaped particles is unsuitable, the shape of the internal pores of the sintered board may be unfavorable for the diffusion of supercritical fluid, leading to a decrease in the expansion ratio of the subsequently formed foamed material. The density, cell distribution, and size of the material are also affected. Besides binding the particles together, the hot-pressing sintering process also influences the pore shape between the particles and the subsequent foaming process. If the hot-pressing sintering temperature is too high, the pores between the particles will melt and merge; if the sintering temperature is too low, a strong bond cannot be formed between the particles, causing the supercritical fluid to easily escape through the pores between the particles during the subsequent foaming process. The cells cannot be fixed, severely affecting the expansion ratio and foaming quality.

[0013] The porosity of the sintered board obtained by hot pressing in step S1 also affects the performance of the foamed board. Too low a porosity will affect the diffusion of supercritical fluids; too high a porosity indicates insufficient packing density of polymer rod-shaped particles, and the size of the pores formed between particles is somewhat random. This not only leads to a decrease in both the size and uniformity of the foamed cells formed in subsequent foaming processes, but may even result in defects such as voids on the surface of the foamed board, seriously affecting its commercial application prospects.

[0014] To obtain foamed polymer sheets with both excellent foaming quality and expansion ratio, step S2 requires foaming the sintered sheet in a mold with a specific ratio. By controlling the length ratio of the sintered sheet to the mold, the sheet can completely fill the mold during the foaming process. Utilizing the confinement effect of the mold and the foaming effect of the supercritical fluid inside the sheet, dense pores can be formed inside the sheet, thereby producing high-quality foamed polymer sheets. In a specific embodiment of the present invention, the length of the sintered sheet in any of the three-dimensional directions (including the x-axis, y-axis, and z-axis) is the length (x-axis length), width (y-axis length), and thickness (z-axis length) of the sintered sheet. In the present invention, if the ratio of the length of the sintered sheet in any dimension of the three-dimensional direction to the length of the mold in the corresponding dimension is <0.1:1, it indicates that the length (or width, thickness) of the mold is too high, which easily leads to free expansion of the sintered sheet in that direction. This not only causes the internal pores of the sheet to expand and rupture, resulting in the inability to guarantee the uniformity of the pore distribution and size of the foamed sheet, affecting the surface quality of the sheet in that direction, but also easily leads to the formation of interconnected pores between the ruptured pores, resulting in a decrease in the thermal insulation performance of the sheet.

[0015] It should be noted that in step S1, the porosity of the sintered plate can be adjusted by regulating the filling amount of polymer rod-shaped particles in the hot-pressing sintering mold or furnace, as well as parameters such as the hot-pressing sintering temperature, pressure, and time. The porosity of the sintered plate is calculated by the following formula:

[0016] P= ;

[0017] Where P is porosity, m1 is the mass of a fully compacted sintered plate under natural volume (by increasing the particle filling amount and adjusting the pressure and temperature of hot pressing sintering, a fully compacted sintered plate with 0 porosity can be obtained, at which point its mass and natural volume can be obtained; the natural volume is calculated by measuring the length, width and height of the sintered plate with a measuring tool), and m2 is the actual mass of the sintered plate under the same natural volume.

[0018] In a specific embodiment of the present invention, the filling amount of polymer rod-shaped microparticles in the hot-pressing sintering mold or hot-pressing sintering furnace in step S1 is 60~95wt% (before hot-pressing sintering, the filling amount of particles in the mold or sintering furnace, plus the initial porosity of the plate at this time, is 100%; during the sintering process, as the pressure, time and temperature of hot-pressing sintering increase, the porosity of the plate will decrease accordingly, and the porosity of the final sintered plate is 3-25%). However, in addition to affecting the porosity of the plate, as mentioned above, the sintering temperature also affects the degree of adhesion between microparticles and the shape of pores inside the plate. Therefore, in step S1, adjusting the sintering temperature is necessary to ensure that the porosity of the sintered plate is 3-25%, and further ensure that the degree of adhesion between microparticles and the shape of pores are appropriate.

[0019] In a specific embodiment of the present invention, the ratio of the dimension of the sintered plate in any dimension of the three-dimensional direction to the dimension of the mold in the corresponding dimension in step S2 is ≥0.1:1, which means: the ratio of the length of the sintered plate to the length of the mold is ≥0.1:1, the ratio of the width of the sintered plate to the width of the mold is ≥0.1:1, and the ratio of the thickness of the sintered plate to the thickness of the mold is ≥0.1:1.

[0020] Preferably, the polymer rod-shaped microparticles in step S1 comprise the following parts by weight of preparation raw materials:

[0021] 80-100 parts of polymer, 0.1-5 parts of nucleating agent, and 0.1-1.0 parts of antioxidant.

[0022] More preferably, the method for preparing the polymer rod-shaped microparticles in step S1 includes the following steps:

[0023] Mix the raw materials in the specified proportions, melt and extrude, and then pelletize to obtain polymer rod-shaped microparticles.

[0024] More preferably, the melt extrusion is performed using a twin-screw extruder.

[0025] More preferably, the polymer includes at least one of general-purpose plastics, engineering plastics, thermoplastic elastomers, and biodegradable polymers.

[0026] More preferably, the general-purpose plastic includes at least one of PP (polypropylene), PE (polyethylene), and PS (polystyrene).

[0027] More preferably, the engineering plastic includes at least one of PPE (polyphenylene oxide), PEI (polyetherimide), and PET (polyethylene terephthalate).

[0028] More preferably, the thermoplastic elastomer includes at least one of TPU (thermoplastic polyurethane), TPEE, and TPAE.

[0029] More preferably, the biodegradable polymer includes at least one of PBAT, PLA, and PHA.

[0030] More preferably, the nucleating agent includes at least one of talc, calcium carbonate, phosphate, and sorbitol derivatives.

[0031] More preferably, the antioxidant includes at least one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, tris(2,4-di-tert-butylphenyl) phosphite, and dioctaneamine.

[0032] Preferably, the polymer rod-shaped microparticles in step S1 have a diameter of 1.5 to 2.6 mm and an aspect ratio of 1 to 2.

[0033] Preferably, the porosity of the sintered plate in step S1 is 5-20%. Typical, but not limiting, porosities are 5%, 8%, 10%, 12%, 15%, and 20%.

[0034] Preferably, the pressure of hot pressing sintering in step S1 is 10~30MPa.

[0035] Preferably, the hot pressing sintering time in step S1 is 5 to 20 minutes.

[0036] In a specific embodiment of the present invention, the sintered plate obtained in step S1 has a length of 5 cm to 3 m, a width of 5 cm to 2 m, and a thickness of 2 mm to 50 mm. Preferably, the sintered plate obtained in step S1 has a length of 5 cm to 2 m, a width of [missing information], and a thickness of 5 mm to 40 mm.

[0037] Preferably, the impregnation in step S2 is carried out at a temperature of 100~300℃ and a supercritical fluid pressure of 8.0~25.0 MPa.

[0038] Preferably, the supercritical fluid in step S2 includes at least one of carbon dioxide and nitrogen.

[0039] More preferably, the supercritical fluid in step S2 includes carbon dioxide and nitrogen.

[0040] More preferably, the partial pressure of carbon dioxide in the supercritical fluid in step S2 is 5~8 MPa.

[0041] More preferably, the partial pressure of nitrogen in the supercritical fluid in step S2 is 11~13 MPa.

[0042] More preferably, the soaking time in step S2 is 0.2 to 1.5 h.

[0043] Preferably, after the pressure relief foaming in step S2, a heat preservation step is further included, and the heat preservation time is 0.5~5 minutes.

[0044] After foaming in a mold, the sintered board undergoes a suitable period of heat preservation (equivalent to restricted sintering), which can further improve the internal bonding ability of the foamed board. If the heat preservation time is too short, the bonding between particles in the foamed board may not reach the optimal state; if the heat preservation time is too long, the foamed board is prone to shrinkage due to prolonged exposure to high temperature.

[0045] More preferably, the heat preservation time is 1.5 to 3 minutes.

[0046] Preferably, the length of the sintered plate in any three-dimensional direction in step S2 is in the ratio of the length of the mold in the corresponding direction to (0.4~0.8):1.

[0047] If the ratio of the length of the sintered board in any three-dimensional direction to the length of the mold in the corresponding dimension is greater than 0.8:1, it indicates that the length (or width, thickness) of the mold is too low, which may cause the sintered board to not expand sufficiently in that direction, thus affecting the foaming ratio of the foamed board.

[0048] The present invention also protects a polymer foam board prepared by the above preparation method.

[0049] This invention also protects the application of the above-mentioned polymer foamed boards in thermal insulation materials, structural materials, and cushioning materials.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] The polymer foamed board provided by this invention has excellent foaming effect, with a foaming ratio of over 8.3 times and a density as low as 0.15 g / cm³. -3 The following materials exhibit excellent lightweight properties and uniform cell size and distribution, demonstrating promising commercial application prospects. Furthermore, their thermal conductivity is no higher than 0.09 W / m². -1 K -1 It has excellent thermal insulation properties. Attached Figure Description

[0052] Figure 1 This is an optical photograph of the polymer foamed board obtained in Example 1 of the present invention.

[0053] Figure 2 This is a cross-sectional scanning electron microscope image of the polymer foamed board obtained in Example 1 of the present invention. Detailed Implementation

[0054] The present invention will be further described below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise stated, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents. The raw material information used in each embodiment and comparative example is as follows:

[0055] PBAT: Jinhui Zhaolong, with a melt index of 4.69 g / 10 min measured at 190℃ and 2.16 kg, and a Vicat softening point T2 of 94.5℃ at a load of 10 N and a heating rate of 10℃ / min.

[0056] TPU: Huafeng 90A, with a melt index of 5 g / 10 min measured at 210℃ and 2.16 kg, a Vicat softening point T2 of 116℃ at a load of 10 N and a heating rate of 10℃ / min.

[0057] PP: ExxonMobil, with a melt index of 3 g / 10 min measured at 230 °C and 2.16 kg, and a Vicat softening point T2 of 125.5 °C at a load of 10 N and a heating rate of 10 °C / min.

[0058] PPE: Kingfa Science & Technology, with a melt index of 19 g / 10 min measured at 230℃ and 2.16 kg, a Vicat softening point T2 of 138℃ at a load of 10 N and a heating rate of 10℃ / min.

[0059] Nucleating agent: Talc, commercially available.

[0060] Antioxidant: Antioxidant 1010 (pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]), commercially available.

[0061] Examples 1-12 and Comparative Examples 1-9

[0062] This embodiment, compared to the comparative examples, provides a method for preparing polymer foamed boards with different parameters such as polymer rod particle size and hot-pressing sintering temperature. The method includes the following steps:

[0063] S1. Mix 98 parts of PBAT, 1.5 parts of nucleating agent, and 0.5 parts of antioxidant, and melt-extrude using a twin-screw extruder. After cooling and pelletizing, polymer rod-shaped microparticles are obtained. The polymer rod-shaped microparticles are injected into the die of a molding press for hot pressing and sintering (particle filling amount is 70-95%, of which the particle filling amount is 85% for the die of Example 1; the hot pressing pressure is 15 MPa and the time is 7 min), to obtain sintered die with a length, width, and thickness of 10 cm, 10 cm, and 20 mm, respectively.

[0064] S2. Place the sintered board obtained in step S1 into a mold, inject 18 MPa of supercritical fluid (with a carbon dioxide partial pressure of 7 MPa and a nitrogen partial pressure of 11 MPa) at 112°C for 40 min (0.67 h), then depressurize and foam, and keep warm for 3 min to obtain the polymer foam board.

[0065] The corresponding parameters in Examples 1-12 and Comparative Examples 1-9 are shown in Table 1 below:

[0066] Table 1. Corresponding parameters in Examples 1-12 and Comparative Examples 1-9

[0067]

[0068] Note: In Table 1 above, "the length ratio of the sintered plate to the mold in any three-dimensional direction" refers to the ratio of the length of the sintered plate in any three-dimensional direction (the lengths in the three directions are the length, width, and height of the plate) to the length of the mold in the corresponding direction.

[0069] Example 13

[0070] A method for preparing a polymer foamed board includes the following steps:

[0071] S1. Mix 96 parts of PBAT, 3.5 parts of nucleating agent, and 0.5 parts of antioxidant, and melt-extrude using a twin-screw extruder. After cooling and pelletizing, polymer rod-shaped microparticles with a diameter of 1.2 mm and an aspect ratio of 1.2 are obtained. The polymer rod-shaped microparticles are injected into the die of a molding press (82% filling) and hot-pressed for sintering (hot pressing temperature is 115℃, T1-T2=20.5℃; hot pressing pressure is 20MPa, and time is 10min) to obtain a sintered plate with a thickness of 12 mm and a porosity of 10%.

[0072] S2. Place the sintered board obtained in step S1 into a mold (the ratio of the size of the sintered board in any dimension of the three-dimensional direction to the size of the mold in the corresponding dimension is 0.5:1), inject 18 MPa of supercritical fluid (where the partial pressure of carbon dioxide is 7 MPa and the partial pressure of nitrogen is 11 MPa) at 112℃ for 25 min (0.42 h) for impregnation, then depressurize and foam, and keep warm for 1.5 min to obtain the polymer foamed board.

[0073] Example 14

[0074] A method for preparing a polymer foamed board includes the following steps:

[0075] S1. Mix 98 parts of PBAT, 1.5 parts of nucleating agent, and 0.5 parts of antioxidant, and melt-extrude using a twin-screw extruder. After cooling and pelletizing, polymer rod-shaped microparticles with a diameter of 2.5 mm and an aspect ratio of 1.5 are obtained. The polymer rod-shaped microparticles are injected into the die of a molding press (83% filling) for hot pressing and sintering (hot pressing temperature is 115℃, T1-T2=20.5℃; hot pressing pressure is 16MPa, and time is 8min) to obtain a sintered plate with a thickness of 20 mm and a porosity of 15%.

[0076] S2. Place the sintered board obtained in step S1 into a mold (the ratio of the size of the sintered board in any dimension of the three-dimensional direction to the size of the mold in the corresponding dimension is 0.4:1), inject 20 MPa of supercritical fluid (where the partial pressure of carbon dioxide is 8 MPa and the partial pressure of nitrogen is 12 MPa) at 114℃ for 35 min (0.58 h), then depressurize and foam, and keep warm for 3 min to obtain the polymer foamed board.

[0077] Example 15

[0078] A method for preparing a polymer foamed board includes the following steps:

[0079] S1. Mix 99 parts TPU, 0.5 parts nucleating agent, and 0.5 parts antioxidant, and melt-extrude using a twin-screw extruder. After cooling and pelletizing, polymer rod-shaped microparticles with a diameter of 1.5 mm and an aspect ratio of 1.3 are obtained. The polymer rod-shaped microparticles are injected into the die of a molding machine (85% filling) for hot pressing and sintering (hot pressing temperature is 130℃, T1-T2=14℃; hot pressing pressure is 20MPa, and time is 10min) to obtain a sintered board with a thickness of 15 mm and a porosity of 10%.

[0080] S2. Place the sintered board obtained in step S1 into a mold (the ratio of the size of the sintered board in any dimension of the three-dimensional direction to the size of the mold in the corresponding dimension is 0.6:1), inject 18 MPa of supercritical fluid (where the partial pressure of carbon dioxide is 5 MPa and the partial pressure of nitrogen is 13 MPa) at 120°C for 30 min (0.5 h) for impregnation, then depressurize and foam, and keep warm for 2 min to obtain the polymer foamed board.

[0081] Example 16

[0082] A method for preparing a polymer foamed board includes the following steps:

[0083] S1. Mix 96 parts of PP, 3 parts of nucleating agent, and 1 part of antioxidant, and melt-extrude using a twin-screw extruder. After cooling and pelletizing, polymer rod-shaped microparticles with a diameter of 1.2 mm and an aspect ratio of 1.3 are obtained. The polymer rod-shaped microparticles are injected into the die of a molding press (87% filling) for hot pressing and sintering (hot pressing temperature is 145℃, T1-T2=19.5℃; hot pressing pressure is 12MPa, and time is 8min) to obtain a sintered plate with a thickness of 18 mm and a porosity of 10%.

[0084] S2. Place the sintered board obtained in step S1 into a mold (the ratio of the size of the sintered board in any dimension of the three-dimensional direction to the size of the mold in the corresponding dimension is 0.4:1), inject 18 MPa of supercritical carbon dioxide at 140℃ for 25 min (0.42 h) for impregnation, then depressurize and foam, and keep warm for 1.5 min to obtain the polymer foamed board.

[0085] Example 17

[0086] A method for preparing a polymer foamed board includes the following steps:

[0087] S1. Mix 98 parts of PPE, 1 part of nucleating agent, and 1 part of antioxidant, and melt-extrude using a twin-screw extruder. After cooling and pelletizing, polymer rod-shaped microparticles with a diameter of 0.8 mm and an aspect ratio of 1 are obtained. The polymer rod-shaped microparticles are injected into the die of a molding press (89% filling) for hot pressing and sintering (hot pressing temperature is 170℃, T1-T2=32℃; hot pressing pressure is 25MPa, and time is 11min) to obtain a sintered board with a thickness of 10 mm and a porosity of 5%.

[0088] S2. Place the sintered board obtained in step S1 into a mold (the ratio of the size of the sintered board in any dimension of the three-dimensional direction to the size of the mold in the corresponding dimension is 0.7:1), inject 20 MPa of supercritical carbon dioxide at 160℃ for 25 min (0.42 h) for impregnation, then depressurize and foam, and keep warm for 1 min to obtain the polymer foamed board.

[0089] Example 18

[0090] A method for preparing polymer foamed boards, wherein the only difference from Example 16 is:

[0091] After depressurization and foaming, keep warm for 8 minutes.

[0092] Example 19

[0093] A method for preparing polymer foamed boards, wherein the only difference from Example 1 is:

[0094] In step S2, the ratio of the length of the sintered plate along the x-axis in the three-dimensional direction to the length of the mold along the x-axis is 0.1:1; the ratio of the length of the sintered plate along the y-axis in the three-dimensional direction to the length of the mold along the y-axis is 0.3:1; and the ratio of the length of the sintered plate along the z-axis in the three-dimensional direction to the length of the mold along the z-axis is 0.4:1.

[0095] Example 20

[0096] A method for preparing polymer foamed boards, wherein the only difference from Example 1 is:

[0097] In step S2, the ratio of the length of the sintered plate along the x-axis in the three-dimensional direction to the length of the mold along the x-axis is 0.6:1; the ratio of the length of the sintered plate along the y-axis in the three-dimensional direction to the length of the mold along the y-axis is 0.4:1; and the ratio of the length of the sintered plate along the z-axis in the three-dimensional direction to the length of the mold along the z-axis is 0.4:1.

[0098] Comparative Example 10

[0099] A method for preparing polymer foamed boards, wherein the only difference from Example 13 is:

[0100] Replace hot pressing sintering in step S1 with injection molding. The injection molding temperature is 120~150℃, the injection pressure is 10MPa, the holding time is 60s, and after 2min of cooling and mold opening, a dense sheet with 0 porosity is obtained.

[0101] Comparative Example 11

[0102] A method for preparing polymer foamed boards, wherein the only difference from Example 1 is:

[0103] In step S2, the ratio of the length of the sintered plate in the three-dimensional x-axis direction to the length of the mold in the x-axis direction is 0.05:1; the ratio of the length of the sintered plate in the three-dimensional y-axis direction to the length of the mold in the y-axis direction is 0.8:1; and the ratio of the length of the sintered plate in the three-dimensional z-axis direction to the length of the mold in the z-axis direction is 0.4:1.

[0104] Comparative Example 12

[0105] A method for preparing polymer foamed boards, wherein the only difference from Example 1 is:

[0106] In step S2, the ratio of the length of the sintered plate along the x-axis in the three-dimensional direction to the length of the mold along the x-axis is 0.4:1; the ratio of the length of the sintered plate along the y-axis in the three-dimensional direction to the length of the mold along the y-axis is 0.05:1; and the ratio of the length of the sintered plate along the z-axis in the three-dimensional direction to the length of the mold along the z-axis is 0.4:1.

[0107] Performance testing

[0108] Density test: Weigh each sample using an electronic balance and measure its volume. Calculate the density using the following formula: Density ρ (g / cm³) -3 = [sample mass (g)] / [sample volume (cm³)] 3 )].

[0109] Cell size and distribution test: The cross-section of the foamed sample was photographed by scanning electron microscope. The diameter of 100 cells was randomly selected at 200x magnification and statistically analyzed to obtain the average cell size of the foamed sample. The cell distribution was observed by SEM.

[0110] Foaming ratio test: Calculated using the formula ψ=ρ1 / ρ2, where ρ1 is the density of the sintered board and ρ2 is the density of the foamed board.

[0111] Thermal conductivity test: obtained according to standard ISO 8302.

[0112] The performance test data is shown in Table 2 below:

[0113] Table 2. Performance test data of polymer foamed boards obtained in the examples and comparative examples

[0114]

[0115]

[0116]

[0117] Note: In Table 2 above, "-" indicates that the test cannot be performed.

[0118] As can be seen from the data in Table 2 above, the polymer foamed board provided by this invention has excellent foaming effect, with a foaming ratio of over 8.3 times and a density as low as 0.15 g / cm³. -3 The following materials exhibit excellent lightweight properties and uniform cell size and distribution, demonstrating promising commercial application prospects. Furthermore, their thermal conductivity is no higher than 0.09 W / m². -1 K -1 It has excellent thermal insulation properties.

[0119] As can be seen from the data in Examples 1-6, when the diameter of the polymer rod-shaped particles in step S1 is preferably 1.5-2.6 mm and the aspect ratio is preferably 1-2 (Examples 1-3), the pore morphology formed by the accumulation of polymer particles is more suitable for the diffusion of supercritical fluid, thus the resulting foamed board has better overall performance. In Examples 4-5, adjusting the particle diameter with a fixed aspect ratio is essentially proportionally enlarging or shrinking the particles. Under the same porosity conditions, smaller particles result in smaller pore sizes (Example 4), which to some extent is beneficial for forming more uniform and abundant pores. However, excessively small particles can negatively impact the impregnation and diffusion of supercritical fluid, thus affecting the foaming effect and causing a decrease in foaming ratio and thermal insulation performance. With a fixed porosity, larger particles (Example 5) result in larger pore sizes, which is more favorable for the impregnation of supercritical fluid, leading to larger pore sizes. However, the presence of large pores, similar to interconnected pores, facilitates air circulation, thus causing a significant decrease in thermal insulation performance.

[0120] As can be seen from the data in Examples 1 and 8-10, the porosity of the sintered plate can be adjusted by changing the amount of polymer particles in the sintering furnace under the same hot pressing conditions. When the porosity is 5-20% (Examples 1 and 8), which is preferred in this invention, the overall performance is better.

[0121] According to Examples 1, 11-12, and Comparative Example 5, the size ratio of the sintered board to the foaming mold has a certain impact on the foaming result. If this size ratio is too small (Comparative Example 5), it means that the size of the foaming mold is too large relative to the size of the sintered board, which easily leads to free expansion, resulting in a decrease in the foaming quality of the sintered board and insufficient bonding between the foamed particles, affecting other properties. When the size ratio of the sintered board to the foaming mold is too large (Example 12), it means that the sintered board is difficult to fully foam in the mold, thus having a certain negative impact on the foaming ratio.

[0122] According to Comparative Examples 1-2, if the hot pressing sintering temperature does not meet the condition T1-T2=10~50℃, the sintering degree of the resulting sintered board will be unsuitable. The negative impact of sintering temperature on porosity can be avoided by adjusting the filling amount of particles. However, an inappropriate sintering temperature will still affect the diffusion of supercritical fluid in the subsequent foaming process, resulting in poor foaming capacity and foaming effect.

[0123] According to Comparative Examples 3-4, unsuitable porosity of sintered plates affects the diffusion of supercritical fluids, further impacting foaming efficiency and effectiveness.

[0124] According to Comparative Examples 6-9, the shape and particle size of the raw material particles affect the shape of the pores in the sintered board, which in turn affects the diffusion of supercritical fluids, further affecting the foaming efficiency and effect.

[0125] According to Comparative Examples 11-12, the inappropriate ratio between the length of the sintered plate in a single direction and the mold affects the surface quality of the sintered plate, which in turn has a certain negative impact on its forming effect.

[0126] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a polymer foamed board, characterized in that, Includes the following steps: S1. Hot-pressing and sintering polymer rod-shaped microparticles to obtain a sintered plate; the diameter of the polymer rod-shaped microparticles is 0.3~2.8 mm, and the aspect ratio is 1~3; the hot-pressing and sintering temperature is T1 and satisfies T1-T2=10~50℃, where T2 is the Vicat softening temperature of the polymer rod-shaped microparticles; the hot-pressing and sintering pressure is 10~30MPa, and the time is 5~20min; the porosity of the sintered plate is 3~25%; S2. Place the sintered board obtained in step S1 into a mold, inject supercritical fluid for impregnation, and then depressurize and foam to obtain a polymer foamed board; the length of the sintered board in any three-dimensional direction is ≥0.1:1 to the length of the mold in the corresponding direction; the impregnation is carried out at a temperature of 100~300℃ and a supercritical fluid pressure of 8.0~20.0 MPa for 0.2~1.5 h; after depressurization and foaming, a heat preservation step is also included, and the heat preservation time is 0.5~5 min.

2. The method for preparing polymer foamed board as described in claim 1, characterized in that, The polymer rod-shaped microparticles in step S1 comprise the following parts by weight of preparation raw materials: 80-100 parts of polymer, 0.1-5 parts of nucleating agent, and 0.1-1.0 parts of antioxidant.

3. The method for preparing polymer foamed board as described in claim 2, characterized in that, The method for preparing the polymer rod-shaped microparticles in step S1 includes the following steps: Mix the raw materials in the specified proportions, melt and extrude, and then pelletize to obtain polymer rod-shaped microparticles.

4. The method for preparing polymer foamed board as described in claim 3, characterized in that, Includes at least one of the following (a) to (c): (a) The polymer includes at least one of PP, PE, PS, PPE, PEI, PET, TPU, TPEE, TPAE, PBAT, PLA, and PHA; (b) The nucleating agent includes at least one of talc, calcium carbonate, phosphate, and sorbitol derivatives; (c) The antioxidant comprises at least one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, tris(2,4-di-tert-butylphenyl) phosphite, and dioctaneamine.

5. The method for preparing polymer foamed board as described in claim 1, characterized in that, Includes at least one of the following (d) to (e): (d) The diameter of the polymer rod-shaped microparticles in step S1 is 1.5~2.6 mm and the aspect ratio is 1~2; (e) The porosity of the sintered plate in step S1 is 5 to 20%.

6. The method for preparing polymer foamed board as described in claim 1, characterized in that, The supercritical fluid in step S2 includes at least one of carbon dioxide and nitrogen.

7. The method for preparing polymer foamed board as described in claim 1, characterized in that, The ratio of the length of the sintered plate to the length of the mold in step S2 is (0.4~0.8):

1.

8. Polymer foamed board prepared by any one of claims 1 to 7.

9. The application of the polymer foam board according to claim 8 in thermal insulation materials, structural materials, and cushioning materials.

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