Profiling foam for battery liquid cooling plate, preparation method and battery liquid cooling plate

Abstract

The invention discloses profiling foam for a battery liquid cooling plate, the foam is a polyolefin resin foaming sheet containing polypropylene resin, the DSC melting peak temperature Tm of the polyolefin resin foaming sheet is 140-160 DEG C, the crosslinking degree G is 20-60%, the polyolefin resin foaming sheet is heated for 2-5 minutes in an oven with the oven temperature t being T + / -5 DEG C, T = Tm + (G / 4) DEG C, and the profiling foam has specific dimensional change rates in the MD, TD and ZD directions. The profiling foam for the battery liquid cooling plate is stable in size under the influence of environmental factors such as temperature and humidity, can adapt to a zigzag complex structure of the liquid cooling plate and is tightly attached, meanwhile, excellent impact absorbability and supporting stability are kept, and the problem of condensation of condensate water can be further effectively solved.

Description

Technical Field

[0001] This invention relates to the field of power battery components, and particularly to conformal foam for battery liquid cooling plates, its preparation method, and battery liquid cooling plates using the foam. Background Technology

[0002] With the rapid development of the new energy vehicle industry, the performance and safety of power batteries, as core components of new energy vehicles, have attracted much attention. Power batteries generate a large amount of heat during charging and discharging. If this heat cannot be dissipated effectively and in a timely manner, it will lead to excessively high battery temperatures, resulting in decreased battery performance, shortened lifespan, and even safety hazards. As a key component of the power battery thermal management system, the liquid cooling plate plays a decisive role in the battery's performance and lifespan due to its heat dissipation performance and structural stability.

[0003] Currently, traditional support foam is widely used between battery liquid cooling plates and battery modules, serving a supporting and cushioning function. However, during long-term use, traditional support foam has revealed several problems. First, traditional support foam is prone to compression deformation, which can lead to problems under prolonged electrical loads. After the pressure on the battery module and the liquid cooling plate, their thickness gradually decreases, making it unable to provide stable support. This leads to a decrease in the fit between the liquid cooling plate and the battery module, affecting the heat dissipation effect.

[0004] Secondly, as traditional support foam is used for a longer period of time and is affected by environmental factors such as temperature and humidity, the foam will change in size and crack. This not only makes it lose its support and protection for the liquid cooling plate, but may also allow foreign objects to enter the battery system, causing more serious safety problems.

[0005] Furthermore, considering the complex structure of the liquid cooling plate and the difficulty in processing the foam, ensuring that the foam can adapt to the complex structure and has good adhesion is a major challenge.

[0006] Furthermore, in practical applications, the environment in which the battery liquid cooling plate operates is complex and variable. It must withstand the impacts and vibrations during vehicle operation, as well as cope with different temperature and humidity conditions. In some low-temperature and high-humidity environments, condensation is prone to occur at the application sites of the battery liquid cooling plate, which can further corrode the liquid cooling plate and battery module, reducing the reliability of the battery system. Existing support foam cannot effectively solve this problem.

[0007] At the same time, the foam must maintain its key function, namely, to have excellent impact absorption and support stability, so as to ensure that the liquid cooling plate can work normally under various working conditions.

[0008] In summary, developing a conformal foam for battery liquid cooling plates that is resistant to compression deformation, dimensionally stable under the influence of environmental factors such as temperature and humidity, can adapt to and tightly adhere to the complex and tortuous structure of liquid cooling plates, maintains excellent impact absorption and support stability, and can further effectively solve the problem of condensation is of great practical significance and has an urgent market demand. Summary of the Invention

[0009] To address the shortcomings of existing technologies, the present invention aims to provide a battery liquid cooling plate conformal foam that is resistant to compression deformation, dimensionally stable under the influence of environmental factors such as temperature and humidity, can adapt to and tightly adhere to the complex and tortuous structure of the liquid cooling plate, while maintaining excellent impact absorption and support stability, and further solves the problem of condensation.

[0010] In order to solve the above problems, the inventors conducted in-depth research and found that foam with a certain range of dimensional changes in each direction at a specific temperature can solve the above problems. Furthermore, foam with a specific range of thermal conductivity can further solve the problem of condensation at the application site.

[0011] The specific plan is as follows: In a first aspect, this invention discloses a conformal foam for a battery liquid cooling plate, wherein the foam is a polyolefin resin foam sheet containing polypropylene resin, and the DSC melting peak temperature T of the polyolefin resin foam sheet is... m The temperature is 140-160℃, the degree of crosslinking G is 20%-60%, and the polyolefin resin foam sheet is heated in an oven at a temperature t of T±5℃ for 2-5 minutes. The dimensional change rate of the polyolefin resin foam sheet in the MD direction is 0 to -5%, in the TD direction is -3% to +5%, and in the ZD direction is 0 to +5%, where "-" indicates shrinkage and "+" indicates expansion. The test temperature T is related to the DSC melting peak temperature T of the foam. m The following relationship exists between T and the degree of crosslinking G of the foam: T = T m +(G / 4)℃, when the polyolefin resin foam sheet has multiple DSC melting peaks, the DSC melting peak temperature T of the polyolefin resin foam sheet is... m This refers to the highest DSC melting peak temperature.

[0012] In one embodiment, the thermal conductivity of the foam is less than 0.05 W / m·K, preferably less than 0.045 W / m. K.

[0013] In one embodiment, the thickness h of the foam is 2-20 mm, preferably 3-15 mm, and more preferably 4-10 mm; the foam density ρ is 0.08-0.3 g / cm³. 3Preferably, it is 0.1-0.25 g / cm³. 3 Further preferably, it is 0.12-0.22 g / cm³. 3 .

[0014] In one embodiment, the foam is a single polyolefin resin foam sheet, or a composite of two or more individual polyolefin resin foam sheets.

[0015] In one embodiment, the impact absorption rate of the foam is 60-90%.

[0016] Secondly, this invention discloses a method for preparing a conformal foam for a battery liquid cooling plate, comprising the following steps: (1) Mixing of matrix resins: Polypropylene resin and polyethylene resin are mixed by mass fraction, wherein the polypropylene resin accounts for more than 40% and less than 100%, and the polyethylene resin accounts for more than 0% and less than 60%. The highest DSC melting point temperature T of the polypropylene resin m The melt flow rate is 0.1-5.0 g / 10 min at 140℃-160℃ and 230℃ / 2.16 kg load. The polyethylene resin has a density of 0.91-0.96 g / cm³ and a melt flow rate of 0.5-5.0 g / 10 min under conditions of 190℃ / 2.16 kg load. (2) Mixing of additives: Add an additive comprising at least a foaming agent to the resin matrix of step (1); the foaming agent is a decomposable foaming agent selected from at least one of azodicarbonamide, sodium bicarbonate, azobisisobutyronitrile, benzenesulfonyl hydrazine, and dinitrospentamethylenetetramine; the amount of additive added is 0.5%-5% of the mass of the resin matrix; (3) Preparation of pre-foamed body: The mixture from step (2) is melt-mixed through an extruder at an extrusion temperature of 160℃-180℃, and then cooled after being shaped by a mold to obtain a pre-foamed sheet containing a foaming agent. (4) Cross-linked foam process: The pre-foamed sheet is subjected to radiation crosslinking treatment, and the radiation source is selected from at least one of electron rays, alpha rays, beta rays, gamma rays, and X-rays; The cross-linked pre-foamed sheet is stretched in the MD direction and foamed at 220℃-310℃, with the foaming temperature controlled at the decomposition temperature of the decomposition foaming agent. (5) Cooling and molding: The foamed sheet obtained in step (4) is naturally cooled and shaped to obtain the conformal foam for the battery liquid cooling plate.

[0017] In one of the schemes, the mass fraction of polypropylene resin in step (1) is preferably 60%-90%, and the density of polyethylene resin is further preferably 0.92-0.95 g / cm³.

[0018] In one embodiment, the decomposable foaming agent is azodicarbonamide, and its addition amount accounts for 0.8%-3% of the resin matrix mass.

[0019] In one embodiment, the additives in step (2) further include flame retardants and / or antioxidants, wherein the flame retardant is selected from at least one of aluminum hydroxide, magnesium hydroxide, and decabromodiphenyl ethane; and the antioxidant is selected from hindered phenolic or phosphite antioxidants.

[0020] In one embodiment, a crosslinking aid is added during the radiation crosslinking of the pre-foamed sheet in step (4). The crosslinking aid is selected from one or more of dicumyl peroxide (DCP), divinylbenzene, cellulose triacetate (TAC), triallyl isocyanurate (TAIC), trimethylolpropane trimethacrylate (TMPTMA), and vinyl ethylbenzene.

[0021] In one of the schemes, when the pre-foamed sheet after crosslinking in step (4) is foamed, the ratio of the traction rate in the MD direction to the traction rate before foaming is 1.1-1.9.

[0022] In one of the schemes, the foaming temperature in step (4) is further preferably 230℃-260℃.

[0023] Thirdly, the present invention provides a battery liquid cooling plate, wherein the battery liquid cooling plate includes a buffer pad structure that matches the flow channel structure of the battery liquid cooling plate, and the buffer pad structure is prepared by the following specific steps: (a) High-temperature preheating: The battery liquid cooling plate of the present invention is cut with conformal foam and placed in an oven. The oven temperature t is set to a range of T ± 5℃, where T = T m Heat at +(G / 4)℃ for 2-5 minutes. (b) Cooling and shaping: The preheated foam is transferred to a mold with a liquid cooling plate flow channel structure, and molding pressure is applied by a press and the foam is cooled and shaped to obtain a buffer pad structure that matches the liquid cooling plate.

[0024] In one embodiment, the flow channel structure of the mold complements the uneven surface features of the battery liquid cooling plate, the molding pressure is 0.5-5MPa, and the cooling temperature is 10-40℃.

[0025] The beneficial effects of this invention are: The present invention first forms a foam that has a certain range of dimensional changes in each direction at a specific temperature. The foam with this characteristic can be attached to the battery liquid cooling plate through a specific process. The compressive deformation resistance of the foam provides support and protection for the liquid cooling plate, and maintains dimensional stability in the environment of repeated high and low temperature changes and a certain humidity of the liquid cooling plate.

[0026] Meanwhile, in the production process of battery liquid cooling plate buffer pads, the dimensional change characteristics of foam at a specific temperature are utilized. Through hot pressing and cooling process, it can be precisely attached to the mold with liquid cooling plate flow channel structure, meeting the installation requirements of complex structures. It can adapt to the tortuous and complex structure of liquid cooling plate and adhere tightly, thus forming a buffer pad structure that is highly matched with the shape of liquid cooling plate.

[0027] Secondly, during driving on roads with poor conditions, vehicles generate low-frequency and high-frequency vibrations. The porous structure and suitable cross-linking degree of the polypropylene resin foam in the foam of this invention endow the foam with excellent elasticity and damping properties. When subjected to vibration and impact, the internal pore structure of the foam can undergo elastic deformation, converting vibration energy into heat energy and other forms of energy for dissipation. This effectively reduces the vibration energy transmitted to the liquid cooling plate, protecting the liquid cooling plate and ensuring its normal operation under complex vibration environments, avoiding problems such as component damage or loose connections caused by vibration.

[0028] Furthermore, by controlling the thermal conductivity of the foam within a specific range, the problem of condensation easily forming on the foam due to the working nature of the liquid cooling plate is further solved. The ideal operating range for a power battery is 20-40 degrees Celsius. However, due to continuous charging and discharging during operation, a liquid cooling plate is needed to control the temperature range and ensure the battery operates within the ideal temperature range. When the battery liquid cooling plate is in operation, its surface temperature is low, creating a significant temperature difference with the surrounding environment, which easily leads to condensation at the foam. The foam of this invention has a low thermal conductivity, effectively preventing heat transfer from the surrounding environment to the surface of the liquid cooling plate, reducing the temperature difference between the foam and the surrounding environment, thereby reducing the possibility of condensation. Even in environments with high humidity, it can effectively suppress condensation formation, avoiding corrosion of the liquid cooling plate and battery module by condensation, and improving the reliability and service life of the battery system. Detailed Implementation

[0029] Although the invention has been described to a certain extent, it is apparent that appropriate variations can be made to the various conditions without departing from the spirit and scope of the invention. It is understood that the invention is not limited to the described embodiments, but falls within the scope of the claims, which include equivalent substitutions for each of the elements.

[0030] This invention discloses a conformal foam for battery liquid cooling plates, wherein the foam is a polyolefin resin foam sheet containing polypropylene resin, and its DSC melting peak temperature T m The temperature ranges from 140 to 160℃, where the DSC melting peak temperature T is... m The type and content of comonomers, crystallinity, and the type and content of nucleating agents and plasticizers added in polypropylene resin foam sheets are all related to these factors. Those skilled in the art can, by combining these influencing factors, make predictive adjustments to the polypropylene resin to achieve its DSC melting peak temperature T. m It is 140-160℃. If the melting peak temperature T... m Below 140℃, the molded buffer pad parts formed by post-heat pressing are prone to cell collapse and deformation during use due to continuous compression, resulting in unstable thickness; while when the melting peak temperature T is below 140℃, the foam cells are prone to collapse and deformation, resulting in unstable thickness. m Above 160℃, the material exhibits high crystallinity, poor low-temperature brittleness, and is prone to cracking, resulting in poor low-temperature impact absorption. (DSC melting peak temperature T) m Further preferably, the temperature is 145-155℃, and more preferably 148-152℃. It should be noted that when the polyolefin resin foam sheet has multiple DSC melting peaks, such as a bimodal melting peak, the DSC melting peak temperature T of the polyolefin resin foam sheet... m This refers to the highest DSC melting peak temperature.

[0031] To enhance the mechanical properties of the material, especially for better dispersion and absorption of energy under impact, the degree of crosslinking of polypropylene resin foam sheets is limited to 20-60%, preferably 25-50%. Influencing factors include the type and content of crosslinking aids, the type and dose of crosslinking irradiation, and the temperature and duration of the crosslinking reaction. Those skilled in the art can, by considering these influencing factors, predictively adjust the degree of crosslinking of polypropylene resin foam sheets to ensure it falls within the specified range.

[0032] Heating in an oven at a temperature t of T ± 5℃ for 2-5 minutes resulted in shrinkage of 0 to -5% in the MD direction, dimensional change of -3% to +5% in the TD direction, and dimensional change of 0 to +5% in the ZD direction. Here, "-" indicates shrinkage and "+" indicates expansion. The test temperature T is related to the DSC melting peak temperature T of the polyolefin resin foam sheet. m The degree of crosslinking G between polyolefin resin foam sheets and the following relationship exists: T = T m +(G / 4)℃. In this invention, defining the test temperature T is a crucial inventive point. From the perspective of material forming process, T = T0 mThe +(G / 4)℃ setting correlates the test temperature with the processing temperature when polyolefin resin foam is hot-pressed into liquid-cooled plate parts. In actual production, the polyolefin resin foam first undergoes a high-temperature softening preheating stage, and this oven preheating temperature is the test temperature T or a temperature close to T (±5℃). The temperature close to T is mainly for oven temperature control. This means that when the processing temperature is less than T-5℃, the polyolefin resin foam cannot fully absorb heat, resulting in insufficient softening. In the subsequent hot-pressing process, the polyolefin resin foam is difficult to deform precisely according to the mold shape, making it impossible to form a liquid-cooled plate part that meets the requirements; even if it is barely formed, the dimensional tolerance of the formed part will be greater than the target value because the internal structure of the foam has not been fully adjusted. When such a part is applied to the liquid-cooled plate of a power battery, it cannot fit tightly into the complex structure of the liquid-cooled plate, resulting in poor buffering and support effects, and thus failing to effectively improve the impact absorption and structural stability of the power battery liquid-cooled plate. At the same time, a loose fit will result in uneven heat transfer and increased local temperature differences, making it difficult to solve the problem of condensation at the application site.

[0033] Conversely, when the processing temperature exceeds T+5℃, the polyolefin resin foam absorbs excessive heat during the preheating stage, significantly increasing the mobility of the molecular chains and leading to excessive shrinkage. Excessive shrinkage results in a large deviation between the dimensions of the polyolefin resin foam after molding and the expected conformal structure, making it impossible to obtain a dimensionally stable conformal structure. Such conformal foam cannot meet the assembly requirements of the battery liquid cooling plate, not only affecting its protective function but also potentially causing malfunctions in the installation and operation of other components within the battery system due to dimensional issues. Therefore, the oven temperature t is set within the range of T±5℃, where T=T m Only when the temperature reaches +(G / 4)℃ can the foam reach the appropriate softening level during the preheating stage. During the hot pressing process, it can be precisely shaped to match the liquid cooling plate and ensure the dimensional stability of the molded parts. This effectively improves the impact absorption and structural stability of the power battery liquid cooling plate, and successfully solves the problem of condensation in the application area, meeting the stringent requirements of the battery liquid cooling plate in practical applications.

[0034] The setting of dimensional changes in the MD, TD, and ZD directions of the foam at this preheating temperature is based on the following considerations: Liquid cooling plates typically have complex shapes and structures, requiring foam to fit snugly against them. Shrinkage of 0 to -5% in the MD direction allows the foam a certain amount of shrinkage allowance in this direction, enabling it to better adapt to the specific shape and contour of the liquid cooling plate. For example, in curved or cornered areas, appropriate shrinkage allows the foam to wrap more tightly around the liquid cooling plate. Dimensional variation of -3% to +5% in the TD direction allows for some shrinkage to accommodate localized recesses or other structural features of the liquid cooling plate, as well as some expansion to fill small gaps or protrusions, ensuring comprehensive and tight contact between the foam and the liquid cooling plate surface. Dimensional variation of 0 to +5% in the ZD direction allows for some expansion space in the thickness direction, helping to better fill gaps between the liquid cooling plate and other components during installation, providing good cushioning and sealing. At the same time, strictly limiting the dimensional variation range in each direction ensures that the foam maintains stable dimensions after preheating and molding. Furthermore, the shrinkage in the MD direction is preferably -1% to -4% independently, the dimensional change in the TD direction is preferably -2% to +4%, more preferably -1% to +3%, and the dimensional change in the ZD direction is preferably +1% to +4%, more preferably +2% to +3%. These characteristics of the foam are also closely related to the melt index, crosslinking degree, crystallinity, molecular chain orientation, and porosity of the resin matrix in the foam, which are of interest in this invention.

[0035] In one preferred embodiment, the thermal conductivity of the foam is limited to less than 0.05 (W / m²). K), preferably less than 0.04 W / m K), further preferably less than 0.03 (W / m The low thermal conductivity (K) effectively hinders heat transfer from the surrounding environment to the surface of the liquid cooling plate. By reducing the heat transfer rate, the temperature difference between the two sides of the foam is controlled within a small range, thereby reducing the condensation of water vapor due to temperature differences. In high-humidity environments, if the foam has a high thermal conductivity, rapid heat transfer will significantly lower the surface temperature of the liquid cooling plate, leading to the generation of a large amount of condensate, which can corrode the liquid cooling plate and battery module, affecting the reliability and lifespan of the battery system. The foam of this invention, with its low thermal conductivity, effectively avoids the above problems, ensuring the stable operation of the battery system. Furthermore, this low thermal conductivity, combined with the foam's dimensional stability and resistance to compression deformation at specific temperatures, ensures that heat transfer issues do not adversely affect other properties during the hot pressing and subsequent use of the foam, thus ensuring that the foam's protective function for the liquid cooling plate is effectively performed. The thermal conductivity of foam depends on the composition of the polypropylene resin in the foam. The cell structure of the foam includes the average cell size, cell distribution and cell shape, as well as the addition of fillers. At the same time, the molding process and foaming process affect the molecular chain orientation and crystallization, which also affect the thermal conductivity. Those skilled in the art can combine these influencing factors to predictively adjust the thermal conductivity of the foam to keep it within a certain range.

[0036] In one preferred embodiment, the thickness h of the foam is 2-20 mm, preferably 3-15 mm, and more preferably 4-10 mm, while the foam density ρ is 0.03-0.3 g / cm³. 3 The preferred concentration is 0.05-0.3 g / cm³. 3 More preferably, it is 0.08-0.3 g / cm³. 3 Generally, increasing the thickness of foam improves its impact resistance. However, when the thickness exceeds 20mm, insufficient installation space becomes a problem in the limited space layout of automotive battery modules, affecting the assembly and normal operation of the foam and other components. Conversely, if the thickness is less than 2mm, the impact absorption capacity of the foam will not meet actual needs, making it difficult to provide effective cushioning protection for the liquid cooling plate during vehicle operation to resist vibration and impact. In terms of density, theoretically, the lower the foam density, the better its impact resistance. However, when the density is below 0.03g / cm³, the foam becomes soft and cannot withstand the long-term pressure of the liquid cooling plate, easily deforming and reducing its support and cushioning performance. When the density is above 0.3g / cm³, the foam mass increases, which not only increases vehicle energy consumption, failing to meet the development requirements of lightweight vehicles and energy conservation and emission reduction, but may also have a certain impact on vehicle handling performance and range. Furthermore, the thickness and density range of the foam are related to its DSC melting peak temperature T. mThe degree of crosslinking is also relevant. During the foam molding process, appropriate thickness and density help the foam better adapt to the mold shape, ensuring the uniformity and stability of the crosslinking process. This allows the foam to maintain stable dimensions and structure while possessing good impact absorption performance, meeting the performance requirements of battery liquid cooling plates. The foam is a single polyolefin resin foam sheet, or a composite of two or more individual polyolefin resin foam sheets. Typically, when the foam thickness is 10mm or more, multiple polyolefin resin foam sheets are used in a composite process.

[0037] <Matrix Resin> The polypropylene resin used in this invention may comprise homopolymer polypropylene, ethylene-propylene block copolymer, or ethylene-propylene block copolymer, or a mixture of one or two of them. The temperature T of the highest melting peak of the polypropylene resin according to DSC is... m The temperature range is between 140°C and 160°C, and the melt flow rate (MI) is between 0.5 g / 10 min and 5.0 g / 10 min at 230°C / 2.16 kg load. The mass fraction of polypropylene resin is between 40% and 100%. When the proportion of polypropylene resin is less than 40%, the proportion of other components combined with the polyolefin mixed resin in this invention will be greater than 40%. The polyolefin resin sheet obtained by the process route of this invention will have insufficient temperature resistance. Under the condition that the oven temperature t is set at T±5°C, the high-temperature dimensional shrinkage of the polyolefin resin foam sheet will be greater than 5%, and a dimensionally stable conformal structure cannot be obtained. At the same time, when the polypropylene resin content is less than 40%, the obtained polyolefin foam resin sheet will have reduced impact absorption characteristics due to insufficient rigidity, which cannot meet the application scenarios required by this invention. The polypropylene resin is preferably between 45% and 100%, and more preferably between 50% and 100%.

[0038] In this invention, the polypropylene contains a structure of "hard segments" and "soft segments", wherein the different proportions of hard segments / soft segments determine that the acrylic resin has different physical properties, such as impact resistance, flexibility and processing performance.

[0039] "Hard segments": mainly composed of propylene units, which are regularly arranged and easily form crystalline structures. Hard segments endow materials with high rigidity and strength, as well as good heat resistance and chemical stability.

[0040] "Soft segments": Soft segments are typically composed of units from comonomers (such as ethylene, butene, hexene, or octene), which do not readily form regular crystalline structures. The presence of soft segments reduces the overall crystallinity of the material, increasing its flexibility and impact resistance.

[0041] Further, the polypropylene resin of this invention preferably contains more than 70 wt% propylene as a hard segment, and at least one α-olefin other than propylene as a soft segment, preferably a propylene-α-olefin random copolymer. The hard segment accounts for 70-100 wt%, preferably 85-99 wt%, more preferably 95%-98 wt%, with the balance being soft segments. The addition of soft segments reduces the crystallinity of the polypropylene resin, improving its transparency and toughness. The crystallinity of the polypropylene resin in this invention is between 30% and 60%, more preferably 32%-50%.

[0042] The polyethylene resin used in this invention may include low-density polyethylene resin, high-density polyethylene resin, linear low-density polyethylene resin, etc. One or more of these polyethylene resins may be selected, or two or more may be mixed and used. The density of the polyethylene resin is preferably 0.91 g / cm³. 3 Above and 0.96 g / cm 3 Below, a density of 0.92 g / cm³ is further preferred. 3 The above and density 0.95 g / cm³ 3 The following polyethylene resins are used, and the melt flow rate is 0.5-5.0 g / 10 min at 190°C / 2.16 kg load, more preferably 0.5-3.0 g / 10 min at 190°C / 2.16 kg load.

[0043] The proportion of polyethylene resin in polyolefin resin foam sheets is more than 0 wt% and less than 60 wt%, preferably more than 10 wt% and less than 50 wt%, and more preferably more than 15 wt% and less than 45 wt%. The addition of polyethylene resin can provide cross-linking fulcrums, increase the gel content of polyolefin resin foam sheets, and thus increase dimensional stability at high temperatures. This is a process requirement for polyolefin resin foam sheets to be more composite and conformal. However, when the content of polyethylene resin is greater than 60%, the temperature resistance of the entire polyolefin resin foam sheet will be insufficient. When conformal preheating processing is carried out under the condition of T±5℃, the shrinkage caused by insufficient temperature resistance will be too large, so the conformal parts obtained by this patent cannot obtain dimensionally stable products, thus failing to solve the core problem of this patent.

[0044] When polyethylene-based resins and polypropylene resins are mixed to form the matrix resin, a bimodal polyethylene-based resin is preferred. This resin undergoes polymerization via a metallocene catalyst and a Ziegler-Natta catalyst system, generating molecular chain segments with two different molecular weight distributions. The long molecular chain structure is similar to the long-branched characteristics of traditional low-density polyethylene (LDPE), endowing the material with excellent flexibility and impact resistance. The short molecular chain structure is similar to typical linear low-density polyethylene (LLDPE), which can improve the material's crystallinity and rigidity. This bimodal structure not only provides abundant free radical contact sites for electron irradiation crosslinking, effectively increasing the gel content of the resin after irradiation, but also significantly improves its temperature resistance and dimensional stability while enhancing the material's toughness and impact resistance. This structural complementarity allows the bimodal polyethylene-based resin to absorb energy through molecular chain slippage and deformation, making the matrix resin less prone to brittle fracture. Bimodal polyethylene resins have two melting peaks. To ensure good creep resistance when used as liquid cooling plate protection, the temperature difference between the first and second melting peaks of the bimodal polyethylene resin should be controlled within 10-15℃.

[0045] It should be noted that the matrix resin of the polyolefin resin foam sheet of the present invention has a complex structure, such as polypropylene and polyethylene blend, polypropylene block copolymer, or polyethylene bimodal distribution, which may cause its DSC curve to show multiple melting peaks. In this case, the DSC melting peak temperature T of the polyolefin resin foam sheet is... m It is uniformly defined as the peak with the highest temperature among multiple melting peaks.

[0046] <Foaming Agent> The polyolefin foamed resin sheet of the present invention is prepared by adding a gas-generating decomposable foaming agent to the matrix. The decomposable foaming agent is generated by heating to decompose the foaming agent and produce gas, primarily nitrogen, carbon monoxide, ammonia, and carbon dioxide. Examples of such gases include azodicarbonamide, sodium bicarbonate, ammonium carbonate, ammonium bicarbonate, azobisisobutyronitrile (AIBN), benzenesulfonyl hydrazine, and one or more of dinitrosopeptimethylenetetramine (DPT). To obtain an environmentally friendly foam that meets the requirements of contouring processes, azodicarbonamide is particularly preferred as the chemical foaming agent for the polyolefin resin foam sheet.

[0047] Crosslinking aids Since the polyolefin resin sheet of the present invention is a cross-linked resin foam, a cross-linking aid is added during the cross-linking process. The cross-linking aid includes one or more of dicumyl peroxide (DCP), divinylbenzene, cellulose triacetate (TAC), triallyl isocyanurate (TAIC), trimethylolpropane trimethacrylate (TMPTMA), and vinyl ethylbenzene. In particular, for the difficult cross-linking characteristics of polypropylene resin, it is preferable to use a multifunctional monomer as a cross-linking aid to improve the melt strength of the polyolefin resin and enhance its dimensional stability.

[0048] <Other adjuvants> Considering that the polyolefin resin of this invention needs to meet special performance requirements such as flame retardancy, aging resistance, and coloring when used as a buffer pad for liquid cooling plates in new energy batteries, the additives are specifically selected: the flame retardant additive can be one or more of aluminum hydroxide, magnesium hydroxide, pentaerythritol, melamine, melamine polyphosphate, piperazine pyrophosphate, triazine triamine compounds, antimony trioxide, decabromodiphenyl ethane, and decabromodiphenyl ether for synergistic compounding; the antioxidant can be one or two of hindered phenolic antioxidant 1010, phosphite antioxidant 168, thioester antioxidant DLTDP, and DSTDP for synergistic enhancement; the colorant is selected from carbon black materials including but not limited to pigment carbon black, rubber reinforcing carbon black, and superconducting carbon black.

[0049] <Battery liquid cooling plate made of contoured foam> The conformal foam for battery liquid cooling plates described in this invention is made by mixing the resin matrix, foaming agent, crosslinking aid, flame retardant, antioxidant, etc., through an extruder, and can be extruded and molded by a single-screw extruder or a twin-screw extruder to obtain the desired pre-foamed sheets or blocks containing foaming agent or pure resin.

[0050] The specific implementation method of the polyolefin resin foam sheet contained in the conformal foam for the battery liquid cooling plate of the present invention is as follows: Polypropylene resin, polyethylene resin, decomposable foaming agent, and other additives such as crosslinking agents and flame retardants are melt-mixed and the mixture is mixed at a controlled melt temperature of 160℃-180℃. The mixture is then cooled and shaped through a coat hanger-type or fishtail-type extrusion die to obtain a pre-foamed body containing the foaming agent.

[0051] The pre-foamed sheet of the cross-linked foam is subjected to radiation cross-linking. Electron rays, alpha rays, beta rays, gamma rays, and X-rays can all be used to perform the cross-linking reaction on the pre-foamed sheet containing cross-linking aids. For stable industrial production, electron rays are preferred for radiation cross-linking. The radiation-cross-linked pre-foamed body is then passed through a high-temperature drying tunnel. The temperature of the drying tunnel needs to be higher than the decomposition temperature of the foaming agent (220°C). To prevent resin decomposition at high temperatures and ensure the mechanical properties of the resin matrix, the foaming temperature needs to be lower than 310°C. Therefore, the preferred foaming temperature is between 220-310°C, with a further preferred range of 230°C-260°C. Hot air is circulated at a constant speed to ensure uniform heating of the pre-foamed body throughout the foaming process, allowing the foaming agent to fully decompose and release gas, thus completing the foaming process. By controlling the foaming temperature and speed, the total amount of gas generated is ensured to meet the density requirements of this patent for polyolefin resin foam.

[0052] Furthermore, during the foaming production process, the ratio of the traction rate in the MD direction to the traction rate before foaming is between 1.1 and 1.9, and more preferably between 1.2 and 1.7. When the rate ratio is less than 1.1, material accumulation will occur due to the volume expansion during foaming, resulting in wrinkles and obvious abnormalities in the appearance of the product. When the rate ratio is greater than 1.9, the excessively fast traction rate will cause a large amount of internal stress to remain in the cooled and shaped sheet. When the residual stress is released during the conformal preheating process, excessive shrinkage in the MD direction will occur. According to the principle of mass conservation, when the shrinkage in the MD direction is too large, there will also be correlated dimensional changes in the ZD and TD directions. Therefore, the traction rate in the MD direction before and during foaming is also an important factor affecting the dimensional changes in the MD, TD, and ZD directions.

[0053] Under the defined conditions of the matrix resin, crosslinking, stretching, and foaming processes, polyolefin resin foam sheets can be dried in an oven at a temperature t of T ± 5℃, where T = T m Under the condition of +(G / 4)℃, the dimensional change rate in the MD direction is controlled within 0 to -5%, the TD direction within -3% to +5%, and the ZD direction within 0 to +5%, which significantly improves the dimensional stability of the material in contour processing.

[0054] Simultaneously, during this process, the average cell diameter, closed-cell ratio, and cell wall thickness are also determined. With the matrix resin also determined, the thermal conductivity of the foam can be controlled to be less than 0.05 W / m·K, and more preferably less than 0.045 W / m·K. Within the range of K.

[0055] <Battery liquid cooling plate made using a shape-mimicking device> The battery liquid cooling plate profile described in this invention is a profiled part structure made by preheating and cooling the battery liquid cooling plate profiled foam at high temperature.

[0056] High-temperature preheating involves cutting the foam sheet into a certain size, placing it in an oven for heating treatment, setting the oven temperature t within the range of T±5℃, and continuing heating for 2-5 minutes. At this time, both the surface layer and the core layer of the foam sheet need to reach a fully preheated state.

[0057] Cooling and shaping involves quickly transferring the preheated foamed resin sheet into a mold with a flow channel structure, and then cooling and shaping it using a molding press. To ensure dimensional stability and production efficiency, it is preferable to use cooling water to shape the contoured parts, which are then cut to obtain contoured parts of specific dimensions.

[0058] The flow channel structure of the mold complements the uneven surface features of the battery liquid cooling plate. The molding pressure is 0.5-5MPa, and the cooling temperature is 10-40℃. If the temperature is too low, the product will shrink drastically during cooling, resulting in a smaller final product size. If the temperature exceeds 40℃, unless the holding time is extended, the product cannot be fully cooled and shaped, leading to dimensional springback and instability in the dimensions of the parts.

[0059] The following description uses several embodiments related to the present invention, but it is not intended to limit the present invention to these embodiments.

[0060] Example 1: 60g of polypropylene resin (brand: Sinopec K8003, melt flow rate of 2.9g / 10min under 230℃ / 2.16kg load conditions) and 40g of resin with a density of 0.92g / cm³ were mixed. 3 Polyethylene resin (brand name: Maoming Petrochemical 7042, melt flow rate of 1.9g / 10min under 190℃ / 2.16kg load) was mixed with 3.5g azodicarbonamide and 0.8g triallyl isocyanurate (TAIC) in an extruder at an extrusion temperature of 170℃.

[0061] The pre-foamed sheet was subjected to electron beam radiation crosslinking treatment with an absorbed dose of 100 kGy, and then foamed at 240°C. The ratio of the MD traction rate to the pre-foaming rate was controlled to be 1.3, and the sheet was naturally cooled to obtain a polyolefin resin foamed sheet.

[0062] The resulting polyolefin resin foam sheet, T m The temperature was set at 145°C, the degree of crosslinking G was 32%, the oven temperature t was set at 153°C, and the heating was carried out for 3 minutes to obtain the conformal foam for the battery liquid cooling plate of Example 1.

[0063] Example 2 100g of polypropylene resin (brand: Qilu Petrochemical T30S, melt flow rate of 2.6g / 10min under 230℃ / 2.16kg load) was mixed with 3.4g of azodicarbonamide and 0.8g of triallyl isocyanurate (TAIC) in an extruder. The extrusion temperature was 175℃, and the mixture was then molded and cooled.

[0064] The pre-foamed sheet was subjected to electron beam radiation crosslinking treatment with an absorbed dose of 100 kGy, and then foamed at 240°C. The ratio of the MD traction rate to the pre-foaming rate was controlled to be 1.3, and the sheet was naturally cooled to obtain a polyolefin resin foamed sheet.

[0065] The resulting polyolefin resin foam sheet, T m The temperature was set at 148°C, the degree of crosslinking G was 28%, the oven temperature t was set at 155°C, and the heating was carried out for 3 minutes to obtain the conformal foam for the battery liquid cooling plate in Example 2.

[0066] Example 3 60g of polypropylene resin (brand: Qilu Petrochemical QPR01, melt flow rate of 0.21g / 10min under 230℃ / 2.16kg load conditions) and 40g of [unclear - possibly a specific resin or product] with a density of 0.91g / cm³ were mixed. 3 Polyethylene resin (brand name: Exxon XP7052, melt flow rate of 0.5g / 10min under 190℃ / 2.16kg load) was mixed with 4.0g azodicarbonamide and 0.8g triallyl isocyanurate (TAIC) in an extruder. The extrusion temperature was 172℃, and the mixture was cooled and shaped in a mold.

[0067] The pre-foamed sheet was subjected to electron beam radiation crosslinking treatment with an absorbed dose of 100 kGy, and then foamed at 240°C. The ratio of the MD traction rate to the pre-foaming rate was controlled to be 1.3, and the sheet was naturally cooled to obtain a polyolefin resin foamed sheet.

[0068] The resulting polyolefin resin foam sheet, T m The temperature was set at 145°C, the degree of crosslinking G was 33%, and the oven temperature t was set at 153°C. Heat setting was performed for 3 minutes to obtain the conformal foam for the battery liquid cooling plate in Example 3.

[0069] Example 4 60g of polypropylene resin (brand: Shanghai Petrochemical F280, melt flow rate of 2.8g / 10min under 230℃ / 2.16kg load) and 40g of resin with a density of 0.92g / cm³ were mixed. 3Polyethylene resin (brand name: Maoming Petrochemical 7042, melt flow rate of 1.9g / 10min under 190℃ / 2.16kg load) was mixed with 1.8g azodicarbonamide and 0.8g triallyl isocyanurate (TAIC) in an extruder. The extrusion temperature was 170℃, and the mixture was cooled and shaped in a mold.

[0070] The pre-foamed sheet was subjected to electron beam radiation crosslinking treatment with an absorbed dose of 100 kGy, and then foamed at 240°C. The ratio of the MD traction rate to the pre-foaming rate was controlled to be 1.3, and the sheet was naturally cooled to obtain a polyolefin resin foamed sheet.

[0071] The resulting polyolefin resin foam sheet, T m The temperature was set at 147°C, the degree of crosslinking G was 30%, the oven temperature t was set at 154°C, and the heating was carried out for 3 minutes to obtain the conformal foam for the battery liquid cooling plate in Example 4.

[0072] Example 5 60g of polypropylene resin (brand: Qilu Petrochemical T36F, melt flow rate of 2.0g / 10min under 230℃ / 2.16kg load conditions) and 40g of resin with a density of 0.93g / cm³ were mixed. 3 Polyethylene resin (brand: Wuhan Ethylene 35B, melt flow rate of 2.0g / 10min under 190℃ / 2.16kg load) was mixed with 2.0g azodicarbonamide and 1.5g triallyl isocyanurate (TAIC) in an extruder. The extrusion temperature was 170℃, and the mixture was then molded and cooled.

[0073] The pre-foamed sheet was subjected to electron beam radiation crosslinking treatment with an absorbed dose of 180 kGy, and then foamed at 240°C. The ratio of the MD traction rate to the pre-foaming rate was controlled to be 1.3, and the sheet was naturally cooled to obtain a polyolefin resin foamed sheet.

[0074] The resulting polyolefin resin foam sheet, T m The temperature was set at 145°C, the degree of crosslinking G was 60%, and the oven temperature t was set at 165°C. The mixture was heated for 2 minutes to achieve heat setting, resulting in the conformal foam for the battery liquid cooling plate in Example 5.

[0075] Example 6 60g of polypropylene resin (brand: Shanghai Petrochemical F280, melt flow rate of 2.8g / 10min under 230℃ / 2.16kg load) and 40g of resin with a density of 0.92g / cm³ were mixed. 3Polyethylene resin (brand name: Maoming Petrochemical 7042, melt flow rate of 1.9g / 10min under 190℃ / 2.16kg load) was mixed with 1.8g azodicarbonamide and 0.8g triallyl isocyanurate (TAIC) in an extruder. The extrusion temperature was 170℃, and the mixture was cooled and shaped in a mold.

[0076] The pre-foamed sheet was subjected to electron beam radiation crosslinking treatment with an absorbed dose of 100 kGy, and then foamed at 220°C. The ratio of the MD traction rate to the pre-foaming rate was controlled to be 1.3, and the sheet was naturally cooled to obtain a polyolefin resin foamed sheet.

[0077] The resulting polyolefin resin foam sheet, T m The temperature was set at 147°C, the degree of crosslinking G was 30%, the oven temperature t was set at 154°C, and the heating was carried out for 5 minutes to obtain the conformal foam for the battery liquid cooling plate in Example 6.

[0078] Example 7 60g of polypropylene resin (brand: Qilu Petrochemical QPR01, melt flow rate of 0.21g / 10min under 230℃ / 2.16kg load conditions) and 40g of [unclear text - possibly a product name or product] with a density of 0.93g / cm³ were mixed. 3 Polyethylene resin (brand: Wuhan Ethylene 35B, melt flow rate of 2.0g / 10min under 190℃ / 2.16kg load) was mixed with 3.7g azodicarbonamide and 0.8g triallyl isocyanurate (TAIC) in an extruder. The extrusion temperature was 170℃, and the mixture was then molded and cooled.

[0079] The pre-foamed sheet was subjected to electron beam radiation crosslinking treatment with an absorbed dose of 110 kGy, and then foamed at 260°C. The ratio of the MD traction rate to the pre-foaming rate was controlled to be 1.3, and the sheet was naturally cooled to obtain a polyolefin resin foamed sheet.

[0080] The resulting polyolefin resin foam sheet, T m The temperature was set at 145°C, the degree of crosslinking G was 32%, and the oven temperature t was set at 149°C. Heat setting was performed for 3 minutes to obtain the conformal foam for the battery liquid cooling plate in Example 7.

[0081] Example 8 60g of polypropylene resin (brand: Shanghai Petrochemical F280, melt flow rate of 2.8g / 10min under 230℃ / 2.16kg load) and 40g of resin with a density of 0.92g / cm³ were mixed. 3Polyethylene resin (brand: Maoming Petrochemical 7042, melt flow rate of 1.9g / 10min under 190℃ / 2.16kg load) was mixed with 3g azodicarbonamide and 0.8g triallyl isocyanurate (TAIC) in an extruder. The extrusion temperature was 170℃, and the mixture was then molded and cooled.

[0082] The pre-foamed sheet was subjected to electron beam radiation crosslinking treatment with an absorbed dose of 115 kGy, and then foamed at 240°C. The ratio of the MD traction rate to the pre-foaming rate was controlled to be 1.1, and the sheet was naturally cooled to obtain a polyolefin resin foamed sheet.

[0083] The resulting polyolefin resin foam sheet, T m The temperature was set at 147°C, the degree of crosslinking G was 34%, the oven temperature t was set at 155.5±5°C, and the heating was carried out for 3 minutes to obtain the conformal foam for the battery liquid cooling plate in Example 8.

[0084] Example 9 60g of polypropylene resin (brand: Qilu Petrochemical QPR01, melt flow rate of 0.21g / 10min under 230℃ / 2.16kg load conditions) and 40g of [unclear text - possibly a product name or product] with a density of 0.93g / cm³ were mixed. 3 Polyethylene resin (brand: Wuhan Ethylene 35B, melt flow rate of 2.0g / 10min under 190℃ / 2.16kg load) was mixed with 3g azodicarbonamide and 0.7g triallyl isocyanurate (TAIC) in an extruder. The extrusion temperature was 170℃, and the mixture was then molded and cooled.

[0085] The pre-foamed sheet was subjected to electron beam radiation crosslinking treatment with an absorbed dose of 100 kGy, and then foamed at 240°C. The ratio of the MD traction rate to the pre-foaming rate was controlled to be 1.9, and the sheet was naturally cooled to obtain a polyolefin resin foamed sheet.

[0086] The resulting polyolefin resin foam sheet, T m The temperature was set at 145°C, the degree of crosslinking G was 25%, the oven temperature t was set at 151°C, and the heating was carried out for 3 minutes to obtain the conformal foam for battery liquid cooling plate in Example 9.

[0087] Example 10 60g of polypropylene resin (brand: Shanghai Petrochemical F282, melt flow rate of 2.8g / 10min under 230℃ / 2.16kg load conditions) and 40g of [unclear text - possibly a product name or substance] with a density of 0.93g / cm³ were mixed. 3Polyethylene resin (brand: Maoming Petrochemical 7042, melt flow rate of 1.9g / 10min under 190℃ / 2.16kg load) was mixed with 3g azodicarbonamide and 0.8g triallyl isocyanurate (TAIC) in an extruder. The extrusion temperature was 170℃, and the mixture was then molded and cooled.

[0088] The pre-foamed sheet was subjected to electron beam radiation crosslinking treatment with an absorbed dose of 120 kGy, and then foamed at 240°C. The ratio of the MD traction rate to the pre-foaming rate was controlled to be 1.3, and the sheet was naturally cooled to obtain a polyolefin resin foamed sheet.

[0089] The resulting polyolefin resin foam sheet, T m The temperature was set at 147°C, the degree of crosslinking G was 45%, the oven temperature t was set at 161°C, and the heating was carried out for 3 minutes to obtain the conformal foam for battery liquid cooling plate in Example 10.

[0090] Example 11 60g of polypropylene resin (brand: Qilu Petrochemical QPR01, melt flow rate of 0.21g / 10min under 230℃ / 2.16kg load conditions) and 40g of [unclear text - possibly a product name or product] with a density of 0.93g / cm³ were mixed. 3 Polyethylene resin (brand name: Wuhan Ethylene 35B, melt flow rate of 2.0g / 10min under 190℃ / 2.16kg load) was mixed with 3.5g azodicarbonamide and 0.8g triallyl isocyanurate (TAIC) in an extruder. The extrusion temperature was 170℃, and the mixture was cooled and shaped in a mold.

[0091] The pre-foamed sheet was subjected to electron beam radiation crosslinking treatment with an absorbed dose of 100 kGy, and then foamed at 240°C. The ratio of the MD traction rate to the pre-foaming rate was controlled to be 1.3, and the sheet was naturally cooled to obtain a polyolefin resin foamed sheet.

[0092] The resulting polyolefin resin foam sheet, T m The temperature was set at 145°C, the degree of crosslinking G was 40%, the oven temperature t was set at 155°C, and the heating was carried out for 3 minutes to obtain the conformal foam for battery liquid cooling plate in Example 11.

[0093] Example 12 65g of propylene-α-olefin random copolymer resin (self-made, with a melt flow rate of 4.2g / 10min under 230℃ / 2.16kg load conditions, containing 3wt% soft segment and 55% crystallinity) and 35g of resin with a density of 0.92g / cm³ were mixed. 3Bimodal polyethylene resin (brand name: FM1810, melt flow rate of 2.1g / 10min under 190℃ / 2.16kg load conditions, bimodal temperature difference of 10.5℃) was mixed with 2.0g azodicarbonamide and 0.8g triallyl isocyanurate (TAIC) in an extruder at an extrusion temperature of 170℃ and then cooled and shaped in a mold.

[0094] The pre-foamed sheet was subjected to electron beam radiation crosslinking treatment with an absorbed dose of 100 kGy, and then foamed at 245°C. The ratio of the MD traction rate to the pre-foaming rate was controlled to be 1.2, and the sheet was naturally cooled to obtain a polyolefin resin foamed sheet.

[0095] The resulting polyolefin resin foam sheet, T m The temperature was set at 147°C, the degree of crosslinking G was 35%, the oven temperature t was set at 155°C, and the heating was carried out for 3 minutes to obtain the conformal foam for the battery liquid cooling plate of Example 12.

[0096] Example 13 70g of propylene-α-olefin random copolymer resin (self-made, with a melt flow rate of 3.9g / 10min under 230℃ / 2.16kg load conditions, containing 3.5wt% soft segments and 50% crystallinity) and 30g of resin with a density of 0.92g / cm³ were mixed. 3 Bimodal polyethylene resin (brand name: FM1810, melt flow rate of 2.1g / 10min under 190℃ / 2.16kg load conditions, bimodal temperature difference of 11.5℃) was mixed with 2.3g azodicarbonamide and 0.8g triallyl isocyanurate (TAIC) in an extruder at an extrusion temperature of 170℃ and then cooled and shaped in a mold.

[0097] The pre-foamed sheet was subjected to electron beam radiation crosslinking treatment with an absorbed dose of 100 kGy, and then foamed at 245°C. The ratio of the MD traction rate to the pre-foaming rate was controlled to be 1.3, and the sheet was naturally cooled to obtain a polyolefin resin foamed sheet.

[0098] The resulting polyolefin resin foam sheet, T m The temperature was set at 143°C, the degree of crosslinking G was 38%, the oven temperature t was set at 152°C, and the heating was carried out for 3 minutes to obtain the conformal foam for battery liquid cooling plate in Example 13.

[0099] Example 14 60g of polypropylene resin (brand: Qilu Petrochemical T30S, melt flow rate of 2.6g / 10min under 230℃ / 2.16kg load conditions) and 40g of resin with a density of 0.93g / cm³ were mixed. 3Polyethylene resin (brand name: Maoming Petrochemical 7042, melt flow rate of 1.9g / 10min under 190℃ / 2.16kg load) was mixed with 1.5g azodicarbonamide, 0.8g triallyl isocyanurate (TAIC) and 0.2g alumina in an extruder. The extrusion temperature was 170℃, and the mixture was cooled and shaped in a mold.

[0100] The pre-foamed sheet was subjected to electron beam radiation crosslinking treatment with an absorbed dose of 100 kGy, and then foamed at 240°C. The ratio of the MD traction rate to the pre-foaming rate was controlled to be 1.3, and the sheet was naturally cooled to obtain a polyolefin resin foamed sheet.

[0101] The resulting polyolefin resin foam sheet, T m The temperature was set at 148°C, the degree of crosslinking G was 33%, the oven temperature t was set at 156°C, and the heating was carried out for 3 minutes to obtain the conformal foam for battery liquid cooling plate in Example 14.

[0102] Example 15 60g of polypropylene resin (brand: Qilu Petrochemical QPR01, melt flow rate of 0.21g / 10min under 230℃ / 2.16kg load conditions) and 40g of [unclear text - possibly a product name or product] with a density of 0.93g / cm³ were mixed. 3 Polyethylene resin (brand: Wuhan Ethylene 35B, melt flow rate of 2.0g / 10min under 190℃ / 2.16kg load) was mixed with 1.0g azodicarbonamide and 0.8g triallyl isocyanurate (TAIC) in an extruder. The extrusion temperature was 170℃, and the mixture was then molded and cooled.

[0103] The pre-foamed sheet was subjected to electron beam radiation crosslinking treatment with an absorbed dose of 95 kGy, and then foamed at 200°C. The ratio of the MD traction rate to the pre-foaming rate was controlled to be 1.3, and the sheet was naturally cooled to obtain a polyolefin resin foamed sheet.

[0104] The resulting polyolefin resin foam sheet, T m The temperature was set at 145°C, the degree of crosslinking G was 32%, the oven temperature t was set at 153°C, and the heating was carried out for 3 minutes to obtain the conformal foam for the battery liquid cooling plate of Example 15.

[0105] Comparative Example 1 35g of polypropylene resin (brand: Sinopec K8003, melt flow rate of 2.0g / 10min under 230℃ / 2.16kg load conditions) and 55g of resin with a density of 0.93g / cm³ were mixed. 3Polyethylene resin (brand: Wuhan Ethylene 35B, melt flow rate of 2.0g / 10min under 190℃ / 2.16kg load) was mixed with 4.6g azodicarbonamide and 0.8g triallyl isocyanurate (TAIC) in an extruder. The extrusion temperature was 170℃, and the mixture was cooled and shaped in a mold.

[0106] The pre-foamed sheet was subjected to electron beam radiation crosslinking treatment with an absorbed dose of 100 kGy, and then foamed at 240°C. The ratio of the MD traction rate to the pre-foaming rate was controlled to be 1.3, and the sheet was naturally cooled to obtain a polyolefin resin foamed sheet.

[0107] The resulting polyolefin resin foam sheet, T m The temperature was set at 145℃, the degree of crosslinking G was 50%, the oven temperature t was set at 157℃, and the heating was carried out for 3 minutes to obtain the conformal foam for the battery liquid cooling plate of Comparative Example 1.

[0108] Comparative Example 2 60g of polypropylene resin (brand: Wuhan Petrochemical T30S, melt flow rate of 2.0g / 10min under 230℃ / 2.16kg load conditions) and 40g of resin with a density of 0.97g / cm³ were mixed. 3 Polyethylene resin (brand: Huajin Chemical T5070, melt flow rate of 5.2g / 10min under 190℃ / 2.16kg load) was mixed with 4.0g azodicarbonamide and 0.8g triallyl isocyanurate (TAIC) in an extruder. The extrusion temperature was 170℃, and the mixture was cooled and shaped in a mold.

[0109] The pre-foamed sheet was subjected to electron beam radiation crosslinking treatment with an absorbed dose of 50 kGy, and then foamed at 240°C. The ratio of the MD traction rate to the pre-foaming rate was controlled to be 1.3, and the sheet was naturally cooled to obtain a polyolefin resin foamed sheet.

[0110] The resulting polyolefin resin foam sheet, T m The temperature was set at 145℃, the degree of crosslinking G was 15%, the oven temperature t was set at 148℃, and the heating was carried out for 3 minutes to obtain the conformal foam for the battery liquid cooling plate of Comparative Example 2.

[0111] Comparative Example 3 60g of polypropylene resin (brand: Qilu Petrochemical QPR01, melt flow rate of 0.21g / 10min under 230℃ / 2.16kg load conditions) and 40g of [unclear text - possibly a product name or product] with a density of 0.93g / cm³ were mixed. 3Polyethylene resin (brand: Wuhan Ethylene 35B, melt flow rate of 2.0g / 10min under 190℃ / 2.16kg load) was mixed with 6g azodicarbonamide and 0.8g triallyl isocyanurate (TAIC) in an extruder. The extrusion temperature was 170℃, and the mixture was then molded and cooled.

[0112] The pre-foamed sheet was subjected to electron beam radiation crosslinking treatment with an absorbed dose of 100 kGy, and then foamed at 240°C. The ratio of the MD traction rate to the pre-foaming rate was controlled to be 1.3, and the sheet was naturally cooled to obtain a polyolefin resin foamed sheet.

[0113] The resulting polyolefin resin foam sheet, T m The temperature was set at 145℃, the degree of crosslinking G was 30%, the oven temperature t was set at 152℃, and the heating was carried out for 3 minutes to obtain the conformal foam for the battery liquid cooling plate of Comparative Example 3.

[0114] Comparative Example 4 60g of polypropylene resin (brand: Sinopec K8004, melt flow rate of 2.0g / 10min under 230℃ / 2.16kg load conditions) and 40g of [unclear text - possibly a product name or product] with a density of 0.93g / cm³ were mixed. 3 2g of azodicarbonamide was added to polyethylene resin (brand: Wuhan Ethylene 35B, melt flow rate of 2.0g / 10min under 190℃ / 2.16kg load) and mixed in an extruder. The extrusion temperature was 170℃, and the mixture was then molded and cooled.

[0115] The pre-foamed sheet was subjected to electron beam radiation crosslinking treatment with an absorbed dose of 30 kGy, and then foamed at 240°C. The ratio of the MD traction rate to the pre-foaming rate was controlled to be 1.3, and the sheet was naturally cooled to obtain a polyolefin resin foamed sheet.

[0116] The resulting polyolefin resin foam sheet, T m The temperature was set at 145℃, the degree of crosslinking G was 15%, the oven temperature t was set at 148℃, and the heating was carried out for 3 minutes to obtain the conformal foam for the battery liquid cooling plate of Comparative Example 4.

[0117] Comparative Example 5 60g of polypropylene resin (brand: Qilu Petrochemical T30S, melt flow rate of 2.6g / 10min under 230℃ / 2.16kg load conditions) and 40g of resin with a density of 0.92g / cm³ were mixed. 3 Polyethylene resin (brand name: Maoming Petrochemical 7042, melt flow rate of 1.9g / 10min under 190℃ / 2.16kg load) was mixed with 4.0g azodicarbonamide and 0.8g triallyl isocyanurate (TAIC) in an extruder. The extrusion temperature was 170℃, and the mixture was cooled and shaped in a mold.

[0118] The pre-foamed sheet was subjected to electron beam radiation crosslinking treatment with an absorbed dose of 105 kGy, and then foamed at 240°C. The ratio of the MD traction rate to the pre-foaming rate was controlled to be 1, and the sheet was naturally cooled to obtain a polyolefin resin foamed sheet.

[0119] The resulting polyolefin resin foam sheet, T m The temperature was set at 148℃, the degree of crosslinking G was 35%, the oven temperature t was set at 156℃, and the heating was carried out for 3 minutes to obtain the conformal foam for the battery liquid cooling plate of Comparative Example 5.

[0120] Comparative Example 6 60g of polypropylene resin (brand: Qilu Petrochemical QPR01, melt flow rate of 0.21g / 10min under 230℃ / 2.16kg load conditions) and 40g of [unclear text - possibly a product name or product] with a density of 0.93g / cm³ were mixed. 3 Polyethylene resin (brand: Wuhan Ethylene 35B, melt flow rate of 2.0g / 10min under 190℃ / 2.16kg load) was mixed with 4.0g azodicarbonamide and 0.8g triallyl isocyanurate (TAIC) in an extruder. The extrusion temperature was 170℃, and the mixture was then molded and cooled.

[0121] The pre-foamed sheet was subjected to electron beam radiation crosslinking treatment with an absorbed dose of 105 kGy, and then foamed at 240°C. The ratio of the MD traction rate to the pre-foaming rate was controlled to be 2, and the sheet was naturally cooled to obtain a polyolefin resin foamed sheet.

[0122] The resulting polyolefin resin foam sheet, T m The temperature was set at 145℃, the degree of crosslinking G was 34%, the oven temperature t was set at 153.5±5℃, and the heating was carried out for 3 minutes for heat setting to obtain the conformal foam for the battery liquid cooling plate of Comparative Example 6.

[0123] Comparative Example 7 60g of polypropylene resin (brand: Sinopec K8003, melt flow rate of 2.9g / 10min under 230℃ / 2.16kg load conditions) and 40g of resin with a density of 0.92g / cm³ were mixed. 3 Polyethylene resin (brand name: Maoming Petrochemical 7042, melt flow rate of 1.9g / 10min under 190℃ / 2.16kg load) was mixed with 3.5g azodicarbonamide and 0.8g triallyl isocyanurate (TAIC) in an extruder. The extrusion temperature was 170℃, and the mixture was cooled and shaped in a mold.

[0124] The pre-foamed sheet was subjected to electron beam radiation crosslinking treatment with an absorbed dose of 100 kGy, and then foamed at 240°C. The ratio of the MD traction rate to the pre-foaming rate was controlled to be 1.3, and the sheet was naturally cooled to obtain a polyolefin resin foamed sheet.

[0125] The resulting polyolefin resin foam sheet, T m The temperature was set at 145℃, the degree of crosslinking G was 32%, and the oven temperature t was set at 142℃. Heat setting was performed for 3 minutes to obtain the conformal foam for the battery liquid cooling plate of Comparative Example 7.

[0126] Comparative Example 8 60g of polypropylene resin (brand: Sinopec K8003, melt flow rate of 2.9g / 10min under 230℃ / 2.16kg load conditions) and 40g of resin with a density of 0.92g / cm³ were mixed. 3 Polyethylene resin (brand name: Maoming Petrochemical 7042, melt flow rate of 1.9g / 10min under 190℃ / 2.16kg load) was mixed with 3.5g azodicarbonamide and 0.8g triallyl isocyanurate (TAIC) in an extruder. The extrusion temperature was 170℃, and the mixture was cooled and shaped in a mold.

[0127] The pre-foamed sheet was subjected to electron beam radiation crosslinking treatment with an absorbed dose of 100 kGy, and then foamed at 240°C. The ratio of the MD traction rate to the pre-foaming rate was controlled to be 1.3, and the sheet was naturally cooled to obtain a polyolefin resin foamed sheet.

[0128] The resulting polyolefin resin foam sheet, T m The temperature was set at 145℃, the degree of crosslinking G was 32%, the oven temperature t was set at 164℃, and the heating was carried out for 3 minutes to obtain the conformal foam for the battery liquid cooling plate of Comparative Example 8.

[0129] The DSC melting peak temperature T of the polyolefin resin foam sheets obtained in Examples 1-15 and Comparative Examples 1-8 was measured. m The crosslinking degree, thermal conductivity, thickness, and density were measured as shown in Table 1. The dimensional change rates in the MD, TD, and ZD directions, impact absorption rate, compressive strength, liquid cooling plate adhesion, and condensation effect of the polyolefin resin foam sheets obtained in Examples 1-15 and Comparative Examples 1-8 were measured at temperature T. The results are shown in Table 2. Test method: 1-DSC melting peak temperature (T) m ) Test method: Differential scanning calorimetry (DSC) Standard basis: ISO 11357-3 Plastics – Differential scanning calorimetry (DSC) – Part 3: Determination of melting and crystallization temperatures and enthalpies Operating procedure: Place the sample in the DSC instrument under a nitrogen atmosphere with a nitrogen flow rate of 50 ml / min, and scan at a heating rate of 10 °C / min. Record the highest peak temperature of the endothermic peak.

[0130] 2-Degree of crosslinking (G%) a. Take a sample from the foamed sheet and accurately weigh the sample A (mg). b. Wrap the sample in a 200-mesh metal mesh, then place the mesh-wrapped sample in an oil bath heated to boiling xylene and let it stand for 12 hours. The insoluble matter can be collected within the metal mesh through filtration; after vacuum drying, accurately weigh the insoluble matter B (mg). c. Calculate the degree of crosslinking (mass%): Degree of crosslinking (mass%) = 100% × (B / A).

[0131] 3- Thermal conductivity (measured by plate method) a. Place the sample with thickness d between the heating plate and cooling plate of the flat plate thermal conductivity meter, adjust the position so that the sample completely covers the surface of the heating plate, and ensure that the sample is in close contact with the plate surface without air gaps; b. Set the heating plate power to 100W, turn on the cooling system, control the water temperature at 20℃, and start the test program; continuously monitor the upper and lower surface temperatures T1 and T2 of the sample and the heat flow Q through the sample, and record the data after the temperature field stabilizes (temperature fluctuation < 0.1℃ within 30 consecutive minutes).

[0132] c. Calculate the thermal conductivity using Fourier's law: λ=

[0133] in: Q represents the heat flow (W) under steady-state conditions. d is the sample thickness; A is the contact area between the sample and the heating plate; T represents the temperature difference (K) between the upper and lower surfaces.

[0134] 4-Thickness and Density Measurement a. Cut a square sample with dimensions of 100mm × 100mm from the foamed sheet, ensuring that the sample surface is flat and free of obvious defects. Use a micrometer to measure the thickness at 5 different locations on the sample, take the average value as the sample thickness d, and calculate the volume V of the square sample.

[0135] b. Use a balance to determine the mass m of the foam material.

[0136] c. Density ρ = m / V.

[0137] 5- Dimensional change rate at a specific temperature (MD / TD / ZD direction) a. Cut a square specimen with dimensions of 150mm × 150mm × tmm (t is the original thickness of the sheet) from the foamed sheet. Draw a 100mm × 100mm square mark at the center of the specimen, ensuring the surface of the specimen is flat, without damage or obvious cell defects. Prepare 3 parallel specimens for each test group. Measure the initial dimensions of the specimens in the MD (longitudinal), TD (transverse), and ZD (thickness direction) directions, respectively. MD1 L TD1 L ZD1 .

[0138] b. Set the oven temperature range t to T ± 5℃, where T = T m +(G / 4)℃ (T) m (where G is the highest melting peak temperature of DSC and G is the degree of crosslinking). After the temperature stabilizes, place the sample horizontally in the middle of the oven, avoiding stacking. The heating time is 5 minutes.

[0139] c. After removing the sample, immediately place it in an environment of (23±2)℃ to cool naturally for 30 minutes, and quickly measure the final dimensions in each direction using the same micrometer, which are L. MD2 L TD2 L ZD2 .

[0140] d. The dimensional change rate in each direction is calculated as follows: Dimensional change rate in the MD direction: (L) MD1 -L MD2 ) / L MD1 ×100% Dimensional change rate in the TD direction: (L) TD1 -L TD2 ) / L TD1 ×100% ZD direction dimensional change rate: (L ZD1 -L ZD2 ) / L ZD1 ×100%.

[0141] 6-Impact absorption rate (%) In a standard laboratory environment, prepare a 100mm × 100mm foam sample and place it on the platform of the stress sensing device at the bottom. Use a 33g ball to drop freely from a height of 30cm, and read the maximum stress before and after placing the foam. Impact absorption = (maximum stress value before placing foam - maximum stress value after placing foam) / maximum stress value before placing foam × 100%.

[0142] 7- Adhesion effect with liquid cooling plate The foamed sheet was cut into samples with the same dimensions as the simulated liquid-cooled plate, and preheated at high temperature for 3 minutes within the range of T±5℃ according to the conditions in the dimensional change rate test method, where T=T m +(G / 4)℃; Bonding and shaping: The preheated sample is quickly transferred to a simulated liquid-cooled plate mold, a pressure of 3MPa is applied, and it is cooled and shaped at 25℃ for 10min; Based on the dimensions of the cold plate in the project drawings, a coordinate measuring machine (CMM) was used to verify the dimensions to ensure that the flow channels and non-flow channels meet the assembly dimensional tolerances. If the tolerance is too small, the flow channels of the parts cannot fall into the flow channels of the liquid cooler during assembly, which is considered "too loose" assembly and will cause vibration and abnormal noise when the car is running. This is recorded as a fit effect "C". When the CMM dimensions of the parts are larger than the dimensions required by the drawings, "interference fit" will occur, which will cause positional interference during the assembly of other parts and affect the assembly of the battery pack. This is recorded as a fit effect "B". When the dimensions of the parts meet the tolerances of the drawings, there will be no abnormal noise or assembly interference. This is recorded as a fit effect "A".

[0143] 8- Effectiveness in solving the problem of condensation The foamed sheet was cut into samples with the same dimensions as the simulated liquid-cooled plate, and preheated at high temperature for 3 minutes within the range of T±5℃ according to the conditions in the dimensional change rate test method, where T=T m +(G / 4)℃; Bonding and shaping: The preheated sample is quickly transferred to a simulated liquid-cooled plate mold, a pressure of 3MPa is applied, and it is cooled and shaped at 25℃ for 10min; A custom-made metal plate with a jacket structure and a flow channel structure on its surface is made of 3003 aluminum alloy. It has inlet and outlet at both ends and a loop flow channel inside the plate. The plate is 200mm*200mm in size. The foamed sheet after shaping is cut into 200mm×200mm samples and tightly attached to the surface of the cold plate. At this time, coolant at a temperature of 10-15 degrees Celsius is circulated inside the metal plate for 60 minutes.

[0144] Observe the foam surface continuously for 60 minutes and record the time of condensation onset and droplet size: If noticeable droplets (diameter > 2 mm) appear within 60 minutes and converge to drip, it is considered severe condensation; denoted as "C". If no visible droplets or only a small amount of dew (0.5mm ≤ diameter < 2mm) appear within 60 minutes, and no condensation or dripping occurs, the condensation suppression effect is moderate, and it is denoted as "B". If no visible droplets or only a small amount of dew (diameter <0.5mm) appear within 60 minutes, and the area is only slightly damp, with no visible water droplets and no accumulation, the condensation suppression effect is excellent and is recorded as "A".

[0145] Table 1:

[0146] Table 2:

[0147] Based on the above embodiments and comparative examples, it can be illustrated that when the battery liquid cooling plate is controlled at the melting peak T using contoured foam... m The temperature is 140-160℃, the degree of crosslinking G is 20%-60%, and it meets the requirement of heating in an oven at T±5℃ for 2-5 minutes. When the dimensional change rate of the polyolefin resin foam sheet is 0 to -5% in the MD direction, -3% to +5% in the TD direction, and 0 to +5% in the ZD direction, it can ensure that the conformal foam of the battery liquid cooling plate can adapt to the tortuous and complex structure of the liquid cooling plate and adhere tightly, while maintaining excellent impact absorption and support stability. It can also further solve the problem of condensation at the application site. Comparative examples that do not meet the above conditions cannot have the above performance.

Claims

1. A profiled foam for a battery liquid cold plate, the foam being a polyolefin resin foamed sheet containing a polypropylene resin, characterized by, The DSC melting peak temperature T of the polyolefin resin foamed sheet m 140-160°C, the crosslinking degree G is 20-60%, the polyolefin resin foamed sheet has a dimensional change rate of 0 to -5% in the MD direction, a dimensional change rate of -3% to +5% in the TD direction, and a dimensional change rate of 0 to +5% in the ZD direction, wherein "-" indicates shrinkage and "+" indicates expansion, where T = T m + (G / 4) °C; When the polyolefin resin foamed sheet has a plurality of DSC melting peaks, the DSC melting peak temperature T m refers to the highest DSC melting peak temperature.

2. The profiled foam for a battery liquid cold plate according to claim 1, characterized by, The thermal conductivity of the foam is less than 0.05 W / m·K.

3. The profiled foam for a battery liquid cold plate according to claim 1, characterized by, The thickness h of the foam is 2-20 mm, and the foam density p is 0.08-0.3 g / cm 3 .

4. The profiled foam for a battery liquid cold plate according to claim 1, characterized by, The foam is a single polyolefin resin foamed sheet or is composed of two or more single polyolefin resin foamed sheets.

5. The profiled foam for a battery liquid cold plate according to claim 1, characterized by, The impact absorption rate of the foam is 60-90%.

6. A method of preparing a profiled foam for a battery liquid cold plate according to any one of claims 1-5, characterized by, The method comprises the following steps: (1) mixing of the base resin: The polypropylene resin and the polyethylene resin are mixed in terms of mass fraction, wherein the polypropylene resin accounts for more than 40% and less than 100%, and the polyethylene resin accounts for more than 0 and less than 60%; The polypropylene resin has a DSC highest melting peak temperature T m 140°C to 160°C, and a melt flow rate under a 230°C / 2.16 kg load condition of 0.1 to 5.0 g / 10 min. The density of the polyethylene resin is 0.91-0.96 g / cm³, and the melt flow rate under the condition of 190℃ / 2.16 kg load is 0.5-5.0 g / 10 min; (2) mixing of the auxiliary agent: At least an auxiliary agent including a foaming agent is added to the resin base of step (1); the foaming agent is a decomposition type foaming agent selected from at least one of azodicarbonamide, sodium bicarbonate, azobisisobutyronitrile, benzenesulfonyl hydrazide, and dinitrosopentamethylene tetramine; the auxiliary agent is added in an amount of 0.5%-5% of the mass of the resin base; (3) preparation of the pre-foamed body: The mixture of step (2) is melt-mixed through an extruder, the extrusion temperature is 160℃-180℃, and after being shaped through a die, the pre-foamed sheet containing the foaming agent is obtained; (4) cross-linking foaming body process: The pre-foamed sheet is subjected to radiation cross-linking treatment, and the radiation source is selected from at least one of electron rays, alpha rays, beta rays, gamma rays, and X rays; The pre-foamed sheet after cross-linking is pulled in the MD direction, and is foamed at 220℃-310℃, and the foaming temperature is controlled to be the decomposition temperature of the decomposition type foaming agent; (5) cooling and molding: The sheet after foaming obtained in step (4) is naturally cooled and molded to obtain the profiled foam for the battery liquid cooling plate.

7. The method for preparing the conformal foam for the battery liquid cooling plate according to claim 6, characterized in that, In step (1), the mass fraction of the polypropylene resin is 60%-90%, and the density of the polyethylene resin is 0.92-0.95 g / cm³.

8. The method of claim 6, wherein the method further comprises the steps of: applying a liquid resin to the mold; and curing the liquid resin to form the foam. The decomposition type foaming agent is azodicarbonamide, and the addition amount is 0.8%-3% of the mass of the resin base.

9. The method for preparing the conformal foam for the battery liquid cooling plate according to claim 6, characterized in that, In step (2), the auxiliary agent further includes a flame retardant and / or an antioxidant, the flame retardant is selected from at least one of aluminum hydroxide, magnesium hydroxide, and decabromodiphenyl ethane, and the antioxidant is selected from a hindered phenol or a phosphite antioxidant.

10. The method of claim 6, wherein the method further comprises the steps of: applying a liquid resin to the mold; and curing the liquid resin to form the foam. In step (4), a cross-linking auxiliary agent is added when the pre-foamed sheet is subjected to radiation cross-linking, and the cross-linking auxiliary agent is selected from one or more of dicumyl peroxide, divinylbenzene, cellulose triacetate, triallyl isocyanurate, trimethylolpropane trimethacrylate, and / or vinyl ethylbenzene.

11. The method of claim 6, wherein the method further comprises the steps of: applying a liquid resin to the mold; and curing the liquid resin to form the foam. In step (4), when the pre-foamed sheet after cross-linking is foamed, the ratio of the pulling rate in the MD direction to the pulling rate before foaming is 1.1-1.

9.

12. The method of claim 6, wherein the method further comprises the steps of: applying a liquid resin to the mold; and curing the liquid resin to form the foam. In step (4), the foaming temperature is 230℃-260℃.

13. A battery liquid cold plate characterized by, The battery liquid cooling plate comprises a buffer pad structure matched with the flow channel structure of the battery liquid cooling plate, and the buffer pad structure is prepared through the following specific steps: (a) high temperature preheating: the battery liquid cold plate as claimed in any one of claims 1-5 is cut into a profiled foam and placed in an oven, the oven temperature t is set in the range of T±5℃, wherein T=T m +(G / 4)℃, and heated for 2-5 minutes; (b) cooling and shaping: the preheated foam is transferred into a mold with the flow channel structure of the liquid cooling plate, shaping pressure is applied through a press, and cooling and shaping are performed to obtain a buffer pad structure matched with the profile of the liquid cooling plate.

14. The battery liquid cold plate of claim 13, wherein, The flow channel structure of the mold is complementary to the concave-convex features on the surface of the battery liquid cooling plate, the forming pressure is 0.5-5 MPa, and the cooling temperature is 10-40 DEG C.

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