2-component low-density polyurethane potting formulation

Abstract

A two-component polyurethane-based potting formulation having excellent flame retardant properties and stabilized foam is provided.

Description

Background Technology

[0001] As electric vehicle (EV) technology advances, there is an increasing demand for vehicles that are lighter and capable of driving longer distances. This ultimately requires manufacturers of individual components to minimize weight. At the same time, for specific applications such as battery potting materials, flame retardancy is also a critical requirement. Automotive EV battery packs typically consist of multiple sections or modules, with each module containing several lithium-ion batteries assembled within a frame. If a cell is damaged, a thermal runaway reaction can occur. For example, heat and pressure can accumulate within a cell due to a short circuit. This heat and pressure can trigger additional exothermic reactions in adjacent cells. If the heat is not dissipated sufficiently quickly, a battery fire may occur. To prevent this, each cell must be surrounded by a thermal barrier, which isolates heat generated from the damaged cell to protect adjacent cells. There is a need in the industry for new and alternative low-density potting materials that offer lightweight properties while meeting applicable flame retardancy standards. means of solving the problem

[0002] The present invention provides a two-component polyurethane-based potting formulation having good flame-retardant properties and a stabilized foam. This formulation is

[0003] a) an isocyanate component containing isocyanate;

[0004] b) As a polyol component,

[0005] i) at least one polyol;

[0006] ii) 1 g / cm 3 A low-density filler having a density of 1% to 20% or less;

[0007] iii) 0.1% to 20% of a rheology modifier;

[0008] iv) at least one crosslinking agent;

[0009] v) 0.5% to 5% of foam stabilizer;

[0010] vi) 0.1% to 5% of a nucleating agent; and

[0011] vii) 0.01% to 2% of foaming agent

[0012] Polyol components including

[0013] Includes

[0014] All of the above percentages are weight percentages based on the total weight of the potting formulation. Specific details for implementing the invention

[0015] The potting formulation generally comprises an isocyanate component and a polyol component, typically in the form of a kit in which each component is kept separate prior to use. The ratio of the two components may vary over a wide range. In some embodiments, the potting formulation comprises 30% to 80% of the polyol component based on the weight of the potting formulation.

[0016] I. isocyanate component

[0017] The isocyanate component of the two-component potting formulation is not limited, and any isocyanate chemical may be used in the present invention. For example, the isocyanate may include any monomeric or polymeric isocyanate commonly used in polyurethane technology. In one embodiment, the isocyanate includes aromatic isocyanates, aliphatic isocyanates, or mixtures thereof. In further embodiments, the isocyanate includes isophorone diisocyanate (IPDI), dicyclohexylmethane diisocyanate (HMDI), hexamethylene diisocyanate (HDI), 4,4-diphenylmethane diisocyanate (MDI) or polymeric variants thereof, 4,4'-methylenediphenyl diisocyanate, or mixtures thereof. In another embodiment, the isocyanate comprises polymeric 4,4-diphenylmethane diisocyanate (MDI), 4,4-diphenylmethane diisocyanate (MDI), tetramethylxylylene diisocyanate (TMXDI), or 4,4'-methylenediphenyl diisocyanate.

[0018] Other suitable isocyanates include 4,4'-methylene-diphenyl diisocyanate; 2,2'-methylene diphenyl diisocyanate; 2,4-methylene diphenyl diisocyanate; toluene diisocyanate (TDI); toluene-2,4-diisocyanate; toluene-2,6-diisocyanate; naphthylene-1,5-diisocyanate; methoxyphenyl-2,4-diisocyanate; diphenyl-methane-4,4'-diisocyanate; diphenylmethane-2,4'-diisocyanate; 4,4'-bi-phenylene diisocyanate; 3,3'-dimethoxy-4,4'-biphenyl diisocyanate; and 3,3'-dimethyl-4-4'-biphenyl diisocyanate. 3,3'-dimethyl-diphenylmethane-4,4'-diisocyanate; 4,4',4"-triphenylmethane triisocyanate; toluene-2,4,6-triisocyanate; 4,4,-dimethyl-di-phenylmethane-2,2,5,5'-tetraisocyanate; and mixtures thereof are included.

[0019] Additionally, any polymer of monomeric isocyanate may be used to prepare an isocyanate prepolymer, which may be used in combination with monomeric isocyanate in some embodiments. Examples include any derivative or polymer of the isocyanate described above. Other examples include polyisocyanates containing urethane, urea, biuret, carbodiimide, uretonimine, alloponate, or other groups formed by the reaction of isocyanate groups. The isocyanate component may also include polymeric MDI (a mixture of MDI and polyMDI, generally referred to as "polymeric MDI"). Other examples include "liquid MDI" products, which are mixtures of MDI and polyMDI derivatives having biuret, carbodiimide, uretonimine, or alloponate linking groups.

[0020] The isocyanate component may comprise an isocyanate prepared by reacting a monomeric or polymeric isocyanate with a polyol, or a diol or triol of lower molecular weight. For example, any one of the polyols listed below may be used for the polyol component; or any of the polyols listed in WO2016205252 (A1) included by reference may be used.

[0021] The potting formulation of the present invention typically contains about 20 to 75%, preferably 25 to 70%, more preferably 30 to 65%, and most preferably 35 to 60% of an isocyanate component based on the total weight of the potting formulation.

[0022] II. Polyol components

[0023] A. polyol

[0024] The polyol suitable for the polyol component may be any polyether polyol having 2 to 7 hydroxyl functionalities. Generally, the polyol component may comprise one or more polyol compounds in an amount of 5 to 50 weight%, preferably 8 to 30 weight%, more preferably 8 to 20 weight%, and most preferably 8 to 15 weight%, based on the weight of the polyol component. The polyol may be any glycerin-initiated propoxylated or ethoxylated polyol, or any propoxylated or ethoxylated polyol prepared from alternative trifunctional and difunctional initiators. In some embodiments, the polyol may be a polyether polyol or a mixture of polyether polyols. In a preferred embodiment, two different polyols are used in the polyol component to balance viscosity and crosslinking density in order to improve the modulus of the potting formulation. In a particularly preferred embodiment, a first polyol having a low functionality of about 250 cps and about 3 is used together with a second polyol having a higher viscosity of about 55 cps and a higher functionality of about 4.3. In other embodiments, the first polyol may be a homopolymer or copolymer of propylene oxide, or a copolymer of propylene oxide having 70 to 99 weight percent propylene oxide and 1 to 30 weight percent ethylene oxide. Where two or more polyether polyols are present, it may be preferable that at least one of the polyols is such a copolymer of propylene oxide and ethylene oxide. In the case of a copolymer, the propylene oxide and ethylene oxide may be randomly copolymerized, block copolymerized, or both. In some embodiments, 50% or more of the hydroxyl groups of the polyether polyol or mixture of polyether polyols are primary hydroxyl groups, and the remaining hydroxyl groups are secondary hydroxyl groups. In other embodiments, 70% or more of the hydroxyl groups of the polyether polyol or mixture thereof may be primary hydroxyl groups.

[0025] In some embodiments, the polyol has a hydroxyl functionality in the range of 2 to 7. In additional embodiments, the polyol has a viscosity of 5,000 cp or less at room temperature (about 25°C), e.g. 4,000 cp or less, 3,000 cp or less, 2,000 cp or less, or 1,500 cp or less.

[0026] B. low-density filler

[0027] To maintain a low-weight potting formulation, the formulation embodiment may contain 1% to 20% of a low-density filler based on the weight of the potting formulation. The low-density filler may be present in either or both of the components, but preferably only in the polyol component. In some embodiments, the low-density filler is 1 g / cm³ 3 It has a density of less than

[0028] In some embodiments, the potting formulation comprises 1% to 20%, preferably 2% to 15%, more preferably 3% to 10%, and most preferably 3.5% or more of a low-density filler based on the weight of the potting formulation. The presence of the low-density filler significantly improves the mechanical properties of the formulation and also makes the foam-based formulation more stable. In a preferred embodiment, surprisingly, it was found that when the amount of the low-density filler in the potting formulation is 3.5% or higher based on the total weight of the potting formulation, the compression modulus of the formulation is significantly improved to more than 300 MPa.

[0029] Various low-density fillers may be used. In some embodiments, the low-density filler comprises hollow microspheres or other syntactic fillers. The hollow microspheres may be hollow glass microspheres, hollow silica microspheres, silica aerogels, hollow phenolic resin microspheres or microballoons, or a combination thereof.

[0030] C. Rheology Modifier

[0031] One advantage of the described potting formulation is that the polyol component is thixotropic. The thixotropic nature of the polyol component allows the low-density filler to be stabilized under storage conditions. Additionally, it is desirable to obtain a formulation that flows easily under mixing or high shear conditions. Such thixotropic properties can be achieved through the use of rheology modifiers.

[0032] In some embodiments, the potting formulation comprises 0.1 to 20%, preferably 0.5 to 15%, more preferably 0.5 to 10%, and most preferably 0.5 to 5% of a rheology modifier based on the weight of the potting formulation. In another embodiment, the potting formulation comprises 0.5 to 2%, preferably 0.5 to 1.5% of a rheology modifier based on the weight of the potting formulation.

[0033] Various rheology modifiers may be used. In some embodiments, the rheology modifier is a urethane resin, such as ethoxylated hydrophobic urethane resin (HEUR), a sulfonate, such as calcium sulfonate, a polyamide, or a modified urea, such as an alkylated or polyether alkyl urea. In a preferred embodiment, the rheology modifier is a modified urea.

[0034] D. Crosslinking agent

[0035] In some embodiments, the polyol component comprises one or more crosslinking agents. The crosslinking agent can advantageously provide a high hard segment content and a high crosslinking density, which can improve the modulus after the potting formulation is fully cured. Any suitable crosslinking agent, for example, any short-chain diol, triol, or quaternary polyol or polyamine, may be used. Non-limiting examples include glycerol, triethanolamine, and pentaerythritol. When the crosslinking agent is present in the polyol component, it may be present in any suitable amount, for example, 0.5% to 20%, e.g., 0.5% to 15%, 0.5% to 10%, 1% to 10%, 2% to 10%, or 5% to 10% based on the weight of the polyol component. In a preferred embodiment, the potting formulation comprises two to three different crosslinking agents in an amount of about 8 to 10% based on the total weight of the potting formulation, in the polyol component.

[0036] In a particularly preferred embodiment, three different crosslinking agents are used in combination to balance the crosslinking density, viscosity, and curing rate for the potting formulation of the present invention. In such an embodiment, triethanolamine is a trifunctional crosslinking agent that has catalytic activity due to its tertiary amine group in the compound structure. Glycerol is also used because it is trifunctional. Additionally, the solid form of pentaerythritol, another crosslinking agent, is also used because it is a tetrafunctional crosslinking agent.

[0037] E. Foam stabilizer

[0038] The polyol component of the present invention also comprises one or more foam stabilizers. While a number of different foam stabilizers may be used, in a preferred embodiment, the foam stabilizer may be one or more of silicone surfactants or non-silicone nonionic surfactants. Such foam stabilizers can improve the stability of the foam and low-density fillers. Typically, the potting formulation comprises one or more foam stabilizers in an amount of 0.5 to 5%, preferably 0.75 to 2.5%, more preferably 0.9 to 1.5%, and most preferably about 1%, based on the total weight of the potting formulation.

[0039] F. nucleus extract

[0040] The polyol component of the potting formulation also comprises one or more nucleating agents. While a number of different nucleating agents may be used, in a preferred embodiment, the nucleating agent may be one or more of talc, silica, alumina trihydrate, zinc oxide, zinc stearate, calcium carbonate, titanium dioxide, graphite, microcrystalline, and nanocellulose. The nucleating agent acts as a site or nucleus for the formation of bubbles that generate foam. By introducing the nucleating agent, the bubble formation process is accelerated, and more uniform bubbles are formed throughout the foam. Typically, the potting formulation comprises one or more nucleating agents in an amount of 0.1 to 5%, preferably 0.1 to 2.5%, more preferably 0.1 to 1.5%, and most preferably 0.1 to 1%, based on the total weight of the potting formulation.

[0041] G. Foaming agent

[0042] The polyol component of the potting formulation also includes a blowing agent. While a number of different blowing agents may be used, in a preferred embodiment, the blowing agent is deionized water. When the blowing agent is included in the potting formulation, it can generate a gas that expands the mixture and creates a foam structure. For example, when water is used as the blowing agent, the water can react with the isocyanate to form CO2, thereby creating a foam-based potting formulation. Hydrocarbons such as pentane and cyclopentane and / or hydrofluoroolefins (HFOs) may also be used as blowing agents in the present invention, as they rapidly vaporize during the foam formation process and contribute to the expansion of the foam. Typically, the potting formulation contains 0.01 to 2%, preferably 0.025 to 1.5%, more preferably 0.05 to 1%, and most preferably 0.05 to 0.5% of the blowing agent based on the total weight of the potting formulation.

[0043] III. Additional optional additives

[0044] A. catalyst

[0045] One of the components may include a catalyst for catalyzing the reaction between an isocyanate reactive group and an isocyanate, such as, for example, a hydroxyl group of a polyol or an amine group of a crosslinking agent. In one embodiment, the catalyst is present in the polyol component.

[0046] The catalyst may comprise, for example, one or more organometallic catalysts that are latent at room temperature (25°C). The organometallic catalysts that are latent at room temperature may contain tin, zinc, bismuth, or a combination thereof. For example, the organometallic catalysts that are latent at room temperature may comprise one or more catalysts such as zinc alkanoate, bismuth alkanoate, dialkyl tin alkanoate, dialkyl tin mercaptide, dialkyl tin bis(alkyl-mercaptoacetate), dialkyl tin thioglycolate, or mixtures thereof. Specific examples include dioctyl tin mercaptide, dibutyl mercaptidem, dibutyl mercaptide, dibutyl mercaptide, bis(dodecylthio)dimethylstannan, dimethyl tin bis(2-ethylhexyl mercaptoacetate), dioctyl carboxylate, dioctyl tin neodecanoate, and mixtures thereof.

[0047] Another catalyst useful for adhesive formulations is any catalyst that can be further heat-activated (referred to as a "thermosensitive catalyst") or otherwise catalyze the reaction. In one embodiment, such catalysts may include, for example, amine-based solid amine catalysts, such as cyclic amidine catalyst compounds, such as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5-diazabicyclo[4.3.0]non-5-ene, 2,4,6-tris-(dimethylaminomethyl)-phenol, and mixtures thereof.

[0048] In additional embodiments, the adhesive formulation may comprise a combination of a latent tin-containing catalyst and a thermosensitive amine-based catalyst. Both the tin-containing organic catalyst and the amine-based catalyst can be readily formulated into an isocyanate component, a polyol component, or both the isocyanate component and the polyol component.

[0049] In additional embodiments, any non-tin metal-organic catalyst exhibiting curing kinetics or a catalytic profile similar to the tin-based catalyst described above may be used as a catalytic component in an adhesive formulation. For example, useful bismuth-based catalysts include bismuth(III)-neodecanoate, and useful zinc-based catalysts include zinc-neodecanoate.

[0050] In another embodiment, non-tin or non-amine catalysts useful for adhesive formulations include carboxylic acid-blocked catalysts, such as DBU carboxylic acid-blocked catalysts. For example, DBU carboxylic acid-blocked catalysts may be TOYOCAT DB41 catalyst (a DBU carboxylic acid salt available from TOSOH), POLYCAT SA-102 / 10 (a DBU carboxylic acid salt available from Air Products), and mixtures thereof. Other useful catalysts include, for example, acid-blocked amine and organic acid catalysts including tertiary amines, such as TOYOCAT DB40, TOYOCAT DB60, and TOYOCAT DB70 available from TOSOH; 1H-1,2,4-triazole amine catalysts, such as TOYOCAT DB30 available from TOSOH; and mixtures thereof. TOYOCAT F22 available from TOSOH; triethylenediamine (TEDA); Any other known thermosensitive amine catalyst, including and mixtures thereof, may also be used. In one embodiment, a useful catalyst is a tin catalyst, such as a di- n - Octyltin bis[isooctylmercaptoacetate]; and amine catalysts, such as POLYCAT SA 1 / 10 and TOYOCAT DB60; and mixtures thereof may be selected.

[0051] In a preferred embodiment, a tertiary amine-based catalyst, such as NIAX-A575 commercially available from Momentive Performance Materials Inc., is used due to its delayed action function. Such a delayed action catalyst is designed to remain inert under normal storage conditions but to become highly active when exposed to heat due to the exothermic reaction of the polyurethane. The use of such a delayed action catalyst allows for longer working times when the viscosity of the potting formulation is low. Additionally, it provides a faster gel time to complete curing / foam rise during the application of the potting formulation.

[0052] Generally, the amount of catalyst in the potting formulation may be in the range of 0.005% to 4.0%; 0.01% to 2.5%; and 0.015% to 2.0% based on the total weight of the formulation.

[0053] If the concentration of the catalyst is less than 0.005% based on the total weight of the potted formulation, the catalyst used may not be effectively active in the formulation, and the storage stability of the resulting formulation may be "poor," meaning that any residual water present in the formulation may deactivate a small amount of the catalyst. If the concentration of the catalyst exceeds 2.0%, the reaction of the components present in the formulation may be too fast, resulting in a short open time, for example, an open time of less than 3 minutes. Additionally, a high level of catalyst in the potted formulation (e.g., exceeding 2.0%) may increase the handling and formulation costs for the resulting formulation.

[0054] B. flame retardant

[0055] Any one or both of the components may contain a flame retardant. Any suitable flame retardant, such as halogenated phosphates, non-halogenated flame retardants, reactive flame retardants, or any combination thereof, may be used. Suitable halogenated phosphates include, for example, chlorinated or brominated organic phosphates. Non-limiting examples include tris(1,3-dichloro-2-propyl)phosphate (TDCPP), tris(1-chloro-2-propyl)phosphate (TCPP), tris(2,3-dichloro-1-propyl)phosphate, and tris(2-chloroethyl)phosphate (TCEP). In a preferred embodiment, the halogenated phosphate is TCPP. Additionally, any suitable halogen-free phosphate may be used in combination with the halogenated organic phosphate.

[0056] Generally, the amount of flame retardant in the potting formulation may be in the range of 5% to 30%; preferably 8% to 25%; more preferably 10% to 23%, and most preferably 15% to 20%, all based on the total weight of the potting formulation.

[0057] IV. Curing method for potting formulations

[0058] The present invention also provides a cured potting formulation prepared by mixing the components of the described potting formulation, applying the mixture onto a desired substrate, such as a battery module, for example, and then curing the mixture. Likewise, the present invention includes a method for curing a potting formulation comprising the steps of mixing an isocyanate component and a polyol component of the potting formulation and curing the mixture. In some embodiments, the isocyanate component and the polyol component are mixed in a ratio ranging from 4:1 to 1:4, preferably 2:1 to 1:2; most preferably about 1:1 (by weight).

[0059] In a specific embodiment, the low-density filler may optionally be dried, for example, at a temperature above 100°C to achieve a desired maximum moisture content. The isocyanate component and the polyol component may each be prepared by mixing for 30 minutes to 1 hour under a maximum pressure, for example, 80 mbar, in an inert atmosphere such as nitrogen. To prepare the final potting formulation, the isocyanate component and the polyol component may be mixed in a desired mass ratio under vacuum for an appropriate amount of time.

[0060] Examples

[0061] The following examples further illustrate the present invention. The scope of the invention and the claims are not limited by the scope of the following examples.

[0062] I. ingredient

[0063] The raw materials listed in Table 1 were used in the examples.

[0064] [Table 1]

[0065]

[0066] Examples of the present invention

[0067] The formulations of the embodiments of the present invention are shown in Table 2 below. The amounts listed are weight percentages of each material.

[0068] [Table 2]

[0069]

[0070] IV. Methods and tests

[0071] Formulation manufacturingFirst, the polyol, crosslinker, and flame retardant were dried on a 3A molecular sieve for 3 days prior to use in the formulation. All liquid components were added to a Max 300 cup (Flackteck Inc.) to prepare Part B of the formulation. The contents were mixed in a Flackteck Speedmixer operating at 2000 rpm for 2 minutes under a vacuum of 50 mBar. Subsequently, the solid contents were added to the cup and mixed at 1200 rpm for 2 minutes without vacuum. Then, the contents were mixed again at 1200 rpm for 2 minutes under a vacuum of 50 mBar. The blended Part B was stored under a nitrogen blanket before mixing with Part A. To prepare the cured potting formulation, Part A and Part B were mixed in a Max 100 cup at the specified ratios provided in Table 2. The contents were mixed in a Flackteck Speedmixer operating at 1200 rpm for 2 minutes under a vacuum of 50 mBar. After mixing, the contents were immediately poured into a mold and cured at room temperature for 3 days.

[0072] rheology Rheological measurements were performed using a Discovery HR1 (TA Instruments) flowmeter with a 25 mm aluminum parallel plate setup. Part B viscosity was measured at 25°C within 120 seconds while increasing the shear flow from 0.01 / s to 100 / s. Viscosities at shear rates of 0.01 and 100 / s are recorded in Table 3 below. For mixed viscosity, the two parts were mixed using a Speedmixer, a small sample was transferred to a 25 mm parallel plate, and viscosity was measured at 25°C at a shear rate of 25 / s. The time to reach a viscosity of 5000 cps was recorded as the working time. Gel time was measured by applying vibrational stress at a frequency of 1 Hz and a strain of 0.12%. The time to reach the G' / G" crossover was recorded as the gel time.

[0073] FlammableFlammability testing was performed using the UL94 standard to assess the flammability safety of plastic materials for components in device and equipment testing. For this test, five specimens measuring 127 mm in length, 13 mm in width, and 3 mm in thickness were prepared. Each specimen was cured for 3 days before the UL94 test was performed. The samples are rated V-0 if: (1) none of the five samples showed flame burn for more than 10 seconds after two 10-second flame applications; (2) the total flame burn time exceeded 50 seconds for 10 10-second flame applications (two applications for each of the five samples); (3) none of the five samples burned to the point of the fixing clamp with flame or luminous burn; (4) none of the five samples dropped flame particles to ignite a dry absorbent surface located 305 mm below the sample; and (5) none of the five samples showed luminous burn lasting more than 30 seconds after the second flame was removed.

[0074] A V1 grade was assigned to the sample if combustion was stopped within 60 seconds after applying a flame to the test bar twice for 10 seconds each.

[0075] compression Compression tests were performed according to ASTM D1621. The material was mixed in a 300 mL-Max speed mixer cup filled to a height of approximately 20 mm. The material was cured in the speed mixer cup into a solid "puck" with a diameter of approximately 150 mm. The top and bottom surfaces of the "puck" were sanded to ensure that the surfaces were parallel to each other. Individual test specimens were obtained from the "puck" using a 1-1 / 8" hole bit.

[0076] The geometric dimensions and mass of each individual specimen were measured and recorded. The specimens were compressed using an INSTRON 5967 equipped with a 30 kN load cell and a parallel compression platen. Tests were performed at a speed 1 / 10 of the measured height of each specimen until a maximum compressive strain of 16% was reached. During each test at an acquisition rate of 2.5 Hz, the transient force [ F ] and bias[ d ] data was recorded. Using the dimensions of the sample recorded prior to the test, compressive engineering stress[ s ] and engineering strain[ e The data was calculated using a formula known in the industry.

[0077] Tensile test : Tensile tests were performed according to ASTM D638 using specimens with dimensions of ISO 8256 Type-3 bar. The material was mixed in a Max Speed ​​Mixer Cup and poured into a rectangular mold to a height of approximately 2.5 to 3 mm. After the material was fully cured, it was trimmed and machined into an ISO 8256 shape using a router fixture.

[0078] Each individual specimen was measured, and its geometric dimensions and mass were recorded. The specimens were tested under tension using an INSTRON 5969 equipped with a 10 kN load cell, mechanical grip, and non-contact extensometer. Tests were performed at a speed of 25 mm / min until fracture. During each test at an acquisition speed of 50 Hz, the transient force [ F ] and local bias[ d ] data was recorded. Using the dimensions of the sample recorded prior to the test, engineering stress[ s ] and engineering strain[ e The data was calculated using a formula known in the industry.

[0079] Lab shear testFor the lap shear test, an e-coated steel coupon measuring 1 inch x 3 inches was used. A liquid potting formulation was applied to an area of ​​12 mm x 25 mm. After applying the liquid potting formulation, a lap shear joint was fabricated using another e-coated steel coupon placed in a 2.5 mm gap. After expansion, the gap between the two coupons was filled with the potting formulation. The potting formulation was cured for 3 days, and the joint was pulled on an INSTRON 5969 at a speed of 1 inch / min.

[0080] density : The density of the cured material was determined using Archimedes' principle at room temperature. The weight of the cured material was measured in air and when immersed in water, and the difference was used to obtain the volume of water displaced (density of water = 1 g / cc). Then, the density was calculated by dividing the mass of the cured sample by its volume.

[0081] Thermal conductivity : ISO 22007-2:2022 Plastics - Determination of Thermal Conductivity and Thermal Diffusivity - Part 2: Thermal conductivity was measured on a ThermTest Hot Disk TPS 2500 S using the transient planar heat source (hot disk) method. A Kapton 4922 sensor (radius of 14.61 mm) was used. The instrument is capable of measuring the thermal diffusivity of a material. Thermal conductivity was calculated by multiplying the thermal diffusivity value obtained from the instrument by independently determined thermal capacity and density. Each sample was measured three times, and the average thermal conductivity value was recorded.

[0082] V. result

[0083] The measured characteristics of the embodiments of the present invention are shown in Table 3.

[0084] [Table 3]

[0085]

[0086] The characteristics of the uncured potting formulation of the embodiment of the present invention are shown in Table 3. The viscosity of the polyol component was measured at various shear rates. The low shear rate viscosity (1 / s) for the potting formulation of the embodiment of the present invention was 8,900 cps, and the high shear rate viscosity (100 / s) was measured at 3,600 cps. From these values, a high degree of thixotropy or "shear thinning" can be observed. The high viscosity at low shear rates is attributed to the formation of a hydrogen bond network of the modified urea-based stabilizer used in the formulation. The high viscosity at low or no shear rates stabilizes the low-density filler during storage. The hydrogen bonds break down at high shear rates, resulting in low viscosity and high fluidity. When mixing the two components, the working time, defined as the time to reach a viscosity of 5,000 cps after mixing, was determined to be 2 minutes in the embodiment of the present invention. The working time allows the liquid formulation to maintain fluidity and self-leveling, enabling the formation of void-free potting. Due to the low mixing viscosity combined with the long working time, this material becomes suitable for pouring into battery packs to fill small gaps between two cells. Additionally, the potting formulation gels approximately 5 minutes after mixing the two parts. The rapid gelation time makes the battery pack suitable for post-processing technology.

[0087] [Table 4]

[0088]

[0089] The characteristics of the cured potting formulation are Table 4As shown in [figure]. The cured potting formulation exhibits high flame retardancy in UL94 testing (V0 grade). In addition, it has a very high thermal resistivity, as indicated by its low thermal conductivity value. Due to its low thermal conductivity along with high flame retardancy, this material is suitable as a thermal barrier to prevent the propagation of thermal runaway reactions in lithium-ion battery packs. Its low density (0.39 g / cc) helps to significantly reduce the weight of the battery pack. Furthermore, its high compressive modulus (410 MPa) and tensile modulus (432 MPa) allow the potting formulation to serve as a structural component of the battery pack and act to mechanically stabilize the battery pack against shock and vibration.

Claims

Claim 1 As a two-component potting formulation, a) an isocyanate component comprising an isocyanate; b) a polyol component, b1) at least one polyol; b2) 1 g / cm 3 A low-density filler having a density of 1% to 20% or less; b3) 0.1% to 20% of rheology modifier; b4) at least one crosslinking agent; b5) 0.5% to 5% of foam stabilizer; b6) 0.1% to 5% of a nucleating agent; and b7) A two-component potting formulation comprising a polyol component comprising 0.01% to 2% of a foaming agent (wherein all percentages are weight percentages based on the total weight of the potting formulation). Claim 2 In claim 1, the polyol component is b8) 0.005% to 4% of catalyst; and b9) A potting formulation further comprising 5% to 30% of a flame retardant (wherein all percentages are weight percentages based on the total weight of the potting formulation). Claim 3 A potting formulation according to claim 1, wherein the low-density filler comprises hollow glass microspheres, hollow silica microspheres, silica aerogel, hollow phenolic resin microspheres or microballoons, or a combination thereof. Claim 4 In claim 1, the foam stabilizer is a potting formulation that is a modified urea-based stabilizer. Claim 5 In paragraph 3, a potting formulation comprising 3.5% or more of the low-density filler based on the total weight of the potting formulation. Claim 6 A potting formulation according to claim 4, comprising 1% or more of the foam stabilizer based on the total weight of the potting formulation. Claim 7 A potting formulation according to any one of claims 1 to 6, wherein the polyol component comprises two different polyols. Claim 8 A potting formulation according to any one of claims 1 to 7, wherein the polyol component comprises three different crosslinking agents. Claim 9 A potting formulation according to any one of claims 1 to 8, wherein the polyol component comprises triethanolamine, glycerol, and pentaerythritol as a combination of crosslinking agents. Claim 10 A potting formulation according to any one of claims 1 to 9, wherein the nucleating agent is one or more selected from talc, silica, alumina trihydrate, zinc oxide, zinc stearate, calcium carbonate, titanium dioxide, graphite, microcrystalline and nanocellulose. Claim 11 In paragraph 2, the catalyst is a tertiary amine-based delayed-action catalyst, a potting formulation. Claim 12 As a two-component potting formulation, a. an isocyanate component comprising an isocyanate; b. a polyol component, i. Polyol; ii. 1 g / cm 3 Low-density filler of 3.5% or more having a density below; iii. 0.5% to 5% of a rheology modifier; iv. At least one crosslinking agent; v. 1% or more of foam stabilizer; vi. 0.1% to 1% of a nucleating agent; and vii. 0.01% to 2% of foaming agent; viii. 0.005% to 4% of catalyst; and ix. A two-component potting formulation comprising a polyol component consisting of 15% to 20% of a flame retardant (wherein all percentages are weight percentages based on the total weight of the potting formulation).

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