Two-component low-density polyurethane potting compound

Abstract

A two-component polyurethane potting compound with excellent flame retardant properties.

Description

Background Art

[0001] As electric vehicle (EV) technology advances, there is an increasing demand for vehicles that are lighter and can travel longer distances. This in turn creates a need for manufacturers of each component to minimize weight. At the same time, for certain applications such as battery potting materials, flame retardancy is also an important requirement. An EV battery pack for a vehicle typically includes a plurality of sections, or modules, each module having several lithium-ion batteries assembled within a frame. If damage occurs to a cell, a thermal runaway reaction can occur. For example, a short circuit can cause heat and pressure to build up within the cell. The heat and pressure can induce further exothermic reactions in adjacent cells. If the heat is not dissipated quickly enough, a battery fire can occur. To prevent this, a thermal barrier is needed to surround each cell, which can isolate the heat generated in a damaged cell so that adjacent cells are protected. There is a need in the art for a new alternative low-density potting material that provides light weight and also meets applicable flame retardancy standards.

Summary of the Invention

Means for Solving the Problems

[0002] This specification describes a two-component potting formulation comprising a) an isocyanate component comprising an isocyanate; and b) a polyol component comprising i) a polyol having a viscosity of 5,000 cp or less at 25°C; ii) a low-density filler having a density of 1 g / cm 3 or less; and iii) a rheology modifier in an amount of 0.1% to 20% by weight of the potting formulation, the two-component potting formulation.

[0003] Typically, uncured potting formulations are in the form of a kit in which the first and second components are not mixed before use.

[0004] The document also describes a process for curing a potting formulation, which generally includes mixing the isocyanate and polyol components of the potting formulation and curing the mixture. [Modes for carrying out the invention]

[0005] Potting formulations generally contain isocyanate and polyol components, typically in the form of a kit where each component is kept separately before use. One or more individual components may be supplied or sold individually; for example, a polyol component may be supplied without an isocyanate component, and vice versa. The ratio of the two components may vary within a wide margin. In some embodiments, the potting formulation contains 50% to 80% polyol component by weight of the potting formulation. In further embodiments, the potting formulation contains 20% to 50% isocyanate component by weight of the potting formulation.

[0006] I. Isocyanate components The isocyanate component of the two-component potting formulation is not limited (any isocyanate component is intended). 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 its polymeric variant, 4,4'-methylenediphenyl diisocyanate, or mixtures thereof. In another embodiment, the isocyanate includes polymeric 4,4-diphenylmethane diisocyanate (MDI), 4,4-diphenylmethane diisocyanate (MDI), tetramethyl xylylene diisocyanate (TMXDI), or 4,4'-methylenediphenyl diisocyanate.

[0007] Other suitable isocyanates include 4,4'-methylene-diphenyl diisocyanate; 2,2'-methylenediphenyl diisocyanate; 2,4-methylene-diphenyl diisocyanate; toluene diisocyanate (TDI); toluene-2,4-diisocyanate; toluene-2,6-diisocyanate; naphthyl-ene-1,5-diisocyanate; methoxyphenyl-2,4-diisocyanate; diphenylmethane-4,4'-diisocyanate; diphenylmethane-2,4'-diiso This includes cyanates; 4,4'-biphenylenediisocyanate; 3,3'-dimethoxy-4,4'-biphenyldiisocyanate; 3,3'-dimethyl-4-4'-biphenyldiisocyanate; 3,3'-dimethyl-diphenylmethane-4,4'-diisocyanate; 4,4',4''-triphenylmethanetriisocyanate; toluene-2,4,6-triisocyanate; 4,4,-dimethyl-diphenylmethane-2,2,,5,5'-tetraisocyanate; and mixtures thereof.

[0008] Any polymer of monomeric isocyanates may also be used to produce isocyanate prepolymers, which in some embodiments may be used in combination with monomeric isocyanates. Examples include any derivatives or polymers of the isocyanates described above. Other examples include polyisocyanates containing urethane, urea, biuret, carbodiimide, uretonimine, alohonate, or other groups formed by the reaction of isocyanate groups. The isocyanate component may also include polymeric MDI (a mixture of MDI and poly-MDI, commonly referred to as "polymeric MDI"). Other examples include "liquid MDI" products, which are mixtures of MDI having biuret, carbodiimide, uretonimine, or alohonate bonds and poly-MDI derivatives.

[0009] The isocyanate component may include isocyanates produced by reacting monomeric or polymeric isocyanates with polyols, or low molecular weight diols or triols. For example, with respect to the polyol component, any one of the polyols described below; or any of the polyols described in International Publication No. 2016205252(A1), incorporated by reference, may be used.

[0010] II. Polyol Components A. Polyol A suitable first polyol for the polyol component can be varied and may be any polyether polyol having a hydroxyl functional value of 2 to 7. Typically, the polyol component may comprise 20 to 80% by weight, for example, 25 to 65% by weight, 25 to 50% by weight, 25 to 40% by weight, or 25 to 30% by weight of the polyol. The polyol may be a propoxylated or ethoxylated polyol initiated with glycerin or any propoxylated or ethoxylated polyol prepared from another trifunctional or bifunctional initiator. In some embodiments, the polyol may be a polyether polyol or a mixture of polyether polyols. 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% by weight of propylene oxide and 1% to 30% by weight of ethylene oxide. When 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, about 50% or more of the hydroxyl groups in the polyether polyol or a mixture of polyether polyols are primary hydroxyls, and the remainder of the hydroxyl groups are secondary hydroxyl groups. In another embodiment, about 70% or more of the hydroxyl groups in the polyether polyol or a mixture thereof may be primary hydroxyl groups.

[0011] In some embodiments, the polyol has a hydroxyl functional value in the range of 2 to 7. In further embodiments, the polyol has a viscosity at room temperature (approximately 25°C) of 5,000 cp or less, for example, 4,000 cp or less, 3,000 cp or less, 2,000 cp or less, or 1,500 cp or less.

[0012] B. Low-density filler To maintain a low weight of the potting material, embodiments of the formulation may include a low-density filler in an amount of 0.1% to 50% of the potting formulation weight. The low-density filler may be present in the first component, the second component, or both. In one embodiment, the low-density filler is present in the polyol component. In further embodiments, the low-density filler is present in the polyol component rather than the isocyanate component. In some embodiments, the low-density filler is 1 g / cm³ 3 It has a density of less than [amount missing].

[0013] In some embodiments, the potting formulation contains 0.1% to 20% of the potting formulation weight of low-density filler, which may be either or both of the components, for example, a polyol component. For example, in one embodiment, the formulation contains 0.1% to 15% of the potting formulation weight of low-density filler, for example, 0.1% to 10%. In further embodiments, the formulation contains 1% to 10% of the potting formulation weight of low-density filler, for example, 1% to 8%, 2% to 6%, 2% to 5%, or 3% to 5%.

[0014] Various low-density fillers can be used. In some embodiments, the low-density filler includes hollow microspheres. The hollow microspheres may be hollow glass microspheres, hollow silica microspheres, silica aerogel, hollow phenolic resin microspheres or microballoons, or a combination thereof.

[0015] C. Rheology Modifier One advantage of the potting formulations described is that the polyol component is thixotropic. The thixotropic properties of the polyol allow the low-density filler to stabilize under storage conditions. It is also desirable to obtain formulations that flow easily under mixing or high-shear conditions. Such thixotropic properties can be achieved through the use of rheological modifiers.

[0016] In some embodiments, the potting formulation contains 0.1 to 20% of the weight of the potting formulation as a rheological modifier. In further embodiments, the potting formulation contains 0.5 to 15% of the weight of the potting formulation as a rheological modifier. In further embodiments, the potting formulation contains 0.5 to 10% of the weight of the potting formulation as a rheological modifier. In further embodiments, the potting formulation contains 0.5 to 5% of the weight of the potting formulation as a rheological modifier. In further embodiments, the potting formulation contains 0.5 to 2% of the weight of the potting formulation as a rheological modifier. In further embodiments, the potting formulation contains 0.5 to 1.5% of the weight of the potting formulation as a rheological modifier.

[0017] A variety of rheological modifiers can be used. In some embodiments, the rheological modifier is a urethane resin, such as an ethoxylated hydrophobic urethane resin (HEUR), a sulfonate, such as a calcium sulfonate, a polyamide, or a modified urea, such as an alkylated or polyetheralkylurea. In one embodiment, the rheological modifier is a modified urea.

[0018] D. Crosslinking agents and other additives In some embodiments, the polyol component includes a crosslinking agent. The crosslinking agent can advantageously provide a high hard segment content and a high crosslink density, which can improve the modulus of elasticity after the potting formulation has fully cured. Any suitable crosslinking agent, e.g., any short-chain diol, triol, or tetrafunctional polyol or polyamine, may be used. Non-limiting examples include glycerol and triethanolamine. If the crosslinking agent is present in the polyol component, it may be present in any suitable amount, e.g., 0.5% to 20% of the weight of the polyol component, e.g., 0.5% to 15%, 0.5% to 10%, 1% to 10%, 2% to 10%, or 5% to 10%.

[0019] In further embodiments, the polyol component may include a moisture scavenger. The potting formulation may contain 0.1 to 10% by weight of the moisture scavenger (e.g., 0.1 to 5%, 0.1 to 3%, or 0.1 to 1.5%) of the potting formulation. A variety of moisture scavengers are preferred. Examples include, among others, molecular sieves, vinylsilanes, oxazolidines, monofunctional isocyanates (e.g., pTSI), and triethyl orthoformate.

[0020] III. Any additional additives A. Catalyst One of the components may contain a catalyst for catalyzing the reaction between the isocyanate and an isocyanate-reactive group, such as 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. In a further embodiment, the catalyst is present in the polyol component but not in the isocyanate component.

[0021] The catalyst may include, for example, one or more latent room temperature (25°C) organometallic catalysts. The latent room temperature organometallic catalyst may contain tin, zinc, bismuth, or a combination thereof. For example, the latent room temperature organometallic catalyst may include one or more catalysts such as zinc alkanoates, bismuth alkanoates, dialkyltin alkanoates, dialkyltin mercaptiates, dialkyltin bis(alkyl mercaptoacetates), dialkyltin thioglycolates, or mixtures thereof. Specific examples include dioctyltin mercaptiates, dibutyl mercaptidems, dibutyl mercaptiates, dibutyl mercaptiates, bis(dodecylthio)dimethyl stannanes, dimethyltin bis(2-ethylhexyl mercaptoacetate), dioctyl carboxylates, dioctyltin neodecanoates, and mixtures thereof.

[0022] Another catalyst useful in the adhesive complex is any catalyst that can be further thermally activated (referred to as a "thermosensitive catalyst") or can catalyze the reaction in another form. In one embodiment, such catalysts can 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.

[0023] In a further embodiment, the adhesive formulation can include 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 easily incorporated into the isocyanate component, the polyol component, or both the isocyanate component and the polyol component.

[0024] In a further embodiment, any non-tin-based metal organic catalyst that exhibits a curing rate or catalyst profile similar to the above tin-based catalyst can be used as a catalyst raw material in the adhesive formulation. For example, useful bismuth-based catalysts include bismuth(III)-neodecanoate, and useful zinc-based catalysts include zinc-neodecanoate.

[0025] In yet another embodiment, non-tin or non-amine catalysts useful in adhesive formulations include carboxylic acid block catalysts such as DBU carboxylic acid block catalysts. For example, DBU carboxylic acid block catalysts may be TOYOCAT DB41 catalyst (a carboxylic acid DBU salt available from Tosoh Corporation), POLYCAT SA-102 / 10 (a carboxylic acid DBU salt available from Air Products), and mixtures thereof. Other useful catalysts include acid block amines, such as tertiary amine and organic acid catalysts such as TOYOCAT DB40, TOYOCAT DB60, and TOYOCAT DB70 available from Tosoh Corporation, 1H-1,2,4-triazole amine catalysts such as TOYOCAT DB30 available from Tosoh Corporation, and mixtures thereof. Any other known thermosensitive amine catalysts, such as TOYOCAT F22, triethylenediamine (TEDA), and mixtures thereof available from Tosoh Corporation, may also be used. In one embodiment, useful catalysts may be selected from tin catalysts such as di-n-octyl tinbis[isooctyl mercaptoacetate], amine catalysts such as POLYCAT SA1 / 10 and TOYOCAT DB60, and mixtures thereof.

[0026] Typically, the amount of catalyst in an adhesive formulation may range from 0.005% to 2.0% by weight, 0.01% to 1.0% by weight, and 0.015% to 0.07% by weight, based on either i) the total weight of the formulation or ii) the total weight of the first or second component of the formulation (i.e., the polyol component or the isocyanate component). In one exemplary embodiment, for example, when a tin catalyst such as di-n-octyl tinbis[isooctyl mercaptoacetate] is used in the adhesive formulation, the concentration of such catalyst in the formulation or any of its components may range from 0.005% to 1.0% by weight, 0.02% to 0.08% by weight, and 0.03% to 0.05% by weight, based on the total weight of the entire formulation or any of its components.

[0027] In another exemplary embodiment, when a thermosensitive amine catalyst such as POLYCAT SA1 / 10 is used in an adhesive formulation, the concentration of such a catalyst in the formulation may be 0.01% to 2.0% by weight; 0.01% to 1.0% by weight; and 0.015% to 0.025% by weight, based on the weight of the formulation, either as a whole or as one of its components.

[0028] In yet another exemplary embodiment, when a catalyst such as TOYOCAT DB60 is used in an adhesive formulation, the concentration of such catalyst in the formulation may be 0.01% to 2.0% by weight; 0.01% to 1.0% by weight; and 0.045% to 0.065% by weight, based on the weight of the formulation, either as a whole or as one of its components.

[0029] If the catalyst concentration is less than 0.005% by weight of the total composition, the catalyst used may not be effectively active in the composition, and the storage stability of the resulting composition may be "insufficient," meaning that any residual water present in the composition may deactivate small amounts of catalyst. If the catalyst concentration exceeds approximately 2.0% by weight, the reaction of the components in the composition may be too rapid, resulting in a short open time, for example, less than 3 minutes. Furthermore, a high catalyst level in the composition (e.g., more than 2.0% by weight) may lead to increased handling difficulty and formulation costs for the resulting composition.

[0030] B. Flame retardants Either or both components may contain a flame retardant. In some embodiments, the polyol component contains a flame retardant. Any suitable flame retardant may be used, such as halogenated phosphates, non-halogenated flame retardants, reactive flame retardants, or any combination thereof. Suitable halogenated phosphates include, for example, chlorinated or brominated organophosphates. 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 one embodiment, the first halogenated phosphate is TCPP. Any suitable halogen-free phosphate may be used in combination with a halogenated organophosphate.

[0031] C. Plasticizers Any component, and in some embodiments, the polyol component, may contain a plasticizer. In one embodiment, the plasticizer may have a weight-average molecular weight of 2,000 g / mol or less, for example, 1,000 g / mol or less, 800 g / mol or less, or 600 g / mol or less. The plasticizer is usually liquid at a temperature of about 100°C. The plasticizer may be present in any suitable amount, for example, by the weight of any component, or alternatively, 1 to 20% of the weight of the formulation.

[0032] Suitable plasticizers include any ester-based plasticizer, such as adipates, azelates, citrates, benzoates, butyrates, orthophthalates, terephthalates, sebacates, and trimellitates. Examples include ester derivatives of acids and anhydrides such as adipic acid, azelaic acid, benzoic acid, citric acid, dimeric acids, fumaric acid, isobutyric acid, isophthalic acid, lauric acid, linoleic acid, maleic acid, maleic anhydride, melissic acid, myristic acid, oleic acid, palmitic acid, phosphoric acid, phthalic acid, ricinoleic acid, sebatic acid, stearic acid, succinic acid, 1,2-benzenedicarboxylic acid, and mixtures thereof. Epoxylated oils, glycerol derivatives, paraffin derivatives, sulfonic acid derivatives, and mixtures thereof are also suitable.

[0033] Specific examples of such plasticizers include diethylhexyl adipate, heptyl nonyl adipate, diisodecyl adipate, adipic acid polyester, dicaprylyl adipate, dimethyl azelate, diethylene glycol dibenzoate and dipropylene glycol dibenzoate, polyethylene glycol dibenzoate, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate benzoate, 2,2,4-trimethyl-1,3-pentanediol diisobutyrate, and methyl (or ethyl or butyl) phthalyl ethyl Glycolate, triethyl citrate, dibutyl fumarate, 2,2,4-trimethyl-1,3-pentanediol diisobutyrate, methyl laurate, methyl linoleate, di-n-butyl maleate, tricapryl trimellitate, heptyl nonyl trimellitate, triisodecyl trimellitate, triisononyl trimellitate, isopropyl myristate, butyloleate, methyl palmitate, tricresyl phosphate, tris(2-ethylhexyl) phosphate, dimethyl phthalate, diethyl phthalate, dibutyl Tyl phthalate, diisobutyl phthalate, di-2-ethylhexyl phthalate, octyldecyl phthalate, diisodecyl phthalate, heptylnonyl phthalate, diundecyl phthalate, ditridecyl phthalate, dicyclohexyl phthalate, diphenyl phthalate, butyl benzyl phthalate such as n-butyl benzyl ester of o-phthalic acid, isodecyl benzyl phthalate, alkyl (C7 / C9) benzyl phthalate, dimethoxyethyl phthalate, 7-(2,6,6,8-tetramethyl-4-oxa-3-oxo-nonyl This includes benzyl phthalate, di-2-ethylhexyl sebacate, butyl ricinoleate, dimethyl sebacate, methyl stearate, diethyl succinate, butylphenyl methyl ester of 1,2-benzenedicarboxylic acid, epoxidized linseed oil, glycerol triacetate, chloroparaffin having about 40% to about 70% Cl, o,p-toluenesulfonamide, N-ethyl p-toluenesulfonamide, N-cyclohexyl p-toluenesulfonamide, sulfonamide-formaldehyde resin, and mixtures thereof.

[0034] Other suitable plasticizers known to those skilled in the art include, alone or in mixtures with other plasticizers, castor oil, aromatic petroleum condensates, partially hydrogenated terphenyls, silicone plasticizers such as dimethicone copolyol esters, dimethiconol esters, silicone carboxylates, and garbet esters.

[0035] IV. Process for curing the potting compound Also disclosed are cured potting formulations prepared by mixing the components of the potting formulation described and curing the mixture after application to a desired substrate, such as a battery module. Similarly, the disclosure includes processes for curing potting formulations, comprising mixing the isocyanate and polyol components of the potting formulation and curing the mixture. In some embodiments, the first and second components of the potting formulation are mixed in a ratio ranging from 4:1 to 1:4, for example, 2:1 to 1:2 (by weight). In further embodiments, the first and second components of the potting formulation are mixed in a ratio of 1:1.

[0036] In one particular embodiment, the lightweight filler may be optionally dried, for example, at over 100°C, e.g., 110°C, to achieve the desired maximum moisture content. The isocyanate component and the polyol component may be prepared by mixing them under maximum pressure, e.g., 80 mbar, in an inert atmosphere such as nitrogen, for 30 minutes to 1 hour, respectively. To pot the two components, the first and second components may be mixed under vacuum in the desired mass ratio for an appropriate amount of time. For the test method, the density of each component may be measured using a density cup. The performance of the flame retardant can be evaluated according to the UL94 standard. [Examples]

[0037] The following embodiments further illustrate this disclosure. The scope of this disclosure and the claims is not limited by the scope of the following embodiments.

[0038] I. Material The raw materials listed in Table 1 were used in the examples.

[0039] [Table 1]

[0040] Table 2 lists the intended substitutes for the specific materials listed in Table 1.

[0041] [Table 2]

[0042] II. Embodiments and Comparative Examples The compositions of the embodiment and comparative example of the invention are shown in Table 3 below. The listed quantities are weight percentages of each material.

[0043] [Table 3]

[0044] III. Methods and Tests The polyol and ANTIFLAME TCPP were first dried under a 3A molecular sieve for 3 days before use in the formulation. Part B of the formulation (polyol blend) was prepared by adding all liquid components in a Max300 cup (Flackteck Inc.). The contents were mixed in a Flackteck Speedmixer operating at 2000 rpm for 2 minutes under a vacuum of 50 mBar. The solid contents were then added to the cup and mixed at 1200 rpm for 2 minutes without vacuum. The contents were then 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 being mixed with Part A. In Example 2, Expanseil 920 DE 40 d30 was first blended with TCPP to form a slurry, which was then added to the final blend.

[0045] To prepare the cured potting compound, parts A and B were mixed in Max 100 cups in the given ratios shown in Table 2. The contents were mixed in a Flackteck Speedmixer operating at 1200 rpm for 2 minutes under a vacuum of 50 mBar. Immediately after mixing, the contents were poured into a mold and cured at room temperature for 3 days.

[0046] Rheology: Rheological measurements were performed using a Discovery HR1 (TA Instruments) rheometer with a 25mm aluminum parallel plate setup. The viscosity of Part B was measured at 25°C with shear flow gradients from 0.01 / s to 100 / s over 120 seconds. Viscosities at shear rates of 0.01 and 100 / s are reported in Table 4. For mixed viscosity, the two parts were mixed using a Speedmixer, a small sample was transferred to a 25mm parallel plate, and the viscosity was measured at 25°C with a shear rate of 25 / s. To determine the pot life, viscosity measurements were continued until the viscosity reached 5000 cps.

[0047] Flammability: Flammability tests were conducted using the UL94 standard to assess the flammability safety of plastic materials for components in device and electrical appliance testing. Five samples measuring 127 mm in length, 13 mm in width, and 3 mm in thickness were prepared for this test. Each sample was cured for 3 days before the UL94 test was performed. A V0 rating was given to a sample if: (1) none of the five samples had flame burning for more than 10 seconds after each of two 10-second flame applications; (2) the total flame burning time exceeded 50 seconds in 10 10-second flame applications (two applications for each of the five samples); (3) none of the five samples burned to the holding clamp with flame or incandescent combustion; (4) none of the five samples dropped flame particles that ignited the dry absorbent cotton placed 305 mm below the sample; (5) none of the five samples had incandescent combustion that lasted for more than 30 seconds after the second flame removal.

[0048] After applying a flame to each test bar for 10 seconds twice, a sample was given a V1 rating if combustion stopped within 60 seconds.

[0049] Compression: Compression tests were performed according to ASTM D1621. The material was mixed in a 300 mL Max speed mixer cup and filled to a height of approximately 20 mm. The material was allowed to harden in the speed mixer cup into a solid "pack" with a diameter of approximately 150 mm. The top and bottom surfaces of the "pack" were polished to ensure that the surfaces were parallel to each other. Individual samples were extracted from the "pack" using a 1-1 / 8" hole bit.

[0050] Each individual sample was measured and both its geometric dimensions and mass were recorded. The samples were compressed using an INSTRON5967 equipped with a 30kN load cell and a parallel compression platen. The tests were performed at a speed of 1 / 10th the measurement height of each sample until a maximum compressive strain of 16% was reached. Transient force [F] and displacement [d] data were recorded during each test at an acquisition rate of 2.5 Hz. Using the sample dimensions recorded before the test, compressive engineering stress [s] and engineering strain [e] data were calculated using equations known in the art.

[0051] Tensile Test: Tensile tests were performed according to ASTM D638 using samples with bar dimensions conforming to ISO 8256 Type 3. The material was mixed in a Max Speed ​​Mixer cup and poured into a rectangular mold to a height of approximately 2.5–3 mm. After the material had fully cured, it was trimmed using a router fixture and machined into the ISO 8256 shape.

[0052] Each individual sample was measured and both its geometric dimensions and mass were recorded. Samples were tested under tension using an INSTRON5969 equipped with a 10kN load cell, mechanical grip, and non-contact extensometer. The tests were performed at a rate of 25 mm / min until failure. Transient force [F] and local displacement [d] data were recorded during each test at an acquisition rate of 50 Hz. Using the sample dimensions recorded before testing, engineering stress [s] and engineering strain [e] data were calculated using equations known in the art.

[0053] Density: The density of the hardened material was determined at room temperature using Archimedes' principle. The weight of the hardened material was measured in air and when submerged in water, and the difference was used to obtain the volume of water removed (density of water = 1 g / cc). The density was then calculated by dividing the mass of the hardened sample by its volume.

[0054] Thermal conductivity: Thermal conductivity was measured using a ThermTest Hot Disk TPS 2500 S with the ISO 22007-2:2022 Plastics (Determination of thermal conductivity and thermal diffusivity) Part 2: Transient plane heat source (hot disc) method. A Kapton 4922 sensor (14.61 mm radius) was used. The instrument can measure the thermal diffusivity of the material. Thermal conductivity was calculated by multiplying the thermal diffusivity value obtained from the instrument by the independently determined heat capacity and density. Each sample was measured in triplicate, and the average thermal conductivity value was reported.

[0055] IV. Results The measured characteristics of the embodiments and comparative examples of the invention are shown in Table 4.

[0056] [Table 4]

[0057] The viscosity of Part B (polyol blend) was measured over various shear rates. For the potting compound of Invention Example 1, the viscosity (1 / s) at a low shear rate was 4,280 cps, and the viscosity (100 / s) at a high shear rate was 850 cps. Similarly, for the potting compound of Invention Example 2, the viscosity (1 / s) at a low shear rate was 6,500 cps, and the viscosity (100 / s) at a high shear rate was 1,100 cps. In both cases, a high degree of thixotropy or "shear thinning" was observed. The high viscosity at low shear rates is attributed to the formation of a hydrogen bonding network of the modified urea-based stabilizer used in the formulation. High viscosity at low shear or without shear allows the low-density filler to stabilize during storage. The hydrogen bonds decompose at high shear rates, resulting in low viscosity and high fluidity. When the two parts A and B were mixed, the resulting initial viscosities were measured at 1,040 cps and 1,100 cps for Invention Examples 1 and 2, respectively. The pot life, defined as the time it takes to reach a viscosity of 5,000 cps after mixing, was determined to be 11 minutes and 12 minutes for Invention Examples 1 and 2, respectively. The low mixed viscosity combined with the long pot life makes this material suitable for pouring into battery packs and filling small gaps between two cells.

[0058] Both potting compounds of the present invention exhibit high flame resistance in UL94 testing (V0 rating). Furthermore, both possess extremely high thermal resistivity, as indicated by their low thermal conductivity values. The combination of high flame resistance and low thermal conductivity makes these materials suitable as thermal barriers to prevent the propagation of runaway thermal reactions in lithium-ion battery packs.

[0059] By adding a low-density filler, the composition of the present invention can have a lower density compared to the comparative example which has a significantly higher density (1.2 g / cc).

[0060] During each test, the modulus of elasticity was calculated in two separate ranges within the stress-strain curve: 1) the initial slope (the linear portion within the first 1% of strain), and 2) the secondary slope (the linear portion within approximately 10% to 15% of strain). Compressive strength was also recorded at separate compressive strain values ​​of 5%, 10%, and 15%. A summary of the compression results can be seen in Table 5.

[0061] [Table 5]

[0062] [Table 6]

[0063] During each test, the modulus of elasticity was calculated within the initial linear portion of the stress-strain curve from a strain of approximately 0.5–1.0%. Maximum tensile strength and elongation at fracture were also recorded for each test. A summary of the compression results can be seen in Table 6.

[0064] [Table 7]

[0065] [Table 8]

[0066] The features and advantages of this disclosure are evident from the detailed specification, and the claims encompass all such features and advantages. Many variations will be conceivable to those skilled in the art, and any variations equivalent to those described herein are included within the scope of this disclosure. Those skilled in the art will understand that the underlying concepts of this disclosure can be used as a basis for designing other compositions and methods to accomplish some of the objectives of this disclosure. Consequently, the claims should not be considered limited by this specification or the examples.

Claims

1. A two-component potting compound, a) Isocyanate components containing isocyanates; b) Polyol components, i) Polyols having a viscosity of 5,000 cp or less at 25°C; ii) 1 g / cm 3 Low-density fillers having the following densities: iii) A polyol component comprising 0.1% to 20% of the weight of the potting formulation as a rheological modifier; A two-component potting formulation comprising, wherein the uncured potting formulation is in the form of a kit in which the first and second components are not mixed before use.

2. The potting compound according to claim 1, wherein the polyol is a polyether polyol having a hydroxyl functional value in the range of 2 to 7.

3. The potting compound 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.

4. The potting formulation according to claim 1, comprising 0.1% to 50% of the weight of the potting formulation of the low-density filler.

5. The potting formulation according to claim 1, comprising 0.1% to 20% of the weight of the potting formulation of the low-density filler.

6. The potting formulation according to claim 1, comprising 0.1% to 15% of the weight of the potting formulation of the low-density filler.

7. The potting formulation according to claim 1, comprising 0.1% to 10% of the weight of the potting formulation of the low-density filler.

8. The potting formulation according to claim 1, comprising 1% to 10% of the weight of the potting formulation of the low-density filler.

9. The potting formulation according to claim 1, comprising 1% to 8% of the weight of the potting formulation of the low-density filler.

10. The potting formulation according to claim 1, comprising 2% to 6% of the weight of the potting formulation of the low-density filler.

11. The potting formulation according to claim 1, comprising 2% to 5% of the weight of the potting formulation of the low-density filler.

12. The potting formulation according to claim 1, comprising 3% to 5% of the weight of the potting formulation of the low-density filler.

13. The potting formulation according to claim 1, comprising 0.5% to 15% of the weight of the potting formulation in the rheological modifier.

14. The potting formulation according to claim 1, comprising 0.5% to 10% of the weight of the potting formulation in the rheological modifier.

15. The potting formulation according to claim 1, comprising 0.5% to 5% of the weight of the potting formulation in the rheological modifier.

16. The potting formulation according to claim 1, comprising 0.5% to 2% of the weight of the potting formulation in the rheological modifier.

17. The potting formulation according to claim 1, comprising 0.5% to 1.5% of the weight of the potting formulation of the rheological modifier.

18. The potting compound according to claim 1, wherein the rheological modifier is a urethane resin, a sulfonate, a polyamide, or a modified urea.

19. The potting formulation according to claim 1, wherein the polyol component further comprises a crosslinking agent having at least two hydroxyl or amino functional groups that are reactive with the isocyanate.

20. The potting compound according to claim 1, wherein the polyol component further comprises a moisture-scavenging agent.

21. The potting compound according to claim 1, further comprising a catalyst capable of catalyzing the reaction between the isocyanate and the isocyanate-reactive group.

22. The potting compound according to claim 1, further comprising a plasticizer.

23. A method for curing a potting compound according to claim 1, comprising mixing the isocyanate component and the polyol component of the potting compound and curing the mixture.

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