Two-part potting composition

Abstract

A two-part potting composition A two-part potting composition comprising: an A part comprising: a first polyol fraction, a reactive diluent comprising an aromatic alcohol, and water; and a B part comprising a polyisocyanate.

Description

[0001] Two-Part Potting Composition

[0002] The invention relates to a two-part potting composition, a method of potting electric vehicle (EV) cells, an electric vehicle (EV) battery, an electric vehicle and the use of the two-part potting composition.

[0003] Battery systems - such as those used in electric vehicles, energy storage modules, and portable electronics - require secure housing and protection from mechanical shock, vibration, and environmental ingress. Potting materials are widely used to encapsulate such components, helping to maintain electrical insulation and structural integrity.

[0004] Conventional potting compounds, such as epoxies and silicones, can be dense and rigid, resulting in increased system weight and poor energy absorption. Since the weight of the battery is a significant portion of the total weight of an electric vehicle, the higher the weight the lower the overall mileage and performance of the vehicle. While foamed potting systems offer improvements in weight and compliance, existing materials often suffer from poor cure control, inconsistent foam morphology, or inadequate thermal or mechanical performance.

[0005] Two-part potting systems, in which reactive components are kept separate until use, offer advantages in terms of stability, on-demand foaming, and processing flexibility. However, known two-part systems may lack optimal properties when foamed in situ around battery cells, particularly in terms of uniformity, resilience, and thermal performance.

[0006] The present invention seeks to tackle at least some of the problems associated with the prior art or at least to provide a commercially acceptable alternative solution thereto.In a first aspect, the present invention provides a two-part potting composition comprising: an A part comprising: a first polyol fraction, a reactive diluent comprising an aromatic alcohol, and water; and a B part comprising a polyisocyanate.

[0007] Each aspect or embodiment as defined herein may be combined with any other aspect(s) or embodiment(s) unless clearly indicated to the contrary. In particular, any features indicated as being preferred or advantageous may be combined with any other feature indicated as being preferred or advantageous.

[0008] The inventors have surprisingly found that the two-part potting composition is capable of forming a foam suitable for potting an electrical device, such as a battery. Once cured, the composition may exhibit a low flammability and / or a high flame retardance, for example a flammability grade LIL94 VO. Such features may be provided without the need to employ the use of phosphate-based or halogen-based flame retardants. Advantageously, the composition, once cured, may exhibit a high level of flexibility, which may serve to increase the vibration resistance of a battery potted with the composition. The composition, once cured, may be dimensionally stable, lightweight, and compliant, and may provide effective potting of battery cells with improved impact absorption, thermal conductivity (such as less than 0.2 W / m.K), and dielectric properties. The invention thus enables an efficient and scalable in situ potting process, suitable for modern battery pack manufacturing.

[0009] The composition, once cured, may enable effective thermal management of a battery cell, ensuring efficient operation of the cell during normal operation, whilst providing improved safety in the event of malfunction to prevent thermal propagation. Effective thermal management enhances battery lifetime ensuring that cells operate within the recommended temperature range, prolonging battery life. High temperatures accelerate the degradation of Li-ion cells. The composition may also replace regular silicone potting resin for weight reduction in IP65 / 66 / 67 enclosures to provide an airtight environment. The excellent thermal insulation properties may help maintain the interior temperature to prevent air condensing.Conventional potting compositions typically aim to undergo fast foaming and curing, for example to speed up battery production methods employing the potting compositions. The potting composition of the present invention may foam and cure more slowly. It has been surprisingly found that such slower foaming and curing may result in fewer empty spaces / voids when forming the potting composition around battery cells (when used as a battery potting composition) or when using the composition as a conformal coating on a PCB. (Such empty spaces I voids being different to the voids defining the foam structure.)

[0010] The composition, once cured, may advantageously exhibit a foam structure that is stable, microcellular and / or soft.

[0011] The term “potting composition” as used herein may encompass a material used to encapsulate electrical components, such a battery cells.

[0012] The composition comprises an A part and a B part. The A part and B part are typically physically isolated from each other prior to use, for example being stored in separate containers.

[0013] The A part comprises a first polyol fraction. The first polyol fraction may comprise only one type of polyol but typically comprises multiple types of polyols.

[0014] In order to pot (encapsulate) an electrical component, the A part and the B part are contacted with each other and the resulting mixture is disposed on and around the electrical component. The polyols of the first polyol fraction may react with the polyisocyanate to form a polyurethane.

[0015] The water may react with isocyanate groups of the polyisocyanate to form bubbles of carbon dioxide. In other words, the water may function as a blowing agent.

[0016] Advantageously, such bubbles may impart a foam structure to the polyurethane. The presence of bubbles, in particular bubbles filled with carbon dioxide, may reduce thermal propagation when a battery cell catches fire and / or inhibit the spread of thefire. In addition, such “foaming” may help to spread the composition around the electrical components during potting. Since water contains hydroxyl groups, it may enter the polyurethane as a chain polymer. Accordingly, the composition may be devoid of blowing agents that become impurities dispersed within the polyurethane. Any amine and / or urea formed when the water reacts with the isocyanate groups may also be part of the polyurethane. The water is consumed during the reaction, and may result in a 100% solids, minimal VOC final product.

[0017] The composition comprises a reactive diluent. This may result in the composition exhibiting a low viscosity such as, for example, less than 2000 cps. Such a reduced viscosity may enable the formation of a foam. This may avoid the need to employ large amounts of blowing agents, which may contaminate the final polyurethane. Such a reduced viscosity may enable the composition to be more easily dispersed around an electrical component to be potted.

[0018] The composition is preferably substantially free of (less than 1 wt.% based on the total weight of the composition, preferably less than 0.1 wt.%, even more preferably less than 0.01 wt.%), more preferably free of, non-reactive diluents and / or phosphate-based flame retardant plasticizers since these may adversely affect one or more of the electrical resistivity, tensile strength, moisture resistivity, hydrolysis resistivity an dimensional stability of the cured foam.

[0019] The potting composition may be a flame-retardant potting composition. The potting composition may be a battery potting composition, for example an EV battery potting composition.

[0020] The reactive diluent comprises aromatic alcohol. The reactive diluent may consist of aromatic alcohol. The hydroxyl groups of the aromatic alcohol may act as chain terminators during the formation of the polyurethane, i.e. the diluent may be a reactive diluent. The aromatic groups may increase the flame retardant properties of the foam. Accordingly, it may be possible to achieve a desired level of flame retardance without the need to employ phosphate-based or halogen-based flameretardants, which may not be environmentally friendly and / or may not exhibit a suitable level of moisture resistance.

[0021] The aromatic alcohol preferably comprises or consists of a phenolic lipid. Phenolic lipids may be particularly suitable as aromatic diluents. The hydrophobic nature of phenolic lipids may increase the hydrophobicity of the polyurethane foam, which may therefore increase the moisture resistance. The long lipid chain may increase the flexibility of the polyurethane foam, thereby increasing the vibration resistance.

[0022] Preferably, the aromatic alcohol and / or phenolic lipid has a hydroxyl functionality of 1 and / or comprises a single hydroxyl group. This may increase the pot life of the composition.

[0023] Preferably, the aromatic alcohol and / or phenolic lipid comprises a carbon chain having from 10 to 20 carbon atoms, more preferably from 13 to 17, even more preferably from 14 to 16, still even more preferably 15. This may increase the flexibility of the polyurethane foam due to internal plasticisation, thereby increasing the vibration resistance. This may also improve the hydrophobicity.

[0024] Preferably, the aromatic alcohol and / or phenolic lipid comprises an unsaturated carbon chain. This may enable the use of lower amounts of blowing agent. In addition, this may result in more three-dimensional cross-linking, which may lead to a more stable foam while using a low functionality polyol.

[0025] Preferably, the aromatic alcohol and / or phenolic lipid comprises or consists of cardanol and / or is cashew nut shell-derived (CNSL-derived). Such species may be particularly suitable imparting the desirable viscosity, flame retardance, flexibility, and / or pot life. A commercial example of such an aromatic alcohol is Ultra LITE2020.

[0026] The two-part potting composition is preferably for potting a battery, more preferably an electric vehicle (EV) battery. Batteries, in particular EV batteries, may be prone to catching fire and are vulnerable to vibrations.The first polyol fraction preferably has a number average molecular weight (Mn) of from 500 to 2500, more preferably from 1800 to 2200. Alternatively, the first polyol fraction preferably has a number average molecular weight (Mn) of from 1000 to 3000, more preferably from 1500 to 2100, even more preferably from 1700 to 1900, still even more preferably about 1800. Alternatively, the first polyol fraction preferably has a number average molecular weight (Mn) of from 500 to 3500, more preferably from 1000 to 3000, even more preferably from 1500 to 2100, still even more preferably from 1700 to 1900, still even more preferably about 1800. Such molecular weights may result in favourable flexibility, softness, vibration resistance and / or crack resistance.

[0027] The first polyol fraction preferably has a weighted average hydroxyl functionality of from 2 to 3, more preferably from 2.5 to 2.9, more preferably from 2.6 to 2.8.

[0028] Alternatively, the first polyol fraction preferably has a weighted average hydroxyl functionality of from 2.3 to 2.8, more preferably from, 2.4 to 2.7. Such hydroxyl functionalities may result in a polyurethane foam having a desirable flexibility. Higher hydroxyl functionalities may increase the amount of cross-linking in the polyurethane, thereby reducing the flexibility. For example, the foam may have a higher degree of flexibility compared to a polyurethane foam formed using castor oil, which contains polyols with a hydroxyl functionality of about 3. The term “hydroxyl functionality” refer to the number of hydroxyl groups per molecule. The hydroxyl number may be determined using the following formula:

[0029] Hydroxyl number = hydroxyl value 156100) * molecular weight

[0030] The molecular weight may be determined, for example, by gel permeation chromatography.

[0031] The first polyol fraction preferably has a hydroxyl value (weighted average hydroxyl value) of from 70 to 90 mgKOH / g, more preferably from 75 to 85 mgKOH / g. Thehydroxyl value may be measured using, for example, ASTM D4274-23. Such hydroxyl values may provide a desirable level of flexibility to the polyurethane foam.

[0032] The first polyol fraction preferably comprises a copolymer comprising triglyceride structural units and fatty acid diester structural units. Preferably, the triglyceride comprises ricinolein and / or the fatty acid of the fatty acid ester comprises ricinoleic acid. Such species may result in a polyurethane foam with particularly desirable flexibility and flame retardance. A commercial example of a polyol fraction containing such a copolymer is Jagropol-80NR from Jayant Agro-Organics Limited. The term “ricinolein” as used herein may encompass a compound having the following structural formula:

[0033]

[0034] The term “ricinoleic acid” as used herein may encompass a compound having the following structural formula:

[0035]

[0036] The first polyol fraction is preferably derived from castor oil, more preferably castor oil that has undergone hydrogenolysis. The first polyol fraction preferably comprises a castor oil copolymer.The first polyol fraction preferably comprises 2-[(Z,12R)-12-hydroxyoctadec-9-enoyl]oxyethyl (Z,12R)-12-hydroxyoctadec-9-enoate, i.e.

[0037]

[0038] Such a species preferably makes up 75 wt.% or more of the first polyol fraction, more preferably 80 wt.% or more of the polyol fraction, even more preferably from 80 to 90 wt.% of the first polyol fraction.

[0039] The A part preferably further comprises a second polyol fraction. The second polyol fraction preferably comprises or consists of a linear polyester polyol. The linear polyester polyol preferably comprises polycaprolactone polyol, more preferably a difunctional polycaprolactone polyol. A commercial example of a suitable polycaprolactone polyol is CAPA 2043. In use, the second polyol fraction reacts with the polyisocyanate. In other words, polyols of the second polyol fraction are included as structural units in the polyurethane foam. This may impart to the polyurethane foam a high resistance to species such as water, oil, solvents and halogens. The second polyol fraction may act as a chain extender and may facilitate linear chain growth during the gelling reaction.

[0040] The second polyol fraction preferably has a number average molecular weight of from 300 to 1000, preferably from 350 to 450. This may impart the composition with an initial workable low viscosity.

[0041] The molar ratio of X : Y in the two-part potting composition is preferably from 1.5:1 to 3:1, preferably from 1.8:1 to 2.2:1 , wherein X corresponds to the moles of polyisocyanate and Y corresponds to the total moles of the polyols of the first polyol, the reactive diluent, the water and, if present, the polyols of the second polyol. Such ratios may result in the formation of a polyurethane foam having a particularly favourable combination of high flexibility and high flame retardance. In addition, the composition may be more easily mixed in a static mixer prior to application.Furthermore, such ratios help maintain the overall dimensional stability of the cured foam product in between the cells.

[0042] The molecular ratio of the first polyol fraction to the polyiosocyanate is preferably from 4:1 to 6:, more preferably from 4.5:1 to 5.5:1, even more preferably from 5:1 to 5.4:1. The molar ratio of the second polyol fraction to the polyisocyanate is preferably from 1:1 to 2:1, more preferably from 1.2:1 to 1.8:1, even more preferably from 1 :3:1 to 1.7:1. The molar ratio of the reactive diluent to the polyisocyanate is preferably from 2:1 to 3:1, more preferably from 2.2:1 to 2.8:1, even more preferably from 2.3:1 to 2.7:1. The molar ratio of the water to the polyisocyanate is preferably from 10:1 to 20:1, more preferably from 12:1 to 18:1, even more preferably from 13:1 to 17:1. Such ratios may result in the formation of a polyurethane foam having a particularly favourable combination of high flexibility and high flame retardance, and may help maintain the overall dimensional stability of the cured foam product in between the cells.

[0043] The molar ratio of X : Y in the two-part potting composition is preferably from 4:1 to 8:1 , preferably from 5:1 to 6:1 , wherein X corresponds to the moles of isocyanate functional groups and Y corresponds to the total moles of the polyols of the first polyol fraction, the reactive diluent, the water and, if present, the polyols of the second polyol fraction. Such ratios may result in the formation of a polyurethane foam having a particularly favourable combination of high flexibility and high flame retardance. In addition, the composition may be more easily mixed in a static mixer prior to application. Furthermore, such ratios help maintain the overall dimensional stability of the cured foam product in between the cells.

[0044] The polyisocyanate preferably comprises polyphenylisocyanate, more preferably polymethylene polyphenylene isocyanate, e.g. diphenylmethane diisocyanate. Such polyisocyanates may impart to the polyurethane foam a particularly high resistance to species such as water, oil, solvents and halogens. A commercial example of a suitable polyisocyanate is PAPI MDI-27.The polyisocyanate has a number average molecular weight of from 260 to 400, more preferably from 300 to 380, even more preferably from 320 to 360, still even more preferably from 330 to 350. This may result in more three-dimensional crosslinking, helping achive help maintain the overall dimensional stability of the cured foam product in between the cells.

[0045] The polyisocyanate preferably has an average isocyanate functionality of greater than 2, more preferably from 2.5 to 3, even more preferably from 2.6 to 2.8. The level of cross-linking in the polyurethane foam resulting from such isocyanate functionalities, in combination with the hydroxyl functionality of the first polyol fraction, may impart a particularly desirable flexibility.

[0046] The A part and / or the B part, preferably the A part, preferably further comprises a gel catalyst. The presence of a gel catalyst may help to initiate reaction of the polyols and the polyisocyanate and may help to initiate foaming.

[0047] Preferably, the gel catalyst: comprises tin; and / or comprises a metal (e.g. tin) salt of a fatty acid, preferably wherein the fatty acid comprises from 8 to 15 carbon atoms, more preferably from 9 to 12 carbon atoms; and / or comprises a salt of alkyl tin, preferably dimethyl tin; and / or comprises or consists of dimethyldineodecanoatetin (also known as dimethyl bis [(1-oxoneodecyl) oxy] stannane, dimethyltin dineodecanoate, and DMBOS). Such gel catalysts may be particularly effective at initiating reaction of the polyols and the polyisocyanate and / or initiating foaming. In addition, such gel catalysts may function as chain terminators in the polyurethane foam. In comparison to gel catalysts used in conventional two-part potting compositions, such gel catalysts of the present invention may result in longer curing times and foaming times, for example curing times of up to 60 minutes. Accordingly, the use of such gel catalysts may help to reduce the occurrence of voids in the polyurethane foam. Since such catalysts are capable of catalysing the polyurethane reaction and foaming, this avoids the need to incorporate multiple catalysts into the composition.Preferably, the gel catalyst is the only catalyst contained in the two-part potting composition. This may avoid the unfavourable situation where, after the formation of the polyurethane foam, one or more gel catalysts remain as separate phases within the polyurethane foam. In addition, this may avoid unfavourably fast foaming and / or curing.

[0048] The A part and / or the B part, preferably the A part, preferably further comprises a surfactant. The presence of a surfactant may improve the wettability of the blowing agent with the polyols and may result in a soft, uniform microcellular structure.

[0049] The surfactant preferably comprises or consists of a polydimethylsiloxanepolyoxyalkylene block copolymer, more preferably dimethylsiloxane- ethylene oxide block copolymer. Such copolymer may be particularly effective surfactants. A commercial example of a suitable surfactant is ADDSIL 13950.

[0050] The A part and / or the B part, preferably the A part, preferably further comprises a flame retardant. This may improve the flame retardance of the polyurethane foam, and may result in a flammability grade LIL94 VO.

[0051] The flame retardant preferably comprises or consists of graphite, more preferably expandable graphite. Such flame retardants may be more environmentally friendly than phosphate-based flame retardants, which may form phosphoric acid. Such flame retardants may be more moisture resistant than fluoride-based flame retardants. Such flame retardants may be particularly effective at increasing the flame retardance of the polyurethane foam, and may result in a flammability grade LIL94 VO. Such flame retardants may be less heavy than flame retardants contained in conventional potting compositions, thereby reducing the weight of the final polyurethane foam. A commercial example of a suitable expandable graphite is Carboflamex PU300.

[0052] The A part and / or the B part, preferably the A part, preferably further comprises a wetting additive. This may improve the wetting of graphite and / or expandible graphitewith the polyols. As a result, the graphite and / or expandible graphite may be better dispersed in the polyurethane. The wetting additive preferably comprises or consists of an alkylammonium salt of a copolymer, more preferably a high molecular-weight copolymer. Such wetting agents may be particularly suitable for improving the wetting of graphite and / or expandible graphite with the polyols. A commercial example of a suitable wetting additive is BYK 9076. In contrast to anti-settling additives used in conventional two-part potting compositions, wetting agent may improve the wettability of the graphite and / or expandible graphite with the polyols without causing a gradual increase in viscosity.

[0053] Preferably, the A part comprises: from 50 to 74 wt.% of the first polyol fraction, preferably from 50 to 65 wt.%; and / or from 5 to 25 wt.% of the second polyol fraction, preferably from 10 to 20 wt.%; and / or from 1 to 20 wt.% of the reactive diluent, preferably from 5 to 15 wt.%; and / or from 0.5 to 5 wt.% of the water, preferably from 1 to 3 wt.%.

[0054] Preferably, the A part and / or the B part, more preferably the A part, comprises: from 0.0001 to 0.002 wt.% gel catalyst, preferably from 0.0005 to 0.0015 w.%; and / or from 0.5 to 2 wt.% surfactant, preferably from 0.7 to 1.1 wt.%; and / or from 5 to 25 wt.% flame retardant, preferably from 10 to 20 wt.% and / or from 0.1 to 3 wt.% wetting additive, preferably from 1 to 2 wt.%.

[0055] The composition is preferably substantially free of, more preferably free of, phosphate and / or phosphate-containing compounds and / or phosphate-based compounds. The term “substantially free of” as used herein, may encompass the situation in which the composition comprises 2 wt.% or less phosphate and / or phosphate containing compounds, preferably 1 wt.% or less, even more preferably 0.1 wt.% or less, still even more preferably 0.01 wt.% or less.

[0056] In a further aspect, the present invention provides a two-part potting composition comprising:

[0057] an A part comprising:a first polyol fraction, the first polyol fraction having a weighted average hydroxyl functionality of from 2.1 to 2.9, and

[0058] water; and

[0059] a B part comprising a polyisocyanate.

[0060] The advantages and preferable features of the first aspect apply equally to this aspect.

[0061] In a further aspect, the present invention provides a two-part potting composition comprising:

[0062] an A part comprising:

[0063] a first polyol fraction, the first polyol fraction having a weighted average hydroxyl number of from 70 to 90, and

[0064] water; and

[0065] a B part comprising a polyisocyanate.

[0066] The advantages and preferable features of the first aspect apply equally to this aspect.

[0067] The two-part potting composition may be in cured form.

[0068] The cured form preferably has a Shore Asker C hardness of from 5 to 50, more preferably from 10 to 45, even more preferably from 15 to 35. This may provide a battery potted with such a composition a particularly high vibration resistance.

[0069] The cured form is preferably in the form of a foam.

[0070] In a further aspect, the present invention provides a method of potting electric vehicle (EV) cells, the method comprising:

[0071] providing two or more EV cells;

[0072] providing the two-part composition as described herein;

[0073] contacting the A part with the B part; andapplying the A part and the B part to the two or more EV cells.

[0074] The advantages and preferable features of the first aspect apply equally to this aspect.

[0075] Contacting the A part with the B part may comprising mixing the A part with the B part, for example using a static mixer. Applying the A part and the B part to the two or more EV cells may comprise spraying.

[0076] In a further aspect, the present invention provides an electric vehicle (EV) battery comprising:

[0077] two or more EV cells; and

[0078] the two-part potting composition as described herein.

[0079] The advantages and preferable features of the first aspect apply equally to this aspect.

[0080] In a further aspect, the present invention provides an electric vehicle comprising the electric vehicle (EV) battery as described herein.

[0081] The advantages and preferable features of the first aspect apply equally to this aspect.

[0082] In a further aspect, the present invention provides use of the two-part potting composition as described herein for potting an electric vehicle battery.

[0083] The advantages and preferable features of the first aspect apply equally to this aspect.

[0084] In a further aspect, the present invention provides use of the two-part potting composition as described herein for preventing thermal runaway in an electric vehicle battery.The advantages and preferable features of the first aspect apply equally to this aspect.

[0085] In a further aspect, the present invention provides use of the two-part potting composition as described herein for potting an electronic device.

[0086] The advantages and preferable features of the first aspect apply equally to this aspect.

[0087] In a further aspect, the present invention provides use of the two-part potting composition as described herein for potting a printed circuit board.

[0088] The advantages and preferable features of the first aspect apply equally to this aspect.

[0089] In a further aspect, the present invention provides use of the two-part potting composition as described herein as a conformal coating for a printed circuit board.

[0090] The advantages and preferable features of the first aspect apply equally to this aspect.

[0091] The invention will now be further described with reference to the following clauses:

[0092] 1. A two-part potting composition comprising:

[0093] an A part comprising:

[0094] a first polyol,

[0095] a second polyol,

[0096] a reactive diluent, and

[0097] water; and

[0098] a B part comprising a polyisocyanate.2. The two-part potting composition of clause 1 , wherein the reactive diluent comprises or consists of an aromatic alcohol, preferably a phenolic lipid.

[0099] 3. The two-part potting composition of clause 2, wherein the phenolic lipid:

[0100] has a hydroxy functionality of 1 ; and / or

[0101] comprises a single hydroxy group; and / or

[0102] comprises a carbon chain having from 10 to 20 carbon atoms, preferably from 13 to 17, more preferably from 14 to 16, even more preferably 15; and / or

[0103] comprises an unsaturated carbon chain; and / or

[0104] comprises or consists of cardanol; and / or

[0105] is cashew nut shell-derived (CNSL-derived).

[0106] 4. The two-part potting composition of any preceding clause, wherein the two-part potting composition is for potting a battery, preferably an electric vehicle (EV) battery.

[0107] 5. The two-part potting composition of any preceding clause, wherein the first polyol has a number average molecular weight (Mn) of from 1000 to 3000, preferably from 1500 to 2100, more preferably from 1700 to 1900, even more preferably about 1800.

[0108] 6. The two-part potting composition of any preceding clause, wherein the first polyol has an average hydroxy functionality of from 2 to 3, preferably from 2.5 to 2.9, more preferably from 2.6 to 2.8.

[0109] 7. The two-part potting composition of any preceding clause, wherein the first polyol is derived from castor oil.

[0110] 8. The two-part potting composition of any preceding clause, wherein the second polyol comprises or consists of a linear polyester polyol9. The two-part potting composition of clause 8, wherein the linear polyester polyol comprises polycaprolactone polyol.

[0111] 10. The two-part potting composition of any preceding clause, wherein the second polyol has a number average molecular weight of from 300 to 1000, preferably from 350 to 450.

[0112] 11. The two-part potting composition of clause 1 or clause 2, wherein the molar ratio of X : Y in the two-part potting composition is from 1.5:1 to 3:1 , preferably from 1.8:1 to 2.2:1 , wherein X corresponds to the moles of polyisocyanate and Y corresponds to the total moles of the first polyol, the second polyol, the reactive diluent and the water.

[0113] 12. The two-part potting composition of clause 1 or clause 2, wherein the molar ratio of X : Y in the two-part potting composition is from 4:1 to 8:1 , preferably from 5:1 to 6:1 , wherein X corresponds to the moles of isocyanate functional groups and Y corresponds to the total moles of the first polyol, the second polyol, the reactive diluent and the water.

[0114] 13. The two-part potting composition of any preceding clause, wherein the polyisocyanate comprises polyphenylisocyanate, preferably polymethylene polyphenylene isocyanate.

[0115] 14. The two-part potting composition of any preceding clause, wherein the polyisocyanate has a number average molecular weight of from 260 to 400, preferably from 300 to 380, more preferably from 320 to 360, even more preferably from 330 to 350.

[0116] 15. The two-part potting composition of any preceding clause, wherein the polyisocyanate has an average isocyanate functionality of greater than 2, preferably from 2.5 to 3, more preferably from 2.6 to 2.8.16. The two-part potting composition of any preceding clause, wherein the A part and / or the B part, preferably the A part, further comprises a gel catalyst.

[0117] 17. The two-part potting composition of clause 16, wherein the gel catalyst: comprises tin; and / or

[0118] comprises a metal salt of a fatty acid, preferably wherein the fatty acid comprises from 8 to 15 carbon atoms, more preferably from 9 to 12 carbon atoms; and / or comprises a salt of alkyl tin, preferably dimethyl tin; and / or

[0119] comprises or consists of dimethyldineodecanoatetin.

[0120] 18. The two-part potting composition of clause 16 or clause 17, wherein the gel catalyst is the only catalyst contained in the two-part potting composition.

[0121] 19. The two-part potting composition of any preceding clause, wherein the A part and / or the B part, preferably the A part, further comprises a surfactant.

[0122] 20. The two-part potting composition of clause 19, wherein the surfactant comprises or consists of a polydimethylsiloxane-polyoxyalkylene block copolymer, preferably dimethylsiloxane- ethylene oxide block copolymer.

[0123] 21. The two-part potting composition of any preceding clause, wherein the A part and / or the B part, preferably the A part, further comprises a flame retardant.

[0124] 22. The two-part potting composition of clause 21 , wherein the flame retardant comprises or consists of graphite, preferably expandable graphite.

[0125] 23. The two-part potting composition of any preceding clause, wherein the A part and / or the B part, preferably the A part, further comprises a wetting additive.

[0126] 24. The two-part potting composition of clause 23, wherein the wetting additive comprises or consists of an alkylammonium salt of a copolymer, preferably a high molecular-weight copolymer.25. The two-part potting composition of any preceding clause, wherein the A part comprises:

[0127] from 50 to 74 wt.% of the first polyol, preferably from 50 to 65 wt.%; and / or from 5 to 25 wt.% of the second polyol, preferably from 10 to 20 wt.%; and / or from 1 to 20 wt.% of the reactive diluent, preferably from 5 to 15 wt.%; and / or from 0.5 to 5 wt.% of the water, preferably from 1 to 3 wt.%.

[0128] 26. The two-part potting composition of any preceding clause, wherein the A part and / or the B part, preferably the A part, comprises:

[0129] from 0.0001 to 0.002 wt.% gel catalyst, preferably from 0.0005 to 0.0015 w.%; and / or from 0.5 to 2 wt.% surfactant, preferably from 0.7 to 1.1 wt.%; and / or

[0130] from 5 to 25 wt.% flame retardant, preferably from 10 to 20 wt.% and / or

[0131] from 0.1 to 3 wt.% wetting additive, preferably from 1 to 2 wt.%.

[0132] 27. The two-part potting composition of any preceding clause, wherein the composition is substantially free of (less than 98 wt.%, preferably less than 99 wt.%, more preferably less than 99.9 wt.%), preferably free of, phosphate and / or phosphate-containing compounds and / or phosphate-based compounds.

[0133] 28. The two-part potting composition of any preceding clause in cured form.

[0134] 29. The two-part potting composition of clause 28, wherein the cured form has a Shore A hardness of from 40 to 60, preferably from 45 to 55, more preferably from 48 to 52.

[0135] 30. The two-part potting composition of clause 28 or clause 29, wherein the cured form is in the form of a foam.

[0136] 31. A method of potting electric vehicle (EV) cells, the method comprising:

[0137] providing two or more EV cells;

[0138] providing the two-part composition of any of clauses 1 to 27;contacting the A part with the B part; and

[0139] applying the A part and the B part to the two or more EV cells.

[0140] 32. An electric vehicle (EV) battery comprising:

[0141] two or more EV cells; and

[0142] potting material surrounding the two or more EV cells,

[0143] wherein the potting material comprises the potting material of any of clauses 28 to 30.

[0144] 33. An electric vehicle (EV) battery comprising:

[0145] two or more EV cells; and

[0146] potting material surrounding the two or more EV cells,

[0147] wherein the potting material comprises a polyurethane formed from:

[0148] a first polyol,

[0149] a second polyol,

[0150] a reactive diluent,

[0151] water, and

[0152] a polyisocyanate.

[0153] 34. An electric vehicle comprising the electric vehicle (EV) battery of clause 32 or 33.

[0154] 35. Use of the two-part potting composition of any of clauses 1 to 30 for potting an electric vehicle battery.

[0155] 36. Use of the two-part potting composition of any of clauses 1 to 30 for preventing thermal runaway in an electric vehicle battery.

[0156] 37. Use of the two-part potting composition of any of clauses 1 to 30 for potting an electronic device.38. Use of the two-part potting composition of any of clauses 1 to 30 for potting a printed circuit board.

[0157] 39. Use of the two-part potting composition of any of clauses 1 to 30 as a conformal coating for a printed circuit board.

[0158] The invention will now be described in relation to the following non-limiting example.

[0159] Sample preparation

[0160] A two-part potting composition was prepared. The A part had the following composition:

[0161]

[0162]

[0163] The B part had the following composition:

[0164]

[0165] The A part and the B part were combined and cured to produce foam block samples 1-4.

[0166] Thermal shock and cycling testing

[0167] Samples 1 -4 were subjected to thermal shock and cycling testing according to AIS 156 ANNEX 8B using the following steps:

[0168] • Sub cycle 1 : Set the thermal chamber to -40 °C. Allow specimens to stabilise at this temperature for 6 hours.

[0169] • Transition: Rapidly raise the temperature to 60 °C, ensuring the transition is swift (within 5 minutes).

[0170] • Sub cycle 2: Maintain the specimens at 60 °C for 6 hours.

[0171] • Repeat the above cycles for five thermal cycles.The percentage of moisture absorption (the amount of water absorbed by the foams relative to their initial dray weight) under thermal shock was calculated using the following formula:

[0172] Moisture absorption percentage = ((W2(wet) - W1 (dry)) / W1 (dry)) x 100, where W1 (dry) is the initial weight of the foam and W2(wet) is the final weight of the foam. The results are set out in the table below:

[0173]

[0174] The average moisture absorption percentage under thermal shock (-40 to +60 °C) was 0.73 %.

[0175] The following observations were made:

[0176] Sample 1 : Sample 1 underwent thermal shock cycles from -40 to +60 °C, which caused slight expansion and contraction of the foam. After moisture exposure, the foam showed a minimal increase in weight, indicating low moisture absorption. The material’s ability to resist moisture after thermal shock suggests a moderate level of durability against environmental extremes.

[0177] Sample 2: Similar to Sample 1 , Sample 2 experienced only a slight increase in weight after thermal shock exposure and moisture absorption. The minimal moisture uptake suggests that this foam formulation is stable under extreme temperature cycles and does not significantly absorb moisture under those conditions.Sample 3: Sample 3 showed a slightly higher moisture absorption rate of 1.18 %. The increase in weight indicates a moderate moisture adsorption capacity. While the sample maintained its integrity under thermal shock, the relatively higher moisture absorption may indicate slightly more porosity or microstructural changes that allow moisture to ingress.

[0178] Sample 4: Sample 4 showed no moisture absorption after thermal shock exposure. This result suggests that the foam has a high resistance to moisture uptake under thermal stress, making it potentially more suitable for environments subject to frequent temperature fluctuations.

[0179] The following general observations were made:

[0180] 1. Minimal Weight Change: The weight differences observed across the samples (ranging from 0.00% to 1.18% moisture absorption) were relatively small. This suggests that the foam did not undergo significant swelling or structural deformation after exposure to moisture, indicating that the polymer matrix retained its integrity throughout the testing process.

[0181] 2. Stable Foam Structure: Despite undergoing extreme temperature fluctuations, the Pll foam samples exhibited no visible signs of deformation, cracking, or breaking apart. The foam maintained its original shape and density, suggesting that the thermal shock cycles did not compromise its physical structure or cause any irreversible changes.

[0182] 3. Consistent Moisture Absorption Behaviour: The moisture absorption percentages were consistent across most of the samples (0.85% in Samples 1 and 2) and only slightly higher in Sample 3 (1.18%). The lack of sign variability in moisture uptake suggests that the foam’s molecular structure remained stable, and no degradation or excessive porosity occurred due to the thermal shock.4. No Change in Physical Properties: After the testing, the foam samples were found to retain their original flexibility, texture, and compressibility, which are essential mechanical properties of Pll foam. This indicates that the molecular bonds and physical structure of the polymer were not adversely affected by the temperature cycles and moisture exposure.

[0183] The moisture absorption behaviour of Pll foam subjected to thermal shock (temperature cycling from -40°C to 60°C) revealed that:

[0184] ■ Most of the Pll foam samples exhibited low to moderate moisture absorption, with percentages ranging from 0.00% to 1.18%.

[0185] ■ The foam’s ability to resist moisture, even after undergoing extreme temperature fluctuations, suggests that it maintains its insulating properties and does not significantly degrade in humid or high-temperature environments.

[0186] ■ Given these findings, it can be concluded that the Pll foam used in the battery packs, subjected to these rigorous thermal shock conditions, performs adequately in terms of moisture absorption. The results meet the required standards for IPrated protection, ensuring that the battery packs are fully protected from moisture ingress. Therefore, the performance of the battery packs under thermal shock and moisture exposure is deemed acceptable, confirming that they are fully IP-rated and capable of withstanding environmental stresses without compromising safety or functionality.

[0187] Thermal runaway tests

[0188] The two-part potting composition described above was subjected to thermal runaway tests at the India Institute of Technology - Madras. Testing was caried out on a battery module in the size of 3*3 cells, where the central cell was heated up to a temperature of 110°C and the same was maintained for one hour and then 5C overcharging was done on it. Thermal runaway was initiated on the central cell, smoke was observed at the peak exotherm temperature of 360 °C, and then dissipated but the flame did not spread to the other neighboring cells and wascontained within the foam surrounding the affected cell only. Foam filling and seepage within the cells was very good and were uniformly distributed within.

[0189] The foregoing detailed description has been provided by way of explanation and illustration, and is not intended to limit the scope of the appended claims. Many variations in the presently preferred embodiments illustrated herein will be apparent to one of ordinary skill in the art and remain within the scope of the appended claims and their equivalents.

Claims

Claims1. A two-part potting composition comprising:an A part comprising:a first polyol fraction,a reactive diluent comprising an aromatic alcohol, andwater; anda B part comprising a polyisocyanate.

2. The two-part potting composition of claim 1 , wherein the aromatic alcohol comprises a phenolic lipid.

3. The two-part potting composition of claim 2, wherein the phenolic lipid:has a hydroxy functionality of 1 ; and / orcomprises a single hydroxy group; and / orcomprises a carbon chain having from 10 to 20 carbon atoms, preferably from 13 to 17, more preferably from 14 to 16, even more preferably 15; and / orcomprises an unsaturated carbon chain; and / orcomprises or consists of cardanol; and / oris cashew nut shell-derived (CNSL-derived).

4. The two-part potting composition of any preceding claim, wherein the two-part potting composition is for potting a battery, preferably an electric vehicle (EV) battery.

5. The two-part potting composition of any preceding claim, wherein the first polyol fraction has a number average molecular weight (Mn) of from 500 to 2500, more preferably from 1800 to 2200.

6. The two-part potting composition of any preceding claim, wherein the first polyol fraction has a weighted average hydroxy functionality of from 2 to 3, preferably from 2.5 to 2.9, more preferably from 2.6 to 2.8.

7. The two-part potting composition of any preceding claim, wherein the first polyol fraction has a hydroxyl value of from 70 to 90, preferably from 75 to 85.

8. The two-part potting composition of any preceding claim, wherein the first polyol fraction comprises a copolymer comprising triglyceride structural units and fatty acid diester structural units.

9. The two-part potting composition of claim 8, wherein the triglyceride comprises ricinolein and / or the fatty acid of the fatty acid ester comprises ricinoleic acid.

10. The two-part potting composition of any preceding claim, wherein the first polyol fraction is derived from castor oil, preferably castor oil that has undergone hydrogenolysis.

11. The two-part potting composition of any preceding claim, wherein the A part further comprises a second polyol fraction.

12. The two-part potting composition of claim 11 , wherein the second polyol fraction comprises or consists of a linear polyester polyol13. The two-part potting composition of claim 12, wherein the linear polyester polyol comprises polycaprolactone polyol.

14. The two-part potting composition of any preceding claim, wherein the second polyol fraction has a number average molecular weight of from 300 to 1000, preferably from 350 to 450.

15. The two-part potting composition of any preceding claim, wherein the molar ratio of X : Y in the two-part potting composition is from 1.5:1 to 3:1 , preferably from 1.8:1 to 2.2:1 , wherein X corresponds to the moles of polyisocyanate and Y corresponds to the total moles of the polyols of the first polyol, the reactive diluent, the water and, if present, the polyols of the second polyol.

16. The two-part potting composition of any preceding claim, wherein the molar ratio of X : Y in the two-part potting composition is from 4:1 to 8:1 , preferably from 5:1 to 6:1 , wherein X corresponds to the moles of isocyanate functional groups and Y corresponds to the total moles of the polyols of the first polyol fraction, the reactive diluent, the water and, if present, the polyols of the second polyol fraction.

17. The two-part potting composition of any preceding claim, wherein the polyisocyanate comprises polyphenylisocyanate, preferably polymethylene polyphenylene isocyanate.

18. The two-part potting composition of any preceding claim, wherein the polyisocyanate has a number average molecular weight of from 260 to 400, preferably from 300 to 380, more preferably from 320 to 360, even more preferably from 330 to 350.

19. The two-part potting composition of any preceding claim, wherein the polyisocyanate has an average isocyanate functionality of greater than 2, preferably from 2.5 to 3, more preferably from 2.6 to 2.8.

20. The two-part potting composition of any preceding claim, wherein the A part and / or the B part, preferably the A part, further comprises a gel catalyst.

21. The two-part potting composition of claim 20, wherein the gel catalyst:comprises tin; and / orcomprises a metal salt of a fatty acid, preferably wherein the fatty acid comprises from 8 to 15 carbon atoms, more preferably from 9 to 12 carbon atoms; and / orcomprises a salt of alkyl tin, preferably dimethyl tin; and / orcomprises or consists of dimethyldineodecanoatetin.

22. The two-part potting composition of claim 20 of claim 21 , wherein the gel catalyst is the only catalyst contained in the two-part potting composition.

23. The two-part potting composition of any preceding claim, wherein the A part and / or the B part, preferably the A part, further comprises a surfactant.

24. The two-part potting composition of claim 23, wherein the surfactant comprises or consists of a polydimethylsiloxane-polyoxyalkylene block copolymer, preferably dimethylsiloxane- ethylene oxide block copolymer.

25. The two-part potting composition of any preceding claim, wherein the A part and / or the B part, preferably the A part, further comprises a flame retardant.

26. The two-part potting composition of claim 25, wherein the flame retardant comprises or consists of graphite, preferably expandable graphite.

27. The two-part potting composition of any preceding claim, wherein the A part and / or the B part, preferably the A part, further comprises a wetting additive.

28. The two-part potting composition of claim 27, wherein the wetting additive comprises or consists of an alkylammonium salt of a copolymer, preferably a high molecular-weight copolymer.

29. The two-part potting composition of any preceding claim, wherein the A part comprises:from 50 to 74 wt.% of the first polyol fraction, preferably from 50 to 65 wt.%; and / orfrom 5 to 25 wt.% of the second polyol fraction, preferably from 10 to 20 wt.%; and / orfrom 1 to 20 wt.% of the reactive diluent, preferably from 5 to 15 wt.%; and / or from 0.5 to 5 wt.% of the water, preferably from 1 to 3 wt.%.

30. The two-part potting composition of any preceding claim, wherein the A part and / or the B part, preferably the A part, comprises:from 0.0001 to 0.002 wt.% gel catalyst, preferably from 0.0005 to 0.0015 w.%; and / orfrom 0.5 to 2 wt.% surfactant, preferably from 0.7 to 1.1 wt.%; and / or from 5 to 25 wt.% flame retardant, preferably from 10 to 20 wt.% and / or from 0.1 to 3 wt.% wetting additive, preferably from 1 to 2 wt.%.

31. The two-part potting composition of any preceding claim, wherein the composition is substantially free of, preferably free of, phosphate and / or phosphate-containing compounds and / or phosphate-based compounds.(less than 98 wt.%, preferably less than 99 wt.%, more preferably less than 99.9 wt.%)32. A two-part potting composition comprising:an A part comprising:a first polyol fraction, the first polyol fraction having a weighted average hydroxyl functionality of from 2.1 to 2.9, andwater; anda B part comprising a polyisocyanate.

33. A two-part potting composition comprising:an A part comprising:a first polyol fraction, the first polyol fraction having a weighted average hydroxyl number of from 70 to 90, andwater; anda B part comprising a polyisocyanate.

34. The two-part potting composition of any preceding claim in cured form.

35. The two-part potting composition of claim 34, wherein the cured form has a Shore Asker C hardness of from 5 to 50, preferably from 10 to 45, more preferably from 15 to 35.

36. The two-part potting composition of claim 34 or claim 35, wherein the cured form is in the form of a foam.

37. A method of potting electric vehicle (EV) cells, the method comprising:providing two or more EV cells;providing the two-part composition of any of claim 1 to 33;contacting the A part with the B part; andapplying the A part and the B part to the two or more EV cells.

38. An electric vehicle (EV) battery comprising:two or more EV cells; andthe two-part potting composition of any of claims 34 to 36.

39. An electric vehicle comprising the electric vehicle (EV) battery of claim 38.

40. Use of the two-part potting composition of any of claims 1 to 36 for potting an electric vehicle battery.

41. Use of the two-part potting composition of any of claims 1 to 36 for preventing thermal runaway in an electric vehicle battery.

42. Use of the two-part potting composition of any of claims 1 to 36 for potting an electronic device.

43. Use of the two-part potting composition of any of claims 1 to 36 for potting a printed circuit board.

44. Use of the two-part potting composition of any of claims 1 to 36 as a conformal coating for a printed circuit board.

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