Polyurethane acrylate hybrid composites containing orthoester moisture scavengers and methods for preparing same

Abstract

Processes of preparing a composite article may include: (i) providing a polyurethane resin formulation including: an isocyanate component, an isocyanate-reactive component, and an orthoester moisture scavenger; (ii) impregnating a reinforcing material with the polyurethane resin formulation under vacuum conditions; and (iii) curing the polyurethane-acrylate hybrid resin formulation to form the composite article, wherein the orthoester moisture scavenger is present at a loading level of 0.1 to 15% in the isocyanate-reactive component. Processes may use one or more orthoester moisture scavengers with the formula RC(OR')3, where R is hydrogen or an alkyl group with 1 to 5 carbons, and R' is an alkyl group with 1 to 5 carbons, such as triethyl orthoformate and triethyl orthopropionate. In some cases, orthoester moisture scavengers are added at a percent by weight (wt%) of the isocyanate-reactive component and the isocyanate component in a range of 0.1 wt% to 10 wt%.

Description

[0001] POLYURETHANE ACRYLATE HYBRID COMPOSITES CONTAINING ORTHOESTER MOISTURE SCAVENGERS AND METHODS FOR PREPARING SAME

[0002] FIELD

[0003] Embodiments relate to polyurethane compositions and composite articles containing polyurethane-acrylate hybrid resins and orthoester moisture scavengers.

[0004] BACKGROUND

[0005] Composite materials are widely used in various industries due to their superior mechanical properties and versatility. Polyurethane composites, in particular, are known for their excellent strength, durability, and resistance to environmental factors. These composites may be manufactured using infusion processes, where a polyurethane resin is brought into contact with a reinforcement material, such as glass fibers, and / or a core material, such as balsa wood, under vacuum conditions.

[0006] One of the challenges in manufacturing polyurethane composites is controlling moisture content. Moisture can react with isocyanate components in the resin, leading to the formation of carbon dioxide and causing foaming in the resulting polymer. This foaming can create defects in the composite material, negatively impacting its performance. Traditional methods to control moisture, such as pre-drying reinforcement materials or using moisture scavengers, have limitations, especially under vacuum conditions.

[0007] SUMMARY

[0008] In an aspect, embodiments disclosed herein are directed to processes of preparing a composite article, including:© providing a polyurethane resin formulation including: an isocyanate component, an isocyanate-reactive component, and an orthoester moisture scavenger; (ii) impregnating a reinforcing material with the polyurethane resin formulation under vacuum conditions: and (iii) curing the polyurethane-acrylate hybrid resin formulation to form the composite article, wherein the orthoester moisture scavenger is present at a loading level of 0.1 to 15% in the isocyanate-reactive component.

[0009] Processes may use one or more orthoester moisture scavengers with the formula RC(OR’)3, where R is hydrogen or an alkyl group with 1 to 5 carbons, and R' is an alkyl group with 1 to 5 carbons, such as triethyl orthoformate and triethyl orthopropionate. In some cases,orthoester moisture scavengers are added at a percent by weight (wt%) of the isocyanate-reactive component and the isocyanate component in a range of 0.1 wt% to 10 wt%.

[0010] Polyurethane-acrylate hybrid compositions may include an isocyanate -reactive component having one or more hydroxy functional acrylate monomers according to the formula:

[0011] O

[0012] R,yyR2onH

[0013] where R1 is selected from hydrogen, methyl or ethyl, R2 is selected from alkylene groups having 2-6 carbon atoms, 2,2-bis(4-phenylene) propane, l,4-bis(methylene)benzene, 1,3-bis(methylene)benzene, l,2-bis(methylene) benzene, and n is an integer selected from 1 to 6.R1 is selected from hydrogen, methyl or ethyl, R2 is selected from alkylene groups having 2-6 carbon atoms, 2,2-bis(4-phenylene) propane, l,4-bis(methylene)benzene, l,3-bis(methylene)benzene, l,2-bis(methylene) benzene, and n is an integer selected from 1 to 6.

[0014] DETAILED DESCRIPTION

[0015] Embodiments relate to polyurethane compositions and composite articles containing polyurethane resins and orthoester moisture scavengers. These composite articles are manufactured using vacuum-assisted fabrication processes, such as infusion, and orthoester moisture scavengers minimize foaming and defects caused by moisture contamination.

[0016] In addition to polyurethane compositions, orthoester moisture scavengers may be incorporated into newer classes of materials such as polyurethane-acrylate hybrid compositions, which introduce a number of potential advantages, such as suitable reactivity profiles, low heat release, good surface quality, toughness, and superior fatigue resistance compared to alternative resins like polyesters, vinyl esters, and epoxies. The use of orthoesters as moisture scavengers in these compositions enhances process efficiency by reducing the need for pre-drying steps and minimizing defects, resulting in high-performance composite articles. Moreover, methods disclosed herein demonstrate that orthoester moisture scavengers exhibit good foam control when compared to other water scavengers, particularly under vacuum cure conditions and simultaneously in contact with reinforcement textiles and / or core materials that, if not pre -dried, will be sources of accessible water in different extents. This processing environment is typically found in industrial vacuum assisted infusion processes for making, for example, wind blades.

[0017] Embodiments disclosed herein relate to polyurethane systems and polyurethane-acrylate hybrid systems containing orthoester moisture scavengers to reduce moisture sensitivity andimprove the appearance and mechanical properties of articles formed therefrom. Systems may include one or more orthoester-based moisture scavengers that can be combined with isocyanatereactive components to sequester residual moisture. Particularly, orthoester-based moisture scavengers react with moisture to prevent the formation of carbon dioxide from the reaction between isocyanate and water, thus reducing foaming.

[0018] Polyurethane and polyurethane-acrylate hybrid compositions may be generated by reacting an isocyanate component with an isocyanate-reactive component containing one or more moisture scavengers. The isocyanate component can include at least one compound having an isocyanate group. The isocyanate component may include one or more isocyanates and polyisocyanates having an average of at least 2.0 isocyanate groups per molecule. The isocyanate components may contain moieties that are aliphatic, cycloaliphatic, alicyclic, arylaliphatic, aromatic, and / or derivatives thereof. Preferably, the isocyanate components contain moieties where the NCO group is directly attached to an aromatic ring. Examples of compounds suitable for use in isocyanate components include monomeric methylene diphenyl diisocyanate (MDI), modified MDI, oligomeric MDI, polymeric MDI, toluene 2,4- / 2,6-diisocyanate (TDI), and the like. Isocyanates may have an average isocyanate functionality from 2 to 5, 2.2 to 5, or 2.2 to 4. The isocyanate can have an isocyanate equivalent weight (EW) in a range of 75 g / eq to 250 g / eq, 80 g / eq to 200 g / eq, or 80 to 175 g / eq.

[0019] The isocyanate component may include one or more prepolymers formed by the reaction of a polyisocyanate compound and a polyol, including, for example, the reaction of 4,4’ -MDI and tripropylene glycol, or a reaction of ethylene oxide capped propoxylated glycerine and 4,4’ -MDI. Prepolymers may have an NCO content of 5 wt% to 30 wt%, 10 wt% to 25 wt%, or 15 wt% to 25 wt%. An isocyanate component may include a prepolymer at a percent by weight (wt%) in a range of 5 wt% to 70 wt%, 10 wt% to 65 wt%, or from 15 wt% to 60 wt%.

[0020] Isocyanate-reactive components may include a polyol blend containing one or more polyether polyols and / or one or more polyester polyols at a percent by weight of the blend (wt%) in a range of 35 wt% and 75 wt%, and one or more hydroxy functionalized (meth) acrylates in a range of 35 wt% and 75 wt%. As used herein, use of “(meth)” in conjunction with various acrylate species indicates that the scope of the specification covers both the acrylate or methacrylate variations of the referenced compound.

[0021] Isocyanate-reactive components may include one or more polyether polyols prepared by polyaddition of alkylene oxides such as propylene oxide and / or ethylene oxide onto polyhydroxy functional starter compounds in the presence of catalysts known in the art. Polyether polyols maybe prepared from a starter compound and one or more alkylene oxides, for example, ethylene oxide, butylene oxide, and / or propylene oxide. Starter compounds may include molecules having 2 to 8 hydroxyl groups per molecule such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, 1 ,4-butanediol, 1,6-hexanediol, bisphenol A, glycerol, trimethylolpropane, pentaerythritol, sugars and sugar alcohols such as sucrose and sorbitol, and the like. Polyether polyols may have an average hydroxyl number (OH number) as determined according to ASTM D4274-21 in a range of 100 mg KOH / g to 500 mg KOH / g, 150 mg KOH / g to 450 mg KOH / g, or 200 mg KOH / g to 450 mg KOH / g.

[0022] Polyester polyols disclosed herein include reaction products of one or more carboxylic diacids and a polyol having an OH functionality of 2 to 4. Suitable carboxylic acids may include aromatic diacids or anhydrides and C4 to C12 aliphatic diacids. Suitable polyols for the formation of polyesters include one or more alkylene glycols or polyalkylene glycols having a hydroxy functionality of 2 to 4, such as ethylene glycol, 1,2- or 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, glycerine, and the like. Example polyester polyols include polyesters of phthalic anhydride and di ethylene glycol, and polyesters of a C4 to Cl 2 diacid such as succinic acid or adipic acid and diethylene glycol. Polyester polyols may have an average hydroxyl number (OH number) as determined according to ASTM D4274-21 in a range of 100 mg KOH / g to 500 mg KOH / g, 150 mg KOH / g to 450 mg KOH / g, or 200 mg KOH / g to 450 mg KOH / g.

[0023] Isocyanate-reactive components may include one or more polyester polyols at a percent by weight (wt%) ranging from 10 wt% to 40 wt%, from 15 wt% to 35 wt%, or from 15 wt% to 30 wt%.

[0024] The isocyanate-reactive component may include one or more hydroxy functional (meth)acrylate monomers that react with the isocyanate component and / or polymerize in the presence of a free radical initiator to produce a polyurethane-acrylate hybrid composition. Hydroxy functional (meth)acrylate monomers may have the general structure:

[0025] O

[0026]

[0027] wherein R1 is selected from hydrogen, methyl or ethyl; R2 is selected from alkylene groups having 2-6 carbon atoms, 2,2-bis(4-phenylene) propane, 1 ,4-bis(methylene)benzene, 1,3-bis(methylene)benzene, l,2-bis(methylene) benzene; and n is an integer selected from 1-6. Hydroxy functional (meth)acrylate monomers may include hydroxy Cl-10 alkyl (meth)acrylatemonomers, such as hydroxyethyl acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate monomer, and the like.

[0028] Hydroxy functional (meth) acrylates may be added at a percent by weight (wt%) of the isocyanate-reactive component and isocyanate component in a range of 10 wt% to 40 wt%, from 20 wt% to 38 wt%, from 25 wt% to 35 wt%, or from 27 wt% to 32 wt%. For example, the hydroxy functional (meth)acrylate may be added to an isocyanate reactive component at a percent by weight ranging from 20 wt% to 80 wt% to provide a final concentration for the resulting polyurethane-acrylate hybrid composition.

[0029] The isocyanate-reactive component includes one or more orthoester moisture scavengers. Orthoester moisture scavengers include compounds described by the formula:

[0030] RC(OR’)s

[0031] where R is hydrogen or an alkyl group with 1 to 5 carbons and R’ is an alkyl group with 1 to 5 carbons. In some cases, one or more R’ may be the same or different alkyl groups. Examples of suitable orthoesters and poly(orthoesters) include, but are not limited to, orthoacetates, such as triethyl orthoformate, trimethyl orthoacetate, triethyl orthoacetate, tripropyl orthoacetate, triisopropyl orthoacetate, and poly(orthoacetates); orthoformates, such as trimethyl orthoformate, triethyl orthoformate, tripropyl orthoformate, triisopropyl orthoformate, and poly (orthoformates); and orthopropionates, such as trimethyl orthopropionate, triethyl orthopropionate, tripropyl orthopropionate, triisopropyl orthopropionate, and poly(orthopropionates). Suitable orthoesters also may be orthoesters of polyfunctional alcohols, such as glycerin and / or ethylene glycol. In some cases, the orthoester moisture scavengers may include triethyl orthoformate and triethyl orthopropionate.

[0032] Orthoester moisture scavengers may be added at a percent by weight (wt%) of the polyurethane acrylate hybrid composition in a range of 0.1 wt% to 15 wt%, 0.1 wt% to 10 wt%, or 1 wt% to 10 wt%.

[0033] Polyurethane-acrylate hybrid compositions may include one or more initiators (e.g., free radical initiators) added to the isocyanate component. The initiator includes but is not limited to peroxides, persulfides, peroxycarbonates, peroxyboric acid, azo compounds or other suitable radical initiators that can initiate curing of a double bond-containing compound. Suitable initiators include azo compounds or peroxides. Preferably, the azo compound can be 2,2-azobisisobutyronitrile (AIBN); the peroxide can be selected from the group consisting of tert-butyl peroxybenzoate, butyl 4,4-di(tert-butylperoxy)valerate, di-tert-amyl peroxide, dicumyl peroxide, di(tert-butylperoxyisopropyl) benzene, 2,5-dimethyl-2,5-di(tert-butylperoxyl)hexane, tert-butylcumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxyl)hexyne-3, di-tert-butyl peroxide, 3,6,9-triethyl-3,6,9-trimethyl-l,4,7-triperoxonane, isopropylcumyl hydroperoxide, 1, 1,3,3-tetramethylbutyl hydroperoxide, cumyl hydroperoxide, tert-butyl hydroperoxide, and any combinations thereof.

[0034] Polyurethane-acrylate hybrid compositions may include an initiator at a percent by weight (wt%) that is larger than zero, including at least 0.1 wt%, at least 0.2 wt%, or at least 0.3 wt%, and at most 6.0 wt%, at most 5.0 wt%, or at most 4.0 wt%.

[0035] Isocyanate-reactive components may include one or more accelerators, including metal salts, such as cobalt salts and zinc salts that catalyze radical polymerization reactions. Accelerators may be added at a percent by weight (wt%) of the polyurethane acrylate hybrid composition in a range of 0 wt% to 0.15 wt%, 0.001 wt% to 0.10 wt%, or 0.01 wt% to 0.05 wt%.

[0036] Catalysts for promoting polyurethane reactions may also be added, including amine catalysts, organometallic catalysts, or a mixture thereof. Amine catalysts may include one or more of triethylamine, tributylamine, triethylenediamine, N-ethylmorpholine, N,N,N',N'-tetramethylethylenediamine, pentamethyldiethylenetriamine, N-methylaniline, N.N-dimethyl aniline, and the like. Organometallic catalysts may include an organotin compound, e.g., tin (II) acetate, tin (II) octanoate, tin ethylhexanoate, tin laurate, dibutyl tin oxide, dibutyl tin dichloride, dibutyl tin diacetate, dibutyl tin maleate, dioctyl tin diacetate, and the like. Catalysts may be added at a percent by weight (wt%) of the polyurethane acrylate hybrid composition in a range of 0 wt% to 0.15 wt%, 0.001 wt% to 0.10 wt%, or 0.01 wt% to 0.05 wt%.

[0037] The isocyanate-reactive component may also contain one or more additives including surfactants, crosslinkers, plasticizers, fillers, smoke suppressants, fragrances, reinforcements, dyes, colorants, pigments, preservatives, odor masks, flame retardants, internal mold release agents, biocides, antioxidants, UV stabilizers, antistatic agents, thixotropic agents, adhesion promoters, cell openers, and the like.

[0038] Polyurethane-acrylate hybrid compositions may include one or more silicone or organic defoamers added at a percent by weight (wt%) of the polyurethane acrylate hybrid composition in a range of 0.05 wt% to 5 wt%, 0.1 wt% to 1.5 wt%, or 0.1 wt% to 1 wt%.

[0039] Polyurethane-acrylate hybrid compositions may be used in any suitable process for developing articles and composites, including molding, injection, vacuum infusion, pultrusion, and the like. In one method, polyurethane-acrylate hybrid compositions may be prepared by combining the isocyanate component and the isocyanate-reactive component to form a mixture; processing the mixture in a mold to produce a molded article; and demolding the molded article.Polyurethane-acrylate hybrid compositions may be used to prepare a molded composite part. For the preparation of the composite part, the polyurethane-poly(meth)acrylate reactive composition is mixed with a reinforcement material or injected into the reinforcement material, e.g., by vacuum-assisted resin transfer molding (VARTM) and / or resin transfer molding (RTM). Suitable reinforcement materials include any one or more of glass fibers, carbon nanotubes, carbon fibers, polyester fibers, natural fibers, aramid fibers, nylon fibers, basalt fibers, boron fibers, silicon carbide fibers, asbestos fibers, whiskers, hard particles, metal fibers, and the like.

[0040] Composite articles prepared using the inventive polyurethane-acrylate hybrid compositions may include one or more reinforcement materials at a percent by weight (wt%) in a range of 1 wt% to 90 wt%, 30 wt% to 90 wt%, 50 wt% to 85 wt%, or 50 wt% to 80 wt%.

[0041] Composite articles prepared using the inventive polyurethane-acrylate hybrid compositions may further include one or more core materials that facilitate the molding and weight reduction of a composite material. Core materials may include polystyrene foams, polyester PET foams, polyimide PMI foams, polyvinyl chloride foam, polyurethane foams, metal foams, celluloses, woods such as balsa wood, and the like.

[0042] Polyurethane-acrylate hybrid compositions may produce articles and composites having excellent mechanical properties, e.g., a high thermal deformation temperature, high tensile and flexural strength, high resistance to fatigue, high ductility, and low shrinkage rate. Articles and composites may be used in the manufacture of wind generator blades, wind generator nacelle housings, watercraft propeller blades, hulls, interior and exterior automobile decorative parts, automobile bodies, truck floors, radomes, machinery structural members, decorative parts and structural members for architectures and bridges, and the like.

[0043] While formulation components and properties have been disclosed individually, it is envisioned that component elements may be included, excluded, or combined in any manner or subcombination utilizing any of the above concentration ranges and nested subranges therein. Further, that the recited formulation properties may be similarly achieved through various combinations of the recited components within the recited ranges.

[0044] EXAMPLES

[0045] The following examples are provided to illustrate the embodiments of the invention, but are not intended to limit the scope thereof. Table 1 provides the materials used in the following examples, and Table 2 details the moisture scavengers used in the samples.Table 1: Components used in the examples.

[0046] Component Description Supplier Isocyanate Reactive

[0047] Components (A Side)

[0048] Polyol 1 Propox y la ted g ly cerine, The Dow OH number ~ 384 mg KOH / g Chemical Company HPMA Hydroxy propyl (Meth) acrylate. The Dow OH number 392 mg KOH / g Chemical Company Defoamer BYK A535 BYK Moisture Scavenger See Table 2 Various Accelerator 553s Cobalt complex (1.9% cobalt content) Nouryon containing cobalt octoate

[0049] Isocyanate Components

[0050] (B Side)

[0051] Isocyanate 1 Mixture of Pure and Polymeric MDI, The Dow NCO%=32%, f=2.2, visc@25C = 50 mPa.s Chemical Company Prepolymer I Formed by the reaction of 4.4’ -MDI and The Dow tripropylene glycol. NCO%=23%, Chemical visc@25C = 575 mPa.s Company Prepolymer 2 Formed by the reaction of Polyol 3 (12,6%). The Dow Polyol 4 (3 / .0% Isocyanate 1 t-'l*8,%) and Chemical Isocyanate 2 (18.1%), NC0%=15% Company Polyol 3 Polypropylene glycol. OH number = 56 mg The Dow KOH / g Chemical Company Polyol 4 Propoxylated glycerine, with 1597 EO The Dow capped, OH number - 28 mg KOH / g Chemical Company Isocyanate 2 Monomeric MDI consisting of about 67% The Dow 4,4’-MDI and 33% 2,4’-MDI content Chemical

[0052] Company

[0053]

[0054] Initiator 1 Tert-Butyl Peroxybenzoate (TBPB) Nouryon

[0055] Table 2: Moisture scavengers used in the examples.

[0056] Moisture Scavenger

[0057] Description Supplier (MS)

[0058] Orthoester MS 1 Tri ethyl orthopropionate (TEOP) Sigma Aldrich Orthoester MS 2 triethyl orthoformate (TEOP) Sigma Aldrich Comp. MSI 3-buty!-2-(heptan-3-yl)- 1 ,3- Keyser & Mackay oxazolidine

[0059] Comp. MS 2 Dimethoxy propane Sigma Aldrich Comp. MS3 Vinyl Trimethoxysilane Sigma Aldrich Zeolite powder in Castor Oil The Dow Chemical Comp. MS4

[0060]

[0061] 50% w / w CompanyN , N -dibenzy liden

[0062] Comp, MS 5 Keyser & Mackay

[0063]

[0064] polyoxypropylene diamine

[0065] Example 1 : PU-Acrylate Hybrid Sample formulation

[0066] The formulations are listed in Table 3 (all values pbw, unless specified) were prepared by the following procedure. For the isocyanate-reactive component, a total of 424g of formulated polyol was prepared containing 24g of moisture scavenger (6 pbw) and mixed by SpeeMixer® at 2350 rpm for 30 seconds. In the specific case of the sample CE6, 48 pbw of a 50 / 50 zeolite-castor oil pre -blended component was added to totalize 24 pbw of zeolite powder in the recipe. For sample CE1, which does not contain moisture scavengers, 424g of formulated polyol was added to the SpeeMixer® and mixed at 2350 rpm for 30 seconds.

[0067] For the isocyanate component, the isocyanate blend was degassed thoroughly before use (minimum 6 hours) to eliminate entrapped air. This treatment was not applied to the formulated polyol to avoid evaporation of some of the moisture scavengers. 100g of reactive mix was poured into a plastic cup and blended by SpeeMixer® at 2350 rpm for 30 seconds. The reactive mixture was then vacuum degassed for 10 minutes.

[0068] Example 2: Sample testing by reactive mix casting

[0069] Approximately 50g of reactive mixture was poured into plastic containers as per the following conditions.

[0070] Test Condition 1 : Neat resin was poured in a container and cured at atmospheric pressure and 35 °C for 1 hour followed by cure at 80°C for 2 hours.

[0071] Test Condition 2: Neat resin was poured in a container having a block of balsa wood glued in the bottom to totalize approximately 2% balsa and 98% resin in w / w. Then it was cured under vacuum conditions (~10 mbar) and 35°C for 1 hour followed by curing at 80°C for 2 hours.

[0072] Qualitative Assessment through Visual Inspection: For each of the two test conditions, visual inspection was performed on the individual samples using back light. A scale was defined as follows: NF: No foaming; Fl: Very few bubbles, randomly dispersed; F2: Some foaming; F3: Extensive foaming.

[0073] Acceptability criteria for composite resin is Fl, corresponding to minimal presence of bubbles, hence limited defects in the composite article. A visual appearance corresponding to F2 or F3 is not acceptable.Table 3: Formulation and results for samples.

[0074] Component CE1 IE1 CE2 Isocyanate-Reacti ve Component

[0075] Polyol 1 36.9 36.9 36.9 HPMA 62.7 62.7 62.7 Defoamer 0.40 0.40 0.40 Accelerator 553s 0.04 0.04 0.04 Orthoester MS 1 - 6.00 - Comp. MS I - 6.00 Isocyanate Component

[0076] Isocyanate 1 72.8 72.8 72.8 Prepolymer 1 18.7 18.7 18.7 Prepolymer 2 13.5 13.5 13.5 Initiator 1 2.07 2.07 2.07 NCO Index 102 102 102 Weight Ratio w / w Isocyanate to reactive component 1 .07 1.01 1.01 Total pbw for Isocyanate-reactive Component and Isocyanate

[0077] 207.04 213.2 213.2 Component

[0078] Test Condition 1: Visual Appearance NF NF

[0079] Gelled

[0080]

[0081] Test Condition 2: Visual Appearance F3 FI

[0082] Table 4; Formulation and results for samples.

[0083] Component CE3 CE4 CE5 CE6 Isocyana te-R eac u ve Co rnponen t

[0084] Polyol I 36.9 36.9 36.9 36.9 HPMA 62.7 62.7 62.7 62.7 Defoamer 0.40 0.40 0.40 0.40 Accelerator 553s 0.04 0.04 0.04 0.04 Comp. MS2 6.00

[0085] Comp. .MS ' - 6.00 Comp. MSI 6.00 Comp. MS5 6.00 - Isocyanate Component

[0086] Isocyanate 1 72,8 72.8 72.8 73.74 Prepolymer 1 18.7 18.7 18.7 18.91 Prepolymer 2 13,5 13.5 13.5 13.65 Initiator 1 2.07 2.07 2.07 2.10 NCO Index 102 102 102 102 Weight Ratio w / w Isocyanate to reactive component 1.01 1.01 1.01 1.02 Total pbw for Isocyanate -reactive Component and Isocyanate

[0087] 213.2 213.2 213.2 214.00 Component

[0088] Test Condition 1 : Visual Appearance NF NF NF NF

[0089]

[0090] Test Condition 2: Visual Appearance F3 F2 F3 F2Table 3 and 4 show that the effectiveness of a certain moisture scavenger depends on the presence or absence of a hygroscopic substrate, in this case, balsa wood. Additionally, the pressure conditions in which the resin cures, being atmospheric or under vacuum, also affect the moisture scavenger performance. As shown, condition 1 is the less demanding condition for foam formation, and all the formulations, including the controls, cured without the presence of foam. Atmospheric cure on neat resin samples is not discriminative of moisture scavenger performance; hence all moisture scavengers show similar performance in terms of visual appearance. However, condition 2 involves the use of vacuum during the cure process involving a polyurethane reaction mix and balsa wood. This is the most stringent condition, considering that balsa wood can pick up water in the range of 7-12% w / w. All samples foamed, but sample IE1 containing the orthoester as scavenger showed clearly better performance.

[0091] Example 3 : Preparation of composite panel by infusion

[0092] In this example, formulation samples were used to manufacture composite panels by the following infusion process. Initially, an infusion layout was prepared by cutting unidirectional (UD) glass fiber mats (650 g / m2) into 60 cm x 60 cm plies. On an infusion table lined with an adhesive release foil (brand), a polyester peel ply (Easy Composite) was positioned. Subsequently, four plies of the UD glass fiber were placed on top, followed by a second peel ply and a flow mesh. Resin distributors and entry and exit tubes were arranged as per standard practices in the field.

[0093] The entire setup was then covered with a vacuum plastic bag (Easy Composite), secured using sticky tapes, and subjected to full vacuum. Samples were formulated as described in Table 5, and manually blended to prepare approximately 2 liters of reactive mixture in a plastic bucket, which was subsequently degassed for 5 minutes. The entry plastic tube was inserted into the plastic bucket, and the entry valve was opened, allowing the resin to infuse over the glass and peel ply setup at ambient temperature. Upon the resin front reaching the exit tube, both entry and exit valves were closed. The vacuum was adjusted to 200 mBar, and the temperature was ramped to 90°C, allowing the composite to cure for 3 hours.

[0094] Post-Curing Process: Following the curing process, the composite was removed from the table, and the peel ply was peeled off for visual inspection. Specimens were then cut and tested for Interlaminar Shear Stress (ILSS) in accordance with ISO 14130.

[0095] Qualitative Assessment through Visual Inspection: For each of the two test conditions, visual inspection was performed on individual samples using backlight. The following scale wasdefined for assessment: NF: No foaming; Fl: Very few bubbles, randomly dispersed; F2: Some foaming; F3: Extensive foaming.Table 5: Formulations and results for samples.

[0096] Component IE2 CE7 CE8 Isocyanate-Reacti ve Component

[0097] Polyol 1 36.9 36.9 36.9 HPMA 62.7 62.7 62.7 Defoamer 0.40 0.40 0.40 Accelerator 553s 0.04 0.04 0.04 Orthoester MS 2 6.00

[0098] Comp. MS 2 6.00

[0099] Comp. MS3 6.00 Isocyanate Component

[0100] Isocyanate 1 72.8 72.8 72.8 Prepolymer 1 18.7 18.7 18.7 Prepolymer 2 13.5 13.5 13.5 Initiator 1 2.07 2.07 2.07 NCO Index 102 102 102 Weight Ratio w / w Isocyanate to reactive component 1.01 1.01 1.01 Total pbw for Isocyanate-reactive Component and

[0101] 213.2 213.2 213.2 Isocyanate Component

[0102] Infusion

[0103] 8x650g / m 8x650g / m 8x650g / m Reinforcement

[0104] 2UD2UD2UD Vacuum, mBar < 20 < 20 < 20 Curing

[0105] Vacuum, mBar 200 200 200 Curing cycle 3h @ 90C 3h @ 90C 3h @ 90C Composite Visual aspect NF F2 F2 ILSS 0° Av 70.0 42.2 34.2 ILSS 0°stdev 1.2 4.4 2.70 ILSS 0° CV% 1.7 10.5 7.88

[0106]

[0107] Number of specimens 10 10 10

[0108] Table 5 illustrates that composite panels prepared under similar conditions show very different appearance depending on the moisture scavenger used. When using Orthoester MS 2 (TEOF) the resulting composite does not show the presence of any bubbles, while comparative examples does show evidence of foaming. Short beam interlaminar shear stress is a good way to characterize the resin to fiber bonding along the direction of the continuous fibers. The results in Table 5 demonstrates that using Orthoester MS2 (TEOF) it is possible to get almost the double strength compared with the comparative examples. The dispersion (CV%) is also reduced compared with CE7 and 8 which is a further indication of quality consistency.While the foregoing is directed to exemplary embodiments, other and further embodiments may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

1. Claims1. A process of preparing a composite article, comprising:(i) providing a polyurethane resin formulation comprising:an isocyanate component,an isocyanate-reactive component, andan orthoester moisture scavenger;(ii) impregnating a reinforcing material with the polyurethane resin formulation under vacuum conditions; and(iii) curing the polyurethane-acrylate hybrid resin formulation to form the composite article, wherein the orthoester moisture scavenger is present at a loading level of 0.1 to 15% in the isocyanate-reactive component.

2. The process of claim 1, wherein the reinforcing material is selected from the group consisting of glass fibers, carbon fibers, and aramid fibers.

3. The process of claim 1, wherein the one or more orthoester moisture scavengers have the formula:RC(OR’)3where R is hydrogen or an alkyl group with 1 to 5 carbons and R' is an alkyl group with 1 to 5 carbons.

4. The process of claim 1, wherein the one or more orthoester moisture scavengers is selected from the group consisting of triethyl orthoformate and triethyl orthopropionate.

5. The process of claim 1, wherein the one or more orthoester moisture scavengers are added at a percent by weight (wt%) of the isocyanate-reactive component and the isocyanate component in a range of 0.1 wt% to 10 wt%.

6. The process of claim 1, wherein the isocyanate-reactive component further comprises a cobalt salt accelerator.

7. The process of claim 1, wherein the isocyanate -reactive component comprises:one or more hydroxy functional acrylate monomers according to formula:wherein Ri is selected from hydrogen, methyl or ethyl, R2 is selected from alkylene groups having 2-6 carbon atoms, 2,2-bis(4-phenylene) propane, 1,4- bis(methylene)benzene, 1 ,3-bis(methylene)benzene, 1 ,2-bis(methylene) benzene, and n is an integer selected from 1 to 6.

8. The process of claim 7, wherein the hydroxy functional acrylate monomers are added at a percent by weight (wt%) of the polyurethane acrylate hybrid composition in a range of 15 wt% to 40 wt%.

9. The process of claim 1, wherein the isocyanate-reactive component comprises one or more poly ether polyols and / or one or more polyester polyols.

10. The process of claim 9, wherein one or more poly ether polyols and / or one or more polyester polyols are added at a percent by weight (wt%) of the isocyanate-reactive component and the isocyanate component in a range of 10 wt% to 40 wt%.

11. A composite article prepared by the process of claim 1.

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