Flame retardant resin and composite preform

Abstract

A curable resin composition includes 100 parts by weight of a curable resin, 0.1 to 5 parts by weight of a first catalyst that is lithium iodide, and 75 parts by weight or less of a flame retardant. A curable preform composition includes the curable resin composition and a fiber reinforcement. At least 5 parts by weight of the curable resin in the curable preform composition is a benzoxazine resin in 100 parts by weight of the curable resin. A method for preparing a curable preform composition includes mixing 100 parts of a curable resin, 0.15 to 5 parts by weight of a first catalyst, 75 parts or less of a flame retardant, and a fiber reinforcement to prepare an uncured curable preform composition, and curing the uncured curable preform composition to prepare the curable preform composition.

Description

Background Technology

[0001] Sheet molding blends (SMCs) are reinforced moldable blends commonly used in the production of compression-molded articles. SMCs typically consist of a resin composition and fiber reinforcement. Unsaturated polyester (UPE) is widely used as the resin composition for SMCs. However, UPE has poor flame retardancy; therefore, when flame retardancy is required for applications, a considerable amount of flame retardant (FR) must be added. SMCs with a large amount of FR often result in the formation of highly brittle char, which negatively impacts their mechanical properties. Furthermore, some types of FR, such as phosphorus additives, can produce toxic fumes upon combustion.

[0002] Due to technical challenges, such as balancing rapid curing, viscosity control, and drapability of SMC, other types of resin compositions have not been widely used. Therefore, there is a need for continuous improvement of moldable blends reinforced with SMC. Summary of the Invention

[0003] The present invention is provided to introduce some concepts further described below in the detailed description. The present invention is not intended to identify key or essential features of the claimed subject matter, nor is it intended to help limit the scope of the claimed subject matter.

[0004] In one aspect, the embodiments disclosed herein relate to a curable resin composition. The curable resin composition comprises 100 parts by weight of a curable resin, 0.1 to 5 parts by weight of a first catalyst (which is lithium iodide), and 75 parts by weight or less of a flame retardant. Of the 100 parts by weight of the curable resin, at least 5 parts by weight are benzoxazine resin.

[0005] In another aspect, the embodiments disclosed herein relate to a curable preform composition. The curable preform composition comprises a curable resin composition and fiber reinforcement. The curable resin composition comprises 100 parts by weight of a curable resin, 0.1 to 5 parts by weight of a first catalyst (which is lithium iodide), and 75 parts by weight or less of a flame retardant. Of the 100 parts by weight of the curable resin, at least 5 parts by weight of the curable resin in the curable preform composition is a benzoxazine resin.

[0006] In another aspect, the embodiments disclosed herein relate to a method for producing a curable preform composition. The method includes mixing 100 parts by weight of a curable resin, 0.15 to 5 parts by weight of a first catalyst, 75 parts or less of a flame retardant and fiber reinforcement to produce an uncured curable preform composition, and curing the uncured curable preform composition to produce a curable preform composition. Of the 100 parts by weight of the curable resin, at least 5 parts by weight of the curable resin in the curable preform composition is a benzoxazine resin, and the first catalyst is lithium iodide.

[0007] Other aspects and advantages of the claimed subject matter will be apparent from the following description and the appended claims. Attached Figure Description

[0008] Figure 1 This is a flowchart of a method for preparing a curable preform composition according to one or more embodiments.

[0009] Figure 2 This is a flowchart of a method for preparing a curable preform composition according to one or more embodiments.

[0010] Figure 3 This is a flowchart of a method for preparing a curable preform composition according to one or more embodiments.

[0011] Figure 4 The blending of fiber-reinforced and unreinforced resin mixtures according to one or more embodiments is shown. Detailed Implementation

[0012] This disclosure generally relates to curable resin compositions and curable preform compositions. A curable resin composition includes a curable resin, a first catalyst, and a flame retardant (FR) agent. A curable preform composition comprises a curable resin composition that includes a curable resin, a first catalyst, a FR agent, and fiber reinforcement. A “preform” (“preform composition”, “composite preform”) means a composition comprising a formulated resin composition and fiber reinforcement. The specific form of the preform is not limited, but may include solid, semi-solid, and paste forms. A curable preform composition may be a sheet molding blend (SMC).

[0013] Curable resin compositions

[0014] In one or more embodiments, the curable resin composition comprises a curable resin. The curable resin may include a benzoxazine resin. Benzoxazine resins typically contain a high amount of nitrogen, which can act as an inherent flame retardant. Furthermore, benzoxazine resins tend to form chars, which reduces the formation of volatile compounds, further contributing to the flame retardancy of the composition. In one or more embodiments, the benzoxazine resin may be any benzoxazine component disclosed in U.S. Publication No. 2017 / 0183450 A1, which is hereby incorporated by reference.

[0015] In one or more embodiments, the benzoxazine resin contains at least one benzoxazine (BZ) group (along the main chain or at the end caps), or is formed from a BZ monomer (ring-opening during the formation of the benzoxazine-based resin) or a combination thereof. The BZ group in the BZ monomer or benzoxazine-based resin may have a structure represented by formula (I), which may be referred to as a monofunctional BZ:

[0016] (I)

[0017] R1 may represent one or more of a hydrogen atom, a hydrocarbon group, a substituted hydrocarbon group, and a functional group. The BZ group in one or more embodiments may include one or more substituents represented by R1. As used throughout the specification, the term "hydrocarbon group" may refer to a branched, straight-chain, and / or cyclic hydrocarbon group, which may be saturated or unsaturated. The hydrocarbon group may be a primary, secondary, and / or tertiary hydrocarbon. As used throughout the specification, the term "substituted hydrocarbon group" may refer to a hydrocarbon group in which at least one hydrogen atom is replaced by a non-hydrogen group that produces a stable compound (as defined above). Such substituents may be selected from (but not limited to) halogens, hydroxyl groups, alkoxy groups, oxo groups, alkylyl groups, aryloxy groups, alkylyloxy groups, amino groups, alkylamino groups, arylamino groups, disubstituted amines, alkylylamino groups, arylylamino groups, arylalkylamino groups, substituted alkylylamino groups, substituted arylamino groups, unsubstituted arylalkylamino groups, thiols, alkylthiols, arylalkylthiols, alkylthiocarbonyl groups, arylthiocarbonyl groups, arylalkylthiocarbonyl groups, alkylsulfonyl groups, arylsulfonyl groups, arylalkylsulfonyl groups, sulfonamides, substituted sulfonamides, nitro groups, cyano groups, carboxyl groups, carbamoyl groups, alkoxycarbonyl groups, aryl groups, substituted aryl groups, guanidine groups, vinyl groups, acetylene groups, acrylate groups, cyanate groups, epoxides, and heterocyclic groups and mixtures thereof. The functional group may be selected from (but is not limited to) halogen, hydroxyl, alkoxy, oxo, amino, amide, thiol, alkylthio, sulfonyl, alkylsulfonyl, sulfonamide, substituted sulfonamide, nitro, cyano, carboxyl, carbamoyl, alkoxycarbonyl vinyl, acetylene, acrylate, cyanate, epoxide group and mixtures thereof.

[0018] R2 is not particularly limited and can represent any group mentioned with respect to R1. However, in certain embodiments, R2 can be a BZ-containing moiety. When R2 is a BZ-containing moiety, the benzoxazine resin may include a bis-BZ unit. The bis-BZ unit may have a structure represented by formula (II), which may be referred to as a diamine-type BZ:

[0019] (II)

[0020] R1 represents a group as discussed above with respect to formula (I). R1' may be the same as or different from R1. R3 may represent a hydrocarbon group or a substituted hydrocarbon group. In a particular embodiment, R3 may represent an aromatic group selected from (but not limited to) benzene, bibenzyl, diphenylmethane, naphthalene, anthracene, diphenyl ether, diphenyl sulfone ether, bis(phenoxy)benzene, stilbene, phenanthrene, fluorine, and their substituted variants. In one or more embodiments, R3 may represent a group with a molecular weight in the range of about 14 to 100,000 Da, or 14 to 10,000 Da, or 14 to 1,000 Da.

[0021] In one or more embodiments, the benzoxazine resin has a structure as shown in formula (III), which may be referred to as a diphenol type BZ:

[0022] (III)

[0023] In formula (III), R1 and R1' represent groups equivalent to R2 in formula (I) above. R3 represents the group discussed above with respect to formula (II).

[0024] In one or more embodiments, the benzoxazine resin may be a main-chain benzoxazine polymer (MCBP). The MCBP may have BZ as part of a repeating unit. In one or more embodiments, the benzoxazine resin may be a main-chain benzoxazine oligomer (MCBO). The MCBO may be chemically similar to the MBCP, wherein the benzoxazine is part of a repeating unit in the main chain.

[0025] In one or more embodiments, the benzoxazine resin may be a polymer formed by the reaction of a bisbenzoxazine monomer with a bifunctional comonomer having phenol, amine and / or thiol functional groups, and the polymer contains at least one end capping group as a crosslinkable group.

[0026] In one or more embodiments, at least 5 parts by weight of the curable resin in 100 parts by weight of the curable resin included in the curable resin composition and / or the curable preform composition is benzoxazine resin (based on the total weight of the curable resin in the curable resin composition and / or the curable preform composition, at least 5% by weight of the curable resin is benzoxazine resin). In one or more embodiments, benzoxazine resin is included in the curable resin in an amount of about 5 parts by weight to about 100 parts by weight of the curable resin in the curable resin composition and / or the curable preform composition (based on the total weight of the curable resin in the curable resin composition and / or the curable preform composition, benzoxazine resin is included in the curable resin in an amount of about 5% by weight to 100% by weight). In one or more embodiments, the content of benzoxazine resin in 100 parts by weight of curable resin ranges from a lower limit selected from any one of 5, 15, 20, 30, 40, 50 and 60 parts by weight to an upper limit selected from any one of 70, 80, 90 and 100 parts by weight, wherein any lower limit may be paired with any upper limit.

[0027] Curable resins may also include unsaturated polyester resins, phenolic resins, vinyl ester resins, epoxy resins, and combinations thereof.

[0028] The curable resin may include one type of resin, such as benzoxazine resin, as the first curable resin. The curable resin may further include at least one second curable resin. For example, the curable resin may include benzoxazine resin as the first curable resin, and unsaturated polyester resin and / or phenolic resin as at least one second curable resin.

[0029] In one or more embodiments, the curable resin composition comprises a first catalyst. The first catalyst may include lithium iodide (LiI). LiI can cure benzoxazine resin via a ring-opening polymerization reaction. Based on 100 parts by weight of the curable resin, the amount of the first catalyst in the curable resin composition may range from about 0.1 to about 5 parts by weight. In one or more embodiments, based on 100 parts by weight of the curable resin, the amount of the first catalyst in the curable resin composition ranges from a lower limit selected from any one of 0.1, 0.3, 0.5, and 1.0 parts by weight to an upper limit selected from any one of 3, 4, and 5 parts by weight, wherein any lower limit may be paired with any upper limit.

[0030] In one or more embodiments, the curable resin composition comprises a second catalyst. The second catalyst may be a catalyst for curing benzoxazine resins, a catalyst for other curable resins included in the composition, such as phenolic resins or unsaturated polyester resins, or a catalyst for two or more curable resins included in the composition. Examples of the second catalyst include tert-butylperoxy-2-ethylhexyl ester (TBEC), azobisisobutyronitrile (AIBN), hexamethylenetetramine (HMTA), 1,8-diazabicyclo(5.4.0)undec-7-ene (DBU), alkaloids, amine salts, amidine blends, methyl ethyl ketone peroxide (MEKP), benzyl peroxide (BPO), acetylacetone peroxide (AAP), organic peroxides, acid catalysts (sulfuric acid, oxalic acid, hydrochloric acid), acid anhydrides, phenols, and combinations thereof.

[0031] Based on 100 parts by weight of the curable resin, the amount of the second catalyst in the curable resin composition can range from about 0.1 to about 5 parts by weight. In one or more embodiments, based on 100 parts by weight of the curable resin, the amount of the second catalyst in the curable resin composition ranges from a lower limit selected from any one of 0.1, 0.3, 0.5, and 1.0 parts by weight to an upper limit selected from any one of 3, 4, and 5 parts by weight, wherein any lower limit may be paired with any upper limit.

[0032] In one or more embodiments, the curable resin composition includes a flame retardant (FR) agent. FR agents may include aluminum trihydride (ATH), magnesium hydroxide (MnH4), phosphorus-containing blends, bromine-containing blends, chlorine-containing blends, nitrogen-containing blends, and antimony oxides, such as antimony oxide (III) and antimony oxide (V).

[0033] The amount of FR agent in the curable resin composition is not limited, provided that mixing of the composition can be practically carried out and the viscosity of the curable resin composition, the curable preform composition, and the mechanical properties of the cured preform composition remain within suitable ranges. Based on 100 parts by weight of the curable resin, the amount of FR agent in the curable resin composition can be 75 parts by weight or less. In one or more embodiments, based on 100 parts by weight of the curable resin, the amount of FR agent ranges from about 0.1 to about 75 parts by weight. In one or more embodiments, based on 100 parts by weight of the curable resin, the amount of FR agent in the curable resin composition can range from a lower limit selected from any one of 0.1, 0.3, 0.5, 1, 5, and 10 parts by weight to an upper limit selected from any one of 5, 10, 20, 30, 40, 50, and 75 parts by weight, wherein any lower limit can be paired with any mathematically compatible upper limit.

[0034] In one or more embodiments, the curable resin composition includes a thickener. The thickener may include, but is not limited to, magnesium oxide (MgO), pyrolytic silica, Group IIA metal oxides and hydroxides, aluminum acylates, aluminum chelates, and combinations thereof.

[0035] Based on 100 parts by weight of the curable resin, the amount of thickener in the curable resin composition may be 10 parts by weight or less. In one or more embodiments, based on 100 parts by weight of the curable resin, the amount of thickener ranges from about 0 to about 10 parts by weight. In one or more embodiments, based on 100 parts by weight of the curable resin, the amount of thickener in the curable resin composition may range from a lower limit selected from any one of 0, 0.1, 0.2, 0.3, and 0.5 parts by weight to an upper limit selected from any one of 1, 2, 3, 4, 5, and 10 parts by weight, wherein any lower limit may be paired with any upper limit.

[0036] In one or more embodiments, the curable resin composition includes a filler. The filler may include, but is not limited to, calcium carbonate, zinc stearate, hydroquinone, nanosheets, silica, kaolin, pigments, antistatic agents, calcium stearate, diluents, and combinations thereof. In one or more embodiments, the curable resin composition does not include a filler.

[0037] Based on 100 parts by weight of the curable resin, the amount of filler in the curable resin composition may be 20 parts by weight or less. In one or more embodiments, based on 100 parts by weight of the curable resin, the amount of filler ranges from about 0 to about 20 parts by weight. In one or more embodiments, based on 100 parts by weight of the curable resin, the amount of filler in the curable resin composition may range from a lower limit selected from any one of 0, 0.1, 0.2, 0.3, and 0.5 parts by weight to an upper limit selected from any one of 1, 2, 3, 4, 5, and 20 parts by weight, wherein any lower limit may be paired with any upper limit.

[0038] Properties - Curable resin compositions

[0039] In one or more embodiments, the dynamic viscosity of the curable resin composition at 85°C is in the range of about 15 Pa·s or lower, for example, in the range of about 1 to about 15 Pa·s, as measured by a rotational rheometer. In one or more embodiments, the temperature of the curable resin composition is 85°C or lower, for example, in the range of about 20 to 85°C, at which temperature the viscosity of the curable resin composition is 15 Pa·s or lower.

[0040] In one or more embodiments, the curable resin composition has a dynamic viscosity of 1 Pa·s or less at 100°C, as measured by a rotational rheometer. In one or more embodiments, the curable resin composition is cured at a temperature of 100°C or lower, for example in the range of about 75 to 100°C, at which temperature the viscosity of the curable resin composition is 1 Pa·s or lower.

[0041] In one or more embodiments, the curable resin composition has a dynamic viscosity, as measured by a rotational rheometer, in the range of about 20,000 to 100,000 Pa·s during the curing process. A curable resin composition with a viscosity within this range allows for non-sticky workability and lay-upability of the curable preform composition at room temperature, as well as sufficient viscosity at elevated temperatures. If the viscosity of the curable resin composition is below the aforementioned range, less glass fiber flow may occur, and the part may have a high resin fraction in the outermost region. If the viscosity is above the aforementioned range, the molded part may have unfilled portions. The cured curable resin composition can be obtained by subjecting the curable resin composition to the same curing process as that for the curable preform composition described in subsequent sections.

[0042] In one or more embodiments, as measured by differential scanning calorimetry (DSC), the curable resin composition has an initial curing temperature of about 180°C or lower.

[0043] In one or more embodiments, the peak curing temperature of the curable resin composition is about 220°C or lower, such as 220°C or lower, 210°C or lower, 200°C or lower, 190°C or lower, or 180°C or lower, as measured by DSC.

[0044] Compared to compositions with curing temperatures above 200°C, curable resin compositions with onset and peak curing temperatures within the aforementioned range exhibit broadened heat release properties over a longer period. Curable resin compositions with the aforementioned onset and peak temperature ranges allow for rapid curing, for example, achieving 75% or higher degree of cure within 5 minutes.

[0045] Curable preform composition

[0046] In one or more embodiments, the curable preform composition comprises a curable resin composition and fiber reinforcement. The curable resin composition in the curable preform composition may be a curable resin composition as described in the preceding section, and may include a curable resin, a first catalyst, and a FR agent. As previously mentioned, the curable resin composition may optionally include a second catalyst, a thickener, and a filler.

[0047] The fiber reinforcements included in the curable preform composition may be fibers commonly used in composite applications. Examples of fibers included in the fiber reinforcements include, but are not limited to, glass fibers (E-glass, high-strength glass), carbon fibers, aramid fibers, boron fibers, basalt fibers, ultra-high molecular weight polyethylene (UHMWPE) fibers, and combinations thereof. The fiber reinforcements may be short fibers, such as chopped and ground fibers, long fibers, nonwoven fabrics, woven fabrics, or stitch-woven fabrics. Short fibers are defined as fibers with lengths less than 30 cm, 20 cm, 10 cm, 5 cm, 1 cm, 5 mm, 1 mm, 0.5 mm, or 0.1 mm. The length of short fibers can range from about 0.001 mm to about 30 cm. Long fibers can have a length of at least 30 cm, 40 cm, or 50 cm. The fiber reinforcements may be randomly oriented such that the orientation of each fiber reinforcement is not particularly controlled, or the orientation of the fiber reinforcements may be controlled such that the fibers are oriented in a specific direction.

[0048] Based on 100 parts by weight of the curable resin, the amount of fiber reinforcement in the curable preform composition may be 60 parts by weight or less. In one or more embodiments, based on 100 parts by weight of the curable resin, the amount of fiber reinforcement ranges from about 1 to about 60 parts by weight. In one or more embodiments, based on 100 parts by weight of the curable resin, the amount of fiber reinforcement in the curable preform composition may range from a lower limit selected from any one of 1, 5, 10, and 20 parts by weight to an upper limit selected from any one of 30, 40, 50, and 60 parts by weight, wherein any lower limit may be paired with any upper limit.

[0049] Properties - Curable preform composition

[0050] In one or more embodiments, the curable preform composition has a resin flow rate of 20% or less. The resin flow rate percentage can be measured according to ASTM D3531. In one or more embodiments, the resin flow rate is measured by pressing a sample of a specific size at a temperature of 180°C and a pressure in the range of 4.8 MPa to 7 MPa for 5 minutes and obtaining the percentage weight difference of the sample before and after pressing.

[0051] In one or more embodiments, the curable preform composition exhibits sufficient layability. A curable resin composition exhibiting sufficient layability can conform to the desired shape or geometry without forming any defects / wrinkles during composite molding, fill the desired mold shape, and have a balance of resin flow at elevated temperatures to deliver fibers throughout the mold without overflowing.

[0052] In one or more embodiments, the curable preform composition has an initial curing temperature of about 180°C or lower, as measured by differential scanning calorimetry (DSC).

[0053] In one or more embodiments, the peak curing temperature of the curable preform composition is about 220°C or lower, such as 220°C or lower, 210°C or lower, 200°C or lower, 190°C or lower, or 180°C or lower, as measured by DSC.

[0054] Compared to compositions with curing temperatures above 200°C, curable preform compositions with onset and peak curing temperatures within the aforementioned range exhibit broadened heat release properties over a longer period. Curable preform compositions with the aforementioned onset and peak temperature ranges allow for rapid curing, e.g., achieving 75% or higher degree of cure within 5 minutes. In SMC molding applications, a curing time of 3 to 5 minutes is considered desirable.

[0055] Cured preform composition

[0056] This disclosure generally relates to cured preform compositions of curable preform compositions. The cured preform compositions can be prepared by subjecting the curable preform composition to curing conditions, which may include subjecting the curable preform composition to elevated temperatures and elevated pressures.

[0057] Cured preform compositions can be produced using methods and equipment known in the art, such as compression molding, injection molding, vacuum bagging, and autoclave or oven curing.

[0058] In one or more embodiments, the cured preform composition has a V-0 flammability rating, as measured according to the UL94 vertical flammability test. V-0 is the lowest flammability rating according to the UL94 test. To achieve a V-0 rating, the sample must not burn for 10 seconds or longer after being exposed to a flame twice at 10-second intervals. Furthermore, the total burning time of 10 samples must be less than 50 seconds.

[0059] In one or more embodiments, when the composition is tested according to the UL94 vertical flammability test, the char formed by the cured preform composition exhibits low char brittleness. A char with "low char brittleness" refers to a char that does not have a weak outer layer that is easily deformable under pressure or stress. The brittleness of the char can be determined by measuring the Shore hardness of the cured preform composition subjected to the flammability test. The brittleness of the char can also be determined by indentation hardness testing and / or by three-point bending testing.

[0060] In one or more embodiments, when the curable preform composition is cured at 180°C for 5 minutes to produce a cured preform composition, the cured preform composition has a degree of curing of at least 75%.

[0061] Method for producing curable preform compositions

[0062] This disclosure generally relates to a method for producing a curable preform composition. In one or more embodiments, the method includes mixing 100 parts of a curable resin, 0.15 to 5 parts by weight of a first catalyst, 75 parts or less of a flame retardant (FR) agent and fiber reinforcement to produce an uncured curable preform composition, and curing the uncured curable preform composition to produce a curable preform composition. The curable resin composition produced by this method may include at least 15 parts by weight of benzoxazine resin in the 100 parts by weight of curable resin contained in the curable resin composition (at least 15 wt% of the curable resin is benzoxazine resin based on the total amount of curable resin in the curable preform composition by weight).

[0063] In one or more embodiments, the method includes mixing a curable resin, a first catalyst, a FR agent, and a fiber reinforcement to produce an uncured curable preform composition. The amounts of the curable resin, first catalyst, FR agent, and fiber reinforcement in the mixing step may be as previously described for curable resin compositions. The mixing of the above components may be performed simultaneously or sequentially.

[0064] Figure 1 This is a flowchart of a method for producing a curable preform composition, wherein the components are mixed sequentially. At 100, the curable resin is heated to reduce its viscosity. At 102, a first catalyst is dissolved in a solvent. At 104, the curable resin dissolved in the solvent and the first catalyst are blended to produce a solvated first mixture. At 106, the solvent is removed from the solvated first mixture to produce a first mixture. At 108, a fiber reinforcement agent is blended with the first mixture to produce an unreinforced resin mixture (curable resin composition). Other components, such as at least one second catalyst, thickener, and filler, may be added via the blending step of the FR agent. At 110, a fiber reinforcement is blended with the unreinforced resin mixture to produce an uncured curable preform composition. At 112, the uncured curable preform composition is cured to produce a curable preform composition.

[0065] Figure 2This is a flowchart of a method for producing a curable preform composition, wherein the components are mixed sequentially, and the curable resin includes a first curable resin and at least one second curable resin. At 200, the first curable resin is heated to reduce its viscosity. At 202, a first catalyst is dissolved in a solvent. At 204, the first curable resin dissolved in the solvent and the first catalyst are blended to produce a solvated first mixture. At 206, the solvent is removed from the solvated first mixture to produce the first mixture. At 208, the first mixture and at least one second curable resin are combined by a method such as mixing or blending to produce a second mixture. At 210, a fiber reinforcement agent is blended with the second mixture to produce an unreinforced resin mixture (curable resin composition). Other components, such as at least one second catalyst, thickener, and filler, may be added via the blending step of the FR agent. At 212, a fiber reinforcement is blended with the unreinforced resin mixture to produce an uncured curable preform composition. At 214, the uncured curable preform composition is cured to produce a curable preform composition.

[0066] Figure 3 This is a flowchart of a method for producing a curable preform composition, wherein the components are mixed sequentially, and the curable resin includes a first curable resin and may further include at least one second curable resin. At 300, the first curable resin is heated to reduce its viscosity. At 302, a first catalyst is added to the heated curable resin by melt mixing to produce a first mixture. The addition of the first catalyst to the heated curable resin can be carried out by dispersing the first catalyst in the heated curable resin. Dispersion may include refining the first catalyst and the heated curable resin by shear force to make the first mixture homogeneous. At 304 (which is an optional step), the first mixture and at least one second curable resin are combined by mixing or blending to produce a second mixture. If the composition does not contain at least one second curable resin and step 304 is omitted, the first mixture from step 302 may be considered the second mixture. At 306, an FR agent is blended with the second mixture to produce an unreinforced resin mixture. Other components, such as at least one second catalyst, thickener, and filler, may be added via the blending step of the FR agent. At point 308, the fiber reinforcement is blended with an unreinforced resin mixture to produce an uncured curable preform composition. At point 310, the uncured curable preform composition is cured to produce a curable preform composition.

[0067] In one or more embodiments, the method includes heating the curable resin (steps 100, 200, and 300). The heating temperature may be determined based on the properties of the curable resin, such as its viscosity. In one or more embodiments, the heating of the curable resin is performed at a temperature in the range of about 80°C to about 85°C.

[0068] In one or more embodiments in which the mixing of components is carried out sequentially, the method includes blending a curable resin and a first catalyst to produce a solvated first mixture (step 104, step 204) or a first mixture (step 302). The first curable resin may be a benzoxazine resin. The first catalyst may be lithium iodide. The first catalyst may be dissolved in a solvent prior to mixing with the curable resin (step 102, step 202). Exemplary solvents for dissolving the first catalyst may include acetone and ethyl acetate. In one or more embodiments, the first catalyst is not dissolved in a solvent and is directly blended with the curable resin to produce the first mixture, thereby omitting the step of dissolving the first catalyst in the solvent (step 102, step 202).

[0069] In one or more embodiments, the blending of the curable resin and the first catalyst is carried out at room temperature or at an elevated temperature. The elevated temperature can be provided by active heating (e.g., a heated mixer). In one or more embodiments, as described in the preceding section, the elevated temperature is provided due to the curable resin being heated prior to the blending step, or due to the heat generated by shearing the curable resin and the first catalyst during blending.

[0070] In one or more embodiments, the method includes removing a significant amount of solvent from a solvated first mixture to produce a first mixture (steps 106, 206). "Significant amount" of solvent means at least 80% by weight, at least 85% by weight, at least 90% by weight, at least 95% by weight, at least 99% by weight, at least 99.9% by weight, or 100% by weight of solvent, based on the total amount of solvent present in the mixture. Solvent removal can be performed by methods known in the art, such as placing the mixture under vacuum. Solvent removal from the solvated first mixture can be performed at room temperature or at elevated temperatures, for example, in the range of about 30 to 60°C. The duration of the solvent removal step can be adjusted according to the requirements of one or more embodiments. The duration can range from about 45 minutes to about 60 minutes. In one or more embodiments in which the first catalyst is insoluble in the solvent, the solvent removal step (steps 106, 206) is omitted.

[0071] In one or more embodiments where the curable resin includes a first curable resin and at least one second curable resin, such as unsaturated polyester resin and / or phenolic resin, the method includes combining at least one second curable resin and a first mixture to produce a second mixture (steps 208, 304). Combining can be performed by mixing or blending at least one second curable resin and the first mixture. Combining can be performed at room temperature or at an elevated temperature. The elevated temperature can be provided by active heating, such as a mixer with heating capabilities. In one or more embodiments, the elevated temperature is provided due to heating the first mixture prior to the combination step, or due to heat generated by combining at least the second curable resin and the first mixture. In one or more embodiments, at least one second curable resin can be combined with the first curable resin before adding the first catalyst. In this case, the blending step of the first curable resin and the first catalyst will include at least the second curable resin.

[0072] In one or more embodiments, the method includes blending a flame retardant (FR) agent and a fiber reinforcement with a first mixture or a second mixture to produce an uncured curable preform composition. The blending of the FR agent and the fiber reinforcement may be performed simultaneously or sequentially. In one or more embodiments in which the FR agent and the fiber reinforcement are blended sequentially, the method may include blending the FR agent to produce an unreinforced resin mixture, which may also be referred to as a curable resin composition (steps 108, 210, 306), and then blending the fiber reinforcement and the unreinforced resin mixture (steps 110, 212, 308). The blending of the fiber reinforcement and the unreinforced resin mixture may be performed at room temperature or at elevated temperatures, for example in the temperature range of about 40°C to about 100°C, to promote impregnation of the mixture into the fiber reinforcement. The blending of the fiber reinforcement and the unreinforced resin mixture may be performed by adding the fiber reinforcement and the unreinforced resin mixture, heating to an elevated temperature, and simultaneously or sequentially blending the fiber reinforcement and the unreinforced mixture.

[0073] Mixing, blending, combining, and blending steps can be performed using any suitable equipment known in the art.

[0074] In one or more embodiments in which the components are mixed sequentially, the fiber reinforcement is blended with a resin mixture (which may be an unreinforced resin mixture, a first resin mixture, or a second resin mixture) to produce an uncured, curable preform composition as follows: Figure 4The process is carried out in a continuous manner. A resin mixture is placed in a "doctor box," and a carrier membrane passes beneath the doctor box to transfer a predetermined amount of resin onto the carrier membrane to create a first resin layer. The resin mixture on the carrier membrane can have a specific thickness / area weight. The doctor box is designed to contain the resin and has features to regulate the amount of resin dispensed onto the carrier membrane. The fiber reinforcement can be provided in continuous form (continuous roving) and can then be fed through a chopped strand machine to cut it into short strands of fibers with a predetermined length. The chopped fiber reinforcement can then be placed on the first resin layer.

[0075] like Figure 4 As shown, the second resin layer can be produced by dispensing a resin mixture onto a carrier membrane in a manner similar to that of the first resin layer. The first resin layer, containing chopped fiber reinforcement, is in contact with the second resin layer, such that the fiber reinforcement is sandwiched between the first and second resin layers. The first and second resin layers and the fiber reinforcement can then be blended under elevated pressure and temperature via an impregnation process, such as at least one set of compaction rollers, to produce an uncured curable preform composition. The uncured curable preform composition can be provided in continuous sheet form or a “laminate,” which can then undergo a curing process.

[0076] Suitable carrier films known in the art can be used in continuous blending processes. Examples of carrier films may include polymer-based release films, which may or may not have a release coating, and release paper.

[0077] The fiber reinforcement may be partially or completely impregnated with a resin mixture. The first and second resin layers may have the same thickness / weight-per-unit area, or they may have different thicknesses / weight-per-unit area. In one or more embodiments, the continuous blending process may include only the first resin layer to provide the resin mixture. In such a configuration, a resin-free second carrier film may be provided prior to the impregnation process, thereby preventing resin transfer onto machine parts.

[0078] In one or more embodiments, the method further includes mixing at least one second catalyst. The method may include mixing one or more second catalysts. The type and amount of the second catalyst may be as previously described for curable resin compositions. Where the mixing of components is carried out sequentially, the mixing of the second catalyst may be performed after a solvent removal process (if the solvent is used to dissolve the first catalyst), after blending the first catalyst and the curable resin (if no solvent is used to dissolve the first catalyst), or after a combination of the first mixture and at least one second curable resin. In one or more embodiments, the mixing of the second catalyst may be performed simultaneously with the blending of the FR agent and / or fiber reinforcement, or separately.

[0079] In one or more embodiments, the method further includes mixing fillers. The type and amount of filler may be as previously described for curable preform compositions. Where the mixing of components is carried out sequentially, the filler mixing may be performed after a solvent removal process (if the solvent is used to dissolve the first catalyst), after blending the first catalyst and the curable resin (if no solvent is used to dissolve the first catalyst), or after a combination of the first mixture and at least one second curable resin. In one or more embodiments, the filler mixing may be performed simultaneously with the mixing of the FR agent and / or fiber reinforcement, or separately.

[0080] In one or more embodiments, the method includes curing an uncured curable preform composition to produce a curable preform composition (steps 112, 214, and 310). A curable preform composition prepared by curing an uncured curable preform composition may also be referred to as a cured curable preform composition.

[0081] In one or more embodiments, the curing process includes adding a thickener to the uncured curable preform composition and subjecting the uncured curable preform composition to a temperature-controlled environment. The type and amount of thickener added during curing may be as previously described for the curable preform composition. The addition of the thickener may be carried out together with the mixing of the curable resin, the first catalyst, the FR agent, and the fiber reinforcement, or after the mixing step. When the components are mixed sequentially, the addition of the thickener may be carried out after the solvent removal process (if the solvent is used to dissolve the first catalyst), after blending the first catalyst and the curable resin (if no solvent is used to dissolve the first catalyst), or after combining the first mixture and at least one second curable resin. In one or more embodiments, the addition of the thickener may be carried out simultaneously with the blending of the FR agent and / or the fiber reinforcement, or separately.

[0082] The addition of thickeners and the subjecting of the uncured curable preform composition to a temperature-controlled environment can be carried out separately or simultaneously.

[0083] The temperature of the temperature-controlled environment can be maintained within the range of approximately 25 to approximately 40°C. The temperature of the temperature-controlled environment can be controlled so that temperature variations are less than approximately 5°C.

[0084] The uncured curable preform composition can be subjected to a temperature-controlled environment for at least 1 day. In one or more embodiments, the uncured curable preform composition can be subjected to a temperature-controlled environment for a duration ranging from about 1 day to about 10 weeks, for example, from the lower limit of any one of 1 day, 2 days, 3 days, 4 days and 5 days to the upper limit of any one of 1 week, 2 weeks, 5 weeks and 10 weeks, wherein any lower limit can be paired with any upper limit.

[0085] In one or more embodiments, the curing process includes subjecting the uncured curable preform composition to an elevated temperature to slightly increase the degree of curing of the uncured curable preform to increase viscosity. "Elevated temperature" refers to a temperature in the range of about 30 to about 100°C. The uncured curable preform composition may be subjected to the elevated temperature for a duration of about 1 to 9 hours.

[0086] In one or more embodiments, the dynamic viscosity of the unreinforced resin mixture at 85°C, as measured by a rotational rheometer, is 15 Pa·s or less, for example, in the range of about 1 to about 15 Pa·s. In one or more embodiments, the uncured curable preform composition has a temperature of 85°C or lower, for example, in the range of about 20 to 85°C, at which temperature the uncured curable preform composition has a viscosity of 15 Pa·s or less.

[0087] In one or more embodiments, the dynamic viscosity of the unreinforced resin mixture at 100°C, as measured by a rotational rheometer, is 1 Pa·s or less. In one or more embodiments, the uncured curable preform composition has a temperature of 100°C or lower, for example in the range of about 75 to 100°C, at which temperature the uncured curable preform composition has a viscosity of 1 Pa·s or less.

[0088] Unreinforced resin mixtures with viscosities within the above range allow the fiber reinforcements to be fully impregnated at room temperature.

[0089] Method for producing cured preform compositions

[0090] This disclosure generally relates to a method for producing a cured preform composition. In one or more embodiments, the method includes curing a curable resin composition at elevated temperatures and elevated pressures. Curing of the curable resin composition may be carried out at elevated temperatures ranging from about 150 to about 220°C and at elevated pressures ranging from about 700 to about 1000 psi (4.8 to 7 MPa).

[0091] The curing step can last for 500 minutes or less, 400 minutes or less, 300 minutes or less, 200 minutes or less, 100 minutes or less, 90 minutes or less, 80 minutes or less, 70 minutes or less, 60 minutes or less, 50 minutes or less, 40 minutes or less, 30 minutes or less, 20 minutes or less, 10 minutes or less, 5 minutes or less, 4 minutes or less, 3 minutes or less, 2 minutes or less, or 1 minute or less. The curing step can last for a duration ranging from approximately 1 minute to approximately 500 minutes, for example, from a lower limit selected from any of 1, 2, 3, 4, and 5 minutes to an upper limit selected from any of 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, and 500 minutes, where any lower limit can be paired with any mathematically compatible upper limit.

[0092] The curing step can be carried out by methods known in the art, such as compression molding, injection molding, vacuum bagging, and autoclave or oven curing.

[0093] Example

[0094] The following examples are provided to illustrate implementation of this disclosure. These examples are not intended to limit the scope of the invention, and they should not be interpreted as such.

[0095] Exemplary curable preform compositions, Examples 1-13 (EX 1-13), and a preform composition not containing benzoxazine resin, Comparative Example 1 (CE 1), were produced by first mixing the components shown in Tables 2-1, 2-2, and 2-3 to produce an uncured curable preform composition.

[0096] Table 1 provides descriptions of the components and chemicals / materials represented by alphanumeric codes in Tables 2-1, 2-2, and 2-3. Catalyst C1 is the catalyst for resin A1, catalyst C2 is the catalyst for resin A2, and catalysts C3 and C4 are the catalysts for resin A3. Catalyst C1 represents the first catalyst, and catalysts C2, C3, and C4 represent the second catalysts.

[0097] [Table 1]

[0098]

[0099] [Table 2-1]

[0100]

[0101] [Table 2-2]

[0102]

[0103] [Table 2-3]

[0104]

[0105] Examples 1-13 were prepared by placing a semi-solid benzoxazine resin in a disposable cup and then placing the cup containing the benzoxazine resin in an oven at 80-85°C until the resin became liquid. The size of the disposable cup was chosen so that it could be placed in a Thinky mixer (purchased from Thinky USA, Inc.).

[0106] For the examples containing phenolic resin (Examples 3 and 7), the phenolic resin (solid phenolic varnish phenolic resin) was heated to a temperature of 80 to 100°C to soften and melt, and mixed with benzoxazine resin in a Thinky mixer, followed by the addition of a lithium iodide catalyst. Lithium iodide (LiI) was dissolved in acetone and mixed with benzoxazine resin or a benzoxazine / phenolic resin blend at 2000 rpm for 2 minutes in a Thinky mixer while the mixture was hot, to produce a solvated first mixture.

[0107] The solvated first mixture is placed in a temperature-controlled vacuum oven at 50°C and the solvent is removed for 45 to 60 minutes, or until all solvent is removed to produce the first mixture.

[0108] For the embodiments containing unsaturated polyester (Examples 2, 4-13), the unsaturated polyester was added to the first mixture and blended in a Thinky mixer at 2000 rpm for 3 minutes while the resin was still warm to produce the second mixture.

[0109] For the embodiments that include a flame retardant (aluminum hydroxide), additional catalysts (hexamethylenetetramine (HMTA), tert-butylperoxy-2-ethylhexyl ester (TBEC), azobisisobutyronitrile (AIBN)) and thickeners (magnesium oxide, pyrolytic silica), the corresponding flame retardant, catalyst and thickener are added to the first mixture (for Examples 1 and 3) or the second mixture (for Examples 2, 4-13) and blended in a Thinky mixer at 2000 rpm for 3 minutes or until homogeneous to obtain an unreinforced resin mixture.

[0110] Fiber reinforcement was added to the unreinforced resin mixture, and the unreinforced resin mixture and fiber reinforcement were placed in a temperature-controlled oven at 80°C for 2 minutes to improve fiber impregnation. The unreinforced resin mixture and fiber reinforcement were then manually mixed with a rod to produce an uncured, curable preform composition.

[0111] The uncured curable preform composition is placed in a silicone mold made of a high-temperature silicone rubber sheet with a Shore hardness of 60A to prepare for curing. The mold dimensions are 135 mm × 20 mm × 3 mm. The mold is used to produce samples that do not require cutting or trimming. The mold containing the uncured curable preform composition is placed in a temperature-controlled oven at 80°C for 2.5 hours to produce a cured curable preform composition with the desired spreadability and tackiness. The mold containing the composition is removed from the oven and allowed to cool to room temperature before being removed from the mold.

[0112] The production of Comparative Example 1 was carried out in the same manner as in Examples 1-13, except that the heating of the benzoxazine resin, the blending of the benzoxazine resin and LiI, and the removal of the solvent were not performed.

[0113] Properties - Uncured preform composition

[0114] The various physical properties of the curable preform compositions of Examples 1-13 and Comparative Example 1 were measured as follows.

[0115] Before the addition of fiber reinforcement (the unreinforced resin mixture of each embodiment), the dynamic viscosity of each embodiment was measured using a TA Instruments Discovery mixed rotating parallel plate rheometer. The parallel plates were 25.0 mm in diameter and made of ETC aluminum. The plate spacing was set to 1000 micrometers. Tests were conducted at onset and end temperatures of 25°C and 280°C, a heating rate of 5.0°C / min, a sampling interval of 1.0 s / pt (single point), a strain of 0.01%, a frequency of 1.0 Hz, a soak time of 0.0 s, and a post-heating soak time of 0.0 s. From the dynamic viscosity tests, the temperature at which the uncured preform composition without fiber reinforcement exhibited a viscosity of 15 Pa·s was obtained.

[0116] The cured Examples 1-12 and Comparative Example 1 were confirmed to be layable and easy to cut and carry by touching the cured samples to confirm their appropriate flexibility.

[0117] The physical properties of the uncured preform compositions of Examples 1-13 (EX 1-13) and Comparative Example 1 (CE 1) are summarized in Tables 3-1 and 3-2.

[0118] [Table 3-1]

[0119]

[0120] Measure the dynamic viscosity before adding chopped glass fibers.

[0121] [Table 3-2]

[0122]

[0123] Measure the dynamic viscosity before adding chopped glass fibers.

[0124] [Table 3-3]

[0125]

[0126] The results in Tables 3-1, 3-2 and 3-3 indicate that the curable preform compositions of Examples 1-12 provide acceptable layability during curing, demonstrating that the preform compositions can lay up to the desired mold shape or geometry without wrinkling or forming defects during the curing process of the preform compositions.

[0127] The results further show that, at temperatures of 26–84°C, the uncured samples (unreinforced resin mixtures, curable resin compositions) without fiber reinforcement as described in Examples 1–12 exhibited a viscosity of 15 Pa·s or lower.

[0128] Properties - Curing Preform Composition

[0129] Test samples of cured preform compositions were prepared from the curable preform compositions of Examples 1-12 and Comparative Example 1 to evaluate the flame retardant properties of the compositions.

[0130] The flammability of the cured preform composition was evaluated according to the UL 94 flammability test method. Samples of the cured preform composition were prepared as follows. The cured uncured preform compositions of Examples 1-12 and Comparative Example 1 were placed in a press at 5 MPa. The composition was kept under pressure until the end of the curing cycle. The press was heated from room temperature to 150°C at a heating rate of 8°C / min. The temperature was held at 150°C for 15 minutes, then increased to 180°C at a heating rate of 8°C / min. The temperature was held at 180°C for 30 minutes, then increased to 220°C at a heating rate of 8°C / min. The temperature was held at 220°C for 60 minutes for post-curing of the composition. The temperature was then reduced to room temperature, at which point the curing cycle was complete, and the composition was depressurized. The cured preform composition was removed from the mold and precision-saved to dimensions of 125 mm × 13 mm × 3 mm. The cut samples were placed in a vacuum oven set at 100°C to remove residual water from the cutting operation. The samples were removed from the oven and cooled to room temperature before flammability testing was performed. Ten samples were prepared for each of Examples 1-12 and Comparative Example 1.

[0131] According to the UL 94 flammability test method, the flammability test is performed as follows: The sample is placed vertically between two clamps in a position such that the distance between the bottom of the sample and the top of the butane torch is approximately 10 mm. The torch flame length is set to 20 mm, so that the top 10 mm of the flame will be in contact with the sample. The flame is applied to the sample for 10 seconds, and then removed. The time required for the flame to self-extinguish is recorded. The flame is again applied to the sample for 10 seconds, and then removed. The flame extinguishing time is recorded again.

[0132] After the samples were removed and cooled, the char brittleness of the char formed on the samples used for flammability testing was assessed based on the ease with which the char formed could be scraped off. Samples with easily scraped-off char were given a "high" char brittleness rating, while samples with difficult-to-scrape-off char were given a "low" char brittleness rating. The burn height and any defects that might be present in the samples were also recorded.

[0133] The Tg of the cured preform composition is determined by DMA using an analyzer such as the Q800DMA (available from TA Instruments), where parameters include, for example, a temperature range of 25°C to 350°C, a heating rate of 5°C / min, a frequency of 1 Hz, and an amplitude of 10 micrometers.

[0134] The properties of the cured preform compositions of Examples 1-12 (EX 1-12) and Comparative Example 1 (CE 1) are summarized in Tables 4-1, 4-2 and 4-3.

[0135] [Table 4-1]

[0136]

[0137] [Table 4-2]

[0138]

[0139] [Table 4-3]

[0140]

[0141] The results in Tables 4-1, 4-2 and 4-3 show that Examples 1-12 meet the requirements of the UL94 V-0 rating while providing low carbide brittleness, indicating improved FR performance compared to Comparative Example 1, which has high carbide brittleness.

[0142] Although only a few exemplary embodiments have been described in detail above, those skilled in the art will readily understand that many modifications can be made to the exemplary embodiments without substantially departing from the invention. Therefore, all such modifications are intended to be included within the scope of this disclosure as defined by the following claims. In the claims, the device plus function clause is intended to cover structures described herein as performing said functions, and includes not only structural equivalents but also equivalent structures. Thus, although nails and screws may not be structural equivalents because nails use a cylindrical surface to hold wooden parts together while screws use a helical surface, nails and screws can be equivalent structures in the context of fastening wooden parts.

Claims

1. A curable resin composition comprising: 100 parts by weight of curable resin; 0.1 to 5 parts by weight of a first catalyst, which is lithium iodide; and 75 parts by weight or less of flame retardant, in, Of 100 parts by weight of curable resin, at least 5 parts by weight are benzoxazine resin.

2. The curable resin composition according to claim 1, wherein the curable resin further comprises at least one of phenolic resin and unsaturated polyester resin.

3. The curable resin composition according to claim 1 or 2, further comprising a second catalyst.

4. The curable resin composition according to any one of the preceding claims, wherein the flame retardant comprises aluminum hydroxide.

5. The curable resin composition according to any one of the preceding claims further comprises at least one of a thickener and a filler.

6. The curable resin composition according to any one of the preceding claims, comprising at least one of the following: The initial curing temperature of 180°C or lower, as measured by DSC, and Peak curing temperature of 220°C or lower, as measured by DSC.

7. The curable resin composition according to any one of the preceding claims has a dynamic viscosity of 15 Pa·s or less at 85°C, as measured by a rotational rheometer.

8. The curable resin composition according to any one of the preceding claims, when subjected to a curing process, has a dynamic viscosity in the range of 20,000 to 100,000 Pa·s at room temperature, as measured by a rotational rheometer.

9. A curable preform composition comprising: A curable resin composition comprising: 100 parts by weight of curable resin; 0.1 to 5 parts by weight of a first catalyst, which is lithium iodide; and 75 parts by weight or less of flame retardant; and Fiber reinforcement, in, Of 100 parts by weight of curable resin, at least 5 parts by weight are benzoxazine resin.

10. The curable preform composition according to claim 9, wherein the amount of the fiber reinforcement in the curable preform composition is in the range of 1 to 60 parts by weight, based on 100 parts by weight of the curable resin.

11. The curable preform according to claim 9 or 10, wherein the curable resin composition is layable.

12. The curable preform composition according to any one of claims 9 to 11, having a resin flow rate of 20% or less as measured according to ASTM D3531.

13. The cured preform composition according to any one of claims 9 to 12.

14. The cured preform composition according to claim 13, having a flammability rating of V-0 as measured according to the UL94 vertical flammability test.

15. The cured preform composition according to claim 13 or 14, wherein the char formed by the cured preform composition has low char brittleness when tested according to the UL94 vertical flammability test.

16. The cured preform composition according to any one of claims 13 to 15, wherein the cured preform composition has a degree of curing of at least 75% when cured at 180°C for 5 minutes.

17. A method for producing a curable preform composition, comprising: Mix 100 parts of curable resin, 0.15 to 5 parts by weight of a first catalyst, 75 parts or less of a flame retardant, and fiber reinforcement to produce an uncured curable preform composition. and The uncured curable preform composition is cured to produce the curable preform composition. Of the 100 parts by weight of curable resin, at least 5 parts by weight are benzoxazine resin, and The first catalyst is lithium iodide.

18. The method of claim 17, wherein the mixture of the curable resin, the first catalyst, the flame retardant, and the fiber reinforcement comprises: Heating the curable resin; The first catalyst is dissolved in a solvent; The curable resin and the first catalyst are blended to produce a solvated first mixture; The solvent is substantially removed from the solvated first mixture to produce the first mixture; and The first mixture, the flame retardant, and the fiber reinforcement are blended to produce the uncured curable preform composition.

19. The method according to claim 17, The curable resin comprises a first curable resin and at least one second curable resin, and The mixture of the curable resin, the first catalyst, the flame retardant, and the fiber reinforcement comprises: Heat the first curable resin; The first catalyst is dissolved in a solvent; The first curable resin and the first catalyst are blended to produce a solvated first mixture; The solvent is substantially removed from the solvated first mixture to produce the first mixture; The first mixture and the at least one second curable resin are combined to produce a second mixture; and The second mixture, the flame retardant, and the fiber reinforcement are blended to produce the uncured curable preform composition.

20. The method of claim 17, wherein the mixture of the curable resin, the first catalyst, the flame retardant, and the fiber reinforcement comprises: Heating the curable resin; The first catalyst is dispersed in a heated curable resin by melt mixing to produce a first mixture; and The first mixture, the flame retardant, and the fiber reinforcement are blended to produce the uncured curable preform composition.

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