Flame retardant resins and composite preforms

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 which is lithium iodide, and 75 parts or less by weight of a fire retardant agent. A curable preform composition includes a 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 out of the 100 parts by weight of the curable resin. A method for producing 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 fire retardant agent, and a fiber reinforcement, to produce an unmatured curable preform composition, and maturing the unmatured curable preform composition to produce the curable preform composition.

Description

FLAME RETARDANT RESINS AND COMPOSITE PREFORMSBACKGROUND

[0001] A sheet molding compound (SMC) is a reinforced moldable compound often used in the production of compression molded articles. SMC generally includes a resin composition and fiber reinforcement. Unsaturated polyester (UPE) is widely used as the resin composition of SMC. However, UPE has poor flame retardancy and therefore, a substantially large amount of fire retardant (FR) agents must be added when the application has fire retardancy requirements. An SMC with a substantial amount of FR agents usually result in formation of highly brittle char, which negatively affects its mechanical properties. Furthermore, some types of FR agents, such as phosphorus additives, may produce toxic smoke upon combustion.

[0002] Other types of resin composition are not widely used for SMC due to technical difficulties, such as balancing of fast cure, viscosity control and drapability of SMC. Accordingly, there exists a need for continuing improvement of a reinforced moldable compound including SMC.SUMMARY

[0003] This summary is provided to introduce a selection of concepts further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.

[0004] In one aspect, embodiments disclosed herein relate to a curable resin composition. The curable resin composition includes 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 or less by weight of a fire retardant agent. At least 5 parts by weight of the curable resin is a benzoxazine resin out of the 100 parts by weight of the curable resin.

[0005] In another aspect, embodiments disclosed herein relate to a curable preform composition. The curable preform composition includes a curable resin composition and a fiber reinforcement. The curable resin composition includes 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 or less by weight of a fire retardant agent. At least 5 parts by weight ofthe curable resin in the curable preform composition is a benzoxazine resin out of the 100 parts by weight of the curable resin.

[0006] In another aspect, embodiments disclosed herein relate to a method for producing a curable preform composition. 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 fire retardant agent, and a fiber reinforcement, to produce an unmatured curable preform composition, and maturing the unmatured curable preform composition to produce the curable preform composition. At least 5 parts by weight of the curable resin in the curable preform composition is a benzoxazine resin out of the 100 parts by weight of the curable 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.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 is a flow diagram of a method for producing a curable preform composition in accordance with one or more embodiments.

[0009] FIG. 2 is a flow diagram of a method for producing a curable preform composition in accordance with one or more embodiments.

[0010] FIG. 3 is a flow diagram of a method for producing a curable preform composition in accordance with one or more embodiments.

[0011] FIG. 4 illustrates admixing of a fiber reinforcement and unreinforced resin mixture in accordance with one or more embodiments.DETAIEED DESCRIPTION

[0012] The present disclosure generally relates to a curable resin composition and a curable preform composition. The curable resin composition includes a curable resin, a first catalyst, and a fire retardant (FR) agent. The curable preform composition includes a curable resin composition, which includes a curable resin, a first catalyst, an FR agent, and a fiber reinforcement. A “preform” (“preform composition,” “composite preform”) refers to a composition that includes a formulated resin composition and fiber reinforcement. A specific form of the preform is not limited,but may include a solid, a semi- solid, and a paste form. The curable preform composition may be a sheet molding compound (SMC).CURABLE RESIN COMPOSITION

[0013] In one or more embodiments, the curable resin composition includes a curable resin. The curable resin may include a benzoxazine resin. Benzoxazine resins generally contain a substantial amount of nitrogen, which may act as an inherent flame retardant. Furthermore, benzoxazine resins tend to char, which reduces the formation of volatile compounds, further contributing to the fire retardancy of the composition. In one or more embodiments, the benzoxazine resin may be any of the benzoxazine component as disclosed in U.S. Pub. No. 2017 / 0183450 Al, hereby incorporated by reference.

[0014] In one or more embodiments, the benzoxazine resin includes at least one benzoxazine (BZ) group therein (along the backbone or in an end-cap), or it 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 benzoxazine -based resin or BZ monomer may have a structure represented by formula (I), which may be referred to as monofunctional BZ:

[0015] R1 may represent one or more of a hydrogen atom, a hydrocarbon group, a substituted hydrocarbon group, and a functional group. The BZ groups of one or more embodiments may include one or more substituents represented by Rl. As used throughout this description, the term “hydrocarbon group” may refer to branched, straight-chain, and / or ring-containing hydrocarbon groups, which may be saturated or unsaturated. The hydrocarbon groups may be primary, secondary, and / or tertiary hydrocarbons. As used throughout this description, the term “substituted hydrocarbon group” may refer to a hydrocarbon group (as defined above) where at least one hydrogen atom is replaced with a non-hydrogen group that results in a stable compound. Such substituents may be groups selected from (but are not limited to) halo, hydroxyl, alkoxy, oxo, alkanoyl, aryloxy, alkanoyloxy, amino, alkylamino,arylamino, arylalkylamino, disubstituted amines, alkanylamino, aroylamino, aralkanoylamino, substituted alkanoylamino, substituted arylamino, aubstituted aralkanoylamino, thiol, alkylthio, arylthio, arylalkylthio, alkylthiono, arylthiono, aryalkylthiono, alkylsulfonyl, arylsulfonyl, arylalkylsulfonyl, sulfonamide, substituted sulfonamide, nitro, cyano, carboxy, carbamyl, alkoxycarbonyl, aryl, substituted aryl, guanidine, vinyl, acetylene, acrylate, cyanate, epoxide, and heterocyclic groups, and mixtures thereof. The functional groups may be groups selected from (but are not limited to) halo, hydroxyl, alkoxy, oxo, amino, amido, thiol, alkylthio, sulfonyl, alkylsulfonyl, sulfonamide, substituted sulfonamide, nitro, cyano, carboxy, carbamyl, alkoxycarbonyl vinyl, acetylene, acrylate, cyanate, epoxide groups, and mixtures thereof.

[0016] R2 is not particularly limited and may represent any of the groups mentioned with regard to Rl. However, in particular embodiments, R2 may be a BZ-containing moiety. When R2 is a BZ-containing moiety, the benzoxazine resin may include bis- BZ units. The bis-BZ units may have a structure represented by formula (II), which may be referred to as di- amine type BZ:

[0017] Rl represents a group as discussed above with regard to formula (I). Rl' may be a group that is the same as, or different from, Rl. R3 may represent a hydrocarbon group or a substituted hydrocarbon group. In particular embodiments, 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 substituted variants thereof. In one or more embodiments, R3 may represent a group having a molecular weight in a range of about 14 to 100,000 Da, or 14 to 10,000 Da, or 14 to 1,000 Da.

[0018] In one or more embodiments, the benzoxazine resin has the structure as shown in Formula (III), which may be referred to as di- phenol type BZ:

[0019] Rl, and Rl' in Formula (III) represent a group equivalent to R2 in Formula (I) as discussed above. R3 represents a group as discussed above regarding Formula (II).

[0020] In one or more embodiments, the benzoxazine resin may be main-chain type benzoxazine polymers (MCBPs). MCBPs may have BZ as part of the repeating units. In one or more embodiments, the benzoxazine resin may be main-chain type benzoxazine oligomers (MCBOs). MCBOs may be similar to MBCPs in terms of the chemical structure, with benzoxazine being part of the repeating unit in the backbone.

[0021] In one or more embodiments, the benzoxazine resin may be a polymer formed from the reaction between a bis-benzoxazine monomer and a bifunctional comonomer having phenol, amine, and / or thiol functional groups, and the polymer contains at least one endcap that is a crosslinkable group.

[0022] In one or more embodiments, at least 5 parts by weight of the curable resin out of 100 parts by weight of the curable resin included in the curable resin composition, and / or curable preform composition is benzoxazine resin (at least 5 wt% of the curable resin is benzoxazine resin, based on the total amount of curable resin by weight in the curable resin composition and / or curable preform composition). 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, out of 100 parts by weight of the curable resin included in the curable resin composition and / or curable preform composition (benzoxazine resin is included in the curable resin in an amount of about 5 to 100 wt % based on the total amount curable resin by weight in the curable resin composition and / or curable perform composition). In one or more embodiments, benzoxazine resin is included in the curable resin in an amount in a range of 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, out of 100 parts by weight of the curable resin, where any lower limit may be paired with any upper limit.

[0023] The curable resin may also include unsaturated polyester resin, phenolic resin, vinyl ester resin, epoxy resin, and combinations thereof.

[0024] The curable resin may include one type of resin, such as benzoxazine resin, as a 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 the at least one second curable resin.

[0025] In one or more embodiments, the curable resin composition includes a first catalyst. The first catalyst may include lithium iodide (Lil). Lil may cure a benzoxazine resin via a ring-opening polymerization reaction. The amount of the first catalyst in the curable resin composition may be in a range of from about 0.1 to about 5 parts by weight, based on 100 parts by weight of a curable resin. In one or more embodiments, the amount of the first catalyst in the curable resin composition is in a range of 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, based on 100 parts by weight of the curable resin, where any lower limit may be paired with any upper limit.

[0026] In one or more embodiments, the curable resin composition includes a second catalyst. The second catalyst may be a catalyst that cures benzoxazine resin, a catalyst for other curable resins included in the composition, such as phenolic or unsaturated polyester resins, or may be 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 salt, amidine compounds, methyl ethyl ketone peroxide (MEKP), benzyl peroxide (BPO), acetylacetone peroxide (AAP), organic peroxides, acid catalysts (sulfuric acid, oxalic acid, hydrochloric acid), anhydrides, phenols, and combinations thereof.

[0027] The amount of the second catalyst in the curable resin composition may be in a range of from about 0.1 to about 5 parts by weight, based on 100 parts by weight of a curable resin. In one or more embodiments, the amount of the second catalyst in the curable resin composition is in a range of from a lower limit selected from any one of0.1, 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, based on 100 parts by weight of the curable resin, where any lower limit may be paired with any upper limit.

[0028] In one or more embodiments, the curable resin composition includes a fire retardant (FR) agent. The FR agent may include aluminum trihydroxide (ATH), magnesium hydroxide (MNH), a compound including phosphorus, a compound including bromine, a compound including chlorine, a compound including nitrogen, and antimony oxide, such as antimony (III) oxide and antimony (V) oxide.

[0029] The amount of FR agent in the curable resin composition is not limited provided that the mixing of the composition may be practically performed, and the viscosity of the curable resin composition, curable preform composition, and the mechanical properties of the cured preform composition remain within an appropriate range. The amount of the FR agent in the curable resin composition may be 75 parts or less by weight, based on 100 parts by weight of the curable resin. In one or more embodiments, the amount of FR agent is in a range of from about 0.1 to about 75 parts by weight, based on 100 parts by weight of a curable resin. In one or more embodiments, the amount of the FR agent in the curable resin composition may be in a range of 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, based on 100 parts by weight of the curable resin, where any lower limit may be paired with any mathematically compatible upper limit.

[0030] In one or more embodiments, the curable resin composition includes a thickening agent. The thickening agent may include, but is not limited to, magnesium oxide (MgO), fumed silica, group IIA metal oxides and hydroxides, aluminum acylates, aluminum chelates and combinations thereof.

[0031] The amount of the thickening agent in the curable resin composition may be 10 parts or less by weight, based on 100 parts by weight of the curable resin. In one or more embodiments, the amount of the thickening agent is in a range of from about 0 to about 10 parts by weight, based on 100 parts by weight of a curable resin. In one or more embodiments, the amount of the thickening agent in the curable resin composition may be in a range of 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, based on 100 parts by weight of the curable resin, where any lower limit may be paired with any upper limit.

[0032] 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, nanoplatelets, silica, kaolin clays, pigments, antistatic agents, calcium stearate, diluent and combinations thereof. In one or more embodiments, the curable resin composition does not include a filler.

[0033] The amount of the filler in the curable resin composition may be 20 parts or less by weight, based on 100 parts by weight of the curable resin. In one or more embodiments, the amount of the filler is in a range of from about 0 to about 20 parts by weight, based on 100 parts by weight of a curable resin. In one or more embodiments, the amount of the filler in the curable resin composition may be in a range of 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, based on 100 parts by weight of the curable resin, where any lower limit may be paired with any upper limit.PROPERTIES - CURABLE RESIN COMPOSITION

[0034] In one or more embodiments, the curable resin composition has a dynamic viscosity in a range of from about 15 Pa-s or less at 85 °C, such as in a range of from about 1 to about 15 Pa-s, as measured by a rotational rheometer. In one or more embodiments, the curable resin composition has a temperature, at which the curable resin composition has a viscosity of 15 Pa-s or less, of 85 °C or lower, such as in a range of from about 20 to 85 °C.

[0035] 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 has a temperature, at which the curable resin composition has a viscosity of 1 Pa-s or less, of 100 °C or lower, such as in a range of from about 75 to 100 °C.

[0036] In one or more embodiments, the curable resin composition, when subjected to a maturation process, has a dynamic viscosity in a range of from about 20000 to100000 Pa-s, as measured with a rotational rheometer. The curable resin composition having a viscosity in the above ranges allows for tack-free handleability and drapability of a curable preform composition at room temperature, and sufficient viscosity at elevated temperatures. If the viscosity of the curable resin composition is below the aforementioned range, there may be less glass fiber low, and parts have a high resin fraction in the outermost regions. If the viscosity is higher than the aforementioned range, the molded parts may have unfilled portions. Matured curable resin composition may be obtained by subjecting the curable resin composition to the same process as the maturing process of a curable preform composition as described in the subsequent section.

[0037] In one or more embodiments, the curable resin composition has an onset curing temperature of about 180 °C or less, as measured by differential scanning calorimeter (DSC).

[0038] In one or more embodiments, the curable resin composition has a peak curing temperature of about 220 °C or less, such as 220 °C or less, 210 °C or less, 200 °C or less, 190 °C or less, or 180 °C or less, as measured by DSC.

[0039] A curable resin composition having an onset curing temperature and peak curing temperature in the above range may have a broadened heat release properties over a longer time period, compared to a composition having a curing temperature above 200 °C. The curable resin composition having the above onset and peak temperature ranges may allow fast curing of the composition, such as reaching a degree of cure of 75 % or above in 5 minutes.CURABLE PREFORM COMPOSITION

[0040] In one or more embodiments, a curable preform composition includes a curable resin composition and a fiber reinforcement. The curable resin composition in the curable preform composition may be the curable resin composition as described in the previous section, and may include a curable resin, a first catalyst and FR agent. The curable resin composition may optionally include a second catalyst, a thickening agent and a filler, as previously described.

[0041] The fiber reinforcement included in the curable preform composition may be fibers generally used in composite applications. Examples of fibers included in thefiber reinforcement include, but are not limited to, glass fiber (E-glass, high strength glass), carbon fiber, aramid fiber, boron fiber, basalt fiber, ultra-high molecular weight polyethylene (UHMWPE) fiber and combinations thereof. The fiber reinforcement may be short fibers, such as chopped fibers and milled fibers, long fibers, non-woven fabric, woven fabric, or stich-bonded fabric. Short fibers refer to as fibers having a length of less than 30 cm, 20 cm, 10 cm, 5 cm, 1 cm, 5 mm, 1 mm, 0.5 mm, or 0.1 mm. The short fibers may have a length in a range from about 0.001 mm to about 30 cm. The long fibers may have a length of at least 30 cm, 40 cm or 50 cm. The fiber reinforcement may be randomly oriented, such that the directions of each fiber reinforcement is not specifically controlled, or the directions of the fiber reinforcement may be controlled such that the fibers are oriented in specific directions.

[0042] The amount of the fiber reinforcement in the curable preform composition may be 60 parts or less by weight, based on 100 parts by weight of the curable resin. In one or more embodiments, the amount of the fiber reinforcement is in a range of from about 1 to about 60 parts by weight, based on 100 parts by weight of a curable resin. In one or more embodiments, the amount of the fiber reinforcement in the curable preform composition may be in a range of 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, based on 100 parts by weight of the curable resin, where any lower limit may be paired with any upper limit.PROPERTIES - CURABLE PREFORM COMPOSITION

[0043] In one or more embodiments, the curable preform composition has a resin flow % of 20% or less. The resin flow % may be measured in accordance with ASTM D3531. In one or more embodiments, the resin flow % is measured by pressing a specimen having specified dimensions at a temperature of 180 °C and under a pressure in a range of 4.8 MPa to 7 MP for 5 minutes, and obtaining a % weight difference of the specimen before and after the pressing.

[0044] In one or more embodiments, the curable preform composition exhibits sufficient drapability. The curable resin composition demonstrating sufficient drapability properties can drape over a desired shape or geometry without forming any defects / wrinkles during composite molding, fill out the desired mold shape, andhas a balance in resin flow at elevated temperature to carry the fibers throughout the mold but not to spill out of the mold.

[0045] In one or more embodiments, the curable preform composition has an onset curing temperature of about 180 °C or less, as measured by differential scanning calorimeter (DSC).

[0046] In one or more embodiments, the curable preform composition has a peak curing temperature of about 220 °C or less, such as 220 °C or less, 210 °C or less, 200 °C or less, 190 °C or less, or 180 °C or less, as measured by DSC.

[0047] A curable preform composition having an onset curing temperature and peak curing temperature in the above range may have a broadened heat release properties over a longer time period, compared to a composition having a curing temperature above 200 °C. The curable preform composition having the above onset and peak temperature ranges may allow fast curing of the composition, such as reaching a degree of cure of 75 % or above in 5 minutes. In SMC molding applications, a cure time of 3 to 5 minutes is considered desirable.CURED PREFORM COMPOSITION

[0048] The present disclosure generally relates to a cured preform composition of a curable preform composition. The cured preform composition may be produced by subjecting the curable preform composition to curing conditions, which may include subjecting the curable preform composition to an elevated temperature and elevated pressure.

[0049] The cured preform composition may be produced by methods and equipment known in the art, such as compression molding, injection molding, vacuum bagging and autoclave or oven curing.

[0050] In one or more embodiments, the cured preform composition has a flammability rating of V-0, as measured in accordance with UL94 vertical flammability test. V-0 is the lowest flammability rating according to UL94 test. In order to achieve the V-0 rating, the sample must not burn 10 seconds or more after exposing the sample to a flame twice for 10 second intervals. In addition, the total bum time of 10 samples must be under 50 seconds.

[0051] In one or more embodiments, a formed char of the cured preform composition, when the composition is tested in accordance with UL94 vertical flammability test, has a low char brittleness. Char having “low char brittleness” refers to char which does not have a weak outer layer that can easily be deformed when a pressure or stress is applied. The brittleness of the char may be determined by measuring the Shore hardness of the cured preform composition subjected to the flammability test. The brittleness of the char may also be determined by indentation hardness test and / or by three-point flexural test.

[0052] In one or more embodiments, the cured preform composition has a degree of cure of at least 75%, when the curable preform composition is cured for 5 minutes at a temperature of 180 °C to produce the cured preform composition.METHOD FOR PRODUCING A CURABLE PREFORM COMPOSITION

[0053] The present 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 fire retardant (FR) agent, and a fiber reinforcement, to produce an unmatured curable preform composition, and maturing the unmatured curable preform composition to produce the curable preform composition. The curable resin composition produced by the method may include at least 15 parts by weight of benzoxazine resin out of 100 parts by weight of the curable resin included in the curable resin composition (at least 15 wt% of the curable resin is benzoxazine resin, based on the total amount of curable resin by weight in the curable preform composition).

[0054] In one or more embodiments, the method includes mixing a curable resin, a first catalyst, an FR agent and a fiber reinforcement to produce an unmatured curable preform composition. The amounts the curable resin, the first catalyst, the FR agent and the fiber reinforcement in the mixing step may be as previously described for the curable resin composition. The mixing of the above-mentioned components may be conducted simultaneously or sequentially.

[0055] FIG. 1 is a flow diagram of the method for producing a curable preform composition, in which the mixing of the components are conducted sequentially. At 100, the curable resin is heated to reduce the viscosity of the resin. At 102, a firstcatalyst is dissolved in a solvent. At 104, the curable resin and the first catalyst dissolved in a solvent 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, an FR agent is admixed with the first mixture to produce an unreinforced resin mixture (a curable resin composition). Other components, such as at least one second catalyst, thickening agent, fillets, may be added with the admixing step of the FR agent. At 110, a fiber reinforcement is admixed with the unreinforced resin mixture to produce an unmatured curable preform composition. At 112, the unmatured curable preform composition is matured to produce a curable preform composition.

[0056] FIG. 2 is a flow diagram of the method for producing a curable preform composition, in which the mixing of the components are conducted 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 the viscosity of the resin. At 202, a first catalyst is dissolved in a solvent. At 204, the first curable resin and the first catalyst dissolved in a solvent are blended to produce a solvated first mixture. At 206, the solvent is removed from the solvated first mixture to produce a first mixture. At 208, the first mixture and at least one second curable resin are combined to produce a second mixture through a process such as mixing or blending. At 210, an FR agent is admixed with the second mixture to produce an unreinforced resin mixture (a curable resin composition). Other components, such as at least one second catalyst, thickening agent, fillets, may be added with the admixing step of the FR agent. At 212, a fiber reinforcement is admixed with the unreinforced resin mixture to produce an unmatured curable preform composition. At 214, the unmatured curable preform composition is matured to produce a curable preform composition.

[0057] FIG. 3 is a flow diagram of the method for producing a curable preform composition, in which the mixing of the components are conducted 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 the viscosity of the resin. 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 in the heated curable resin may be conducted by dispersing the first catalyst in the heated curable resin. The dispersing may include refining of the first catalyst and the heated curable resin byshear force such that the first mixture becomes homogeneous. At 304, which is an optional step, the first mixture and at least one second curable resin are combined to produce a second mixture through a process of mixing or blending. In case at least one second curable resin is not included in the composition, and Step 304 is omitted, the first mixture from Step 302 may be considered as the second mixture. At 306, an FR agent is admixed with the second mixture to produce an unreinforced resin mixture. Other components, such as at least one second catalyst, thickening agent, fillers, may be added with the admixing step of the FR agent. At 308, a fiber reinforcement is admixed with the unreinforced resin mixture to produce an unmatured curable preform composition. At 310, the unmatured curable preform composition is matured to produce a curable preform composition.

[0058] In one or more embodiments, the method includes heating the curable resin (Step 100, Step 200, Step 300). The heating temperature may be determined based on the properties of the curable resin, such as the viscosity of the curable resin. In one or more embodiments, the heating of the curable resin is conducted at a temperature in a range of from about 80 °C to about 85 °C.

[0059] In one or more embodiments in which mixing of the components is conducted in a sequential manner, the method includes blending the curable resin and 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 a first mixture, thereby omitting the dissolving step of the first catalyst in a solvent (Step 102, Step 202).

[0060] In one or more embodiments, the blending of the curable resin and the first catalyst is conducted at room temperature or under an elevated temperature. The elevated temperature may be provided via active heating, such as a heated mixer. In one or more embodiments, the elevated temperature is provided as a result of the curable resin being heated prior to the blending step, as described in the previoussection, or as a result of the heat generated due to shearing of the curable resin and the first catalyst by blending.

[0061] In one or more embodiments, the method includes removing a substantial amount of solvent from the solvated first mixture to produce a first mixture (Step 106, Step 206). A “substantial amount” of solvent refers to at least 80 wt%, at least 85 wt%, at least 90 wt%, at least 95 wt%, at least 99 wt%, at least 99.9 wt%, or 100 wt %, of solvent based on the total amount of the solvent present in the mixture. The removal of the solvent may be conducted by methods known in the art, such as placing the mixture under vacuum. The removal of the solvent from the solvated first mixture may be conducted at room temperature, or under an elevated temperature, such as in a range of from about 30 to 60 °C. The duration of the solvent removal step may be adjusted according to the requirements of one or more embodiments. The duration may be in a range of from about 45 minutes to about 60 minutes. In one or more embodiments which the first catalyst is not dissolved in a solvent, the removing step of the solvent (Step 106, Step 206) is omitted.

[0062] In one or more embodiments in which 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 the at least one second curable resin and the first mixture to produce a second mixture (Step 208, Step 304). Combining may be conducted by mixing or blending of the at least one second curable resin and the first mixture. The combining may be conducted at room temperature or under an elevated temperature. The elevated temperature may be provided via active heating, such as a mixer with heating capability. In one or more embodiments, the elevated temperature is provided as a result of the first mixture being heated prior to the combining step, or as a result of the heat generated by the combining of the at least a second curable resin and the first mixture. In one or more embodiments, the at least one second curable resin may be combined with the first curable resin prior to the addition of the first catalyst. In such a case, the blending step of the first curable resin and the first catalyst would include at least a second curable resin.

[0063] In one or more embodiments, the method includes admixing a fire retardant (FR) agent, and fiber reinforcement with the first mixture or the second mixture to produce an unmatured curable preform composition. The admixing of the FR agentand fiber reinforcement may be conducted simultaneously or sequentially. In one or more embodiments which the FR agent and fiber reinforcement are admixed sequentially, the method may include admixing of the FR agent to produce a unreinforced resin mixture, which may also be referred as a curable resin composition (Step 108, 210, 306), and then admixing the fiber reinforcement and the unreinforced resin mixture (Step 110, 212, 308). The admixing of the fiber reinforcement with the unreinforced resin mixture may be conducted at room temperature or under an elevated temperature, such as a temperature in a range of from about 40 °C to about 100 °C, in order to promote the impregnation of the mixture into the fiber reinforcement. The admixing of the fiber reinforcement and the unreinforced resin mixture may be conducted by adding the fiber reinforcement and the unreinforced resin mixture, heating to the elevated temperature, and mixing the fiber reinforcement and the unreinforced mixture simultaneously or sequentially.

[0064] The mixing, blending, combining and admixing steps may be conducted by any suitable equipment known in the art.

[0065] In one or more embodiments, in which the mixing of the components are conducted sequentially, the admixing of the fiber reinforcement with a resin mixture, which may be an unreinforced resin mixture, a first resin mixture, or a second resin mixture, to produce an unmatured curable preform composition is conducted in a continuous process as illustrated in FIG. 4. The resin mixture may be placed in a “doctor box,” and a carrier film is passed under the doctor box to transfer a predetermined amount of resin onto the carrier film to produce a first resin layer. The resin mixture on the carrier film may have a specific thickness / areal weight. The doctor box is designed to contain the resin and to have a feature to adjust the amount of resin that is dispensed onto the carrier film. The fiber reinforcement may be provided in a continuous form (continuous strand roving), and may then be fed through a chopper to cut into short strands of fibers with a pre-determined length. The chopped fiber reinforcement may then be placed onto the first resin layer.

[0066] As shown in FIG. 4, a second resin layer may be produced by dispensing the resin mixture onto a carrier film in a similar manner as the first resin layer. The first resin layer containing the chopped fiber reinforcement is contacted with the second resin layer such that the fiber reinforcement is sandwiched between the first and thesecond resin layer. The first and second resin layers and fiber reinforcement may then admixed through an impregnation process under an elevated pressure and temperature, such as at least one set of compaction rollers, to produce unmatured curable preform composition. The unmatured curable preform composition may be provided in a continuous sheet form or a “stack,” which may then undergo a maturation process.

[0067] A suitable carrier film known in the art may be used in the continuous admixing process. Examples of the carrier film may include polymer-based release film, which may or may not have a release coating on the film, and release paper.

[0068] The fiber reinforcement may be partially or fully impregnated by the resin mixture. The first and second resin layer may have the same thickness / areal weight, or may have different thickness / areal weight. In one or more embodiments, the continuous admixing process may include only the first resin layer to provide the resin mixture. In such a configuration, a second carrier film containing no resin may be provided prior to the impregnation process such that the transfer of resin onto the machine components may be avoided.

[0069] In one or more embodiments, the method further includes mixing at least one second catalyst. The method may include mixing one or a plurality of the second catalyst. The types and amount of the second catalyst may be as previously described for curable resin composition. In case the mixing of the components is conducted in a sequential manner, the mixing of the second catalyst may be conducted after the solvent removal process (if solvent is used to dissolve the first catalyst), after the blending of the first catalyst and the curable resin (if no solvent is used to dissolve the first catalyst), or after the combining of the first mixture and the at least one second curable resin. In one or more embodiments, the mixing of the second catalyst may be conducted simultaneously with the admixing of FR agent and / or fiber reinforcement, or separately.

[0070] In one or more embodiments, the method further includes mixing a filler. The types and amount of the filler may be as previously described for curable preform composition. In case the mixing of the components is conducted in a sequential manner, the mixing of the filler may be conducted after the solvent removal process(if solvent is used to dissolve the first catalyst), after the blending of the first catalyst and the curable resin (if no solvent is used to dissolve the first catalyst), or after the combining of the first mixture and the at least one second curable resin. In one or more embodiments, the mixing of the filler may be conducted simultaneously with the admixing of FR agent and / or fiber reinforcement, or separately.

[0071] In one or more embodiments, the method includes maturing the unmatured curable preform composition to produce a curable preform composition (Step 112, Step 214, Step 310). The curable preform composition, which may be produced by maturing of the unmatured curable preform composition, may also be referred to as matured curable preform composition.

[0072] In one or more embodiments, the maturing process includes adding a thickening agent to the unmatured curable preform composition, and subjecting the unmatured curable preform composition to a temperature-controlled environment. The types and amount of the thickening agent added in the maturing process may be as previously described for curable preform composition. The addition of a thickening agent may be conducted together with the mixing of the curable resin, first catalyst, FR agent and the fiber reinforcement, or after the mixing step. In case mixing of the components is conducted in a sequential manner, the addition of the thickening agent may be conducted after the solvent removal process (if solvent is used to dissolve the first catalyst), after the blending of the first catalyst and the curable resin (if no solvent is used to dissolve the first catalyst), or after the combining of the first mixture and the at least one second curable resin. In one or more embodiments, the addition of the thickening agent may be conducted simultaneously with the admixing of FR agent and / or fiber reinforcement, or separately.

[0073] The addition of the thickening agent and the subjecting of the unmatured curable preform composition to the temperature-controlled environment may be conducted separately or simultaneously.

[0074] The temperature-controlled environment may have a temperature in a range of from about 25 to about 40 °C. The temperature of the temperature-controlled environment may be controlled such that the temperature variation is less than about 5 °C.

[0075] The unmatured curable preform composition may be subjected to the temperature-controlled environment for at least 1 day. In one or more embodiments, the unmatured curable preform composition may be subjected to the temperature- controlled environment for a duration in a range of from about 1 day to about 10 weeks, such as a lower limit selected from any one of 1 day, 2 days, 3 days, 4 days, and 5 days to an upper limit selected from any one of 1 week, 2 weeks, 5 weeks, and 10 weeks, where any lower limit may be paired with any upper limit.

[0076] In one or more embodiments, the maturing process includes subjecting the unmatured curable preform composition to an elevated temperature to slightly advance the degree of cure of the unmatured curable preform to increase the viscosity. The “elevated temperature” refers to a temperature in a range of from about 30 to about 100 °C. The unmatured curable preform composition may be subjected to the elevated temperature for a duration of about 1 to 9 hours.

[0077] In one or more embodiments, the unreinforced resin mixture has a dynamic viscosity of 15 Pa-s or less at 85 °C, such as in a range of from about 1 to about 15 Pa-s, as measured by a rotational rheometer. In one or more embodiments, the unmatured curable preform composition has a temperature, at which the unmature curable preform composition has a viscosity of 15 Pa-s or less, of 85 °C or lower, such as in a range of from about 20 to 85 °C.

[0078] In one or more embodiments, the unreinforced resin mixture 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 unmatured curable preform composition has a temperature, at which the unmature curable preform composition has a viscosity of 1 Pa-s or less, of 100 °C or lower, such as in a range of from about 75 to 100 °C.

[0079] An unreinforced resin mixture having a viscosity in the aforementioned ranges allows adequate wet-out of the fiber reinforcement at room temperature.METHOD FOR PRODUCING A CURED PREFORM COMPOSITION

[0080] The present disclosure generally relates to a method for producing a cured preform composition. In one or more embodiments, the method includes curing the curable resin composition under an elevated temperature and an elevated pressure.Curing of the curable resin composition may be conducted at an elevated temperature in a range of from about 150 to about 220 °C, and at an elevated pressure in a range of from about 700 to about 1000 psi (4.8 to 7 MPa).

[0081] The curing step may be conducted for a duration of 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 may be conducted for a duration in a range of from about 1 minute to about 500 minutes, such as a lower limit selected from any one of 1, 2, 3, 4, and 5 minutes, to an upper limit selected from any one of 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400 and 500 minutes, where any lower limit may be paired with any mathematically compatible upper limit.

[0082] The curing step may be conducted by methods commonly known in the art, such as compression molding, injection molding, vacuum bagging and autoclave or oven curing.EXAMPLES

[0083] The following examples are provided to illustrate embodiments of the present disclosure. The Examples are not intended to limit the scope of the present invention, and they should not be so interpreted.

[0084] Exemplary curable preform compositions, EXAMPLES 1-13 (EX 1-13), and a preform composition comprising no benzoxazine resin, COMPARATIVE EXAMPLE 1 (CE 1), were produced by first mixing components as shown in Tables 2-1, 2-2 and 2-3 to produce unmatured curable preform compositions.

[0085] The descriptions of the components and chemicals / materials represented by alphabetical and alpha-numerical codes in Tables 2-1, 2-2 and 2-3 are provided in Table 1. Catalyst Cl is a catalyst for resin Al, catalyst C2 is a catalyst for resin A2, and catalyst C3 and C4 are catalysts for resin A3. Catalyst Cl represents a first catalyst, and catalyst C2, C3 and C4 represent second catalysts.[Table 1][Table 2-1][Table 2-2][Table 2-3]

[0086] The production of EX 1-13 was conducted by placing a benzoxazine resin, which was semi solid, in a disposable cup, and placing the cup containing benzoxazine resin in an oven at 80-85 °C until the resin became a liquid. The size of the disposable cup was chosen such that the cup can be placed in a Thinky mixer (available from Thinky U.S.A., Inc.).

[0087] For examples which included phenolic resin (EX3 and EX7), the phenolic resin (solid novolac phenolic resin) was heated to a temperature of 80 to 100 °C to soften and melt, and mixed with the benzoxazine resin in the Thinky mixer prior to adding Lithium iodide catalyst. Lithium iodide (Lil) was dissolved in acetone and blended with the benzoxazine resin or benzoxazine / phenolic resin blend in the Thinky mixer at 2000 rpm for 2 minutes while the mixture was hot to produce a solvated first mixture.

[0088] The solvated first mixture was placed in a temperature-controlled vacuum oven at 50 °C and the solvent was removed for 45 minutes to 60 minutes, or until all solvent was removed to produce a first mixture.

[0089] For examples which included unsaturated polyester (EX2, 4-13), unsaturated polyester was added to the first mixture, and blended in the Thinky mixer at 2000 rpm for 3 minutes while the resin was still warm to produce a second mixture.

[0090] For examples which included flame-retardant agents (Aluminum trihydroxide), additional catalysts (Hexamethylenetetramine (HMTA), Tert-butylperoxy-2- ethylhexyl ester (TBEC), Azobisisobutyronitrile (AIBN)), and thickening agents (magnesium oxide, fumed silica), respective flame retardant agents, catalysts and thickening agents were added to either the first mixture (for EX 1 and EX 3), or the second mixture (for EX 2, 4-13), and blended in the Thinky mixer at 2000 rpm for 3 minutes or until homogenously mixed to obtain an unreinforced resin mixture.

[0091] Fiber reinforcement was added to the unreinforced resin mixture, and the unreinforced resin mixture and fiber reinforcement was placed in a temperature- controlled oven at 80 °C for 2 minutes to improve fiber impregnation. The unreinforced resin mixture and fiber reinforcement was then mixed manually with a stick to produce an unmatured curable preform composition.

[0092] The unmatured curable preform composition was placed into a silicone mold made from high temperature silicone rubber sheets having a Shore hardness of 60A to be prepared for maturation. The mold had dimensions of 135 mm x 20 mm x 3 mm. The mold was used in order to produce specimens which do not require cutting or trimming. The mold containing the unmatured curable preform composition was placed in the temperature-controlled oven at 80 °C for 2.5 hours in order to produce a matured curable preform composition having a desired drapability and tackiness . The mold containing the composition was removed from the oven and allowed to cool down to room temperature before removed from the mold.

[0093] The production of CE1 was conducted in the same manner as EX 1-13, except that the heating of benzoxazine resin, blending of benzoxazine resin and Lil, and removing of solvent were not conducted.PROPERTIES - UNCURED PREFORM COMPOSITIONS

[0094] Various physical properties of the curable preform compositions of EXAMPLES 1-13 and COMPARATIVE EXAMPLE 1 were measured as described below.

[0095] Dynamic viscosity of each example was measured prior to the addition of the fiber reinforcement (the unreinforced resin mixture of each example) by TA Instruments Discovery hybrid rotational parallel plate rheometer. The parallel plates had a diameter of 25.0 mm and was made of ETC aluminum. The gap of the plates was set at 1000 microns. The test was conducted with a start and end temperatures of 25 °C and 280 °C, a ramp rate of 5.0 °C / min, sampling interval of 1.0 s / pt (single point), strain of 0.01%, frequency of 1.0 Hz, soak time of 0.0 s and soak time after ramp of 0.0 s. From the dynamic viscosity testing, a temperature at which the unmatured preform composition excluding the fiber reinforcement exhibited a viscosity of 15 Pa-s was obtained.

[0096] The matured EXAMPLE 1-12 and COMPARATIVE EXAMPLE 1 were confirmed to be drapable by touching the matured samples to confirm appropriate flexibility, and ease of cutting and carrying.

[0097] The summary of the uncured preform composition physical properties of EXAMPLES 1-13 (EX 1-13) and COMPARATIVE EXAMPLE 1 (CE 1) is shown in Tables 3-1 and 3-2.[Table 3-1]*Dynamic viscosity was measured before adding Chopped glass fiber.[Table 3-2]*Dynamic viscosity was measured before adding Chopped glass fiber.[Table 3-3]

[0098] The results in Tables 3-1, 3-2 and 3-3 show that the curable preform compositions of EXAMPLES 1-12 provide acceptable drapability at maturation, indicating that the preform compositions would be able to drape over a desired mold shape or geometry without wrinkling or formation of defects during the curing process of the preform composition.

[0099] The results further show that the viscosity of 15 Pa s or below is exhibited by unmatured samples (unreinforced resin mixture, curable resin composition) excluding fiber reinforcement as described in EXAMPLES 1-12 at a temperature of 26-84 °C.PROPERTIES - CURED PREFORM COMPOSITIONS

[0100] Test samples of cured preform compositions were prepared from the curable preform compositions of EXAMPLES 1-12 and COMPARATIVE EXAMPLE 1 in order to evaluate the compositions for flame retardant properties.

[0101] The flammability of the cured preform compositions was evaluated in accordance with UL94 flammability test method. Samples of cured preform compositions were prepared as follows. The matured, uncured preform composition of EXAMPLES 1-12 and COMPARATIVE EXAMPLE 1 was placed in a press under a pressure of 5 MPa. The composition remained pressurized until the end of the curing cycle. The press was heated from room temperature to 150 °C at a ramp rate of 8°C / min. The temperature was held at 150 °C for 15 minutes, and then increased to 180 °C at a ramp rate of 8 °C / min. The temperature was held at 180 °C for 30 minutes, and then increased to 220 °C at a ramp rate of 8 °C / min. The temperature was held at 220 °C for 60 minutes for post cure of the composition. The temperature was then lowered to room temperature, at which point the curing cycle was completed and the composition was depressurized. The cured preform composition was removed from the mold and cut into the dimensions of 125 mm x 13 mm x 3 mm using a precision saw. The cut sample was placed in a vacuum oven set at 100 °C in order to remove residual water from the cutting operation. The sample was removed from the oven and cooled to room temperature before being subjected to the flammability test. 10 samples were prepared for each of EXAMPLES 1-12 and COMPARATIVE EXAMPLE 1.

[0102] The flammability test was conducted as follows, in accordance with UL94 flammability test method. A sample was placed vertically between two grips at a location such that the distance between the bottom end of the sample and top of the butane torch is approximately 10 mm. The flame length of the torch was set for 20 mm and therefore, the top 10 mm of the flame would be in contact with the sample. The flame was applied to the sample for 10 seconds and then the flame was removed. The time required for the flame to self-extinguish was recorded. The flame was applied to the sample again for 10 seconds and then the flame was removed. The extinguishing time of the flame was recorded again.

[0103] Upon removal and cooling of the sample, the char brittleness of the formed char on the specimens subjected to the flammability test was evaluated based on the ease or difficulty to scrape off the formed char from the specimens. Samples with formed char that could be easily scraped off were given a grade of “high” char brittleness, while samples having char that is difficult to scrape of were given a grade of “low” char brittleness. The bum height and any defects which may be present in the sample were also recorded.

[0104] Tg of the cured preform compositions was determined by conducting DMA using an analyzer such as Q800 DMA (available from TA Instruments), with parameters including, for example, a temperature range of 25 °C to 350 °C, a ramp speed of 5°C / min, a frequency of 1 Hz, and an amplitude of 10 microns.

[0105] The summary of the cured preform composition properties of EXAMPLES 1- 12 (EX 1-12) and COMPARATIVE EXAMPLE 1 (CE 1) is shown in Tables 4-1, 4- 2 and 4-3.[Table 4-1][Table 4-2][Table 4-3]

[0106] The results in Tables 4-1, 4-2 and 4-3 show that Examples 1-12 meet the requirement for UL94 V-0 rating while providing low char brittleness, suggesting improved FR properties over Comparative Example 1, which had high char brittleness.

[0107] Although only a few example embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from this invention. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus,although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures.

Claims

CLAIMSWhat is claimed is:

1. A curable resin composition, comprising:100 parts by weight of a curable resin;0.1 to 5 parts by weight of a first catalyst which is lithium iodide; and75 parts or less by weight of a fire retardant agent. wherein, out of the 100 parts by weight of the curable resin, at least 5 parts by weight of the curable resin is a benzoxazine resin.

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

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

4. The curable resin composition of any of the preceding claims, wherein the fire retardant agent comprises aluminum hydroxide.

5. The curable resin composition of any of the preceding claims, further comprising at least one of a thickening agent and a filler.

6. The curable resin composition of any of the preceding claims, having at least one of: an onset curing temperature of 180 °C or less, as measured by DSC, and a peak curing temperature of 220 °C or less, as measured by DSC.

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

8. The curable resin composition of any of the preceding claims, having a dynamic viscosity in a range of from 20000 to 100000 Pa-s at a room temperature, as measured by a rotational rheometer, when subjected to a maturing process.

9. A curable preform composition, comprising: a curable resin composition comprising:100 parts by weight of a curable resin;0.1 to 5 parts by weight of a first catalyst which is lithium iodide; and75 parts or less by weight of a fire retardant agent; and a fiber reinforcement, wherein, out of the 100 parts by weight of the curable resin, at least 5 parts by weight of the curable resin is a benzoxazine resin.

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

11. The curable preform of claim 9 or 10, wherein the curable resin composition is drapable.

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

13. A cured preform composition of the curable preform composition of any of claims 9 to 12.

14. The cured preform composition of claim 13, having a flammability rating of V-0, as measured in accordance with UL94 vertical flammability test.

15. The cured preform composition of claim 13 or 14, wherein a formed char of the cured preform composition has a low char brittleness, when tested in accordance with UL94 vertical flammability test.

16. The cured preform composition of any of claims 13 to 15, having a degree of cure of at least 75%, when the curable preform composition is cured for 5 minutes at a temperature of 180 °C.

17. A method for producing a curable preform composition, comprising: mixing 100 parts of a curable resin, 0.15 to 5 parts by weight of a first catalyst, 75 parts or less of a fire retardant agent, and a fiber reinforcement, to produce an unmatured curable preform composition; and maturing the unmatured curable preform composition to produce the curable preform composition, wherein, out of the 100 parts by weight of the curable resin, at least 5 parts by weight of the curable resin is a benzoxazine resin, and wherein the first catalyst is lithium iodide.

18. The method of claim 17, wherein the mixing of the curable resin, the first catalyst, the fire retardant agent and the fiber reinforcement comprises: heating the curable resin; dissolving the first catalyst in a solvent; blending the curable resin and the first catalyst to produce a solvated first mixture; substantially removing the solvent from the solvated first mixture to produce a first mixture; and admixing the first mixture, the fire retardant agent and the fiber reinforcement to produce the unmatured curable preform composition.

19. The method of claim 17, wherein the curable resin comprises a first curable resin and at least one second curable resin, and wherein the mixing of the curable resin, the first catalyst, the fire retardant agent and the fiber reinforcement comprises: heating the first curable resin; dissolving the first catalyst in a solvent; blending the first curable resin and the first catalyst to produce a solvated first mixture; substantially removing the solvent from the solvated first mixture to produce a first mixture; combining the first mixture and the at least one second curable resin to produce a second mixture; and admixing the second mixture, the fire retardant agent and the fiber reinforcement to produce the unmatured curable preform composition.

20. The method of claim 17, wherein the mixing of the curable resin, the first catalyst, the fire retardant agent and the fiber reinforcement comprises: heating the curable resin; dispersing the first catalyst in the heated curable resin by melt mixing to produce a first mixture; and admixing the first mixture, the fire retardant agent and the fiber reinforcement to produce the unmatured curable preform composition.

Images