A resin composition for high-speed forming of continuous fiber-reinforced polyurethane composite profiles and a composite material thereof

Abstract

The application discloses a resin composition for high-speed forming of continuous fiber reinforced polyurethane composite profiles and a composite material thereof, and the resin composition comprises, in parts by weight, 30-55 parts of polyol, 42-60 parts of isocyanate, 3-12 parts of chain extender, 0.5-2.0 parts of a first latent catalyst, 0.2-1.0 parts of a second latent catalyst, 0.1-0.5 parts of an internal release agent, 0.05-0.2 parts of an infiltration enhancer, 1-3 parts of a water-removing agent and 0.1-0.5 parts of a defoaming agent. The internal release agent is octadecyl phosphate dimethylcyclohexylamine salt, and the infiltration enhancer is di(2-ethylhexyl) phosphate dimethylcyclohexylamine salt. By introducing the specific infiltration enhancer and matching the latent catalyst compound system and the internal release agent, the profile interlayer shear strength is high, and the resin and the fiber are closely infiltrated under high-speed forming.

Description

Technical Field

[0001] This invention relates to the field of polyurethane resin technology for pultrusion, and more particularly to a resin composition for high-speed molding of continuous fiber reinforced polyurethane composite profiles and its composite material. Background Technology

[0002] Pultrusion is a highly efficient process for manufacturing continuous fiber-reinforced composite profiles, offering advantages such as high production efficiency, stable product quality, and high fiber utilization. Polyurethane, due to its excellent comprehensive properties, has become a crucial matrix resin for pultrusion of continuous fiber-reinforced composites. As pultrusion processes evolve towards higher efficiency, traction speeds typically need to reach 1.0 m / min or higher. Under high-speed pultrusion conditions, existing polyurethane resin systems mainly face the following two technical challenges:

[0003] First, it is difficult to achieve both a long service life at room temperature and rapid curing in the mold. Second, high linear speed leads to insufficient fiber impregnation, weakens interlayer bonding, and restricts the density and mechanical properties of the product.

[0004] Therefore, how to provide a resin composition that can achieve sufficient resin impregnation of fibers and ensure excellent interlaminar shear strength while meeting the requirements of high-speed pultrusion is a technical problem that needs to be solved. Summary of the Invention

[0005] The purpose of this invention is to provide a resin composition for high-speed molding of continuous fiber reinforced polyurethane composite profiles. This resin composition has the characteristics of fast curing speed, sufficient fiber wetting, and high fiber-resin interface strength under high-speed pultrusion conditions.

[0006] Another object of the present invention is to provide a composite material prepared from the above composition and continuous fibers.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A resin composition for high-speed molding of continuous fiber reinforced polyurethane composite profiles comprises, by weight, the following components: 30-55 parts of polyol, 42-60 parts of isocyanate, 3-12 parts of chain extender, 0.5-2.0 parts of first latent catalyst, 0.2-1.0 parts of second latent catalyst, 0.1-0.5 parts of internal release agent, 0.05-0.2 parts of wetting reinforcement agent, 1-3 parts of dehydrating agent, and 0.1-0.5 parts of defoamer, wherein the internal release agent is dimethylcyclohexyl phosphate salt, and the wetting reinforcement agent is di(2-ethylhexyl) phosphate salt.

[0009] Preferably, the first latent catalyst is a blocked tertiary amine catalyst, and the second latent catalyst is a blocked sulfonic acid catalyst.

[0010] Preferably, the mass ratio of the first latent catalyst to the second latent catalyst is 2:1 to 3:1.

[0011] Preferably, the octadecyl phosphate dimethylcyclohexylamine salt is a neutralization product of octadecyl phosphate and dimethylcyclohexylamine.

[0012] Preferably, the di(2-ethylhexyl) phosphate dimethylcyclohexylamine salt is a neutralization product of di(2-ethylhexyl) phosphate and dimethylcyclohexylamine.

[0013] Preferably, the polyol is one or more of polyether triol and polyether tetraol; the preferred polyether triol of the present invention is polyether triol N330, purchased from Jinan Guolan New Materials Co., Ltd., and the chain extender is one or more of 1,4-butanediol or trimethylolpropane, the preferred polyether triol of the present invention is 1,4-butanediol.

[0014] Preferably, the isocyanate is diphenylmethane diisocyanate, i.e., MDI, purchased from Yantai Wanhua Polyurethane Co., Ltd., product number WANNATE1635.

[0015] Preferably, the dehydrating agent is one or more of oxazolidine dehydrating agents, carbodiimide dehydrating agents, or orthoformate triester dehydrating agents. The present invention preferably uses orthoformate triester dehydrating agent, purchased from Zhongshan Youpai Materials Co., Ltd., item number UP-920. The defoamer is a fluorinated defoamer, specifically a fluorinated modified polysiloxane, purchased from Zhuhai Jintuan Chemical Co., Ltd., item number 702.

[0016] A continuous fiber reinforced polyurethane composite material is prepared from continuous fibers and the resin composition, wherein the continuous fibers are one or more of carbon fiber, glass fiber, or basalt fiber, and the present invention preferably uses glass fiber, the volume percentage of which is 55-75% of the total volume of the composite material.

[0017] Preferably, the volume percentage of the resin composition is 25-45% of the composite material.

[0018] The beneficial effects of this invention are:

[0019] This invention uses di(2-ethylhexyl)phosphate dimethylcyclohexylamine salt with a branched structure as a wetting enhancer. Its 2-ethylhexyl branched structure significantly reduces the dynamic surface tension of the resin, promoting rapid air dissipation and full penetration into the continuous fiber bundle during high-speed traction. Simultaneously, within the dosage range (0.05~0.2 parts) described in this invention, due to the significant steric hindrance of the branched structure, its molecules can only be adsorbed in an isolated and dispersed form on the fiber surface, failing to form a continuous, dense molecular layer covering the entire fiber surface. This discontinuous adsorption mode effectively reduces the dynamic surface tension of the resin and promotes wetting and spreading without forming a continuous, weak interfacial barrier between the fiber and the resin, thus... Without compromising the chemical anchoring of the resin and fiber, excellent wetting enhancement effect is achieved. At the same time, the internal release agent, namely octadecyl phosphate dimethylcyclohexylamine salt, and the wetting enhancer, namely di(2-ethylhexyl) phosphate dimethylcyclohexylamine salt, in the system of this invention have a synergistic effect. Both are tertiary amine salts of phosphate esters, which are chemically inert and will not react with latent amine catalysts in an acid-base reaction, thus disrupting the catalyst's closed equilibrium. This is beneficial for maintaining the long service life of the resin in the impregnation tank. Meanwhile, the straight-chain long alkyl group is responsible for providing continuous and stable release lubrication to migrate to the mold interface, while the branched short alkyl group is responsible for providing strong wetting and spreading at the fiber interface, effectively solving a series of problems such as internal porosity and excessive release resistance that are prone to occur in high-speed pultrusion. Attached Figure Description

[0020] Figure 1 This is a SEM image of the interlaminar shear section of the composite material prepared in Example 1 of the present invention;

[0021] Figure 2 This is a SEM image of the interlaminar shear section of the composite material prepared in Comparative Example 1 of the present invention.

[0022] Figure 3 This is a SEM image of the interlaminar shear section of the composite material prepared in Comparative Example 2 of the present invention. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] The octadecyl phosphate dimethylcyclohexylamine salt used in this invention is prepared by neutralizing octadecyl phosphate and dimethylcyclohexylamine in an equimolar ratio at room temperature; wherein, the octadecyl phosphate monoester content is 95%, purchased from Maclean, catalog number P723258.

[0025] Di(2-ethylhexyl) phosphate dimethylcyclohexylamine salt is prepared by neutralization of di(2-ethylhexyl) phosphate and dimethylcyclohexylamine in an equimolar ratio at room temperature;

[0026] First type of latent catalyst (blocked tertiary amine catalyst): a salt of triethylenediamine and 2-ethylhexanoic acid. Preparation method: Dissolve triethylenediamine in acetone, add an equimolar amount of 2-ethylhexanoic acid, stir at room temperature for 1 hour, and remove the solvent under reduced pressure to obtain the catalyst.

[0027] The second latent catalyst (blocked sulfonic acid catalyst): a salt of p-toluenesulfonic acid and N,N-dimethylcyclohexylamine. Preparation method: p-Toluenesulfonic acid monohydrate is dehydrated and dissolved in ethanol. An equimolar amount of N,N-dimethylcyclohexylamine is added dropwise, and the mixture is stirred at room temperature for 30 minutes. The solvent is then removed by vacuum evaporation to obtain the catalyst.

[0028] Example 1

[0029] The following is a method for preparing a resin composition for high-speed molding of continuous fiber reinforced polyurethane composite profiles and its composite material, as described in this embodiment:

[0030] By weight, 50 parts of polyether triol, 8 parts of 1,4-butanediol, 1.2 parts of blocked tertiary amine catalyst, 0.6 parts of blocked sulfonic acid catalyst, 0.25 parts of dimethylcyclohexyl octadecyl phosphate, 0.12 parts of di(2-ethylhexyl) phosphate, 2 parts of orthoformate triester dehydrating agent, and 0.3 parts of fluorinated defoamer were mixed evenly to form a resin premix. This premix was then mixed with 50 parts of MDI and stirred until homogeneous before impregnating glass fibers. The impregnated fibers were then fed into a pultrusion die, with the three zone temperatures set as follows: Zone 1 110℃, Zone 2 170℃, and Zone 3 190℃. The traction speed was 1.0 m / min. Continuous pultrusion yielded a composite profile with a circular cross-section. The glass fiber volume percentage was 65% of the total composite volume, and the resin composition volume percentage was 35%. The SEM image of the cross-section of the prepared composite material after interlaminar shear testing is shown below. Figure 1 As shown.

[0031] Example 2

[0032] The following is a method for preparing a resin composition for high-speed molding of continuous fiber reinforced polyurethane composite profiles and its composite material, as described in this embodiment:

[0033] By weight, 30 parts of polyether triol, 3 parts of 1,4-butanediol, 0.5 parts of blocked tertiary amine catalyst, 0.2 parts of blocked sulfonic acid catalyst, 0.1 parts of dimethylcyclohexyl octadecyl phosphate, 0.05 parts of di(2-ethylhexyl) phosphate, 1 part of orthoformate triester dehydrating agent, and 0.1 parts of fluorinated defoamer are mixed evenly and then mixed with 42 parts of MDI. The remaining processes are the same as in Example 1. The volume percentage of glass fiber is 65% of the total volume of the composite material, and the volume percentage of the resin composition is 35%.

[0034] Example 3

[0035] The following is a method for preparing a resin composition for high-speed molding of continuous fiber reinforced polyurethane composite profiles and its composite material, as described in this embodiment:

[0036] By weight, 55 parts of polyether triol, 12 parts of 1,4-butanediol, 2.0 parts of blocked tertiary amine catalyst, 1.0 part of blocked sulfonic acid catalyst, 0.5 parts of dimethylcyclohexyl octadecyl phosphate, 0.2 parts of di(2-ethylhexyl) phosphate, 3 parts of orthoformate triester dehydrating agent, and 0.5 parts of fluorinated defoamer were mixed evenly and then mixed with 60 parts of MDI. Glass fiber was then impregnated, and the remaining processes were the same as in Example 1. The volume percentage of glass fiber was 65% of the total volume of the composite material, and the volume percentage of the resin composition was 35%.

[0037] Comparative Example 1

[0038] Compared to Example 1, di(2-ethylhexyl) phosphate dimethylcyclohexylamine salt was not added, while the remaining components and processes remained unchanged. The SEM image of the cross-section of the prepared composite material after interlaminar shear testing is shown below. Figure 2 As shown.

[0039] Comparative Example 2

[0040] Compared to Example 1, the amount of di(2-ethylhexyl) phosphate dimethylcyclohexylamine salt was increased to 0.3 parts, while the remaining components and processes remained unchanged. The SEM image of the cross-section of the prepared composite material after interlaminar shear testing is shown below. Figure 3 As shown.

[0041] Actual test

[0042] (1) Tensile strength, which characterizes the maximum bearing capacity of composite materials under tensile conditions, is tested according to ISO 527-5 standard.

[0043] (2) Bending strength, which characterizes the maximum stress that a composite material can withstand when it breaks under bending load or reaches a specified bending moment. The bending strength of the composite material is tested according to ISO 14125 standard, with a span-to-thickness ratio of 20:1.

[0044] (3) Interlaminar shear strength, a mechanical quantity of shear performance between layers, characterizes the shear resistance of composite materials and the interfacial properties between reinforcing fibers and resin matrix. The interlaminar shear strength of composite materials is tested according to ISO 14130 standard.

[0045] The specific test data is shown in Table 1:

[0046] Table 1

[0047] Example 1 1124 1013 51 Example 2 1109 993 46 Example 3 1187 1022 53 Comparative Example 1 994.5 827 31 Comparative Example 2 1067 894 39

[0048] As can be seen from the table, the tensile strength, flexural strength, and interlaminar shear strength of Examples 1-3 are all at a high level, with the interlaminar shear strength reaching 85 MPa, 76 MPa, and 89 MPa, respectively. Comparative Examples 1 and 2 show significantly lower mechanical properties than the Examples, especially the interlaminar shear strength, which shows the most significant decrease. The only difference between Comparative Example 1 and Example 1 is the absence of di(2-ethylhexyl) phosphate dimethylcyclohexylamine salt. The interlaminar shear strength of Comparative Example 1 is 40 MPa, only 47% of that of Example 1. The tensile strength and flexural strength also decreased by 11% and 18%, respectively.

[0049] Interlaminar shear strength is a direct indicator of the interfacial bonding strength between fibers and resin. The significant decrease in interlaminar shear strength in Comparative Example 1 indicates insufficient resin wetting of the fiber bundle when a wetting reinforcing agent is lacking. At a traction speed of 1.0 m / min, the fiber bundle passes through the impregnation tank for a very short time, requiring the resin to displace air from the fiber surface and penetrate the tiny gaps between the fibers within a very short period. If wetting is insufficient, micro-bubbles or unwetted areas will remain between the fiber and resin. These defects become stress concentration points under shear force, leading to premature interface failure. Macroscopically, this manifests as low interlaminar shear strength.

[0050] In Example 1, di(2-ethylhexyl) phosphate dimethylcyclohexylamine salt was added. This substance has a 2-ethylhexyl branched structure, which can effectively reduce the dynamic surface tension of the resin system. During the impregnation process, the lower dynamic surface tension allows the resin to spread more quickly on the fiber surface, displacing air and penetrating into the fiber bundle, increasing the effective contact area between the resin and the fiber. After curing, a denser interfacial bond is formed between the fiber and the resin, thus significantly improving the interlaminar shear strength. Compared with Comparative Example 2, when the amount of wetting reinforcement exceeds 0.2 parts, the number of wetting reinforcement molecules increases, and a continuous molecular layer begins to form on the fiber surface. Since the mechanical strength of this molecular layer itself is lower than that of the resin matrix, under shear force, the damage preferentially occurs and propagates within this weak interfacial layer, leading to a decrease in interlaminar shear strength. This phenomenon indicates that 0.05 to 0.2 parts is the critical dosage range for the wetting reinforcement to exert a positive effect. Beyond this range, the weakening effect caused by excessive accumulation of the wetting reinforcement at the interface will gradually offset or even exceed its wetting improvement effect.

[0051] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A resin composition for high-speed molding of continuous fiber-reinforced polyurethane composite profiles, characterized in that, The product comprises, by weight, the following components: 30-55 parts polyol, 42-60 parts isocyanate, 3-12 parts chain extender, 0.5-2.0 parts first latent catalyst, 0.2-1.0 parts second latent catalyst, 0.1-0.5 parts internal release agent, 0.05-0.2 parts wetting enhancer, 1-3 parts dehydrating agent, and 0.1-0.5 parts defoamer, wherein the internal release agent is dimethylcyclohexyl octadecyl phosphate, and the wetting enhancer is di(2-ethylhexyl) phosphate.

2. The resin composition according to claim 1, characterized in that, The first latent catalyst is a blocked tertiary amine catalyst, and the second latent catalyst is a blocked sulfonic acid catalyst.

3. The resin composition according to claim 1, characterized in that, The mass ratio of the first latent catalyst to the second latent catalyst is 2:1 to 3:

1.

4. The resin composition according to claim 1, characterized in that, The octadecyl phosphate dimethylcyclohexylamine salt is a neutralization product of octadecyl phosphate and dimethylcyclohexylamine.

5. The resin composition according to claim 1, characterized in that, The di(2-ethylhexyl) phosphate dimethylcyclohexylamine salt is a neutralization product of di(2-ethylhexyl) phosphate and dimethylcyclohexylamine.

6. The resin composition according to claim 1, characterized in that, The polyol is one or more of polyether triol and polyether tetraol; the chain extender is one or more of 1,4-butanediol or trimethylolpropane.

7. The resin composition according to claim 1, characterized in that, The isocyanate is diphenylmethane diisocyanate.

8. The resin composition according to claim 1, characterized in that, The dehydrating agent is one or more of oxazolidine dehydrating agents, carbodiimide dehydrating agents, or orthoformate triester dehydrating agents, and the defoamer is a fluorinated defoamer.

9. A continuous fiber-reinforced polyurethane composite material, characterized in that, It is prepared from continuous fibers and the resin composition, wherein the continuous fibers are one or more of carbon fiber, glass fiber or basalt fiber, and the volume percentage of the continuous fibers is 55-75% of the total volume of the composite material.

10. The composite material according to claim 9, characterized in that, The volume percentage of the resin composition is 25-45% of the composite material.

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