Hybrid thermoplastic fiber and method of making same

Abstract

This invention relates to a hybrid thermoplastic fiber and its preparation method, applicable to the field of polymer-based composite materials technology. The hybrid fiber is composed of thermoplastic resin and uncured epoxy resin, and is prepared by wet spinning. Specifically, the thermoplastic resin and uncured epoxy resin are stirred in a ratio of 1:1 to 5:1 to obtain a mixed powder; the mixed powder is then wet-spun to obtain the hybrid thermoplastic fiber. The advantages of this invention are that the hybrid fiber can act as a shaped carbon fiber preform and as a resin guide during liquid molding, improving the toughness of carbon fiber composites without sacrificing other mechanical properties and heat resistance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of polymer-based composite materials, and particularly relates to a hybrid thermoplastic fiber with the functions of shaping, flow guiding and toughening and a preparation method thereof. BACKGROUND

[0002] Carbon fiber reinforced resin-based composite materials (referred to as carbon fiber composite materials) have excellent specific strength, specific modulus, chemical stability and performance designability, and are widely used in the fields represented by aerospace. Under this background, liquid molding technology with low comprehensive cost and high preparation efficiency is an important direction for the development of carbon fiber composite material forming process. However, the mainstream thermosetting resin matrix has a highly cross-linked structure, which leads to poor interlaminar toughness and insufficient impact damage resistance of carbon fiber composite materials, which limits the further promotion and application of carbon fiber composite materials.

[0003] Chinese patent CN201711414921 (published on July 3, 2018) discloses a preparation method of a self-shaping pre-toughening fiber preform. The preform is obtained by sewing reinforcing fibers with low-melting thermoplastic yarns, which is suitable for the liquid molding process of carbon fiber composite materials. The thermoplastic yarns toughen the composite materials while fixing the reinforcing fibers. However, the low-melting sewing thread will reduce the heat resistance of the composite materials, the sewing process is complex and time-consuming and may damage the reinforcing fibers, and is only suitable for a small number of carbon fiber composite materials that require high degree of structural integration.

[0004] Chinese patent CN106459560A (published on May 10, 2019) discloses a functionalized polymer particle used as a toughening agent. By blending thermoplastic particles that can react with thermosetting resin with the resin, the interlaminar toughness of the carbon fiber composite material can be significantly improved. However, at the same time, the viscosity of the uncured blended resin will also be significantly improved, which makes it impossible to be applied to the liquid molding process that requires resin infusion.

[0005] Chinese patent CN102888007B (published on October 22, 2014) discloses a toughening film with surface protruding microstructure and a preparation method thereof. The complex and variable surface micro-protrusion structure of the film and the combination of different material matrices can match various requirements of carbon fiber composite material toughening effect. However, the toughening film is composed of thermoplastic resin with a high melting point (> 300℃), which makes it difficult to achieve good shaping effect at the conventional preform shaping process temperature (50-150℃). In addition, when the toughening material in the form of a film is applied to liquid molding, it will hinder the flow of resin in the out-of-plane direction during the infusion process and reduce the infusion rate.

[0006] Although the above-mentioned technology improves the interlaminar toughness of carbon fiber composite materials to a certain extent, it has difficulties in balancing the performance of liquid molding process and not reducing the heat resistance and other mechanical properties of the composite material. Therefore, there is a need for a new toughening material that has the functions of shaping, flow guiding and toughening for preparing liquid molded carbon fiber composite materials. SUMMARY

[0007] The present application aims at the deficiencies of the prior art and proposes a hybrid thermoplastic fiber having the functions of shaping, flow guiding and toughening and a preparation method thereof, which improves the structure stability of carbon fiber composite material preforms and the liquid molding efficiency, while improving the interlaminar toughness of the composite material and avoiding the reduction of heat resistance and other mechanical properties.

[0008] A preparation method of a hybrid thermoplastic fiber, comprising the following steps:

[0009] (1) stirring the thermoplastic resin and the uncured epoxy resin in a ratio of 1:1 to 5:1 to obtain a mixed powder;

[0010] (2) preparing the hybrid thermoplastic fiber by wet spinning the mixed powder obtained in step (1).

[0011] Preferably, the thermoplastic resin of the present application is at least one of tertiary amine polyarylether sulfone, benzimidazole-containing polyarylether ketone, and pyridine ring structure-containing polyarylether ketone.

[0012] Preferably, the uncured epoxy resin of the present application is one or more of dicyclopentadiene epoxy resin, polybutadiene epoxy resin, silicone epoxy resin, and aromatic epoxy resin, and the uncured epoxy resin is in a solid state at room temperature and has a melting point range of 50-150℃.

[0013] Preferably, the present application dissolves the mixed powder in N,N-dimethylacetamide and configures a spinning dope with a mass fraction of 30-60% before wet spinning.

[0014] Preferably, in the wet spinning process of the present application, the pressure applied to the spinning dope is 0.01-0.5MPa, the composition of the coagulation bath for wet spinning is deionized water and the coagulation bath temperature is 20-80℃, and the winding speed range is 15-200m / min.

[0015] The present application provides a hybrid thermoplastic fiber having the functions of shaping, flow guiding and toughening, which is composed of a thermoplastic resin and an uncured epoxy resin.

[0016] Compared with the prior art, the hybrid thermoplastic fiber with the functions of shaping, flow guiding and toughening can be efficiently prepared in batches, the hybrid thermoplastic fiber can fix the structure of a preform at a conventional preform shaping process temperature, flow guiding resin is used in liquid molding to improve molding efficiency, and the toughness of a composite material can be improved without losing other mechanical properties and heat resistance. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The hybrid thermoplastic fiber with the functions of shaping, flow guiding and toughening and the appearance and microstructure thereof. DETAILED DESCRIPTION

[0018] The application will be further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the application and not used to limit the scope of the application. Furthermore, it should be understood that those skilled in the art can make various modifications or changes to the application after reading the content of the application, and these equivalent forms also fall within the scope defined by the appended claims.

[0019] A preparation method of a hybrid thermoplastic fiber, comprising the following steps:

[0020] (1) stirring a thermoplastic resin and an uncured epoxy resin in a proportion of 1:1 to 5:1 to obtain a mixed powder.

[0021] The thermoplastic resin is at least one of a tertiary amine polyarylether sulfone, a benzimidazole group-containing polyarylether ketone and a pyridine ring structure-containing polyarylether ketone. The uncured epoxy resin is one or more of a dicyclopentadiene epoxy resin, a polybutadiene epoxy resin, a silicone epoxy resin and an aromatic epoxy resin, and the uncured epoxy resin is in a solid state at room temperature and has a melting point range of 50-150℃.

[0022] (2) preparing the hybrid thermoplastic fiber by wet spinning the mixed powder obtained in step (1).

[0023] The mixed powder is dissolved in N,N-dimethylacetamide, and a spinning dope with a mass fraction of 30-60% is prepared for wet spinning. During the wet spinning process, the pressure applied to the spinning dope is 0.01-0.5 MPa, the composition of the coagulation bath for wet spinning is deionized water, the coagulation bath temperature is 20-80℃, and the winding speed range is 15-200 m / min.

[0024] The application provides a hybrid thermoplastic fiber with the functions of shaping, flow guiding and toughening, which is composed of a thermoplastic resin and an uncured epoxy resin.

[0025] Example 1

[0026] The embodiment provides a method for preparing a hybrid thermoplastic fiber with a shaping, flow guiding and toughening function by melt spinning, and the steps are as follows:

[0027] (1) The dry tertiary amine polyarylether sulfone and the dicyclopentadiene epoxy resin are mixed according to a mass ratio of 4:1. The drying conditions of the polyarylether sulfone are 4h at 140 DEG C, and the drying conditions of the dicyclopentadiene epoxy resin are 1h at 80 DEG C.

[0028] (2) The mixed powder in step (1) is fully mixed in a high-speed crushing stirrer, the stirring speed is 2000r / min, the mixing time is 10s each time, the mixing times are 8 times, and the mixing process temperature is controlled below 50 DEG C.

[0029] (3) The high-speed mixed powder in step (2) is dissolved in N,N-dimethylacetamide to prepare a spinning dope with a mass fraction of 45%;

[0030] (4) The spinning dope obtained in step (2) is used for wet spinning, the pressure applied to the spinning dope is 0.2MPa, the composition of the coagulation bath for wet spinning is deionized water, the coagulation bath temperature is 25 DEG C, and the winding speed ranges from 15m / min, and finally the hybrid thermoplastic fiber is obtained.

[0031] (5) The hybrid thermoplastic fiber in step (4) is cut into short fibers with a diameter of 6-8mm, and is laid in the carbon fiber plain fabric (T300, 24k, 200g / m 2 ) layer with a surface density of 30g / m 16 , and a laying sequence of [0] 2 , is sealed by a vacuum bag, is vacuumized and compacted at 100 DEG C for 30 minutes, is impregnated with 90 DEG C defoamed epoxy resin, is cured and formed (curing temperature 180 DEG C, curing time 120 minutes) to prepare a carbon fiber composite material. The carbon fiber composite material is cut to obtain a sample with a size of 150mm*25mm*4mm, which is used for I-type interlaminar fracture toughness test.

[0032] According to the ASTM D5528 test standard, the I-type interlaminar fracture toughness of the carbon fiber composite material is tested by using a double cantilever beam sample, and the calculation formula is as follows.

[0033]

[0034] In the formula, G IC is the I-type interlaminar fracture toughness (J / m 2), b is the width of the sample (mm), a is the total length of the crack on the side of the sample (mm), |Δ| is the crack length correction factor, and P and δ are the load (N) and beam displacement (mm) at the corresponding crack length, respectively. The total crack length a is the sum of the initial crack length a0 and the crack propagation length Δa obtained from the scale on the side of the sample. The calculation results are shown in Table 1.

[0035] Example 2

[0036] This embodiment provides a method for preparing thermoplastic fibers with shaping, flow guiding and toughening functions, and a liquid-molded carbon fiber composite material with interlayer toughening, the steps of which are as follows:

[0037] (1) The dried polyarylether ketone containing pyridine ring structure and the silicone epoxy resin were mixed in a mass ratio of 3:2. The polyarylether ketone containing pyridine ring structure was dried at 160℃ for 3 hours, and the silicone epoxy resin was dried at 80℃ for 1 hour.

[0038] (2) The mixed powder described in step (1) is thoroughly mixed in a high-speed pulverizer and mixer at a speed of 2500 r / min, with each mixing time being 10 s and the mixing number being 8 times. The temperature during the mixing process is controlled below 50°C.

[0039] (3) Dissolve the mixed powder obtained by high-speed mixing in step (2) in N,N-dimethylacetamide to prepare a spinning solution with a mass fraction of 38%;

[0040] (4) Wet spinning is performed using the spinning solution obtained in step (2). The pressure applied to the spinning solution is 0.15 MPa. The coagulation bath composition of wet spinning is deionized water, the coagulation bath temperature is 40℃, and the winding speed range is 21 m / min. Finally, hybrid thermoplastic fibers are obtained.

[0041] (5) Cut the hybrid thermoplastic fiber obtained in step (4) into short fibers with a diameter of 6-8 mm, and feed them at 40 g / m 2 The areal density is laid in a ply sequence of [0]. 16 Carbon fiber plain weave fabric (200g / m) 2 A carbon fiber composite material was prepared by sealing the interlaminar layers (24K T300) in a vacuum bag, compacting it under vacuum at 100℃ for 30 minutes, and then infusing it with degassed epoxy resin at 90℃. The mixture was then cured at 180℃ for 120 minutes to obtain the final product. The carbon fiber composite material was cut into strips measuring 150mm × 25mm × 4mm for type I interlaminar fracture toughness testing.

[0042] The interlaminar fracture toughness of carbon fiber composite was tested according to ASTM D5528 test standard, using double cantilever beam sample, and the calculation formula is shown as follows.

[0043]

[0044] G = (P / b) * (a + |Δ|) / 2a IC is the interlaminar fracture toughness (J / m 2 ), b is the width of the sample (mm), a is the total length of the crack on the side of the sample (mm), |Δ| is the crack length correction factor, P and δ are the load (N) and the beam displacement (mm) corresponding to the crack length, respectively. The total crack length a is the sum of the initial crack length a0 and the crack propagation length Δa obtained according to the sample side scale, and the calculation results are shown in Table 1.

[0045] Comparative Example 1

[0046] A carbon fiber plain fabric (200g / m 2 , 24K T300) was laid in a layering order of [0] 16 , sealed with a vacuum bag, vacuumized and compacted at 100℃ for 30 minutes, then poured with 90℃ defoamed epoxy resin, and cured by temperature rising (curing temperature 180℃, curing time 120 minutes) to obtain a carbon fiber composite material. The carbon fiber composite material was cut to obtain a sample with a size of 150mm×25mm×4mm, which was used for interlaminar fracture toughness test.

[0047] The interlaminar fracture toughness of carbon fiber composite was tested according to ASTM D5528 test standard, using double cantilever beam sample, and the calculation formula is shown as follows.

[0048]

[0049] G = (P / b) * (a + |Δ|) / 2a IC is the interlaminar fracture toughness (J / m 2 ), b is the width of the sample (mm), a is the total length of the crack on the side of the sample (mm), |Δ| is the crack length correction factor, P and δ are the load (N) and the beam displacement (mm) corresponding to the crack length, respectively. The total crack length a is the sum of the initial crack length a0 and the crack propagation length Δa obtained according to the sample side scale, and the calculation results are shown in Table 1.

[0050] Table 1

[0051] Sample Interlaminar fracture toughness (J / m 2 )]]> Example 1 765.0 Example 2 658.5 Comparative Example 1 370.6

[0052] The specific embodiments of the present application are described above. It needs to be understood that the present application is not limited to the specific embodiments described above, and various changes or modifications can be made by those skilled in the art within the scope of the claims, which does not affect the essential content of the present application. The embodiments of the present application and the features in the embodiments can be combined with each other at will without conflict.

Claims

1. A method for preparing hybrid thermoplastic fibers, characterized in that, Includes the following steps: (1) A mixed powder is obtained by stirring thermoplastic resin and uncured epoxy resin in a ratio of 1:1 to 5:1; wherein the thermoplastic resin is at least one of tertiary amine polyarylether sulfone, polyarylether ketone containing benzimidazole group, and polyarylether ketone containing pyridine ring structure. (2) The mixed powder obtained in step (1) is used to prepare hybrid thermoplastic fibers by wet spinning; the mixed powder is dissolved in N,N-dimethylacetamide to prepare a spinning solution with a mass fraction of 30-60% and then wet spinning is performed; during the wet spinning process, the pressure applied to the spinning solution is 0.01-0.5MPa, the coagulation bath composition of the wet spinning is deionized water and the coagulation bath temperature is 20-80℃, and the winding speed range is 15-200m / min.

2. The preparation method according to claim 1, characterized in that, The uncured epoxy resin in step (1) above is one or more of dicyclopentadiene epoxy resin, polybutadiene epoxy resin, silicone epoxy resin, and aromatic epoxy resin. The uncured epoxy resin is solid at room temperature and has a melting point range of 50-150℃.

3. A hybrid thermoplastic fiber obtained by the preparation method according to any one of claims 1-2.

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