Preparation method of high-flow nylon 6 composite material based on nylon 66 fiber reinforcement and composite material

Abstract

The invention discloses a preparation method of a high-flowability nylon 6 composite material based on nylon 66 fiber reinforcement and the composite material. Nylon 66 fibers with similar chemical structures are used as reinforcing skeletons to reinforce and toughen high-flowability nylon 6, firstly, a dopamine solution is used for carrying out surface treatment on a nylon 66 fabric; polydopamine nano-particles are formed through self-polymerization of dopamine on the surface of the nylon 66 non-woven fabric, the interface bonding force can be enhanced through the hydrogen-bond interaction among polydopamine, nylon 6 and nylon 66, and then a mechanical interlocking structure is formed by high-flow nylon 6 and the polydopamine particles on the surface of nylon 66 under the hot-pressing effect. The generated mechanical force further enhances the interface bonding force between the nylon 66 non-woven fabric and the high-flowability nylon 6 resin base material, and the problems that the interface bonding force between the existing high-flowability nylon 6 and the reinforced fiber layer is low, the toughness is poor and the like are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of nylon reinforcement, and more specifically, relates to a preparation method of a high-flow nylon 6 composite material based on nylon 66 fiber reinforcement and the composite material. Background Art

[0002] High-flow nylon 6 offers advantages such as rapid prototyping, low processing costs, extensive design freedom, and excellent surface properties. However, nylon's high flow properties are often achieved by reducing molecular weight or adding lubricants, which undoubtedly leads to a significant decrease in material properties. For example, a lower molecular weight weakens the entanglement between molecular chains, resulting in a decrease in tensile strength and impact strength, which in turn limits the application of high-flow nylon 6 in high-performance applications such as structural parts and heat-resistant electronic components.

[0003] At present, conventional approaches to improve the performance of nylon 6 while retaining its high fluidity include:

[0004] (1) Utilizing the synergistic effect of fibers, that is, by adding fiber reinforcement, the tensile strength and impact strength of nylon can be effectively enhanced. For example, CN103013099A discloses a high-flowability long glass fiber reinforced nylon 6 material and its preparation method, which discloses the use of glass fiber reinforced high-flowability nylon 6 material, thereby greatly improving the rigidity, strength and impact resistance of the material.

[0005] (2) Elastomer toughening, such as using maleic anhydride grafted thermoplastic elastomer and blending it with nylon 66, can significantly improve the impact strength. In CN103571182A, a high-flowability toughened filled nylon and its preparation method are used to graft maleic anhydride onto a polyolefin elastomer with ultra-high fluidity, promote the dispersion of mineral fillers in nylon, improve the impact resistance, and have better impact resistance than traditional toughening agent toughened filled nylon, and have higher flow properties and better processing stability.

[0006] (3) Hyperbranched polymer modification: using hyperbranched polyamide to increase the molecular chain gap through its branched structure and reduce the melt viscosity, such as CN117532794A, a method for improving the processing fluidity of nylon 66 composite materials using hyperbranched polyamide.

[0007] The elastomer, hyperbranched polymer or fiber added in the above method can utilize the group carried or grafted by itself to improve the dispersibility in nylon and the compatibility with nylon. However, in the lamination process of nylon 6 material and other materials, the reinforcement needs to maintain the compatibility of the reinforcement and the matrix to avoid the separation between the layers and reduce the material performance. In order to improve the compatibility between multilayer composite materials, as disclosed in CN106671543B surface modified regenerated carbon fiber felt reinforced nylon composite material and preparation method thereof, formic acid solution is used to form some oxygen-containing active functional groups on the carbon fiber surface, and the regenerated carbon fiber felt is treated with formic acid solution by dissolving nylon, and oxygen-containing functional groups are used to generate chemical reactions, thereby improving the compatibility of carbon fiber and resin matrix. However, when using nylon 66 fiber reinforced nylon 6 material with similar composition, formic acid will cause the infiltration of nylon structure, destroy intermolecular hydrogen bonds, cause the material to swell and gradually dissolve, and under acidic conditions, the amide bond of nylon may undergo acidic hydrolysis, which instead causes the performance of the material to decline.

[0008] CN105603717B, a surface-modified aramid fiber and its preparation method, discloses immersing aramid in a dopamine solution to produce dopamine-coated aramid fiber, utilizing the groups contained in dopamine to enhance its binding ability with the material. While the dopamine modification improves compatibility, the bonding strength between the fiber layer and the nylon layer after lamination has certain limitations. When subjected to a certain force, the fiber layer and the matrix layer are prone to delamination. Furthermore, while increasing the strength of nylon 6, it also significantly reduces its toughness, resulting in a significant decrease in the material's toughness. Summary of the Invention

[0009] In order to overcome the problems of weak bonding strength and strong limitation between existing high-flow nylon 6 and fiber layer, easy partial peeling under stress and greatly reduced toughness, the present invention provides a preparation method of high-flow nylon 6 composite material based on nylon 66 fiber reinforcement.

[0010] Another technical problem solved by the present invention is to provide a nylon 6 / nylon 66 composite material obtained based on the preparation method.

[0011] The present invention is achieved through the following technical solutions:

[0012] A method for preparing a high-flow nylon 6 composite material based on nylon 66 fiber reinforcement, comprising the following steps:

[0013] S1. Immersing nylon 66 fibers in a dopamine hydrochloride solution having a concentration of 4 to 6 mg / mL and a pH of 8 to 9 for 2 to 8 hours to obtain nylon 66 fibers having self-polymerized polydopamine nanoparticles formed on their surfaces;

[0014] S2. The nylon 66 fiber obtained in S1 is hot-pressed with nylon 6 to obtain a reinforced high-flow nylon 6 composite material.

[0015] Furthermore, the nylon 66 fiber is treated with an ethanol solution to remove surface grease and is then dried before being immersed in the dopamine hydrochloride solution.

[0016] Furthermore, the ethanol solution treatment is performed by ultrasonic treatment in a 98% ethanol solution for 15 minutes.

[0017] Furthermore, the nylon 66 fiber is a nylon 66 non-woven fabric, which contains multi-directional fibers and can simultaneously reinforce the matrix in the transverse and longitudinal directions.

[0018] Furthermore, the thickness of the nylon 66 non-woven fabric is 0.26 to 0.30 mm.

[0019] Furthermore, the concentration of the dopamine hydrochloride solution is 5 mg / mL and the pH value is 8.5.

[0020] Furthermore, the treatment time of the dopamine hydrochloride solution is 6 hours.

[0021] Furthermore, the hot pressing temperature is 225-245° C., and the heating time is 5-15 minutes.

[0022] Furthermore, the hot pressing pressure is 480-530 kg, and the pressing time is 3-8 minutes.

[0023] Furthermore, the mold opening temperature of the hot pressing is 130-160° C., and the cooling water flow rate is 8-12 L / h.

[0024] Compared with the prior art, the beneficial effects are:

[0025] The present invention adopts nylon 66 fiber with similar chemical composition and good mechanical properties to reinforce nylon 6 material with low mechanical strength and high fluidity, on the one hand, to solve the compatibility problem between the two, and on the other hand, to enhance the interfacial bonding force by utilizing the hydrogen bonding between the two to achieve "self-reinforcement". On this basis, the present invention adopts the modification of nylon 66 fiber by utilizing dopamine, and further enhances the interfacial bonding force by the hydrogen bonding between polydopamine and nylon 6 and nylon 66, thereby achieving the reinforcement of high-flow nylon resin and the toughening effect of composite materials. In addition, the present invention utilizes dopamine to self-polymerize on the surface of nylon 66 fiber to form polydopamine nanoparticles, strictly controls the polymerization time, and forms a micro-protrusion structure on the surface of nylon 66 fiber. Under the action of hot pressing of nylon 66 fiber and high-flow nylon 6, the high-flow nylon 6 material combines with the micro-protrusion structure on the nylon 66 fiber to form a "mechanical interlocking structure", achieving the dual enhancement of hydrogen bonding and mechanical force.

[0026] Figures in the specification

[0027] Figure 1is the SEM image of untreated nylon 66 nonwoven fabric / nylon 6 resin composite material.

[0028] Figure 2 These are scanning electron micrographs of nylon 66 nonwoven fabrics treated with polydopamine for different periods of time.

[0029] Figure 3 These are scanning electron micrographs of nylon 66 / nylon 6 resin composites treated with polydopamine for different times.

[0030] Figure 4 This is the tensile stress-strain curve of pure high-flow nylon 6 resin.

[0031] Figure 5 This is a tensile stress-strain curve of the nylon 66 non-woven fabric / high-flow nylon 6 resin composite material in Comparative Example 1.

[0032] Figure 6 1 is a tensile stress-strain curve of the nylon 66 non-woven fabric / high-flow nylon 6 resin composite material in Example 1.

[0033] Figure 7 3 is a tensile stress-strain curve of the nylon 66 non-woven fabric / high-flow nylon 6 resin composite material in Example 2.

[0034] Figure 8 3 is a tensile stress-strain curve of the nylon 66 non-woven fabric / high-flow nylon 6 resin composite material in Example 3.

[0035] Figure 9 3 is a tensile stress-strain curve of the nylon 66 non-woven fabric / high-flow nylon 6 resin composite material in Example 4. DETAILED DESCRIPTION

[0036] The present invention will be further explained and illustrated below with reference to the examples, but the specific examples do not limit the present invention in any form. Unless otherwise specified, the methods and equipment used in the examples are conventional methods and equipment in the art, and the raw materials used are all conventional commercially available raw materials.

[0037] Example 1

[0038] This embodiment provides a method for preparing a high-flow nylon 6 composite material based on nylon 66 fiber reinforcement, the steps comprising:

[0039] S1. Ultrasonic clean nylon 66 nonwoven fabric with a thickness of 0.26-0.30 mm with 98% ethanol for 15 minutes to remove surface grease, and then vacuum dry at 80°C for 2 hours.

[0040] S2. Immerse the dried nylon 66 nonwoven fabric in a dopamine hydrochloride solution with a concentration of 5 mg / mL and a pH of 8.5 for 6 hours to allow polydopamine nanoparticles to form on the surface of the nylon 66 nonwoven fabric. Remove the fabric and air dry.

[0041] S3. A nylon 66 nonwoven fabric with polydopamine nanoparticles formed on its surface was hot-pressed with high-flow nylon 6 at a temperature of 235°C, a heating time of 10 min, a pressure of 500 kg, and a pressing time of 5 min. The fabric was then cooled to 150°C at a cooling water flow rate of 10 L / h and molded to obtain a reinforced high-flow nylon 6 composite material.

[0042] Example 2

[0043] This embodiment provides a method for preparing a high-flow nylon 6 composite material based on nylon 66 fiber reinforcement, the steps comprising:

[0044] S1. Ultrasonic clean nylon 66 nonwoven fabric with a thickness of 0.26-0.30 mm with 98% ethanol for 15 minutes to remove surface grease, and then vacuum dry at 80°C for 2 hours.

[0045] S2. Immerse the dried nylon 66 nonwoven fabric in a dopamine hydrochloride solution with a concentration of 5 mg / mL and a pH value of 8.5 for 2 hours to form polydopamine nanoparticles on the surface of the nylon 66 nonwoven fabric. Remove and dry.

[0046] S3. A nylon 66 nonwoven fabric with polydopamine nanoparticles formed on its surface was hot-pressed with high-flow nylon 6 at a temperature of 235°C, a heating time of 10 min, a pressure of 500 kg, and a pressing time of 5 min. The fabric was then cooled to 150°C at a cooling water flow rate of 10 L / h and molded to obtain a reinforced high-flow nylon 6 composite material.

[0047] Example 3

[0048] This embodiment provides a method for preparing a high-flow nylon 6 composite material based on nylon 66 fiber reinforcement, the steps comprising:

[0049] S1. Ultrasonic clean nylon 66 nonwoven fabric with a thickness of 0.26-0.30 mm with 98% ethanol for 15 minutes to remove surface grease, and then vacuum dry at 80°C for 2 hours.

[0050] S2. Immerse the dried nylon 66 nonwoven fabric in a dopamine hydrochloride solution with a concentration of 5 mg / mL and a pH value of 8.5 for 4 hours to form polydopamine nanoparticles on the surface of the nylon 66 nonwoven fabric. Remove and dry.

[0051] S3. A nylon 66 nonwoven fabric with polydopamine nanoparticles formed on its surface was hot-pressed with high-flow nylon 6 at a temperature of 235°C, a heating time of 10 min, a pressure of 500 kg, and a pressing time of 5 min. The fabric was then cooled to 150°C at a cooling water flow rate of 10 L / h and molded to obtain a reinforced high-flow nylon 6 composite material.

[0052] Example 4

[0053] This embodiment provides a method for preparing a high-flow nylon 6 composite material based on nylon 66 fiber reinforcement, the steps comprising:

[0054] S1. Ultrasonic clean nylon 66 nonwoven fabric with a thickness of 0.26-0.30 mm with 98% ethanol for 15 minutes to remove surface grease, and then vacuum dry at 80°C for 2 hours.

[0055] S2. Immerse the dried nylon 66 nonwoven fabric in a dopamine hydrochloride solution with a concentration of 5 mg / mL and a pH of 8.5 for 8 hours to allow polydopamine nanoparticles to form on the surface of the nylon 66 nonwoven fabric. Remove the fabric and air dry.

[0056] S3. A nylon 66 nonwoven fabric with polydopamine nanoparticles formed on its surface was hot-pressed with high-flow nylon 6 at a temperature of 235°C, a heating time of 10 min, a pressure of 500 kg, and a pressing time of 5 min. The fabric was then cooled to 150°C at a cooling water flow rate of 10 L / h and molded to obtain a reinforced high-flow nylon 6 composite material.

[0057] Example 5

[0058] This embodiment provides a method for preparing a high-flow nylon 6 composite material based on nylon 66 fiber reinforcement, the steps comprising:

[0059] S1. Ultrasonic clean nylon 66 nonwoven fabric with a thickness of 0.26-0.30 mm with 98% ethanol for 15 minutes to remove surface grease, and then vacuum dry at 80°C for 2 hours.

[0060] S2. Immerse the dried nylon 66 nonwoven fabric in a dopamine hydrochloride solution with a concentration of 4 mg / mL and a pH of 8 for 6 hours to form polydopamine nanoparticles on the surface of the nylon 66 nonwoven fabric. Remove and air dry.

[0061] S3. A nylon 66 nonwoven fabric with polydopamine nanoparticles formed on its surface was hot-pressed with high-flow nylon 6 at a temperature of 225°C, a heating time of 15 min, a pressure of 480 kg, and a pressing time of 8 min. The fabric was then cooled to 130°C at a cooling water flow rate of 8 L / h and molded to obtain a reinforced high-flow nylon 6 composite material.

[0062] Example 6

[0063] This embodiment provides a method for preparing a high-flow nylon 6 composite material based on nylon 66 fiber reinforcement, the steps comprising:

[0064] S1. Ultrasonic clean nylon 66 nonwoven fabric with a thickness of 0.26-0.30 mm with 98% ethanol for 15 minutes to remove surface grease, and then vacuum dry at 80°C for 2 hours.

[0065] S2. Immerse the dried nylon 66 nonwoven fabric in a dopamine hydrochloride solution with a concentration of 6 mg / mL and a pH of 9 for 6 hours to form polydopamine nanoparticles on the surface of the nylon 66 nonwoven fabric. Remove and air dry.

[0066] S3. A nylon 66 nonwoven fabric with polydopamine nanoparticles formed on its surface was hot-pressed with high-flow nylon 6 at a temperature of 245°C, a heating time of 5 minutes, a pressure of 530 kg, and a pressing time of 3 minutes. The fabric was then cooled to 160°C at a cooling water flow rate of 12 L / h and molded to obtain a reinforced high-flow nylon 6 composite material.

[0067] Comparative Example 1

[0068] In this comparative example, the nylon 66 non-woven fabric and the high-flow nylon 6 are directly hot-pressed to obtain a reinforced high-flow nylon 6 composite material.

[0069] The nylon 66 non-woven fabric and high-flow nylon resin composite material without dopamine treatment in Comparative Example 1, the nylon 66 non-woven fabric treated with polydopamine for different time periods, and the nylon 66 / nylon 6 resin composite material treated with polydopamine for different time periods in Examples 1 to 4 were respectively subjected to scanning electron microscopy. Figures 1 to 3 , Figure 1 The surface of the nylon 66 nonwoven fabric shown in Figure 1 is smooth without dopamine treatment. However, as the dopamine solution treatment time increases, granular substances, namely polydopamine particles, appear on the surface of the nylon 66 nonwoven fabric fibers. When the treatment time is extended to 8 hours, obvious large particle precipitates appear.

[0070] Taking high flow nylon resin as control, the tensile stress and strain test of nylon 6 composite materials prepared in Examples 1 to 4 and Comparative Example 1 were carried out respectively. The test results are as follows: Figures 4 to 9As shown, compared to the maximum stress of approximately 60 MPa and the maximum strain of approximately 65% ​​for high-flow nylon resin, hot-pressing nylon 6,6, and nylon 6 improves the tensile strength of high-flow nylon 6. The tensile strength of the direct composite of nylon 6,6, and nylon 6 reaches 100 MPa, while the strain is reduced to approximately 35%. The tensile strength of the composite of nylon 6,6, and nylon 6, which has self-polymerized polydopamine nanoparticles on its surface, is further improved. Specifically, with increasing exposure time in the dopamine hydrochloride solution (0 to 6 hours), the maximum tensile stress and strain of the reinforced high-flow nylon 6 composite increase. The composite obtained after 6 hours of dopamine hydrochloride treatment exhibits the best performance, reaching a tensile strength of 120 MPa and a strain of 50%, demonstrating the optimal strengthening and toughening effect of polydopamine. With further addition of dopamine hydrochloride solution, the tensile strain and deformation properties of the material begin to decline.

[0071] Combine Figure 3 It can be seen that after 2h and 4h of treatment with polydopamine, there is an obvious detachment phenomenon at the interface, and the grooves after the fiber is pulled out are relatively smooth. The nylon 66 non-woven fabric and high-flow nylon 6 are mainly combined through hydrogen bonding. After 6h of treatment with dopamine solution, the binding ability of nylon 66 non-woven fabric and high-flow nylon 6 is significantly enhanced due to the influence of hydrogen bonding and mechanical interlocking. However, after 8h of treatment with dopamine solution, due to the obvious large particles of polydopamine particles on the surface of nylon 66 fiber, the bearing capacity of the precipitate accumulated by the large particles is poor, resulting in easy detachment from the matrix when subjected to force, resulting in a decrease in performance.

[0072] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a high-flow nylon 6 composite material based on nylon 66 fiber reinforcement, characterized in that the steps include: S1. Immersing nylon 66 fibers in a dopamine hydrochloride solution having a concentration of 4 to 6 mg / mL and a pH of 8 to 9 for 2 to 8 hours to obtain nylon 66 fibers having self-polymerized polydopamine nanoparticles formed on their surfaces; S2. The nylon 66 fiber obtained in S1 is hot-pressed with nylon 6 to obtain a reinforced high-flow nylon 6 composite material.

2. The method for preparing a high-flow nylon 6 composite material based on nylon 66 fiber reinforcement according to claim 1, characterized in that: The nylon 66 fiber is treated with an ethanol solution and dried before being immersed in the dopamine hydrochloride solution.

3. The method for preparing a high-flow nylon 6 composite material based on nylon 66 fiber reinforcement according to claim 1, characterized in that: The ethanol solution treatment was performed by ultrasonic treatment in a 98% ethanol solution for 15 minutes.

4. The method for preparing a high-flow nylon 6 composite material based on nylon 66 fiber reinforcement according to claim 1, characterized in that: The nylon 66 fiber is nylon 66 non-woven fabric.

5. The method for preparing a high-flow nylon 6 composite material based on nylon 66 fiber reinforcement according to claim 1, characterized in that: The thickness of the nylon 66 non-woven fabric is 0.26-0.30 mm.

6. The method for preparing a high-flow nylon 6 composite material based on nylon 66 fiber reinforcement according to claim 1, characterized in that: The concentration of the dopamine hydrochloride solution was 5 mg / mL and the pH value was 8.

5.

7. The method for preparing a high-flow nylon 6 composite material based on nylon 66 fiber reinforcement according to claim 1, characterized in that: The treatment time of dopamine hydrochloride solution is 6 hours.

8. The method for preparing a high-flow nylon 6 composite material based on nylon 66 fiber reinforcement according to claim 1, characterized in that: The hot pressing temperature is 225-245° C., the heating time is 5-15 minutes, the hot pressing pressure is 480-530 kg, and the pressing time is 3-8 minutes.

9. The method for preparing a high-flow nylon 6 composite material based on nylon 66 fiber reinforcement according to claim 1, characterized in that: The mold opening temperature of hot pressing is 130-160°C, and the cooling water flow rate is 8-12 L / h.

10. The nylon 6 / nylon 66 composite material prepared according to the method for preparing a high-flow nylon 6 composite material reinforced with nylon 66 fibers according to any one of claims 1 to 9.

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