Polydicyclopentadiene / carbon nanofiber composite material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of engineering plastics, and discloses a polydicyclopentadiene / carbon nanofiber composite material and a preparation method and application thereof.The method comprises the steps that DCPD, ENB and MNA are mixed to be uniform, CNF is added and subjected to ultrasonic dispersion, a Grubbs second-generation catalyst is added and subjected to ultrasonic dispersion after freezing, finally, mixed liquid is poured into a mold, and the polydicyclopentadiene / carbon nanofiber composite material is obtained. And heating and curing to obtain the high-performance PDCPD / CNF composite material. According to the preparation method, the interaction between PDCPD and CNF can be remarkably improved, so that the mechanical property of the composite material is improved, the used raw material DCPD has low viscosity and high reaction activity, and rapid forming can be realized; meanwhile, the whole production process of the modified PDCPD composite material is green and environment-friendly, the process is simple, complicated chemical modification is not involved, and the feasibility of large-scale industrial production is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of engineering plastics, and in particular to a polydicyclopentadiene / carbon nanofiber composite material and a preparation method and application thereof. Background Art

[0002] Polydicyclopentadiene (PDCPD) is a thermosetting engineering plastic prepared by ring-opening metathesis polymerization. It has the advantages of light weight, high strength, chemical corrosion resistance, weather resistance and waterproofness, and shows broad application prospects in the fields of construction, electronic appliances, etc. On the other hand, thanks to the low viscosity and high reactivity of its monomer dicyclopentadiene (DCPD), PDCPD can be quickly processed through reaction injection molding technology, which gives it a significant advantage in large-scale industrial production. Unfortunately, although PDCPD itself has high strength, its strength is still not enough to meet the needs in high-performance fields such as aerospace and transportation.

[0003] In order to enhance the mechanical properties of PDCPD, researchers have tried to improve its strength by introducing inorganic fillers such as carbon nanofibers (CNF), carbon nanotubes (CNT), and carbon fibers (CF). Among them, CNF and CF are considered to be one of the potential ideal fillers for reinforcing polymer composites because of their ultra-high strength, high modulus, and excellent thermal stability. However, the interaction between CNF, CF, and PDCPD is weak, which makes it very easy for CNF and CF to agglomerate in the PDCPD matrix, making it difficult to achieve uniform dispersion, thus limiting the further improvement of the mechanical properties of the composite material. Therefore, how to improve the compatibility of CNF and PDCPD, thereby improving its dispersibility in the PDCPD matrix and enhancing interfacial bonding, has become the key to improving the mechanical properties of PDCPD / CNF composites.

[0004] In recent years, researchers have explored a variety of strategies to enhance the interaction between CNF and the PDCPD matrix. For example, the Sanada team found that long-term (nearly 120 min) ultrasound can significantly improve the dispersion of CNF in the DCPD monomer, thereby improving the dispersion of CNF in the PDCPD matrix, and ultimately significantly enhancing the mechanical properties of the PDCPD / CNF composite. However, long-term ultrasound can cause irreversible damage or even fracture to the CNF surface, reduce the mechanical properties of the CNF itself, and limit the further improvement of the composite material performance. On the other hand, He Xuelian's team at South China University of Technology improved the interfacial compatibility of PDCPD and CF by grafting norbornene groups that can copolymerize with DCPD on the CF surface, and finally prepared a high-performance PDCPD / CF composite. However, the preparation process involves complex chemical modifications, which is not conducive to large-scale production. Summary of the invention

[0005] The technical problem to be solved by the present invention is: in view of the problem that the poor compatibility of existing PDCPD and CNF leads to poor comprehensive mechanical properties of composite materials, a preparation method is provided which can improve the compatibility of PDCPD with inorganic fillers such as CNF and enhance the mechanical properties of PDCPD composite materials.

[0006] To achieve the above object, on the one hand, the present invention provides a method for preparing a copolymer-modified polydicyclopentadiene / carbon nanofiber (PDCPD / CNF) composite material, which comprises the following steps:

[0007] S1, dicyclopentadiene (DCPD), ethylidene norbornene (ENB) and methyl nadic anhydride (MNA) are mixed uniformly to obtain a uniform, stable and transparent mixed solution;

[0008] S2, adding carboxylated carbon nanofibers (CNF) and Grubbs second-generation catalyst to the transparent mixed solution of step S1 and dispersing them evenly, pouring the obtained dispersion into a mold, heating and curing to obtain a polydicyclopentadiene / carbon nanofiber (PDCPD / CNF) composite material.

[0009] The present invention introduces MNA as a comonomer of DCPD into the system. On the one hand, it copolymerizes with DCPD through ROMP reaction to form a modified PDCPD matrix. On the other hand, the hydrogen bonding between the anhydride group of MNA and the carboxyl group on the surface of CNF is used to enhance the interface interaction between the PDCPD matrix and CNF. This strategy can not only effectively inhibit the agglomeration of CNF, improve its dispersibility in the DCPD monomer and the PDCPD matrix formed after polymerization, but also significantly enhance the interface bonding, thereby greatly improving the mechanical properties of the PDCPD / CNF composite material and broadening the application field of the PDCPD composite material.

[0010] As a further preferred technical solution of the present invention, the amount of ethylidene norbornene added is 5-20 wt% of the dicyclopentadiene; and / or the amount of methylnadic anhydride added is 2-15 wt% of the dicyclopentadiene.

[0011] As a further preferred technical solution of the present invention, the added amount of the carboxylated carbon nanofibers is 0.05-2 wt % of the total polydicyclopentadiene / carbon nanofiber composite material system.

[0012] As a further preferred technical solution of the present invention, the addition amount of the Grubbs second-generation catalyst is 0.01-0.1 wt % of the dicyclopentadiene.

[0013] As a further preferred technical solution of the present invention, in step S2, carboxylated carbon nanofibers are first added to the transparent mixed solution at room temperature, ultrasonically dispersed, and then Grubbs second-generation catalyst is added and ultra-dispersed at -20~10 °C. More preferably, the ultrasonic time after adding the carboxylated carbon nanofibers is 1~5 min; and / or, the ultrasonic time after adding the Grubbs second-generation catalyst is 1~3 min. Among them, ENB and DCPD are mixed and dispersed in a liquid state at low temperature (-20~10 °C), which is not only convenient for subsequent ultrasonic dispersion of the catalyst, but also helps to enhance the toughness of the PDCPD material. When the Grubbs catalyst is added under relatively high temperature conditions, polymerization will occur, resulting in the catalyst being unable to be ultrasonically dispersed. For this reason, the preferred low temperature is -20~10 °C, and further preferably -20~0 °C.

[0014] As a further preferred technical solution of the present invention, in step S2, the heating and curing molding includes two stages: prepolymerization and post-curing: the prepolymerization temperature is controlled at 40-80 o C, the time is controlled at 5~20 min; the post-curing temperature is controlled at 120~140 o C, the time is controlled within 1~3 h.

[0015] According to another aspect of the present invention, the present invention also provides a polydicyclopentadiene / carbon nanofiber composite material.

[0016] According to another aspect of the present invention, the present invention also provides a use of a polydicyclopentadiene / carbon nanofiber composite material as a thermosetting engineering plastic, which can be applied to the fields of aerospace, transportation, etc.

[0017] The present invention utilizes the characteristics of methyl nadic anhydride (MNA) that it is not only easy to copolymerize with dicyclopentadiene (DCPD), but also can form hydrogen bonds with carboxylated carbon nanofibers (CNF) through its anhydride groups, and cleverly introduces MNA into the DCPD and carboxylated CNF mixed system. On the one hand, MNA and DCPD form a modified PDCPD matrix through ring-opening metathesis polymerization; on the other hand, the anhydride groups of MNA can form a strong interaction with the carboxyl groups on the surface of CNF, thereby improving the dispersibility of CNF in the PDCPD matrix while increasing the interfacial bonding, and finally preparing a high-performance PDCPD / CNF composite material.

[0018] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0019] 1) The present invention can use dicyclopentadiene (DCPD) in the C5 fraction of ethylene byproducts from petroleum cracking or the light benzene fraction of coal coking as a raw material, which has the characteristics of low viscosity and high reactivity and can achieve rapid molding;

[0020] 2) The production process of the composite material of the present invention is green and environmentally friendly, does not generate wastewater, waste gas or dust emissions, and has relatively low energy consumption, which meets the requirements of modern industry for sustainable development;

[0021] 3) The present invention adopts a process of direct blending followed by heating and polymerization, which is simple to operate, highly controllable, and easy to scale up for industrial production;

[0022] 4) The present invention can significantly improve the interaction between CNF and PDCPD and enhance its dispersibility, thereby effectively improving the mechanical properties of PDCPD composite materials, and is expected to broaden the application field of PDCPD composite materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0024] Figure 1 are macroscopic characterization images, wherein a is a digital photograph of the mixed solution formed by DCPD, ENB and CNF in Comparative Example 3, b is a digital photograph of the mixed solution of DCPD, ENB, MNA and CNF in Example 3, c and d are digital photographs of the composite material sheets prepared in Comparative Example 3 and Example 3, respectively.

[0025] Figure 2 For Comparative Example 3 ( Figure 2 a 1 with a 2 ) and Example 3 ( Figure 2 b 1 With b 2 )Scanning electron microscope photograph of the liquid nitrogen brittle fracture of the composite material specimen prepared.

[0026] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings in conjunction with the embodiments. DETAILED DESCRIPTION

[0027] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0028] Unless otherwise defined, the technical terms used in the following examples have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. The test reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods, unless otherwise specified, are all conventional methods.

[0029] The materials used in the following examples and comparative examples are: dicyclopentadiene (DCPD) has a molecular weight of 132.202 and a chemical formula of: 10 H12 ; Ethylene norbornene (ENB) has a molecular weight of 120.192 and a molecular formula of: C 9 H 12 ; The molecular weight of methylnadic anhydride (MNA) is 178.185, and the chemical formula is: C 10 H 10 O 3 ; The manufacturer of carboxylated carbon nanofiber powder (CNF) is Jiacai Technology, purity> 95%; the catalyst is Grubbs second-generation catalyst with a molecular weight of 848.98 and a molecular formula of: C 46 H 65 Cl 2 N 2 PRu.

[0030] Comparative Example 1: Preparation of PDCPD material.

[0031] Step 1: Mix 100 parts by mass of DCPD and 5 parts by mass of ENB to obtain a uniform, stable and transparent mixed solution.

[0032] Step 2: Place the mixed solution at -20 o C for 3 min, add Grubbs second-generation catalyst and ultrasonicate for 2 min to ensure uniform dispersion of the catalyst. Then pour the mixture into a stainless steel mold and heat at 50 o C prepolymerization 15 min, 130 o C for 3 h to finally obtain the PDCPD material.

[0033] Comparative Example 2: Preparation of P(DCPD-co-MNA5) composite material.

[0034] Step 1: 100 parts by mass of DCPD, 5 parts by mass of ENB and 5.25 parts by mass of MNA were mixed evenly to obtain a uniform, stable and transparent mixed solution.

[0035] Step 2: Place the mixed solution at -20 o C for 3 min, add Grubbs second-generation catalyst and ultrasonicate for 2 min to ensure uniform dispersion of the catalyst. Then pour the mixture into a stainless steel mold and heat at 50 o C prepolymerization 15 min, 130 o C for 3 h, and finally P(DCPD-co-MNA 5 ) composite materials.

[0036] Comparative Example 3: Preparation of PDCPD / CNF 0.2 Composite materials.

[0037] Step 1: Mix 100 parts by mass of DCPD and 5 parts by mass of ENB to obtain a uniform, stable and transparent mixed solution.

[0038] Step 2: Add 0.2 wt% CNF to the mixed solution, disperse it uniformly by ultrasonic treatment, and place the resulting dispersion at -20 o C for 3 min, add Grubbs II catalyst, and sonicate again for 2 min to ensure uniform dispersion of the catalyst. Then pour the mixture into a stainless steel mold and heat at 50 o C prepolymerization 15 min, 130 o C for 3 h, and finally PDCPD / CNF was obtained. 0.2 Composite materials.

[0039] Example 1: Preparation of P(DCPD-co-MNA 5 ) / CNF 0.05 Composite materials.

[0040] Step 1: 100 parts by mass of DCPD, 5 parts by mass of ENB and 5.25 parts by mass of MNA were mixed evenly to obtain a uniform, stable and transparent mixed solution.

[0041] Step 2: Add 0.05 wt% CNF to the mixed solution, disperse it uniformly by ultrasonic treatment, and place the resulting dispersion at -20 o C for 3 min, add Grubbs II catalyst, and sonicate again for 2 min to ensure uniform dispersion of the catalyst. Then pour the mixture into a stainless steel mold and heat at 50 o C prepolymerization 15 min, 130 o C for 3 h, and finally P(DCPD-co-MNA 5 ) / CNF 0.05 Composite materials.

[0042] Example 2: Preparation of P(DCPD-co-MNA 5 ) / CNF 0.1 Composite materials.

[0043] Step 1: 100 parts by mass of DCPD, 5 parts by mass of ENB and 5.25 parts by mass of MNA were mixed evenly to obtain a uniform, stable and transparent mixed solution.

[0044] Step 2: Add 0.1 wt% CNF to the mixed solution, disperse it uniformly by ultrasonic treatment, and place the resulting dispersion at -20 oC for 3 min, add Grubbs II catalyst, and sonicate again for 2 min to ensure uniform dispersion of the catalyst. Then pour the mixture into a stainless steel mold and heat at 50 o C prepolymerization 15 min, 130 o C for 3 h, and finally P(DCPD-co-MNA 5 ) / CNF 0.1 Composite materials.

[0045] Example 3: Preparation of P(DCPD-co-MNA 5 ) / CNF 0.2 Composite materials.

[0046] Step 1: 100 parts by mass of DCPD, 5 parts by mass of ENB and 5.25 parts by mass of MNA were mixed evenly to obtain a uniform, stable and transparent mixed solution.

[0047] Step 2: Add 0.2 wt% CNF to the mixed solution, disperse it uniformly by ultrasonic treatment, and place the resulting dispersion at -20 o C for 3 min, add Grubbs II catalyst, and sonicate again for 2 min to ensure uniform dispersion of the catalyst. Then pour the mixture into a stainless steel mold and heat at 50 o C prepolymerization 15 min, 130 o C for 3 h, and finally P(DCPD-co-MNA 5 ) / CNF 0.2 Composite materials.

[0048] Example 4: Preparation of P(DCPD-co-MNA 5 ) / CNF 0.3 Composite materials.

[0049] Step 1: 100 parts by mass of DCPD, 5 parts by mass of ENB and 5.25 parts by mass of MNA were mixed evenly to obtain a uniform, stable and transparent mixed solution.

[0050] Step 2: Add 0.3 wt% CNF to the mixed solution, disperse it uniformly by ultrasonic treatment, and place the resulting dispersion at -20 o C for 3 min, add Grubbs II catalyst, and sonicate again for 2 min to ensure uniform dispersion of the catalyst. Then pour the mixture into a stainless steel mold and heat at 50 o C prepolymerization 15 min, 130 o C for 3 h, and finally P(DCPD-co-MNA 5 ) / CNF 0.3 Material.

[0051] 1. The samples obtained in the above comparative example 3 and example 3 were characterized in terms of macroscopic and appearance, as follows:

[0052] Macroscopic photographs of the DCPD, ENB and CNF mixed solution and the composite material samples obtained in Example 3 were taken, and the results are shown in the figure. Figure 1 As shown in a and c in Example 3, the DCPD, ENB, MNA and CNF mixed solution and the resulting composite material sample were macroscopically photographed, and the results were as shown in Figure 1 b and d in the figure; the sample obtained in comparative example 3 was placed in liquid nitrogen and fractured, and the cross section was observed by scanning electron microscope. The results are shown in Figure 2 a 1 and a 2 The sample obtained in Example 3 was placed in liquid nitrogen and fractured, and the cross section was observed by scanning electron microscope. The results are as follows Figure 2 b 1 and b 2 shown.

[0053] like Figure 1 As shown in Figure 2, the dispersibility of CNF in the DCPD and ENB mixed solution is poor, and there is a wall adhesion phenomenon ( Figure 1 a), which directly leads to the difficulty of uniform dispersion of CNF in the PDCPD matrix formed after curing, and the surface of the prepared composite sheet is obviously uneven ( Figure 1 c). The addition of MNA significantly improved the dispersibility of CNF in the DCPD and ENB mixed solution, showing no wall adhesion phenomenon ( Figure 1 b), and thereby promote the dispersion of CNF in the PDCPD matrix formed after curing, and the appearance of the prepared composite sheet is relatively uniform ( Figure 1 d) in.

[0054] like Figure 2 As shown, for PDCPD / CNF 0.2 Composite materials, it can be found that CNF has a large amount of agglomeration in the PDCPD matrix ( Figure 2 a 1 , a 2 ), while the addition of MNA effectively inhibited the aggregation of CNF ( Figure 2 b 1 , b 2 ), which may be due to the strong hydrogen bonding between the modified PDCPD matrix formed by the copolymerization of MNA and DCPD and the carboxyl groups on the surface of CNF. Figure 1 The results of the macroscopic photographs are consistent with those of the

[0055] 2. The samples obtained from the comparative example and the embodiment were subjected to tensile property test. The experimental conditions were as follows: the tensile rate was 10 mm / min. The results are shown in Table 1.

[0056] Table 1

[0057] As shown in Table 1, PDCPD / CNF obtained in Comparative Example 3 0.2 The mechanical properties of the composite material are very poor, with a tensile strength of only 42.4±4.8MPa and an elongation at break of only 8±6%. This is because a large amount of CNF agglomerates in PDCPD, causing stress concentration and deteriorating the mechanical properties of the original PDCPD. The present invention greatly improves the mechanical properties of the composite material by adding MNA copolymerization modification strategy, wherein the P(DCPD-co-MNA obtained in Example 3 5 ) / CNF 0.2 The tensile strength of the sample is as high as 53.4±1.2MPa, and the elongation at break is as high as 176±9%.

[0058] Although specific embodiments of the present invention are described above, those skilled in the art should understand that these are merely examples and that various changes or modifications may be made to the embodiments without departing from the principles and essence of the present invention. The scope of protection of the present invention is limited only by the appended claims.

Claims

1. A method for preparing a polydicyclopentadiene / carbon nanofiber composite material, characterized in that: The following steps are involved: S1, mixing dicyclopentadiene, ethylidene norbornene and methyl nadic anhydride uniformly to obtain a uniform, stable and transparent mixed solution; S2, adding carboxylated carbon nanofibers and Grubbs II catalyst to the transparent mixed solution of step S1 to disperse evenly, pouring the obtained dispersion into a mold, heating and curing to obtain a polydicyclopentadiene / carbon nanofiber composite material.

2. The method for preparing the polydicyclopentadiene / carbon nanofiber composite material according to claim 1, characterized in that: The amount of ethylidene norbornene added is 5-20 wt% of the dicyclopentadiene; and / or the amount of methylnadic anhydride added is 2-15 wt% of the dicyclopentadiene.

3. The method for preparing the polydicyclopentadiene / carbon nanofiber composite material according to claim 1, characterized in that: The added amount of the carboxylated carbon nanofiber is 0.05-2 wt % of the total polydicyclopentadiene / carbon nanofiber composite material system.

4. The method for preparing the polydicyclopentadiene / carbon nanofiber composite material according to claim 1, characterized in that: The addition amount of the Grubbs second generation catalyst is 0.01-0.1 wt % of the dicyclopentadiene.

5. The method for preparing the polydicyclopentadiene / carbon nanofiber composite material according to claim 1, characterized in that: In step S2, carboxylated carbon nanofibers are first added to the transparent mixed solution at room temperature, ultrasonically dispersed, and then Grubbs second-generation catalyst is added and ultra-dispersed at -20~10°C.

6. The method for preparing the polydicyclopentadiene / carbon nanofiber composite material according to claim 5, characterized in that: The ultrasonic time after adding the carboxylated carbon nanofibers is 1 to 5 min; and / or, the ultrasonic time after adding the Grubbs second generation catalyst is 1 to 3 min.

7. The method for preparing the polydicyclopentadiene / carbon nanofiber composite material according to claim 1, characterized in that: In step S2, the heating and curing process includes two stages: pre-polymerization and post-curing. The pre-polymerization temperature is controlled at 40-80 o C, the time is controlled at 5~20 min; the post-curing temperature is controlled at 120~140 o C, the time is controlled within 1~3 h.

8. A polydicyclopentadiene / carbon nanofiber composite material, characterized in that: The method is prepared by any one of claims 1 to 7.

9. Use of the polydicyclopentadiene / carbon nanofiber composite material according to claim 8 as thermosetting engineering plastics.

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