CN109251480B

CN109251480B - Application of block copolymer in construction of specific nanostructure in epoxy resin and preparation of high-toughness composite material

Info

Publication number: CN109251480B
Application number: CN201810982478.7A
Authority: CN
Inventors: 邹华维; 陈洋; 衡正光; 李霂萱; 张浩若; 梁梅
Original assignee: Sichuan University
Current assignee: Sichuan University
Priority date: 2018-08-27
Filing date: 2018-08-27
Publication date: 2022-03-04
Anticipated expiration: 2038-08-27
Also published as: CN109251480A

Abstract

The invention provides application of a block copolymer in construction of a specific nano structure in epoxy resin and preparation of a high-toughness composite material. Experimental results prove that compared with pure epoxy resin, the toughness of the PDMS-PCL/EP composite material prepared by the invention is obviously enhanced: when PDMS₁‑PCL₄At a content of 40 wt%, the fracture toughness of the thermosetting material with 10-60nm worm-like nano-structure is improved by about 255% compared with that of the pure epoxy resin, while the fracture toughness of the spherical nano-structure is improved by only 42% compared with that of the pure epoxy resin under the same addition amount. Compared with the PCL-b-PDMS-b-PCL/EP composite material, the PDMS-PCL/EP composite material prepared by the invention has obviously better toughness than the PCL-b-PDMS-b-PCL/EP composite material under the same addition amount, and the promotion amplitude reaches 97%. The toughness of the PDMS-PCL/EP composite material prepared in a specific proportion has obvious advantages, unexpected technical effects are achieved, and the PDMS-PCL/EP composite material can be used as a base material of coatings, electrical materials, pouring and packaging materials, adhesives and sealants and widely applied to the fields of aerospace, automobiles, shipbuilding, construction, railway transportation and the like.

Description

Application of block copolymer in construction of specific nanostructure in epoxy resin and preparation of high-toughness composite material

Technical Field

The invention belongs to the field of polymer composite materials, and particularly relates to application of a block copolymer in construction of a specific nanostructure in epoxy resin and preparation of a high-toughness composite material.

Background

Epoxy resin (EP) is an excellent high-strength thermosetting resin, and is a very widely used matrix material. The EP molecule has two or more than two epoxy groups, can be crosslinked and cured with amines, acid anhydrides and polyamides to form a highly crosslinked space three-dimensional network structure, and a cured product of the EP molecule has the advantages of good wear resistance, excellent heat resistance, good chemical stability, excellent electrical insulation, high strength, low shrinkage, easy processing and molding, chemical reagent resistance, good adhesion performance to a base material, low price and the like, and can be widely applied to various fields of national economy such as aerospace, automobiles, shipbuilding, buildings, railway traffic and the like as a matrix resin of electronic coating, electrical materials, pouring and packaging materials, adhesives and sealants. However, a cured product formed after EP curing has high crosslinking density, a spatial three-dimensional network structure, difficult sliding among molecular chains and large internal stress, so that the cured product is hard and brittle, easy to crack, and poor in impact resistance and peeling resistance, and the use requirement is difficult to meet in practical application, so that the application of the cured product is limited to a certain extent, and the defects are caused by insufficient toughness of the EP cured product.

At present, the toughening modification approaches of epoxy resin mainly include methods of toughening rubber elastomers, toughening resin alloying, toughening thermotropic liquid crystal polymers, toughening dendritic molecules, toughening nano particles, toughening by introducing flexible chain segments in a cross-linked network and the like. With the continuous deepening of the research of the nanotechnology, the epoxy resin-based nanocomposite prepared by introducing a small amount of nano structural units (such as nano particles, nano wires, nano tubes, nano sheet layers and the like) can greatly improve the shock resistance of a resin cured product, and other physical properties are rarely influenced, so that the nano toughening modified epoxy resin has a very good application prospect.

Document "Heng Z, Li R, Chen Y, et al. preparation of mapping integration materials of the formation of nanostrucrure in triblock copolymer modified epoxy resins [ J]Journal of Polymer Research,2016,23(7):128 discloses that PCL-PDMS-PCL triblock copolymers have a good toughening effect on epoxy resins, have a spherical structure in the epoxy resins, and have a K value of 20%_ICThe value is improved by 55.56 percent compared with that of pure epoxy resin. It does not improve the toughness of epoxy resin.

Disclosure of Invention

The invention aims to provide application of a block copolymer in construction of a specific nanostructure in epoxy resin and preparation of a high-toughness composite material, wherein the block copolymer is a PDMS-b-PCL diblock copolymer.

Further, the weight ratio of the block copolymer to the epoxy resin is 0.2-1: 1, preferably, the weight ratio of the block copolymer to the epoxy resin is 0.2-0.4: 1; more preferably, the weight ratio of the block copolymer to the epoxy resin is 0.4: 1.

Further, the molecular weight ratio of PDMS to PCL in the PDMS-b-PCL two-block copolymer is 1: 1-4; preferably, the molecular weight ratio of PDMS to PCL in the PDMS-b-PCL diblock copolymer is 1: 3-4.

Further, the epoxy resin is bisphenol A type epoxy resin; the PDMS is polydimethylsiloxane terminated by monohydroxy.

Further, the bisphenol A epoxy resin is selected from E-51 and E-44.

The invention also provides application of the high-toughness epoxy resin composite material in preparing a matrix material, wherein the composite material is prepared from the following raw materials in parts by weight:

40-60 parts of epoxy resin, 0.01-16 parts of PDMS-b-PCL diblock copolymer and 16-23 parts of curing agent.

Further, the composite material is prepared from the following raw materials in parts by weight:

40-50 parts of epoxy resin, 10-16 parts of PDMS-b-PCL diblock copolymer and 16-20 parts of curing agent;

preferably, the composite material is prepared from the following raw materials in parts by weight:

40 parts of epoxy resin, 16 parts of PDMS-b-PCL diblock copolymer and 16 parts of curing agent.

Further, the PDMS is a monohydroxy-terminated polydimethylsiloxane; the curing agent is selected from 3,3 ' -dichloro-4, 4 ' -diaminodiphenylmethane, 4 ' -diaminodiphenyl sulfone and diaminodiphenylmethane; the epoxy resin is selected from E-51 and E-44.

Further, the base material is a base material of paint, an electrical material, a pouring packaging material, an adhesive and a sealant.

Experimental results prove that compared with pure epoxy resin, the toughness of the PDMS-PCL/EP composite material prepared by the invention is obviously enhanced: when PDMS₁-PCL₄At a content of 40 wt%, the fracture toughness of the thermosetting material with 10-60nm worm-like nano-structure is improved by about 255% compared with that of the pure epoxy resin, while the fracture toughness of the spherical nano-structure is improved by only 42% compared with that of the pure epoxy resin under the same addition amount. Compared with the PCL-b-PDMS-b-PCL/EP composite material, the PDMS-PCL/EP composite material prepared by the invention has obviously better toughness than the PCL-b-PDMS-b-PCL/EP composite material under the same addition amount, and the promotion amplitude reaches 97%. The toughness of the PDMS-PCL/EP composite material prepared in a specific proportion has obvious advantages, unexpected technical effects are achieved, and the PDMS-PCL/EP composite material can be used as a base material of coatings, electrical materials, pouring and packaging materials, adhesives and sealants and widely applied to the fields of aerospace, automobiles, shipbuilding, construction, railway transportation and the like.

Obviously, many modifications, substitutions, and variations are possible in light of the above teachings of the invention, without departing from the basic technical spirit of the invention, as defined by the following claims.

The present invention will be described in further detail with reference to the following examples. This should not be understood as limiting the scope of the above-described subject matter of the present invention to the following examples. All the technologies realized based on the above contents of the present invention belong to the scope of the present invention.

Drawings

FIG. 1 shows GPC curves of PDMS as a starting material and two-block copolymers PDMS-b-PCL of four different molecular weights.

FIG. 2 shows four PDMS-b-PCL types¹HNMR comparison.

FIG. 3 is PDMS₁-PCL₁In the FESEM photographs of the thermosetting material (2), a, b and c respectively indicate that the addition amounts of the block copolymers were 10%, 20% and 40%.

FIG. 4 is PDMS₁-PCL₂In the FESEM photographs of the thermosetting material (2), a, b and c respectively indicate that the addition amounts of the block copolymers were 10%, 20% and 40%.

FIG. 5 is PDMS₁-PCL₃In the FESEM photographs of the thermosetting material (2), a, b and c respectively indicate that the addition amounts of the block copolymers were 10%, 20% and 40%.

FIG. 6 is PDMS₁-PCL₄In the FESEM photographs of the thermosetting material (2), a, b and c respectively indicate that the addition amounts of the block copolymers were 10%, 20% and 40%.

FIG. 7 is a SAXS image of a thermoset resin containing a PDMS-PCL diblock copolymer.

FIG. 8 is a DMA curve of the DMS-PCL/EP system.

FIG. 9 shows the glass transition temperature of the PDMS-PCL/EP system.

FIG. 10 shows K for a thermosetting resin_ICThe values are plotted as a function of diblock copolymer content.

FIG. 11 is a FESEM image of fracture surface, wherein a, b, c are epoxy sections containing spherical nanostructures, d, e, f are epoxy sections containing vermicular nanostructures, from left to right, and the scale bars are 10 μm,1 μm and 100nm, respectively.

FIG. 12 is the water contact angle of epoxy resin, a represents pure epoxyA resin; b to e each represents PDMS₁-PCL₁The addition amounts of the block copolymers were 5%, 10%, 20%, 40%; f to i each represents PDMS₁-PCL₂The addition amounts of the block copolymers were 5%, 10%, 20%, 40%; j to m each represents PDMS₁-PCL₄The addition amounts of the block copolymers were 5%, 10%, 20%, 40%; n to q each represents PDMS₁-PCL₃The amounts of block copolymer added were 5%, 10%, 20% and 40%.

FIG. 13 shows the water contact angle values of the PDMS-PCL/EP system.

FIG. 14 is a graph of the change in fracture toughness for epoxy resins of different triblock copolymer content.

Detailed Description

Example 1 preparation and Performance testing of the composite materials of the invention

Firstly, preparation of the composite material of the invention

1. Experimental raw materials and reagents

Bisphenol A glycidyl ether epoxy resin E-51(DGEBA), available from Jiangsu tin-free resin works;

3,3 '-dichloro-4, 4' -diaminodiphenylmethane (MOCA), available from febuxostat, belr, inc;

monohydroxy-terminated polydimethylsiloxane (PDMS-OH), available from Nippon Denshoku industries Co., Ltd. Before use, anhydrous toluene is adopted for azeotropic distillation;

epsilon-caprolactone (. epsilon. -CL), available from Aladdin, 99%, calcium hydride (CaH)₂) Drying, and distilling under reduced pressure;

stannous octoate (Sn (Oct)₂) From Aladdin.

2. Synthesis of diblock copolymer PDMS-b-PCL

Adding the following monohydroxy terminated polydimethylsiloxane PDMS-OH, caprolactone monomer and 0.1 wt% stannous octoate into a dried 250ml round bottom schlenk bottle, and putting a magnetic stirrer to stir uniformly; then freezing by liquid nitrogen, vacuumizing, and unfreezing, wherein the process is circulated for three times, and residual air in the schlenk bottle is removed; putting a schlenk bottle in a vacuum state into an oil bath kettle at the temperature of 120 ℃ for reacting for 36 hours, taking out and cooling to room temperature, dissolving the crude product into dichloromethane, adding the dichloromethane into a large amount of frozen methanol for precipitation, and repeatedly operating for several times until white precipitates are obtained; suction filtered and dried in a vacuum oven at 40 ℃ to constant weight. The formula of the addition amount of each raw material is shown in table 1.

TABLE 1 formulation of the diblock copolymer PDMS-b-PCL

3. Preparation of epoxy thermosetting resin containing PDMS-b-PCL diblock copolymer

The following weight of PDMS-b-PCL two-block copolymer and epoxy resin E-51 at 120 degrees C vigorous stirring and mixing to a uniform state, then adding curing agent MOCA and again vigorous stirring to uniform. The obtained blend is degassed under vacuum state, and then poured into a polytetrafluoroethylene mold, the curing conditions are 150 ℃ for 2h, the curing is carried out at 180 ℃ for 2h, and the epoxy resin sample strip obtained after curing is transparent. The formula of the addition amount of each raw material is shown in table 2.

TABLE 2 PDMS-b-PCL/EP composite formulations

Secondly, detecting the performance of the composite material

1. Testing and characterization

1.1 Gel Permeation Chromatography (GPC)

The measurement of the molecular weight and molecular weight distribution of the polymer was carried out on a gel permeation chromatograph model U.S. Waters1515 (equipped with three 7.8X 300mm columns, THF as solvent, polystyrene calibration) at a test temperature of 30 ℃ with Tetrahydrofuran (THF) as mobile phase and a flow rate of 0.5. mu.L/min with Polystyrene (PS) as calibration standard.

1.2 Nuclear magnetic resonance Hydrogen Spectroscopy (NMR)

Nuclear magnetic resonance hydrogen spectroscopy of the block copolymer was performed on a DRX-400(Bruker, Germany) 400MHz instrument using deuterated chloroform as the solvent at 25 ℃ with Tetramethylsilane (TMS) as the internal standard.

1.3 Dynamic Mechanical Analysis (DMA)

The dynamic mechanical properties were tested on a TA Instruments Q800 (USA) instrument in a three-point bending mode with a frequency of 40Hz, a rate of temperature rise of 3 ℃/min from 30 ℃ to 200 ℃. The rectangular sample size was 20mm by 10mm by 4 mm.

1.4 Small Angle X-ray Scattering (SAXS)

The SAXS test is carried out on a Xeuss 2.0SAXS/WAXSsystem in the key laboratory of the national Polymer materials science of Sichuan university, the test temperature is room temperature, and the test wavelength is

The test conditions were 50.00kV, 0.60mA, and the exposure time was 5 min. The test range of the tester is 2.8-150 nm. The scattering intensity is plotted against the scattering vector to obtain a scattering curve, where q ═ 4 π/λ sin (θ/2) (θ is the scattering angle).

1.5 Field Emission Scanning Electron Microscope (FESEM)

A sample is quenched by liquid nitrogen, the shape of the section is characterized by a scanning electron microscope with the model of JSM-5900(JEOL, Tokyo, Japan), the accelerating voltage is 15kV, and a thin gold layer is sprayed on the section to ensure that the section is conductive in the test process.

1.6 fracture toughness test

Fracture toughness of the cured samples were tested at a rate of 2mm/min using a notched three point bend mode in an Instron 5567 model (Instron, USA) universal tester (according to ASTM E399 standard). The height of the gap is 45-55% of the width of the sample strip. Critical stress field intensity factor (K)_IC) Calculated as follows:

where S is the span of the test, P is the maximum load, B is the thickness of the spline, W is the width of the sample, f (x) is the form factor, and A is the notch depth.

1.7 Water contact Angle test

Contact angle measurements of the samples were performed in a DSA30 contact angle analyzer (KRUS3, germany). Distilled water was used to analyze the samples and measurements were made on all samples at room temperature. In all cases, the drop volume was kept at 10 μ L using a micro-syringe. For accuracy, the contact angles at five different points on the sample were measured and their average values were reported.

2. Results and discussion

2.1 Synthesis of diblock copolymer PDMS-b-PCL

The molecular weight was measured by Gel Permeation Chromatography (GPC), with the molecular weight of the starting polydimethylsiloxane PDMS being 3915g/mol, and the molecular weights of the four PDMS-b-PCL diblock copolymers with different PCL block molecular weights being, respectively, Mn 8449g/mol, Mn 11397g/mol, Mn 15039g/mol, Mn 19333g/mol and Mn 26701 g/mol. Their molecular weights and the ratio of the block molecular weights are listed in Table 3. The GPC curves of the starting PDMS and of these 4 diblock copolymers are shown in FIG. 1, and it can be seen that the GPC curves are essentially monomodal.

TABLE 3 molecular weights and Block ratios of PDMS to the four PDMS-b-PCL' s

Further carries out the preparation of the diblock copolymer PDMS-b-PCL¹And (4) HNMR characterization. Nuclear magnetic resonance hydrogen spectrogram of diblock copolymer PDMS-b-PCL¹HNMR is shown in FIG. 1. Wherein the peak at 0.07-0.09ppm is assigned to the characteristic group [ Si (CH) of polydimethylsiloxane PDMS₃)₂](ii) a The peaks at 1.35-1.41, 1.60-1.68, 2.28-2.38 and 4.04-4.07 are respectively assigned to methylene at different positions in PCL. The peaks of the NMR spectrum of the diblock copolymer PDMS-b-PCL and the corresponding groups are shown in Table 4. The above results indicate that the synthesized polymer has the structural characteristics of both PCL and PDMS.

TABLE 4 peaks of NMR spectra of PDMS-b-PCL and the corresponding groups

2.2 micro-morphology of PDMS-b-PCL/EP System

FIG. 3(a) (b) (c) is a block diagram containing 10, 20 and 40 wt% PDMS₁-PCL₁FESEM photographs of the thermosetting material of (2) and scale bars are all 1 μm, it can be seen that the microphase-separated morphology is spherical. The particle size range is 40-170 nm. As the content of the block copolymer increases, the number of spherical micelles significantly increases. FIGS. 4(a) (b) (c) show PDMS containing 10, 20 and 40 wt% PDMS₁-PCL₂FESEM image of epoxy thermosetting resin of block copolymer, (a) (b) scale bar is 1 μm, and (c) scale bar is 3 μm. The results show that the morphology of the nanostructure remains spherical micelles with increasing content of block copolymer. As the concentration of the block copolymer increases, the particle size (20-350 nm) and the number of spherical micelles increase. FIGS. 5(a) (b) (c) shows PDMS containing 10, 20 and 40 wt% PDMS₁-PCL₃FESEM pictures of thermosets of block copolymers and scale bars are 500 nm. A morphological transition from spherical to worm-like is observed in this system. Spherical micelles were observed at low levels (fig. 5a), with irregular nano-domains called worm-like nanostructures of size 10-40 nm dispersed in a continuous epoxy matrix as the concentration of the block copolymer increased. FIG. 6(a) (b) (c) shows PDMS containing 10, 20 and 40 wt%₁-PCL₄FESEM pictures of thermosets of block copolymers, all at a scale bar of 500 nm. A transition from spherical to worm-like is also observed in this system.

PDMS-containing materials were further investigated by small angle X-ray scattering (SAXS)₁-PCL₁、PDMS₁-PCL₂、PDMS₁-PCL₃、PDMS₁-PCL₄A thermoset material of a diblock copolymer. FIG. 7(a) shows PDMS containing 5%, 10%, 20% and 40%₁-PCL₁Thermosetting of diblock copolymersSAXS profile of the resin. It can be seen that in all cases a well-defined scattering peak appears in the scattering curve, indicating the formation of nanostructures in the thermoset blend. With PDMS₁-PCL₁With increasing content, the position of the primary scattering peak shifts slightly to a higher Q value, indicating that the average distance between adjacent regions decreases, because the content of the block copolymer increases. FIG. 7(b) shows PDMS with different contents₁-PCL₂SAXS profile of epoxy thermosets of block copolymers. The appearance of the scattering peak indicates that the diblock copolymer is microphase separated in the epoxy matrix. With PDMS₁-PCL₂The increase in diblock copolymer content from 5 wt% to 20 wt% significantly increased the intensity and number of scattering peaks, which means that the order of the nanostructures was improved. It is also noted that as the diblock copolymer content increases, the first order scattering peak shifts to a high Q value, indicating that the average distance between adjacent regions decreases. FIG. 7(c) (d) shows PDMS containing 5%, 10%, 20% and 40%₁-PCL₃And PDMS₁-PCL₄SAXS profile of the thermosetting resin of the diblock copolymer. In both systems, the corresponding SAXS curves look similar. It can be seen that the scattering curve shows a well-defined scattering peak in all cases, indicating the formation of nanostructures in the thermoset blend. When the content is less than 20 wt%, the epoxy thermosetting resin has a similar SAXS curve, and the appearance of a single scattering peak indicates that the thermosetting resin is microphase-separated, but the nanostructure is not ordered, and the primary scattering peak is hardly shifted. As the content further increased, the SAXS curve changed, with the first-order scattering peaks shifted towards high Q values, indicating that the average distance between adjacent regions decreased. Furthermore, the intensity and number of scattering peaks are significantly increased compared to the low content SAXS curve, which means that the order of the nanostructures is improved. These results are in good agreement with the results obtained by FESEM.

2.3 glass transition temperature of PDMS-b-PCL/EP System

Dynamic Mechanical Analysis (DMA) is adopted to characterize the epoxy resin containing two-block copolymer PDMS-b-PCL with different block ratios and different addition amounts to obtainTo the corresponding glass transition temperature. FIG. 8 is PDMS₁-PCL₁/EP、PDMS₁-PCL₂/EP、PDMS₁-PCL₃/EP、PDMS₁-PCL₄DMA curves for the/EP system. To system PDMS₁-PCL₁For the EP, the Tg is increased relative to pure epoxy at the addition levels of 5 wt%, 10 wt% and 20 wt%, and the increase amplitude is reduced with the addition level; at 40 wt% addition, the Tg decreased compared to the pure epoxy. To system PDMS₁-PCL₂For the EP, when the addition amount is 5 wt% and 10 wt%, the Tg is increased relative to pure epoxy, and the increase amplitude is slightly reduced along with the increase of the addition amount; at addition levels of 20 wt% and 40 wt%, the Tg decreased compared to the pure epoxy, and the magnitude of the decrease increased with increasing addition levels. To system PDMS₁-PCL₃[ EP ] and PDMS₁-PCL₄For EP, the Tg increases relative to pure epoxy when the amount is 5% by weight; at addition levels of 10 wt%, 20 wt% and 40 wt%, the Tg decreased relative to the pure epoxy, and the magnitude of the decrease increased with increasing addition levels.

FIG. 9 shows the values of glass transition temperatures for different systems. For the thermosetting resin containing PDMS-PCL block copolymer, the Tg tends to increase first and then decrease with the increase of the content, and when the content is 5 wt%, the Tg is higher than that of the pure epoxy resin.

2.4 fracture toughness

Measurement of the critical stress intensity factor (K) by three-point bending mode_IC) To characterize the fracture toughness of epoxy thermosets containing PDMS-PCL block copolymers. FIG. 10 shows K for a thermosetting resin_ICValues are plotted as a function of block copolymer content, and fig. 11 shows FESEM images of fracture surfaces close to pre-crack. It can be seen that K of all the thermosetting resins_ICHigher than that of pure epoxy resin, and shows that the PDMS-PCL segmented copolymer has toughening effect on the epoxy resin. K_ICThe value increases with increasing content of PDMS-PCL block copolymer. In particular for thermosetting resins containing worm-like nanostructures, K_ICThe value is obviously higher than that of pure epoxy resin when PDMS is used₁-PCL₄At a content of 40 wt.%, K_ICThe value is 3.83MPa · m^1/2Bipur ringOxygen resin (1.08 MPa. m)^1/2) The improvement is 255%. As the thermosetting resin containing spherical nanostructures, PDMS₁-PCL₂At a content of 40 wt%, K thereof_ICA value of about 1.53MPa m^1/2The content of the epoxy resin is higher than that of pure epoxy resin by 42 percent. It can be seen that the toughening effect of the worm-like nanostructure is much better than that of the spherical nanostructure.

2.5 wettability

Water contact angle measurements were performed on epoxy thermosets containing PDMS-PCL block copolymers and a photograph of a water drop on the surface of the sample is shown in fig. 12. For the contact angle of water, 90 ° is a threshold above which it is considered hydrophobic and below which it is considered hydrophilic. MOCA cured epoxy is hydrophilic in nature, but PDMS is hydrophobic in nature. FIG. 13 shows the contact angle values of the PDMS-PCL containing thermosets as a function of the block copolymer content. For all systems, the contact angle values rose first and then small scale fluctuations occurred, which were noted to be above 90 °. Neat epoxy resin showed a water contact angle of 70 deg. when PDMS is used₁-PCL₄At 5 wt% block copolymer, the water contact angle was about 99.4 °, 29.4 ° greater than that of the neat epoxy. Compared with the hydrophilic pure epoxy resin, the addition of the PDMS-PCL diblock copolymer enables the epoxy resin to be changed from hydrophilic to hydrophobic.

Example 2

The PDMS-PCL/EP composite material prepared in example 1 is used as a base resin, and a modifier commonly used in the fields of coating, electrical material, casting encapsulation material, adhesive, sealant, etc. is added to prepare the coating, the electrical material, the casting encapsulation material, the adhesive, and the sealant.

Comparative example 1 preparation and Performance test of PCL-b-PDMS-b-PCL/EP composite

Synthesis of 1 triblock copolymer PCL-b-PDMS-b-PCL

The preparation method is the same as that of the publication Heng Z, Li R, Chen Y, et al, preparation of mapping structural materials of the formation of nanostructured in triblock copolymer modified epoxy resins [ J ]. Journal of Polymer Research,2016,23(7):128.

Preparation of epoxy thermosetting resin containing PCL-b-PDMS-b-PCL triblock copolymer

The following weight of PCL-b-PDMS-b-PCL triblock copolymer and epoxy resin E-51 were mixed to a homogeneous state at 120 ℃ with vigorous stirring, then curing agent MOCA was added and again stirred to homogeneity with vigorous stirring. The obtained blend is degassed under vacuum state, and then poured into a polytetrafluoroethylene mold, the curing conditions are 150 ℃ for 2h, the curing is carried out at 180 ℃ for 2h, and the epoxy resin sample strip obtained after curing is transparent. The formulation of the added amount of each raw material is shown in table 5.

TABLE 5 formulation of PCL-b-PDMS-b-PCL/EP composites

3 fracture toughness test and results

The test method was the same as in example 1, and the test results are shown in FIG. 14. As can be seen from FIG. 14, K for all the thermosetting resins_ICHigher than pure epoxy resin, and K_ICThe value increases with the increase of the content of the PCL-b-PDMS-b-PCL triblock copolymer, and when the addition amount of the PCL-b-PDMS-b-PCL is 40%, the K of the composite material is_ICA value of 1.94MPa · m^1/2Comparative pure epoxy resin (1.08 MPa. m)^1/2) The improvement is 79.63%.

In conclusion, compared with pure epoxy resin, the toughness of the PDMS-PCL/EP composite material prepared by the invention is obviously enhanced: when PDMS₁-PCL₄At a content of 40 wt%, the fracture toughness of the thermosetting material with 10-60nm worm-like nano-structure is improved by about 255% compared with that of the pure epoxy resin, while the fracture toughness of the spherical nano-structure is improved by only 42% compared with that of the pure epoxy resin under the same addition amount. Compared with the PCL-b-PDMS-b-PCL/EP composite material, the PDMS-PCL/EP composite material prepared by the invention has the same addition amountThe toughness of the material is obviously superior to that of a PCL-b-PDMS-b-PCL/EP composite material, and the promotion amplitude reaches 97%. The toughness of the PDMS-PCL/EP composite material prepared in a specific proportion has obvious advantages, unexpected technical effects are achieved, and the PDMS-PCL/EP composite material can be used as a base material of coatings, electrical materials, pouring and packaging materials, adhesives and sealants and widely applied to the fields of aerospace, automobiles, shipbuilding, construction, railway transportation and the like.

Claims

1. The application of the block copolymer in preparing the high-toughness epoxy resin composite material is characterized in that: the block copolymer is a PDMS-b-PCL two-block copolymer;

the molecular weight ratio of PDMS to PCL in the PDMS-b-PCL diblock copolymer is 1: 4;

the epoxy resin is bisphenol A type epoxy resin;

the PDMS is polydimethylsiloxane with monohydroxy end capping;

the weight ratio of the block copolymer to the epoxy resin is 0.4: 1.

2. Use according to claim 1, characterized in that: the composite material is prepared from the following raw materials in parts by weight:

40 parts of epoxy resin, 16 parts of PDMS-b-PCL diblock copolymer and 16 parts of curing agent;

the curing agent is selected from 3,3 ' -dichloro-4, 4 ' -diaminodiphenylmethane, 4 ' -diaminodiphenyl sulfone and diaminodiphenylmethane; the epoxy resin is selected from E-51 and E-44.