CN109734854B

CN109734854B - Block copolymer capable of spontaneously constructing specific nanostructure in epoxy resin and application of block copolymer in high performance of epoxy resin

Info

Publication number: CN109734854B
Application number: CN201811429182.9A
Authority: CN
Inventors: 邹华维; 陈洋; 衡正光; 张浩若; 李霂萱; 梁梅
Original assignee: Sichuan University
Current assignee: Sichuan University
Priority date: 2018-11-27
Filing date: 2018-11-27
Publication date: 2022-02-08
Anticipated expiration: 2038-11-27
Also published as: CN109734854A

Abstract

The invention provides a block copolymer capable of spontaneously constructing a specific nano structure in epoxy resin and application thereof in high performance of the epoxy resin. Experimental results show that the BXLS segmented copolymer forms a novel paramecium-like nanostructure in the epoxy resin, so that the BXLS/epoxy resin composite material prepared by the invention realizes the remarkable increase of material toughness under the condition of extremely low addition of the BXLS segmented copolymer, has excellent mechanical properties, and greatly widens the application field of the epoxy resin.

Description

Block copolymer capable of spontaneously constructing specific nanostructure in epoxy resin and application of block copolymer in high performance of epoxy resin

Technical Field

The invention belongs to the field of polymer composite materials, and particularly relates to a block copolymer capable of spontaneously constructing a specific nano structure in epoxy resin and application thereof in high performance of the epoxy resin.

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.

Disclosure of Invention

The invention aims to provide a block copolymer (BXLS block copolymer) capable of spontaneously constructing a specific nano structure in epoxy resin and application thereof in high performance of the epoxy resin, wherein the molecular weight ratio of BX-OH to PCL and PS in the BXLS block copolymer is 1: 1.16: 1.43.

preferably, the BX-OH is a monohydroxy-terminated polydimethylsiloxane.

Preferably, the preparation of the block copolymer comprises the steps of:

BX-OH initiates epsilon-caprolactone to open ring and polymerize, and then an atom transfer radical polymerization method is used for synthesizing the BXLS block copolymer.

The invention also provides application of the BXLS segmented copolymer in construction of paramecium-like nano structures in epoxy resin and preparation of high-toughness epoxy resin composite materials.

Preferably, the composite material is prepared from the following raw materials in parts by weight: 50 parts of epoxy resin, 20 parts of curing agent, 1.25-20 parts of BXLS segmented copolymer,

preferably, the composite material is prepared from the following raw materials in parts by weight: 50 parts of epoxy resin, 20 parts of curing agent, 1.25-5 parts of BXLS segmented copolymer,

preferably, the composite material is prepared from the following raw materials in parts by weight: 50 parts of epoxy resin, 20 parts of curing agent, 1.25-2.5 parts of BXLS segmented copolymer,

preferably, the composite material is prepared from the following raw materials in parts by weight: 50 parts of epoxy resin, 20 parts of curing agent and 2.5 parts of BXLS block copolymer.

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

Preferably, the preparation of the composite material comprises the following steps:

weighing the epoxy resin and the BXLS segmented copolymer according to the weight ratio, uniformly mixing, adding the curing agent, uniformly mixing again, removing bubbles in vacuum and curing.

The invention also provides application of the high-toughness epoxy resin composite material in preparation of a matrix material.

Preferably, the composite material is prepared from the following raw materials in parts by weight: 50 parts of epoxy resin, 20 parts of curing agent and 1.25-20 parts of BXLS block copolymer;

preferably, the composite material is prepared from the following raw materials in parts by weight: 50 parts of epoxy resin, 20 parts of curing agent and 1.25-5 parts of BXLS block copolymer;

preferably, the composite material is prepared from the following raw materials in parts by weight: 50 parts of epoxy resin, 20 parts of curing agent and 1.25-2.5 parts of BXLS block copolymer;

preferably, the composite material is prepared from the following raw materials in parts by weight: 50 parts of epoxy resin, 20 parts of curing agent and 2.5 parts of BXLS block copolymer;

preferably, the BXLS block copolymer has a molecular weight ratio of BX to PCL and PS of 1: 1.16: 1.43;

preferably, BX is a monohydroxy-terminated polydimethylsiloxane; the epoxy resin is bisphenol A type epoxy resin, preferably, the epoxy resin is selected from E-51 and E-44; the curing agent is selected from 3,3' -dichloro-4, 4' -diaminodiphenylmethane, 4' -diaminodiphenyl sulfone, and diaminodiphenylmethane.

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

Experimental results show that the BXLS segmented copolymer forms a novel paramecium-like nanostructure in the epoxy resin, so that the BXLS/epoxy resin composite material prepared by the invention realizes the remarkable increase of material toughness under the condition of extremely low addition of the BXLS segmented copolymer, has excellent mechanical properties, and greatly widens the application field of the epoxy resin.

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 is a size diagram of a mechanical property test specimen, (a) is a tensile property test specimen, and (B) is a fracture toughness test specimen, S is a test span, P is a load, B is a specimen thickness, W is a specimen width, and A is a crack depth.

FIG. 2 shows GPC curves of the starting BX-OH, intermediate BXL and block copolymer BXLS.

FIG. 3 is a block copolymer BXLS¹HNMR spectrogram.

FIG. 4 is a TEM photograph of epoxy resin containing different block copolymer addition amounts, the block copolymer addition amount in a and a' being 1.75 wt%; the amount of block copolymer added in b and b' was 6.67 wt%; the block copolymer in c and c' was added in an amount of 22.22 wt%.

FIG. 5 is a plot of SAXS for epoxy resins with different block copolymer addition levels.

FIG. 6 is a SAXS curve before and after curing of an epoxy resin containing 6.67 wt% BXLS block copolymer.

FIG. 7 is a FESEM photograph of an epoxy resin containing 6.67 wt% BXL block copolymer.

FIG. 8 is a graph representing tensile properties of epoxy resins containing different amounts of block copolymer added.

FIG. 9 is a graphical representation of fracture toughness for epoxy resins containing different amounts of block copolymer added.

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 materials and reagents

BX-OH: polydimethylsiloxane, Nippon Denshi chemical industry Co., Ltd., product number X-22-107BX (R and R' in the structural formula are short hydrocarbon chain-terminated units, for example, butyl (R-: CH)₃-CH₂-CH₂-CH₂-), ethyl (-R' -: -CH₂-CH₂-) however the manufacturer does not give a specific structural formula). Caprolactone, polystyrene, dibromo isobutyryl bromide, stannous octoate, etc. are all chemically pure and purchased from Shanghai Allantin Biotechnology GmbH. EP: bisphenol a epoxy resin (E51), phoenix brand epoxy resin, model WSR618(E51), southernwood star finished materials ltd. Chroma: 40Pt-Co or less, epoxy equivalent: 184-195 g/mol, hydrolysis chlorine: less than or equal to 0.2 percent, 50mg/kg, volatile matter: 0.5%, viscosity (25 ℃): 10000-16000 mPa.s. 4,4 '-diamino-3, 3' -dichlorodiphenylmethane (MOCA): industrial grade, febrile bell chemical ltd.

2 experimental part

2.1 Synthesis of Block copolymer BX-b-PCL (BXL-OH)

The block copolymer PDMS-PCL is synthesized by stannous octoate [ Sn (Oct)₂]The catalyst is obtained by initiating the ring-opening polymerization of caprolactone (. epsilon. -CL) by hydroxyl-terminated polydimethylsiloxane (BX-OH). The procedure was first followed by azeotropic removal of BX-OH (15g,3.83mmol) and dry toluene (20ml) in a 250ml anhydrous oxygen-free flask, distilling off excess toluene, and then reacting ε -CL (19.15g,167.98mmol) and Sn (Oct)₂(the amount of ε -CL added was 1 wt% o) was added to the purified BX. After three cycles of liquid nitrogen freezing, vacuum degassing and unfreezing, the flask is placed into a constant temperature oil bath at 120 ℃ under the negative pressure state and stirred for reaction for 36 hours. After the reaction is finished, the crude product is dissolved in a proper amount of dichloromethane solution, and then a large amount of frozen methanol is added for precipitation and filtration. This dissolution-precipitation-filtration process was repeated three times to remove any side products possibly present in the systemProduct and residual monomer. The purified product was dried in a vacuum oven at 30 ℃ to constant weight.

2.2 Synthesis of macroinitiator BX-b-PCL-Br (BXL-Br)

BXL-OH prepared by the method reacts with 2-bromoisobutylacyl bromide (2-BiB) in purified and dried Dichloromethane (DCM) in the presence of Triethylamine (TEA) and a catalyst of 4-Dimethylaminopyridine (DMAP) to synthesize a macroinitiator BXL-Br. The specific process is as follows: a solution of TEA (480mg, 4.74mmol), BXL-OH (20g, 2.37mmol) and DMAP (869mg, 7.11mmol) in DCM (200ml) was added to a three-necked round bottom flask and mixed well with stirring under an argon and ice bath. 2-BiB (2.49g, 11.85mmol) was dissolved in 50ml of DCM and added to the mixture via a constant pressure funnel under ice bath, and after the addition was complete the reaction was stirred at room temperature for 24 h. After the reaction is finished, the solution is subjected to rotary evaporation to remove half of the solvent, and the residual product is dropwise added into the frozen methanol for precipitation and filtration. This dissolution-precipitation-filtration process was repeated three times and the purified product was dried to constant weight in a vacuum oven at 30 ℃.

2.3 Synthesis of Block copolymer polydimethylsiloxane-polycaprolactone-polystyrene BX-b-PCL-b-PS (BXLS)

The BXLS segmented copolymer is obtained by atom transfer radical polymerization by taking cuprous bromide (CuBr) as a catalyst, N, N, N' -Pentamethyldiethylenetriamine (PMDETA) as a coordination agent and the product as a macromolecular initiator. The synthesis procedure is described as follows: a macroinitiator (BXL-Br, 17.2g,2mmol), a styrene monomer (9.47g,91.06mmol), CuBr (340mg) and PMDETA (990 μ L) were sequentially added to a 250ml anhydrous oxygen-free flask, stirred uniformly, and after three cycles of liquid nitrogen freezing-vacuum degassing-thawing, the flask was placed in an oil bath at 110 ℃ under negative pressure and magnetically stirred for 24 hours. After the reaction is finished, the product is exposed to air and cooled to room temperature to stop the reaction. The product was dissolved in dichloromethane and passed through a neutral alumina column to remove the catalyst. The concentrated solution was rotary evaporated and dropped dropwise into a large amount of frozen methanol to precipitate, and filtered. After three dissolution-precipitation-filtration processes, the final product was dried to constant weight in a vacuum oven at 30 ℃.

2.4 preparation of BXLS/epoxy resin composite Material

Adding the synthesized block copolymer into epoxy prepolymer (DGEBA), violently stirring at 120 ℃ until a uniform solution is formed, adding curing agent MOCA into the system, and uniformly mixing. And (3) putting the obtained blending solution into a 110 ℃ vacuum oven to remove air bubbles in the system, then pouring the blending solution into a polytetrafluoroethylene mold, curing for 2 hours at 150 ℃, and then heating to 180 ℃ for curing for 2 hours. And (3) after the curing reaction is finished, demolding to obtain the epoxy thermosetting resin containing the block copolymer. The sample numbers and compositions are shown in Table 1.

TABLE 1 formulation of BXLS/epoxy composites

Secondly, detecting the performance of the composite material

1 testing and characterization

1.1 Gel Permeation Chromatography (GPC)

Molecular weight tests were carried out on the starting materials and the synthesized product at 30 ℃ using a Waters1515 model gel permeation chromatograph of Waters corporation, USA, with tetrahydrofuran as a mobile phase at a flow rate of 0.5. mu.L/min and polystyrene as a standard.

1.2 Nuclear magnetic resonance Hydrogen Spectroscopy (NMR)

A400 MHz nuclear magnetic spectrum is obtained at 25 ℃ by adopting a DRX-400 nuclear magnetic resonance spectrometer of Bruker company of Germany and deuterated chloroform as a solvent.

1.3 Transmission Electron Microscopy (TEM)

And (3) slicing the sample at-120 ℃ by using a low-temperature ultra-thin slicer of Lieka UC7 to obtain a sample with the thickness of 100-150 nm. After the ruthenium tetroxide is fumigated at normal temperature for 15min, the observation is carried out on a Tecnai G2F20 type transmission electron microscope, the low electron beam current is less than 10mA, and the acceleration voltage is 120 keV.

1.4 Small Angle X-ray Scattering (SAXS)

Small-angle X-ray scattering measurements were performed on samples using a Xeuss 2.0SAXS/WAXS equipped with a PILATUS 3R 300K detector and thermal stage from Xenocs, FranceAt an X-ray wavelength of

50kV, 0.6mA, and the exposure time is 10 min.

1.5 Field Emission Scanning Electron Microscope (FESEM)

The method comprises the steps of firstly carrying out brittle fracture on a sample in liquid nitrogen, carrying out gold spraying treatment on a brittle fracture surface in vacuum, and carrying out microstructure characterization on the sample by adopting a Nova NanoSEM 450 type field emission scanning electron microscope of FEI company in America, wherein the acceleration voltage is 5 kV.

1.6 tensile and crack toughness test

The tensile and fracture toughness tests were performed on the bars using an Instron 5567 Universal Material testing machine, the dimensions of the bars being shown in FIG. 1. The tensile property test speed is 2 mm/min. The fracture toughness of the test specimens was measured according to ASTM D5045 standard, and the fracture toughness of the test specimens was calculated from the following formula at a test rate of 2 mm/min.

2 results and discussion

2.1 synthetic characterization of Block copolymers

As can be seen from FIG. 2, the molecular weights of BX-OH, BXL and BXLS are 3915 (M)_w/M_n＝1.06)，8449(M_w/M_n1.24) and 14034 (M)_w/M_n1.06). The molecular weight ratio of BX-OH, PCL and PS in BXLS is 3915 through calculation: 4534: 5585.

as can be seen from FIG. 3, the synthesized block copolymer has the structural characteristics of BX-OH, PCL and PS.

2.2 microstructural characterisation

According to the dyeing principle, the colors of the TEM picture are PS, the epoxy resin matrix and the BX-OH-rich phase from dark to light respectively. As can be seen from the TEM photograph of fig. 4, the block copolymer is distributed in the epoxy resin matrix in a caterpillar-like form, the internal spherical structure is a PDMS-rich aggregate phase, and a tubular "flagella" structure having "PS as a shell and PDMS as a core" is formed around the internal spherical structure. Meanwhile, the paramecium-like structures are all core-shell-corona (C-S-C) structures with PDMS as a core, PS as a shell and PCL as corona. As the content of the block copolymer increases, the morphology of the nanostructures does not change, but the size of the nanostructures increases. When the amount added is 1.75 wt%, the diameters of the spherical PDMS-rich phase and the entire microstructure are 120nm and 280nm, respectively. The addition amount is 6.67 wt%, and the diameters of the spherical PDMS-rich phase and the whole microstructure are 250nm and 550nm respectively. The SAXS test of FIG. 5 further demonstrates the TEM results that the SAXS curve is found after the block copolymer is incorporated into the epoxy resin

A distinct scattering peak was observed indicating the presence of the nanostructure of the block copolymer in the epoxy resin. According to the Bragg formula (L is 2 pi/Q), the average distance between the nanostructures corresponding to the scattering peak can be calculated to be 16.11 nm. In conjunction with TEM photographs, the scattering peaks in SAXS curves should be assigned to "flagellum" structures.

2.3 microstructure formation Process study

FIG. 6 is a SAXS curve before and after curing of an epoxy resin containing 6.67 wt% BXLS block copolymer. To further study the morphology of the nanostructure at this stage, we synthesized BXL diblock copolymer with the same molecular weight as BXLS by using the same BX-OH and introduced it into epoxy resin for curing, and the microscopic morphology is shown in FIG. 7, and PDMS forms spherical dispersed phase in epoxy resin. Thus, for the BXLS/EP system, the BXLS first self-assembles to form a spherical PDMS phase before the epoxy resin cures. With the curing of the epoxy resin, the PS segment begins to react to induce microphase separation, which results in that the spherical PDMS phase formed at the earlier stage cannot exist stably, the nanostructure is locally rearranged, and meanwhile, the PCL segment back is fixed in the cross-linked network of the epoxy resin to form a halo, and the SAXS curve after curing is shown in fig. 6.

2.4 tensile Property test

As can be seen from FIG. 8, the tensile strength and elongation at break of the pure epoxy resin were 71.3MPa and 4.4%, respectively. When the addition amount of the block copolymer was only 1.75% by weight, the tensile strength reached a maximum of 93.6MPa, which was 1.31 times that of the epoxy resin. The elongation at break of the material reaches the maximum value when the addition amount is 3.45 wt%, and is 1.84 times of that of the epoxy resin, and the elongation at break is not changed after the addition amount of the block copolymer is further increased and is slightly reduced.

2.5 fracture toughness test

As can be seen from FIG. 9, the fracture toughness and the elongation at break of the material have the same change tendency as the addition amount of the block copolymer increases. The fracture toughness of the pure epoxy resin is 47N/mm^3/2. When the content of the block copolymer is only 1.75 wt%, the fracture toughness of the material is obviously improved, and the fracture toughness is 137.4N/mm^3/2(2.92 times of pure epoxy resin). When the addition amount is 3.45 wt%, the fracture toughness of the material reaches a maximum value, which is 3.2 times of that of the pure epoxy resin. Compared with the prior art, the preparation method can realize the obvious increase of the toughness of the material under the condition of extremely low addition of the block copolymer, and has obvious advantages.

Example 2

The BXLS/EP composite material prepared in example 1 is used as a matrix resin, and a modifier commonly used in the fields of coatings, electrical materials, casting encapsulation materials, adhesives, sealants and the like is added to prepare the coatings, the electrical materials, the casting encapsulation materials, the adhesives and the sealants.

In conclusion, the BXLS block copolymer forms a caterpillar-like novel nano structure in the epoxy resin, so that the BXLS/epoxy resin composite material prepared by the invention realizes the remarkable increase of material toughness under the condition of extremely low addition of the BXLS block copolymer, has excellent mechanical properties, and greatly widens the application field of the epoxy resin.

Claims

The application of the BXLS block copolymer in improving the toughness of the epoxy resin composite material is characterized in that: the BXLS segmented copolymer constructs a paramecium-like nano structure in epoxy resin, wherein the paramecium-like nano structure is a core-shell-corona structure with PDMS as a core, PS as a shell and PCL as corona; the molecular weight ratio of BX-OH to PCL and PS in the BXLS segmented copolymer is 1: 1.16: 1.43; the BX-OH is monohydroxy terminated polydimethylsiloxane; the preparation of the block copolymer comprises the following steps: b X-OH initiates epsilon-caprolactone to open ring and polymerize, then the BXLS segmented copolymer is synthesized by an atom transfer radical polymerization method; the epoxy resin composite material is prepared from the following raw materials in parts by weight: 50 parts of epoxy resin, 20 parts of curing agent and 1.25-20 parts of BXLS block copolymer; the curing agent is selected from

3,3' -dichloro-4, 4' -diaminodiphenylmethane, 4' -diaminodiphenylsulfone, diaminodiphenylmethane; the epoxy resin is selected from E-51 and E-44.
2. Use according to claim 1, characterized in that: the composite material is prepared from the following raw materials in parts by weight: 50 parts of epoxy resin, 20 parts of curing agent and 1.25-5 parts of BXLS block copolymer.
3. Use according to claim 2, characterized in that: the composite material is prepared from the following raw materials in parts by weight: 50 parts of epoxy resin, 20 parts of curing agent and 1.25-2.5 parts of BXLS block copolymer.
4. Use according to claim 3, characterized in that: the composite material is prepared from the following raw materials in parts by weight: 50 parts of epoxy resin, 20 parts of curing agent and 2.5 parts of BXLS block copolymer.
5. Use according to claim 1, characterized in that: the preparation of the composite material comprises the following steps: weighing the epoxy resin and the BXLS segmented copolymer according to the weight ratio, uniformly mixing, adding the curing agent, uniformly mixing again, removing bubbles in vacuum and curing.
6. The application of the high-toughness epoxy resin composite material in preparing the matrix material is characterized in that: the composite material is prepared from the following raw materials in parts by weight: 50 parts of epoxy resin, 20 parts of curing agent and 1.25-20 parts of BXLS block copolymer; the molecular weight ratio of BX-OH to PCL and PS in the BXLS segmented copolymer is 1: 1.16: 1.43; the BX-OH is monohydroxy terminated polydimethylsiloxane; the epoxy resin is selected from E-51 and E-44; the BXLS segmented copolymer constructs a paramecium-like nano structure in epoxy resin, wherein the paramecium-like nano structure is a core-shell-corona structure with PDMS as a core, PS as a shell and PCL as corona; the curing agent is selected from 3,3' -dichloro-4, 4' -diaminodiphenylmethane, 4' -diaminodiphenyl sulfone and diaminodiphenylmethane; the preparation of the block copolymer comprises the following steps: BX-OH initiates epsilon-caprolactone to open ring and polymerize, and then an atom transfer radical polymerization method is used for synthesizing the BXLS block copolymer.
7. Use according to claim 6, characterized in that: the composite material is prepared from the following raw materials in parts by weight: 50 parts of epoxy resin, 20 parts of curing agent and 1.25-5 parts of BXLS block copolymer.
8. Use according to claim 6, characterized in that: the composite material is prepared from the following raw materials in parts by weight: 50 parts of epoxy resin, 20 parts of curing agent and 1.25-2.5 parts of BXLS block copolymer.
9. Use according to claim 6, characterized in that: the composite material is prepared from the following raw materials in parts by weight: 50 parts of epoxy resin, 20 parts of curing agent and 2.5 parts of BXLS block copolymer.
10. Use according to claim 6, characterized in that: the preparation of the composite material comprises the following steps: weighing the epoxy resin and the BXLS segmented copolymer according to the weight ratio, uniformly mixing, adding the curing agent, uniformly mixing again, removing bubbles in vacuum and curing.
11. Use according to claim 6, characterized in that: the base material is a base material of paint, electrical material, pouring packaging material, adhesive and sealant.