Compound modification technology for epoxy resin application

Abstract: Epoxy resins and curing agents have been modified by physical methods or chemical methods to increase the varieties of epoxy resins and meet practical application requirements. Compound modification technology is one of the important contents of epoxy resin application technology. Compound modification technology is characterized by cross-infiltration, superimposition, improved performance, and innovative products that are involved in compound modification of the base material. The application practice shows that the compound modification technology has updated the application concept of epoxy resin, added the technical content of the epoxy system product, and expanded the application field of epoxy resin. This article focuses on epoxy resin compounding, epoxy resin and other resin compounding, epoxy resin toughening and reinforcement, epoxy resin and acrylate monomer copolymerization reaction, amine curing agent compound, amine and phenolic Resin compounding, aromatic amine eutectic and eutectic melting etc.
Keywords: epoxy resin curing agent compound modification technology Currently, the concept of epoxy resin application technology is undergoing profound changes, the traditional concept of epoxy resin curing properties (such as adhesion, insulation and low shrinkage, etc.), curing The function of the agent and the curing speed are impacted by the new application concept. The new concept of epoxy resin application has opened up new ideas for people, expanded the new fields of epoxy resin application, and promoted the new development of epoxy resin application technology.
Epoxy resin application compound modification technology can update the application concept of epoxy resin, increase the technical content of epoxy system, explore the new characteristics of epoxy resin system materials, and expand the new market of epoxy resin system products. In general, a bisphenol A epoxy resin cured material has a high crosslink density, a large internal stress, and poor flexibility, fatigue resistance, heat resistance, and weather resistance. Therefore, the epoxy resin and curing agent should be compounded and modified by physical or chemical methods in order to more prominently demonstrate the new characteristics of the epoxy resin system product, so that it can achieve satisfactory application results. This article focuses on the part of the compound modification technology and application examples that have achieved practical application for reference.
1. Modification of Epoxy Resins 1.1. Physical Modifications 1.1.1. Epoxy Resin Epoxy Resin Epoxy Resin (Varnish) can be made of two or more different molecular weights. Epoxy resin compounding gives the so-called relative molecular weight distribution "double peak" or "multimodal" type epoxy resin glue. Epoxy resin with low molecular weight is good for improving permeability in compounded epoxy resin glue, and epoxy resin with high molecular weight is good for controlling fluidity during hot pressing. Improve the process operability of glue and meet the product's usability.
1.1.2. Epoxy coating base materials When designing epoxy coating formulations, different molecular weight bisphenol A epoxy resins are often compounded to form a mixed base; bisphenol A type epoxy resin and aliphatic Epoxy resin compounded into a mixture of base materials, improve product flexibility and weather resistance; sometimes in the epoxy resin component added electrophilic additives to improve the coating of the construction and use.
1.1.3. Epoxy resin and unsaturated polyester resin, vinyl ester resin, phenolic resin, furan resin, amino resin, acrylic resin, alkyd resin, polyvinyl butyral and coal tar, etc. For compound modification, good application results have been obtained. For example, the epoxy coal tar mixed base compound modified by physical methods takes into consideration the characteristics of epoxy resin and coal tar, and the coating has excellent anti-corrosion effect. In general, one of the other resins added to the epoxy resin may account for 30% to 60% of the total amount of the compound-modified resin.
Epoxy resin - amino resin - acrylic resin compounded into a ternary system varnish, its composition and the performance of the formation of coating film in Table -l and Table -2.
Table-1 Composition and Mechanical Properties of Ternary System Varnish [Note]

-
Formula 1
Formula 2
Recipe 3
Formula 4

Composition -
-
-
-

E-44 Epoxy Resin 22
twenty two
17
13

Acrylic resin 46
56
56
60

Amino resin solution 32
twenty two
27
27

Mechanical behavior -
-
-
-

Impact resistance/N·cm
441
490
441
490

Flexibility/mm
/
/
/
/

Adhesion/level/
/
/
/

Note: Without catalyst, curing conditions are 180±5°C/10min
Table-2 Chemical Resistance of Ternary System Clear Films

Item Test result Item Test result
10% saline soak 15d
No change 120× gasoline soaked for 15 days
No change
Soaked in 5% hydrochloric acid for 15 days
No change Soybean Oil Soak 15d
No change
Soaked in acetic acid for 15 days
No change Canola oil soak 15
No change
10% sodium hydroxide soak 15d
No change Boil 8h
No change
Industrial alcohol soak 2d
The film is slightly soft soaked in toluene for 2 days
The film is slightly soft

The ternary varnish compounded by the epoxy resin-amino resin-acrylic resin has excellent mechanical properties, ester-alkali resistance and boiling water resistance. However, the crosslink density of the coating should be increased to improve its solvent resistance.
1.1.4. New breakthroughs have been made in the toughening of epoxy resins and in the enhancement of toughening and reinforcing compounding of epoxy resins. New types of applications have been introduced for epoxy systems, new markets have been opened up, and resin applications for rings have been promoted. New developments in technology. Toughened or reinforced epoxy system products have become the dominant material in many fields, fully demonstrating the vitality of compound modification technology.
Toughening agent is a compound (or polymer) that can cross-link curing reaction with epoxy resin or curing agent. The toughness, elongation at break and flexibility (elasticity) of the cured product are obviously improved and improved.
According to the application technical requirements, the types and amounts of tougheners are properly selected, and scientific and rational compounding techniques can be used to produce a variety of epoxy series products that have excellent performance and meet application requirements. For example, take 100 parts of E-51 epoxy resin, carboxyl butyronitrile-2l, 35 parts and 10 parts of 2-methyl-4-ethylimidazole to form a nitrile rubber toughened epoxy glue. When steel-steel is bonded, the shear strength at room temperature is 46.5 MPa after curing at 120°C/3h. If adhesion promoters are added to the nitrile rubber-toughened epoxy system, the bond strength to ABS and other plastics can be significantly improved.
In addition to the above-mentioned toughening agents, toughening materials such as rigid inorganic fillers or thermoplastic polymers may be added to the epoxy system, and toughening effects may also be achieved on epoxy cured products.
Enhancers can increase the strength properties of epoxy cured products. Reinforcing agents (or reinforcing materials) used in epoxy resins are mainly fibers, whiskers and reinforcing fillers are sometimes used. The use of glass fibers, carbon fibers and organic fibers can significantly increase the strength properties of epoxy materials.
The composite material composed of various fibers and epoxy resin has the characteristics of low density, high fatigue strength, excellent vibration damping properties, corrosion resistance, dielectric properties, electromagnetic wave permeability, and heat resistance. At the same time, the composite material has anisotropy and designability of the material properties.
Table-3 Performance Comparison of Several Engineering Materials

Material Name Density/g·cm-3
Tensile strength/GPa
Tensile modulus/×102GPa
Specific strength/MN·m·kg-1
Specific modulus/MN·m·kg-1

Steel 7.8
1.03
2.1
0.13
27

Aluminum Alloy 2.8
0.47
0.75
0.17
27

Titanium Alloy 4.5
0.96
0.14
0.21
25

Glass Fiber Composite 2.0
1.06
0.4
0.53
20

High-strength carbon fiber/epoxy composite 1.45
1.5
1.4
1.03
97

High-modulus carbon fiber/epoxy composite 1.6
1.07
2.4
0.67
150

Aramid Fiber/Epoxy Composite 1.4
1.4
0.8
1.00
57

Boron Fiber/Epoxy Composites 2.1
1.38
2.1
0.66
100

Boron Fiber/Aluminum Composites 2.65
1.0
2.0
0.38
57

The mechanical properties of composites made of glass fiber, carbon fiber and aramid fiber (also known as Kevlar fiber) and epoxy resin are shown in Table-4.
Table-4 Comparison of mechanical properties of several fiber reinforced epoxy resin unidirectional composites

Project Kevlar-49
E Glass Fiber T-300 Carbon Fiber
Fiber volume content/%
60
60
60

0o tensile strength/MPa
1.38
2.05
1.55

0o tensile strength/MPa
1380
1100
1240

0o tensile modulus/GPa
72.4
39.3
131

Elongation at break/%
1.8
2.8
1.11

Poisson's ratio 0.34
0.3
0.25

0o compressive strength/Mpa
276
586
1100

0o compression modulus/Gpa
72.4
39.3
131

90o tensile strength/Mpa
27.6
34.5
411.4

90o tensile modulus/Gpa
5.5
8.96
6.2

90o compressive strength/Mpa
138
138
138

90o compression modulus/Gpa
5.5
8.96
6.2

In-plane shear strength/Mpa
44.7