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The characteristics and applications of alicyclic epoxy resins lie in the fact that the epoxide groups in their molecular structure do not originate from epichlorohydrin; rather, these epoxide groups are directly attached to the alicyclic rings. As a result, compared to bisphenol A-type epoxy resins, alicyclic epoxy resins possess the following characteristics: 1. Good thermal stability: Since the epoxide groups in alicyclic epoxy resins are directly connected to the alicyclic rings, a tight and rigid molecular structure is formed. This leads to a high degree of cross-linking after curing, thereby resulting in a high heat deformation temperature. The Martin heat resistance can exceed 190°C, while the heat decomposition temperature is above 360°C. It has low curing shrinkage and high tensile strength. However, due to its low epoxy equivalent and high cross-linking density, the cured product is relatively brittle and lacks toughness. 2. Good weather resistance: The molecular structure of alicyclic epoxy resins does not contain benzene rings, granting them excellent weather resistance and protection against ultraviolet radiation. 3. Excellent electrical insulation properties: Since the synthesis process does not involve elements such as chlorine or sodium, alicyclic epoxy resins possess good dielectric properties. Both in terms of specific resistance and dielectric loss tangent, they outperform bisphenol A-type epoxy resins. 4. Good processability: Aromatic epoxy resins have relatively low viscosities, which makes it easier to carry out casting and pressing operations. This is particularly important when processing large components. Furthermore, due to their low viscosity, alicyclic epoxy resins can also be used as excellent reactive diluents for epoxy resins. 5. High safety: Aromatic epoxy resins are more reactive toward organic acids and anhydrides than toward amines. Therefore, they can be fully cured using acidic curing agents. This avoids the use of highly toxic and volatile amine curing agents, making it safer for operators. Main uses of alicyclic epoxy resins: 1. As diluents, the alicyclic epoxides that can be used as reactive diluents include epoxy-269, 206, 201, and 221. Among them, epoxy 269 and 206 are both liquids with high boiling points and low viscosity; they remain in a liquid state even at -60°C, making them excellent diluents for epoxy resins. Furthermore, as the amount used increases, the viscosity of the epoxy system decreases significantly, but the heat distortion temperature remains almost constant, a feature that is unmatched by ordinary epoxy diluents. The effects of various diluents on the properties of the cured product are shown in Table 7. Epoxy 269 is a reactive diluent with two epoxy groups; after curing, it exhibits a high degree of cross-linking while retaining its original ring structure, which gives it a high heat resistance and good mechanical properties. 2. Organic insulators made from alicyclic epoxides have replaced ceramic materials in outdoor high-voltage equipment as the dielectric encapsulation material. Compared to ceramics, it has advantages such as light weight, small size, and good impact resistance, and it can be produced economically in a variety of sizes and shapes. Due to its excellent electrical properties and color stability, it can be used as a packaging material for light-emitting diodes. With the addition of polyol plasticizers, it is widely used in the potting of transformers, high-voltage coils, and various small electronic components. Such products can meet the requirements of good resistance to thermal shock, a high heat deformation temperature, and excellent critical electrical properties. 3. Aromatic epoxy resins for composite materials exhibit good heat resistance, mechanical properties, and weather resistance; in particular, they have low viscosity and a long pot life, making them particularly suitable for the production of high-strength, heat-resistant composite materials through wet laminating and winding processes. Glass fiber reinforced plastic laminates made from alicyclic epoxides have a dense structure after curing; they feature a high heat deformation temperature (above 300°C), excellent thermal stability and weather resistance, high impact strength, and good electrical insulation properties. 4. Aromatic epoxy compounds used in mold manufacturing can also serve as resin components in plastic molds. The resulting cured products exhibit good heat resistance, high mechanical strength, low volume shrinkage, and high precision, making them suitable for use in precision casting molds and other types of molds. Compared to metal molds, it has advantages such as ease of processing, lower cost, lighter weight, and better suitability for molding operations. Japanese patents describe the use of ZH92-21, aluminum powder, and methyl phthalic anhydride, along with catalysts, for stepwise curing in order to create vacuum forming molds, low-pressure casting molds, injection molding molds, blow molding and foaming molds with good thermal conductivity and high surface finish. 5. Aromatic epoxy resins, as adhesives, are unique in adhesive applications due to their ability to form strong chemical bonds with dirty surfaces or even oily metal surfaces, outperforming glycidyl ether-based epoxy resins in this regard. Adhesives made from ZH207 exhibit the following characteristic when bonding aluminum sheets: the bonding strength is moderate at room temperature, but it increases as the temperature rises gradually. 6. Aromatic epoxy compounds used in coatings also have distinct features. Coatings prepared using such resins as the base material can withstand high temperatures; for example, ZH68-01 can tolerate temperatures above 230°C, ZH206 can handle temperatures over 250°C, while ZH207 can resist temperatures up to 300°C. The alicyclic structure contributes to the surface resistance and leakage resistance of electrical coatings, which helps to maintain the color and durability of outdoor coatings. Coatings with excellent properties are obtained by the mixed cross-linking of alicyclic epoxies and resin containing alkoxy groups; these coatings can be used as topcoats, automotive primers, and in industrial coatings where relatively high film-forming properties are required. UV-curable coatings are gaining increasing attention due to their advantages such as fast curing, no need for high temperatures, no bubble formation, and excellent film gloss. These coatings, which are made primarily from alicyclic epoxies, possess excellent weather resistance, high hardness, wear resistance, impact resistance, chemical resistance, and good adhesion. They can be used as solder resist in printed circuit boards, as outer coatings for optical discs, and as protective coatings for metals and plastics. The use of epoxy resin in the production of handicrafts is well known. Epoxy resin has good workability and can be shaped using various methods such as sticking, coating, and pouring; therefore, it is an excellent material for creating handicrafts. It can be used to bond shells, glass, pebbles, and velvet together to create handicrafts in various shapes; it can be used to pour various plants and animals into molds of specific shapes to produce specimen-like handicrafts; it can also be poured into molds to create Buddha statues, animal figures, as well as handicrafts in the form of jade-like, bronze-like, or stone-like objects; it can be used to attach photos and drawings to handicrafts; and of course, epoxy resin paint can be used to draw on glass, porcelain, and stone surfaces. The formula for epoxy resin adhesives is quite simple; depending on the materials to be bonded, 6101 epoxy resin (or 634 epoxy resin), aliphatic amine curing agents, talcum powder, etc. can be used to create adhesives in liquid or paste form. Epoxy resin coatings require the addition of materials such as pigments and solvents to meet the requirements of the surface to be coated. The casting material used for pouring molded products should have its formula designed based on the transparency, color, hardness, curing conditions, and complexity of the mold shape of the product. Modification of Epoxy Resins 1. Overview Epoxy resins possess excellent comprehensive mechanical properties, high adhesion strength, low shrinkage rate, good stability, and outstanding electrical insulation characteristics. As coatings, adhesives, resin matrices for composite materials, and electronic packaging materials, they are widely used in various fields such as machinery, electronics, electrical appliances, aerospace, aviation, coatings, and bonding. However, due to the high cross-linking density and large internal stress of the cured epoxy resin, it has disadvantages such as brittleness, poor fatigue resistance, low heat resistance, and weak impact toughness, which makes it difficult to meet the requirements of engineering applications and thus limits its use. In particular, this has restricted the use of epoxy resins in composite materials of the type used for structural applications. As a result, scholars at home and abroad have conducted extensive research on modifying epoxy resins. Among these, the most important is to improve the brittleness and moisture and heat resistance of epoxy resins. Epoxy resins can be modified through chemical methods and physical methods. Chemical modification mainly involves the synthesis of epoxy resins with new structures and curing agents with new structures; physical modification aims to improve performance by forming a blended structure with modifiers. When comparing the two methods, the first method is at a disadvantage to the second in terms of process, cost, and ease of implementation. Therefore, the modification of epoxy resins is currently mainly achieved through blending structures. There are mainly three approaches to toughening epoxy resins: ① Toughening is achieved by forming a two-phase structure using rigid inorganic fillers, rubber elastomers, and thermoplastic polymers. ②Thermoplastic plastics are continuously incorporated into the epoxy resin network to form a semi-interpenetrating network polymer for toughening and modification. ③The mobility of the cross-linked network is improved by altering the chemical structure composition of the cross-linked network (such as introducing \"flexible segments\" into it). The improvement in the moisture and heat resistance of epoxy resins is achieved mainly by introducing polycyclic structural units into the epoxy resin molecules and by synthesizing fluorine-containing epoxy resins, as well as by using new curing agents in place of traditional DDSs. The modified epoxy resin, thanks to its improved resistance to moisture and heat as well as enhanced toughness, will further expand the applications of epoxy resins in electronic and electrical products, load-bearing components in composite materials, and high-performance structural adhesives. On the other hand, although epoxy resins have good processability, their handling procedures need to be appropriately modified for different applications. Resins of the diphenylpropane type, for example, have high viscosity and poor processability in certain operations; therefore, diluents need to be added to the curing system to reduce viscosity and improve the processability. Therefore, to meet various applications, different additives such as diluents, fillers, and reinforcing agents need to be added. Regulation of epoxy resin fluidity: The fluidity of epoxy resin compounds is very important for applications such as coatings, linings, and casting. To meet these requirements, it is necessary to reduce the viscosity, or increase it, or endow it with thixotropy; the composite materials that can fulfill these requirements are known as flow regulators.