In-depth analysis of mainstream curing agent categories and representative models in the market.
In fields such as coatings, adhesives, and composite materials, curing agents act as unsung heroes, directly determining key properties of the final product, including hardness, weather resistance, chemical resistance, and mechanical strength. With the wide variety of curing agents available on the market, choosing the right type is crucial. This article will objectively analyze the advantages and disadvantages of various mainstream curing agent categories and their representative models based on current market conditions, helping you make informed decisions.
Analysis of Mainstream Curing Agent Categories
- Isocyanate Curing Agent Principle: Contains active -NCO groups, which undergo addition polymerization reactions with compounds containing active hydrogen groups (-OH, -NH2, -COOH, etc.) (such as polyols and amine chain extenders). Commonly used in polyurethane systems, such as two-component polyurethane coatings, adhesives, and elastomers. Advantages: Fast curing speed (especially wet curing in the presence of moisture); excellent film performance, outstanding hardness, wear resistance, elasticity, and chemical resistance (especially oil and solvent resistance); good adhesion to various substrates (metals, plastics, rubber, wood); wide design range (from rigid to highly elastic). Disadvantages: Isocyanate monomers are toxic and irritating (the content of free monomers such as MDI/TDI needs to be strictly controlled); extremely sensitive to moisture, easily causing bubbles and affecting performance; solvent-based products usually contain high VOCs (volatile organic compounds); the application window (pot life) needs to be strictly controlled. Representative companies and models: Covestro: Desmodur N (aliphatic HDI trimer/biuret, such as N3300, N3600), Desmodur L (aliphatic/alicyclic isocyanate, such as L75 TDI/trimethylolpropane adduct). BASF: Basonat series (HDI/LPDI/IPDI trimers, etc.). Wanhua Chemical: Wannate HDI trimer series (such as HT-100, HT600), Wannate MDI series. Evonik: Vestanat IPDI (isophorone diisocyanate) and its derivatives.
Hefei Konada (Our company):
CR-G118 Water-based isocyanate curing agent (comparable to Covestro 305, Wanhua HT-600)
Amine curing agents (primarily used for curing epoxy resins)
Principle: Amine groups (-NH2, -NH-) attack the epoxy group, undergoing ring-opening addition polymerization. Widely used in epoxy resin coatings, adhesives, sealants, and composite materials. Advantages: Relatively fast curing speed (aliphatic amines are very fast, polyamides are moderate); good overall performance: excellent adhesion, chemical resistance (especially acid, alkali, and solvent resistance), hardness, and insulation; abundant low/room temperature curing systems (no high-temperature energy consumption required); mature water-based technology (low VOC). Disadvantages: Irritating odor and skin sensitization (particularly severe for some aliphatic amines); prone to amine blushing or incomplete curing under low temperature/high humidity conditions; some types (such as aromatic amines) may be prone to yellowing (affecting outdoor weather resistance); some aliphatic amines release a large amount of heat during curing. Representative companies and models: Huntsman: Jeffamine series polyether amines (D/E series), Araldite series modified amines (e.g., LY series). Cardolite: NX (special cashew nutshell liquid modified amines, such as NX-2041), Lite series (low viscosity curing agents). Air Products: Ancamine series (modified cycloaliphatic amines/aliphatic amines, such as K54, 2014AS). Dow Chemical: Epikure series (polyamides, such as 3115, 3140; modified amines). Allnex: Additol XL series (modified amine curing agents).
Latent curing agent
Principle: At room temperature or lower temperatures, the active groups of the curing agent are “protected” (in an inert or low-activity state) through physical encapsulation, chemical masking, or microencapsulation. They are “activated” by heating, moisture, mechanical force, or specific conditions (such as ultraviolet light), releasing reactive groups (such as isocyanates or amines). This is used in applications requiring single-component systems, good storage stability, and convenient application, such as single-component baking paints, single-component adhesives, and powder coatings. Advantages: Provides a single-component system solution, simple operation, eliminating the need for weighing and mixing; good storage stability (does not cure easily at room temperature); very low VOC content (e.g., water-soluble); solves the problem of short pot life after mixing; enables low-temperature or special-condition curing. Disadvantages: Usually requires additional energy to trigger curing (e.g., heat); the deblocking temperature/conditions are relatively fixed, resulting in less flexibility; the deblocking reaction may release small molecules of the blocking agent (leading to odor or environmental pollution risks, requiring careful selection of the blocking agent); the cost is usually higher than ordinary curing agents. Representative Companies and Models: Based on isocyanate blocking technology: After deblocking, -NCO is released and reacts with -OH. Hefei Konada (This company): CR-40S (good water dispersibility, low-temperature deblocking: approximately 110-120°C, good flexibility, excellent yellowing resistance) Covestro: Bayhydur BL (hydrophilically modified blocked aliphatic polyisocyanate, good water dispersibility, requires higher temperature for deblocking) Based on amine blocking technology/DICY: Mainly used for epoxy curing. DOW: Epikure P-series (sebacic acid dihydrazide). Mitsubishi Chemical: Novacure HX series (e.g., HX-3721 urea derivatives). Others: Imidazoline compounds (epoxy curing latent catalysts), UV latent amines, etc.
CR-40S
Type: Water-based non-ionic blocked isocyanate (latent curing agent) Core Mechanism: Latent activity at room temperature, rapid release and activation of -NCO groups upon heating at 110-120°C. Key Advantages: Low-temperature activation: Compared to similar products (common unblocking temperature >130°C), low-temperature (110-120°C) unblocking is more energy-efficient and suitable for heat-sensitive substrates (such as certain plastics and fabric coatings). This is especially important for textiles and “three-proof” finishing. Water-based and environmentally friendly: Water-dilutable, VOC-free, complying with increasingly stringent environmental regulations. Tactile effect: After curing, it maintains or imparts excellent soft feel to the coating, which is crucial for textile and leather applications. Anti-discoloration performance: Excellent yellowing resistance, especially suitable for white and light-colored systems and applications requiring strict color stability. Typical Applications: Single-component thermosetting water-based coatings: Significantly improves the water resistance, chemical resistance, abrasion resistance, and adhesion of the paint film. Textile “three-proof” finishing: Helps improve the durability (wash resistance) of organofluorine/silicone finishing agents. Textile coating/printing: Enhances adhesion, wash resistance, abrasion resistance, and color stability. Single-component metal baking paint: Replaces traditional amino resins, reducing formaldehyde release and improving brittleness. Polyester/cord fabric treatment: Optimizes the adhesion between polyester and rubber. Key Parameters (Reference): Solid content approximately 40%, viscosity <100 mPa.s, NCO content after unblocking 4.5-5.0% (note the unblocking conditions and final NCO utilization rate). Storage Requirements: Must be stored sealed and protected from light at 6-28°C (cold chain recommended), shelf life 12 months.
How to choose a curing agent?
There is no “universal” curing agent; only the one best suited to the application scenario: What are the core needs? Fast curing? Long-term storage? Environmental friendliness? Excellent hardness? Or toughness? Cost? What are the process requirements? Is a two-component mixture acceptable? Are heating conditions available (what temperature can be reached)? What are the requirements for the working window (pot life)? Substrate and performance targets? Is it for treating metals? Plastics? Wood? Fabrics? Are the core performance requirements wear resistance? Chemical resistance? Weather resistance? Or a soft touch? Compliance with environmental regulations? VOC content? Toxicity? Are there any requirements regarding prohibited substances (such as formaldehyde)? Key conclusions: Performance is paramount, and two-component operation is acceptable → Choose isocyanates (polyurethane type) or amines (epoxy type).
Easy operation, long shelf life, low VOC → Latent curing agents are the preferred choice.
Water-based systems, low-temperature baking, emphasis on feel and yellowing resistance → CR-40S and similar new water-based latent curing agents demonstrate significant value.
