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Abstract: Due to a temporary surplus in epoxy resin production, a sharp drop in prices, and a structural shortage along with steep price declines in commonly used fatty amine curing agents, the material selection used in the epoxy flooring industry has been forced to undergo adjustments. Firstly, the cost-performance advantages of conventional varieties such as phenolic amine T-31, polyamides, and modified fatty amines have basically disappeared. II. The variety structure of floor coatings is evolving toward higher performance characteristics, with curing agents that offer outstanding advantages being given priority. III. Environmental protection, safety, and emission reduction are driving the epoxy flooring industry to abandon solvent-based processes as well as materials with high viscosity and low density. These three factors have driven the development of curing agents for epoxy floors toward the use of modified aromatic amine primers, along with modified polyether amine intermediates and topcoats. It is estimated that in 2009, modified aromatic amines and modified polyether amines will account for over 70% of mid-coats and over 80% of top coats, respectively. At the same time, the modification technologies for aromatic amines and polyether amines will be key to research and development across the industry. Keywords: Plummeting resins, soaring fatty amines, restructuring of curing agents, aromatic amines, polyether amines taking the lead. China is not yet a powerhouse in epoxy resin production, but it is definitely a major producer. Although the product quality is still second-rate on a global scale, its annual production capacity of 800,000 tons definitely ranks among the highest in the world. Moreover, it is entirely possible that around 2010, production capacity will exceed the threshold of one million tons per year, enabling the country to rank first in the world. But as a curing agent that must be used in conjunction with epoxy resins, it is a country that is absolutely weak and small in terms of quality, variety, and production capacity. A facility with an annual production capacity of 800,000 tons of epoxy resin still lacks the equipment needed to produce the key raw materials used in the manufacture of epoxy resin curing agents, namely fatty amines, epoxy amines, and polyether amines. This means that we have no say in terms of the sourcing and pricing of these raw materials for curing agents. To date, the application and formulation of epoxy resin curing agents in the Chinese market are still largely determined and adjusted by the supply and prices available in the international market. This situation may continue for quite some time yet. This year, due to certain special circumstances in the international market, aliphatic amines – which are used as raw materials for more than two-thirds of the curing agents produced domestically – have become unavailable, leading to abnormal situations such as prices soaring threefold. Not only are polyamides, phenolic amines, and Mannich-modified amines produced using imported amines far more cost-effective, but this also has led to fundamental changes in the structure of high-end epoxy resin curing agents produced in China. Given that people are now aware of this structural deficiency in aliphatic amines, it is expected that this situation will not change completely for another one or two years. Therefore, the traditional structure of the epoxy resin curing agents used in China must undergo fundamental adjustments, and a phase of comprehensive modification has already begun. The product structure of curing agents for epoxy flooring in China is currently being adjusted due to the following three factors: First, due to a shortage of aliphatic amines in the market, the traditionally used phenolic amine T-31 has maintained a price of over 25,000 yuan per ton for a long time; polyamide (H-200) also has a price of over 25,000 yuan per ton, yet its quality cannot be guaranteed. As for imported versions of these products, their price is approaching 40,000 yuan per ton. As for pure aromatic amine curing agents modified with diphenylmethane based on triamine or tetraamine groups, high-quality ones also cost 17,000 yuan per ton. With a resin ratio of 100:60–80, these varieties outperform T-31 and polyamides in terms of temperature resistance, water resistance, and corrosion resistance. Moreover, the cost per ton of the cured product is 2,000 yuan/ton lower than that of T-31, and more than 2,640 yuan/ton lower than that of domestic polyamides. Therefore, for some time to come, regardless of the fluctuations in the market price of epoxy resins, aromatic amines will continue to dominate the market in terms of cost-effectiveness for epoxy primers. Traditional amine curing agents for epoxy topcoats mainly include IPDA, polyether amines, modified aliphatic amines, and polyamides. Due to changes in the structure of amine resources in the market, modified fatty amines and polyamides have completely lost their cost-effectiveness advantage, while IPDA is generally used only in small amounts as an additive due to its price. Only the amount of modified polyetheramine has been increasing steadily. As a top-coating curing agent, polyether amine boasts excellent properties such as a light color, good surface gloss, wear and slip resistance (with appropriate elasticity), and high tensile break strength. It also features adjustable curing speed, low viscosity, and good leveling properties. However, when materials such as the commonly used variety D-230 are used alone, both their hardness and adhesion require appropriate adjustment. As the application technology of polyether amine curing agents matures, polyether amine varieties with excellent properties and good cost-performance, such as 511 and 104, can be promoted rapidly. It is expected that in the next one to two years, from a cost-performance perspective, modified polyether amines will undoubtedly dominate the market for epoxy topcoat curing agents. II. Changes in the types and structures of floor surfaces have led to corresponding adjustments in the varieties of curing agents. Epoxy flooring has a development history of nearly 15 years in China. It has evolved from being solvent-free, of high quality, expensive, and offering high added value when first introduced, to solvent-based products with lower prices, lower added value, and uneven quality in the intermediate stage, and now it has progressed again to solvent-free products that are of high quality, possess multiple features, and are practically solvent-free. It has gone through a gradual process of increased awareness – from a situation where neither the owners nor the builders knew each other, to superficial acquaintance, and then to an emphasis on internal quality. Today, in China’s epoxy flooring industry, both owners and builders are becoming more experienced. Owners prioritize products with excellent quality and performance, while also seeking reasonable prices. In particular, there is a strong demand for properties such as wear resistance, durability, compressive strength, corrosion resistance, and temperature tolerance. For example, with the restructuring of China’s food industry, flooring used in this sector needs to meet international standards: it must be resistant to mold, oil, dust, and slippage, and it cannot contain chemical disinfectants. As a result, it is necessary to clean and disinfect such flooring using high-temperature steam on a daily basis. Such flooring is required to withstand temperatures of 120 degrees Celsius, long periods of steam treatment, and to not release any toxic or harmful solvents; it also needs to be pressure-resistant and wear-resistant. Ordinary self-leveling epoxy floors cannot withstand it, let alone solvent-based epoxy floors. The use of epoxy sand-cement flooring can fully meet various performance requirements, and the key is that this process allows for a silica sand content of up to 92%. The interfacial area between inorganic and organic materials is very low, which effectively reduces the changes in thermal deformation stress caused by temperature differences. Moreover, the properties of the special epoxy bonding materials can be adjusted according to the owner’s requirements. The selection of the curing agent plays a very critical role in this. As environmental requirements such as environmental protection, corrosion prevention, and building preservation become increasingly stringent, its application scope is expanding. Epoxy flooring is being used increasingly in various applications, including indoors, as flooring in facilities requiring high corrosion resistance, in mechanical operation workshops and aircraft hangars where oil resistance and slip prevention are important. It is also used outdoors on bridges, high-speed roads with waterproof and anti-slip properties, and in tunnels. The basic requirements for such flooring include being solvent-free, having high tensile strength at break, high compressive strength, water resistance, corrosion resistance, temperature resistance, flexibility, high adhesion, and a low interfacial tension along with a high content of fillers. Generally, modified fatty amines and polyamides fail to meet these requirements ； Aromatic amines and polyether amines have strong properties, but their drawbacks are also evident. If combined using the cold assembly method, it is difficult to achieve the desired results. The most effective method currently in use is the grafting and composite addition process, which combines the advantages of both approaches and can basically meet the performance requirements of modern epoxy flooring. It can possess both crack-resistant tensile fracture strength and compressive strength, along with appropriate elasticity. It is also resistant to friction and to the scouring effects of steam at high temperatures, and it does not become brittle at temperatures below minus 20 degrees Celsius. Resistant to acids and alkalis. But at the same time, we must fully recognize that the technical complexity of such curing agent composite processes is relatively high, and the varieties of floor surfaces as well as their design techniques are also becoming increasingly advanced. The emergence of sandblasted floors, sand-pressed floors, and floors made with thick layers of polymer mortar has also promoted the modification of high-quality epoxy curing agents such as polyether amines, leading to faster development and advancement in related application technologies. Starting in the second half of this year, the market price of epoxy resins plummeted. Yet imported amine curing agents have seen a sharp drop despite the contrary market trends. It is expected that in the first half of 2009, epoxy resin prices will remain low, but this low level will not persist for too long. Fat amines used as curing agents will also remain at high levels, and this situation will continue for an extended period. Due to their widespread use in composite materials such as wind turbine blades, polyether amines will face supply constraints; however, compared to other imported amine products, their supply and prices remain relatively stable. Therefore, from the perspective of the flooring market, regardless of the ‘tsunami’ or ‘earthquake’ that struck the epoxy resin market in 2009, modified aromatic amines and polyether amines remain the dominant choices for curing agents in Chinese epoxy flooring. However, the requirements for greater specificity regarding varieties and performance will continue to rise, as will the demands for composite modification techniques for curing agents. III. Promote environmental protection and energy conservation by enforcing mandatory adjustments to the materials and structures used in epoxy flooring. China’s annual production capacity for epoxy resin is 800,000 tons; with an average consumption of 30 kg of xylene per ton, the total annual emissions of benzene gas amount to 2,400 tons. China produces approximately 100 million square meters of epoxy flooring per year, of which 90% uses solvent-based primers; the average amount of benzene solution emitted per square meter is about 0.187 kg, resulting in an annual total emission of 16,830 tons. The amount of epoxy used was only 43,200 tons, accounting for 5.4% of the production capacity. The emissions, however, are 7.02 times those generated by the total production capacity of epoxies. Such astonishing figures mean that even if environmental authorities do not conduct any inspections, every professional in the flooring industry will feel guilty. Moreover, it is impossible for these authorities to ignore this situation forever. The widespread use of solvent-based epoxy floors began in the late 1990s, when the market price of epoxy floors dropped significantly, affecting China’s epoxy flooring industry. The entry barriers for businesses are extremely low, and there are many construction teams that operate without any licenses or permits; as a result, their operational and management costs are virtually zero. As a result, it has led to vicious competition in the flooring industry, where only price is considered and quality is ignored. Some irresponsible construction teams, driven solely by a pursuit of profit, are responsible for the fact that over 90% of flooring surfaces in China use solvent-based materials and techniques. In fact, when China introduced epoxy flooring systems in the early 1990s, solvent-free epoxy flooring was already widely used worldwide. And based on the current market prices of flooring materials, solvent-based flooring does not offer any significant cost advantage over solvent-free versions; the cost reduction per square meter is only about 0.5 yuan. Meanwhile, the hazards associated with safety, environmental protection, hygiene, and flooring quality resulting from the use of solvent-based flooring are enormous and alarming. By emitting 16,830 tons of toxic and harmful gases, 45 million yuan in costs can be saved, at the expense of the internal quality of 90 million square meters of flooring. It is a high price paid for meager benefits and moral conscience, along with a huge loss of social responsibility. No one is able to maintain balance of mind and forgive. The unrestrained emission of harmful gases from adhesive coatings during actual application and in their long-term use has drawn attention from countries around the world. Whether developed or developing, countries have already implemented or are preparing to introduce corresponding regulatory measures. This practice of emitting toxic and harmful gases at no cost should be abolished as soon as possible. In the production of epoxy flooring, the use of solvent-free coatings is feasible without any technical issues. When epoxy flooring coatings were introduced to China 15 years ago, they were already solvent-free; it was later two factors that led to a large-scale shift in China’s epoxy flooring industry toward solvent-based coatings. Firstly, low costs, cheap labor, and a zero-emission environment create conditions for fierce price competition in the market. Some owners who have no understanding of the significant quality differences between solvent-based coatings and solvent-free floor coatings force legitimate companies to compete on price, focusing only on the slight difference between these two types of products, which results in legitimate businesses being unable to compete with unlicensed and unqualified operators. High-quality solvent-free epoxy flooring cannot compete with low-quality, low-cost solvent-based flooring. It also forced some legitimate companies that originally had a focus on quality and environmental protection to comply as well. Secondly, epoxy resins have remained at high prices, and the technology for developing curing agents is underdeveloped. In domestic floor coating systems, high-viscosity polyamide-based curing agents with high mixing ratios have been used for a long time; it is difficult to apply such curing agents without solvent release. For another type of curing agent with a high amine value and a low mixing ratio, such as phenol-aldehyde amine (T-31), the mixing ratio must be strictly controlled. Moreover, inadequate control of the phenol content in the products manufactured by these companies results in uneven curing rates. Therefore, an appropriate amount of solvent needs to be added to improve its fluidity and dispersibility, thereby accelerating the mixing process and speeding up curing. Today, in China, the pace of development in curing agent technology is accelerating. The widespread use of modified aromatic amine primers as curing agents, which feature low viscosity, low volatility, and virtually no emission of harmful or toxic gases, not only enables solvent-free application but also results in curing products with relatively low costs. Of course, this is assuming that manufacturers do not deliberately add toxic substances such as aniline to these curing agents in order to gain unfair profits. The technical and economic aspects of midsole coating make full solvent-free production highly feasible. As safety and environmental regulations become increasingly stringent, solvent-based epoxy flooring that releases toxic substances will eventually be completely banned. As the prices of some amine-based curing agent raw materials exported from China to the international market continue to rise sharply against market trends, it has become increasingly urgent to reduce costs through product structure adjustments. In 2009, modified aromatic amines accounted for the vast majority of the intermediate coatings used in conventional epoxy flooring, while modified curing agents based on polyether amines were to make up over 80% of the top-coating curing agents. The return to normal levels for epoxy resin prices will bring great opportunities to epoxy flooring, especially solvent-free epoxy flooring that is environmentally friendly, safe, and hygienic. It also creates favorable conditions for competition between epoxy flooring and acrylic and polyurethane flooring. To meet the market’s demands for epoxy flooring that combines low cost, solvent-free properties, high temperature resistance, corrosion resistance, oil resistance, freeze resistance, water resistance, high adhesion, and excellent coverage, epoxy primers will increasingly rely on modified curing agents with high density, low viscosity, strong penetration, and moderate stress in the cured film, among which modified aromatic amines are the preferred choice. As for topcoats, curing agents with high density, moderate stress, good transparency and weather resistance, as well as high tensile strength, are required to ensure water resistance, corrosion resistance, temperature resistance, and compressive strength. In line with the development trend of the advanced epoxy flooring industry, pure resin topcoat processes with different properties will be widely used in the future, and the curing agents used will primarily be modified polyether amines. It is expected that in 2009, modified polyether amines will gradually become the dominant curing agents used in epoxy topcoats. In the intermediate bonding layers employed in sandblasting, shot blasting, and polymer mortars, modified polyether amines and aromatic amines will either be used together or separately, but polyether amines will still hold a decisive advantage. It is also undeniable that aromatic amines account for over 70% of the curing agents in primers. Author’s profile: With over 40 years of experience in the research and development of epoxy resins, including raw materials such as ECH and bisphenol A, as well as special epoxy resins and epoxy diluents, he has particular expertise in the development and application of epoxy curing agents. On multiple occasions, I was responsible for the technical work related to the initial introduction of domestic self-leveling floor materials, spray-painted colored sand, sand-pressed materials, and polymer mortar floor materials. Author: Hang Longcheng — 13538683267