Background Currently, almost all commercialized epoxy resins are petroleum-based, and bisphenol A epoxy resin (DGEBA) accounts for about 90% of production. Bisphenol A is one of the most widely used industrial compounds in the world. However, in recent years, with the deepening of people's understanding of the biological toxicity of bisphenol A, many countries have banned the use of bisphenol A in plastic packaging and containers for food. In addition, DGEBA is easy to burn and cannot extinguish automatically after leaving the fire, which also limits its application scope. Therefore, the use of bio-based raw materials to prepare epoxy resin has gradually become a research hotspot in recent years.   Application Bio-based epoxy resin has wide application prospects in the fields of automobiles, transportation, culture and sports, woodware, home furnishing, and construction. In particular, the demand for electronic appliances and coatings industries is growing. Composite materials and adhesives are increasingly used in various fields. As well as the advancement of the global green and sustainable development strategy, bio-based epoxy resin will usher in excellent development opportunities and market space.   Challange In recent years, researchers have designed and synthesized a variety of bio-based compounds with heterocyclic, aliphatic and aromatic rings to replace petroleum-based bisphenol A for the preparation of epoxy resins. However, the thermal stability and mechanical properties of current bio-based epoxy resins are still difficult to match those of bisphenol A-type epoxy resins. Therefore, it is still a big challenge to design and synthesize bio-based monomers that can meet the high performance and functional requirements of bio-based epoxy resins.It is also an important step to broaden the application scope of bio-based polymer materials and enhance their competitive advantages over petroleum-based polymer materials. At present, bio-based epoxy resins mainly include high-temperature resistant bio-based epoxy resins, intrinsic flame-retardant bio-based epoxy resins, toughening of bio-based epoxy resins, degradable and recycled bio-based epoxy resins, etc.   Development trend With the diversification of molecular structure designs of bio-based compounds, the high-performance and functional advantages of bio-based epoxy resins have gradually become more prominent, and the composite materials constructed from them have shown excellent comprehensive properties. After analysis and data review, the future development trends of bio-based epoxy resins mainly include the following directions: Build a stable bio-based raw material supply system. Synthesize new bio-based epoxy resins from non-food sources. Construct a structure-function integrated bio-based epoxy resin polymer material system. Design degradable, self-healing and recyclable bio-based thermoset polymer materials. Nanjing Yolatech provides all kinds of high purity and low chlorine epoxy resins and specialty epoxy resin, including Bisphenol A epoxy resin, Bisphenol F epoxy resin, Phenolic epoxy resin, Brominated epoxy resin, DOPO modified phenolic epoxy resin, MDI modified epoxy resin, DCPD epoxy resin, Multifunctional epoxy resin, Crystalline epoxy resin, HBPA epoxy resin and so on. And we also could provide all kinds of curing agents or hardeners and diluents for epoxy resin application.  

1. Indicators of epoxy groups This is the most important characteristic index of epoxy resin, which is used to indicate the content of epoxy group in the resin molecule, and there are three main ways of expression, including  epoxy value, epoxy index and epoxy equivalent. Epoxy value is defined as the amount of epoxy groups(mol) per 100g of epoxy resin，unit is mol/100g. The definition of the epoxy value is mainly for the purpose of calculating the amount of curing agent to be added to the epoxy resin for curing. The amount of curing agent is the mass of curing agent to be added per 100g of epoxy resin cured. Epoxy index is the amount of epoxy groups(mol) per 1kg of epoxy resin, the unit is mol/kg. In terms of the International System of Measurement (SI units), the epoxy index is more appropriate than the epoxy value, which is 10 times larger than the epoxy value. Epoxy equivalent is the mass (g) of an epoxy resin containing 1 mol of epoxy groups ,the unit is g/mol. The chain segments between the epoxy groups become longer and longer as the molecular weight of the epoxy resin increases, so the epoxy equivalent of epoxy resins with a high relative molecular mass is also elevated. The physical quantity of epoxy equivalent is usually used to describe the epoxy group of epoxy resin in the United States, Japan and Europe.   2. Hydroxyl content Bisphenol A-type epoxy resin molecular chain contains a large number of secondary hydroxyl structure, the larger the polymerization degree n value, its molecular weight is also larger, the higher the hydroxyl content. It can cross-link with phenolic resins, amino resins or Poly isocyanates, and it can promote the curing reaction. Therefore, when controlling the curing process of epoxy resin paint, the hydroxyl content of epoxy resin must be determined. There are two most used methods to express the hydroxyl content. The hydroxyl value F is the amount of hydroxyl contained in 100g of epoxy resin, the unit is mol/100g. And the hydroxyl equivalent H is the mass(g)of epoxy resin containing 1mol of hydroxyl, the unit is g/mol.   3. Softening point Epoxy resin is a mixture of homologous prepolymers with different degrees of polymerization and has no fixed melting point or melting process. The softening point generally refers to the temperature at which the epoxy resin turns from hard to soft and shows a certain fluidity in the process of heating. The softening point of epoxy resin can characterize the average molecular weight size and distribution of the resin, the molecular weight of the high softening point is large, and the molecular weight of the low softening point is small. Epoxy resins can be broadly classified according to the softening point into three types. Type Softening point Degree of polymerisation Low molecular weight epoxy resin <50°C <2 Medium molecular weight epoxy resin 50~95°C 2~5 High molecular weight epoxy resin >100°C >5     4. Viscosity The viscosity of epoxy resins affects the fluidity and workability of resins and coatings. Viscosity increases as the average molecular weight of the epoxy resin increases and decreases as the molecular weight distribution decreases. The viscosity of epoxy resins is extremely sensitive to temperature and decreases rapidly with increasing temperature, so it is generally expressed as the viscosity at a specific temperature.   5. Chlorine value The amount of chlorine contained in an epoxy resin (including organic chlorine and inorganic chlorine) is called the chlorine value. The chlorine in the epoxy resin is divided into organic chlorine and inorganic chlorine by the form of its existence. Organic chlorine comes from the residue of insufficient ring closure in the manufacture of the epoxy resin, which is called easily hydrolysable chlorine. Inorganic chlorine comes from the residual sodium chloride that is not washed sufficiently when manufacturing epoxy resins. Organic chlorine measures the resin reaction, and inorganic chlorine measures the level of post-production treatment processes for epoxy resins. Both are detrimental to the electrical properties of the cured substance and to corrosion resistance.