The development of unsaturated polyester resin products has a history of more than 70 years. In such a short period of time, unsaturated polyester resin products have developed rapidly in terms of output and technical level. Since the former unsaturated polyester resin products have developed into one of the largest varieties in the thermosetting resin industry. During the development of unsaturated polyester resins, technical information on product patents, business magazines, technical books, etc. emerges one after another. So far, there are hundreds of invention patents every year, which are related to unsaturated polyester resin. It can be seen that the production and application technology of unsaturated polyester resin has become more and more mature with the development of production, and has gradually formed its own unique and complete technical system of production and application theory. In the past development process, unsaturated polyester resins have made a special contribution to general use. In the future, it will develop to some special-purpose fields, and at the same time, the cost of general-purpose resins will be reduced. The following are some interesting and promising unsaturated polyester resin types, including: low shrinkage resin, flame retardant resin, toughening resin, low styrene volatilization resin, corrosion-resistant resin, gel coat resin, light curing resin Unsaturated polyester resins, low-cost resins with special properties, and high-performance tree fingers synthesized with new raw materials and processes.
1.Low shrinkage resin
This resin variety may just be an old topic. Unsaturated polyester resin is accompanied by a large shrinkage during curing, and the general volume shrinkage rate is 6-10%. This shrinkage can severely deform or even crack the material, not in the compression molding process (SMC, BMC). To overcome this shortcoming, thermoplastic resins are usually used as low shrinkage additives. A patent in this area was issued to DuPont in 1934, patent number U.S. 1.945,307. The patent describes the copolymerization of dibasic antelopelic acids with vinyl compounds. Clearly, at the time, this patent pioneered low shrinkage technology for polyester resins. Since then, many people have devoted themselves to the study of copolymer systems, which were then considered to be plastic alloys. In 1966 Marco’s low shrinkage resins were first used in moulding and industrial production.
The Plastics Industry Association later called this product “SMC”, which means sheet molding compound, and its low-shrinkage premix compound “BMC” means bulk molding compound. For SMC sheets, it is generally required that the resin-molded parts have good fit tolerance, flexibility and A-grade gloss, and micro-cracks on the surface should be avoided, which requires the matched resin to have a low shrinkage rate. Of course, many patents have since improved and improved this technology, and the understanding of the mechanism of low-shrinkage effect has gradually matured, and various low-shrinkage agents or low-profile additives have emerged as the times require. Commonly used low shrinkage additives are polystyrene, polymethyl methacrylate and the like.
2.Flame retardant resin
Sometimes flame retardant materials are as important as drug rescue, and flame retardant materials can avoid or reduce the occurrence of disasters. In Europe, the number of fire deaths has decreased by about 20% in the past decade due to the use of flame retardants. The safety of flame retardant materials itself is also very important. It is a slow and difficult process to standardize the type of materials used in industry. At present, the European Community has and is conducting hazard assessments on many halogen-based and halogen-phosphorus flame retardants. , many of which will be completed between 2004 and 2006. At present, our country generally uses chlorine-containing or bromine-containing diols or dibasic acid halogen substitutes as raw materials to prepare reactive flame retardant resins. Halogen flame retardants will produce a lot of smoke when burning, and are accompanied by the generation of highly irritating hydrogen halide. The dense smoke and poisonous smog produced during the combustion process causes great harm to people.
More than 80% of fire accidents are caused by this. Another disadvantage of using bromine or hydrogen-based flame retardants is that corrosive and environment-polluting gases will be produced when they are burned, which will lead to damage to electrical components. The use of inorganic flame retardants such as hydrated alumina, magnesium, canopy, molybdenum compounds and other flame retardant additives can produce low smoke and low toxicity flame retardant resins, although they have obvious smoke suppression effects. However, if the amount of inorganic flame retardant filler is too large, not only will the viscosity of the resin increase, which is not conducive to construction, but also when a large amount of additive flame retardant is added to the resin, it will affect the mechanical strength and electrical properties of the resin after curing.
At present, many foreign patents have reported the technology of using phosphorus-based flame retardants to produce low-toxicity and low-smoke flame retardant resins. Phosphorus-based flame retardants have a considerable flame retardant effect. The metaphosphoric acid generated during combustion can be polymerized into a stable polymer state, forming a protective layer, covering the surface of the combustion object, isolating oxygen, promoting the dehydration and carbonization of the resin surface, and forming a carbonized protective film. Thereby preventing combustion and at the same time phosphorus-based flame retardants can also be used in conjunction with halogen flame retardants, which has a very obvious synergistic effect. Of course, the future research direction of flame retardant resin is low smoke, low toxicity and low cost. The ideal resin is smoke-free, low-toxic, low-cost, does not affect the resin, has inherent physical properties, does not need to add additional materials, and can be directly produced in the resin production plant.
3.Toughening resin
Compared with the original unsaturated polyester resin varieties, the current resin toughness has been greatly improved. However, with the development of the downstream industry of unsaturated polyester resin, more new requirements are put forward for the performance of unsaturated resin, especially in terms of toughness. The brittleness of unsaturated resins after curing has almost become an important problem restricting the development of unsaturated resins. Whether it is a cast-molded handicraft product or a molded or wound product, the elongation at break becomes an important indicator for evaluating the quality of resin products.
At present, some foreign manufacturers use the method of adding saturated resin to improve toughness. Such as adding saturated polyester, styrene-butadiene rubber and carboxy-terminated (suo-) styrene-butadiene rubber, etc., this method belongs to the physical toughening method. It can also be used to introduce block polymers into the main chain of unsaturated polyester, such as the interpenetrating network structure formed by unsaturated polyester resin and epoxy resin and polyurethane resin, which greatly improves the tensile strength and impact strength of the resin. , this toughening method belongs to chemical toughening method. A combination of physical toughening and chemical toughening can also be used, such as mixing a more reactive unsaturated polyester with a less reactive material to achieve the desired flexibility.
At present, SMC sheets have been widely used in the automotive industry due to their light weight, high strength, corrosion resistance, and design flexibility. For important parts such as automotive panels, rear doors, and outer panels, good toughness is required, such as automotive exterior panels. The guards can bend back to a limited extent and return to their original shape after a slight impact. Increasing the toughness of the resin often loses other properties of the resin, such as hardness, flexural strength, heat resistance, and curing speed during construction. Improving the toughness of the resin without losing other inherent properties of the resin has become an important topic in the research and development of unsaturated polyester resins.
4.Low styrene volatile resin
In the process of processing unsaturated polyester resin, volatile toxic styrene will cause great harm to the health of construction workers. At the same time, styrene is emitted into the air, which will also cause serious air pollution. Therefore, many authorities limit the allowable concentration of styrene in the air of the production workshop. For example, in the United States, its permissible exposure level (permissible exposure level) is 50ppm, while in Switzerland its PEL value is 25ppm, such a low content is not easy to achieve. Relying on strong ventilation is also limited. At the same time, strong ventilation will also lead to the loss of styrene from the surface of the product and the volatilization of a large amount of styrene into the air. Therefore, to find a way to reduce the volatilization of styrene, from the root, it is still necessary to complete this work in the resin production plant. This requires the development of low styrene volatility (LSE) resins that do not pollute or less pollute the air, or unsaturated polyester resins without styrene monomers.
Reducing the content of volatile monomers has been a topic developed by the foreign unsaturated polyester resin industry in recent years. There are many methods currently used: (1) the method of adding low volatility inhibitors; (2) the formulation of unsaturated polyester resins without styrene monomers uses divinyl, vinylmethylbenzene, α-methyl Styrene to replace vinyl monomers containing styrene monomers; (3) The formulation of unsaturated polyester resins with low styrene monomers is to use the above monomers and styrene monomers together, such as using diallyl phthalate The use of high-boiling vinyl monomers such as esters and acrylic copolymers with styrene monomers: (4) Another method to reduce the volatilization of styrene is to introduce other units such as dicyclopentadiene and its derivatives into unsaturated polyesters Resin skeleton, to achieve low viscosity, and ultimately reduce the content of styrene monomer.
In seeking a way to solve the problem of styrene volatilization, it is necessary to comprehensively consider the applicability of the resin to the existing molding methods such as surface spraying, lamination process, SMC molding process, the cost of raw materials for industrial production, and the compatibility with the resin system. , Resin reactivity, viscosity, mechanical properties of resin after molding, etc. In my country, there is no clear legislation on restricting the volatilization of styrene. However, with the improvement of people’s living standards and the improvement of people’s awareness of their own health and environmental protection, it is only a matter of time before relevant legislation is required for an unsaturated consumer country like us.
5.Corrosion-resistant resin
One of the larger uses of unsaturated polyester resins is their corrosion resistance to chemicals such as organic solvents, acids, bases, and salts. According to the introduction of unsaturated resin network experts, the current corrosion-resistant resins are divided into the following categories: (1) o-benzene type; (2) iso-benzene type; (3) p-benzene type; (4) bisphenol A type; (5) Vinyl ester type; and others such as xylene type, halogen-containing compound type, etc. After decades of continuous exploration by several generations of scientists, the corrosion of resin and the mechanism of corrosion resistance have been thoroughly studied. The resin is modified by various methods, such as introducing a molecular skeleton that is difficult to resist corrosion into unsaturated polyester resin, or using unsaturated polyester, vinyl ester and isocyanate to form an interpenetrating network structure, which is very important for improving the corrosion resistance of the resin. The corrosion resistance is very effective, and the resin produced by the method of mixing acid resin can also achieve better corrosion resistance.
Compared with epoxy resins, the low cost and easy processing of unsaturated polyester resins have become great advantages. According to unsaturated resin net experts, the corrosion resistance of unsaturated polyester resin, especially the alkali resistance, is far inferior to that of epoxy resin. Can not replace epoxy resin. At present, the rise of anti-corrosion floors has created opportunities and challenges for unsaturated polyester resins. Therefore, the development of special anti-corrosion resins has broad prospects.
Gel coat plays an important role in composite materials. It not only plays a decorative role on the surface of FRP products, but also plays a role in wear resistance, aging resistance and chemical corrosion resistance. According to experts from unsaturated resin network, the development direction of gel coat resin is to develop gel coat resin with low styrene volatilization, good air drying and strong corrosion resistance. There is a large market for heat-resistant gel coats in gel coat resins. If the FRP material is immersed in hot water for a long time, blisters will appear on the surface. At the same time, due to the gradual penetration of water into the composite material, the surface blisters will gradually expand. The blisters will not only affect The appearance of the gel coat will gradually reduce the strength properties of the product.
Cook Composites and Polymers Co. of Kansas, USA, uses epoxy and glycidyl ether-terminated methods to manufacture a gel coat resin with low viscosity and excellent water and solvent resistance. In addition, the company also uses polyether polyol-modified and epoxy-terminated resin A (flexible resin) and dicyclopentadiene (DCPD)-modified resin B (rigid resin) compound, both of which have After compounding, the resin with water resistance can not only have good water resistance, but also have good toughness and strength. Solvents or other low-molecular substances penetrate into the FRP material system through the gel coat layer, becoming a water-resistant resin with excellent comprehensive properties.
7.Light curing unsaturated polyester resin
The light curing characteristics of unsaturated polyester resin are long pot life and fast curing speed. Unsaturated polyester resins can meet the requirements for limiting the volatilization of styrene by light curing. Due to the advancement of photosensitizers and lighting devices, the foundation for the development of photocurable resins has been laid. Various UV-curable unsaturated polyester resins have been successfully developed and put into production in large quantities. The material properties, process performance and surface wear resistance are improved, and the production efficiency is also improved by using this process.
8.Low-cost resin with special properties
Such resins include foamed resins and aqueous resins. Currently, the scarcity of wood energy has an upward trend in the range. There is also a shortage of skilled operators working in the wood processing industry, and these workers are increasingly being paid. Such conditions create conditions for engineering plastics to enter the wood market. Unsaturated foamed resins and water-containing resins will be developed as artificial woods in the furniture industry due to their low cost and high strength properties. The application will be slow at the beginning, and then with the continuous improvement of processing technology, this application will be developed rapidly.
Unsaturated polyester resins can be foamed to make foamed resins that can be used as wall panels, pre-formed bathroom dividers, and more. The toughness and strength of the foamed plastic with unsaturated polyester resin as the matrix are better than that of foamed PS; it is easier to process than foamed PVC; the cost is lower than that of foamed polyurethane plastic, and the addition of flame retardants can also make it flame retardant and anti-aging. Although the application technology of resin has been fully developed, the application of foamed unsaturated polyester resin in furniture has not been paid much attention. After investigation, some resin manufacturers have great interest in developing this new type of material. Some major issues (skinning, honeycomb structure, gel-foaming time relationship, exothermic curve control have not been fully resolved before commercial production. Until an answer is obtained, this resin can only be applied due to its low cost In the furniture industry. Once these problems are solved, this resin will be widely used in areas such as foam flame retardant materials rather than just using its economy.
Water-containing unsaturated polyester resins can be divided into two types: water-soluble type and emulsion type. As early as the 1960s abroad, there have been patents and literature reports in this area. Water-containing resin is to add water as a filler of unsaturated polyester resin to the resin before resin gel, and the water content can be as high as 50%. Such resin is called WEP resin. The resin has the characteristics of low cost, light weight after curing, good flame retardancy and low shrinkage. The development and research of water-containing resin in my country began in the 1980s, and it has been a long period of time. In terms of application, it has been used as an anchoring agent. Aqueous unsaturated polyester resin is a new breed of UPR. The technology in the laboratory is becoming more and more mature, but there is less research on the application. The problems that need to be further solved are the stability of the emulsion, some problems in the curing and molding process, and the problem of customer approval. Generally, a 10,000-ton unsaturated polyester resin can produce about 600 tons of wastewater every year. If the shrinkage generated in the production process of unsaturated polyester resin is used to produce water-containing resin, it will reduce the cost of resin and solve the problem of production environmental protection.
We deal in the following resin products: unsaturated polyester resin; vinyl resin; gel coat resin; epoxy resin.
We also produce fiberglass direct roving, fiberglass mats, fiberglass mesh, and fiberglass woven roving.
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Post time: Jun-08-2022
