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Development Trends Of New Unsaturated Polyester Resins

Jun 17, 2020

Resin is the base material of glass fiber reinforced plastics. If glass fiber is regarded as the "muscle" of glass steel, then resin can be visually regarded as the "muscle" of glass fiber reinforced plastics. It can be seen that resin plays an indispensable role in the production process of glass steel Unsaturated polyester resin is an important member of the resin family. In recent years, unsaturated polyester resin has made rapid progress in foreign research, and new products have emerged in an endless stream, such as: low shrinkage resin, corrosion-resistant resin, strong toughness resin, low Water-absorbing unsaturated polyester resin, transparent unsaturated polyester resin, unsaturated polyester resin with low residual free styrene, PET unsaturated polyester resin, low volatility resin, gel coat resin, foamed unsaturated Polyester resin, special resin for FRP boats, heat-resistant UPR resin and photo-curable UPR resin.

The performance and application of some new unsaturated polyester resins are analyzed below. These include low shrinkage resins, corrosion-resistant resins, low water absorption unsaturated polyester resins, low volatility resins, and water-containing unsaturated polyester resins WCUP.

1. Low shrinkage resin

The so-called low-shrinkage resin, which uses thermoplastic resin to reduce and ease the curing shrinkage of UPR, has been widely used in SMC manufacturing. Commonly used low shrinkage agents are polystyrene, polymethyl methacrylate and diallyl phthalate polymers. At present, in addition to the use of polystyrene and its copolymers abroad, polycaprolactone (LPS-60), modified polyurethane and butyl cellulose acetate have also been developed. The Research Institute of Chemical Products of Japan Oil & Fats Co., Ltd. has studied the new low-shrinkage additive (LPAS) of UP resin. This new type contains elastic segments and segments compatible with UP resin. It is used in the molding process of UP resin SMC/BMC Medium makes the surface gloss and shrinkage of the product low, and the coloring performance is good. The Ohio State University studied the UP/ST/LPAS system that can be cured at low temperature with a modified thermoplastic LPAS additive, and introduced the Co-accelerator DVB into the low temperature curing system, and the second The body trimethylolpropane trimethacrylate (TMPT-MA) makes the shrinkage of the resin in the curing process better controlled. Canada added thermoplastic PVAC as a low shrinkage agent LPAS to UP resin, which also solved the shrinkage problem well. Japan Showa Polymer Co., Ltd. can increase the bonding strength of unsaturated polyester composition to 2.45MPa and linear shrinkage coefficient to 0.32% by adding low shrinkage agent solids. Japan's Monsanto Industrial Chemical Company used polyvinyl acetate (DenkaASRM4) as a low-shrinkage additive to develop a molding compound with a shrinkage of only 0.096%.

2. Corrosion Resistant Resin

Corrosion-resistant resins include bisphenol A unsaturated polyester, terephthalic acid resin and rosin modified unsaturated polyester. It is reported that the 8250 vinyl ester resin developed by Ube Corporation of Japan not only has good corrosion resistance, but also has a storage period of up to 14 months. Japan uses isophthalic type, bisphenol A type or vinyl ester type unsaturated polyester resin to make glass fiber composite materials that are resistant to 25% NaCl aqueous solution. Strong and tough resins are getting more and more attention. At present, foreign countries mainly adopt the method of adding saturated resin to improve the toughness. Such as the addition of saturated polyester, styrene-butadiene rubber and carboxyl-terminated nitrile rubber. American Amoco Chemical Co., Ltd. adopts a resin made by the reaction of unsaturated polyester containing hydroxyl group at the end and diisocyanate, its toughness can be increased by 2 to 3 times, and the trade name is Xycon. The SD resin developed by Japan Showa Polymer Company has good toughness and can be widely used to manufacture artificial marble. In Brazil, the flexible polysiloxane segment (APTS) is graft copolymerized to modify the unsaturated polyester resin containing glycidyl methacrylate (GMA) to obtain resins with high impact strength and glass fiber reinforced resins. The University of Poland found that with the increase of TDI content, the viscosity of TDI modified unsaturated polyester resin increased. When the TDI mass fraction reached 3%, the resin had good thixotropy. When 4,4-dimaleimidodiphenylmethane (BM) is added to the resin for modification, the compressive strength of the modified resin is increased to 159MPa, the glass transition temperature is 184°C, and the decomposition temperature is increased to 280°C At the same time, the curing speed is accelerated accordingly.

3. Unsaturated polyester resin with low water absorption

Regarding the low water absorption type unsaturated polyester resin, Germany made IR radiation-cured unsaturated polyester resin, which has a short curing residence time of the composite material during IR radiation curing, and the water absorption rate of the product is reduced.

The transparent unsaturated polyester resin is a bisphenol A type transparent unsaturated polyester resin artificial marble developed by Kao Corporation of Japan with a tensile strength of 44.1 MPa, a transmittance of 48%, and good heat resistance. The unsaturated polyester resin with low free styrene residue has been developed by Japan NOF United Company with a good anti-yellowing unsaturated polyester resin, which can be used as FRP, SMC, BMC resin, benzene residue after curing at 130 ℃ The ethylene mass fraction is only 0.03%. PET-type unsaturated polyester resin has more achievements. The United States and Egypt used PET (polyethylene terephthalate) waste alcoholysis to synthesize unsaturated polyester resin. By adjusting the reaction, the curing temperature can be 74~ At 90℃, the curing time is only a few minutes to more than 20 minutes of unsaturated polyester resin. South Korea synthesized a series of unsaturated polyester resins obtained from various alcoholysis products, and controlled the alcoholysis degree of PET through various alcohol compositions, and controlled the gel time and brittleness of PET unsaturated polyester resins. Used in SMC and BMC. Foamed unsaturated polyester resin also leaps into the eye. Unsaturated polyester resin as a matrix of foam plastic has better toughness and strength than foamed PS, and is easier to process than foamed PVC. Adding flame retardants can also make it flame retardant and It is resistant to aging and its cost is lower than that of foamed polyurethane plastic. Foaming unsaturated polyester resin foam mainly uses chemical foaming agent. There is not much literature on the use of physical blowing agents. The physical blowing agent is mainly freon but pollutes the environment. Chemical blowing agents mainly include: isocyanates, azos, sulfonyl hydrazides, carbonate anhydrides.

4. Low volatility resin

There are many varieties of low volatility resin and gel coat resin. Low volatility resin is currently being developed abroad, the general requirement is that the styrene content in the air around the workshop must be less than 50ug/g. The method is: adding surface film forming agent to reduce styrene volatilization; using high boiling point cross-linking agent to replace styrene; using cyclopentadiene and its derivatives combined with uPR to make the low molecular mass, so as to achieve Reduce the purpose of using styrene. Foreign BYK Chemie Company has developed a new type of auxiliary agent LPX-5500, which can reduce the styrene volatilization by 70-90%. Gel coat resin is a special resin for making gel coat layer of FRP products. Styrene is still the most suitable monomer currently used for UP resins. However, styrene has a high vapor pressure at room temperature and is easy to volatilize, especially in the process of making the gel coat layer of glass fiber reinforced plastic products by hand lay-up or injection molding process, and the backing reinforcement layer. When the vapor concentration exceeds a certain amount (>50ug/g), it will irritate people's eyes, nose and mucous membranes, causing dizziness and nausea. Therefore, the development of low-styrene dispersible gel coat resin is very necessary and of great practical significance. American Sartomer Technology Company developed a low VOC UPR composition containing maleic anhydride monomers, and used in gel coatings, adhesives, laminating resins or molding resins. The United States and Germany have developed (styrene) monomer-free unsaturated polyester resins and their compositions, which can be used in opening casting, gel coating, and electronics industries, respectively.

V. Water-containing unsaturated polyester resin WCUP

Water-containing unsaturated polyester resin WCUP is emerging. Water-containing unsaturated polyester resin WCUP is a new type of resin with water as filler that came out in the 1950s. In addition to its remarkable low-cost characteristics, this resin also has many excellent properties, such as small heat release during curing, small volume shrinkage, flame retardant and easy processing and molding. It can be used in artificial wood, decorative materials, foam products, porous materials, building materials, polyester concrete, infiltrating agents and coatings. In 1967, Horie et al. reported for the first time the preparation of stable aqueous unsaturated polyester resin emulsions with alkaline materials such as sodium hydroxide. This method is called the polyester salt formation method. In recent years, the use of dynamic methods to study multiphase/multicomponent polymer systems has attracted great international attention. Nguven-Thue et al. have studied the relationship between dynamic rheological behavior and morphological structure. Since then, such studies have become more and more A hotspot of research on polymer systems rheology. Kicko-walczak, Ewa reviewed the latest developments in unsaturated polyester resins that meet EU requirements.

Compared with the international industry, although China's unsaturated polyester resin industry has developed rapidly in the past 10 years, it still has a large gap compared with foreign countries. It has a small production scale and low product quality. There are only about 500 varieties and models, and there is a shortage of raw materials. The quality of some new raw materials does not meet the requirements, the investment in the development of new varieties and technologies is not enough, and the collaboration between scientific research institutes and production and application units needs to be further strengthened.

In particular, many small factories and poor detection methods make it difficult to guarantee product quality. At present, this low-grade competition has brought many hidden dangers to my country's FRP product market.