In recent years, the research progress of unsaturated polyester resin abroad is rapid, and new products emerge in endlessly, such as: low shrinkage resin, corrosion-resistant resin, strong toughness resin, low water absorption unsaturated polyester resin, transparent unsaturated polyester resin, low free styrene residual unsaturated polyester resin, pet unsaturated polyester resin, low volatile resin, gel coat resin, foaming unsaturated polyester resin Resin, special resin for fiberglass boat, heat resistant UPR resin and light cured UPR resin.
The following five kinds of unsaturated polyester resin performance and application analysis. It includes low shrinkage resin, corrosion-resistant resin, low water absorption type unsaturated polyester resin, low volatility resin and water content unsaturated polyester resin WCup.
（1） Low shrinkage resin
The so-called low shrinkage resin, which uses thermoplastic resin to reduce and mitigate the curing shrinkage of UPR, has been widely used in SMC manufacturing. The commonly used low shrinkage agents are polystyrene, polymethyl methacrylate and diallyl phthalate polymer. At present, in addition to polystyrene and its copolymers, polycaprolactone (lps-60), modified polyurethane and butyl acetate are also developed abroad.
A new type of low shrinkage additive (LPAS) for up resin, which contains elastic segments and segments compatible with up resin, has been studied by Japan Institute of oil and fat products. It is used in the molding process of up resin SMC / BMC, making the surface luster, shrinkage rate of products low and color performance good.
The up / St / LPAS system with modified thermoplastic LPAS additive can be cured at low temperature was studied in terms of swelling, morphology and structure at Ohio State University. The co promoter DVB and the second monomer trimethylolpropane trimethylacrylate (tmpt-ma) were introduced into the low temperature curing system to better control the shrinkage of the resin during the curing process.
Canada uses thermoplastic PVAc as low shrinkage agent LPAS to add to up resin, which also solves the shrinkage problem well. By adding low shrinkage agent solid, the bonding strength of unsaturated polyester can reach 2.45mpa, and the linear shrinkage coefficient can be reduced to 0.32%. Another Japanese company used polyvinyl acetate (denkaasrm4) as a low shrinkage additive to develop a molding compound with a shrinkage rate of only 0.096%.
（2） Corrosion resistant resin
The corrosion resistant resins include bisphenol a type unsaturated polyester, isophthalic acid type resin and rosin modified unsaturated polyester. It is reported that 8250 vinyl ester resin developed by a Japanese company not only has good corrosion resistance, but also has a storage life of 14 months. In Japan, the glass fiber composite with 25% NaCl solution resistance was made by isophthalic, bisphenol A or vinyl ester unsaturated polyester resin.
More and more attention has been paid to the strength and toughness resin. At present, saturated resin is mainly used to improve the toughness in foreign countries. Such as adding saturated polyester, SBR and carboxyl terminated NBR. A company in the United States uses unsaturated polyester with hydroxyl end to react with diisocyanate to make the resin. Its toughness can be increased by 2-3 times, and its trade mark is xycon. SD resin developed by a Japanese company has good toughness and can be widely used to manufacture artificial marble. In Brazil, flexible polysiloxane segments (APTS) were grafted onto unsaturated polyester resin containing glycidyl methacrylate (GMA) to obtain high impact resin and glass fiber reinforced resin.
The University of Poland found that the viscosity of TDI modified unsaturated polyester resin increased with the increase of TDI content. When the TDI content reached 3%, the resin had good thixotropy. When 4,4-bismaleimide-diphenylmethane (BM) was added into the resin, the compressive strength of the modified resin was increased to 159mpa, the glass transition temperature was 184 ℃, the decomposition temperature was increased to 280 ℃, and the curing speed was also increased accordingly.
（3） Unsaturated polyester resin with low water absorption
As for the low water absorption type of unsaturated polyester resin, IR radiation curing unsaturated polyester resin is made in Germany. When IR radiation curing, the curing residence time of the composite is short, and the water absorption of the product is reduced.
The transparent unsaturated polyester resin, developed by a Japanese company, is a bisphenol a transparent unsaturated polyester resin artificial marble with tensile strength of 44.1mpa, transmissivity of 48%, and good heat resistance. The unsaturated polyester resin with low free styrene residue has been developed, which can be used as FRP, SMC and BMC resin. The mass fraction of residual styrene after curing at 130 ℃ is only 0.03%.
There are many achievements in pet type unsaturated polyester resin. In the United States and Egypt, the unsaturated polyester resin was synthesized from the waste of pet (polyethylene terephthalate) by alcoholysis. By adjusting the reaction, the curing temperature is 74-90 ℃, and the curing time is only a few minutes to more than 20 minutes, which can be selected arbitrarily.
South Korea has synthesized a series of unsaturated polyester resins obtained from various alcohols, and controlled the alcoholysis degree of PET by various alcohol compositions, and controlled the gel time and brittleness of PET unsaturated polyester resin. It has been successfully applied to SMC and BMC.
The foaming unsaturated polyester resin is also in the eye. Unsaturated polyester resin is used as the matrix foam. Its toughness and strength are better than that of foamed PS. Processing is easier than foam PVC. Adding flame retardants can also make it flame retardant and aging resistant, lower cost than foam polyurethane plastics.
Chemical foaming agent is mainly used in the foaming of unsaturated polyester resin. There are few literatures on the use of physical foaming agents. Physical foaming agent is mainly Freon but pollutes the environment. Chemical foaming agents mainly include isocyanates, azo, sulfonylhydrazides and carbonate anhydrides.
（4） Low volatile resin
There are many varieties of low volatile resin and gel coat resin. Low volatile resin is a subject being developed in foreign countries. 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 the volatilization of styrene; adding high boiling point crosslinking agent to replace styrene; using cyclopentadiene and its derivatives combined with UPR to make low molecular weight, so as to reduce the use of styrene.
A new assistant lpx-5500 developed by foreign companies can reduce the volatilization of styrene by 70-90%.
Gel coat resin is a special resin for making gel coat of FRP products. Styrene is still the most suitable monomer for up resin. However, the vapor pressure of styrene at room temperature is high, and it is easy to volatilize, especially in the process of using hand paste or spray molding technology to make the gel coat layer of FRP products and the backing reinforcement layer.
When the vapor concentration exceeds a certain amount (& gt; 50ug / g), it will stimulate the eyes and nose mucosa and cause dizziness, nausea and other symptoms. Therefore, it is very necessary and significant to develop low styrene dispersive gel coat resin.
A technology company in the United States has developed a low VOC UPR composition containing maleic anhydride monomer and used in gel coatings, adhesives, laminated resins or molding resins. Unsaturated polyester resins and their compositions without styrene monomer have been developed in the United States and Germany. They can be used in open casting, gel coating and electronic industry.
(five) WCUP
Water unsaturated polyester resin WCup is emerging. Water unsaturated polyester resin WCup is a new type of resin with water as filler, which came out in 1950s. In addition to its remarkable low cost characteristics, the resin also has many excellent properties, such as small heat release, small volume shrinkage, flame retardant and easy processing.
It can be used for artificial wood, decorative materials, foam products, porous materials, building materials, polyester concrete, wetting agents and coatings.
In 1967, the first time reported that sodium hydroxide and other alkaline substances were used to prepare stable aqueous unsaturated polyester resin emulsion. This method is called polyester salt formation. In recent years, the study of multiphase / multicomponent polymer systems by dynamic method has attracted great attention in the world, and the relationship between dynamic rheological behavior and morphology has been studied. After that, this kind of research has become a hot topic in the rheology of many polymer systems.
Source: composite community
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