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What effect unsaturated polyester resins do have on human body ?

Jan 26, 2019

The unsaturated polyester is a polycondensation of an unsaturated dicarboxylic acid (or anhydride) or a mixed acid thereof and a saturated dicarboxylic acid (or anhydride) with a polyol, and has a linear form of an ester bond and an unsaturated double bond. Polymer compound. Usually, the polyester polycondensation reaction is carried out at 190 to 220 ° C until the desired acid value (or viscosity) is reached. After the end of the polyesterification reaction, a certain amount of vinyl monomer is added while hot, and a viscous liquid is formed. Such a polymer solution is called an unsaturated polyester resin. Physical and chemical properties of unsaturated polyester resin 1. Physical properties The relative density of unsaturated polyester resin is about 1.11 to 1.20. The volume shrinkage during curing is large. Some physical properties of the cured resin are as follows: (1) Heat resistance . Most of the unsaturated polyester resins have a heat distortion temperature of 50 to 60 ° C, and some resins with good heat resistance can reach 120 ° C. The red thermal expansion coefficient α1 is (130 to 150) × 10 -6 ° C. (2) Mechanical properties. The unsaturated polyester resin has high strength such as stretching, bending, and compression. (3) Chemical resistance. Unsaturated polyester resin has good performance against water, dilute acid and dilute alkali, and has poor resistance to organic solvents. At the same time, the chemical resistance of the resin can vary greatly depending on its chemical structure and geometrical switch. (4) Dielectric properties. The dielectric properties of the unsaturated polyacid resin are good. 2. Chemically unsaturated polyester is a linear polymer compound having a multifunctional group having a polyester chain bond and an unsaturated double bond in its main chain, and a carboxyl group and a hydroxyl group at both ends of the macromolecular chain. . The double bond on the main chain can be copolymerized and crosslinked with the vinyl monomer to convert the unsaturated polyester resin from a soluble, fusible state to an insoluble, infusible state. The ester bond on the main chain can undergo a hydrolysis reaction, and an acid or a base can accelerate the reaction. When copolymerized with styrene, the hydrolysis reaction can be greatly reduced. In acidic media, hydrolysis is reversible and incomplete, so polyester can withstand the attack of acidic medium; in alkaline medium, due to the formation of a resonance-stable carboxylate anion, hydrolysis becomes irreversible, so polyester is resistant to alkali. Poor sex. The carboxyl group at the end of the polyester chain can react with an alkaline earth metal oxide or hydroxide [e.g., MgO, CaO, Ca(OH)2, etc.) to expand the molecular chain of the unsaturated polyester, eventually forming a complex. The molecular chain extension can be such that the initial viscosity is 0.1 to 1.0 Pa·s of a viscous liquid resin, and the viscosity is sharply increased to 103 Pa·s or more in a short period of time until it becomes a non-flowable, non-sticky gel-like substance. When the resin is in this state, it is not crosslinked, it is soluble in a suitable solvent, and has good fluidity when heated. Relationship between structure and properties of unsaturated polyester resin. So far, unsaturated polycondensation as a composite matrix at home and abroad. The ester (resin) matrix is basically a phthalic acid type (abbreviated as o-benzene type), an isophthalic acid type (referred to as an isophthalic type), a bisphenol A type and a vinyl ester type, a halogenated unsaturated polyester resin, or the like. . 1. The o-benzene type unsaturated polyester and the isophthalic unsaturated polyester phthalic acid and isophthalic acid are mutually isomers, and the unsaturated polyester molecular chains synthesized by them are o-benzene type and m-benzene respectively. Types, although their molecular chain chemical structures are similar, the meta-benzene type unsaturated polyester has the following characteristics compared with the ortho-phenyl type unsaturated polyester: 1 higher molecular weight can be obtained by using isophthalic acid dicarboxylic acid. The isophthalic acid unsaturated ester ester gives the cured product better mechanical properties, toughness, heat resistance and corrosion resistance; the purity of the 2 isophthalic acid polyester does not remain in the resin. And low molecular weight isophthalate impurities; the ester bond on the molecular chain of the 3 isophthalic acid polyester is protected by the steric hindrance effect of isophthalic acid, and the ester bond on the molecular chain of the phthalic acid polyester is more susceptible. Invasion of water and various other corrosive media, glass fiber reinforced plastics made with isophthalic polyester resin have a relatively high performance after being immersed in a saturated sodium chloride solution at 71 ° C for one year. 2. The bisphenol A type unsaturated polyester bisphenol A type unsaturated polyester is easily hydrolyzed in the molecular chain compared with the chemical structure of the o-benzene type unsaturated polyacid and the isophthalic type unsaturated polyester macromolecular chain. The spacing between the broken ester bonds is increased, thereby reducing the density of the ester bond; the bisphenol A unsaturated polyester and the cross-linking agent such as styrene have a large space effect after curing, and the ester group is shielded and protected, hindering the ester. The hydrolysis of the bond; while the neopentyl group in the molecular structure is linked to two benzene rings, maintaining the stability of the chemical melon, so the resin has good acid, alkali and hydrolysis resistance. 3, vinyl resin Vinyl resin, also known as epoxy acrylic resin, is a new type of resin developed in the 1960s, which is characterized by a terminal unsaturated double bond in the polymer. Vinyl resin has good comprehensive properties: 1 Since the unsaturated double bond is located at the end of the polymer molecular chain, the double bond is very active, and is not affected by the space barrier during curing, and can be passed through the phase under the action of the organic peroxide. Cross-linking curing between adjacent molecular chains, and poly-curing with monomeric styrene; 2 R groups in the resin chain can shield ester bonds, improve chemical resistance and hydrolysis stability of ester bonds; 3 vinyl resin In the medium, the ester bond in the relative molecular mass per unit is about 35% to 50% less than that in the ordinary unsaturated polyester, thus improving the hydrolytic stability of the resin in the acid and alkali solution; 4 the secondary hydroxyl group on the resin chain It has the wettability and cohesiveness with glass fiber or other fiber to improve the strength of the composite; 5 epoxy resin main chain, which can impart vinyl toughness, and the ether bond in the molecular main chain can make the resin have excellent acid resistance. Sex. The variety and properties of vinyl resins vary widely depending on the materials used. The molecular structure can be designed according to the requirements of the composites for resin properties. 4. Halogenated Unsaturated Polyester The halogenated unsaturated polyester refers to a chlorinated unsaturated polyester synthesized from chlorinic anhydride (HET anhydride) as a saturated dibasic acid (anhydride). The chlorinated unsaturated polyester resin has been used as a resin having excellent self-extinguishing properties. However, recent studies have shown that chlorinated unsaturated polyester resin also has quite good corrosion resistance. Its corrosion resistance in the above media is basically the same as that of bisphenol A unsaturated polyester resin and vinyl resin, but in some The corrosion resistance in the case (for example, wet chlorine) is superior to that of the vinyl resin and the bisphenol A unsaturated polyester resin. The hot wet chlorine reacts after contact with the unsaturated polyester resin to produce a chlorinated unsaturated polyester resin or "chlorine cream". The "chlorine cream" property is softened by the bisphenol A unsaturated polyester resin and the vinyl ester resin, and the wet chlorine can be further (corrosive) infiltrated through the "chlorine cream" layer, but the "chlorine cream" is produced from the chlorinated unsaturated polyester. "The character is hard and can prevent further (corrosive) penetration of wet chlorine. Most of these resins contain a benzene ring, but since they have a substituent on the benzene ring, they are easily metabolized into the human body, so the damage to the human body is greatly reduced relative to benzene, and it is low in toxicity. In addition, halogenated hydrocarbons also have certain toxicity, which is also harmful to the human body and the environment.

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Neweco is one of the leading unsaturated polyester resin manufacturers and  suppliers,widely used in automobiles, ships, rail transit, wind power  generation, pipe cans, heat and corrosion protection, building  materials, stone repair, sanitary ware, artificial stone and other  industries. Suitable for hand lay-up, spray, pultrusion, winding,  molding, vacuum introduction / RTM, casting and other molding processes. Neweco Resin is committed to excellence and focuses on the application  of composite materials to provide customers with comprehensive  solutions.

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