Name | Unsaturated polyester |
Synonyms | Unsaturated polyester |
overview
It is mainly formed by polycondensation of unsaturated and saturated dibasic acid (anhydride) and polyol at 190~220 ℃ and acidic conditions. The crosslinking agent with vinyl structure is generally added to the product. In order to improve the storage period, a certain amount of polymerization inhibitor is usually added. The appearance of unsaturated polyester is viscous colorless or yellowish liquid. After adding additives, fillers, initiators and accelerators during use, the resin is formed by crosslinking reaction. According to the type of accelerator, the surface of the cured resin is colorless or brown translucent. There are many varieties of unsaturated polyester. In the process, only the properties of diols and dibasic acids used in the polycondensation reaction and the composition of ethylene monomers and additives can be changed to produce universal type, toughness, flexibility, and light Stability, photosensitive type, corrosion resistance type, self-extinguishing type, flame retardant type, pouring type, low volatilization type and other varieties. The structural formula of universal unsaturated polyester is as follows:
where: R1 diol R2 phthalic anhydride R3 maleic anhydride
Unsaturated polyester products are hard, rigid, insoluble and insoluble. Modified unsaturated polyester products have heat resistance, flame resistance, chemical resistance, atmospheric aging resistance, and light transmittance.
unsaturated polyester is mainly used as glass fiber reinforced plastic, mainly used in construction, chemical industry, anti-corrosion, shipping, transportation and so on. Unsaturated polyester can also be used to make coatings, cement, compression molding powder, cast plastics, sanitary ware, artificial agate, artificial marble, buttons, electrical sealing materials, etc.
Advantages and disadvantages of unsaturated resins
Unsaturated polyester resin, whose molecular structure contains non-aromatic unsaturated bonds, can be used to initiate a crosslinking reaction with an appropriate initiator to become a thermosetting plastic. Unsaturated polyester molecules are long-chain molecules before curing, and their molecular weight is generally 1000~3000. This long-chain molecule can be crosslinked with unsaturated monomers to form a huge network structure with complex structure. After curing, unsaturated polyester resin is mainly formed into an uneven continuous network structure, and there are chain-type molecules with lower density between the dense continuous networks.
Advantages of UPR:
1. good formability and manufacturability, viscosity, thixotropy, pot life, air dryness, etc. can be adjusted. Through the selection of the type and quantity of initiators, it can be cured in any time from normal temperature to any temperature of 160 ℃, and no by-products are produced. The size and quantity of the corresponding products can be selected by various molding methods to meet different Uses and requirements;
2. It has good mechanical properties, corrosion resistance and electrical properties. Recently, a high-strength impact-resistant and low-shrinkage sheet molding compound resin modified with urethane has been developed, and a resin with good electrical properties at high temperature has been developed;
3. Free coloring, easy to paint and add gel coating, so that the product has a variety of colors;
4. Easy to combine with different reinforcing materials and fillers to obtain composite products with different characteristics;
5. Low price and a series of ways to reduce costs, easy to invest in production.
the disadvantages of the original UPR include more styrene, which is irritating to human eyes, trachea and mucosa. Poor flame retardancy; Large shrinkage. At present, UPR with low styrene content can be achieved by improving the formula, and the oxygen index of flame retardant UPR can reach more than 40%, thus UPR with low shrinkage can be produced.