Unsaturated polyester

a) Unsaturated polyester resin
The English abbreviation of unsaturated polyester is UP. Pure UP is a linear thermoplastic polymer, which is different from saturated polyester (PBT, PET) in that its macromolecular backbone contains unsaturated ethylene double bonds, which are easy to oxidize, and can be cross-linked and polymerized with other ethylene monomers through addition reactions to form thermosetting bulk polymers, so ethylene monomers are commonly used as cross-linking agents.
The appearance of UP products is hard, brown and translucent, and it fluoresces blue under ultraviolet light. The relative density is 1.2~1.3, the water absorption rate is 0.1%~1%, and it is highly impermeable to water vapor.
The mechanical properties of UP are high, and the tensile strength of pure UP products is 40~90MPa, which can reach 250~350MPa after being reinforced with glass fiber.
The general use temperature of pure UP products is 100°C, and it can reach 200°C after enhancement.
The chemical resistance of UP is average, it is not resistant to the oxidation of oxidizing media, and it is not good to resist ordinary acids, alkalis and solvents.
(2) Unsaturated polyester plastics
UP has no volatiles escaping during processing and curing, and can be formed at room temperature and pressure. It has high curing reaction ability, extremely convenient processing, and can be molded by injection molding, casting, pressing, hand lay-up, winding, spraying and other methods.
The various properties of pure UP are not ideal, so it is generally rarely used as a plastic product alone, and is mainly used as a coating. Commonly used UP plastic products are modified by adding fillers or reinforcing materials to them. UP's glass fiber reinforced plastic, also known as "FRP", is the most commonly used modified product of UP, and its dosage can account for more than 80% of the entire UP plastic.
1. Filling products
The amount of UP filler products is not large, but it has a wide range of applications. Commonly used fillers are: stone powder, mica powder, glass powder, quartz powder, porcelain powder, calcium carbonate and slag. The molding methods mainly include casting, pressing, etc.
UP can be used for hot casting, similar to phenolic casting, and the hardness is higher than phenolic, and the color is lighter, which can be used to make decorative products, buttons, knife handles, brush handles, and umbrella handles.
UP has good compatibility with inorganic fillers and can be filled in large quantities, so it is suitable for the production of imitation products, such as artificial marble, artificial agate, etc.
UP has good electrical insulation and can be cured at room temperature, and can be widely used in the molding of electronic components and electrical components, such as capacitors, complete sets of miniaturized circuits, small transformers and transformers.
2. Enhanced products
The mechanical properties of UP FRP are very high, close to metal in some aspects, and the tensile strength is nearly twice as high as that of steel, and the relative density is only 1.7~1.9, which is 1/4~1/5 of structural steel and 2/3 of aluminum alloy, and has very excellent specific strength, which can be widely used as structural materials. In addition, UP reinforced products also have the advantages of good toughness, high heat resistance and high temperature.
There are many forming methods for UP FRP, including hand lay-up method, winding method, pressing method and injection molding method. Among them, the compression molding method has developed rapidly, and can be divided into two types: sheet molding compound and block molding compound according to the different product structure and processing methods.
UP FRP can be widely used in the following aspects:
(1) Automotive industry UP FRP has many uses in automobiles, including bumpers, body dash panels, front radiator covers, water tank masks, fuel tanks, water inlet pipes, dashboards, engine covers and luggage compartments.
(2) Electronics industry: electrical housing, arc shield, arc extinguishing board and printed circuit board.
(3) Building materials: high-level water tank, bathtub, washbasin, integral bathroom, etc.
(4) Chemical equipment: all kinds of storage tanks, pipelines, runners and pump housings, etc.
(5) Other seats, dining tables, aircraft parts, small boats, large shells and ventilation ducts, etc.