Introduction

"Polyester" is a class of polymer compounds containing ester bonds that are distinguished from resins such as "phenolic" and "epoxy". This polymer compound is produced by polycondensation reaction of dibasic acid and diol, and when this polymer compound contains unsaturated double bonds, it is called unsaturated polyester. This unsaturated polyester dissolves In polymerizable monomers (usually styrene)

When it becomes a viscous liquid, it is called unsaturated polyester resin (English name Unsaturated Polyester Resin, UPR for short).

Therefore, unsaturated polyester resin can be defined as a linear polymer compound containing unsaturated dibasic acid or diol, which is formed by polycondensation of dibasic acid and dibasic alcohol, dissolved in monomer (usually styrene) and into a viscous liquid.

Unsaturated polyester resin, which accounts for 75% of the resins we use every day.

characteristic

Unsaturated polyester resin is a kind of thermosetting resin, which can be cured into an insoluble and infusible high molecular network polymer under the action of heat or initiator. However, the mechanical strength of this polymer is very low and cannot meet the requirements of most applications. When reinforced with glass fiber, it can become a composite material, commonly known as "glass reinforced plastic" (English name Fiber Reinforced Plastics, FRP for short). Compared with the resin casting body, the mechanical strength and other aspects of "glass fiber reinforced plastic" have been greatly improved.

The glass fiber reinforced plastic (UPR-FRP) based on unsaturated resin has the following characteristics:

Lightweight and high strength

The density of FRP is 1.4-2.2g/cm3, which is 4-5 times lighter than steel, but its strength is not small, and its specific strength exceeds that of steel, duralumin and fir. This is of great significance for products that need to reduce their own weight, such as aviation, aerospace, rockets, missiles, ordnance and transportation. For example, the FRP components used in the main structure of the Boeing 747 jetliner are up to 2.2 tons, which effectively saves aircraft fuel, improves the speed, prolongs the endurance time, and increases the payload.

Good corrosion resistance

UPR-FRP is a kind of good corrosion-resistant material, which can withstand common concentrations of acids, alkalis, salts, most organic solvents, sea water, air, oils, and is also highly resistant to microorganisms. It is widely used in petroleum, Chemical industry, pesticide, medicine, dyestuff, electroplating, electrolysis, smelting, light industry and other fields of national economy play an irreplaceable role of other materials.

Excellent electrical performance

UPR-FRP has excellent insulation properties and can still maintain good dielectric properties under high frequency action. It does not reflect radio waves, is not affected by electromagnetic effects, and has good microwave permeability. It is an ideal material for making radomes. Using it to manufacture instruments, motors, and insulating parts in electrical products can improve the service life and reliability of electrical appliances.

unique thermal properties

The thermal conductivity of UPR-FRP is 0.3-0.4Kcal/mh℃, which is only 1/100-1/1000 of that of metal. It is an excellent thermal insulation material. The doors and windows made of it are the fifth generation of new energy-saving building materials. In addition, the FRP linear expansion coefficient is also very small, which is close to that of general metal materials, so the connection between FRP and metal will not cause stress due to thermal expansion, which is conducive to its bonding with metal substrates or concrete structures.

Excellent processing performance

UPR has excellent processing performance, simple process, and can be molded at one time. It can be molded at room temperature and pressure, and can be cured under heat and pressure. In addition, no low-molecular by-products are generated during the curing process, and relatively uniform products can be produced. Due to its excellent process performance, it has been widely used in non-glass fiber reinforced materials such as handicrafts, imitation marble products, and polyester paint in recent years.

Good material designability

UPR-FRP is a composite material with UPR as the matrix and glass fiber as the reinforced aggregate. The two are processed into the final shape of the product after one-time processing. So FRP is not only a material, but also a structure. The so-called designability includes two aspects: (1) functional design; FRP products with various special functions can be made by selecting appropriate UPR and glass fibers, such as: it can be made into corrosion-resistant products; High-temperature products; can be made into light-transmitting plates; can be made into fire-resistant and flame-retardant products; FRP grating, FRP pipe, FRP tank, FRP tank, etc.

No material is omnipotent, and FRP is no exception. First of all, FRP has many essential differences compared with metal. For example, metal is an isotropic material, while FRP is an anisotropic material. Under stress, metal is generally divided into two stages: elastic deformation and plastic deformation, while FRP is under stress Under the action, there is generally no significant plastic deformation stage, no yield point, and there is delamination during the stress process, and it is easy to break suddenly when overloaded. Secondly, the modulus of FRP is low, which is 10 times worse than that of steel, so products with high rigidity requirements must be carefully designed. Third, the heat resistance of FRP is much lower than that of metal materials. So far, the long-term use temperature of FRP is only limited to below 200°C.

use

The use of unsaturated polyester resin

According to specific special varieties, it includes winding resin, spray resin, RTM resin, pultrusion resin, SMC, BMC resin, flame-retardant resin, food-grade resin, anti-corrosion resin, air-drying resin, Polaroid resin, handicraft resin, Button resin, agate resin, artificial stone resin, highly transparent resin crystal resin, putty resin, etc.

Anti-aging flame retardant gel coat, heat-resistant gel coat, spray gel coat, mold gel coat, non-cracking gel coat, radiation curing gel coat, high wear-resistant gel coat, etc. as FRP surface decoration.

According to the structure of unsaturated polyester resin, it can be divided into o-phthalic type, m-benzene type, p-phenylene type, bisphenol A type, vinyl ester type, etc.;

According to its performance, it can be divided into general-purpose type, anti-corrosion type, self-extinguishing type, heat-resistant type, low shrinkage type, etc.;

According to its main use, it can be divided into two categories: glass fiber reinforced plastic (FRP) resin and non-glass fiber reinforced plastic resin. The so-called FRP products refer to various products made of resin with glass fiber and its products as reinforcing materials, also known as glass fiber reinforced plastics (FRP or FRP for short); non-FRP products are resins mixed with inorganic fillers or used alone Various products made of fiberglass are also called non-reinforced FRP products.

UPR's FRP products are widely used in the following fields:

Construction field: Cooling towers, 8m3/h-3000m3/h cross-flow, counter-flow, spray towers and accessories such as air ducts, fans, and water eliminators. Doors, windows, light lighting buildings, grilles, mobile rooms, cold storage, park pavilions, platforms, newsstands, etc.

Anti-corrosion products and projects such as glass steel pipes, tanks and tanks: including large, medium and small-diameter pipes, pipe fittings, valves, storage tanks, storage tanks, grilles, filling plates, towers, chimneys, anti-corrosion floors and building anti-corrosion, etc.

FRP vehicles: train double-decker passenger cars and parts, window frames, car bodies, bumpers, train air ducts, spring plates, etc.

FRP boats: including yachts, lifeboats, traffic boats, fishing boats, speedboats, sampans, breeding boats, assault boats, etc.

FRP amusement equipment: including large amusement machines, large water parks, and children's playgrounds.

FRP transportation equipment, labor insurance and security supplies: including road signs, road signs, footbridges, lamps, cable boxes, measuring scales, helmets, kiosks, explosion-proof equipment, manhole covers, etc.

FRP Sanitary Equipment: Bathtub, washstand, toilet, mirror frame, overall toilet, trash can.

Energy-saving FRP products; including axial fans, centrifugal fans, solar water heaters, wind generators, etc.

FRP food containers: high-level water tanks, food transport tanks, beverage cans.

Fiberglass urban sculptures, fonts, handicrafts and bone crafts.

Fiberglass furniture: including seats, fast dining tables, complete sets of furniture, telephone booths, counters, etc.

FRP electromechanical, mining, light textile products: including protective covers, grilles, dry-type transformers, transformers, high-voltage pull rods, computer rooms, electrical switches, SMC satellite antennas, copper foil plates, clothing models, ventilation pipes, cotton sliver cans wait.

Fiberglass sports equipment and music and dance equipment: including tennis rackets, parallel bars, horizontal bars, springboards, rowing boats, props, etc.

The non-glass reinforced plastic application fields of UPR are roughly as follows:

Including crystal handicrafts, opaque various modeling handicrafts, etc.

Buttons: various polyester button products.

Artificial stone: including artificial marble, artificial agate, artificial granite, etc.

Coating: including furniture coating, piano, TV, radio casing, sewing machine table and bicycle varnish, etc.

Putty: Polyester putty for car repair, etc.

Others: including anchoring agent, electrical casting, toughening agent, adhesive, etc.

curing mechanism

From the perspective of chemical kinetics of free radical polymerization, the curing of UPR belongs to free radical copolymerization. The curing reaction has the characteristics of four radical reactions of chain initiation, chain growth, chain termination and chain transfer.

Chain Initiation--The process from the decomposition of a peroxide initiator to form a free radical to the addition of this free radical to an unsaturated group.

Chain Growth - The process by which monomers are continuously added to newly generated free radicals. The activation energy required for chain growth is much lower compared to chain initiation.

Chain Termination - Two free radicals combine to terminate the growing polymeric chain.

Chain transfer - a growing large free radical can interact with other molecules, such as solvent molecules or inhibitors, so that the original active chain disappears and becomes a stable macromolecule, while the original inactive molecule becomes a free radical.

Molding

1) Hand lay-up process;

2) Injection molding process;

3) Casting molding process;

4) Fixed-length winding process;

5) Continuous winding pipe making process;

6) Pultrusion molding process;

7) Bag pressure method (pressure bag method);

8) Sheet molding process;

9) Group packaging molding process;

10) Vacuum Assisted Lightweight RTM (L-RTM)