Thermosetting polymers (TS) contain a resin (a linear polymer with functional groups such as hydroxyl, carboxyl called COOH, amino (NH2), or double bond), which forms the crosslinker and catalyst. Most thermosetting polymers may be used in pure form; For example, mixed with polymer-based composites. Forming thermosetting is done by molding a mixture of thermoset resins with fibers or reinforcers. In some applications, the use of fiberglass for reinforcement is also common. It should be noted that low viscosity formulations reduce production costs and mold costs.

Familiarity with Forming of thermosetting

Familiarity with Forming of thermosetting

Familiarity with Forming of thermosetting

Typical thermoplastic polymers include polyesters, alkyds, amino resins, epoxy resins, and polyurethanes. Thermostats contain cross-links that make them resistant to heating to high temperatures as well as a creep. However, the impact resistance of thermosetting polymers is low.

Forming of thermosetting polymers is the reactive processing of prepolymers or monomers with a catalyst or a curing agent as part of the forming process. These include:

  • Compression or transition molding
  • Injection molding
  • Injectable-reactive molding
  • Vacuum injection
  • Distribution of resin or foam
  • Autoclave molding and resin transfer
  • SMC / DMC molding
  • Filament tail

Introduction of various methods of Forming thermosetting polymers

As mentioned, there are 8 different methods for molding thermosetting polymers. In the following, we will examine these methods in full:

1. Compression molding, the first method of Forming thermosetting polymers

This process is useful for molding DMC / SMC powders or polymers. The mold is placed inside a hydraulic press and heated to a temperature of about 160-200 ° C. The required amount of prepolymer mixed with the catalyst or curing agent is placed inside the mold.

The mold is then closed, then under pressure, the material is sent inside the mold cavities. For SMC, the load is cut into small pieces and after weighing, they are placed inside the mold. The applied pressure on the hot mold causes the formation of thermosetting polymers.

After pressing, the mold is kept closed until processing is complete and cross-links are formed. The process of compression and transfer molding are considered batch processes.

2. Transitional molding

Transitional molding is a type of pressure molding in which a source of molten resin is present. This molten resin enters the mold cavity at the appropriate time.

This method has an advantage over compression molding in applications where a hollow shell is required. In this method, the mold is not pressed directly. Electrical components are usually produced by transition molding.

3. Injection molding

In the injection molding of thermosetting plastics, the method is similar to the method used in the molding of thermoplastic materials; Except that plasticization occurs at very low temperatures and processing is done in the mold.

The material remains in the mold until the processing is done properly and takes the form of a stable state. At this time, the piece is detached from the mold even though it is still hot.

The cycling times required for thermosetting polymers are longer than the cycling times of thermoplastics. The reason for this is the need to perform a chemical reaction in the thermostatic process.

Injection, compression and transfer molding processes are high-pressure molding methods. In addition to these methods, there are low-pressure molding methods used for liquid resins. These methods of Forming thermosetting polymers are mostly used in the production of fiber-reinforced composites.

Vacuum Resin Injection (VARI), Resin Transfer Molding (RTM), or Vacuum Injection Process are some of the low-pressure molding processes in which catalyzed resin is inserted into matched molds.

In this method, the use of vacuum series is used to help inject the resin into the mold. All of these methods depend on the ease of flow of the prepolymer and good wettability with the amplifier.

Differences between Forming of thermosetting polymers and thermoplastic materials

Many thermoset polymers (such as polyurethane, epoxides, silicones, modified polyesters, phenol-formaldehyde, and amino resins) and some thermoplastic polymers (such as modified polyamide 6 and certain acrylics) can be used directly.

These polymers are produced from liquid and low viscosity monomers or pre-polymeric ethers. These precursors are mixed in a certain ratio before processing. Mixing units are equipped with measuring and mixing equipment.

Thermosetting polymers generally have a low viscosity, so when these materials fill the mold under pressure, some of the material leaks through the cavity between the two molds. This creates waste chips.

While this problem can be corrected for injection molding of TPs, by using proper mold structure design and proper determination of process parameters. Of course, unwanted appendages can also be removed by abrasion. Of course, thermosetting waste cannot be recycled; This was possible with thermoplastics.

Conclusion

Thermoset polymers

Thermoset polymers

Thermosetting refers to polymers that cause chemical reactions by applying heat to crosslinks. The result of this process is a change in the average molecular weight of the material with upward growth and the integration of its compounds. These resins are usually in the liquid state and, in combination with a hardener or desiccant, perform an irreversible reaction and harden. Among the types of these resins, we can mention polyester resin, vinyl ester, epoxy, etc.

In this PetroProviders article, we are introduced to the Forming thermosetting polymers methods. These polymeric materials have different advantages: they can withstand loads at higher temperatures and pressures, they have low molecular weight and they are liquid with low viscosity. The use of free radicals makes them solid. They have good thermal stability, good chemical resistance, and a good performance against creep and stress.

What do you think about Forming thermosetting polymers? Are these polymers as popular as thermoplastics? Is the use of these polymers harmful to human health? Are thermosetting polymers recycled? In the comments section, you can tell us your opinions about these polymers.

 


 

Are thermosetting polymers dangerous to human health and the environment?

These polymers are not harmful to human health; But if they become monomers, they will be very harmful. If the thermosetting polymer catches fire, is cut, or hydrolyzed, it may be harmful.

What are some examples of thermosetting polymer?

This polymer is used to produce various plastic devices. Bakelite, Epoxy Resin, Polyamide, Vulcanized Rubber, Silicon Resin, and Duroplast are types of thermosetting polymers.

Are PVC and PET types of thermosetting materials?

Polyvinyl chloride or PVC is a type of thermoplastic material used in the plastics industry. In addition, polyethylene terephthalate or PET is a thermoplastic polymeric material.

What are the applications of thermosetting polymer in industries?

These polymeric materials are used to produce building panels, electronics, durable home appliances, building insulation, and building flooring. The applications of this polymer are due to its high resistance to heat.