Introduction to Polymer

To familiarize yourself with the methods of producing polymer materials, it is important to understand that polymer and plastic are two different concepts. Plastic is a product resulting from various processes on a polymer. In contrast, a polymer is shaped as a raw material under pressure, heat, and molding to be used in various industries for producing plastic products. Polymers are available in various types such as polyethylene, polypropylene, etc., each having different characteristics based on their chemical specifications. The widespread application of polymers in various industries has led to this raw material being produced in various ways. Generally, for polymer production, initial specifications such as the type of polymer resin, production volume, required strength, and geometric shape are considered so that the desired polymer can ultimately be produced using one of the available methods.

In general, the methods of shaping polymers depend on the following factors:

Type of polymer resin

Geometric shape of the final product

Required strength

Volume of production

When selecting production methods, the mentioned factors must be carefully considered. The methods most commonly used for producing polymer materials include:

Extrusion

Blow molding

Injection molding

Rotational molding

Thermoforming

In all polymer production methods, the material must first be heated to reach the softening (melting) temperature; at this stage, the material is ready for proper shaping. Understanding the behavior of each type of plastic material at high temperatures is crucial, and for example, the melt index or melt flow rate is the most common method for examining the behavior of these materials.

Next, we will provide a complete description of these processes.

Extrusion

Extrusion is a flexible and practical process for shaping polymer materials, where the necessary force for this work is provided hydraulically or mechanically. In summary, the process during which the polymer material passes through a mold of a specific shape under pressure and reduces its cross-section is called extrusion. This process is relatively new and more practical compared to other shaping methods.

In extrusion, granules or plastic powder, masterbatch, and other additives are mixed together and fed into the hopper of the extruder. Then, this mixture is melted in the extruder based on heat and shear stresses and moves towards the mold with the screw motion. The molten product is shaped under pressure into the desired mold and finally, the mold is cooled, and the product is removed. It is one of the most well-known methods for producing plastic materials.

Using this method, a wide variety of plastic products such as wire insulation, packaging nylon, food-grade bags, pipes and profiles, greenhouse coverings, etc., can be produced.

Advantages of the Extrusion Method:

Cooling the piece after leaving the mold

Ability to produce thin parts

Simplicity of the production process

Injection Molding

To produce plastic materials using this method, great attention must be paid to how the polymer materials melt so that the product in the discontinuous production process of injection molding has suitable quality. In various methods of producing polymer materials, the process occurs according to the capacity of the raw materials under specific conditions, where in this method, attention must be paid to maintaining pressure and temperature during the product's production. In the use of plastic production methods, the produced product may require modifications that are carried out during various finishing processes. However, in injection molding, due to the high precision of the production process, the product is produced in one step at high speed and has suitable quality. In various polymer production methods, the dimensions of the produced products are of high importance, and there may be dimensional limitations in some methods.

Whereas injection molding has no limitations for producing plastic products and can assist in producing small items such as bottle caps, kitchenware, toys, etc., alongside larger products such as car bodies.

Advantages of the Injection Molding Method

Mass production capability

Ability to incorporate metal materials into plastic

No need for modifications after the part is produced

Ability to reuse waste

Rotational Molding

Various production methods with different performances are always in competition, and usually, the method that produces high-quality products at a more economical cost receives more attention. In the rotational molding method, the shaping of the polymer is done at a high speed, resulting in hollow products with thin walls that are produced and utilized. The operation of this device is such that sometimes in the production process of certain parts, only this device is used. The rotational molding method has many differences among various polymer production methods and typically produces plastic goods through four stages: filling the mold, heating, cooling, and product discharge. Major applications of this plastic production method include producing automotive parts, toys, various dolls, tanks, etc.

Advantages of the Rotational Molding Method

Low equipment costs

Low waste amount

Ability to produce multi-layer parts

Ability to produce hollow parts

Easy process for separating the part from the mold

High resistance

Blow Molding

In familiarizing with the methods of producing polymer materials, in addition to the type of raw materials and their characteristics, attention must also be paid to other factors such as the geometric shape of the produced product. In the blow molding method, hollow products such as various beverage bottles, cans, pipes, tanks, etc., can be produced. The blow granules enter the extruder as hollow cylinders and after melting, are directed towards the walls with the help of air pressure in the mold. After applying cold to the mold, the cooled polymer takes the shape of the mold and is removed from it.

Advantages of the Blow Molding Method

Uniform mixing and melting of polymer materials

Ability to use thermoplastic in the production process

Low cost of mold preparation

Thermoforming

The aforementioned methods each contribute to the production of plastic products through the molding process. In contrast, thermoforming is a method of shaping raw materials that leads to the production of plastic products. In this method, the polymer material in sheet form reaches its softening point due to heat and is prepared for reshaping.

Then, under the application of positive or negative air pressure, the materials move towards the mold walls and take the shape of the mold.

After shaping, the piece is removed from the mold, and with the help of trimming operations, its waste is separated, and necessary modifications are made.

Among various polymer production methods, this method, with high precision and low cost, is a suitable method for mass production, and purchasing its initial equipment is also a very easy and low-cost task.

Advantages of the Forming Method

Suitable for low-volume production

Ability to produce multi-layer parts

No expensive equipment required

Low cost of molds

Applicable in producing various plastic molds

Conclusion

Considering the diversity of polymers and the possibility of producing plastic products in high variety, it is better to choose a method that, taking into account the complete production needs of the collection, helps you produce your desired product with fewer stages and with suitable precision and quality.

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