What is injection molding of plastic materials

Injection molding is a manufacturing process that is widely used to create plastic parts. There are two macro-families of plastic materials: thermoplastics and thermosets. In injection molding the polymers (both thermoplastic and thermosetting) are melted inside a cylinder equipped with a worm screw, and subsequently injected at high pressure inside a mold where the material solidifies, taking the shape of the mold cavity.

The injection molding process offers several advantages over other manufacturing methods. First, it allows you to produce parts with high precision and repeatability, with a high quality finish. Furthermore, the production of parts in large quantities becomes very efficient, since injection molding machines are able to produce a large number of parts quickly and consequently at a low cost. Finally, the injection molding process is very flexible and can be used to produce parts in different plastic materials, with a wide range of geometries and designs.

For over 30 years, Ludabak has been involved in the injection molding of thermoplastics and thermosets. We are among the few companies globally that can boast the ability to transform both of these families of materials without distinction. This provides customers who choose us the opportunity to explore more technological solutions for their projects. With increasing frequency, the technical offices of multinational companies turn to us for support in choosing the most suitable materials.

How it works

So let’s go and describe in detail the phases that make up this molding method to understand how it is articulated.

Initially, the plastic to be processed in the form of powder or granules is introduced into an injection molding machine. Granules and powder are subsequently plasticized or melted inside a cylinder, in which the rotation of a screw together with the temperature of the cylinder, bring the plastic into liquid form awaiting the injection phase.

After being melted, the material is pushed into the mold through a specific channel. At this point, using ramifications, the compound reaches the mold cavity. It is here that we proceed with the conditioning of the material (in fact the mold can be both cooled and heated according to the specific material we are working with) and subsequent hardening of the molten polymer. The whole process ends with the opening of the mold from which the final product is obtained.

Thermosetting Materials

Thermosetting materials are those which, after solidifying, cannot be melted again and are usually ground and reused as an inert filler.

In fact, they are materials which, once solidified through a heating and cooling process, cannot be brought back to the liquid state by further heating because their chemical structure is irreversibly transformed. This makes them resistant to heat and permanent deformation, giving them greater dimensional stability than thermoplastic materials, but their recycling process is more complex and limited.

Phenolic Resin

Phenolic resin is one of the first synthetic plastics used in injection molding. It has good mechanical, thermal and electrical resistance, but is relatively brittle and has low resistance to moisture.

Melamine

Melamine resin is a flame resistant thermosetting material often used in electrical and electronic applications. It is also used in the production of kitchenware and tableware due to its resistance to abrasion and stains.

Epoxy Resin

Epoxy resin is a thermosetting plastic with a unique combination of mechanical, electrical and thermal properties. It is usually used to produce parts that can withstand high temperatures, acids, alkalis and corrosive chemicals. Epoxy resin has good resistance to mechanical stress and has high wear resistance. It is often used in the aerospace and military industries to produce high precision parts.

Graphite Resin

Graphite resin is a graphite-based thermosetting resin and is used to produce parts that require high mechanical properties, such as turbine blades. It has high structural strength and good flame resistance. This material is also used in high temperature applications where most other plastics would fail.

BMC

That is Bulk Molding Compound, a mixture of thermosetting resins, reinforced with glass fibers or other reinforcing materials, which is used for the production of components with high mechanical resistance, good thermal and dimensional stability, which makes them particularly suitable for use in industrial applications, such as the automotive sector.

Thermoplastic materials

Thermoplastics are materials that can be repeatedly melted and re-solidified by heating and cooling. This means that they can be recycled more easily than thermosetting materials, which is done directly during the molding process, where any non-conforming products and scraps are shredded on board the machine and the resulting material is remixed through special equipment in defined proportions and reprinted . Examples of thermoplastics include polystyrene, polyethylene, PVC, nylon and polycarbonate.

ABS (Acrilonitrile Butadiene Stirene)

ABS is a very common thermoplastic used in injection molding. This material is resistant to impact, offers good aesthetic results and above all it is the only thermoplastic material that lends itself to the galvanic process, making it a very versatile material used in aesthetic components. Furthermore, ABS is relatively cheap and is commonly used to produce parts for the automotive industry, electronic appliances, and toys.

PBT (Polibutilene Tereftalato)

PBT is a high strength thermoplastic, mainly used in electronic and engineering applications. This material is resistant to impact and high temperatures, but can be brittle at low temperatures. Additionally, PBT is very resistant to chemicals and abrasion. This material is often used in the production of electronic parts, components of telecommunications systems and connectors and is also added with glass fillers to improve its performance.

PC (Policarbonato)

PC is a high-strength thermoplastic used in high-stress applications, such as parts of electronic devices and lighting elements. PC is resistant to shocks, high temperatures and UV rays, but can be brittle when subjected to high voltages. This material is commonly used for the production of automotive parts, electronic components and sunglasses.

PA (Poliammide)

PA is a thermoplastic used in a wide range of applications, including automotive parts, electronic appliances and components for the mechanical industry. This material has good resistance to abrasion and moisture. Furthermore, PA has good resistance to fatigue, so it is often used in components that have to undergo mechanical stress.

PP (Polipropilene)

It’s a lightweight, strong thermoplastic that is used in a wide variety of applications including food containers, packaging, medical products and textiles. PP is impact resistant, but can be vulnerable to UV light. It is an easily workable material, it has a low cost. Furthermore, PP is highly resistant to fatigue and deformation.

In conclusion, each material family has its own specific characteristics, and a wide range of materials to choose from within them. Thermosetting materials are often used to produce parts with high mechanical, thermal and electrical resistance, while thermoplastic materials are used to create parts that require impact resistance, low cost and thin gauges.

Contact our technical office for more information, if you have any doubts about the geometries and materials to apply to your new product we will be happy to assist you.

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