Injection moulding processes are widely used in the automotive industry as means of high productivity and precision reducing the cost and time of making plastic parts. What does this process look like, which plastics can be processed and what are the benefits?
Types of plastics used in the automotive industry
A number of different types of plastics are currently used in the automotive industry. They are used in a wide variety of applications depending on their properties. The most common of these are thermoplastics such as polypropylene (PP), polycarbonate (PC) and ABS processed with injection moulding machines. The former is lightweight, chemical- and impact-resistant, so it is used in the manufacture of bumpers, engine covers or door panels. Polycarbonate, on the other hand, is transparent and resistant to mechanical damage, which makes it suitable for the manufacture of headlights. Equally good in terms of mechanical resistance or high temperatures is ABS (Acrylonitrile Butadiene Styrene). Typically, dashboard components and housings are made of it.
Thermosetting polymers are another important group of plastics. These include chemical- and temperature-resistant epoxy resins, which can be found in adhesives and protective coatings. Also included in this group are phenolic resins used in electrical insulation and engine components with resistance to extremely high temperatures and fire.
A third extremely popular group of modern plastics used in cars are carbon or glass fibre reinforced composite materials. The former combine extraordinary strength with ultra-low weight, which is why they work well for vehicle bonnets, for example. The latter, on the other hand, are often used for bumpers or mudguards due to their corrosion resistance.
Plastic injection moulding processes
There are several different plastic injection moulding technologies available for a wide range of automotive components to be produced. The most common method is injection moulding, which involves heating the plastic to a liquid state and then injecting it into a mould under high pressure. Once cooled and hardened, it takes the shape of the mould permanently. This method is used to produce, for example, dashboards, door panels, bumpers, engine covers, as well as interior and exterior cladding components.
Another solution is extrusion which involves forcing of plastic heated to a plastic state through a die to achieve the desired shape. Extrusion is typically used to produce long, homogeneous parts such as sections, pipes, gaskets and mouldings. The plastic injection moulding technologies also include rotational, hot and pressurised moulding. The former involves placing plastic powder or granules in a mould, which is then simultaneously rotated in two axes and heated. The melting plastic is evenly distributed over the inner walls of the mould to form a thin-walled part. This is for example how fuel tanks and all kinds of covers are made. In thermoforming, on the other hand, a sheet of plastic is heated to a plastic state and then given the desired shape using a mould and negative or positive pressure. Hot injection moulding makes it possible to produce larger parts from thin material, such as boot components. In pressure moulding, on the other hand, the plastic is placed in a mould and subjected to high pressure, allowing the shape of the mould to be accurately copied. This process is often used in conjunction with injection moulding and allows more complex products, such as structural components and housings, to be made.
Benefits of plastics in the automotive industry
There are many benefits to using plastics in the automotive industry. Injection-moulded automotive components contribute to the effectiveness, safety and sustainability of vehicles. They are significantly lighter than traditional materials such as steel or glass, and vehicles with lower kerb weight use less fuel, resulting in lower CO2 emissions and improved fuel efficiency.
Furthermore, plastics offer greater freedom in the design of complex shapes and structures so that more aerodynamic and aesthetically pleasing vehicles can be produced. At the same time, they are resistant to corrosion which increases the durability and lifespan of components manufactured, even when used in harsh weather conditions. On the other hand, due to their high mechanical strength, plastics are widely used in safety components such as airbags, energy-absorbing shock absorbers in bumpers or protective covers, thus effectively protecting passengers during an accident. This type of material also has excellent insulating properties, which contributes to acoustic and thermal comfort inside the vehicle. At the same time, they are environmentally friendly, as most of them can be recycled to reduce waste. Note also that the processing of plastics by injection moulding often requires less energy compared to traditional materials. This also has the effect of making their processing more economically efficient, which is beneficial, especially in high-volume production.
Examples of plastic applications in the automotive industry
Modern vehicles contain a significant amount of plastic. It is estimated that, on average, plastics account for around 10-15% of the weight of a modern car. In some cases, particularly in more advanced vehicles, this can be as much as 25%. The most commonly used plastics include polypropylene (PP) and ABS. These ensure an aesthetically pleasing look and durability of cockpit parts, side panels or door handles. Seats typically use polyurethane (PU) and polypropylene foams (ex. EPP). The latter of the materials makes it possible to produce attractive sun visors or comfortable and permanently elastic seats that retain their original shape for a long time. However, airbags used in the safety system are manufactured from nylon (PA). Plastics can also increasingly be found on the outside of vehicles, for example in radiator grilles or bumpers. These structures are most often manufactured by injection moulding of polypropylene (PP) or polycarbonate (PC). However, inside the bumpers, the EPP car components, so called absorbers, are used to absorb impact energy, thus minimising damage in case of an accident.
Plastics are also used to manufacture engine covers to protect the engine from dirt and damage. Polypropylene (PP) works best for this purpose. The mechanical strength of this type of material means that it is increasingly being used in the manufacture of body parts. The range of applications for plastics also includes such items as all kinds of PVC gaskets and cable sheathing or boot components in the form of various mats, compartments or toolboxes.
Challenges and the future of plastic injection moulding in the automotive industry
Plastic injection moulding technology will continue to evolve to address the challenges of sustainability. Its future looks promising, especially with the growing demand for electric and hybrid vehicles and the development of new materials and technologies. Although plastics reduce the kerb weight of vehicles and increase their energy efficiency, urgent measures are needed in the field of efficient processing and recycling technologies to reduce the use of energy and fossil raw materials.
One of the solutions for the future is proper recycling and closed-loop economy. Implementing more efficient methods of recovering plastics will reduce oil extraction and cut down the amount of waste deposited in the environment that is difficult to decompose. Increasingly stringent environmental regulations oblige manufacturers to manage plastics responsibly. Undoubtedly, the future of plastics will continue to be shaped by innovation. The industry is constantly looking for new types of plastics with even better technical properties and sustainability. Development of lightweight carbon or glass fibre reinforced composites or bio-based materials is certainly to be expected in the days to come. Modern automated and robotic production lines managed by artificial intelligence will assist in their efficient manufacturing.