The Plastic Conundrum: Modern Cars' Design Choice Explained

Plastic has become an integral part of modern car manufacturing, with plastic and polymer parts now making up more than 50% of a car's body and components. This shift from metal to plastic has been driven by several factors, including cost, weight, safety, and design. Plastic is more affordable than metal, and its lightweight nature improves fuel efficiency. Additionally, plastic absorbs impact better than metal, enhancing safety, and its flexibility allows for more complex designs. However, some critics argue that the use of plastic in cars contributes to planned obsolescence, as plastic parts may need to be replaced more frequently than metal ones.

Plastic is lightweight, durable, and cheaper to produce than metal

Plastic is a lightweight, durable, and cheaper alternative to metal, making it an attractive option for car manufacturers. Its lightweight property helps increase fuel mileage and is thus used in exterior car parts like doors, fenders, bonnets, and bumpers. Plastic is also used as a foam filler in hollow structures, adding structural strength and keeping passengers safe in accidents, especially during rollover crashes.

The use of plastic in cars has revolutionized the automotive industry, providing a flexible and affordable material that can be moulded into nearly any shape. Injection moulding allows for the creation of strong and thick parts where needed, while also enabling thin and light components where less strength is required. This versatility is advantageous for manufacturing complex car parts.

Additionally, plastic is a safer option for car occupants in certain areas. Unlike metal, plastic does not conduct noise and vibrations, making it preferable for ventilation channels and interior panels. Plastic is also more suitable for areas that come into direct contact with occupants, such as the dashboard, centre console, and backside of the front seats. Metal would require additional padding in these areas, increasing labour and material costs.

The durability of plastic further contributes to its popularity in car manufacturing. Certain plastics are highly resistant to fire, weather conditions, and chemicals, prolonging the life of the vehicle. For example, polyethylene, a strong plastic used in car manufacturing, can withstand heavy impacts, maintain integrity under stress, and resist moisture and chemicals.

While some may argue that plastic parts in cars are more prone to breaking, it is important to note that many plastic components are designed to last the lifetime of the vehicle. In some cases, plastic parts can even outperform their metal counterparts in terms of strength and impact resistance, providing additional safety in the event of a collision.

Plastic is safer in crash tests and increases fuel mileage

Plastic is a lightweight, durable, and flexible material that has revolutionised automotive manufacturing. It is the second most common building material in motor vehicles, with more than 50% of a modern car's body and parts being made of plastic.

Plastic is a safer choice of material in crash tests. Plastic parts have a higher energy absorption capability, nearly four to five times that of metal. This additional absorption provides better protection for passengers in the event of a collision. Plastic also has the ability to crumple on impact, which is not as easily achievable with metal parts. Furthermore, plastic can be used as a foam filler in hollow structures, adding greater structural strength to the vehicle and improving safety in a variety of accidents, especially during rollover crashes.

The lightweight nature of plastic helps to increase fuel mileage. Plastic parts are much lighter than their sheet metal equivalents, and as a result, a car with plastic parts is more fuel-efficient. Plastic's low weight means the engine has less overall weight to propel, improving performance.

The use of plastic in cars has allowed for new designs that were not possible with metal. Injection moulding techniques allow plastic parts to be thick and strong where needed, and thin and light where less strength is necessary. This versatility in manufacturing, along with plastic's low cost, has allowed for the production of vehicles at lower costs, with more streamlined production.

Plastic is flexible and can be used to create complex shapes

Plastic is a flexible material that can be moulded into complex shapes, making it ideal for car manufacturing. Injection moulding, for example, allows for the creation of parts that are thick and strong in some areas, and thin and light in others. This technique is far more complex and expensive when using metal. Plastic parts can be designed to be durable, fire-resistant, and weatherproof, depending on the design goals.

The flexibility of plastic also allows for the creation of lightweight parts, which can help improve fuel efficiency. Polypropylene, for instance, is a thermoplastic polymer commonly used in the automotive industry. It can be easily formed into almost any shape, making it a versatile material for manufacturing. Plastic parts are also generally safer in crash tests, as they have a higher energy absorption capability than metal. This means that in the event of a collision, plastic parts can crumple and absorb the impact, providing additional safety for passengers.

Additionally, plastic can be used to create complex shapes that would be difficult or impossible to achieve with metal. This allows for innovative designs that were not possible with traditional materials. For example, plastic bumpers can be made with high-impact resistance using materials like polypropylene, polycarbonate, or TPO. Plastic is also used in tyres and suspension systems, often made from polyurethane due to its durability and suitability for outdoor use.

While some people may associate plastic with lower quality or breakage, it is important to note that plastic parts can be designed to last for the life of the vehicle. The choice between plastic and metal depends on the specific application and design goals, as each material has its own advantages and disadvantages.

Plastic is highly resistant to fire, weather, and chemicals

The use of fire-resistant plastics in car manufacturing improves the overall safety and usability of motor vehicles. For example, certain plastics with high impact strength, such as polycarbonate, are often used in high-stress applications like car bumpers. Additionally, plastics tend to have a higher energy absorption capability than metal, providing additional safety for passengers in the event of a car accident.

Plastics are also weather-resistant, which prolongs the life of a vehicle and allows it to be operated safely in varying circumstances. For example, polyethylene, a strong plastic used in car manufacturing, is highly resistant to moisture and can maintain its integrity under stress. This resistance to weather conditions helps to reduce maintenance costs for vehicle owners.

Furthermore, some plastics are highly resistant to chemicals, which is especially important for certain automotive applications. For instance, polypropylene is used in fuel systems due to its high resistance to temperature and stability. This chemical resistance ensures the safety and efficiency of the vehicle's fuel system.

Plastic is used in exterior parts like doors, fenders, bonnets, and bumpers

Plastic is now used in exterior parts like doors, fenders, bonnets, and bumpers. Polypropylene, the plastic used in plastic bottles, is the most common plastic used in the automotive industry. It is a thermoplastic polymer, which means it can be easily moulded into almost any shape, helping to create more versatility during the manufacturing process. Polypropylene is also used in bumpers, along with polycarbonate and TPO, as these plastics have high impact resistance. Polyurethane is often used for tyres and suspension due to its suitability for outdoor use. Polyoxymethylene is used for door handles and headlights as it has high rigidity, making it suitable for both interior and exterior components.

The use of plastic in these exterior parts has several benefits. Firstly, it improves safety. Plastic has a higher energy absorption capability than metal, nearly four to five times more, which provides additional safety for passengers in the event of a collision. Plastic is also used as a foam filler in hollow structures, adding greater structural strength to the vehicle and keeping passengers safe in a variety of accidents, especially during rollover crashes. Plastic parts are also lightweight, which helps to increase fuel mileage.

The use of plastic in exterior parts also improves the efficiency of manufacturing. Injection moulding with plastic allows for parts that are thick and strong where needed, and thin and light where less strength is necessary. This process is much simpler and more cost-effective than metal casting. The use of plastic also allows for new designs that were not possible with metal, giving designers more freedom. Additionally, the low cost of plastic helps to streamline production and keep vehicle prices competitive.

While plastic parts may seem weaker and more prone to breaking, they can often perform better than metal parts. Metal parts do not crush as easily and can be more difficult to replace. Plastic parts are designed to crumple on impact, which is safer for occupants. Plastic parts are also less susceptible to issues like thermal cycles and can last for the life of the vehicle.

Frequently asked questions