In today's automobiles, the widespread use of plastics instead of expensive metal materials in automobiles has become an inevitable trend. High-strength engineering plastics not only reduce parts processing, assembly and maintenance costs, but also make cars more lightweight, energy saving and environmental protection. The data shows that plastic and its composite materials are the most important automotive lightweight materials. It not only can reduce the quality of parts and components by about 40%, but also can reduce procurement costs by about 40%. Therefore, the amount of use in automobiles has rapidly increased in recent years. .
Engineering Plastics Opportunities and Challenges
In the 1990s, the average amount of plastic used in the developed countries was 100kg/vehicle-130kg/vehicle, which accounted for 7%-10% of the vehicle's overall quality; by 2011, the average amount of plastic used in the developed countries reached 300kg/vehicle. It accounts for 20% of the vehicle's overall quality; it is estimated that by 2020, the average amount of plastic used in developed countries will reach 500kg/vehicle.
At present, the most common types of plastic used in automotive plastics are polypropylene (PP), ABS resin, polyvinyl chloride (PVC), and polyethylene (PE). Polyolefin materials constitute the main plastic parts of automobiles, and this trend will become more and more apparent in the future. Below, the author will list several mainstream automotive engineering plastic solutions and interpret their characteristics.
Polypropylene (PP)
PP can be used as a variety of automotive parts. Nowadays, in the typical passenger car, PP plastic parts account for more than 60. The main types of PP auto parts include: bumpers, dashboards, door trim panels, air conditioner parts, battery casings, cooling fans, and steering wheels, of which the first five types account for more than half of the total vehicle PP usage.
Polyethylene (PE)
Through the graft modification and filling toughening modification of high density PE and low density PE resin, a series of modified PE alloy materials with good flexibility, weather resistance and coating performance were obtained. PE mainly uses blow molding methods to produce fuel tanks, vent pipes, deflectors and various types of storage tanks.
In recent years, there has been no increase in the use of PE in automobiles, and it is worth noting that the development trend of lightweight vehicles has promoted the plasticization of fuel tanks. European cars formally use plastic fuel tanks. Their main material is high-molecular-weight high-density polyethylene (HMWHDPE).
ABS resin
ABS resin is a terpolymer of three monomers: acrylonitrile, butadiene and styrene. It can be used to make external or internal parts of automobiles such as instrument housings, cooling and heating systems, tool boxes, handrails, and radiator grilles. Boards, etc.; it can also be used to make dashboard skins, trunks, glove box covers, etc.
In recent years, the increase in the use of ABS resin in automobiles has not been significant. This is mainly due to the fierce competition between ABS resin and PP resin, and ABS itself also has drawbacks of poor weatherability, discoloration, flammability, etc. Therefore, it is in the car. Applications for major components such as automotive dashboards and grilles are also limited.
Polyamide (PA)
Polyamide is commonly known as nylon and has high impact strength, abrasion resistance, heat resistance, chemical resistance, lubricity, and dyeability. As an automotive structural part, the amount of PA is constantly increasing and can be applied in harsh environments around the engine.
Polyoxymethylene (POM)
Excellent wear resistance characteristics, long-term sliding characteristics, molding fluidity, surface appearance and gloss characteristics are also suitable for insert molding. Automotive chassis bushings, such as steering knuckle bushings, various bracket bushings, front and rear leaf spring bushings, and brake bushings, are widely used in polyoxymethylene-type three-layer composites. They are based on cold-rolled steel plates and sintered porous bronzes. The powder is a three-layer composite material with an intermediate layer and a surface modified with polyoxymethylene as a friction-reducing layer. Rolled out of a certain regularity of the oil storage pit, its structure determines its special properties: it not only has the mechanical strength and rigidity of steel, but also has excellent antifriction and anti-wear properties under boundary lubrication conditions. Other applications include door handles, safety belt mechanics, combination switches and mirrors. Engineering plastics are further improved.
Among the above-mentioned materials, nylon materials used for automobile structural parts have the most demanding operating environments. In the face of increasingly stringent automotive-grade standards, engineers have continuously improved engineering plastics, and conventional nylon glass fiber reinforced materials are no longer satisfactory. Updated requirements. A more advanced solution has also emerged for polyoxymethylene materials.
Hostaform®XGC
As a global manufacturer of engineering plastics, Celanese's Hostaform® XGC series materials have superior chemical resistance, long-term stability in high-temperature environments, high wear resistance, dimensional stability, excellent thermal stability and process stability Sex, widely used in automotive structural parts.
XGC series materials can maintain the balance between strength, stiffness and toughness even at ambient temperatures of minus 30°C and minus 40°C. It also uses Celanese's proprietary blended backbone modification technology. In conventional glass fiber reinforced materials, the resin and glass fiber are only physically mixed in the molten state. While the XGC material is in the molten state and a similar coupling chemical reaction is performed internally, a part of the POM molecule chain will be connected to the glass fiber, so it is not a pure physical reaction. Such materials are at least 50% higher in impact resistance than conventional materials.
Hostaform® XGC expands the application of glass-reinforced Hostaform® acetal copolymers and complements the existing glass fiber reinforced product portfolio. The performance of the XGC series is comparable to that of non-similar substrates such as PBT and PA glass-reinforced products. The following figure shows the mechanical performance comparisons. The following are the potential application advantages:
Higher strength meets future specifications and/or reduces component weight while still meeting application functional requirements.
Better toughness? Suitable for applications where parts may be subjected to high impact during use (typical examples include wiper arms, conveyor systems, and snowboard fixtures).
Excellent fatigue resistance? The transmission gears of the window and door systems are typical applications where the components are subjected to severe cyclic stress during operation.
Higher Tensile Strength and Rigidity For new parts, there is an opportunity to reduce stiffeners and reduce wall thickness, and/or use lower glass content than non-similar resins. This can be lightweight and/or ensure a higher safety factor in existing part designs.
Freedom from the influence of humidity? Provides dimensional stability over a wide operating temperature range, which is critical for applications requiring high accuracy, such as gear systems in doors, windows, and wiper systems. Celanese's Hostaform® fiberglass-reinforced products combine these advantages with all other highly-regarded performance advantages, enabling design engineers to view material selection from a new level.
In terms of impact resistance, the Hostaform® XGC series is also greatly improved on the basis of the original typical glass fiber reinforced products (as shown in the figure below). It can be seen that XGC's impact resistance has been significantly improved, exceeding the standard glass fiber reinforced type. (C9021GV1/30) grade.
Hostaform®PTX
Automakers are under pressure to reduce weight, lower costs, and increase fuel efficiency. The use of high-performance engineering materials can help manufacturers maintain profitability at a time when costs and competitive pressures are increasing.
The Celanese Hostaform® PTX series sets benchmarks for cold impact resistance, weld strength and fuel resistance. These new POM grades have low moisture absorption, excellent mechanical properties and friction properties as well as high levels of chemical resistance and fuel resistance. Hostaform® PTX can be extruded into flat tubes and bellows for use in fuel, pneumatic brake systems, clutches, fresh air vents, and liner applications.
It is understood that the difference between Hostaform® PTX and conventional POM is that the former is very soft and the latter is very rigid. As a result, PTX series materials are more often used in automotive pipelines. The typical application is the tubing in automotive fuel tanks.
Early automobile fuel tank hoses were made of materials such as nylon 11 and nylon 22. Their disadvantage was that they were prone to low-molecular-weight nylon molecules that were precipitated by long-term exposure to fuel soaking. As the oil temperature became lower, these substances precipitated. Over time, it will block the oil and fuel injectors. The PTX material does not exhibit low molecular weight polyoxymethylene precipitates and is an ideal material for fuel tank hoses.
There are tens of thousands of parts in the car, and the different parts have different requirements for the characteristics of the materials. With the advancement of automobile design and the change of the concept of consumers, there is an increasing demand for automotive materials. Regardless of the legal level or the level of consumer demand, engineering plastics have become the inevitable trend of new automotive materials because of their environmental protection, light weight, energy saving, and diversification.