Application of the hottest thermoplastic in body p

2022-10-22
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Application of thermoplastics in body panels

Yang Roger thermoplastics have been used in body panels for more than 25 years. Thermoplastic is far better than metal in corrosion resistance, weight loss and impact resistance. However, due to the significant difference in thermal expansion coefficient, it may not be able to achieve the matching accuracy expected by Automotive Engineers for panel gap tolerance

although material suppliers have made a lot of efforts in market and application development, the application penetration of thermoplastics on body panels has never achieved the paradigm shift of thermoplastics on instrument panels or front and rear bumper panels. In the application of dashboard and bumper panel, thermoplastic is far superior to metal materials in modeling and design freedom. So far, due to cost reasons, the application of thermoplastics in body panels has failed to break through the limit of small batches (less than 50000 vehicles per year)

at present, automobile manufacturers use electrophoretic coating process to obtain the corrosion protection required by the body and frame. This is a relatively high temperature process. After electrophoretic coating, the vehicle enters the painting production line and hardens the paint through the paint furnace. Traditional steel will not produce any thermal deformation problems after these processes

thermoplastic materials used in body panels are divided into three different heat-resistant categories according to the stage of body panels applied to the finishing process. Among them, high-temperature engineering thermoplastics are generally based on nylon mixtures, which are suitable for panels that need electrophoretic coating. Engineering thermoplastics are generally based on PC/PBT mixtures, and are suitable for panels that need to go through a gloss paint furnace (in exceptional cases, they can also be specially designed for low-temperature gloss paint furnaces, such as the panels used in general Saturn models). The last kind of thermoplastic is not painted in the paint furnace, and it is still connected with the car body after finishing the coating process. Automobile manufacturers try to avoid painting parts outside the production line in order to reduce paint color differences

the cost of thermoplastics increases with the increase of thermal deformation, so the materials used for electrophoretic coating are the most expensive thermoplastics in automotive applications. The cost of thermoplastics used for gloss paint furnaces has been reduced, and the lowest cost is thermoplastics used for coating outside the production line

although the price of metal raw materials is low, the overall capital cost is not low due to the need to invest a lot of money to buy a variety of steel tools needed to build body panels. Although the price of thermoplastic raw materials is high, only one injection molding tool is needed in the production of parts. Therefore, its economy depends on the ratio of the cost curve of a single part to the capital cost. Usually, this breakeven point is about 50000 vehicles per year. In the past 20 years, steel manufacturers have improved corrosion resistance and reduced the weight of body panels through steel thinning. The requirements for tools are also reduced from the original 6-7 tools to 4-5 tools, which reduces the capital cost and improves the competitiveness of steel panels

with automobile manufacturers, especially Asian automobile manufacturers, starting to produce low-cost cars with a price of only $2500-5000, it seems that this has brought great application potential to plastics. Tata Motors originally intended to use thermoplastic in the nano's body panels, but gave up because it was not cost-effective enough to be competitive in the industry direction

in fact, there has been an opportunity to produce more competitive thermoplastic body panels using existing technology, changing the break even point

first of all, engineering thermoplastics are too expensive for a wide range of mass applications. Pc/pbt has been used in bumper panels since the early 1980s, and TPO has successfully replaced it mainly by virtue of its cost advantage. The same pattern will also be reproduced on the body panel, which will reduce the cost of raw materials by 40% or more. General Saturn models with low-temperature gloss paint furnaces still have higher costs than the metals used in mass automobile production. To improve the cost competitiveness of thermoplastic solutions, we must reduce the cost of raw materials

second, applicable technologies have been developed for the "coating" technology of ordinary vehicles. Coating technology based on PVDF and co extrusion thermoplastic vulcanization/PP system, such as Shulman's invision technology, has provided a non painting solution that can meet the quality requirements of body panels. But Shulman lacks sufficient funds to implement this promising technology. In addition, for such low-cost cars with a price of only $2500, molding thermoplastic into color panels can bring potential quality/price advantages and new choices to consumers

although the cost of coating and coextrusion structure is very high, considering the high cost of painting production line and the considerable potential in emission reduction, it is hopeful to bring new choices to Asian automakers who are building new plants not only by comparing the cost of components. It is unrealistic for mature Western automakers to consider canceling coating production, because their funds have been invested, and they do not intend to produce cars that meet the needs of mass markets with low incomes such as Asia. Newly built factories for Asian countries can make full use of non painting solutions and reduce capital investment

third, a material grade that can be heat molded has been developed on PP, and now it has been applied in the slotting of the middle crossbeam in the bumper panel and the under door coaming of cars made in North America to facilitate the adjustment of the center of the sample. There are many kinds of rotary thermoforming machines that can achieve the productivity efficiency of a single injection molding machine, but the capital investment is relatively low. In addition, using a single-sided mold, usually aluminum (although steel may be more ideal for such applications), can also reduce the cost than injection molding (double-sided mold)

fourth, the corresponding fastening technology has been developed by laser welding accessories or using Velcro straps (which has been verified on the thermoplastic front bumper panel). This kind of fastening technology minimizes the limitations of thermoplastic molding in the inability to easily produce 3-D depth geometry, and it is also easier to assemble

fifth, the adoption of PP based technology helps to improve the recyclability of automobile 1) runner design. For front and rear bumper panels, instrument panels, sealing systems and some under hood components, when the amount of PP used in the vehicle reaches a certain critical amount of raw materials, vehicle dismantlers will be attracted to regenerate end-of-life vehicles

then, since it has such attractive advantages in economy and environment, why can't thermoplastic be fully applied in automobiles? In fact, it has been gradually applied. Daimler smart model is a good example. Pc/pbt was first used, and now it is extended to PP (injection molding is still used). As for the application of thermoplastics in individual parts, there are countless examples. However, the application of thermoplastics in automobile has not taken a leap forward. One of the main reasons why no substantive breakthrough has been made (metal plates were eventually selected for projects such as Tata Nano) is the lack of large PP suppliers to inject impetus into the development process of this application. PP manufacturers are unwilling to invest money and make commitments to provide support for OEMs. They believe that the risk of changing to new materials is too great. This change can only be realized in the Asian market driven by Asian OEMs, because the vehicles produced with this technology mainly have markets in Asia, and Western automakers lack the incentive to change their traditional processes to produce such low-cost products with possibly low quality requirements

thermoplastics can give full play to the advantage of performance in the urban environment with heavy traffic. Won't cars that are both cost competitive and bring "green" advantages become new market favorites

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