Carbon fiber is a carbon content of more than 90% of the high strength, light weight, corrosion resistance, has a good energy-absorbing effect of the material, can replace a lot of traditional materials, for automotive lightweight has the significance of the times. However, the high price of car companies and consumers deterred, in recent years, the cost has been slightly reduced to civilian use, the current price of 200 ~ 250 yuan per kg, still far more than traditional materials, making many automotive companies in the use of carbon fiber stretched.

Carbon fiber use in the automotive industry status quo

In other industries, including automotive, the demand for carbon fiber has grown very rapidly in recent years, is expected to grow in 2020 to 140,000 tons per year. Carbon fiber in the motor vehicle industry service life of 15 years, in the aviation field is 20 to 25 years, and the current aircraft fuselage carbon fiber accounted for 40%, so in the next 10 to 20 years, the market will have a large number of carbon fiber materials need to go to the recycling, China in April 2017 introduced the "recycling development to lead the action" in October launched the "industry key common technology development guide", which all Mentioned the recycling of carbon fiber composite materials.

Today, in addition to the BMW I3 carbon fiber composite materials accounted for 50%, most fuel cars are still using steel or alloy body, new energy vehicles before the use of all-aluminum body and carbon fiber body, with the enhancement of power, in order to cut costs also began to use steel and alloys, for example, the Tesla Model S using all-aluminum body, now the new Model 3 replaced with a steel, aluminum hybrid body, BMW I3 will be replaced with steel, aluminum, carbon hybrid body, domestic new energy vehicles are more small cars, mostly using low-cost all-aluminum alloy frame, the overall automotive industry carbon fiber use rate is low, it is difficult to achieve the ultimate lightweight, carbon fiber recycling is imperative.

High efficiency recycling still faces technical difficulties

First of all, thermosetting polymers can not be directly heated to reshape, and recycled materials are often mixed with pollutants, such as metal and plastic debris, if you want to make the current recycling technology out of the laboratory, industrial production, it is necessary to solve the cost of the problem, in the 2018 Automotive Materials (Xicheng) International Forum from the University of Nottingham, Prof. Meng Fanran brought their experimental results.

The current carbon fiber recycling process is mainly divided into three, mechanical, chemical and pyrolysis methods, mechanical recovery methods are not applicable to automotive carbon fiber composite materials recovery, and chemical recovery is still limited to the laboratory stage, there is still a large gap from the industrial production, so pyrolysis is currently the only industrial production of carbon fiber composite materials recycling technology.

The current carbon fiber recycling process is mainly divided into three kinds of mechanical, chemical and pyrolysis methods, mechanical recycling methods are not applicable to the recovery of carbon fiber composites for automotive use, and chemical recycling is still confined to the laboratory stage, there is still a large gap from industrial production, so pyrolysis is the only carbon fiber composite material recycling technology to achieve industrial production at present.

The experiments used is the pyrolysis method in the fluidized bed recovery process, first of all, the waste material loaded into the fluidized bed, the fluidized bed after more than 500 degrees of high temperature, the recycled polymer through the oxidation of the removal of the remaining is the carbon fiber. Carbon fiber and then through the recycling process to be collected, the rest of the exhaust gas can be recycled, the whole process can be recycled waste in the carbon fiber, effective separation of pollutants and carbon fiber, including impurities. And the use of exhaust gas recycling to reduce the energy consumption of the entire process, realizing the energy flow back, has a good market prospect.

However, the recycled carbon fiber and traditional materials are not the same, can not be used directly for the manufacture of final products, to use the recycled carbon fiber to go to the intermediate processing, including fiber distribution, suspension, thermal drying and other processes, and finally need to get the carbon fiber alignment, the use of rotation, rotating hoop can be corrected and unified direction of the fiber, and finally get the adjusted and aligned carbon fiber material, used to generate high strength carbon fiber composites.

From the decomposition of the recycled material to the later production of the composite and the production of motor vehicle parts, many variables affect the cost of recycling, including the speed of conveying the waste material and the quality of the waste material, the energy consumption is significantly reduced when the material is fed faster.

At the same time, if we look at the whole life cycle, the fuel economy of the whole vehicle produced by recycled carbon fiber ranges from 20% to 60%, the recycled composite can reduce greenhouse gas emissions, and after alignment can bring higher strength, the performance of recycled carbon fiber compared to traditional materials, there are still obvious advantages.