Recycling and Reuse to Trigger Robust Growth of FRSP Industry
Year:2019 ISSUE:16
COLUMN:POLYMERS
Click:167    DateTime:Aug.23,2019


By Zhang Rongqi, Zhang Jun, Fiber Composite Material Recycling Branch of China National Resources Recycling Association


Brief profile of recycling industry 

There are more than 10 000 registered fiber reinforced thermoset plastic (FRSP) composite companies in China. According to the data from National Bureau of Statistics, the number of FRSP available in service exceeded 34 million tons in 2018 in the 442 big-sized producers surveyed nationally. 

   The production processes of FRSP consist of molding, pultrusion and winding. The yield rate of scraps (including rejects) in the manufacturing process is around 6%, and based on it, Chinese FRSP scrap availability is calculated at 3 million tons or so and is growing at a rate of 10% year on year. The service life of FRSP is generally estimated at 20-30 years, and according to it, more than 2 million tons of FRSP have expired the service so far. 

   Chinese FRSP market entered a boom era from the middle of 1990s. FRSP became widely applied, and natural aging and fragile life of some grades (such as outdoor or carrier grades) were usually affected by the application environment. The recycling technologies have been developing slowly, so most solid FRSP wastes were left with little choice but being buried. 


Solid FRSP wastes

   1. Carbon fiber reinforced composites

   The recycling technologies of carbon fiber and its products are developing slowly for the following reasons: the output of carbon fiber composites is quite small, at less than 50 000 t/a, according to statistics, and subsequently, the amount of scraps and wastes from carbon fiber products manufacturers is limited; carbon fiber products manufacturers are widely located across the country, making it more difficult to recycle the scraps and wastes together. Pyrolysis recovery is the key technology for the recycling of carbon fiber, and whether the equipment could be put into commercial use is yet to be verified. 

   2. Recycling of wind power blades

   The recycling of wind power blades is extremely urgent. No matter the blade manufacturers, engineer factories or proprietors have paid much attention to it and are actively engaged in treatment and recycling of the blades. However, there are few successful cases for application and industrialization of recycled blades in pipe, purlin, landscape, and architecture sectors for the reasons below: 

   1) Not a big amount of waste blades is available in the market, so the application scale is not potentially big;

   2) A lack of recovery decomposition technology and research on the reuse of recycled materials, a lack of application and exploration of recycled material;

   3) Many companies disassemble the blades on the spot and transport the parts to other regions, and then pile them up;

   4) Companies generating wastes ignore the recycling technology and environmental-protection requirements in the process of recycling and treatment;

   5) No standards and regulations for the recycling;

   6) A lack of reasonable business mode and supervision system for the recycling;

   7) A lack of the government’s supportive policies.

   The blade recycling market has not been standardized and upscaled, so the recycling and the reuse could not be industrialized and high-valued. 

   3. Reuse of fiberglass wastes and fiberglass product scraps

   There are over 300 000 tons of fiberglass wastes and fiberglass product scraps in China every year. Companies put fiberglass wastes back into kilns, grind them, and make them into ceramic glaze, heat-insulating material and chopped strand mat. However, the economic gains are quite low. There is another highly-concerned way for the treatment of fiberglass wastes and scraps. The fiberglass wastes and scraps are processed into powder with various specifications, and then are applied in rubber, plastics, electronics, paint and ink sectors. 


Recycling technologies

   1. Energy acquisition method - incineration

   Energy, obtained by the incineration of polymer resin in composites, can be used to generate power and provide heat. In spite of high heat value of the polymer resin, the content of the resin in composites is scant, so the total heat value is limited. Besides, since the content of fiberglass in composites is high, there are hidden dangers from the incineration of composites which usually gives rise to a big amount of glassy-state substance easily sticking to furnace body or grate. 

   2. Cement kiln collaborative disposal hazardous waste process

   Cement kiln collaborative disposal hazardous waste process is relatively mature in the UK and German, while it has not been accompanied with mature experimental data and application experience in China. Some domestic producers have started engaged in the research of the process and it is believed to be more applied in the near future. 

   3. Chemical dissolution process (directional depolymerization)

   Polymer is opened at specific key positions with help of solvents and at certain temperature and pressure, to form long-chain monomer or raw material of resin. This is truly a good approach to materialize circular economy. Many universities and colleges in China have conducted researches based on polymer materials (led by plastics and rubber) such as the researches of degradation of thermoset composition base resin, although the process has not widely been put into use. Purification of the byproduct based on chemical dissolution process is yet to be worked on. Given big investments on equipment, the key to the utilization of chemical dissolution process is high efficiency of the equipment.

   4. Biological degradation

   Today, only two kinds of fiber reinforced polymer materials - polylactic acid, degradable epoxy material can adopt the process. Why the process cannot be put into wide use yet? The reason is that the properties of degradable materials vary and the cost is high. But the research on the process is going on. 

   5. Pyrolysis

   Organic-content polymer chain of resin is opened, and then fiber and filler are separated and recycled through pyrolysis. Big-sized products can be pyrolyzated without dissembling, which is very efficient to recycle and reuse carbon fiber products. At present, Shanghai Jiaotong University-Shanghai Yeshi Alloy Science & Technology Co., Ltd. is in trial run of production based on the process.

   The pyrolysis technology has improved much, with the pyrolysis energy evolved from power, natural gas, coal and microwave to pyrolysis gas and pyrolysis oil stemmed from composites pyrolysis. The evolving of the energy highlights a reduction in processing costs and natural energy consumption. 

   6. Reuse

   Composite products, after the expiration of service or discarded, can be reused if some properties of the products remain workable and they can be directly moved or be processed to be moved. Taking blades as an example, the root cylinders of waste and scrap blades are cut off and then applied in pipeline, water storage ponds and septic tanks in water-deficient plateau areas; the blade web can be processed and used as wallboard and insulation board for architecture. The application of waste and scrap blades is a successful case of high-valued reuse.

   7. Mechanical comminution and addition

   This process boasts with lowest operating costs and the easiest access to industrialized production. Glassfiber conventionally reacts with alkali-aggregate of cement, so it is not welcomed in the architecture sector. But the problem has been solved, as chopped strand glassfiber is recycled and used in crack-resistant mortar. The architecture market has great potential, so the application of waste and scrap glassfiber in the sector will be a good way for the process. 

   There are two critical points in FRSP recycling technologies - the recycling and reuse of reinforced resin as well as scrap and waste glassfiber. At present, FRSP, no matter via physical or chemical process routes, can be reused after grinded, decomposed or directional depolymerized. 

   From the perspective of the development and commercial use of FRSP recycling technologies, application of the recycling technologies should be promoted step by step based on current development status quo. The key to the promotion of FRSP recycling technologies is how to reuse the recycled glassfiber.