At present, the application of polymer materials can be seen everywhere in automobile load-bearing parts, new energy vehicle battery packs, and other automobile parts. The application of polymer materials in automotive parts and the need to improve automotive safety have promoted the development of flame-retardant polymer materials. The flame-retardant polymer materials currently used are mainly PP, PU, ABS, and PC. According to the special needs of automobile parts, composite materials (alloyed), PA, PBT, and PMMA are also used.
1. Flame retardant PP
PP is the most commonly used polymer material among automotive plastics. It has excellent chemical corrosion resistance, simple processing, and low cost. Currently, it is widely used in automobile dashboards, battery pack casings, door guards, pillars, seat guards, bumpers, etc. However, due to the poor flame retardant properties of PP without added flame retardants, its LOI is only 17.8%, which makes it very easy to burn.
Domestic and foreign research on automotive flame retardant PP mainly focuses on modifying the polypropylene matrix and developing polypropylene composite materials with excellent mechanical properties and flame retardant efficacy by adding low-toxicity, halogen-free flame retardants to meet the needs of automotive zero- Flame retardant requirements of components.
At present, flame retardants suitable for PP are mainly additive flame retardants, and halogen-based flame retardants (such as bromine-based flame retardants, bromine-antimony synergistic flame retardant systems) and inorganic-filled flame retardants are widely used. Agents (such as magnesium hydroxide, and aluminum hydroxide), phosphorus-nitrogen series (such as MPP, APP, MCA, phosphazene, phosphate ester, etc.), and intumescent flame retardants (IFR).
As we said above, with the implementation of strict environmental protection policies, halogen-free flame retardants for polymer materials have become a general trend. Judging from specific cases, LGF-reinforced halogen-free flame-retardant polypropylene has been prepared using PP as the matrix, long glass fiber (LGF) as the filling material, and adding phosphorus-nitrogen-based halogen-free intumescent flame retardant, MCA, etc. Example of battery bay.
During the preparation process, a double masterbatch preparation method is adopted, by separately preparing LGF masterbatch and halogen-free flame retardant masterbatch, mixing the two evenly, and directly injection molding to produce flame retardant PP products. The double masterbatch preparation method avoids the degradation of flame retardants caused by excessive shearing zone temperature during the manufacturing process of long glass fiber masterbatch and the degradation of mechanical properties caused by short glass fiber length.
Among the halogen-free modification technologies of flame-retardant PP, IFR is considered to be the most advanced among halogen-free flame-retardant PP due to its minimal impact on PP processing fluidity and low density, excellent flame retardant efficiency, low dosage, low smoke, and non-toxicity, etc. One of the best prospects for development.
Flame-retardant PP started late in my country, but it is developing rapidly. In particular, the rapid growth of the new energy automobile industry in recent years has directly promoted the rapid growth of the demand for flame-retardant PP. Many domestic universities, scientific research institutions, and enterprises have participated in the development of flame-retardant PP for automotive parts. In the future, research on automotive flame-retardant PP will focus on high efficiency and environmental protection. By selecting halogen-free flame retardants, intumescent flame retardants, phosphorus-nitrogen flame retardants, and compound flame retardants combined with other additives, Developed flame-retardant PP materials with excellent performance.
2. Flame retardant ABS
Before the rise of ABS in the automotive industry, it was also one of the most widely used polymer materials for home appliances in the world. According to incomplete statistics, about 80% of my country's ABS consumption comes from the field of home appliances, which is mainly due to the outstanding surface coating performance, durability, and anti-corrosion properties of ABS. It is also these characteristics that make ABS a typical example in the field of automotive painting. However, ABS resin has only three elements: C, H, and O in its molecular structure, so it does not have flame retardant properties. It has poor stability at high temperatures and is extremely easy to burn. At the same time, a pungent odor and black smoke will be produced during the combustion process, and it cannot be directly used in automobile parts.
At present, the main application direction of ABS is through flame retardant or high-temperature resistance modification, or it is blended with PC to form PC/ABS composite materials, which will be introduced in detail below. For ABS, the flame retardant efficiency of halogen-based flame retardants is relatively high, and the flame-retardant effect of bromine-based flame retardants is better than that of chlorine-based flame retardants. Although halogen flame retardants are low-cost and effective, practitioners know that halogen flame retardants will face tremendous pressure from policies and environmental regulations in the future. Therefore, the flame retardant modification of ABS is still an important research and development direction. But having said that, for application scenarios with strict flame retardant standards, brominated flame retardants are currently the most mainstream choice. It is reported that about 70% of ABS used in electronic and electrical products uses brominated flame retardants.
PC/ABS has the advantages of both, with better heat resistance and stability, and better processing performance. It is currently the plastic alloy with the largest output and the most mature technology and is also the most widely used material in the field of automotive parts. one. PC/ABS materials are used in parts such as car dashboards, battery packs, bodywork, and interiors. However, it should be noted that there is still a "1+1<2" situation in some indicators: PC itself is a self-extinguishing material, UL94 can reach V2 level, but the flame retardant performance of PC/ABS has declined. Need to make up.
In addition to the halogen and phosphorus systems currently commonly used, the development direction worthy of attention is nano-flame retardants, such as nano-scale antimony trioxide, aluminum hydroxide, magnesium hydroxide, and nano-layered double hydroxide.
3. Flame retardant PC
As one of the five major engineering plastics, PC is also quite mature in its application in automotive parts, such as automotive dashboards, lighting systems, heating plates, defrosters, and even some bumpers made of PC alloys.
As we just said, PC itself has certain flame retardancy and has certain advantages compared to other polymer materials (such as PE, PP, etc.), and the LOI can reach 21-24%. However, in application fields with relatively high flame retardant requirements for automotive parts, its flame retardant performance is still insufficient, and flame retardant modifications are still needed. Brominated flame retardants can significantly improve the flame retardant properties of PC. Commonly used ones include decabromodiphenyl ether (DBDPO), tetrabromobisphenol A (TBB-PA), etc. However, bromine-containing flame retardant materials easily decompose at high temperatures to produce corrosive gases, which can damage auto parts. In addition, the addition of brominated flame retardants will seriously affect the transparency of PC, and it also does not meet the requirements of the EU's halogen-free and environmentally friendly policies. Currently, the most commonly used phosphorus flame retardants in industrial PC products are TPP, RDP, and BDP.
Among them, TPP is solid at room temperature, has poor thermal stability, is easily volatilized at PC processing temperatures, and only plays a gas-phase flame retardant role. RDP and BDP are liquids at room temperature, have good thermal stability, and can exert both gas phase and solid phase flame retardant effects. At the same time, BDP has good compatibility with PC and can play a role in accelerating hardening, so PC The +BDP system has become a more commonly used system, and the BDP addition ratio is approximately 10%.
In addition, silicon-containing compounds, as a new generation of environmentally friendly flame retardants, have gradually attracted attention due to their high efficiency, low toxicity, non-polluting properties, and small impact on PC processing performance and physical properties, such as polysilane and polysiloxane. wait.
PC used in auto parts is also moving closer to halogen-free and environmentally friendly when selecting flame retardants. The comprehensive performance of PC can be improved by adding a variety of additives or preparing composite flame retardants. In addition, PC is also the best choice to improve PC processing performance and flame retardant performance by forming composite materials with ABS, PBT, etc.
4. Other flame retardant materials
PP, PU, ABS, and PC are flame-retardant polymer materials currently mainly used in the production of automotive parts. In addition, composite materials prepared by melting and blending two or more polymer materials are also commonly used materials at present, such as PC/ABS, PC/PBT, PC/FR composite materials, etc.
