One

Future Development Direction of Materials for Automotive Industry

The future development of China's automobile industry will change from pursuing production capacity and scale to paying more attention to quality and level. Lightweight, environmental protection, comfort and safety will become the three major themes of the future development of automotive materials in China.

According to relevant statistics, the average consumption of PU for a car in China is 15-20 kg. In 2010, the consumption of PU in China's automobile industry was about 300,000 tons. The application of PU material in cars is one of the important signs to measure the quality of cars. European and American high-grade cars, PU consumption 25-30 kg.

PU materials used in automotive industry mainly include soft, rigid, semi-rigid, foamed plastics, PU elastomers (including CPU, TPU microporous elastomers), adhesives, sealants and coatings (see Table 1).

Two

PU is the key material for realizing lightweight of Automobile Materials

The application of PU foam in automotive interior decoration: in 2010, the amount of PU soft foam in domestic automotive interior parts was 152 thousand T, and the PU rigid foam content was 67 thousand T. Mainly used in automobile dashboard, cushion, backrest, headrest, door, armrest, steering wheel assembly, automobile roof, door inner panel and sealing parts. Reducing the density of PU foam is an important way to realize the lightweight of automotive interior parts. At present, the main technical approaches adopted in China are high solid content, low viscosity POP (grafted polyether) and high functionality and high activity polyether.

Application of RIM (Reaction Injection Molding), RRIM (Enhanced Reaction Injection Molding) and SRIM (Structural Reaction Injection Molding) PU Products in Automobile Lightweight: RIM, RRIM and SRIM in Europe and America.

Table 1 List of Automotive Polyurethane Products

Varieties	Auto parts	Main Performance and Application Status
High resilience cold-moulded soft foam	ushion, backrest, headrest, decorative strip	CExcellent resilience, low hysteresis loss, high compression load ratio, good handle, good air permeability, good self-extinguishing, low energy consumption in production, is more popular now.
Thermo-moulding and filling soft foam	Cushion, backrest, headrest, footpad	Inorganic filler can be added to improve product performance and reduce cost when raw material price is low. Mold with simple structure and low cost can be used.
Semi rigid foam	Instrument panel filler, door post wrapping, control box, horn seat cushion, armrest, headrest, sunshade	It has high density and compressive strength, excellent energy absorption function, shock absorption and shock resistance. It is widely used now.
Self forming foam	Armrest, steering wheel, air spoiler, headrest, door post, control box	It has a smooth, smooth, high density self crust surface, and its core is a low density and flexible foam.
Microporous elastomer	Steering wheel, filter sealing pad, sealing strip, shock pad	Compared with rubber, it has soft density, good dimensional stability, excellent wear resistance, flexural resistance and aging resistance.
Rigid foam	Door panel lining, ceiling lining, small refrigerator, imitation wood trim, silencing mat, sunshade	Light weight, high strength, good automobile stability, excellent insulation (the best organic insulation material), good aging resistance, more in use now
Casting Elastomer (CPU)	Dust proof seal, bearing sleeve, steering knuckle bushing, door gear block, leaf spring lug bushing, automobile tire	Large bearing capacity, high tear strength, wear resistance, oil resistance, hardness adjustable range
Thermoplastic elastomer	Damping cushion block, leaf spring cushion, spring coil sheath, gear transmission unit, roof and body parts	High modulus, high strength, high elongation and elasticity, excellent wear resistance, oil resistance, low temperature resistance and aging resistance. It is possible to produce all kinds of products and wastes by general plastic processing methods (injection moulding machines) and recycle them. There is an expanding trend.

Automobile industry has been widely used, mainly for bumpers, steering wheel, body panels, engine hood, trunk cover, radiator grille, mud baffle, spoiler and so on. The weight of RRIM products is only half that of steel, which is an important way to realize the lightweight of automobiles. At present, RIM and other technologies in the domestic automotive industry still lag behind those in Europe and the United States in terms of quantity and quality, and need to be further developed.

PU material is the most promising material for plasticizing automobiles. At present, the development direction of world automobiles (mainly cars and new energy vehicles) is lightweight. Lightweight is not only an important technical measure to improve fuel combustion efficiency and reduce vehicle exhaust emissions, but also an important technical measure to achieve energy saving and emission reduction. The plasticization of automobile materials, replacing steel with plastics, is an inevitable trend and an important technical way for the development of automobile lightweight. The energy consumption of automobile parts with different materials is different.

Taking parts with the same weight (450g) as an example, the energy consumption of plastic parts is 3.9-4.5 kg of gasoline, and that of aluminum or steel is 5.3-6.8 kg of gasoline. Statistics show that for every 10% reduction in vehicle weight, fuel consumption can be reduced by 6%~8%.

At present, the average plastic consumption of cars in developed countries is 120 kg/vehicle, and that of German cars is 300 kg. The average plastic consumption of cars in China ranges from 80 to 100 kg/vehicle, and that of Audi A2 is 220 kg. By 2020, the average plastic consumption of cars in developed countries will reach more than 500 kg/vehicle. BASF manufactures a full PU body sports car with a maximum speed of 270 km per hour. RRIM technology is adopted. The PU body is a carbon fiber reinforced microporous PU elastomer composite material.

Three

TPU and its composites are plasticized for automobiles

One of the important raw materials

At present, the main plastic parts used in cars are PP (polypropylene), PVC (polyvinyl chloride), PU and PA (nylon). The development direction of automotive plastic parts is to continuously introduce cost-effective and recyclable materials. Thermoplastic polyurethane elastomer (TPU) has its unique advantages. TPU has been used in various components of automobile body, including TPU plastic alloys, such as TPU and PP, PVC, PA and other plastics to form cost-effective composite materials, which can play an important role in the automobile industry. TPU rubber composites: TPU and a variety of rubber composites have important applications in the automotive industry.

(1) TPU/PP (polypropylene) plastic alloy

At present, reinforced rubber-plastic composite structural materials for TPU-PP glass fibers (including long and short fibers) are being developed at home and abroad. This material has the advantages of light weight, good cost performance and recyclability. It is expected to be widely used in automotive interior and exterior accessories, such as bumpers and their brackets, various brackets and structural frameworks, once opened. If successful, the application of TPU in automobiles will be greatly increased.

(2) TPU/PC (polycarbonate) plastic alloy

TPU/PC blend can improve the toughness, stress cracking, fracture sensitivity, solvent resistance and chemical resistance of PC, and reduce the processing temperature of PC, which enlarges its application scope in automobile industry.

(3) TPU/PVC plastic alloy

TPU/PVC alloy can significantly increase the elongation of PVC (which can replace toxic DOP plasticizer) and expand the application field of PVC. The preparation of TPU/PVC alloy by reactive blending technology has been reported recently. First, PVC was dissolved in the binary alcohol of TPU, and then isocyanate was added to in-situ polymerization to form TPU/PVC alloy. The performance of TPU/PVC alloy was better than that of the general TPU/PVC blend, which expanded the application scope in the automobile field.

(4) TPU/PA6 (nylon 6) plastic alloy

Nylon 6 is the most cost-effective and widely used engineering plastics. PA6 has the advantages of high strength, corrosion resistance, oil resistance and self-lubrication, but it has the disadvantages of low impact toughness and high moisture absorption. As a result, its application field is limited. TPU elastomer has the characteristics of high strength, high elasticity and high wear resistance, but it has the disadvantage of low temperature resistance. The development of TPU/PA6 engineering plastics combines the advantages of these two materials and overcomes their shortcomings. It will be a new type of high performance composite material. It has wide application value in automobile industry.

TPU plastic alloy and TPU rubber composite materials have the advantages of recycling and reuse. At present, there are more than 50 million used vehicles in our country, and 10 million used vehicles need to be renovated and scrapped every year. Advanced countries in Europe and the United States clearly put forward the recovery index and utilization rate of plastic parts for automotive industry, requiring that the recovery rate of automotive plastics should be more than 95% and the utilization rate should be more than 90%. China's Development and Reform Commission, the Ministry of Science and Technology and the Environmental Protection Bureau jointly formulated a technical policy on automobile parts recycling: "By 2017, China's automobile recovery rate requirements will reach 95% or more, and the utilization rate will reach 85%. TPU is a recyclable thermoplastic elastomer, but the annual consumption of TPU in China's automotive industry is only about 30,000 tons. TPU plastic alloy and other composite materials undoubtedly provide a new huge market opportunity for the application of new TPU elastomer materials in automobiles

Four.

PU Green Environmental Protection Material is Automotive Material

The inevitable trend of exhibition

(1) Development of Low VOC PU Foam Plastics

Volatile organic compounds (VOC) content in automobiles has become an important indicator of consumers'awareness of their products.

VOC volatiles in PU foam materials, PU adhesives, PU coatings, PU synthetic leather and so on are the main factors that affect the air quality inside the vehicle.

Research and control of harmful gases and volatility in PU materials and effective preventive measures are of great significance to the improvement of vehicle interior environment and the development of China's automobile industry.

VOC of PU foam plastics for automotive interior decoration mainly comes from polyether polyols (mainly POP), catalysts, homogenizers (stabilizers), volatile organic compounds in isocyanates, including aromatic compounds (toluene, styrene) and organic amine compounds.

Development of high solid, low volatile POP, organic amine reaction catalyst, low volatile foaming agent, etc. Shanghai Institute of Applied Technology is cooperating with Wuhan Xingqiao Polymer New Materials Technology Co., Ltd. to develop an in-car VOC air purifier, which has obvious effect on improving the in-car air quality.

(2) Actively Developing Green Technology for Biomass Vegetable Oil-based Polyols

Vegetable oil is a renewable resource. Using vegetable oil such as soybean oil, castor oil and palm oil as raw materials, corresponding vegetable oil polyols can be developed to replace polyether polyols in petrochemical routes. The biobased PU foam is better than the petroleum based PU foam in terms of recycling efficiency, organic matter volatilization and CO2 emission. The US focused on the development of soybean oil based vegetable oil polyols. Ford motor has successfully developed soybean oil based PU foam for vehicle seat and seat backrest. Malaysia has developed a series of palm oil polyols using local resources, which are widely used in PU foam industry. Toyota Motor Company of Japan has successfully developed castor oil-based PU foam cushion.

(3) Actively develop green tire technology for PU automobiles

At present, rubber tires are mostly used in automobile tires all over the world. When this kind of automobile tire runs in the city, a large number of harmful substance particles are emitted into the air due to friction with the ground, which is an important pollution source causing poor air quality in the city. PU tire has excellent wear resistance (3-5 times as much as natural rubber and 10 times as much as practical application). It does not contain carbon black and paraffin hydrocarbons. It will greatly improve urban air quality when used in urban transportation. Compared with rubber tires, PU tires also have the advantages of low energy consumption, energy saving, emission reduction and long service life. The important raw material of rubber tire is natural rubber (NR). The tire industry in China needs NR 490-6 million tons annually, accounting for 50% of the global output, while the self-sufficiency rate is only 13-16%. A large number of imported NR is needed. At present, the price of NR is over 40,000 yuan/t. Therefore, it is imperative to actively develop PU tyres, which has been listed as the key development object of China PU Industry Association during the 12th Five-Year Plan period.

Using CPU technology, South China University of Technology has successfully developed PU-rubber composite tire, which is in the stage of industrialization. Shanghai Institute of Applied Technology is actively developing TPU tires. Relevant units are welcome to participate in the cooperation.

(4) Water-borne PU adhesives for automobiles have broad prospects for development

With the improvement of environmental laws and regulations and the increasing awareness of environmental protection, solvent-based vehicle adhesives will gradually be replaced by environmental-friendly adhesives, such as water-based adhesives. Especially the popularization and application of water-based automobile interior adhesive is imperative. Water-based interior adhesives are mainly used for adhering automotive roof, floor, carpet, dashboard, door panels and other interior decorations. At present, all the Japanese automotive interior adhesives are water-based, with 60% in the United States and only 20% in China. PU is the main type of water-based automotive interior adhesives. The technology of waterborne PU interior adhesives in China is becoming more and more mature, and should be actively promoted in the automotive field.

In addition, with the increasing use of plastic parts and the lightweight of automobiles, environmentally friendly solvent-free PU structural adhesives have broad application prospects in the automotive field, such as glass fiber reinforced plastics (FRP) and sheet moulding composites (SMC), which have been widely used in automotive body panels, roofs and cockpit covers in Europe, America and Japan. FRP and SMC can not use traditional welding technology, but must adopt bonding technology to assemble with body frame. Solvent-free PU adhesive is one of the important varieties.

(5) Bright development prospects of water-borne PU coatings for automobiles

Waterborne PU flexible coating is a kind of low VOC coating, which is 10 times lower than the volatile VOC of traditional solvent-based coating. With the lightweight of automobiles, the application of plastic parts is expanding. Environmental friendly green waterborne PU flexible materials are the future development direction of automotive plastic parts coatings.

(6) PU synthetic leather has broad application prospects in automobile interior decoration

Compared with dermis, PU synthetic leather has many advantages, such as odorless, soft handle, good wear resistance, high tear strength, good color fastness of finished products, etc. It overcomes the shortage of dermis resources and serious environmental pollution, and meets the requirements of green environmental protection for automotive interiors. Especially PU super-fibre deerskin-like velvet has the advantages of luxurious appearance, soft texture, elegant luster and good durability. It makes the interior of automobile feel like a living room. It has been favored by automobile manufacturers and has become an indispensable high-grade interior environmental protection material for high-grade automobiles.

Five.

Comfort and Safety of PU Material is Its Important Development Direction

(1) Improving vehicle comfort is an important development direction of PU automotive interiors

Car seat cushion, backrest and headrest are the parts where polyurethane foam plastics are widely used in automobiles. They are also the most sensitive places for people to ride comfortably. Therefore, the performance requirements of products are also very strict. At present, most polyurethane foam cushions used for automobiles in China are mostly uniform density cold curing products. In recent years, a new type of automobile seat cushion developed is double hardness or multi hardness foam. The production of the double hardness seat cushion can be realized by injecting polyether polyols and isocyanates through a double head or multi head mixing head. The whole MDI cold molding process can also be used, and the isocyanate index can be accurately controlled through changing the isocyanate index. Hardness of different parts of the cushion - the middle part of the cushion is soft and the sides are hard. Soft foam gives comfort to people, providing support performance on both sides of hard parts. When driving or turning at a high speed, the car helps to maintain the stability of the driver and passengers and improve the safety of the ride. Wuhan Xingqiao Polymer Technology Co., Ltd. has produced multi hardness and multi hardness foam by multi component mixing technology, and its technology level is in the leading position in China.

(2) Microporous PU used as shock absorber pad for automobile floor

Microporous polyurethane foams are expected to replace rubber materials in most car bodies as shock absorber pads for car body floor. North American car manufacturers are trying to make cars quieter and more comfortable. The shock absorber pad is mounted on the chassis of the car to isolate the body and frame so as to improve the riding and driving quality. Microporous polyurethane is a unique innovative material for sound insulation and vibration attenuation (NVH).

As a substitute for rubber body assembly, microporous polyurethane has competitive price, which can effectively improve the shock absorption performance, prolong the material performance retention time, reduce the quality, and improve the assembly process. Another advantage of using microporous polyurethane is that by changing the material density, it is convenient to optimize the shock-proof rubber pad of the body chassis, instead of adjusting the material production formula or product geometry by changing the traditional process. The latter requires prototyping, which is costly and time-consuming.

(3) Microporous PU elastomer-assisted spring shock absorber

The auxiliary spring for front and rear independent suspension shock absorber of car is made of cylindrical tower-shaped micro-porous polyurethane elastomer (micro-foam type). The use of this spring system has a particularly obvious effect on improving vehicle performance. The tensile strength, elongation and tear strength of the spring are ~20N/mm, 300% and 8N/mm respectively. Spring compression stress rises very little until the deformation reaches about 35%, and then the deformation increases rapidly, which meets the requirements of vehicle form stability and ride comfort, and greatly improves the service life of shock absorber. Some vehicles use air spring and micro-porous polyurethane elastomer spring to reduce the design volume and improve the driving stability of vehicles. According to the type of diisocyanate used in vehicle microporous polyurethane elastomers, there are NDI type and MDI type. The main difference lies in their dynamic and static properties. At present, more than 90% of luxury cars use microporous polyurethane shock absorber. Compared with rubber shock absorber, it has very high compressibility, deformation ability, excellent mechanical properties and outstanding dynamic fatigue resistance.

(four) PU bumper

Bumpers are installed in front and rear of the car, which can buffer and reduce damage during collision. The materials used are required to be both rigid and elastic. In recent years, a new type of suspension bumper made of micro-porous polyurethane elastomer has appeared. Because of its low hardness and high compression rate, the micro-porous elastomer can absorb 80% of the impact energy through deformation, and the rest of the impact energy can be transferred to the chassis. The bumper has the functions of light weight, safety, stability and silencing. Because of the high price of polyurethane material, it is widely used in Europe, the United States, Japan and China. Use it as a bumper for a premium car.

(5) PU airbag

Installing airbags on automobiles is an inevitable trend in the development of modern automotive industry, which plays an important role in protecting drivers'lives and safety. Airbags must have a certain degree of strength, able to withstand high-speed impact, and also require better low temperature flexibility. Therefore, they are suitable for polyurethane materials. Polyurethane foam is used in the cortex of airbags, polyurethane foam is used on the back, and polyurethane foam plastics are used. The material dosage of the capsule is 200-400 G.

(6) PU noise reduction technology

With the development of automobile industry, as an alternative vehicle, people not only put forward high requirements for its performance, but also put forward higher and higher requirements for its ride comfort. The noise level in the car is an important indicator of its comfort. In order to improve the comfort of vehicles, the major automotive companies in the world have formulated strict control standards for the level of vehicle interior noise, and take the control of vehicle interior noise as an important research direction. Especially for cars, interior noise is one of the criteria to measure the grade of cars. The level of vehicle motion noise directly reflects the quality level of the whole car.

Because polyurethane foaming material has the internal structure of porous sound absorbing material, i.e. it has many tiny gaps and continuous bubbles. Because of the internal friction of material itself and the friction between air and pore wall, the sound wave energy is greatly absorbed and attenuated. This kind of sound absorbing material can effectively absorb the incident sound. The above sound energy, which makes it have good high-frequency sound absorption performance. Because of the effect of friction and viscous force, a considerable part of sound energy is converted into heat energy, so that sound wave attenuation and reflection sound attenuation can achieve the purpose of sound absorption; secondly, heat loss caused by heat exchange between air and hole wall and fiber in the small hole also causes sound energy attenuation.

(7) Halogen-free flame retardant PU interiors

The flame retardant property of PU foam used in automobile interior decoration is also an important index to measure the safety performance of automobile. This kind of flame retardant material needs halogen-free flame retardant technology, which has been applied in some high-grade cars at home and abroad.

Six

conclusion

The rapid development of PU industry in China has created necessary conditions for the super-high-speed development of automobile industry in China. On the contrary, China's automobile industry will greatly promote the rapid development of PU industry.

1. China's automobile industry is the largest manufacturing and consumption country in the world, but it is not a manufacturing power. The future development of China's automobile industry will gradually change from pursuing capacity, output and scale to paying more attention to quality and level.

2. Automotive lightweight, environmental protection, comfort and safety will become the future development direction of materials for automobile industry in China.

3. PU material is the key material for realizing lightweight and plasticization of automobiles.

4. TPU plastics alloys and TPU composites will be an important technical way to realize plasticization of automobiles.

5. PU materials, PU foam plastics, PU adhesives, PU coatings and PU synthetic leather for automotive interiors must be developed in a green and environmentally friendly way.

6. PU automobile tyres and biomass vegetable oil polyols are green PU materials for automobiles, which have tremendous vitality for development.

7. PU materials include interior accessories (seats, backrest pillows), micro-porous PU elastomer cushions, shock absorber springs, bumpers, airbags and PU noise reduction technology, PU flame retardant material is an important technical way and development direction to achieve car comfort and safety.

Source: Polyurethane Alliance