For a long time, automotive sealing strips must have th […]
For a long time, automotive sealing strips must have three major functions: connectivity, sealing and decoration. With the advancement of science and technology and the development of the automobile industry, especially the emergence of new materials, people have higher and higher requirements for the environmental protection, comfort, safety, and aesthetics of automobiles, and the three previous functions of automobile sealing strips The requirements of the company are constantly innovating and improving. In order to meet the needs of continuous improvement in the performance and grade of passenger cars, the development trend of the door sealing strip industry is analyzed and studied from the application materials, product structure and production technology of passenger car sealing strips.
1. Review of the development process of passenger car sealing strips
Before the 1980s, due to the limitation of the level of science and technology at that time, almost all automobile sealing strips only considered the connection performance and partial sealing performance, and rarely considered the decoration, safety and comfort. Therefore, the sealing strips used in passenger cars at that time only considered more in terms of connectivity, such as the sealing strips for front and rear wind windows, side windows, and doors; the structure is also very simple, mostly using a single type of glue, one end is connected to the body, the other is connected to the glass, etc. ; The materials are mainly natural rubber or styrene butadiene rubber and plastics (mainly modified PV C ). Although such a sealing strip satisfies the connection performance and part of the sealing performance, other properties such as elasticity, water resistance, noise prevention, isolation, dust resistance, heat resistance, weather resistance, ozone resistance, and aging resistance are poor, let alone Aesthetics and comfort are gone. Due to the limitation of the material's own performance, the service life of the car sealing strip is only 3 to 5 years, which cannot match the service life of the passenger car; the color is relatively simple (the rubber is almost all black), and it is not decorative and beautiful. Sex up. The airtightness of the door, body, and luggage compartment is poor, the noise inside the car is louder, and the effect of dust and water resistance is also very poor. In the late 1980s, with the continuous improvement of passenger car grades, the requirements for passenger car sealing strips also increased correspondingly.
2. The current status of passenger car sealing strips
Since the 1980s, the automotive industry has placed increasingly higher requirements on the overall performance of the parts and components industry, and of course the sealing strip industry has also made great progress.
(1) The product structure of the sealing strip has changed a lot. Change the original single rubber type to the current two-composite rubber type (that is, the compound of dense rubber and dense or sponge rubber), three-composite material (that is, the composite of dense rubber, sponge rubber and steel or nylon skeleton), and four-composite material ( That is, the composite of dense rubber, sponge rubber, steel or nylon skeleton, and flocking).
(2) There has been a new development in the application of materials. Natural rubber (or styrene butadiene rubber) and plastics with poor strength, heat resistance, weather resistance, and aging resistance are discarded, and synthetic ethylene propylene diene monomer (EPDM) rubber (EPDM) is used. EPDM has excellent heat resistance, weather resistance, and ozone resistance. Its main physical properties are shown in Table 1. Due to the excellent characteristics of EPDM, production and sales have continued to grow in recent decades.
(3) The production process bids farewell to the original production process of pure rubber extrusion steam vulcanization tank vulcanization, and adopts a more advanced multi-head extrusion microwave vulcanization production process, as well as an injection secondary processing molding process.
Obviously, the first and most basic function of the sealing strip is to seal, which needs to be waterproof, noise-proof and dust-proof. In fact, the sealing effect can be further improved by improving the design. At present, the anti-friction requirements of materials are getting higher and higher, so that the sealing performance can be maintained for a longer time, and the damage can be reduced during the initial installation. The main function of the seal is to isolate the inside of the car from the outside as much as possible, and to maximize the ride comfort of the driver and passengers. It should be said that the current sealing strips are greatly improved in terms of connectivity, sealing, decoration, and safety compared to before the 1980s, but there is still a certain gap in terms of decoration and environmental protection.
3. The development trend of passenger car sealing strips
The rapid development of the automotive industry has put forward higher requirements for various performances of automotive weather strips. The development of science and technology, the application of new materials and new processes have provided development space for the development of the sealing strip industry. The requirements for sealing strips do not only stop at the three major functions of connectivity, sealing and decoration, but also put forward new requirements for the environmental protection, safety, comfort and beauty of the car. This requires continuous improvement in the selection of materials, the improvement of the structure, and the selection of the manufacturing process for the sealing strip.
(1) From the selection of materials, it is not only limited to the application of E PDM. Thermoplastic elastomers with relatively simple molding processes: T PV (thermoplastic vaporized elastomer), T P E (thermoplastic elastomer), T PO (thermoplastic olefin), etc., have been widely used in some aspects. They have strong coloring properties, good composite and recyclability, and can also meet the requirements of environmental protection. The physical properties of the thermoplastic elastomer are shown in Table 1, and its advantages are as follows: excellent flexural fatigue life; high temperature resistance; high impact strength; low density; excellent chemical resistance and weather resistance; good electrical properties; high Tearing resistance and high abrasion resistance; colorability; reproducibility; co-injection and co-extrusion molding with polyolefin; low tensile and compression set.
(2) Structural improvement: the use of exterior surface composite and automotive interior
Coordinated various materials of different colors, such as colored EPDM, colored thermoplastic elastomer; Use surface spraying wear-resistant and lubricating materials to replace the original flocking materials; Apply surface spraying of various smooth, matte or colored four-composite materials .
(3) Process improvement: Full use of pre-shaping + high-speed hot air + microwave vulcanization + ordinary hot air vulcanization process, greatly improving the vulcanization surface quality and production efficiency of the sealing strip; cancel the original molding process and replace it with various The secondary processing technology of injection molding not only improves the efficiency but also improves the product quality; the online spraying process replaces the original manual spraying process.
In short, with the continuous improvement of automobile grades, the performance requirements of passenger car sealing strips have also increased correspondingly. The rationality of the structure, the humanization of the design, the flow and automation of the production process, the product safety, environmental protection, recyclability, matching aesthetics, and diversity are all important performances that need to be considered for passenger car sealing strips.