Essential Car Seal Strip Tech and Application You Need Know

Overview of Automotive Seal Strips

One critical metric for evaluating automobile quality is its sealing performance. Car seal strips play a vital role in ensuring this. Their primary functions include sealing against external elements (water and dust) and isolating glass, serving purposes such as windproofing, noise reduction, vibration damping, and wear resistance.

Table of Contents

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Applications of Automotive Seal Strips

Automotive seal strips not only shield vehicles from wind and rain but also provide sealing, vibration reduction, and decorative functions. They prevent external elements like wind, rain, and dust from entering the car interior, reduce vibrations in doors and windows during driving, and enhance cleanliness and comfort for passengers. Moreover, seal strips improve the operating environment of sealed components, thereby extending their service life.

On average, a vehicle uses 10 to 15 meters of seal strips, distributed across more than ten locations inside and outside the car. This consumes 2 to 2.5 kg of rubber, accounting for 20% to 25% of the rubber used in vehicles (excluding tires). This makes seal strips a significant rubber component after tires, hoses, and V-belts.

Currently, seal strips constitute half of all industrial rubber products (calendered, extruded, and molded). Around 70% to 80% of these are used in automotive applications. Most seal strips are manufactured through extrusion processes, representing approximately 80% of all extruded products. More complex seal strips, such as those with corners, joints, or precise dimensions, require additional specialized molding processes. Automotive rubber seal strips have developed their unique production methods, achieving continuous and automated production. They have become a major focus and growth area in the rubber industry.

With the continuous advancement of automotive technology, seal strips will evolve further, incorporating new materials and processes to meet the demand for innovative products.

Classification of Automotive Seal Strips

1. By Material

Seal strips are made from various materials, including single rubber compounds and combinations of solid rubber and foam sponge rubber. The main types of rubber materials used include solid rubber, sponge rubber, and hard rubber.

2. By Application

Seal strips are categorized based on the part of the vehicle they are installed on. Examples include:

Hood Seal Strips: Used on the front, sides, and rear of the engine hood.
Door Frame Seal Strips: Provide sealing around car doors.
Car Door and Window Sealing Strips: Include front and rear windscreen sealing.
Roof Seal Strips
Glass Window Guide Channel Strips
Inner and Outer Seal Strips
Trunk Seal Strips
Sunroof Waterproof Seal Strips
Decorative Strips and Inserts

Each car model has its own specific seal strip specifications.

Door, Trunk, and Hood Seals: These typically consist of a sealing part (usually tubular sponge) and a fixing part (with or without a framework).
Guide Channel and Side Seal Strips: Installed on glass surfaces to improve sealing, reduce friction, and lower noise levels. These often feature single- or double-sided flocking.
Primary Door Seals: Work in conjunction with door frame seals to enhance overall sealing.
Window Seals: Positioned between the car body and glass for sealing and holding the glass. These seals remain under tension post-installation to ensure consistent sealing.

3. By Climate Adaptability

Standard Seal Strips: Typically used for front and rear windshields, corner windows, and side seals.
Weather-Resistant Seal Strips: Equipped with hollow sponge tubes for temperature and humidity retention, commonly applied to doors, trunks, and hoods.

4. By Structural Composition

Single-Layer Rubber Seals: Made entirely of solid or sponge rubber.
Two-Composite Rubber Seals: Combine solid rubber and sponge rubber, often with embedded metal frameworks for added strength.
Three-Composite Rubber Seals: Incorporate two types of solid rubber and sponge rubber, sometimes with a protective surface layer.
Four-Composite Rubber Seals: High-end seals with additional surface coatings for enhanced durability, primarily used in luxury vehicles.

5. By Cross-Section Shape

Seal strips come in various cross-sectional shapes, such as H-shaped, slot-shaped, and custom designs tailored for specific applications. These designs impact sealing performance, cushioning, installation, and usability.

6. By Surface Treatment

Surface-treated seal strips include:

Smooth finish
Chemically treated or coated (PU, silicone)
Flocked surfaces (single or multi-directional, colored flocking)
Fabric-lined or patterned film coatings

7. By Installation Method

Adhesive Type: Fixed using adhesives (mostly obsolete).
Embedded Type: Mechanically inserted into frames but may require adhesive reinforcement.
Clip-On Type: Features metal or plastic clips for attachment.
Insert Type: Combines U-shaped clamps with seal strips for dual sealing and decorative purposes.

8. By Additional Functional Features

Modern seal strips offer advanced functionalities such as vibration damping, corrosion resistance, and anti-pinch properties. High-end seals used in vehicle doors and windows represent the pinnacle of seal strip technology, with innovative materials and designs meeting stringent performance standards.

With increasing demands for high-performance automotive components, manufacturers like SIMBA are developing multi-material, multi-hardness composite seals to meet specific car model requirements. Innovative products, including rubber flocking seals and silicone-coated seals, are becoming industry standards. As vehicle designs diversify, seal strip specifications are expected to grow, with current estimates reaching 2,000–3,000 variations. SIMBA stands out as a leading supplier offering customized solutions for automotive seal strips.

Basic Characteristics and Performance Requirements of Car Seal Strips

Car seal strips are typical rubber extrusion products. In addition to requiring specific extrusion flow properties of the material, their exposure to external atmospheric conditions necessitates exceptional aging resistance. The goal is to match the product’s durability with the lifespan of the vehicle, typically a minimum of 10 years.

1. Geometric Shape

Car seal strips come in complex and diverse shapes that evolve rapidly. Therefore, die design is critical, as it directly impacts extrusion precision and speed. Advanced CAD/CAM technologies are essential for achieving precise product dimensional tolerances.

2. Processability

Car seal strips are often composites of rubber, plastic, metal, or fiber, available in solid, sponge, or hollow forms. They frequently undergo surface treatments such as coating, spraying, chemical modification, or electrostatic flocking. Adhesion between composite layers is crucial, determining the seal strip’s appearance and durability. Material cost significantly influences production and sales, accounting for 70–80% of the overall expense. Lightweight construction is a key focus in production and usage.

Seal strips require precise compounding and advanced vulcanization techniques, encompassing adjustments in solid rubber hardness, combinations of hard rubbers, sponge foaming control, and robust adhesion between materials. Thermoplastic elastomers like TPE and plastics such as PVC are also used.

Car seal strips serve as sealing, vibration-damping, and cushioning materials. Exposed strips also function as decorative elements. They ensure air and water sealing, noise reduction, and aesthetic appeal without odors, discoloration, or corrosiveness. They must meet environmental standards, including energy-efficient production, flame resistance during use, recyclability, and easy disposal.

High-end seal strips are vastly different from low-grade ones. For instance, wiper blades demand micron-level precision, smooth wiping motion, and clean operation, often requiring premium HNBR rubber.

Seal strips are highly specialized, with specific designs for each door or window, forming integral components of the car body. They require synchronized design and assembly with the vehicle, ensuring seamless integration from body panels and glass to seals and molds.

Seal strips must also facilitate easy installation and removal, resist scratches from glass and metal, and withstand repeated disassembly without deformation or damage. For movable seal strips, flexibility and lightweight construction are vital to prevent injuries from pinching.

3. Material Mechanical Properties

Solid rubber strips:
Hardness (Shore A): Typically 60±5.
Tensile strength: ≥7 MPa, elongation ≥300%.
Compression set (70°C for 22h and 100h): ≤30% and ≤50%, respectively.
Sponge strips:
Density: 0.4–0.9 g/cm³.
Water absorption: ≤2%.
Tear strength: ≥1 N/m.

For composite seal strips, adhesion and peel strength are crucial, typically ≥60 N/m and ≥30 N/m, respectively.

Material Types and Properties

EPDM (Ethylene Propylene Diene Monomer):
Used for car window seals with sponge layers. EPDM features ozone, UV, and heat resistance, stability with paint, tensile strength ≥7.6 MPa, and elongation 200–550%. It resists corrosion, has foam cell diameters ≤0.5 mm, and exhibits minimal permanent deformation (≤40% after 94h at 23°C).
Neoprene Rubber:
Hardness (Shore A): 70±4.
Tensile strength: ≥8.0 MPa (≥6 MPa under various conditions).
Elongation: 200–500%.
It offers stability with paint, weather, ozone, and abrasion resistance, even at -35°C.

Weathering Performance and Surface Treatments

Car seal strips exposed to atmospheric conditions must pass stringent durability tests, including:

Weather resistance: 300h in a sunlight aging tester.
Ozone resistance: 50×10⁻⁶ ozone at 38°C, 30% elongation for 70h.
Flex resistance: 300 cycles per minute for 500,000 cycles.
Cold resistance: -40°C for 5h with 180° bending, showing no abnormalities.

Repeated installation and removal should leave no marks on metal or glass surfaces. Currently, only a few materials like EPDM meet these requirements.

Surface coatings, especially for glass-run channels, are critical for durability, freeze resistance, sealing, sound insulation, and low friction. Specific tests ensure wear resistance (10,000–20,000 cycles), friction coefficients ≤0.3–0.4, and durability under conditions of moisture, weather, and heat.

Seal strips typically operate within a temperature range of -40°C to 70°C, necessitating excellent low-temperature performance.

As shown:

Performance Specifications for Automotive Weatherstripping
Property	Volkswagen	General Motors	Honda	Toyota	National Standard	Industry Standard
Tensile Strength (MPa)	≥6.0	≥7.0	≥7.0	≥7.0	≥7.0	≥7.0
Elongation at Break (%)	250-550	≥300	≥200	200-300	250-350	≥200
Brittleness Temperature (°C)	-35 (remains elastic)	-40 (remains elastic)	-40 (remains elastic)	-40 (remains elastic)	-35	-35

4. Material Chemical Properties

The rubber materials used in car seal strips are predominantly EPDM rubber, valued for its excellent resistance to aging, low temperatures, water vapor, and chemical corrosion, particularly ozone aging. This rubber also offers good processability and can be combined with steel strips, woven steel wire, velvet, flocking, PU coatings, or silicone coatings. These combinations ensure the car seal strip performs its functions of waterproofing, dustproofing, sound insulation, thermal insulation, vibration reduction, and decoration. Under typical conditions, EPDM seal strips can achieve a service life of over a decade.

5. Performance of Finished Products

① Compression Force

Car seal strips, especially those used for door frames, trunks, and engine covers, must balance compression force effectively. For example, when closing a car door, the seal strip should require minimal force (“closing force”), yet after the door is closed, it should exert greater compression force to ensure proper sealing. To address this balance, the compression force of car seal strips is carefully designed, often using CAD, CAE, and finite element analysis.

To reduce closing force, manufacturers implement strategies such as adding air vents to the seal strips to release air when compressed or applying PU or silicone coatings on the contact surfaces to reduce friction between the seal strip and the door.

② Insertion and Pull-Out Forces

Insertion force refers to the effort needed to press a seal strip into its fixed position on the car body, while pull-out force measures the effort required to remove it. These forces impact the strip’s operational state and assembly process. The gripping section of a seal strip, responsible for pull-out force, is often made of harder solid rubber or a combination of solid rubber and bent skeleton materials. The interior is designed with reverse teeth to prevent slippage.

Ideally, a seal strip should have low insertion force but high pull-out force. However, these two forces are inherently linked; decreasing one usually decreases the other. This balance complicates the design and installation process. For example, pre-bent seal strips designed for stronger pull-out force may require greater insertion force, making installation more challenging.

The traditional method of installing seal strips involves using a mallet (wooden or rubber) to hammer the strip into position. If pull-out force is too high, excessive hammering could damage the strip’s surface. Therefore, the gripping structure must achieve a balance between insertion and pull-out forces.

To address this challenge, some manufacturers now use a rolling method for installation. This process involves a pneumatic tool with a rotor to press the gripping section of the seal strip uniformly into place, improving installation quality and reducing worker fatigue. This innovation offers a new solution to the insertion and pull-out force dilemma.

③ Abrasion Resistance of Flocked Surfaces

Flocked car seal strips, typically installed at window positions, must withstand frequent friction with the glass. Therefore, their flocked surfaces require excellent abrasion resistance.

④ Abrasion Resistance of Coatings

Car door seal strips and first-line sealing strips experience high-frequency friction during door opening and closing. As a result, the abrasion resistance of their coatings is critically important.

Main Materials of Car Seal Strips

Car seal strips are made from a variety of materials, including rubber, rubber-plastic composites, rubber combined with metals, fabrics, steel, and flocking.

(1) Rubber and Plastic Materials

The primary material for car seal strips is rubber, which must exhibit excellent resistance to UV aging, ozone aging, thermal oxidation aging, as well as low compression set, low creep, and high durability in extreme temperatures and wet conditions. In terms of processing, the rubber should feature easy extrusion, minimal shrinkage deformation, and good flexibility.

Commonly used rubber materials for car seal strips include SBR (Styrene-Butadiene Rubber), which incorporates high-fill reinforcement and multi-physical-chemical anti-aging systems. High-quality products often utilize CR (Chloroprene Rubber). In recent years, EPDM (Ethylene Propylene Diene Monomer) has become the preferred material due to its superior characteristics. However, the high cost of EPDM and CR means that cheaper seal strips often substitute PVC and modified PVC. For premium products, PU seal strips are widely used.

The materials for automotive seal strips are diversifying, primarily using rubber, with material selection depending on the application, service life, and cost. Environmentally friendly and energy-saving TPV (Thermoplastic Vulcanizates) is gaining traction in the industry and is expected to see wider application in seal strip manufacturing.

Car door seal strips are typically made from EPDM rubber, CR, SBR, and rubber-plastic composites. EPDM is commonly used as the base material, with specific formulations to meet the varying demands of different vehicle seal strip types and installation locations.

Thermoplastic elastomers (TPE) are also widely used in automotive seal strips. High-molecular-weight TPV is utilized for extruding automotive glass channel seals and corner joints. Additionally, water-foamed sponge TPV has been developed, replacing sponge rubber in car seal strips. TPV’s easy coloring makes it ideal for external decorative materials in car seal strips. Chinese manufacturers have introduced co-extrusion technology for colorful TPV and rubber seal strips.

Advancements in car seal strip technology have enabled rapid vulcanization of EPDM rubber. Meanwhile, manufacturers are exploring thermoplastic elastomers to potentially replace EPDM-based seal strips.

Thermoplastic Elastomers (TPE):
TPE combines the physical and mechanical properties of rubber with the processing characteristics of plastics, making it an ideal material for energy-saving and efficiency-enhancing applications. TPE materials such as SBS, TPO, TPV, TPU can be used for car seal strips. However, their relatively poor elasticity, high compression set, and challenges in forming sponge structures limit their application, primarily to window strips and glass channels. TPV is closer to rubber but is costly, while TPU is an excellent seal strip material but is limited to specific high-end applications due to its high price.

Compared to EPDM rubber, TPE’s advantages include recyclability, injection molding capability, and superior tear strength, addressing some of the limitations of EPDM.

(2) Framework Materials

The framework materials of car seal strips vary based on the manufacturing process and include steel strips, braided steel wires, and aluminum strips:

Steel Strips:
- Tension Steel Strips: Symmetrical or asymmetrical types.
- Punched Steel Strips: Single-bridge (fishbone-shaped) or double-bridge punched steel strips.
Single-bridge punched steel strips can only bend radially and cannot be folded. Double-bridge punched steel strips can bend in multiple directions.
Braided Steel Wires and Aluminum Strips:
Used based on structural needs and manufacturing cost considerations.

Framework material selection must consider the structure of the seal strip’s mating position with the car body (including curvature radius), clamping force requirements, processing costs, and quality expectations.

Processing Methods and Production Equipment for Automotive Sealing Strips

(1) Processing Methods for Automotive Sealing Strips

Automotive sealing strips widely use EPDM as raw material, while thermoplastic elastomers (TPV, TPO), known for their energy-saving and eco-friendly properties, are increasingly applied. These sealing strips are typically processed through extrusion molding. Earlier methods were relatively simple, using basic molds. However, the advent of microwave vulcanization technology in the 1970s marked a new era in automotive sealing strip production internationally. Subsequently, technologies like variable cross-section extrusion, injection molding for joints, EPDM electrostatic flocking, silicone surface coatings, and TPV sponge strip water foaming have been developed and refined.

In the 1980s, Europe introduced high-temperature, multi-directional airflow vulcanization extrusion lines, eliminating the need for microwave vulcanization tanks and enabling faster vulcanization, particularly for thinner products. As vehicle sealing requirements have grown, demands for sealing strips have increased, leading to more advanced materials and techniques. For instance, thermoplastic elastomers such as TPO and TPV are now replacing EPDM due to their dual advantages of elasticity and plasticity, ease of processing, and recyclability.

Modern automotive sealing strips often consist of a co-extruded solid carrier and sponge rubber tubing. The sponge component provides sealing when compressed by the door frame. However, at high speeds, external air pressure can exceed the sponge’s maximum sealing force, leading to seal failure. To address this, some companies have developed innovative profiles incorporating magnetic rubber into the sponge layer or applying magnetic coatings to enhance sealing performance.

(2) Production Methods for Rubber Sealing Strips

Rubber sealing strips are produced using three primary methods:

Extrusion followed by batch vulcanization: This simple and versatile method is suitable for small-batch, multi-variety production.
Continuous vulcanization after extrusion: A modern, high-efficiency production method involving an automated line of 100–200 meters, ideal for large-scale, consistent production.
Mold vulcanization post-extrusion: A complex process requiring flat-plate or injection molding machines, mainly for producing joints and special sealing strips.

Characteristics of Major Vulcanization Methods:

Microwave vulcanization: Suitable for thick-walled or complex-shaped strips. It offers fast and uniform heating with minimal waste but requires high carbon black dispersion in the material. It’s ideal for non-peroxide-cured polar rubber materials.
Shear head vulcanization: Suitable for both polar and non-polar rubbers, with fast and uniform heating. However, it is not ideal for low-viscosity or peroxide-cured materials.
Salt bath vulcanization: Known for excellent heat transfer and fast vulcanization. While it produces high-quality sponge rubber strips, it poses environmental concerns due to pollution.
Fluidized bed vulcanization: Ideal for sponge rubber strips, with smooth finished surfaces and minimal deformation. However, it is limited by its inability to use peroxide-cured materials.

The most widely used methods today are microwave vulcanization and salt bath vulcanization. Salt bath methods, despite their pollution issues, remain valuable due to advancements like new liquid curing media and recycling technologies.

(3) Joint and End Molding

Traditionally, joints and ends of sealing strips were formed using flat-plate vulcanization. Now, specialized rubber injection molding machines are commonly used, offering higher efficiency and flexibility. Rotary rubber injection machines with multiple molds are also employed for higher productivity.

(4) Post-Processing and Equipment

Post-processing is a critical part of sealing strip production. Key equipment includes:

Spray coaters: Save 30–50% of coating materials compared to brushes.
Filling machines: Inject sealant into joints for an integrated structure.
Steel core handling machines: Bend steel cores without damaging the rubber surface.
Cutting and punching machines: Ensure precise customization for various applications.

The continuous innovation in processing and equipment has significantly improved the quality, efficiency, and environmental sustainability of automotive sealing strip production.

Car Door Seal Strip Product Analysis

The car door seal strip is one of the most important seal strips in car seal products, directly affecting the sealing quality of the cabin. It plays a dominant role in the overall vehicle sealing quality evaluation.

The car door seal strip is installed on the edge of the car door frame, sealing the gap between the car door and the door frame. As the car door operates in two states (open and closed), this type of seal is classified as a dynamic seal. So how can you assess the performance and quality of the car door seal strip you purchase? Generally, this can be analyzed from several aspects: usage, installation, maintenance, recycling, and relevant laws and regulations.

① Performance of car door seal

After comparing and analyzing the standards of various international automobile manufacturers regarding car door seal strips, the performance requirements for a car door seal strip should include the following: isolating the cabin from external influences (water, air, dust, noise); being securely fixed to the car door frame edge; having a certain service life; meeting the requirements for sound, odor, appearance integrity, and aesthetics; and meeting the requirements for the door’s opening and closing performance.

The following will analyze and discuss these performance requirements in detail.

a. Cabin Sealing Performance

Cabin Sealing Performance is the primary function of the car door seal strip, determining the overall product quality. The testing items and evaluation methods are as follows in the table:

Test Item	Inspection Method
Rain Test	Visually inspect the vehicle cabin for any water intrusion.
Dust Test	Visually inspect the vehicle cabin for any presence of dust.
Soundproofing Test	Compare the measured attenuation curve with the standard curve.

b. Fixing Strength

The car door seal strip is fixed to the edge of the car door frame using its built-in U-shaped installation slot. To ensure that the seal strip does not detach during operation, it must have a certain pull-out strength. Theoretically, the greater the pull-out strength, the better; however, in practical applications, a minimum value is typically set to control the fixing strength of the door frame seal strip. This is because the pull-out strength comes from the frictional resistance between the sealing teeth and the edge of the door frame. If the pull-out strength is too high, it can result in excessive insertion force, which in turn affects the installation of the car door seal strip. Through comparative analysis, the control range for pull-out strength is determined to be no less than 50N/100mm, with a pull-out speed of 200mm/min.

The pull-out strength test method for the car door seal strip is shown in the diagram:

c. Service Life

The polymer elastic materials used in the production of seal strips will experience varying degrees of aging and wear during use. Typically, the following requirements are expected for the service life of car door seal strips:

ⅰ. Length Shrinkage Rate: A car door seal strip with a length of approximately 1 meter (accurate to 0.5mm) is installed on a 0.5mm thick stainless steel stop edge, without any stretching or compression in the length direction. After undergoing 5 cycles of high and low-temperature storage tests (80°C±2°C for 3 hours → room temperature for 0.5 hours → -30°C±2°C for 2 hours → room temperature for 0.5 hours, 1 cycle), the shrinkage rate of the component’s length should not exceed 1%.

ⅱ. Compression Permanent Deformation Rate: A car door seal strip with a length of 100mm is installed on a test fixture, and compressed to heights corresponding to the door frame design gap H and the minimum gap H-2mm. After 5 cycles of high and low-temperature storage tests (80°C±2°C for 3 hours → room temperature for 0.5 hours → -30°C±2°C for 2 hours → room temperature for 0.5 hours, 1 cycle), the change rate in the component’s sectional height should not exceed 50%.

ⅲ. Compression Load Loss Rate: A car door seal strip with a length of 100mm is installed on a test fixture and compressed to heights corresponding to the door frame design gap H and the minimum gap H-2mm. After 5 cycles of high and low-temperature storage tests (80°C±2°C for 3 hours → room temperature for 0.5 hours → -30°C±2°C for 2 hours → room temperature for 0.5 hours, 1 cycle), the loss rate of the compression load on the component should not exceed 50%.

ⅳ. Wear Resistance Test: A car door seal strip with a length of 100mm is installed on a test fixture (as shown in Figure 5-20). The friction head is generally chromium-plated, with a friction speed of 60 cycles/min (one cycle for both forward and return motions), a stroke of 50mm, and a pre-load to compress the sectional height to match the door frame design gap H and the minimum gap H-2mm. After 1000 friction cycles, the component’s surface should not show any visible damage.

ⅴ. Seal Tube Tensile Strength: A car door seal strip with a length of 50mm is installed on a test fixture and subjected to a tensile test at a speed of 100mm/min. The maximum tensile force at the point of seal tube rupture should not be less than 150N.

ⅵ. Ozone Aging Resistance: A long strip sample is cut from the car door seal strip component for testing. The general test conditions are: ozone concentration of 200×10⁻⁶, sample pre-stretched by 20%, and a temperature of 40°C. After 72 hours, the sample should show no cracking.

ⅶ. Light and Weather Resistance: A 100–200mm length section of the car door seal strip is placed in a xenon light aging chamber for 1000 hours of aging tests. The tests are conducted under both rain and no-rain conditions. After aging, the sample should show no decomposition, brittleness, cracking, discoloration, or other defects compared to its pre-aging condition.

ⅷ. Salt Spray Test: Since the U-shaped installation groove of the car door seal strip embeds a metal skeleton, this test is necessary to control the product’s service life. Typically, a segment of the car door seal strip is placed in a salt spray test chamber. After 144 hours of testing at 35°C, there should be no accumulation of red rust.

ⅸ. Seal Tube Water Absorption Rate: As the seal tube is generally made of foamed EPDM material, waterproofing is one of its primary functions. The absorption rate should not exceed 5% after the seal tube is soaked in water for 24 hours at room temperature.

ⅹ. Compression Fatigue Test: The car door seal strip is installed on a standard vehicle body. The car door is opened and closed at a speed of 1.5m/s, with each opening and closing cycle counting as 1 cycle. After 50,000 cycles, the seal strip should show no significant defects.

ⅺ. Paint Board Contamination Test: A 100mm long car door seal strip is used, with its sealing part in contact and compressed against a light-colored painted board. After being placed in an 80°C oven for 24 hours, the painted board should show no contamination on its surface.

d. Requirements for Sound, Odor, Appearance Integrity, and Aesthetics

The door frame seal strip is not only a functional component but also an important decorative element. International automotive manufacturers have specific performance requirements for the door frame seal strip in terms of auditory, olfactory, and visual aspects, as outlined below:

ⅰ. Sound Requirements: During the process of opening or closing the car door, the car door seal must not generate disturbing noises, such as the whistling sound of air being expelled or drawn through the sealing tube or squeaking noises.

ⅱ. Odor Requirements: The car door seal must not emit any unpleasant odors that could contaminate the air inside the cabin.

ⅲ. Appearance Integrity and Aesthetic Requirements: The car door seal should harmoniously match the interior components of the cabin. Its surface should be free from bulges, scratches, cracks, dents, folds, color differences, or other cosmetic defects. The decorative patterns should be clear and even.

e. Requirements for Door Opening and Closing Performance

The car door seal strip’s influence on the door’s opening and closing performance primarily manifests in the force required to open or close the door and the associated noise under various environmental conditions.

ⅰ. Compression Load (Curve): The force required to open or close the car door can be measured through real vehicle testing. The compression load value at the sealing area of the seal strip is used for design and control. A higher compression load means greater force required to open and close the door, and better sealing performance of the door frame seal strip; a lower compression load means less force required and poorer sealing performance. Therefore, when considering the compression load of the door frame seal strip, both the cabin sealing performance and the door opening and closing performance should be taken into account, typically within a reasonable range.

ⅱ. Freezing Adhesion Performance: After installing the door frame seal strip on a standard vehicle body and conducting a rain test, the vehicle is placed in an environment at -15°C until the water remaining on the body freezes. A door opening test is performed, and the door must be able to open without tearing the sealing tube of the door frame seal strip.

ⅲ. Door Opening Noise Performance: The door frame seal strip is installed on a standard vehicle body, and the maximum noise at the moment of door opening is measured. Generally, for sedans, this noise level should not exceed 80 dB.

② Car Door Seal Installation Performance

Due to the strict pace requirements of the automotive assembly line, car manufacturers have specific installation performance requirements for the car door seal as follows.

a. Insertion Force

The smaller the insertion force when installing the car door seal, the better. However, in order to ensure the secure attachment of the car door seal to the door frame edge, an excessively small insertion force will inevitably lead to a decrease in the pull-off force of the seal. Therefore, the insertion force of the car door seal is generally controlled within a maximum value. Typically, the insertion force should not exceed 50N/100mm, with an insertion speed of 200mm/min.

b. Joint Strength

Based on the sealing gap and appearance requirements of the car door seal, the corner areas often require molding joints or direct molding of the car door seal into a closed loop. To ensure the car door seal’s tensile or bending strength during installation, the joint strength is generally required as follows:

Joint Tear Strength
Measure the tear strength along the joint axis. The typical requirement is that it should not be less than 100N.
Joint Bending Strength
After bending the joint area around a cylinder with a radius of 30mm, no cracking should occur on the joint surface.

c. Product Labeling

Since most cars have four doors, the seal strips for the four door are typically symmetric left and right and similar front and rear, making them easy to confuse. Therefore, clear identification must be made on the product to distinguish them. Additionally, to meet traceability requirements, the product must be marked with information such as the supplier’s name, part number, production batch, production date, and material type.

③ Maintenance and Repair Performance of Car Door Seal Strip

The following specific requirements must be adhered to for the maintenance and repair of car door seal strips:

a. Repetitive Disassembly and Installation Performance: After being disassembled and reinstalled three times, the pull-out force of the car door seal strip should not decrease by more than 15%, and no deformation, cracking, or scratches should appear on the surface.

b. Interchangeability: When replacing an old or damaged car door seal strip, no adjustments or replacement of other related components should be necessary upon reinstallation of the new seal.

c. Paint Oven Bake Performance: When the car’s paint is damaged and requires repair, the car door seal strip must maintain all of its performance characteristics after exposure to the paint oven. Typically, the seal strip is placed in a 110°C oven for 30 minutes, followed by various performance tests.

d. Wash Liquid Resistance: The car door seal strip must resist corrosion from various automotive cleaning liquids without any degradation in performance.

e. Resistance to Anti-Corrosion and De-Corrosion Agents: During the sea transport of vehicles, anti-corrosion treatment is applied to prevent seawater corrosion. Therefore, the car door seal strip must withstand the corrosion of anti-corrosion agents and de-corrosion agents without any decline in performance.

④ Recyclability of Car Door Seal Strips

To protect the environment and facilitate the recycling of car door seal strips, the material type used, such as EPDM, PP+EPDM, etc., is typically marked in the invisible areas of the parts after assembly. These markings should be permanent and non-removable.

⑤ Laws and Regulations

The laws and regulations concerning car door seal strips mainly cover the following two aspects:

i. Flammability Performance: According to GB8410 “Burning Characteristics of Automotive Interior Materials,” the horizontal burning rate should not exceed 100 mm/min.

ii. Prohibited Materials Management: The car door seal strips must comply with the regulations regarding prohibited materials management in the country or region of production and sale.