Goggle skirt fit technology

Gasket Fitting Technology for Swim Goggles: Principles, Materials, Processes, and Performance Optimization  

Abstract: The gasket fitting technology of swim goggles is a core factor determining their waterproof sealing, wearing comfort, and service life. This paper systematically expounds the structural design principles of the goggle gasket, compares and analyzes the performance differences between the two mainstream gasket materials—TPE and silicone—explores the technological evolution path of overmolding processes, and discusses sealing performance optimization, aging failure analysis, and standardized testing, aiming to provide a reference for the R&D, design, and quality control of swim goggles.  

I. Introduction  

The gasket of swim goggles—the soft sealing ring on the back of the frame that conforms to the wearer’s face—is one of the most inconspicuous yet critical components of the entire product. Its technical level directly determines whether the user can keep water out of the eyes during dynamic scenarios such as high-speed swimming, underwater somersaults, and head-turning for breathing, while avoiding deep marks left on the face due to excessive pressure. An improperly designed gasket can lead to water leakage and frequent lens wiping, or worse, impair athletic performance and even cause eye injury. However, for a long time, the waterproof sealing of swim goggles has relied excessively on the crude strategy of "tightening the head strap," which not only compromises user comfort but also reveals the deep-seated limitations of traditional gasket design and manufacturing systems. This paper provides a systematic and professional review of gasket fitting technology for swim goggles from the perspectives of structural principles, material science, manufacturing processes, performance optimization, and testing standards.

II. Structural Principles and Design Philosophy of the Gasket

From a functional perspective, the gasket of swim goggles plays a dual role: it acts as a “sealing barrier” that prevents water from entering the eye cavity during swimming, while also serving as a “comfort layer” that remains in prolonged direct contact with the periorbital soft tissues. These two roles inherently create tension—the stronger the seal, the greater the compression force typically required, and the poorer the comfort.

Traditional swim goggle gaskets mostly adopt a simple curved-bend structure. Although they provide basic conformity, their sealing performance depends entirely on strap tension, lacking any cushioning mechanism. As noted in a granted invention patent, the drawback of such simplistic structures is that “the wearer either fastens the goggles too tightly, or when diving under high water pressure, the face-contacting surface excessively compresses the user’s face,” leaving “deep pressure marks after removal.”

To resolve this contradiction, contemporary swim goggle gasket designs have introduced several key structural concepts.

2.1 Buffer Space Design

One important structural innovation is the provision of a buffer space between the contact surface of the gasket and the inner side of the lens frame. Specifically, the gasket bends toward the inner side of the frame, forming a contact surface that conforms to the face. Through a defined radius of curvature, a curved surface is created, leaving a certain gap between the contact surface and the inner side of the lens frame. When the user wears the goggles, the tension from the head strap compresses this buffer space, but the pressure does not directly act on the bony or soft tissue limits. Instead, it achieves an effect of “tighter fit without tighter pain.”

2.2 Differentiated Hardness Zoning

The stress characteristics on different facial regions against the sealing gasket vary significantly. The nasal bridge has prominent bone with very limited contact area; the eye socket area has abundant soft tissue capable of greater deformation; the area below the cheekbone, near the muscle attachment zone, requires moderate support without excessive pressure. Speedo’s IQFIT technology starts from this premise, employing a triple-gradient silicone structure with varying softness—the softest part contacts the skin to form a seal, the middle layer provides rebound cushioning, and the outer edge maintains frame stability. This allows the same pair of goggles to achieve differentiated support across the three key pressure zones: the nasal bridge, the eye sockets, and the cheekbones. This design cleverly balances personalized fit and wearing stability. Studies have shown that traditional fixed goggles exhibit a sealing degradation rate of up to 37% during dynamic head-turning, while the IQFIT structure reduces this figure to less than 9%. This data strongly demonstrates the practical value of refined structural design in enhancing sealing stability.

2.3 Multi-layer Sealing Structure

Adding an inner frame layer between the gasket contact surface and the lens frame is another effective strategy. Speedo’s Biofuse series employs a dual-layer structure consisting of a “soft outer layer + rigid inner frame.” The soft outer gasket conforms to facial contours and forms a seal, while the rigid inner frame withstands water impact forces during swimming, maintaining the overall stability of the lens frame. This “division of labor” structural layering avoids placing all functional pressure on a single gasket structure, thereby improving system reliability.

III. Material Selection and Performance Comparison of Gasket Materials

The choice of gasket material directly affects the product's physical performance, manufacturing cost, and user experience. Currently, the main materials for swim goggle sealing gaskets are thermoplastic elastomer (TPE) and silicone. These two technological routes each have their own advantages and disadvantages, resulting in a clear market segmentation.

3.1 Thermoplastic Elastomer (TPE)

TPE is a class of thermoplastic materials that combine the high elasticity of rubber with the processability of plastics. It is typically modified by blending with SEBS elastomer as the main base material. The advantages of TPE for swim goggle gaskets are concentrated in the following areas:

- High processing efficiency: TPE can be directly overmolded onto PC frames via injection molding without the need for vulcanization, resulting in short molding cycles and significantly improved production efficiency.
- Environmentally friendly and recyclable: TPE complies with environmental directives such as ROHS and REACH, and defective products as well as scrap material can be reprocessed and recycled.
- High tunability: Hardness can be flexibly adjusted within the range of 25A to 95A, and surface finishes such as natural, translucent, or transparent effects can be achieved.

However, TPE is slightly inferior to silicone in terms of long-term tensile recovery. Under high-intensity, repeated use, it may exhibit a certain degree of plastic deformation tendency. Therefore, TPE is mostly used in mid-to-low-end swim goggle products.

3.2 Silicone

Silicone is a thermosetting rubber material with higher tensile recovery and temperature resistance. Medical-grade silicone is gentle on the skin, non-allergenic, and offers good chemical stability and aging resistance. The disadvantages of silicone lie in its more complex processing it requires compression molding or liquid injection molding combined with vulcanization and defective products cannot be recycled, resulting in a higher unit cost. Consequently, silicone is typically used in high-end swim goggle products.

3.3 Summary of Material Comparison

Both materials exhibit good low-temperature resistance, maintaining softness and elasticity even at -30°C. Practice has shown that TPE is suitable for product routes prioritizing production efficiency and cost-effectiveness, while silicone serves the high-end market pursuing ultimate performance and comfort.

IV. Manufacturing Processes for Gasket Production

The core challenge in gasket manufacturing lies in how to firmly bond soft, highly elastic materials with rigid PC frames, ensuring a seamless interface between the two while achieving high-efficiency, high-yield mass production.

4.1 Traditional Two-Step Injection Molding Process

The traditional manufacturing process follows a "step-by-step" mode: first, the lens is placed into the first mold for initial overmolding, forming the outer frame that holds the lens; then, the semi-finished product from the first overmolding is removed and placed into another mold for a second overmolding step, forming the sealing gasket around the periphery of the lens. Although feasible, this process has significant drawbacks: first, it involves multiple steps, requiring two mold openings/closings and two mold changes; second, extensive manual intervention increases the risk of contamination or damage to the product between the two injection steps, leading to a higher rejection rate; third, in terms of equipment occupancy, labor costs, and cycle time, it struggles to meet the efficiency demands of modern production lines.

4.2 Two-Color Overmolding Process: A Breakthrough in One-Step Molding

The true driver of high-efficiency gasket manufacturing has been the introduction of two-color overmolding mold technology. This innovation fundamentally changes the traditional manufacturing logic.

Represented by a patented invention from Huakai Sports Goods (Suzhou) Co., Ltd., the designed vertical two-color overmolding mold features two independent hot runner systems (first and second hot runners) in the upper mold half, used for injecting hard plastic and soft rubber materials respectively. In the lower mold half, a first ejector block and a second ejector block cooperate to form two stacked cavities—the first cavity for molding the outer frame, and the second cavity arranged around the lens periphery for molding the sealing gasket. The entire process flow is straightforward: the lens is placed on the contoured surface of the second ejector block in the lower mold; after the mold is closed, both injection systems simultaneously inject materials into their corresponding cavities. In one open-and-close cycle, a fully overmolded pair of swim goggles is produced.

The advantages of the two-color overmolding process are:

Doubled efficiency: Both materials are injected in a single mold closure, eliminating switching and waiting between two processes. According to the patent data, this solution "reduces one injection molding machine, two workers, and halves the production cycle."
Improved yield: Since the entire process from lens insertion to removal is completed within the same closed mold, errors and contamination risks from manual handling and repositioning are minimized.
Integrated sealing: The rigid frame and soft gasket form a molecular-level bond within the same molding cycle, resulting in higher interfacial bond strength and better sealing reliability.

This process represents not only a major technological advancement in swim goggle manufacturing but also an industry trend toward replacing "step-by-step assembly" with "one-step molding."

4.3 Technical Details of Overmolding Bonding

The key to the overmolding process lies in the bond strength between the TPE soft material and the PC rigid frame. The conventional approach requires surface pretreatment of the PC (such as plasma treatment or primer coating) to enhance adhesion. In recent years, modified TPE materials have emerged that can bond directly to PC without pretreatment, further simplifying the process. Additionally, the formulation design of TPE materials—including the molecular weight distribution of the SEBS base, plasticizer ratio, and compatibilizer addition—directly affects the overmolding results.

V. Sealing Performance Optimization and Failure Analysis

Even the best-designed swim goggle gaskets, made from optimal materials and manufactured with the finest processes, still face a series of challenges in real-world use. Systematic performance optimization and failure analysis are necessary to ensure long-term product reliability.

5.1 Factors Affecting Sealing Performance

The sealing performance of swim goggles is primarily influenced by the interplay of the following factors:

Facial contour adaptability: There are significant differences among individuals in nasal bridge height, eye socket depth, and cheekbone position. Whether the shape design of the gasket is based on sufficient ergonomic research directly determines its adaptability to different face shapes.
Distribution of strap tension: The pressure applied by the goggle strap is transmitted through the frame to the gasket. The uniformity of pressure distribution affects sealing quality. Skewed or uneven tension can cause localized stress concentration or sealing blind spots.
Stability under dynamic conditions: During swimming, dynamic factors such as changes in water pressure, impact acceleration from head movements, and water surface slapping constantly alter the force balance between the gasket and the face. Sealing performance under static test conditions does not equal performance under dynamic conditions.

5.2 Aging Failure Modes and Mechanisms

Aging failure of the gasket is a core constraint determining the service life of swim goggles. It mainly manifests in the following modes:

Elasticity degradation of the material: After long-term use, TPE and silicone materials undergo stress relaxation and a decrease in elastic modulus due to molecular chain breakage or changes in crosslinking density, resulting in a weakened initial deformation recovery force of the sealing ring, which can no longer maintain a tight fit.
Chemical corrosion and degradation: Repeated attack by pool disinfectants (chlorine-containing compounds) accelerates the chemical aging of gasket materials, causing surface roughening, initiation of micro-cracks, and even material embrittlement.
UV aging: In outdoor swimming scenarios, ultraviolet radiation induces photo-oxidative degradation of polymer materials, causing the gasket to become hard, brittle, and even discolored.

5.3 Standardized Test Methods

In response to the above performance requirements, the industry has established a relatively comprehensive system of test standards. The international standard ISO 18527-3 covers leakage testing, compression testing, water seal testing, and strap slip resistance for swim goggles. The domestic standard QB/T 4734-2023 specifies the specific method for sealing testing—simulating a water depth of 2 meters of pressure for 10 minutes to observe leakage. The negative pressure test method, as a core means of sealing performance inspection, involves wearing the goggles on a standard headform, sealing the exhaust valve, and maintaining a specified negative pressure for a set period to evaluate air leakage or water ingress. These standardized test methods provide a reliable technical basis for product development and quality inspection.

VI. Industry Development Trends and Outlook

The evolution of swim goggle gasket fitting technology clearly points to several main directions: moving toward ergonomic coupling with higher sealing efficiency and lower compression force, expanding toward smarter and more personalized material systems, and optimizing for full-life-cycle reliability.

The trends toward standardization and intelligence cannot be ignored. With the continuous refinement of standards such as ISO 18527-3 and QB/T 4734-2023, the design verification and quality control of gasket fitting technology have gradually transitioned from subjective experience to objective quantitative analysis. In the future, by combining large-scale 3D facial scan data with finite element simulation analysis, the shape and hardness zoning design of swim goggle gaskets will hopefully achieve more precise personalized customization.

The integration and innovation of materials science are also worth attention. TPE materials are iterating toward higher tensile recovery and stronger overmolding adhesion; meanwhile, silicone processing is evolving toward injection molding and automation. The performance boundaries of the two materials are gradually converging. At the same time, exploration of new materials such as degradable bio-based materials and specialty elastomers with enhanced chlorine resistance is also gradually unfolding.

Furthermore, the development of new overmolding processes will further improve product manufacturing consistency. Vertical two-color overmolding molds and their automation have already set a benchmark for the industry. The next breakthrough may lie in a closed-loop manufacturing system featuring multi-cavity high-speed precision injection molding and fully integrated online quality inspection, leading to truly unmanned smart factories.

VII. Conclusion

Swim goggle gasket fitting technology may appear to be a minor "trim" process science, but it profoundly reflects the convergence and integration of materials science, mechanical design, precision manufacturing, and human factors engineering. From simple curved bends to humanized structures with buffer space, from step-by-step injection molding to integrated vertical two-color overmolding, from a single silicone option to parallel TPE/silicone material pathways—each technological iteration seeks a new balance among tightness and looseness, sealing and comfort, cost and performance. Understanding and mastering the evolutionary logic of this technology is not only a professional commitment to protecting the user's "underwater eyes" for those engaged in swim goggle product development, manufacturing, and quality control, but also an inevitable path for driving the industry from experience-driven toward engineering-science-driven progress.

Wave China is a swimming goggles manufacturer. If you are interested in swimming goggles, please contact us.