What Is IPX? SEKISUI Technologies for Achieving Waterproof Performance
2026-09-25
Understand the fundamentals of impact resistance and common evaluation methods. Discover SEKISUI's material solutions that enhance the durability and protection of electronic devices.
"IPX" is a waterproof rating commonly listed in the specifications of smartphones and electronic devices.
While IPX ratings indicate the waterproof performance of a finished product, achieving the required performance depends not only on product design but also on selecting the right materials.
As electronic devices become increasingly compact and lightweight, manufacturers are challenged to deliver high levels of waterproof protection within limited installation space.
This article explains the fundamentals of IPX ratings and introduces SEKISUI's material solutions that contribute to waterproof design and performance.
Contents
What Is IPX?
IPX is a type of protection rating within the IP (International Protection) Code that indicates the level of waterproof performance.
The number following "IPX" represents the waterproof rating level. In general, the higher the number, the greater the level of waterproof protection under more demanding test conditions.
IPX Rating Classifications
IPX ratings are classified from 0 to 8 according to the waterproof performance test conditions.
The waterproof protection provided by each rating is shown below.
| IPX0 | Not protected |
| IPX1 | Protected against vertically falling water droplets |
| IPX2 | Protected against falling water droplets when tilted up to 15° |
| IPX3 | Protected against spraying water |
| IPX4 | Protected against splashing water from any direction |
| IPX5 | Protected against water jets from any direction |
| IPX6 | Protected against powerful water jets from any direction |
| IPX7 | Protected against temporary immersion in water |
| IPX8 | Protected against continuous immersion in water |
In general, IPX1 to IPX4 indicate protection against water droplets and splashing water, IPX5 to IPX6 indicate protection against water jets, and IPX7 to IPX8 indicate protection against water immersion.
It is important to select the appropriate level of waterproof performance based on the intended operating environment. The highest rating is not always necessary; instead, the most suitable rating should be chosen according to the expected application and usage conditions.
In addition, IPX testing is generally conducted using fresh water at room temperature. As a result, performance against hot water, chlorinated water, seawater, and similar environments is typically not guaranteed. If use in such environments is anticipated, additional testing and evaluation may be required.
SEKISUI Solutions for Waterproof Performance
How is waterproof performance achieved through material technology?
In waterproof design for electronic devices, high waterproof performance is achieved through a combination of primary waterproofing, which prevents water from entering the device, and secondary waterproofing, which protects critical components in the event that water does penetrate the enclosure.
SEKISUI offers a wide range of materials that support waterproof design, including foam tapes and adhesives for primary waterproofing, as well as closed-cell foams for secondary waterproofing.
The following sections introduce Closed-cell Foam XLIM™, which features excellent waterproof performance through its closed-cell structure; Waterproof/Shock-Absorbing Foam Tape 5200 Series, which combines waterproofing and shock absorption; and UV + Moisture-Curing Flexible Adhesive Photolec™ B, which offers resistance to sweat and chemicals required for applications such as wearable devices.
SEKISUI's Closed-Cell Foam Technology for Waterproof Performance
The crosslinked polyolefin foam used as the base material for Closed-cell Foam XLIM™ features a unique closed-cell structure in which individual cells are not interconnected.
This structure makes it highly resistant to the passage of water and heat, enabling excellent waterproof performance.
Another key feature of the closed-cell structure is its low water absorption. The figure below compares the cross-sectional structure and water absorption rate of the product with those of a conventional urethane foam.
| Material | Water Absorption Rate | Cell Cross-Section |
|---|---|---|
| XLIM™ WL05 | ≤0.01 |  |
| Urethane Foam 0.5t | 14.9 |  |
Because the material is highly resistant to water penetration, it can provide excellent waterproof performance even at very thin thicknesses. This makes it well suited for compact and thin electronic devices, where high waterproof performance is required within limited installation space.
Achieving IPX5 Equivalent Performance with Single-Sided Bonding and IPX8 Equivalent Performance with Double-Sided Bonding
Closed-cell Foam XLIM™ offers excellent flexibility and conforms well to surface irregularities and warpage between components. By reducing gaps caused by uneven surfaces or distortion, it helps minimize potential pathways for water ingress.
The waterproof performance that can be achieved with the closed-cell foam structure of XLIM™ is:
・ IPX5-equivalent protection with single-sided adhesive bonding
・ IPX8-equivalent protection with double-sided adhesive bonding
Waterproof/Shock-Absorbing Foam Tape with IPX8-Equivalent Waterproof Performance
SEKISUI's Waterproof/Shock-Absorbing Foam Tape 5200 Series combines closed-cell foam and adhesive technology to achieve both excellent waterproof performance and secure fixation.
The foam conforms to uneven surfaces and component warpage, reducing gap formation, while the highly cohesive adhesive provides strong adhesion to substrates, helping to prevent water ingress.
Another key feature of the adhesive used in the Foam Tape 5200 Series is its ability to maintain tack while providing the high strength required for waterproof applications. In general, improving waterproof performance requires a harder adhesive formulation; however, this often results in reduced tack and poorer handling during assembly. SEKISUI's proprietary adhesive formulation technology achieves both, delivering excellent waterproof performance while maintaining ease of application.
SEKISUI's Foam Tape 5200 Series combines IPX8-equivalent waterproof performance with shock-absorbing properties, making it ideal for waterproofing and protection applications in electronic devices such as smartphones.
Photolec™ B: An Adhesive Combining Sweat and Chemical Resistance
SEKISUI's UV + Moisture-Curing Flexible Adhesive Photolec™ B combines flexibility with excellent adhesion. In addition to bonding components together, it helps prevent water ingress and contributes to improved waterproof performance.
When using a conventional adhesive for waterproof sealing, it can be difficult to control and maintain adhesive thickness because the adhesive is applied in liquid form. As a result, there may be areas where the adhesive does not sufficiently fill gaps, potentially leading to water leakage.
Photolec™ B can be brought to a semi-cured (B-stage) state by UV irradiation prior to assembly. This allows the adhesive to maintain a controlled thickness despite being an adhesive, enabling stable waterproof performance.
In actual waterproof testing, IPX8-level waterproof performance has been confirmed not only for PC-to-PC bonding, but also for bonding between dissimilar materials such as PC and glass, and PC and aluminum.
In wearable devices in particular, not only waterproof performance but also resistance to sweat and chemicals is required. SEKISUI's UV + Moisture-Curing Flexible Adhesive Photolec™ B offers excellent sweat and chemical resistance, making it suitable for applications that demand high reliability, such as wearable devices.
Product Inquiries
As devices continue to become smaller and thinner, there are increasing opportunities for SEKISUI's technologies to add value. If you are looking to achieve high waterproof performance within limited space, we encourage you to consider SEKISUI's products.
For product details, purchasing information, samples, or other inquiries, please feel free to contact us using the inquiry form below.
