What is the "truly suitable rubber strap" based on material properties?

The strap material has a major impact on the practicality of a watch, especially in the summer when you tend to sweat a lot, or in active situations such as sports and marine sports.

Among them, rubber straps are waterproof, lightweight, and durable, making them a standard choice for divers' watches and sports watches.

However, the term "rubber" is not a uniform material. The two main types of rubber used in watches are as follows:

- Urethane rubber

・Silicon rubber

Although they may look similar, the materials have very different molecular structures, durability, fit, and aging characteristics.
In this article, we will delve deeper into the properties of each material from a watch enthusiast's perspective.

Urethane rubber

Functional materials optimized for practical watches

Urethane rubber is a polyurethane-based thermoplastic elastomer (TPU).
It is an extremely practical material that combines the elasticity of rubber with the strength of plastic.

Since the 1970s, adoption of urethane straps has rapidly increased with the spread of diver's watches. In particular, the wavy urethane straps used in Seiko's diver's watches are symbolic of this trend.

Physical properties of urethane

The greatest feature of urethane is its high mechanical strength.

-High tensile strength

-High tear strength

High wear resistance

High shape retention ability

In other words, it is less likely to break even when subjected to strong forces, making it suitable for harsh environments.

This is also the reason why urethane has been used in watches for professional divers.

In addition, urethane has a moderate rigidity that helps the strap maintain its shape and can firmly support even heavy watches.

The benefits of urethane

High durability and structural strength

It has extremely high tear resistance among watch straps.
It pairs perfectly with heavy diver's watches and tool watches.

Oil and chemical resistance

It is relatively resistant not only to seawater but also to oil and chemicals, making it suitable for professional use.

Thin yet strong

Due to its high strength, it can ensure sufficient durability even though it is thin.

Urethane's greatest weakness - hydrolysis

The biggest drawback of urethane is its hydrolysis.

This is a phenomenon in which the molecular structure breaks down as it reacts with moisture in the air.

As a result,

・Hardening

・Cracks

- Surface collapse

occurs.

This process occurs regardless of frequency of use, so deterioration will occur even if the product is unused.

The average lifespan is about 2 to 5 years.

In other words, urethane straps are a material designed with the assumption that they will be a consumable item.

Silicone Rubber

Modern materials for comfort and stability

Silicone rubber is a polymer compound whose main skeleton is silicon and oxygen.

This structure is extremely stable and the material is extremely resistant to chemical degradation.

It is known as a highly biocompatible material, so much so that it is used in medical devices and artificial organs.

The greatest feature of silicone - It is resistant to deterioration over time

This is the biggest difference from urethane.

Silicone does not undergo hydrolysis.

In other words,

- Maintains softness for a long time

・Hard to harden

・Crack resistant

It has the following characteristics.

This material is designed for long-term use.

The benefits of silicone

Unparalleled flexibility

The material is very soft and conforms to the wrist well.

In terms of fit, it is superior to urethane.

Resistant to temperature changes

Silicone remains flexible over a wide temperature range.

・Hard to harden even at low temperatures

- Resistant to deterioration even at high temperatures

Also suitable for polar environments and outdoor use.

Less deterioration over time

Maintains performance and appearance for a long time.

Silicon's weakness: low structural strength

Silicon is soft, but

・Tear strength

- Wear resistance

However, it has the disadvantage that its strength is lower than that of urethane.

In addition, the surface is sticky,

・Dust easily accumulates

- Large friction with shirt sleeves

It has the following characteristics:

Watches that are suitable for urethane

・Full-scale diver's watch ・Large case ・Heavyweight watch ・Tool watch

The reason is,

・High strength

・Shape stability

・Structural support capacity

is.

Urethane is still widely used for professional purposes today.

Watches suitable for silicone

Lightweight sports watches, everyday watches, smart watches, and watches that prioritize comfort.

The reason is,

・High wearing comfort

・Long-term stability

is.

The difference you can feel - Coefficient of surface friction

This is a bit of a nerdy point, but it's important.

Urethane has a low coefficient of friction and is smooth.

Silicone has a high coefficient of friction and feels slightly sticky.

This is,

・Fitness

・Easy to put on and take off

・Compatibility with sleeves

affects.

Some luxury watch brands have developed their own rubber with adjusted friction characteristics.

conclusion

It's not the quality of the material, but the difference in use

Urethane and silicone are not superior or inferior in any way, but have different uses.

Who is urethane suitable for?

・Use a full-fledged diver's watch ・Prioritize durability ・Use as a tool watch

Who is silicone suitable for?

・Place emphasis on comfort ・Want to use for a long time ・Mainly for everyday use

The watch is complete with a strap

The performance of a watch is not determined solely by its movement and case.

The strap is also part of the watch.

By understanding the differences in materials, you can even see the watch's original design philosophy.

Choosing a rubber strap isn't just a matter of appearance.
It is an important factor that determines how you use your watch.

CONTÉVANOU, an authorized watch and jewelry dealer

〒151-0053
Nishisando Terrace E1, 28-7 Yoyogi 4-chome, Shibuya-ku, Tokyo

[MAIL]

info@CONTÉVANOU.com

[TEL]

03-3299-8008

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Approximately a 15-minute walk from Exit 6 of Shinjuku Station. Approximately an 8-minute walk from the East Exit of Sangubashi Station. From Shibuya Station, take the Keio Bus bound for Shinjuku Station West Exit. Get off at the Yoyogi-sanchome bus stop and walk for approximately 4 minutes. There is a paid parking lot nearby.