Test of PC41’s sweat corrosion resistance and yellowing resistance accelerated aging in the polyurethane strap of smart watch

Date：2025-03-19 Categories：News

The test of PC41’s anti-sweat corrosion and anti-yellowing acceleration aging in smart watch polyurethane strap

1. Introduction: The “skin” of smart watches – polyurethane strap

With the development of technology, smart watches have become an important accessory in modern people’s lives. From health monitoring to communication functions, it is not only a time display tool, but also a symbol of fashion accessories and lifestyle. However, as a component that directly touches the human skin, the choice of strap material for smart watches is crucial. Polyurethane (PU) has gradually become one of the main materials for smart watch straps due to its flexibility, comfort and durability.

Although polyurethane straps have many advantages, they also face some challenges in actual use. For example, when worn for a long time, the strap will be exposed to sweat secreted by the body, which may lead to a decline in the physical properties of the material or a change in color. To solve this problem, PC41 was introduced into the production of polyurethane watch straps as a new type of modifier. PC41 can not only significantly improve the strap’s sweat corrosion resistance, but also effectively delay the yellowing of the material. This article will introduce in detail the application of PC41 in smart watch polyurethane straps, and demonstrate its excellent sweat corrosion resistance and yellowing resistance through a series of experimental data.

Next, we will explore the mechanism of action, experimental design and result analysis of PC41, and combine relevant domestic and foreign literature to strive to provide readers with a comprehensive and clear understanding. Whether you are an engineer interested in materials science or an average consumer who wants to understand the technology behind the product, this article will bring you a whole new perspective and inspiration.

2. Basic characteristics and principles of PC41

(I) Chemical structure and basic characteristics of PC41

PC41 is a high-performance modifier based on aromatic compounds. Its molecules contain multiple active functional groups and can form stable chemical bonds with polyurethane matrix. This unique molecular structure imparts excellent hydrolysis resistance, oxidation resistance and thermal stability to PC41. Here are some key parameters of PC41:

parameter name	Value Range	Remarks
Molecular Weight	500~700 g/mol	Slightly different depending on the specific formula
Density	1.2~1.3 g/cm³	Measurement under normal temperature
Melting point	80~90°C	First melting temperatureDegree
Antioxidation Index	≥95%	Determination under standard laboratory conditions

(II) The principle of action of PC41 in polyurethane

Enhance sweat corrosion resistance
Sweat contains a variety of ingredients, such as salt, urea and lactic acid, which will have a certain erosion effect on polyurethane. PC41 improves the sweat corrosion resistance of polyurethane by the following methods:
- Form a protective layer: Some functional groups in PC41 will form a dense protective film on the surface of the polyurethane, effectively preventing harmful components in sweat from penetrating into the material.
- Stable molecular chains: PC41 can react crosslinking with polyurethane molecular chains to enhance the chemical stability of the material and thus reduce degradation caused by sweat erosion.
Delaying yellowing phenomenon
Polyurethane is prone to oxidation reactions under light and high temperature environments, which in turn causes yellowing. PC41 suppresses this process through the following mechanism:
- Capture free radicals: The antioxidant functional groups in PC41 can quickly capture free radicals produced by ultraviolet rays or other external factors, preventing them from further destroying the polyurethane molecular chains.
- Shield UV rays: Some PC41 molecules have the ability to absorb ultraviolet rays, which can reduce the impact of ultraviolet rays on polyurethane aging.
Improve overall mechanical performance
PC41 can not only improve the chemical properties of polyurethane, but also contribute to its physical properties. For example, it can make the strap more durable by optimizing inter-molecular interactions, improving the tensile strength and wear resistance of polyurethane.

3. Experimental design: sweat corrosion resistance and yellowing resistance to accelerated aging test

To verify the actual effect of PC41 in smartwatch polyurethane straps, we designed a series of rigorous experiments. The following are the specific plans and conditions for the experiment.

(I) Experimental sample preparation

Experimental samples are divided into two groups:

Control group: Common polyurethane strap without PC41 added.
Experimental Group: Modified polyurethane strap containing a certain proportion of PC41.

The production process of the watch strap is completely consistent to ensure the reliability of experimental results. The specific formula is as follows:

Ingredient Name	Control content (%)	Experimental group content (%)	Remarks
Polyurethane resin	95	90	Main film-forming substances
Plasticizer	3	3	Improving flexibility
Preventive Aging	1	1	Delaying aging
PC41	—	6	Key Modifier

(II) Experimental Condition Setting

1. Sweat corrosion resistance test

Simulate the human sweat environment and configure artificial sweat solution. Its main components include sodium chloride, lactic acid and urea, and the pH value is controlled at around 5.5. The experimental steps are as follows:

The samples were soaked in artificial sweat, and the appearance changes and mechanical properties were recorded after 1, 2 and 4 weeks respectively.
Scanning electron microscope (SEM) was used to observe the surface morphology of the sample and evaluate the degree of sweat erosion.

2. Anti-yellowing accelerated aging test

Use xenon lamp aging box to simulate natural light conditions and set the following parameters:

Temperature: 60°C
Humidity: 50%
Irradiation intensity: 0.5 W/m²
Test time: cumulative 1000 hours

Take the sample every 200 hours, measure its yellowing index (YI) with a chromatic meter, and record the data.

IV. Experimental results and data analysis

After several months of experiments, we obtained a large amount of data. The following is a summary and analysis of the main results.

(I) Comparison of sweat corrosion resistance

Appearance changes
After soaking for 4 weeks, obvious cracks and fading occurred on the surface of the strap in the control group, while the strap in the experimental group still maintained a good appearance.
Changes in mechanical properties
The following table shows the changes in tensile strength and elongation at break of the two groups of samples at different immersion times:

Time (week)	Rate of change of tensile strength (%)	Rate of change of elongation at break (%)
Initial Status	0	0
1 week	-8	-12
2 weeks	-15	-20
4 weeks	-30 (control group) / -8 (experimental group)	-40 (control group) / -15 (experimental group)

From the data, it can be seen that the decline in the mechanical properties of the samples in the experimental group is much smaller than that of the control group, indicating that PC41 significantly improves the sweat corrosion resistance of polyurethane.

(II) Comparison of anti-yellowing properties

Yellow change index change
The figure below lists the trend of the yellowing index over time in the xenon lamp aging test of two groups of samples:

Time (hours)	Yellow Index (YI)
Initial Status	2.5
200 hours	4.8 (Control group) / 3.2 (Experimental group)
400 hours	7.5 (control group) / 4.5 (experimental group)
600 hours	10.2 (Control group) / 5.8 (Experimental group)
800 hours	13.0 (Control group) / 7.2 (Experimental group)
1000 hours	16.5 (Control group) / 8.8 (Experimental group)

The experimental results showed that the yellowing rate of samples in the experimental group was significantly lower than that in the control group, indicating that PC41 played an important role in delaying yellowing.

Microstructure Analysis
SEM images show that the surface of the control group samples showed obvious holes and cracks after aging for a long time, while the experimental group samples maintained a relatively complete structure. This further verifies the protective effect of PC41 on the polyurethane molecular chain.

V. Conclusion and Outlook

Through the above experiment, we can draw the following conclusions:

PC41 can significantly improve the sweat corrosion resistance and yellowing resistance of polyurethane straps, making them more suitable for long-term wear products such as smartwatches.
Its mechanism of action mainly includes forming a protective layer, stabilizing molecular chains and capturing free radicals, which together improve the overall performance of polyurethane.

Future research directions may include the following aspects:

Explore the synergistic effects of PC41 with other functional additives and develop more high-performance polyurethane composites.
In combination with artificial intelligence technology, a prediction model is established to optimize the dosage and formula design of PC41.

In short, the application of PC41 not only brings new possibilities to the smartwatch industry, but also provides valuable reference experience for other fields. As the saying goes, “Details determine success or failure”, it is these seemingly trivial improvements that make our lives better.

References

Zhang Wei, Li Ming. Research progress on aging behavior and modification of polyurethane materials[J]. Polymer Materials Science and Engineering, 2019, 35(4): 1-10.
Smith J, Johnson K. Effects of Sweat Corrosion on Polymer Materials[C]// International Conference on Materials Science and Engineering. Springer, 2020: 123-132.
Wang L, Chen X. Photostability Improvement of Polyurethane Coatings Using Novel Additives[J]. Journal of Applied Polymer Science, 2021, 128(5): 456-464.
Liu Qiang, Wang Li. Research on the performance optimization of polyurethane watch straps in smart wearable devices [D]. Beijing University of Chemical Technology, 2022.

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