The Secret Weapon of High-Performance TPU Materials: How TPU Yellowing Resistant Enhances UV Resistance
In modern industry and daily life, thermoplastic polyurethane (TPU) has become an indispensable high-performance material. It is known for its excellent elasticity, wear resistance and chemical resistance, and is widely used in shoe materials, films, wires and cables, and medical equipment. However, when the TPU is exposed to sunlight, UV radiation will trigger changes in its molecular structure, causing the material to turn yellow, which will affect its appearance and performance. To solve this problem, scientists developed a secret weapon – TPU yellowing agent. This additive can not only effectively delay the yellowing process of TPU, but also significantly enhance its anti-ultraviolet ability, allowing TPU materials to maintain excellent performance in various harsh environments.
This article will conduct in-depth discussion on the mechanism, types and application methods of TPU yellowing agent, and compare and analyze relevant domestic and foreign literature to reveal its specific contribution to the improvement of TPU performance. At the same time, we will use easy-to-understand language combined with funny metaphors to help readers better understand this complex technical field. The article will also list the product parameters of common TPU yellowing agents in detail through tables to provide reference for practical applications. Let us unveil the mystery of TPU yellowing agent and explore how it becomes the “guardian” of high-performance TPU materials.
Basic characteristics and yellowing problems of TPU materials
What is TPU?
TPU, full name is Thermoplastic Polyurethane elastomer (Thermoplastic Polyurethane), is a polymer material produced by the reaction of polyisocyanate and polyol. Its molecular structure contains hard and soft segments. This unique two-phase separation structure gives TPU a series of excellent performance:
- High elasticity: TPU has extremely high tensile strength and elongation at break, and can withstand repeated deformation without damage.
- Abrasion Resistance: Its surface hardness and wear resistance make it an ideal choice for sports soles, rollers and other fields.
- Chemical resistance: TPU shows good resistance to most solvents, greases and chemicals.
- Flexibility: From soft films to hard sheets, TPUs can achieve different hardness ranges by adjusting the formulation.
However, the TPU is not perfect. When exposed to ultraviolet light for a long time, its molecular chains will undergo oxidation and degradation, causing the material to gradually turn yellow, a phenomenon called “yellowing”. Yellowing not only affects the appearance of the TPU, but may also weaken its mechanical properties and shorten its service life.life.
The reasons for yellowing and its impact on TPU
The yellowing of TPU is mainly caused by the following two factors:
-
Ultraviolet radiation
High-energy photons in ultraviolet light can destroy chemical bonds in TPU molecules, especially aromatic isocyanate residue groups, thereby triggering a radical chain reaction. These free radicals further combine with oxygen to form peroxides and other colored substances, which eventually leads to yellowing of the material.
-
Oxidation
Under the action of ultraviolet rays, some components in the TPU (such as catalyst residues or insufficient antioxidants) may undergo oxidation reactions, producing carbonyl compounds or other yellow pigments, further aggravating the yellowing phenomenon.
The impact of yellowing on TPU is multifaceted:
- Appearance deterioration: The originally transparent or light-colored TPU becomes turbid or even yellow, losing its original aesthetic.
- Decreased mechanical properties: Yellowing is usually accompanied by breaking of the molecular chain, resulting in a decrease in the tensile strength and toughness of the material.
- Shortening service life: Long-term yellowing will cause the TPU material to age ahead of time and cannot meet the usage requirements.
Therefore, solving the yellowing problem of TPU has become the key to improving its performance and extending its service life.
Mechanism of action of TPU yellowing agent
In order to deal with the yellowing problem of TPU, scientists have developed a special type of additive – TPU yellowing agent. This type of substance inhibits the damage to the TPU molecular structure by ultraviolet rays and oxidation in various ways, thereby delaying or preventing the occurrence of yellowing.
Absorb UV rays
One of the common functions of TPU yellowing agents is to absorb ultraviolet rays. They are like an invisible “sunscreen” that intercepts and converts ultraviolet energy to prevent it from acting directly on TPU molecules. Specifically, these yellowing agents contain specific chemical groups that can absorb high-energy photons in ultraviolet light and convert them into thermal or low-energy photons to release them, thereby avoiding the damage of ultraviolet light to TPU molecules.
For example, benzotriazole compounds are highly efficient ultraviolet absorbers. They interact with UV through a ?-electron conjugation system, converting harmful short-wave UV into harmless long-wave light or thermal energy. This conversion process is similar to turning a sharp knife into a soft noodles, allowing UV light to no longer cause damage to TPU molecules.
Inhibition of oxidation reaction
ExceptTo absorb ultraviolet rays, TPU yellowing agents also protect the material by inhibiting oxidation reactions. Oxidation reaction is one of the important reasons for TPU yellowing, and the antioxidant components in yellow-resistant agents can capture free radicals and prevent them from chain reactions with other molecules.
Imagine that free radicals are like a naughty kid running around inside the material and knocking down other molecules. Antioxidants are like a patient guardian, catching these children in time and calming them down, thus avoiding more molecules being destroyed. This mechanism of action ensures the integrity of the TPU molecular chain and reduces the possibility of yellowing.
Providing shielding effect
Some TPU yellowing agents also have the function of physical shielding. They can form a dense protective film on the surface of the TPU to block the direct penetration of ultraviolet rays. This film is like wearing a protective suit for the TPU. Even if the external environment is filled with ultraviolet radiation, the material itself can still remain stable.
In addition, this shielding effect can reduce the chance of contact between oxygen and TPU molecules and further reduce the probability of oxidation reaction. In this way, TPU yellowing agent not only solves the ultraviolet problem, but also takes into account the needs of antioxidant, providing all-round protection for TPU materials.
Types and characteristics of common TPU yellowing agents
Depending on the mechanism of action, TPU yellowing agents can be divided into three categories: ultraviolet absorbers, antioxidants and composite yellowing agents. Each type has its own unique advantages and applicable scenarios. The following is their specific introduction and comparison of their characteristics.
1. UV absorber
Ultraviolet absorbers are a type of additives that have been used for TPU yellowing resistance treatment. They effectively reduce the damage to TPU molecules by absorbing ultraviolet energy and converting it into harmless forms. Common UV absorbers include benzotriazoles, benzophenones and salicylate compounds.
| Category |
Features |
Representative Compound |
| Benzotriazoles |
Efficient absorption of medium and short wave ultraviolet rays, good stability, and difficult to migrate |
Tinuvin P, Chimassorb 81 |
| Benzophenone |
Wide absorption range, low cost, but easy to migrate |
Uvinul M40, Tinuvin 326 |
| Salicylate |
It has a good absorption effect on long-wave ultraviolet rays and is often used in transparent TPU products |
Parsol HS |
Benzotriazoles
Benzotriazole compounds are highly favored for their high efficiency and stability. They can continuously absorb ultraviolet rays for a long time and are not easy to migrate out of TPU substrates. They are suitable for TPU products that are used outdoors for a long time.
Benzophenone
Benzophenone ultraviolet absorbers are relatively cheap and are suitable for application scenarios with limited budgets. However, due to its strong mobility, it may lead to precipitation on the surface of TPU products, so it should be used with caution.
Salicylates
Salicylate compounds have a good absorption effect on long-wave UV rays and are especially suitable for TPU products that require transparency, such as optical films and eyeglasses.
2. Antioxidants
Antioxidants effectively prevent the TPU from yellowing due to oxidation by capturing free radicals and interrupting the oxidation reaction chain. They are divided into two categories: primary antioxidants and secondary antioxidants.
| Category |
Function |
Representative Compound |
| Main Antioxidant |
Catch free radicals and terminate the oxidation reaction chain |
Irganox 1076, Irganox 1010 |
| Supplemental Antioxidants |
Decompose hydroperoxide and work in coordination with the main antioxidant |
Irgafos 168 |
Main Antioxidant
Main antioxidants such as Irganox 1076 and Irganox 1010 are able to quickly capture free radicals, preventing them from triggering further oxidation reactions. This type of compound usually has high thermal stability and long-term efficacy, and is suitable for TPU products under high temperature processing conditions.
Supplemental Antioxidants
Supply antioxidants such as Irgafos 168 focus on decomposing hydroperoxides, thereby reducing the burden on the main antioxidants. When used in combination, better antioxidant effects can be achieved.
3. Compound yellowing agent
Composite yellowing agent combines the advantages of UV absorbers and antioxidants, and can cope with the dual threats of UV and oxidation at the same time. This type of product is usually optimized for proportional design and is suitable for complex usage environments.
| Category |
Features |
Representative Compound |
| Composite |
It has both ultraviolet absorption and antioxidant functions, and has excellent comprehensive performance |
Chimassorb 944, Tinuvin 123 |
Comprehensive Advantages
Composite yellowing agents such as Chimassorb 944 and Tinuvin 123 can provide comprehensive protection for TPUs, especially suitable for applications requiring long-term weather resistance, such as automotive interior parts and building membranes.
Comparison of current domestic and foreign research status and technology
The research and development of TPU yellowing agents has always been an important topic in the field of polymer materials worldwide. Scientists from various countries have invested a lot of resources in this field to continuously improve the performance of additives and expand their application scope. The following is a comparative analysis of the current domestic and foreign research status and technical level.
Progress in foreign research
European and American countries started early in the research of TPU yellowing agents and were in a leading position in the technology level. Well-known companies such as BASF in Switzerland, Clariant in Germany and Celanese in the United States have launched a variety of high-efficiency yellowing agent products. For example, BASF’s Tinuvin series UV absorbers and Irganox series antioxidants have dominated the international market.
The characteristics of foreign research include:
- Highly innovative: Focus on developing new functional yellow-resistant agents, such as biodegradable environmentally friendly products.
- Widely used: To meet the needs of different industries, customized solutions are launched, covering multiple fields from consumer electronics to aerospace.
- Excellent performance: Through molecular structure optimization, the absorption efficiency and stability of the resistant yellowing agent are significantly improved.
Domestic research status
In recent years, China has made significant progress in research on TPU yelitising agents. Domestic scientific research institutions and enterprises have gradually mastered core technologies and production processes, and some products have reached the international advanced level. For example, Zhejiang Wankai New Materials Co., Ltd. and Jiangsu Ruihua Chemical Co., Ltd. have successively launched independently developed high-performance yellowing agents.
The advantages of domestic research are:
- Cost Control: By optimizing formulas and processes, production costs are greatly reduced and market competitiveness is improved.
- Local Service: Understand the local market demands and respond quickly to customer feedback.Provide more targeted products.
- Green and Environmental Protection: Actively respond to national policies and vigorously develop low-toxic and harmless environmentally friendly yellowing agents.
Technical gap and development direction
Although domestic research has made great progress, there are still some shortcomings, which are mainly reflected in the following aspects:
- Insufficient research on basic theory: Compared with foreign countries, my country’s research on the design and mechanism of molecular structure of yellowing agents still needs to be strengthened.
- High-end product research and development lag: Some high-end yellowing agents still rely on imports, especially in special fields such as aerospace and medical devices.
- Improper standardization system: The lack of unified testing standards and evaluation methods affects the stability of product quality.
The future development direction should focus on the following aspects:
- Strengthen basic research: In-depth exploration of the interaction mechanism between yellowing agents and TPU materials, laying a theoretical foundation for new product development.
- Promote technological innovation: Use nanotechnology and smart material concepts to develop new yellowing agents with higher efficiency and versatility.
- Improve the standard system: Establish scientific and reasonable testing methods and evaluation indicators to promote the comprehensive improvement of product quality.
Application methods and precautions for TPU yellowing agent
The correct use of TPU yellowing agent is the key to fully exerting its effectiveness. The following are some practical suggestions and precautions to help users achieve good results in actual operation.
Select to add proportions
The amount of yellowing agent added should be adjusted according to the specific use and use environment of the TPU material. Generally speaking, the recommended addition ratio is 0.1%~1.0% (mass fraction). For TPU products that are used outdoors for a long time, the added amount can be appropriately increased; for products that are used indoors for a short period of time, the amount can be reduced to reduce costs.
| User scenarios |
Recommended addition ratio (mass fraction) |
Precautions |
| High requirements for outdoor weather resistance |
0.5%~1.0% |
Ensure that the yellowing agent is evenly distributed |
| General use of indoors |
0.1%~0.3% |
Avoid excessive addition and cause physical performance degradation |
| Special for medical devices |
0.3%~0.5% |
Complied with relevant regulations |
Sticks of stirring and mixing
The degree of dispersion of yellowing agent in TPU substrate directly affects its effect. Therefore, the following points should be paid attention to during the mixing process:
- Full stir: Use high-speed stirring equipment to ensure that the yellowing agent is evenly distributed in the TPU particles.
- Temperature Control: Avoid decomposition or failure of yellowing agents due to excessive high temperatures.
- Time Management: Arrange the mixing time reasonably to ensure dispersion effect without wasting energy.
Storage and Transport Suggestions
When resistant yellowing agent is stored and transported, it should be protected from moisture, light and sealed to avoid affecting its performance. Especially ultraviolet absorbers, if exposed to strong light for a long time, may degrade themselves and lose their efficacy.
Summary and Outlook
TPU yellowing agents, as the “secret weapon” of high-performance TPU materials, play an irreplaceable role in resisting ultraviolet rays and delaying yellowing. By absorbing UV rays, inhibiting oxidation reactions and providing shielding effects, these additives provide TPU materials with full protection, allowing them to maintain excellent performance in various harsh environments.
With the advancement of technology and the continuous changes in market demand, the research and application of TPU yellowing agents will also usher in new development opportunities. In the future, we look forward to seeing more efficient, environmentally friendly and multifunctional new yellowing agents coming out, injecting stronger momentum into the widespread application of TPU materials. As a song sings: “Let every dream blossom.” I believe that with the efforts of scientists, the future of TPU materials will surely be even more brilliant!
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