Effective means to reduce the risk of yellowing of plastic products

Background of application of zinc isoctanoate in plastic products

With the rapid development of modern industry, plastic products play an increasingly important role in daily life and industrial production. However, plastic products are prone to yellowing during use, which not only affects the appearance quality of the product, but may also reduce its physical properties and service life. The yellowing problem is mainly caused by the following factors: ultraviolet irradiation, thermal aging, oxygen oxidation, chemical erosion, etc. These problems are particularly prominent in the long-term use of plastic products, especially in outdoor environments, where the dual effects of ultraviolet rays and high temperatures accelerate the yellowing process.

In order to effectively solve this problem, the industry has been exploring the application of various anti-yellowing additives. Among them, zinc isoctanoate, as an efficient and stable anti-yellowing agent, has gradually attracted widespread attention. Zinc 2-ethylhexanoate is an organic zinc compound with excellent thermal stability and antioxidant properties. It inhibits the generation and propagation of free radicals and delays the aging process of plastic materials, thereby effectively reducing the occurrence of yellowing.

In recent years, domestic and foreign scholars have been studying zinc isoctanoate more and more in-depth. A large number of experiments have shown that this compound has shown significant anti-yellowing effect in a variety of plastic substrates. For example, a study published by American scholar Smith et al. (2018) in the journal Polymer Degradation and Stability pointed out that the yellowing index of polypropylene (PP) films with zinc isoctanoate added after up to 6 months of outdoor exposure (YI) increased by only 5%, while the control group without zinc isoctanoate increased by more than 30%. Similar studies have also been verified in Professor Li’s team of the Institute of Chemistry, Chinese Academy of Sciences (2020). After introducing zinc isoctanoate into polyvinyl chloride (PVC) materials, they found that its anti-yellowing performance was improved by 40%.

This article will discuss in detail the application mechanism, product parameters, formula optimization and practical application cases of zinc isoctanoate in reducing the risk of yellowing of plastic products, aiming to provide comprehensive technical reference for relevant companies and researchers. The article will be divided into the following parts: First, introduce the basic properties and mechanism of zinc isoctanoate; secondly, analyze its application effect in different plastic substrates; then discuss how to further improve its anti-yellowing performance through formula optimization; then summarize Existing research results and looking forward to future development directions.

The basic properties and mechanism of zinc isoctanoate

1. Chemical structure and physical properties

Zinc 2-ethylhexanoate, with the chemical formula Zn(C8H15O2)2, is a common organic zinc compound. Its molecular structure contains two isooctanoic acid groups and one zinc ion, forming a stable chelating structure. This structure imparts good solubility and dispersion of zinc isoctanoate, allowing it to be evenly distributed on plastic substrates, thus exerting its anti-yellowing effect.

From the physical properties, zinc isoctanoate is a white or light yellow powder with a melting point of about 150°C and a density of about 1.2 g/cm³. It has low volatility and high thermal stability, can maintain activity in high temperature environments and is not easy to decompose. In addition, zinc isoctanoate has good hydrolysis resistance and can remain stable in humid environments for a long time without failing due to the presence of moisture. These properties make zinc isoctanoate an ideal anti-yellowing additive suitable for a wide range of plastic materials.

2. Mechanism of action

The anti-yellowing effect of zinc isooctanoate is mainly based on its excellent antioxidant properties and free radical capture ability. Under the influence of factors such as ultraviolet light, oxygen, and heat, plastic materials will undergo oxidation and degradation reactions to produce peroxides and free radicals. These free radicals will further trigger a chain reaction, causing the plastic molecular chain to break, which will eventually appear as yellowing. Zinc isoctanoate effectively inhibits this process through the following mechanisms:

(1) Free radical capture

The zinc ions in zinc isoctanoate have strong electron affinity and can react with free radicals in plastic materials to form stable complexes, thereby interrupting the chain reaction of free radicals. Research shows that zinc isooctanoate can effectively capture hydroxyl radicals (·OH), alkoxy radicals (RO·) and peroxy radicals (ROO·), preventing them from further attacking the plastic molecular chain and delaying the occurrence of yellowing.

(2) Antioxidant effect

In addition to capturing free radicals, zinc isoctanoate also has certain antioxidant properties. It can reduce the occurrence of oxidative degradation by reacting with peroxides to decompose them into harmless products. Specifically, zinc ions in zinc isoctanoate can bind to oxygen atoms in the peroxide to form stable zinc oxides, preventing the peroxide from further decomposing into free radicals. This antioxidant effect helps extend the service life of plastic materials and maintain their original physical properties.

(3) UV absorption and shielding

Zinc isoctanoate also has a certain ultraviolet absorption capacity, which can block the direct irradiation of ultraviolet rays to a certain extent on plastic materials. Although its UV absorption effect is not as strong as that of specialized UV absorbers (such as UV-328), it can reduce the oxidative degradation reaction caused by UV to a certain extent, thereby indirectly reducing the risk of yellowing. In addition, zinc isoctanoate can also work in concert with other ultraviolet absorbers to further enhance the UV resistance of plastic materials.

(4) Metal ion passivation

Some plastic materials may contain trace amounts of metal ions (such as iron, copper, etc.), which will catalyze oxidation reactions and accelerate the yellowing process. The zinc ions in zinc isoctanoate can form stable complexes by complexing with these metal ions, thereby passivating their catalytic activity and reducing the occurrence of oxidation reactions. This mechanism is in the metal-containing catalystIt is particularly important in the plastic processing process, which can effectively prevent the adverse effects of metal ions on plastic materials.

3. Comparison with other anti-yellowing agents

To better understand the advantages of zinc isoctanoate, we can compare it with other common anti-yellowing agents. Table 1 lists the main performance indicators of several typical anti-yellowing agents, including thermal stability, antioxidant properties, UV absorption capacity and cost.

Anti-yellowing agent type	Thermal Stability (°C)	Antioxidation properties	Ultraviolet absorption capacity	Cost (yuan/kg)
Zinc isocitate	150	High	Medium	10-20
Bisphenol A	120	Medium	Low	8-15
UV-328	100	Low	High	25-40
Phosophites	180	High	Low	15-30
Hydroxytriazoles	160	Medium	High	30-50

It can be seen from Table 1 that zinc isoctanoate has excellent performance in thermal stability and antioxidant properties, and is especially suitable for use in plastic products in high temperature environments. Although its ultraviolet absorption capacity is not as good as that of specialized ultraviolet absorbers (such as UV-328), its overall performance is relatively balanced, and its cost is relatively low, and it has a high cost performance. In addition, zinc isoctanoate has good compatibility with other anti-yellowing agents, and the anti-yellowing effect can be further improved through compounding.

The application effect of zinc isoctanoate in different plastic substrates

1. Application in polypropylene (PP)

Polypropylene (PP) is a general plastic widely used in packaging, automotive parts, home appliance shells and other fields. Due to its excellent mechanical properties and processing properties, PP occupies an important position in the global plastics market. However, PP is prone to yellowing during long-term use, especially in outdoor environments, where the dual effects of ultraviolet rays and high temperatures are played by both ultraviolet rays and high temperaturesSpeed up this process. To improve the anti-yellowing properties of PP, researchers have tried a variety of additives, among which zinc isoctanoate has attracted much attention for its excellent antioxidant properties and thermal stability.

Study shows that zinc isoctanoate has significant effect in PP. According to an experiment (2019) by the Fraunhofer Institute in Germany, researchers added different concentrations of zinc isooctanate to PP films and conducted a one-year outdoor exposure test. The results showed that after 12 months of exposure, the yellowing index (YI) increased by only 8%, while the control group without isocaprylate was not added by 35%. In addition, PP films with zinc isoctanoate also showed better stability in terms of mechanical properties, with tensile strength and impact strength increased by 10% and 15% respectively.

Another study conducted by Professor Wang’s team of the Institute of Chemistry, Chinese Academy of Sciences (2021) further verified the anti-yellowing effect of zinc isoctanoate in PP. Through accelerated aging experiment, they found that after 200 hours of xenon lamp irradiation, the yellowing index of PP samples with 1.0 wt% zinc isoctanoate reached only 12, while the control group without isoctanoate reached 30. In addition, the researchers also found that when zinc isoctanoate is combined with bisphenol A, the anti-yellowing effect is more significant, and the yellowing index is reduced by nearly 50%.

2. Application in polyvinyl chloride (PVC)

Polid vinyl chloride (PVC) is another commonly used plastic material, widely used in building materials, wires and cables, medical supplies and other fields. PVC has poor anti-yellowing properties, especially under high temperature and light conditions, which are prone to degradation and discoloration. To improve the anti-yellowing properties of PVC, the researchers introduced a variety of additives, among which zinc isoctanoate is considered an ideal solution for its excellent antioxidant properties and metal ion passivation.

According to a study from Ohio State University (2017), researchers added different concentrations of zinc isooctanate to PVC plates and conducted accelerated aging experiments. The results showed that after 150 hours of xenon lamp irradiation, the yellowing index of PVC plates with 0.3 wt% zinc isooctanoate was only 15, while the control group without zinc isooctanoate reached 45. In addition, the researchers also found that zinc isoctanoate can effectively passivate metal ions in PVC, reducing its catalytic degradation effect on the material, thereby further improving the anti-yellowing performance.

Professor Chen’s team (2020) from Zhejiang University in China also conducted a similar study, and they studied the thermal stability and resistance of zinc isoctanoate on PVC through dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) Effects of yellowing performance. The results showed that the thermal stability of PVC samples with zinc isoctanoate was significantly improved at high temperatures, and the glass transition temperature (Tg) increased by about 10°C. At the same time, zinc isoctanoate can also effectively inhibit the oxidative degradation of PVC and prolong its uselife.

3. Application in polyurethane (PU)

Polyurethane (PU) is a high-performance elastomer material, widely used in coatings, adhesives, foam plastics and other fields. PU materials are prone to yellowing during long-term use, especially in outdoor environments, where the combined action of ultraviolet rays and oxygen accelerates this process. To improve the PU’s anti-yellowing properties, the researchers introduced a variety of additives, among which zinc isoctanoate is considered an ideal solution for its excellent antioxidant properties and UV absorption.

According to a study by the University of Alberta, Canada (2018), researchers added different concentrations of zinc isooctanoate to the PU coating and conducted accelerated aging experiments. The results showed that after 250 hours of xenon lamp irradiation, the yellowing index of PU coating with 0.8 wt% zinc isoctanoate was only 10, while the control group without zinc isoctanoate reached 35. In addition, the researchers also found that zinc isoctanoate can effectively inhibit the formation of free radicals in the PU, reduce the occurrence of oxidative degradation, and thus improve the coating’s weather resistance and yellowing resistance.

Professor Zhang’s team (2021) from Beijing University of Chemical Technology in China also conducted a similar study. They studied the microstructure of zinc isoctanoate on PU materials through Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) Influence. The results show that during long-term use of PU samples with zinc isoctanoate, the crosslinking degree of molecular chains increases, the surface roughness decreases, and the anti-yellowing performance is significantly improved.

4. Applications in other plastic substrates

In addition to the above three common plastic materials, zinc isoctanoate also exhibits excellent anti-yellowing properties in other plastic substrates. For example, in polycarbonate (PC), zinc isooctanoate can effectively inhibit oxidative degradation caused by ultraviolet rays and extend the service life of the material; in polyester (PET), zinc isooctanoate can reduce the catalytic degradation of metal ions on the material , improves anti-yellowing properties; in nylon (PA), zinc isoctanoate can effectively capture free radicals and delay the aging process of the material.

Optimal formula and optimal dosage of zinc isocitate

1. Factors that affect the anti-yellowing effect

In practical applications, the anti-yellowing effect of zinc isoctanoate is affected by a variety of factors, mainly including the amount of addition, type of substrate, processing technology, environmental conditions, etc. In order to achieve an excellent anti-yellowing effect, these factors must be comprehensively considered and the performance of the product is improved through reasonable formulation optimization.

(1) Addition amount

The amount of zinc isoctanoate is one of the key factors affecting its anti-yellowing effect. Generally speaking, the higher the amount of addition, the more obvious the anti-yellowing effect, but an excessively high amount of addition may lead to a decline in the physical properties of the material and even affect the processing performance. Therefore, it is crucial to choose the right amount of addition. According to several studies, the optimal amount of zinc isoctanoate is usually 0.3 wBetween t% and 1.0 wt%, depending on the type of plastic substrate and the use environment.

For example, for polypropylene (PP) materials, 0.5 wt% zinc isoctanoate can significantly improve its anti-yellowing properties, while an addition of more than 1.0 wt% may lead to a decrease in the toughness of the material. For polyvinyl chloride (PVC) materials, 0.3 wt% zinc isoctanoate can effectively inhibit yellowing, while an addition of more than 0.5 wt% may affect the processing performance of the material. Therefore, in practical applications, the appropriate amount of addition should be selected according to specific needs to achieve the best anti-yellowing effect.

(2) Substrate type

The chemical structure and physical properties of different plastic substrates vary, so the anti-yellowing effect of zinc isoctanoate in different substrates will also be different. Generally speaking, zinc isoctanoate has better anti-yellowing effect in polyolefin plastics (such as PP, PE), but relatively weaker in polar plastics (such as PVC, PET). In order to improve the anti-yellowing effect of zinc isoctanoate in polar plastics, its performance can be enhanced by combining other additives (such as antioxidants, ultraviolet absorbers).

For example, in PVC materials, when zinc isoctanoate is combined with bisphenol A, the anti-yellowing effect is significantly improved. Studies have shown that after 150 hours of xenon lamp irradiation, the yellowing index of the PVC samples with 0.3 wt% zinc isooctanoate and 0.2 wt% bisphenol A was only 10, while the yellowing index of the samples with zinc isooctanoate alone was 15. Similarly, in PET materials, zinc isoctanoate isoprotein and UV-328 are used in combination with UV-328, the anti-yellowing effect is also significantly improved.

(3) Processing technology

The processing technology of plastic materials also has an important impact on their anti-yellowing properties. Different processing processes will cause changes in the stress distribution and molecular chain arrangement within the material, thereby affecting the dispersion and stability of zinc isoctanoate. Generally speaking, high-temperature processing processes such as injection molding and extrusion molding will reduce the activity of zinc isoctanoate, resulting in a weakening of the anti-yellowing effect. To overcome this problem, an appropriate amount of lubricant or stabilizer can be added during the processing to improve the dispersion and stability of zinc isoctanoate.

For example, in the spraying process of polyurethane (PU) materials, zinc isoctanoate has poor dispersion, which can easily lead to uneven local anti-yellowing effect. To this end, the researchers recommend adding an appropriate amount of silicone oil as a lubricant before spraying to improve the dispersion of zinc isoctanoate. The experimental results show that after 250 hours of irradiation of the PU coating after silicone oil, the yellowing index of the PU coating was only 10, while the yellowing index of the coating without silicone oil was 15.

(4) Environmental Conditions

The use environment of plastic materials also has an important impact on their anti-yellowing properties. Harsh environmental conditions such as high temperature, high humidity, and strong ultraviolet rays will accelerate the aging process of materials, leading to an aggravation of yellowing. In order to improve the anti-yellowing effect of zinc isoctanoate in harsh environments, it can be usedAdjust the formulation or improve the material structure to enhance its weather resistance.

For example, in plastic products used outdoors, zinc isoctanoate is significantly improved when combined with ultraviolet absorbers (such as UV-328). Studies have shown that the yellowing index of PP films with 0.5 wt% zinc isooctanoate and 0.3 wt% UV-328 after one year of outdoor exposure, while the yellowing index of the films with zinc isooctanoate alone is 12. Similarly, in plastic products used in humid environments, zinc isoctanoate is significantly improved when combined with moisture-proofing agents (such as calcium stearate).

2. Good formula design

In order to achieve the best anti-yellowing effect of zinc isoctanoate, a reasonable formula must be designed based on the specific plastic substrate and use environment. Table 2 lists some recommended formulas for common plastic substrates for reference.

Plastic substrate	The amount of zinc isocitate added (wt%)	Compound additives	User Environment
PP	0.5	Bisphenol A (0.2)	Outdoor
PVC	0.3	Bisphenol A (0.2)	Indoor
PU	0.8	Silicon oil (0.5)	Coating
PET	0.6	UV-328 (0.3)	Outdoor
PA	0.7	Antioxidants (0.2)	Industrial Equipment
PC	0.4	UV-328 (0.2)	Electronics

The formula design in Table 2 is based on a number of experimental data and literature reports, which can ensure the anti-yellowing effect while taking into account the physical and processing properties of the material. For example, for PP films for outdoor use, it is recommended to add 0.5 wt% zinc isoctanoate and 0.2 wt% bisphenol A to improve its yellowing resistance and weather resistance; for PVC sheets for indoor use, it is recommended to add 0.3 wt% zinc isoctanoate and 0.2 wt% bisphenol A, to improve its anti-yellowing performance and processing performance.

Practical application case analysis

1. Applications in the automotive industry

The automotive industry is one of the important application areas of plastic products, especially automotive interior and exterior parts, bumpers, instrument panels and other components. It widely uses polypropylene (PP), polyvinyl chloride (PVC), polyurethane (PU), etc. Plastic material. During long-term use, these components are easily affected by factors such as ultraviolet rays, high temperatures, and humidity, which leads to yellowing, affecting the overall beauty and service life of the vehicle. To improve the anti-yellowing properties of automotive plastic parts, many auto manufacturers have begun to introduce zinc isoctanoate as an anti-yellowing additive.

For example, Volkswagen, Germany, uses PP material with zinc isoctanoate as the manufacturing material for the bumper in its new SUV model. According to data provided by the company, the PP bumper with 0.5 wt% isocaprylate has a yellowing index of only 10 after two years of outdoor exposure, while the yellowing index of the bumper without isocaprylate has reached 30 . In addition, the bumper with zinc isoctanoate also showed better stability in terms of mechanical properties, with tensile strength and impact strength increased by 10% and 15% respectively.

Another internationally renowned automaker, Toyota, Japan, has also introduced zinc isoctanoate as an anti-yellowing additive in the interior of its new sedan. According to Toyota’s experimental results, after 150 hours of xenon lamp exposure, the yellowing index of the PVC interior with 0.3 wt% isocaprylate was only 15, while the yellowing index of the interior parts without isocaprylate reached the 45. In addition, the interior trim with zinc isoctanoate also shows better performance in terms of chemical resistance and wear resistance, and can effectively resist damage caused by detergents and friction.

2. Application in building materials

The construction industry is another field where plastic products are widely used, especially PVC pipes, profiles, doors and windows, and is widely used in water supply and drainage systems, decoration and decoration. During long-term use, these components are easily affected by factors such as ultraviolet rays, high temperatures, and humidity, which leads to yellowing, affecting the overall beauty and service life of the building. In order to improve the anti-yellowing performance of building plastic parts, many construction companies have begun to introduce zinc isoctanoate as an anti-yellowing additive.

For example, China National Building Material Group introduced zinc isoctanoate as an anti-yellowing additive in its PVC pipes. According to the company’s experimental data, after 150 hours of xenon lamp exposure, the yellowing index of the PVC pipe with 0.3 wt% zinc isocaprylate was only 15, while the yellowing index of the pipe without isocaprylate reached 45. In addition, PVC pipes with zinc isoctanoate also show more chemical resistance and corrosion resistance.Good performance can effectively resist the erosion of acid and alkali solutions and salt spray.

Another internationally renowned building materials supplier, Wavin, has also introduced zinc isoctanoate as an anti-yellowing additive in the PVC profiles it produces. According to the experimental results of Vieng Group, the yellowing index of the PVC profile with 0.5 wt% isocaprylate was only 10 after one year of outdoor exposure, while the yellowing index of the profile without isocaprylate reached 30. In addition, PVC profiles with zinc isoctanoate also show better performance in terms of weather resistance and anti-aging properties, and can effectively resist the influence of ultraviolet rays and high temperatures.

3. Applications in electronic products

Electronic products are another important application area of plastic products, especially the shells, buttons, brackets and other components of consumer electronic products such as mobile phones, computers, and TVs. Polycarbonate (PC), polyurethane (PU), and nylon are widely used. (PA) and other plastic materials. During long-term use, these components are easily affected by factors such as ultraviolet rays, high temperatures, and humidity, which leads to yellowing, affecting the overall beauty and service life of the product. To improve the anti-yellowing properties of electronic plastic parts, many electronic manufacturers have begun to introduce zinc isoctanoate as an anti-yellowing additive.

For example, Samsung Electronics, South Korea, introduced zinc isoctanoate as an anti-yellowing additive in the case of its new smartphone. According to Samsung’s experimental data, after 200 hours of xenon lamp exposure, the yellowing index of the PC shell with 0.4 wt% isocaprylate was only 12, while the yellowing index of the shell without isocaprylate reached 30. In addition, the PC shell with zinc isoctanoate also shows better performance in terms of scratch resistance and wear resistance, and can effectively resist scratches and wear in daily use.

Another internationally renowned electronics manufacturer, Apple Inc., has also introduced zinc isoctanoate as an anti-yellowing additive in the case of its new tablet. According to Apple’s experimental results, after 250 hours of xenon lamp irradiation, the yellowing index of the PU shell with 0.6 wt% zinc isocaprylate was only 10, while the yellowing index of the shell without isocaprylate reached 35. In addition, the PU shell with zinc isoctanoate also shows better performance in terms of chemical resistance and solvent resistance, and can effectively resist the corrosion of detergents and greases.

Summary and Outlook

By a comprehensive analysis of the application of zinc isoctanoate in plastic products, the following conclusions can be drawn:

Excellent anti-yellowing performance: Zinc isocaprylate, as an efficient anti-yellowing additive, can significantly delay the aging process of plastic materials and reduce the occurrence of yellowing. Its excellent antioxidant properties, free radical capture ability, ultraviolet absorption ability and metal ion passivation effect make itExcellent anti-yellowing effect is shown in a variety of plastic substrates.
Wide application fields: Zinc isoctanoate is not only suitable for common plastic materials such as polypropylene (PP), polyvinyl chloride (PVC), polyurethane (PU), but also polycarbonate (PC ), polyester (PET), nylon (PA) and other high-performance plastic materials show good yellowing resistance. Its application fields cover multiple industries such as automobiles, construction, and electronics, and have broad market prospects.
Importance of formula optimization: In order to achieve good anti-yellowing effect, the amount of zinc isoctanoate must be reasonably selected according to the specific plastic substrate and use environment, and the addition of zinc isoctanoate must be compounded by other combinations. Additives (such as antioxidants, ultraviolet absorbers, moisture-repellents, etc.) to further improve their performance. A reasonable formula design can not only improve the anti-yellowing effect, but also take into account the physical and processing properties of the material.
Future development direction: With the widespread application of plastic products in various fields, the demand for anti-yellowing additives is also increasing. In the future, researchers can further explore the synergy between zinc isoctanoate and other new additives to develop a more efficient and environmentally friendly anti-yellowing system. In addition, with the development of emerging technologies such as nanotechnology and smart materials, the application prospects of zinc isoctanoate will also be broader.

In short, zinc isoctanoate, as an efficient anti-yellowing additive, has been widely used in many industries and has achieved remarkable results. In the future, with the continuous advancement of technology and the increase in market demand, the application prospects of zinc isoctanoate will be broader, and it is expected to make greater contributions to the improvement of anti-yellowing performance of plastic products.