Differences Between Antioxidants 1010/1076/1098/1790/245

In the field of polymer material processing and application, engineering technicians often fall into the selection misunderstanding of "cost-only" or "heat resistance-only" when choosing hindered phenolic antioxidants. They make judgments merely based on the basic indicators in material specifications.

In fact, the five mainstream hindered phenolic antioxidants, namely 1010, 1076, 1098, 1790 and 245, have highly similar chemical functional group structures.

However, their microscopic behaviors in the polymer matrix are significantly different, which ultimately manifest as distinct engineering application performances.

The following is a comparison table of the physical parameters of these five types:

The root cause of their core differences lies in the physicochemical properties derived from molecular structures and the movement states in the polymer system determined thereby.

The following will deeply analyze the influence mechanism of key performance indicators on engineering applications based on these indicators, providing a theoretical basis for precise selection.

Molecular Weight: The Core Determinant of Antioxidant Long-Term Effectiveness

Molecular weight is the core parameter determining the diffusion behavior of antioxidants in the polymer matrix, which follows the free volume theory in polymer physics. Small-molecule additives diffuse relying on thermal motion and free volume. The higher the molecular weight, the lower the diffusion coefficient, and the stronger the movement resistance between polymer chain segments.

The five antioxidants show an obvious molecular weight gradient, in the descending order of 1010＞1098＞1076＞1790＞245, and their corresponding engineering performances present a clear rule:

1. 245 and 1076, with the smallest molecular weights, are highly active diffusing molecules in the polymer matrix, prone to volatilization and migration during processing or application.
2. 1010, with the largest molecular weight, has a molecular size close to that of short-chain oligomers, making it difficult to move in the polymer chain network, and its diffusion behavior is significantly inhibited.

From this, a core conclusion can be drawn: molecular weight is positively correlated with the long-term effectiveness of antioxidants. The higher the molecular weight, the stronger the resistance to volatilization, migration and extraction, and the more excellent the long-term thermal-oxidative stability.

This is why 1010 is widely used in long-term service scenarios such as automotive interior parts, cable sheaths and outdoor pipes, while 245 is only suitable for short-term processing protection such as single extrusion and thin-walled products.

Melting Point and Polarity: Key Factors Regulating Matrix Compatibility

The compatibility between antioxidants and the polymer matrix is jointly determined by melting point and molecular polarity, which directly affect the dispersion state and action mode of antioxidants during processing.

The five antioxidants have a wide range of melting points, which can be divided into the low-melting-point echelon (1076≈50℃, 245≈69℃) and the high-melting-point echelon (1010≈120℃, 1790≈165℃, 1098≈170℃). The action mechanisms of different echelons are significantly different:

1. Low-melting-point antioxidants can melt at conventional processing temperatures, and can quickly fill the free volume and molecular chain gaps of polymers. Taking 1076 as an example, it has a fast swelling rate in polyolefin materials and excellent dispersion uniformity, which can quickly capture free radicals generated by melt degradation, and has a prominent inhibitory effect on thermal-oxidative degradation in the initial stage of processing.
2. High-melting-point antioxidants exist as solid particles in the initial stage of processing, requiring stronger shear force to achieve uniform dispersion. However, this type of antioxidants has stronger molecular polarity. Especially for 1098, the amide functional groups in its molecular structure can form hydrogen bonding interactions with the amide bonds of nylon molecular chains, realizing molecular-level "anchoring".

In short, the melting point determines whether the antioxidant is a "fast-acting auxiliary agent actively participating in melt reaction" or a "long-acting auxiliary agent fixed by polar interaction". Once uniformly dispersed, high-melting-point antioxidants will exist stably in the matrix for a long time through physical steric hindrance and polar adsorption, which is the core reason why 1098 becomes a special antioxidant for nylon materials.

Migration Resistance: Synergistic Effect of Molecular Weight and Molecular Configuration

Migration resistance is a key indicator to measure whether antioxidants are prone to blooming. This property is highly correlated with molecular weight, but it is not the only determining factor. The influence of molecular configuration is also crucial.

There are two typical counterexamples in engineering: 1790, with a medium molecular weight, has strong migration resistance; 245, whose molecular weight is not the smallest, has extremely significant mobility. The core reason lies in whether the molecular configuration matches the polymer chain segments:

1. 1010 adopts a multi-arm branched structure, and its molecular morphology is similar to a "four-legged octopus". The four hindered phenol functional groups are distributed divergently, which are easy to entangle physically with the polymer chain network, greatly improving migration resistance.

2. 1790 has a rigid planar molecular structure. Under the extrusion and thermal motion of polymer chain segments, it is difficult to slip like linear molecules such as 1076, thus showing excellent migration resistance.

This characteristic is crucial for products with strict surface quality requirements. If excessive 1076 is added to products such as thick-walled household appliance shells and automotive exterior parts, surface blooming phenomenon is likely to occur in the later stage, affecting the appearance and performance of the products. The selection of "large-size, complex-configuration" antioxidants such as 1010 or 1790 can eliminate the blooming risk from the perspective of molecular structure.

Thermal Processing Stability: Competition for the "Survival Ability" of Antioxidants

There is a common misunderstanding in the industry: equating the thermal processing stability of antioxidants with heat resistance. In fact, the core of thermal processing stability is the "survival ability" of antioxidants in high-temperature processing environments, that is, whether the molecules are easy to decompose and volatilize, and whether they can continuously exert antioxidant effects.

Different types of antioxidants show significant differences in thermal processing performance:

1. Small-molecule antioxidants such as 245 and 1076 have low thermal decomposition temperatures, are prone to volatilization at high temperatures, and their own oxidation consumption is fast. This type of antioxidants belongs to "fast-acting protective additives", which can quickly inhibit the degradation reaction in the initial stage of processing, but cannot withstand long-time high-temperature processing, and are suitable for polyolefin products with low processing temperatures and single molding.
2. Macromolecular antioxidants such as 1010, 1098 and 1790 have higher thermal decomposition temperatures and multi-functional group synergistic structures. Even if one phenol hydroxyl group in the molecule fails, the remaining functional groups can still continue to exert antioxidant effects.

Therefore, in engineering plastics with narrow processing windows and processing temperatures exceeding 250℃, such as PBT, POM and nylon, macromolecular antioxidants are rigid demands. Their advantage lies not in faster reaction speed, but in "longer survival time", which can ensure that the molecular chains of materials do not break and degrade during multiple extrusion and injection molding processes.

Three-Step Engineering Selection Strategy

The core logic of antioxidant selection is to match molecular characteristics with engineering requirements, rather than simply comparing cost or heat resistance. Specifically, the following three-step method can be followed:

1. Step 1: Clarify the type of matrix resin

• For polyolefin materials, priority should be given to the compound system of 1010 and auxiliary antioxidant 168, which takes into account both processing stability and long-term effectiveness.
• For nylon materials, 1098 is the first choice, which realizes long-term stable protection by utilizing its hydrogen bonding interaction with nylon molecules.
• For other engineering plastics, it is necessary to select models in a targeted manner based on the compatibility test data provided by suppliers, and there is no universal standard scheme.

2. Step 2: Anchor the core failure risk

• If there is a concern about yellowing and decomposition during processing, it is necessary to add a sufficient amount of auxiliary antioxidants to the formula and use them in combination with main antioxidants such as 1076 and 1010.
• If there is a concern about chalking and embrittlement after long-term use, it is necessary to take long-acting antioxidants such as 1010 and 1790 as the formula basis to ensure the long-term service life of materials.
• If there is a concern about surface oil seepage and blooming, it is necessary to select models with good compatibility with the matrix, large molecular weight and complex configuration. For example, 1098 is selected for nylon, and 1010 instead of 1076 is selected for polyolefin.

3. Step 3: Match processing and service conditions

• When the processing temperature exceeds 280℃, 1076 and 245 should be used with caution, and high heat-resistant models such as 1010 and 1790 should be preferred.
• When the products need to be in long-term contact with hot water, acid and alkali environments, 1098 (for nylon materials) or 1010 (for polyolefin materials) with excellent extraction resistance should be preferred.
• When cost is sensitive and performance requirements are low, economical antioxidants such as 1076 and BHT can be selected, but the shortened service life of products should be accepted.

Summary

The selection of hindered phenolic antioxidants is essentially the precise control of molecular motion states. Molecular weight determines long-term effectiveness, melting point and polarity determine compatibility, molecular configuration determines migration resistance, and thermal stability determines processing adaptability. Only by combining the characteristics of matrix resin, failure risks and service environment can the optimal scheme be selected to achieve the balance between material performance and cost.