Guangzhou Jieneng Teknologi Tekstil Co, Ltd.
1. Struktur molekul, Properti Grup Karakteristik, and Addition Amounts
The efficacy of an anti-static agent primarily depends on its fundamental characteristics as a surfactant—surface activity. Surface activity is influenced by the types of hydrophilic and hydrophobic groups within the molecule, the molecular shape, and the molecular weight. When anti-static agent molecules are orientatedly adsorbed at interfaces, they reduce the free energy of the interface and the critical contact angle between water and plastic. This adsorption effect is determined not only by the properties of the matrix but also by the characteristics of the surfactant. According to the principle of polarity similarity, the hydrocarbon chain portion of the surfactant molecule tends to interact with polymer chain segments, while the polar group interacts with water in the air. As a hydrophobic material, the primary role of the anti-static agent on the polymer surface is to form a regular hydrophilic adsorption layer facing the water in the air.
Under identical air humidity conditions, anti-static agents with superior hydrophilicity can bind more water, enabling the polymer surface to adsorb more water and providing more favorable conditions for ionization, thereby enhancing the anti-static effect. Charge transfer can also occur through proton exchange. Anti-static agents containing hydroxyl or amino groups can form chains via hydrogen bonds and remain effective even under low humidity conditions. In dry environments, if immediate anti-static properties are required after molding, polyol monostearate anti-static agents are highly effective. Hydroxyethyl alkylamine in polypropylene exhibits optimal anti-static effects only after being stored for a period in an environment with 50% relative humidity, and its performance is significantly influenced by humidity. Monoglyceride stearate produces an immediate anti-static effect upon addition and is unaffected by humidity; however, its effectiveness diminishes over time with prolonged storage.
The efficacy of additive-type anti-static agents depends on their migration rate to the surface of the plastic product. When the plastic surface is covered with a continuous conductive layer, charge attenuation reaches its peak. If the molecular weight of the anti-static agent is too high, it hinders migration to the polymer surface; conversely, if the molecular weight is too low, it compromises wash resistance and surface abrasion resistance. Typically, the molecular weight of the anti-static agent is much lower than that of the polymer. Adding low-molecular-weight substances may degrade the physical and mechanical properties of the polymer material. To mitigate this adverse effect, the dosage of the anti-static agent is usually minimal, ranging from 1 ppm to 1000 ppm, or it can be diluted before addition. The dosage of the anti-static agent varies depending on the application of the product.
The CMC (critical micelle concentration) value serves as a measure of the surfactant’s surface activity. A smaller CMC value indicates a lower concentration required for the surfactant to achieve surface (interface) adsorption or micelle formation, and thus a lower onset concentration for the anti-static effect. The dosage of different types of anti-static agents varies and depends on the product form. There is an optimal dosage range: too low, and the anti-static effect is insufficient; too high, and it affects the physical and mechanical properties of the material. For thin products such as films and sheets, the dosage is relatively lower, whereas for thicker products, the dosage is higher.
2. Compatibility of Anti-Static Agents with Polymers
The compatibility of anti-static agents with polymers follows the principle of polarity similarity. Polymer materials typically have long carbon chain structures and belong predominantly to non-polar resins, some of which possess polar end groups that enhance polarity. Anti-static agents contain both hydrophobic groups (non-polar) and hydrophilic groups (polar). Generally, the longer the hydrophobic group carbon chain, the better the compatibility with the polymer. If the hydrophilic group has strong polarity, its compatibility with the polymer is poor; if the polarity is weak, the hydrophilic adsorption property is inadequate. Excessive compatibility makes it difficult for the anti-static agent to migrate out, failing to achieve the desired anti-static effect; poor compatibility results in rapid migration, shortening the duration of effectiveness and affecting long-term use. Therefore, these factors must be considered during the design and application of anti-static agents. Through experimentation, the appropriate type of anti-static agent and optimal dosage should be selected.
3. Influence of Other Additives
During the processing of polymer materials, stabilizers, pigments, plasticizers, lubricants, dispersants, or flame retardants are often added as auxiliary agents. The interactions between these additives and the anti-static agent significantly impact the anti-static effect. Misalnya, anionic stabilizers can form complexes with cationic anti-static agents, reducing their respective efficacies. Lubricants typically migrate rapidly to the polymer surface, inhibiting the transfer of the anti-static agent. If the lubricant molecular layer covers the anti-static agent molecular layer, it reduces the surface concentration of the anti-static agent, significantly affecting its performance; sometimes, due to the influence of the lubricant, the anti-static agent transfers to the surface. Plasticizers increase the distance between polymer chains, facilitating molecular movement, improving polymer porosity, and promoting the migration of the anti-static agent to the surface to exert its anti-static effect. Some plasticizers lower the glass transition temperature of the polymer, further enhancing the anti-static agent’s efficacy. The influence of the anti-static agent on various additives is difficult to predict in advance. Currently, most selections are made experimentally to determine the most suitable anti-static agent and dosage. Inorganic additives such as dispersants, stabilizers, and pigments generally exhibit strong adsorption capacity, making it challenging for the anti-static agent to migrate to the surface and adversely affecting its diffusion and migration. Most inorganic additives are fine particles with large surface areas, easily adsorbing the anti-static agent and preventing it from functioning effectively. Pigment particles tend to accumulate around the anti-static agent, hindering its outward diffusion. For example, adding titanium dioxide to ABS with the same anti-static agent concentration reduces the anti-static effect. Different inorganic fillers have varying adsorption properties, and their influence on the anti-static effect differs accordingly. Additionally, elastomers in polymer components also reduce the efficacy of the anti-static agent. Misalnya, in polypropylene-rubber composites, the anti-static agent tends to accumulate around the rubber component, impeding its migration to the surface.