Factors affecting anti-static agents
1. The effect of anti-static agent depends on its basic characteristics as a surfactant. Surface activity is related to the type of hydrophilic group, the type of hydrophobic group, the shape of the molecule, and the size of the molecular weight. When the anti-static agent molecules do directional adsorption at the phase interface, it will reduce the free energy of the phase interface and the critical contact angle between water and plastic. This adsorption is only related to the nature of the matrix, but also related to the nature of the surfactant. In the case of the same air humidity, the anti-static agent with good hydrophilicity will bind more water, so that more water can be adsorbed on the polymer surface, and the ionization conditions are more sufficient, thereby improving the anti-static effect.
The effect of the additive anti-static agent is determined by the migration rate of the additive to the surface of the plastic product. When the surface of the plastic product is covered by a continuous conductive layer, the attenuation of the charge is optimal
2. The molecular weight of the anti-static agent is too high, which is not conducive to its migration to the surface of the polymer; the molecular weight is too low, the washing resistance and the surface friction resistance are not good. Usually the molecular weight of the anti-static agent is much smaller than the molecular weight of the polymer. The addition of low-molecular-weight substances may deteriorate the physical and mechanical properties of polymer materials. In order to reduce this adverse effect, the amount of anti-static agent added is usually very small.
3. The compatibility of the anti-static agent and the polymer follows the principle of compatibility with similar polarities. Polymer materials have long carbon chain structure, mostly non-polar resins, and some have polar end groups, which enhance the polarity. The anti-static agent has both a hydrophobic group and a hydrophilic group. Generally, the longer the hydrophobic carbon chain, the better the compatibility with the polymer. If the hydrophilic group is very polar, the compatibility with the polymer is not good; if the polarity is weak, the hydrophilic adsorption is poor. The compatibility is too good, the anti-static agent is not easy to migrate out, and the anti-static effect is not achieved; the compatibility is not good, the migration is too fast, and the validity period is too short, which affects long-term use.