Views: 5 Author: Site Editor Publish Time: 2024-09-03 Origin: Site
There are two main ways to eliminate static electricity:
(1) Physical method, because the size of static electricity is affected by temperature and humidity, it can be used to adjust the temperature and humidity, corona discharge and other physical methods to eliminate the electrostatic phenomenon on the surface of the item.
(2) Surface chemical method, that is, the use of surfactants, also known as antistatic agents, for surface treatment of fiber and plastic products or mixing in the interior of plastics to achieve the purpose of eliminating static electricity.
The washing effect of surfactants is the basic characteristic of the practical use of surfactants. It touches the daily lives of millions of families. And in all walks of life and various industrial production has also been more and more applied.
Antistatic effect of surfactants
Fibers and plastics and other products often produce static electricity due to friction, which affects the application performance of their products. For example, if the fiber fabric has static electricity, it often has the disadvantages of "close fitting" or "static sticking", and easy to vacuum or become dirty. If the plastic products have a greater impact on static electricity, not only the products are easy to absorb dust. It affects the transparency and surface cleanliness and beauty of its products, and also reduces the performance and value of the products.
In order to eliminate this electrostatic phenomenon, surfactants antistatic method is often used at present. Such surfactants are called antistatic agents.
Section 1 Electrostatic phenomena and causes
The order in which the fibers are charged varies somewhat, but fibers with amide bonds, such as wool, nylon and artificial wool, tend to be positively charged. The electrical status of commonly used plastics is shown in Table 10-2, and the electrical status of common substances is in the following order from positive to positive:
(+) Polyurethane - hair - nylon - wool - silk - viscose fiber - cotton - hard rubber - acetate fiber - Vinylon-polypropylene - polyester - polyacrylonitrile - polyvinyl chloride - vinyl chloride - acrylonitrile copolymer - polyethylene - polytetrafluoroethylene (-).
Although the cause of static electricity is not very clear at present, it is agreed that because different types of objects friction with each other, the friction between the objects will produce moving charges resulting in static electricity, the object with what kind of charge can be determined according to the gain and loss of electrical production. An object is positively charged if it loses electrons and negatively charged if it gains electrons.
Section 2 Antistatic agent
There are two main ways to eliminate static electricity:
(1) Physical method, because the size of static electricity is affected by temperature and humidity, it can be used to adjust the temperature and humidity, corona discharge and other physical methods to eliminate the electrostatic phenomenon on the surface of the item.
(2) Surface chemical method, that is, the use of surfactants, also known as antistatic agents, for surface treatment of fiber and plastic products or mixing in the interior of plastics to achieve the purpose of eliminating static electricity.
First, the antistatic agent of fiber
one As an antistatic agent should have the conditions:
(1) Does not change the feel of the fiber; (2) The antistatic effect is good, the amount is small, and it is still effective at low temperature; (3) Good compatibility with resin fibers; (4) Good compatibility with other auxiliaries; (5) No foaming phenomenon, and no water stains; (6) No toxicity, no damage to the skin; (7) Can maintain good stability.
2. Type of antistatic agent
The main types of antistatic agents used in fibers are cationic and zwitterionic surfactants.
3. The mechanism of antistatic agent
Antistatic mechanism: mainly in two aspects of preventing static electricity and surface charge from escaping when the surface of fiber fabric is subjected to friction. The structure of the surfactant is closely related to the prevention of triboelectrification. The surface charge dissipation is related to the amount of surfactant adsorbed on the fabric and the hygroscopic property.
Cationic surfactants are easily adsorbed to negatively charged fiber surfaces by their own positive charges.
① can neutralize the surface charge of the fiber;
② Because cationic surfactants are adsorbed on the fiber surface with positively charged quaternary ammonium ions and adsorbed on the fiber surface with hydrophobic hydrocarbon chains in the outward adsorption state, a layer of oriented adsorption film composed of hydrocarbon chains is formed on the fiber surface. This layer of adsorption film can effectively reduce the friction generated by friction on the fiber surface and weaken the friction charging phenomenon.
For the synthetic fiber with low polarity and strong hydrophobicity, the cationic surfactant adsorbs its hydrophobic hydrocarbon chain to the fiber surface by van der Waals force, while the polar quaternary ammonium group faces outward, so that the fiber surface is covered with hydrophilic polar group. This not only increases the conductivity of the fiber surface, but also increases the surface humidity, which is conducive to the electrostatic escape generated by friction and plays an antistatic role.
The adsorption capacity of dioctadecyl ammonium chloride on the surface of natural fiber is obviously higher than that of synthetic fiber. This indicates that it has a better antistatic effect on natural fibers.
Zionic surfactants and cationic surfactants with positive charges can also adsorb on the negatively charged fiber surface, neutralize the static charge, its hydrophobic group also has the effect of reducing friction, and compared with cationic surfactants, in its molecular structure there is also one more anionic group, so it can better increase humidity and charge escape. Therefore, zwitterionic surfactants are antistatic agents with good performance, but the price is high.
The antistatic effect of anionic and non-ionic surfactants on fiber surface is poor because of their low adsorption capacity. The adsorption capacity of non-ionic surfactants is higher than that of anionic surfactants because it is not affected by the surface charge of the fiber, but the electrostatic dispersion is poor, so the antistatic ability is much worse than that of cationic and zphoteric ionic surfactants.
Second, plastic antistatic agent
The mechanism of action of surfactant as an antistatic agent of plastic is that the surfactant is adsorbed on the plastic surface with hydrophobic hydrocarbon chain through van der Waals force to reach out to the polar group, and the directional adsorption film of surfactant is formed on the plastic surface to conduct electricity so that the static charge can escape well. At the same time, the adsorption film can also play a role in alleviating the friction of the plastic surface.
one Plastic antistatic agents according to the type of surfactants are divided into:
(1) Anionic type;
(2) cationic type;
(3) Zwitterionic type;
(4) Non-ionic type.
2. Antistatic agents can be divided into two categories according to the method of use:
(1) Surface coated antistatic agent;
(2) mixed antistatic agent.