What are the components of fiberglass sizing?
(1) Film former. The film former is the bonding component in the sizing agent. It is the main component for achieving single-filament bundling and maintaining the integrity of the original filament. It determines the stiffness and softness of the original filament to meet the process requirements of different types of fiberglass products. This component is used in the largest amount in the sizing agent formula, accounting for 2%-15%, and has an important influence on the performance and function of the sizing agent. It is the most critical component in the sizing agent. Different formulas use different types of raw materials. Sometimes more than two film formers are used to achieve the effect set by the sizing agent formula.
(2) Coupling agent. The use of coupling agent is one of the characteristics of the enhanced sizing agent. Through its own various different reactive groups, it combines fiberglass with polymers such as resin, plays a bridging role, achieves a good interface bonding between inorganic and organic substances, and enables fiberglass reinforced materials to obtain satisfactory application effects. Different coupling agents have different effects on the strength of fiberglass composite materials. It is necessary to correctly select the type of coupling agent based on the resin matrix material and its curing agent. Usually, the coupling agent is used in the sizing agent formula at a dosage of 0.2%-1.2%.
(3) Lubricant. Lubricant refers to a substance that lubricates the surface of fiberglass and reduces wear in wet state (dry wire drawing process) and dry state (raw fiber debonding and textile processing). Its dosage in the sizing agent is generally 0-5%. The type and dosage of lubricants used in sizing agents for different purposes vary greatly.
(4) Antistatic agent. Antistatic agent can effectively reduce the static effect of fiberglass during processing and use. Its effect is particularly significant in the sizing agent for short-cut fiberglass. The main working principle of antistatic agent is to reduce the friction coefficient and form a conductive channel.
(5) Auxiliary ingredients
1. Wetting agent. Wetting agent is a substance with surface activity. It can reduce the surface tension of the wetting agent system so that the wetting agent can more easily wet the surface of the fiberglass and achieve the effect of uniformly coating the fiberglass.
2. pH adjuster. The wetting agent system is generally neutral or weakly acidic. The pH adjuster is mostly used to adjust the stability of the wetting agent system and ensure the best use of the coupling agent. Commonly used pH adjusters include formic acid, acetic acid, citric acid, oxalic acid, ammonia water, organic amines, etc. Considering that the wetting agent is in direct contact with people and machinery, the pH value in the general formula is in the range of 4-7. For some wetting agents, their film-forming agent emulsion can only be used stably in alkaline conditions or can only achieve the required viscosity. The pH value of the wetting agent system is controlled at 8-11, but it is relatively rare.
3. Plasticizer. A substance added to the wetting agent system to improve the flexibility of the film-forming agent. When preparing the impregnation agent, it can sometimes be added directly to the film-forming agent. Commonly used plasticizers include dibutyl phthalate, dioctyl phthalate, tributyl phosphate, etc. The use of monofilament plasticizers sometimes affects the permeability of the yarn and is only used when the performance provided by the impregnation agent system does not meet the requirements.
4. Cross-linking agent. After the cross-linking agent is added to the impregnation agent system, it will produce a cross-linking reaction with a certain film-forming agent in the impregnation agent during the drying process of the original silk, and transform the original linear molecular structure into a three-dimensional network structure, thereby increasing the hardness of the film, which is very beneficial to the performance improvement of the hard yarn, but at the same time it will bring about the problem of difficulty in impregnation of the yarn and poor stability of the impregnation agent.
5. Preservatives and fungicides. When the impregnation agent formula contains starch, gelatin, hydrogenated vegetable oil, stearic acid or oleic acid lubricants, etc., which are prone to corruption, mildew, and deterioration, preservatives or fungicides are required.
6. Defoaming agent. The film-forming agent emulsion and lubricant in the wetting agent contain certain surface active ingredients, which are easy to produce foam during stirring and use, causing inconvenience in production and application. Sometimes defoamers need to be added to eliminate foam. Defoamers are generally silicone compounds, which are usually sprayed on the surface in small amounts after the wetting agent is prepared.
