Silane Coupling Agents in Plastics: A Detailed Explanation

Coupling Agents Modify Inorganic Fillers

The combination of organosilane coupling agents with inorganic fillers begins with the interaction between the hydroxyl groups on the inorganic filler surface and the silane oligomers. Therefore, the coupling agent's effectiveness is better for inorganic fillers with hydroxyl groups on their surface; conversely, it is difficult to achieve the desired effect for inorganic fillers without hydroxyl groups.

As plastics become more high-performance and multifunctional, corresponding higher demands are placed on organosilane coupling agents, thereby prompting the development of various new products with different functions and requirements. Some newly developed organosilane coupling agents in recent years possess certain unique properties. The ability of organosilane coupling agents from UnionSilicon to enhance the bonding strength of plastic products is due to a complex combination of factors, such as wettability, surface energy, boundary layer adsorption, polar adsorption, and acid-base interactions. The actual application methods of organosilane coupling agents mainly include pretreatment methods and overall blending processes.

The so-called pretreatment method involves first treating inorganic fillers with silane before adding them to the resin. Depending on the method of treatment, it can be further divided into dry processing and wet processing methods.

Dry processing involves initially adding inorganic fillers to a high-speed mixer, then slowly introducing the pre-mixed silicone oil solution while stirring, and uniformly dispersing it on the surface of the fillers for treatment. Wet processing, on the other hand, treats the inorganic fillers in a silicone oil solution and then dries them. Either dry or wet processing requires careful control of the treatment process, particularly the mixing and drying conditions, to ensure the coupling agent is evenly coated on the surface of the inorganic fillers.

When pre-treatment methods are not applicable or are insufficient, the whole blending method can be adopted. This method involves incorporating silicone coupling agents into the inorganic filler and resin system, and mixing them together. Its advantage is that the amount of coupling agent can be adjusted freely, and the batching process can be completed in a single step, thus commonly used in industrial production. However, compared to pre-treatment methods, to achieve the same modification effect, more silicone coupling agents must be used in the whole blending method. Silicone coupling agents can enhance the dispersion and bonding properties of inorganic fillers in polymers, making them widely used in the modification of plastic fillers (or reinforcement). Especially for plastics made with inorganic fillers that require electromagnetic, sound-insulating, flame-retardant, and other special functions, the use of silicone coupling agents will produce significant modification effects.

Among various coupling agents, silicone coupling agents are the earliest studied and most widely used. The use of organic silicon coupling agents in plastics can improve their mechanical, electrical, heat resistance, water resistance, weather resistance, flame retardancy, dispersibility, and processing performance.