Resin additives refer to substances used in the process of synthesizing resin to change the properties of the resin. Different resin additives have different properties, such as reducing resin viscosity, improving temperature resistance or enhancing resin toughness. Commonly used resin additives are diluent, toughening agent, coupling agent and filler.
Due to the rich variety and indispensable in the preparation process of resin, resin additives have very great application value.
- Thinner: Thinner is also called "cleaner". Diluent is a liquid substance with good miscibility added to the resin in order to reduce the viscosity of the resin and improve the process performance of the resin. Because of its unique organic-inorganic hybrid characteristics, excellent temperature resistance and dielectric properties, silyne hybrid resins have become increasingly widely used in aerospace and nuclear power fields. The viscosity of silyne hybrid resin usually affects its application value. Therefore, in the process of preparing silyne hybrid resin, diluent is often added to reduce its viscosity. For example, using phenylacetylene and methyldichlorosilane as raw materials, methyldiphenylethynylsilane (MDPES) was synthesized by the Grignard reagent method. When methyldiphenylethynyl silane is used as the main raw material to prepare silyne hybrid resin, benzoxazine-amino diluent is often added for modification.
Figure 1. Structural formula of silyne hybrid resin
- Filler: Filler is one of the additives used in the synthesis of resin. Fillers can be roughly divided into organic fillers, inorganic fillers, metal fillers, non-metallic fillers and other categories. On the one hand, choosing fillers in the process of synthesizing resins can specifically improve certain properties of epoxy resins (such as temperature resistance, dielectric properties, flame retardancy, etc.). On the other hand, the addition of fillers can correspondingly reduce the amount of resin and curing agent to achieve the purpose of reducing the cost of epoxy resin mixture. For example, light-cured composite resins have been widely used in clinic because of their superior aesthetic properties and biocompatibility. Its composition includes two main components: resin matrix and inorganic filler. Among them, the inorganic filler is closely related to the mechanical properties, optical properties and radiation resistance of the composite resin. The main reason for the failure of direct repair of light-curing composite resin is secondary caries and fracture of the filling body. The introduction of bioactive inorganic fillers provides a new method for solving micro-leakage at the edge of the filling body and secondary caries. The bioactive inorganic fillers commonly used in the process of synthesizing light-curing composite resin mainly include bioactive glass (BAG), calcium silicates, calcium phosphates such as hydroxyapatite (HA), amorphous calcium phosphate (ACP) and its nanoparticles (NACP), dicalcium phosphate anhydrous (DCPA) and dicalcium phosphate dihydrate (DCPD), etc
- Coupling agent: In the application process of epoxy resin, in order to improve its comprehensive performance and reduce costs, it is often necessary to add fillers. However, due to the poor compatibility of the filler and the epoxy resin, it is easy to agglomerate during the curing of the epoxy resin, thereby reducing the performance of the cured product. Therefore, the compatibility between the reinforcing filler and the epoxy resin is the most important link in the process of the filler reinforcing the epoxy resin. In order to improve the bonding force between the epoxy resin and the matrix or the filler, a coupling agent is often added during the preparation of the resin. Choosing a suitable structure of coupling agent is of great significance for the synthesis of excellent resin. At present, the coupling agent commonly used in the resin synthesis process is a silane coupling agent. For example, a new type of silane coupling agent with epoxy groups was synthesized using high-purity eugenol epoxy as raw material. The coupling agent molecule contains epoxy groups, which can effectively react with the epoxy resin matrix during the epoxy curing process, and the benzene ring segment contained in the coupling agent can improve the compatibility of the modified filler and the epoxy resin. The filler modified by the coupling agent can be effectively dispersed in the epoxy resin, and is fixed when the epoxy resin is cured, thereby effectively improving its performance modification effect on the epoxy resin.
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