First, the acid value affects the starting speed of the curing reaction. Resins with higher acid values contain more acidic functional groups, which can act as catalysts in the adhesive system and accelerate the start of the curing reaction. For example, when used with some amine-containing curing agents, resins with high acid values can promote the faster reaction of amine groups with active groups in the resin, so that the adhesive can start crosslinking and curing in a shorter time, reduce waiting time, and improve production efficiency. On the contrary, when the acid value is low, the starting speed of the curing reaction is relatively slow, and additional catalysts may be required or the curing time may be extended to achieve the ideal initial curing effect.
Secondly, the acid value plays an important role in the degree of curing reaction and crosslinking density. Appropriate acid values help to form a uniform and high crosslinking density curing network structure. Too high an acid value may cause the curing reaction to be too intense, forming a large number of crosslinking points in a short time, but it may make the crosslinking structure uneven, resulting in local stress concentration, affecting the final performance of the adhesive, such as reduced toughness and impact resistance. If the acid value is too low, it may cause incomplete crosslinking, insufficient cohesive strength of the adhesive, and inability to provide sufficient bonding force, which may easily lead to debonding during use. For example, in wood bonding applications, Rosin modified phenolic resin with a suitable acid value can form a good chemical bond between the adhesive and the wood surface, while forming a stable cross-linking network inside to ensure the firmness and durability of the bonding.
Furthermore, the acid value will also affect the storage stability of the adhesive. Resins with high acid values may react more easily with impurities such as moisture in the air during storage, causing the resin properties to gradually change, affecting its effectiveness in the adhesive formulation. Resins with low acid values have relatively good storage stability, but may require more detailed adjustments to the curing conditions during use to compensate for their relatively low reactivity.
The acid value of Rosin modified phenolic resin is a key parameter. In adhesive applications, it is necessary to comprehensively consider its effects on the curing reaction speed, degree, cross-linking density, and storage stability. Only by accurately controlling the acid value and optimizing other formulations and process conditions can adhesive products with excellent performance and wide applicability be prepared to meet the requirements of bonding performance in different industrial fields.
