Delamination of Foundry Coating Binder during long-term storage is a widespread and normal physical phenomenon. Most water-based and solvent-based special binders for foundry applications encounter such issues, differing only in the rate and degree of stratification rather than indicating product defects. The formula system of Foundry Coating Binder is not a single homogeneous liquid. It is a composite colloidal mixture composed of bonding resin, inorganic fillers, suspending additives, solvents, wetting agents and other ingredients. Significant differences in density, molecular weight and particle size among these components constitute the fundamental cause of delamination.
During long static storage, under gravitational force, dense inorganic powder and hard fillers within the system slowly sink and accumulate at the bottom of the container. In contrast, low-density substances such as resin solutions, solvents and defoaming additives rise to the upper section, finally forming a layered structure with clear liquid on top and thick sediment at the bottom. Generally, stratification emerges gradually after sealed storage at ambient temperature for 1 to 3 months, and becomes obvious after more than half a year of storage.
Storage conditions directly affect the stratification speed. High ambient temperature accelerates molecular movement inside the system, impairs colloidal suspension stability and speeds up component settlement. Low temperature reduces additive activity and unbalances the suspension system, which also aggravates delamination. Frequent temperature swings, incomplete sealing after opening and impurity contamination will further accelerate sedimentation and even caking. On the contrary, constant-temperature sealed storage in cool and dry surroundings can effectively slow down delamination.
It is essential to distinguish that delamination represents reversible physical separation rather than chemical deterioration. After stratification, components are unevenly distributed, yet core bonding groups and chemical properties remain unchanged. Fully stir the binder to restore a homogeneous state before application; indicators including bonding strength, adhesion and brushing performance will return to normal, fully meeting the application requirements of foundry coatings. Nevertheless, if layered materials are left untreated for a long time, sediments at the bottom will compact and form hard masses, slightly impairing application effects. Therefore, thoroughly stir Foundry Coating Binder stored for an extended period prior to use.
