The solid content of polyurethane adhesives: Definition, significance and influencing factors

The solid content of Polyurethane Adhesive, in simple terms, refers to the percentage by mass of non-volatile substances in the adhesive. These non-volatile substances mainly include Polyurethane Resin, curing agent, fillers, and other functional additives, while the volatile part is usually organic solvents or water. Solid content is one of the key technical indicators for evaluating the performance of polyurethane adhesives. 

 

The solid content directly affects the coating amount, drying speed, bonding strength and final usage cost of the adhesive. Products with high solid content mean there is more active ingredient per unit weight of adhesive, lower solvent content, and a thicker and stronger adhesive layer after drying and curing. At the same time, high solid content helps reduce the emission of volatile organic compounds, meeting environmental protection requirements. For different application scenarios, the appropriate solid content varies - for example, in situations requiring rapid positioning, a higher solid content is needed, while in cases where it is necessary to penetrate porous substrates deeply, a lower solid content is required. 

 

The solid content can be measured by the oven drying method (by heating the sample to a constant weight and then weighing and calculating) or by an infrared rapid moisture analyzer. Adjusting the viscosity of the polyurethane prepolymer, selecting appropriate solvents, or using reactive diluents are all common methods for controlling the solid content. When choosing a polyurethane adhesive in practice, one should pay full attention to the product's solid content parameters and match them with specific process conditions to achieve the best bonding effect and economic benefits.