Adhesives and sealants are a broad class of materials that are rarely visible but serve important purposes almost everywhere you look. Applications are quite varied and include products like high performance epoxies used to hold together Formula 1 cars or airplanes, sealants between double-pane windows that make buildings more energy efficient, and even specially developed pressure sensitive adhesives that make your favorite pack of cookies resealable.
Performance requirements for many classes of products are unique. For example, medical adhesives favor biocompatibility whereas chemical resistance is far more important for a product like a fuel tank sealant. Therefore, base polymers and additives must be selected and formulated for each unique use case.
Homing in on the optimum properties requires a great deal of application & material knowledge, trial & error, and, of course, mixing. This might mean dissolving and dispersing tackifiers into pressure sensitive adhesives, blending polymers with filler and vacuum degassing moisture cured urethanes & silicone products, dispersing rheology modifiers like fumed silica, incorporating structures like hollow glass micro balloons to reduce density etc. One thing that is universally true adhesive and sealant products is that the must be mixed homogeneously and free of unwanted bubbles & voids to deliver the best performance.