High stiffness surface coating optimization through starch encapsulation of platy kaolin

Modified fillers consisting of kaolin particles encapsulated by starch have recently been demonstrated in mill trials to achieve significant filler loading levels without accompanying strength losses. In this work, laboratory experiments were conducted to explore the potential advantages of using starch-treated pigment for strength increases by application of surface coating. It is found that a platy clay coating will produce a higher increase in strength per unit weight of application compared to a fine clay, and more-so if the clay is encapsulated in starch. Starch encapsulation of clay produces a greater increase in strength than an equivalent weight proportion addition of starch to a kaolin formulation blend. The observations and measurements of changes in various physical properties of the coated samples are explained by a proportionate loss of void volume in the coating from the encapsulation process and the increase of stress transfer through introduction of higher platelet aspect ratio.