Лако-красочные материалы — производство

Two types of fillers may be incorporated into formulated epoxy systems. Powder fillers are added to increase viscosity, improve abrasion resistance and gap-filling properties, impart specific electrical or mechanical properties, or reduce cost and shrinkage. Addition levels may be 50 to 300 parts by weight of resin (phr). Although most fillers will increase the density of the cured product, certain lightweight fillers will decrease density. Viscosity increases depend on surface area, oil absorption, and filler type. Chemical resistance may be improved or made worse, depending on fillers selected. Highly alkali fillers should be avoided, especially with acid-cured systems, as they may retard setting.

Fibrous fillers may be added to impart specific rheological properties or to reinforce the system. They will usually improve both tensile strength and impact resistance. Addition levels are much lower at 10 to 50 phr, as they usually cause much more rapid thickening. Table 3 lists common fillers.

Settlement of fillers during storage depends primarily on the particle size of the filler and its density, and the viscosity of the formulated product. Settlement can be reduced or eliminated by proper formulation. Fine particle fillers with relatively low specific gravity in high-viscosity products will settle much less, especially if the product is at all thixotropic. Where coarse fillers must be used, an approach toward a fully filled voidless system where the volume of liquid is such as just to fill the voids will solve the problem. Incorporation of fine fillers, use of a pigment-dispersing aid, and where application permits, use of a thix — otroping agent will help to reduce or eliminate settlement.

Depending on addition levels, fillers will generally increase the usable life and extend the cure time of the mix. Tensile and compressive strength usually increase maximally then decrease on further additions. Most fillers have relatively little effect on HDT. Chemical resistance will vary from filler to filler. Shrinkage is usually reduced.