Although manufactured as both ready-mix and dry powder mix products, at the time of use joint (or tape joint) compounds are wet, thick paste-like materials. The joint compound “mud”, is used in conjunction with a special paper tape to form smooth “invisible” connecting joints when gypsum wallboard is installed during the fabrication of interior wall and ceiling surfaces in home and commercial construction. This compound is also used as “spackle” to finish the slight indentations formed where nails or screws are used to attach the wallboard to wood or metal support structures.
Joint compounds are fairly easy to manufacture and do not necessarily require large capital intensive operations, so producers and formulations are numerous; although large operations offer typical economies of scale. Joint compounds are generally formulated with fillers of gypsum or calcium carbonate, binders such as starch, vinyl acetate or acrylic resins, bactericides and any host of thickeners, stabilizers and light-weighting additives.
Gel quality attapulgite has been the thickener and rheology modifier of choice for decades in literally hundreds of joint compound formulations. AMI’s brands of gel quality attapulgite are now the most widely used of all attapulgite thixotropes in joint compounds around the world. Kaolin products are used to improve slip (workability) and sanding properties due to their platy nature. They are especially useful in lightweight joint compounds in replacing mica and pyrophyllite.
Products of choice for this application are: