Magnesium Oxides (MgOs) have been utilized in the Rubber Industry for more than 100 years. Shortly after the discovery of sulfur vulcanization in 1839, MgO and other inorganic oxides proved to accelerate the slow cure rate of sulfur used alone. It was not until the early 1900s when organic accelerators were developed and replaced magnesium and other oxides as primary accelerators in curing systems. MgO consumption decreased until the early 1930s during the birth of a new synthetic elastomer which used this oxide extensively to stabilize and neutralize (acid scavenge) the compound-polychloroprene (CR). Even now, at the beginning of the next century, the primary use of MgO in the rubber industry is still in polychloroprene (CR) cure systems. Through the years, compounders realized the benefits of MgO in other elastomers such as: chlorosulfonated polyethylene (CSM), fluoroelastomer (FKM), halobutyl (CIIR, BIIR), hydrogenated NBR (HNBR), polyepichlorohydrin (ECO) among others. Let's first look at how rubber grade MgOs are produced and their properties.
Early in the rubber industry only one type of MgO was available-heavy (due to its bulk density). This type was produced by thermally decomposing natural magnesites (MgCO2). The resultant grade was often impure, not very active and had a large particle size. With the development of CR, magnesia manufacturers produced a new, high purity, more active, smaller particle size MgO-extra light. This product was made by thermally decomposing basic magnesium carbonate (MgCO3). Still used today in pharmaceuticals and cosmetics, this MgO was replaced by a very active, smaller particle size MgO-light or technical light. Nearly all rubber compounders use this type of MgO. It is manufactured by thermally decomposing magnesium properties 2 types: continued hydroxide (Mg(OH)2). Its bulk density is between that of heavy and extra light and has a very high activity and small particle size. These latter two properties-activity and particle size-are the most important properties of any MgO utilized in rubber compounding.
Post time: Nov-15-2022