Stearic acid coating

Calcium carbonate used as an additive in polymeric systems, is a hydrophilic, finely divided powder. When used as a component in polyolefins, the calcium carbonate s surface is modified by coating it with a thin layer of stearic acid. Why would compounders prefer to use the stearic acid coated material over the uncoated mineral ... 

Fillers. Fillers are used to improve strength and stiffness, to lower cost, and to control gloss. The most common filler is calcium carbonate, which ranges in size from 0.07 to well over 50 m. Some forms are treated with a stearic acid coating. Clay fillers, such as calcined clay, improve electrical properties. Glass fibers, talc, and mica improve tensile strength and stiffness, but at a loss in ductility. 

Particle size is important and, for some applications requiring good weathering and impact performance (window profile), the ultrafine milled, high whiteness, natural version is normally used. To ease dispersion, the filler is usually coated with stearic acid. Coated ultrafine and precipitated calcium carbonates are claimed also to have a positive effect on impact properties in impact modified formulations (52, 294, 462). The abrasive wear of calcium carbonate, on melt processing equipment, is not significant but increases with increasing levels (177). 

TABLE 11.1 Effect of Stearic Acid Coating on Physical Properties of Magnesium Hydroxide Filled Polypropylene (50%)... 

Figure 7. Characteristic isotherm plot (17). Data are for indicated vapor/solid system at 20°C 1, H,0/PTFE 2, H/0/PE 3, H O/stearic-acid-coated copper 4. H,0/pyrolytic carbon-silicon alloy 5, CtHflSr/PTFE 6, CH,NOt/PTFE 7, H/O/ pyrolytic carbon 8. C,H,/PTFE 9, n-CJt OH/PTFE 10, ssrCfl OH/PTFE II, n-C,H,OH/PTFE 12, C,H,OH/PTFE 13, CCyPTFE 14, n-CJlu/PTFE 15,...

Stearic acid coated calcium carbonate (Multiflex SC) 17.5... 

Precipitated calcium carbonate with stearic acid coating 10-40... 

Stearic acid coated, precipitated calcium carbonate 0.1... 

Hyun Kim, Jagannath Biswas, Soonja Choe, Effects of stearic acid coating on zeolite in LDPE. LLDPE, HOPE Compos. Polym. 47, 3981-3992 (2006)... 

Drug release from stearic acid-coated microspheres may occur by diffusion when microspheres come in contact with aqueous fluids in the G1 tract. This release may occur when water diffuses into the interior of the microsphere, and allows the drug to diffuse across the release coat of the microsphere to the exterior [82], In addition, stearic acid may act as an emulgent that regulates the rate of drug release from microspheres [83], After ingestion, the drug will disperse and dissolve upon contact with GI fluid, possibly by interactions between stearic acid and the suspension media [85],... 

Angadi, S.C., Manjeshwar, L.S. Aminabhavi, T.M. Stearic acid-coated chitosan-based interpenetrating polymer network microspheres ... 

The filled composites containing 5 phr of nano-ZOS and 10-15 phr of SCC exhibited comparable tensile properties, tear strength and hardness as that of the microcomposite containing 5 phr of micro-ZnO and 30 phr of precipitated silica. These observations also support the findings that stearic acid-coated nano-ZnO (ZOS), nano-BIAT and SCC are better dispersed due to the small size of the particles as well as the higher specific surface area as already discussed in this chapter. 

A vast literature exists on the surface modification of CaC03 mineral with SA [3] including information in Chapter 6. Recently, Khanna et al. [5] have investigated the nature of surface interactions between CaC03 and SA. Using multiple analytical techniques, they have been able to identify and quantify as many as four different phases of stearic acid coating applied at the monolayer concentration ... 

Coating is increasingly used to enhance the properties of fillers. One of the most widely used materials is stearic acid. Metal stearates are particularly effective as coatings for reactive particulate fillers, such as magnesium hydroxide (MH), producing polypropylene compounds with better impact resistance than those containing uncoated, or stearic acid-coated fillers. 

Some studies with filled and unfilled rigid PVC were made in our laboratory to describe the effect of chalk as additional stabilizer. A suspension PVC (K-value 70) with an organotin stabilizer (2 phr) and lubricants (1.8 phr) was used as the experimental material. A part of this compound was filled with a stearic acid coated calcium carbonate (10 phr) as an additional component. The PVC powder and the additives were mixed at a high speed in an intensive mixer. The received dry blends were pelletized by extrusion to get a better dispersion of the additives in the polymer material. Finally, the granulates were processed by injection molding to test specimens for measurements of mechanical properties. 

Papirer and co-workers have also used IGC to study stearic acid coated calcium carbonates [17]. In their work, a high surface area precipitated filler was used, and coating was from toluene solution. They also prepared fractional coating levels based on solution adsorption isotherms. Stearic acid treatment was again found to decrease both the dispersive and polar contributions of surface energy to values typical of a hydrocarbon. Both acidic and basic probes were used in this work and interestingly, the uncoated filler was found to contain sites capable of interaction with both. 

---