Surface modifiers calcium carbonate

Hiflex - surface treated calcium carbonate for easy compounding in water pipes, cables, etc. Precipitated USP Grade - 3 grades for pharmaceutical, cosmetic, and food industries 402 - surface modified calcium carbonate for PVC plastisols and other plastics ECC International, Cornwall, UK... 

Carbokup. [Malvern Miner ] Surface-modified calcium carbonate. 

Haworth, B. and Raymond, C.L. (1997) Processing and fracture characterisation of polypropylene filled with surface modified calcium carbonate. Proceedings of the Eurofillers 97 Conference, Manchester, UK, September 1997,... 

Currently, surface-modified calcium carbonate whiskers are used mainly in the following polymer materials. 

Akovali G, Akman M A, Mechanical properties of plasma surface-modified calcium carbonate-polypropylene composites , Polym Int, 1997 42(2) 195-202. 

Lucie, S., Kovacevic, V., Packham, D.E., Bogner, A., Gerzina, A., Stearate-modified calcium carbonate fillers and their effect on the properties of polyvinyl acetate, composites. Proc. 2nd Int. Symp. Polymer Surface Modification Relevance to Adhesion, Newark, NJ, 24-26 May, 1999. 

Due to their often hydrophilic surfaces, inorganic components have to be hydrophobized in order to incorporate them in hydrophobic polymers. For the encapsulation in polystyrene shells, the surface of calcium carbonate was modified with stearic acid which allowed an encapsulation of about 5 wt% of the inorganic... 

Figure 5.9 shows that the activation index is almost zero for unmodified calcium carbonate whiskers, but increases significantly after surface modification. Thus it can be seen that sodium stearate is effective in modifying calcium carbonate whiskers. When the concentration of the modifier is less than 4.5%, the activation index of the whiskers gradually increases. 

Dry processing is applied more often in industrial production. We adopt dry processing to modify calcium carbonate whiskers and investigate the Influence of a titanate coupling agent on the surface properties of the whiskers. 

Figure 9.11 shows the effect of surface treatment on extensional viscosity for 30% calcium carbonate filled polystyrene [27]. The data are presented in two forms, namely steady state extensional viscosity vs. extensional rate in Figure 9.11(a) and steady state extensional viscosity vs. tensile stress in Figure 9.11(b). Irrespective of the type of data representation, it is seen that surface treated calcium carbonate reduces the level of extensional viscosity and brings it closer to that of the unfilled polymer. The yield stress value is reduced considerably though the values of the ratio of yield stress in extension to that of shear is still maintained nearer to the von Mises value of 1.73 as can be seen from Table 9.1. Surface treatment tends to modify the forces of particle-particle interaction and hence show reduced yield stress values due to lowering of the interaction forces [2,27]. 

Seawater Distillation. The principal thermal processes used to recover drinking water from seawater include multistage flash distillation, multi-effect distillation, and vapor compression distillation. In these processes, seawater is heated, and the relatively pure distillate is collected. Scale deposits, usually calcium carbonate, magnesium hydroxide, or calcium sulfate, lessen efficiency of these units. Dispersants such as poly(maleic acid) (39,40) inhibit scale formation, or at least modify it to form an easily removed powder, thus maintaining cleaner, more efficient heat-transfer surfaces. 

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 ... 

Phosphate and phosphonate molecules have a very high affinity for calcium carbonate surfaces, as shown by their influence on the precipitation and growth of calcite [164-166]. Accordingly, organophosphorus compounds such as alkylphosphoric acids [167-169] and phosphonic acid-terminated polyoxyethylene [170, 171] have been used to modify the surface of CaCOs powders. 

The absorption of vinyl chloride(VC) on surface-treated light-grade and nanoscale calcium carbonate was shown to obey the Langmuir isothermal equation in VC/calcium carbonate/water system. The absorption of VC on calcium carbonate was shown to increase with increase of the partial pressure of VC up to the saturation absorption and the absorption of VC on nanoscale calcium carbonate was greater than that of light-grade calcium carbonate at the same temp, and partial pressure of VC. The presence of calcium carbonate in VC suspension polymerisation system was found to influence the pressure/temp./ conversion(PTC) relationship of the reaction system. Based on the absorption of VC on calcium carbonate and VC distribution in vapour, water and polymer phases, a modified model to represent the PTC relationship of VC suspension polymerisation in the presence of calcium carbonate was proposed. 10 refs. 

The primary particle size of Winnofil stearate coated precipitated calcium carbonate from Zeneca Resins is in the region of 0.075 micron. When compounded into natural and synthetic elastomers, the hydrophobic surface coating assists wetting and aids dispersion. When compounded into plasticised PVC for cable sheathing, the PCC allows for formulations with minimal potential for acid gas release in combustion conditions. In rigid PVC, stearate coated PCC has been used in compounding as an alternative to conventional acrylic processing aids and as a means to reduce impact modifier levels. 

Surface grafting of barium sulfate is interesting Ifom the point of view of the kinetics of such reactions. Barium sulfate like calcium carbonate, is an inert filler. So it is necessary to modify its surface. First, barium chloride is reacted with sodium sulfate in the presence of a small amount of sodium 12-hydroxystearate. This introduces a controlled number of hydroxyl stearate sites onto the barium sulfate surface. The reaction is followed by a redox graft polymerization of acrylamide initiated by the hydroxyl stearate groups and ceric ion as a catalyst. Figures 6.9 to 6.11 show the effect of reaction substrates concentrations on polymerization rate. 

Soon after, Howard and Martin (1950) published an account of the first use of what was to become known as reversed-phase chromatography. Instead of using a polar stationary phase, such as silica or calcium carbonate, to sorb polar compounds from a nonpolar solvent, they made the stationary phase nonpolar to sorb the nonpolar compounds from a polar solvent. They treated silica with dichlorodimethylsilane, which modified the surface of the silica to a nonpolar phase. This phase effectively held a nonpolar solvent stationary while a polar solvent was acted as a mobile phase. They separated long-chain fatty acids in an aqueous-methanol (80 20) mobile phase by partitioning of the solutes into the nonpolar stationary phase, which was n-octane saturated with methanol. 

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