Calcium Carbonate Whiskers

Like other inorganic whiskers, calcium carbonate whiskers have high polarity, and therefore surface modification is required for filling polymer materials. The common surface... 

Typical fillers barium sulfate, calcium carbonate, carbon black, calcium sulfate whiskers, diatomaceous earth, glass fiber, glass spheres, hollow silicates, kaolin, mica, talc, wollastonite, silica, magnesium hydroxide, hydrotalcite, red mud, ground tire rubber, ferromagnetic powder, nickel fibers, wood flour, zirconium silicate, starch, soot, marble, aluminum, lignin, sand... 

Typical fillers glass fiber, glass beads, carbon fiber, aramid fiber, carbon black, metal flakes, zinc whisker, talc, calcium carbonate, PTFE fiber... 

NR composites and nanocomposites can be fabricated by three main techniques, namely latex compounding, solution mixing and melt blending. A variety of nanofillers, such as carbon black, silica, carbon nanotubes, graphene, calcium carbonate, organomodified clay, reclaimed rubber powder, recycled poly(ethylene terephthalate) powder, cellulose whiskers, starch nanocrystals, etc. have been used to reinforce NR composites and nanocomposites over the past two decades. In this chapter, we discuss the preparation and properties of NR composites and nanocomposites from the viewpoint of nanofillers. We divide nanofillers into four different types conventional fillers, natural fillers, metal or compound fillers and hybrid fillers, and the following discussion is based on this classification. 

Calcium carbonate (CaC03) whiskers are of several different types, such as calcite, aragonite, and vaterite. Aragonite whiskers are a new acicular material synthesized in recent years. They are a white powder and appear as acicular single crystals under a microscope. 

Calcite type calcium carbonate whiskers have a single crystal crystalline form and have almost no internal defects therefore they possess some special characteristics, such as high intensity, high modulus, good heat resistance and heat... 

Table 3.7 Physical and Chemical Properties of Calcium Carbonate Whiskers...

The treatment process of calcium carbonate whiskers using the dry method is as follows. Measured materials are mixed in a high-speed mixer at slow speed for 1 minute and at high speed for 1 minute. Wang et al. added calcium sulfate whiskers into a high-speed mixer, then heated and stirred. They then added surface treatment agent diluted with liquid paraffin at 100°C, stirred for 6 minutes, and obtained modified calcium sulfate whiskers. 

Takashi Sasaki, Kttagawa Takayki, Sato Shinataro et al. Core/ shell and hollow polymeric capsules prepared from calcium carbonate whisker. Polvmer Toum/il 37(6) 434-438, 2005. 

Takashi Sasaki, Shoko Kawagoe, Hajime Mitsuya et al. Glass transition of crosslinked polystyrene shells formed on the surface of calcium carbonate whisker. Journal of Polvmer Science B Polymer Physics. 44(17) 2475-2485, 2006. 

Mingshan Yang, Chenghan He. Preparation of calcium carbonate whiskers and modification of PP with it. Modern Plastics Processing and Applications, 20(6) 21-24, 2008. 

Although the price of inorganic whiskers is lower than in the past, it is still higher than that of other inorganic mineral packing. The price of relatively cheap calcium sulfate whiskers and calcium carbonate whiskers is hundreds of US dollars per tonne, but the price of calcium carbonate is tens of US dollars per tonne. Thus it can be seen that high cost hampers the... 

Figure 4.7 Influence of the filling content of calcium carbonate whiskers on rheological properties of polypropylene matrix (180°C).

The thermal stability of a material sometimes is represented by the temperature of 5% decomposition and usually can be determined by a thermogravimetric method. Because inorganic fillers have a high melting point, adding inorganic fillers into resin can improve the heat resistance of the polymer. A composite material is prepared by filling calcium carbonate whiskers into PP material. The thermal decomposition temperature (5% decomposition) of the composite material increased from 366.7 to 400.6°C as the whisker content was enhanced. 

In recent years, there has been a breakthrough in the manufacturing cost of potassium titanate whiskers, aluminum borate whiskers, and so forth. Meanwhile, inexpensive and high-quality inorganic whiskers such as calcium carbonate, calcium sulfate, and magnesium are successfully synthesized, which makes inorganic whiskers a new type of filling modification material of polymer materials. This field has become a research hotspot all over the world and reveals broad application and market prospects. 

The most studied anti-wear material modified by whiskers is PEEK. Wang et al." compared the performances of PEEK before and after modification with potassium titanate whiskers. The friction and wear performances of the latter showed obvious improvement over the former. Under 300 N, the wear resistance of the latter increases 2.64 and 2.11 times than the former, respectively. In addition, calcium carbonate whiskers have an excellent anti-friction effect on PEEK composite material. When the whisker content is less than 15%, the wear rate of the material decreases dramatically. The wear rate of the... 

Youming Cao. The preparations and applications of calcium carbonate whisker. New Chemical Materials, 26(101 23-25, 1998. 

Qingfeng Liu, Zhou Wang, Wenyu Shang et al. Preparation of calcium carbonate whisker. Inorganic Chemicals Lndustry, 32(2) 11-12, 2000. 

Lixia Li, Yuexin Han, Wanzhong Yin et al. The application and preparation technology of calcium carbonate whisker. Non-Ferrous Mining and Metallurgy, 21(Sl) 73-74, 2005. 

Calcium carbonate whiskers are produced with calcite, marble, or limestone as raw materials, and the process is simple. Compared with other whiskers obtained from more complex and high-temperature processes, calcium carbonate whiskers have lower cost and more significant economic value, leading to their large-scale use for industrial and consumer products. In addition, calcium carbonate whiskers are nontoxic and biodegradable in an acidic environment thus environmental pollution and any unfavorable effects on humans are low as well. ... 

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