Fibers Wollastonite

When glass fibers are compounded in polyamides in high content, warping of the molded product can become a problem. Wollastonite exhibits better properties in this aspect." Wollastonite is a white mineral that consists essentially of calcium metasilicate. It is commonly used as an inorganic filler material of thermoplastic polymers for molding. The wollastonite fibers are treated with silane surface treatments by using y-aminopropyltri-ethoxysilane or y-glycidylpropylmethoxysilane. 

J. Tong, M. Yunhai, J. Man, Effects of the wollastonite fiber modification on the sliding wear behavior of the UHMWPE composites. Wear 255, 734—741 (2003)... 

I. Krupa, V. Cecen, R. Tlili, A. Boudenne, and L. Ibos, "Thermophysical properties of ethylene-vinylacetate copolymer (EVA) filled with wollastonite fibers coated by silver," European Polymer Journal, vol. 44, pp. 3817-3826, 2008. 

The textile roller(Fig. 1) in the textile maehines is a worn part which should be replaced after a eertain time. The material of the roller is PBT. PBT has good dimensional stability, mechanical strength, stiffness, and fire retardant characteristics. To improve the meehanical strength, most of the plastics are filled with glass fiber. In this study, both glass and Wollastonite fiber filled PBT are investigated. Wollastonite is a calcium metasilicate (CaSiOs) which can improve thermal and dimensional stability at elevated temperatures[8]. 

The materials used were 30 wt% glass fiber filled PBT and 30 wt% Wollastonite fiber filled PBT. The PBT material, Shinte D202G30, was supplied by Shinkong Synthetic Fibers Co. The material was dried at 120 C for 3 hours before injection molding. The PVT diagram is shown in Fig. 4. 

Figs. 14 15 show the microstructure of the cell near the gate of glass fiber and Wollastonite fiber filled PBT. The cell structure of Wollastonite fiber filled PBT is more uniform than that of glass fiber filled PBT, and the cell size is around 10 [iva. 

Figure 9.Rim thickness variation vs. injection speed for foamed Wollastonite fiber filled PBT.

Figure 15. The cell structure of the Wollastonite fiber filled PBT near the gate.

Wollastonite is a preferred filler in some instances due to its fibrous form. While not as effective in improving the mechanical properties as glass fibers, it will give more strength than spherical fillers and less anisotropy than longer glass fibers. 

Another pyroxenoid, bustamite, [(Mn,Ca,)3Si309], whose stmcture closely approximates that of wollastonite, has also been identified in fibrous form, but no detailed examination has been undertaken to check the possibility that a structural segregation similar to wollastonite exists in this mineral, and might contribute to the formation of fibers. 

Epoxynovolak resin and BPA/DC-BMI prepolymer, tert.butyl peroxide and Zn acetate [106, 107] or 2-phenylimidazole and other catalysts [108] were filled with wollastonite. Carbon-fiber reinforced composites were obtained using a binder, which consisted of BPA/DC, BMI, an epoxynovolak, 2-ethyl-4-methylimidazole and an organic solvent [109]. A BPA/DC-BMI prepolymer in methylethylketone was mixed with middle-molecular-weight epoxide resin (Epikote 1001), 2-ethyl-4-methyl-imidazole, Zn acetate and triethylenediamine thermal shock resistant GRP was thus obtained [110]. 

Monoclinic minerals have an inclined angle of extinction. Orthorhombic minerals have parallel extinction. Chrysotile can be monoclinic or orthorhombic depending upon whether it is the ortho or clino variety. The b axis of the clino variety is so close to 90° (93°), (25) that the fibers will appear to have parallel extinction unless this is carefully measured. Anthophyllite, an orthorhombic mineral, has parallel extinction that is, the angle of extinction is zero degrees. All amphibole asbestos minerals except anthophyllite are monoclinic. Although wollastonite is a triclinic mineral, its extinction is parallel, or nearly parallel. The angle of extinction of some asbestos minerals is shown in table I (26, 27). 

Wollastonite. Wollastonite is a fibrous calcium silicate sometimes used in industry as a substitute for asbestos. Further testing will be necessary if wollastonite is present. See the discussion on fiber rolling, and the table on identification of fibers by dispersion stain. 

Tremolite and anthophylUte can be identified in 1.620 medium. In a talc sample where talc fibers may also be present, 1.605 medium is prefered. This will distinguish between talc fibers and asbesestos fibers by the dispersion staining colors. 1.605 medium will also distinguish between wollastonite and asbestos. 

Flexural strength, psi (MPa) Fly ash, wollastonite, and 1-3% glass fiber 1300-1700(9-12) ==700 (4.9) MaCTO-encapsulation of radioactive objects, structural ceramics... 

Substitutes for asbestos are constantly being developed (EPA 19891). Nonasbestos friction materials are currently being used in disc brake pads, and substitutes have been developed for drum brake linings. Substitutes include fibers made of carbon, steel, cellulose, ceramics, glass, and wollastonite and organic fibers made from aramid, polyethylene, polypropylene, and polytetrafluoroethylene (USGS 2000). No single substitute was as versatile and as cost effective as asbestos. 

MacDonald JL, Kane AB. 1997. Mesothelial cell proliferation and biopersistence of wollastonite and crocidolite asbestos fibers. Fundam Appl Toxicol 38 173-183. 

Epojty Resins as Matrix Resin, Burton and Handlovits used conventional epoxy resins as the matrix resin, and fiber glass, wollastonite and inorganic fillers as the reinforcement (29). 

Wollastonite is a natural calcium metasilicate mineral with an acicular structure. Silanized and uncoated versions with maximum fiber lengths up to 25 pm are used as inexpensive secondary reinforcements in friction materials. Short fiber attapulgite clays have also been developed as secondary reinforcements. 

Also, fibers are controversial. In one currently used handbook, natural, inorganic fibers such as wollastonite or asbestos have been included among fillers whereas other fibers were included in a separate group with only three materials glass, aramid, and graphite. But, mixtures of fibrous and particulate materials are found in many composites today and various natural materials having fibrous structures are considered fillers in technical papers. Again our definition includes these examples. 

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