Document qkGBXNXkww5KRMg54pL1NwxN5

TWO OF THE . MORE IMPORTANT MINERAL'OR inorganic fillers employed in the plastics industry arc ^asbestos and diatomaceous silica. Mineral fillers are required where high hear resistance, exceptional elec trical properties j>r minimum moisture absorption char- . acterisrics are required in molded products. In addition, there are other 'characteristics of each of these fillers that make their use important in the plastics field. Chemical composition . The term asbestos Has now conic to include most of the more or less fibrous minerals. However, as employed in the..plastics industry, asbestos usually refers to rhe mineral chrjsc-tih. This is a: hydrated magnesium sili cate, corresponding in' composition fairly closely to the formula HiMgr,Si;Oj or 3MgO-iSiO;-iH;0.: Asbestos is employed'in the form of fabric, paper and definitely fibrous forms for laminated compositions, ecc., but its .general use as a filler is as asbestos finis or floats, consist ing of very fine fibers with associated dust and non- fibrbus asb.esric material. '-!> ' 7 Diatomaceous silica is a natural occurring opaline silica, containing three to eight percent of combined water and some two to six percent of other substances in ` chemical combination (alumina, iron oxide, alkaline .-earths and.alkali metals). The material is of plant "origin, consisting of the silicified residues of diatoms, which are microscopic aquatic plants of common occur rence. Diatomaceous silica Is unique among mineral fillers because of its microscopic structure, great bulk, high absorptive capacity arid low specific gravity.**.;;'; - Chemical analyses for' samples'of cirjsctH'i. asbestos from Quebec and .Arizona and of a leading grade of. .** V'tlcmaz'Ji Sil:ci *n P!iJctT Mod<rn Patties, October 1935. .. Moisture - CLoss at 1005 C.) Combined H.O Loss on ignition). SiO: Al;Oj Fc.O; Ms& ... CaO -vv' Na:0 - ' T*dle I ' \ ' ,v* ; Diatomaceous CkrysatiU ChryctUt Silica Canadian `lAritona ..`CtUre 1.88 y- 0,69 . ' ..iis.60 ` , 13.36 39.9L' 42.69 - All35 . - ' 0.39. 1.05--- . 0.63 . 41-57^ 41.73 .'Trace. 0.20 .: ' 0-30 -'0,22- . 92.42 3-86 ' 1.35- 0.60 0.28 1-01^ TOTAL \ * ^ icojfi . ,100.19 ' .100.04 General characteristics * J? Asbestos. The only haciiriil fibrous fnatcrial of mineral 'iferiipositibn available." Its use is',required when a fine .fibrods filler must be used for temperature conditions above that which can be tolerated by ih'c usual organic fillers, such as woodflour, cellulose, ere., which char at temperatures bejow that ic ivhich any apparent change occurs with asbestos. The specific gravity of pure cArjsjrile may be as low . as'z.ij,'htft for commercial grades the.range will tie ordinarily from 1.45 to i.So.; Color varies from nearly white to gray. Hear, resistance is good ro above'1400 deg. F. Dry density of commercial grades varies from ii to 40 per cii. ft. Fineness specifications vary -widely. . Fiber length in all materials used as a powdered ` filler is below '/a incHy:' ' 7 Diatcma'ciaus Silica.. Its' true spicifii: gravity is within : 'the range of.i.o to i.j. - Apparent'density (dry) is 8.0 to xj^lbs. per "cu%-ft. Fineness specifications range between zero percent on 200'mesh to ten to fifteen percent - on 150 mesh deperiding on the use!... While diatomaceous ' silica,has an extraordinarily high absorptive capacity for' `:v . ' \ - bcfOBEfi 1939 -si' (/VU ki J 355^'.y ~ m. m w! : liquid*, ctc-j itis readily mixed with plasticcoraposifions Asbestos Diatomaceous Silica acd can be handled satisfactorily in molding operations. Electrical insulations Surgical parts Dtvifopmmti during 1939 Wax compositions Roofings Asphaltic cements and en amels ''AsUitds. Greater effort'has been made on the part of. manufacturersi to effect standardization of grades and co ' provide flew and improved grades than in any previous :,year.'-/`.jjLt`least otic of the leading asbestos producers has carried Wt,'extensive technical investigations on the grades of fiber most suitable fer different purposes and . has set up a continuous technical service group to meet Friction materials *'Havcg,,typc compositions Coating compositions Rubber products Box toe compositions For many parts requiring excellent and durable surface finish Phone receivers' Precision molding the requirements of the plastics trade, both in supplying We`prttper grades of shore-fiber filler and iri dcvcloping the heist technique and.nierbods in'the use and appltca- Foims available Asbestos Diatomaceous Silica tion'of Asbestos in molding powders. Long fiber Natural powders and cal ' ySorai outstanding advances during. 1919 have been:. Short fiber . \ cined powders of differ Production of necessary grades now standardized "FloJts" -at economic price levels. Fabric Commercial availability of cleaner and better Yarn short-fiber grades. .. . Paper Establishment of expert technical service. 'ri^Low iron-content grades ent degrees of .fineness and . chemical purity Different density mate. rials available from' very light powders to those of 15Tb. per cu. ft. lo.ose Diatomaceous Silica. The use of diatomaceous silica weight; - - * r"! . in synthetic plastics is relatively new, but has been definitely increasing. During 1939, rhe increase in use Outstanding characteristics as fillers came to, nearly too percent over the average for the Asbestos Diatomaceous Silica - previous four year period. This has'eome about through. . wider acquaintance with the unique properties of diaromaceous silica and recognition of some of the'outstand ing qualities of molded objects filled with this inorganic material.' ; Two'outstanding developments have taken place in 193;.*: High heat resistance ` Chemical inertness Low moisture absorption Low shrinkage Low coefficient expansion Fair electrical properties. High heat resistance Chemical inertness . Minimum moisture absorp-' tion ' -- - Lowest specific'gravity of any mineral filler 1. The practical solution of problems in rhe fabrica. _ tion of molding powders containing high loadings. x. Introduction of certain new grades of material : ..which are characterized by more ready mixability. Permits high loadings High impact strength - (with better' quality grades) . - , .^01'' Exceptional surface finish Excellent electrical proper-. ties " _ ;y< ' Good to exceptional' sur-, face hardness Types of, products in which employed ' Asbestos Diatomaceous Silica Hearer plugs Battery boxes High heat-resistant parts, Phonograph records : Trade names Asbestos Good molding flow \ Grit-free grades available Diatomaceous Silica .irons, ovens, etc. Heater plugs I. Chrfsotile 1 Infusorial Electrical panels Sulphur plastics a. Canada z. Kieseliuhr Flbpririg compositions Electrical parts b. Arizona 3. Diatonite Laminated products Closures x. AmphtboU FILL WC by yIK PKEVIOtj dealt with! to thcrmci advantage^ fillers. Ti of thermo^ unique, in to rhe jt}i possible it selection, j siderably | these mate In this I fillers, nanj far more v resins. O volume, i forth in a; made to tf ` to produce .which hay the wood; 'with a stt far as poss id such a it maximum fiber is im .Cotton, problem' i factor. 7 fully iatei v-'jvdocl filler matt . AVaodfli matcly chi cotton is 1 such as'n filler. E dvc', will A close-up of one of the huge cliffs of dratomacedus earth at Lompoc, Cal., showing the great depth and uni formity of the deposit. (Photo, courtesy Johns-Manville) Fig. 1 show: in which th< Fig. 2 show* dency to curl magnification'. .flv.--. Figs. 3-4 show ntfcrbphotographs 0/ typical - '