Document NMoeV96byyEEXaxgaeMBjGwV

--. ,V-'v.-jF-. dfe&i*-' -^^ - r'-'Cr* -.- , PLAINTIFF'S EXHIBIT UC-2Z44 . ' ; ,' ... . <] ***&>.* ir-, mU-; 'j&fzttjEi ` `j.->,r ;!>.. -CAn*al Qentral. Af&fiag* ^ -' ::;-':--y--*,: <* *.,...*; v:-: :; , >:;'^^.-%Vf'f^'-'; ' '"" -'.^; * / s* ;-; ? \ (Fhmsdctioiu, Poiume TjtX,isi69^ pp. 2S.8-888) '- . " " v>^'* I rrriooncTipK,,- Increase heat and fire re-- . . The grades of asbestos nsed in' Stance ' >% , the cold-molding field are normal^ DURING the past twenty year* - ' (7)' Allpja ejeefiodf o'the, cold*.,''ly''described as floats and shorts, the ' use of . asbestos- fibre- in ' molding* from- the jackt and #?' The.: quality and physical ebarae. ; molding compounds twit- increasepdro:ve handling andibtivemeBtofthe /, teristicsLof the asbestos are impor- considerably, and . Bence tbe<.TMafl-"' uheured moldings. without-danger, * t*l and should be controlled. The . , ties field has served as air outlet for': of deformation oxwarpage^, '. 'vs.;." meet.'. important. mid troublesome large quantities of asbeatbs- fibre* ' .: Unfilled; molding* wohid-Tie im^ .vgriaWes within this field are; : from Canada., It is estimated. that' practical in tlmjioW^ W qiwlity of nbre approximately 14,000 tons.ofi sifc bestos fibres varying from Gratf* * ofbdWensand'phenolics. Because filler remit pnxfeo* toffieient;;'; sjXhotm&ldtfbe aff 'co_n_s_t_aent "a.s^upobs'shibilke to floats arc nsedr by the p^Ueav industry. The utility of filler in molding; fibrous charactei,,r^ Binders' bprraattyihed^ai* S***' bfrtdalw; repeated ahahges. -. of' ! --'iVS constant. . For eiao;; is,iiKn?eaed in bnllt. - _ prr^er?titsw.inoye Binder ia >- days, these fillers consisted' ofrsai*',; quired and; tkf& ihereasea prodnet. ' dust, cotton waste, powdered ashed- bestdfc- Si *' ' '" * (todti,- Gb . tife^^othat', hand, if the . - tos, silica, dlatomaceoav eaftij^ mrd'y~f*- mr.,. fe' h..teb hiia^^ lbsa bnlkyv the: "' clay, powdered glass,, cork* jjtarblte^. yiILiieat ' ".***' h^et&kg become*. - McfefVv:-; dost, slate floor; or other materttK.^. .!' dfihbcsnse it do** abl,isiaorb the"prjr:;-V Each filler had certain mJj&'ibig: quantify ^hindkri TMay e<?nf acteristics as well as tertsW jWtW-1 tionable ones. T-'tK-jle.ft 'ete*t*piiS''(Mir*n ieak" finr * tin rfsV causes scyenaing an^ raold^ J'; ; ing diffieultles,' sticking In this presentation it is proposed ', ;r , meteised? Baking time, .and^.'. to discuss only asbestos a* a ' *" ig*,.Ofien^ the taewdv--;. * in molding plasties. `'&o&i w---wrfY-*rr of the product ia.^ia-v '^. . , ._ , - r. s : '/tv II Tvprs or Furbc Ekeesss mrdstmro iq. /tl**<t:;^;; In general,, 1 he divided into tfio. es; (1) cold-i plastics, and s2S^3S! ,ck&B sTrl .Jf. i9*hJtie.th '.qait.^au tibuldilisiiiwirj^Kvi _^i' fe'-*shest^ Wyved by thfctadMP'yi;''V tw*>p .4^ Cold-Mii Asbestos filli ing advantages ltfl P^s't' propertfcK. -&&*(**&?*9;., rbi^rHimk - fh* flbr^mayi ptek;: opr addMSnaf . .'',r s-. f moisture;. thd*"la.' why some;'phui't,.; operators - prpdry: their fibre a*.*' .-'M" field: (1) Lower moId)ng^'Coft^ CoM-nmlded- cot*pora5S|r5arai ^ conddant^^';;;^ (2) Make cdd-moIdBag1 ^dmdbtk' genmal made h^ toading:$# j J^r4d4f*jBif filde* sh^W^,"-." by controlling the flow of oodeidak into - a heated internUhattier, afhm^ tej *t ap abdrte inin&audi,' The/'r ' under pressure while it i* idh the . which' the' descr^^j^-thoke'thafchiaV^^ , cold mold '%*' gradients are* added hr BqttW'.wnfe 'vrm^r*': tw'ta&. fiSrilf in-excess ' '* (3) Improve mechanical proper or in. solution,, ^hts mass become bf tlln'average flue iehgfii for that ' ties = somewhat tacky v and;,'; after - &- .' partkaday.' grad& These `wMskors' .' , (4) Increase hardnes* charge, it is a Unwed-ht `season^. twist and tangle; ai)d .interfere with ' (.1) Decrease: molded shrinkage. Later on it ta;sicreeBedi to Separate thaMfttUteyohtte screening pro- Johns-Manville Sesearck -Centar, Manville, New Jersey. fFormerty of Johns-Manville Re search Center; now retired lumps, whiskers, and other extr*j neons material' to provide rs- teirfy uniform granular compound for molding. cesa^Thcy: atee cause sticking to tb*;,...-;:. tuoldaj 'prddtic^ sarfdese blisters, and' in moot'cases affect the finish and the appearance of molded products. ' UCC 004642 -38 -- - ~w* near- After the molding'' powders "ere properly sized by screening* they are ready to be placed in- the mold. At this point* the hulk factor is extremely important^ because pre forming and final are one and the same operj^fas'^, Moreover, positive molds are bmS3J' and most molded parts are each' fitted with from one to several metal inserts. The molds are loaded by means of a small hand rake or mechanical rake. Good pourabiiity and proper bulk of the molding compounds are indispensable at this step for good and efficient cold-molding. If the molding compound charge is insuf ficient, then the molded part is offsize; and if the charge is excessive, the product is heavy and in some extreme cases may even damage the mold. The cold-molding operator has his own responsibilities. He must de velop a well-balanced compound in which the ratio of binder to filler is adjusted in relation to the bulk value of the filler. If he does this, sticking and off-size products, as well as other troubles, will be mini mized or eliminated. In most cases, the compounds are dusted with a powdered lubri cant before they are loaded into the mold, to prevent any sticking tendency. If the formulation is made correctly, the cold-molded com pound will flow properly and pro duce good material. The main fac tors the operator must constantly watch are: (1) hulk of the asbestos filler; (2 ratio of hinder or filler; (3) proper size of particles of the molding compound; and (4) mold ing pressure as well as baking tem peratures and cycles. In genera], it may be stated that cold-molded products are not suit able for power factor applications of any importance; but they are used extensively as heater plug parts and as housings for the shield ing of electrical unit*. High load ing of asbestos as a filler imparts the heat and flame resistance re quired. Thermoplastics In the thermoplastics field the fillers generally used are zinc oxide, titanium oxide, blanc fixe (barium sulphate), talc, diatomaceous earth, and asbestos. The common names of the most familiar thermoplastics are; cellu lose nitrate, cellulose acetate, cellu lose acetate butyrate, ethyl cellu lose, vinyls, polystyrenes, vinylidene chlorides, and esters of acrylic acid. The disadvantages of fillers in thermoplastics may be. summarized as follows: (1) Mineral fibres increase the specific gravity and molding weight of both thermoplastics and thermo setting molding compounds. (2) Fillers preclude production of transparent or translucent plas tics (molded, cast, or fabricated). Translucency can be obtained only to a limited extent when the re fractive index of the plastic and the filler are approximately the same; in these cases, however, the mold ings lack quality. (3) Fillers decrease water and moisture resistance. (1) Fillers also reduce electrical and mechanical properties. The ex ceptions are resistance to arcing and compressive strength. (5) Fillers in most cases damage the delicate molding and fabricating equipment. (6) Fillers frequently introduce new and sometimes complicated problems in the difficult art of col ouring, mottling, and configuration of thermoplastics. (7) Fillers in thermoplastics im pose the need for special types of processing, molds, and methods of molding. (8) Fillers increase the quantity of waste and re-work. (9) Fillers make injection and extrusion molding methods trouble some and wasteful. Consequently, work along these lines is chiefly experimental at present. Asbestos improves the heat re sistance and compressive strength of the thermoplastic moldings. It also reduces the cost and the tend ency to cold-flow, with resultant deformation and warpage. Although hardness is improved, the increase is only moderate. Resistance to flammability and arcing is also im proved by asbestos; however, this is true of all mineral fillers. Incorporation of fillers in ther moplastics is usually handled by one of three different methods, briefly described as follows: (1) Preliminary mixing of the plastic binder in powdered or flake form with the plasticizers, fillers, and other ingredients in ball mills or in internal mixers. (2) Blending of the ingredients, including binders, plasticizers, and fillers, with or without solvents, in heated kneaders. Hot-rolling is fol lowed by calendering, stamping, or by molding. (8) Incorporation of the fillers and plasticizers' on the hot rolls after the plastic binder has been consolidated into a plastic sheet. This procedure is used for blanking and/or fabricating and/or molding. To obtain a good product requires considerable good judgment on the part of the operator. This is in fluenced by: (1) method of incor poration; (2) time of mixing; (3) temperature of mix; (4) percentage of filler; (5) type of filler; (6) mixing technique; and (7) type and condition of the plastic binder. Because of the conditions under which hot-rolling is practical in the thermoplastics industry, and be cause the binders are plasticized, the operation is a safe and efficient one for the operator. Binders re main fusible indefinitely, and this permits perfect blending by pull ing the filled compound in fairly thin sheets over and over as re quired. Filler loadings are usually on the low side. In most cases, a well-formulated compound can be processed and molded without sticking to hot steel; however, in some special cases lu bricants are used to minimize pos sible difficulty. Most of the thermoplastics used for regular molding can be produced in a large variety of molding flows, because the plastic base and the plasticizer content, or their ratios, can be changed within wide limits. In thermoplastics, the molder must give close attention to: (1) nature, grade and flow of the base; (2) nature of the plasticizer, wheth er it is a solid or liqnid; (3) per centage of plasticizer; (4) nature and percentage of fibre; (5) pre heating; (6) molding temperature; and (7) molding pressure. Special techniques have been de veloped by the trade for the drill ing and machining of each par ticular type of thermoplastic, filled or unfilled. Asbestos, especially light-coloured fibres, can be used in moderate percentages in the manufacture of thermoplastic molding or calender ing materials based on ethyl cellu lose, vinylchloride acetate, and vinylchloride (polyethylene has been tried experimentally). The as bestos filler improves the hardness, heat resistance, burning rate, com pressive strength, and arcing resist ance of the product but it affects UCC 004643 -- 39 -- 51 rJ v?*l .41 adversely such wiactmrtiGS 'u specific gravity, tranitocency, ap pearance, depth of colour; other col our possibilities, flexibility, shock >&>.flexural' alter resist- ance, and ele jttfcs. la the tber use of fillers is Mield, the lited: Vinyl chloride acetate an iySuyfchloride- base floor tiles, however, constitute a very important and growing field. Work is also being done on floor coverings. Asbestos is used in some types of shellac-base compounds also, but not to the extent it was in the past. One manufacturer in the United States has been producing injection moldings in very large quantities with a compound made with miner al fillers, asphalts of high purity, pitches, plasticizers, and hardening or strengthening agents such as as bestos or other fibres of short or medium length. We understand that the cost of these moldings Tanges from $20 to $200 per ton. Thermosetting Plastic* The thermosetting field of plas tics is large, and use of fillers.has many advantages. Filled moldings are cheaper, and the fillers control the flow of the molding compound. In addition, they improve the me chanical strength and dimensional uniformity, they make the moldings more dependable and durable, and they decrease the shrinkage and warping tendencies of moldings after their ejection from the hot mold. F iltres shorten the curing time and increase hardness; they im prove heat, fire, and arcing resist ance. Some of the disadvantages in the use of commercial fillers in these plastics are: increase,- in specific gravity and molded- weight; de crease in water an^.jtpihistnre resist ance; lowering of proper ties; increase in ufljgjtaJBd' tear on equipment and motdSrdmreover, as bestos introduces ~gnlyVrock, and magnetite. These impurities increase deterioration of equipment; they make drilling and machining opera tions difficult. In the production of thermoset ting plastics it is generally accepted that, if the compound has a tend ency to stick to the hot-mixing rolls, it will also stick to the molds and cause rejections, expensive delays, and cleaning jobs. Moreover, the mirror polish of the cavities may he damaged, and internal lubrication of the molding compounds is indis pensable. If the compound flows poorly, production is decreased. Also, mold ings are mechanically weak, untrue, and defective dimensionally, and electrical and other properties are erratic. On the other hand, if the' com pound flows immoderately and too rapidly, it causes- excessive case hardening, excessive and wasteful flash, lack of dimensional accuracy, decreased mechanical and electrical strength, and upsetting of pins, re movable parts, inserts, and the like. It also interferes with the efficiency of the ejecting devices. Chrysotile asbestos as a filler has a number of advantages, some of which are common with other fill ers. Advantages of chrysotile are: (1) it is mineral in nature; (2) it is available in large quantities; (3) it is low or moderate in cost; (4) it is fibrous in structure; (5) it is pos sible to adjust percentages used in relation to fibre length; (6) it is easy to process and mold in com pounded form; (7) it retains the binders; (8) it is inert to reactions involving rolling, molding, and cur ing of the compounds; (9) it per mits the manufacturer to use high percentages of filler, e.g., 65 to 70 per cent; (lO) it allows the molder to vary the percentage - and fibre length- to achieve desired mechanical strengths; (11 it imparts tough ness; (12) it provides better surfacefinish than soft wood flours, barytes, or mka; (13) it retards the burning, rate; (14), it supplies heat and fire resistance; (15) it in creases hardness-; (19)- it reduces the natural shrinkage of the resins and plastic binders; (IT)' it allows blending with mineral and organic filfera; and (18). ft- increases- the moisture resistance of moldings partly filled with cellulose fillers- Compared with - other mineral fillers,- chrysotile has the following advantages; (1) it is fibrous and available in lengths desired; (2) it has excellent binder retention; (3) ( )it is easy to process and mold;' 4 it may be loaded at higher levels than other mineral fillers; and (5) it produces the hardest and tough est moldings at loadings impossible with other fillers. Asbestos - filled thermosetting moldings excel all others in- heat re sistance, up to temperatures of 450F., because asbestos loadings can be made at higher percentages than is possible with other mineral fillers. The impact strength can be varied within wide limits by vary ing the quantity and length of as bestos. Chrysotile asbestos has some dis advantages however. Chief of these (1) Combined Water, Combined water is present as a part of- the chrysotile structure. If temperatures . of molded products reach 450 F. or higher'and some of the combined water in the asbestos is liberated, the molding will blister and crack. This difficulty is par ticularly significant when heater plugs and other electrical and heat ing appliances are involved. (2) Fibre Length Fibre lengths of asbestos used in plastics vary, depending upon the grade. The molder must understand the type of fibre and something about its. properties, especially the specific gravity, bulk, molded weight, mechanical and electrical properties, water and moisture re sistance. In addition, he must under stand mixing techniques, colouring, surface finish, molded shrinkage, and percentage of fibre available in the asbestos grade used. (3) Dust' or, Fines The so-called 'dost* or `fines' in asbestos miry be granular, fibrous, or talcy. Variations hi the ratio of dost to fibre, and its- degree of fine- ness, will affect all those properties mentioned under the beading of fibre length. For example, surface quality of the molding will improve as the percentage of dust increases; however, all' other conditions being, equal,, the- surface quality of the' molding will be-f; lowered as thefibrous structure of the dust; or as the. particle: alse' Sf tHe dust;' in* creases, la -other words, a fine gran- _ ular dust will impart the best- sur- . face finish;.- , ' (4) Talcy Dust. ' Talcy dust adheres to the sur faces of the fibres, producing- what is called the `talcose', effect. It re tards, and. in extreme eases pre vents, adhesion of the resin binder to the asbestos filler nd adhesion of the blending charge to the hotter of the mixing rolls. This often re sults- in increased rolling time, stick ing, fouling, irregularities, poor de tail, inferior surface finish, and increased rejections or waste. . (5) Rock The so-called `rock fraction' in asbestos, which is mostly ground serpentine, is usually present in dif- UCC 004644 -- in -- ; '* feeing percentages. This fraction has a tendency to segregate when the ingredients forming the molding compound are given the preliminary dry- and cold-mixing. Accumulation of rock on the bottom of the mixer or hall mill unbalances the disposi tion of the ingredients. Presence of this rock in a molding compound will tend to scratch the delicate mir ror polish of the mold, which is costly to repolish. (ti) Pencils of Fibre Pencils' are defined as fibre bundles not well opened, and thin in cross-section. These pencils cause the charge to stick to the hot rolls and molds as a result of the pencils being crushed between the friction rolls or under the molding pressure. When this happens, the newly ex posed fibre surfaces remain partly coated and do not ride with the charge on the rolls or within the mold. When the pencils remain uncrushed they are enclosed by the binder, and, when opened by the grinding operation, they appear as poorly bound units, or as uncoated fibres or specks that show on the exposed surface of the moldings and throughout their mass. These pen cils may also he blamed to a cer tain extent for blistering of mate rial within the mold or in service. (7) Lumps of Fibre If the fibre is lumpy before the molding powder is made it will cause about the same trouble as pen cils. Lumps must be removed to en sure good disposition. The fibre product as produced from the mine should be void of lumps; if not, it should be screened or lightly fluffed before use. (8) ll'kiskers Small percentages of long fibres in an extremely short fibre product arc called `whiskers'. Although these whiskers may be only a frac tion of an inch longer than the main makeup of the fibre grade, they cause sticking and affect sur face quality and appearance. (!)) (int (irit is usually smaller in particle size then the rock discussed earlier; it is harmful, however, and can damage the molds. ! 10) Magnet/te Magnetite, an iron oxide having magnetic properties, is usually pres ent in most grades of chrvsotile as bestos. Its removal is difficult. The effect of magnetite on electrical properties lias been the subject of much discussion, particularly when it is coated by a resin. Its black colour is objectionable in moldings of light colour or shade. Electrical properties of the molding may or mav not be affected by the pres ence of magnetite. (11) Alkalinity Chrvsotile asbestos has a high al kalinity because of the nature of the molecular grouping of its ele ments, which, in the presence of water, combine to form a small per centage of Mg(OH)j, The pH is usually around 9.3 to 9.7. In many molding powders this alkalinity is not objectionable; in others, such as urea formaldehyde, alkalinity is troublesome. However, asbestos is not used to fill resins of this type, (12) Capacity for Moisture Absorption Asbestos, unfortunately, has a high capacity for absorbing mois ture. This effect can be counter acted. however, by oven-drying be fore the molding powders are made. (13) Surface Finish Imparted by Asbestos Floats of good grade impart good finish as well as the desired tough ness and mechanical strength. As the result of considerable experi mentation, floats of excellent qual ity are now available. (I I) Phenolic Molding Compounds Phenolic resins include the con densation products resulting from the controlled reaction of phenol with formaldehyde or with furfuraldehyde. The ratio of the reactants can be varied. The variations as well as the type of condensing agents, modifiers and/or additives used determine the characteristics of the resultant resin. One- and twostep resins and variations are made; they are used within the field dis cussed, the type selected being based on the properties desired in the end product. Phenolic molding com pounds are made by blending shortfibred asbestos and/or floats and subjecting the mixed ingredients (including fibre) to some type of mechanical or heat treatment while the mass is in motion. Chief among these treatments are: (1) prelimin ary dry-mixing in ball mills or in internal mixers followed bv hotblending in friction rolls, and fin ally grinding of the mass to .pow ders of the desired fineness; (2) preliminary dry-mixing in ball mills or in internal mixers followed bv hot-friction blending in Banbury mixers, and grinding to powders of the desired fineness. By this meth od of treatment, fibre length is sometimes reduced, and conseqnently the toughness and mechanical strengths of the moldings are de creased. However, good blends are made and the curing cycles are re duced. The purpose of the hot-rolling or hot-blending in Banburys is two fold, (I) to ensure thorough blend ing of the resin, fillers, dyes, and lubricants, and (2) to facilitate the advance of the resin in order to de crease molding time. Moreover, re duction in the amount of condensa tion produced in the mold favours production of perfect, blisterless moldings and tends to reduce mold ing flash. Thermoset flash is prac tically useless. On the other hand, the thermoplastics type can be re worked and mixed with virgin com pound, with or without the addi tion of plasticizers to compensate for volatilization in molding. Preforming.--Phenolic molding compounds are usually preformed in suitable equipment. Preforms produced with the original powders are made in various forms and sizes or pellets, or in shapes approximat ing the final molding. This method accelerates production, assures uni formity of the molding charge, and reduces waste and flash to a mini mum. Preheating.--Molding preforms are usually preheated in special ovens to bring them to the proper degree of plasticity. Preheating re duces molding time. When long or very long asbestos fibres are used in phenolic molding compounds they are mixed with the finely powdered resins and other ingredients in internal mixers, or by spraying liquid resins, or in solu tions. The resultant mixture, al though not very uniform, is used for molding. Mechanical mixing does not affect fibre length, but it does create a problem of loading the mold because of the high-bulk factor. Toughness and mechanical strengths are improved, but flow within the mold is retarded. Conse quently the molding cycles are long er, more internal lubricant is usual ly needed, surface quality is poor, and the molded mass is not so uni form as that resulting from short asbestos grades. The furan resins include the products resulting from the reaction of furfuryl alcohol and furfural; UCC 004645 41 -- .Tw^wwii Tips* n t: SwVi;:. .A-- Pmwxtm Ptnu* ' Q**.u fSSSSttSf Mold akrtnkf, Ito j (S^r* .OOOft-ftFOT TudW trnrth, P-*4.i: 4,00ft $m Compreoaive aUsicOtp FlaiuraJ at/enftb..........y.-^Vv..................... Impact ft, IK. /ti til notd^-Isod tast 7o4jnW-f8t>^lft.M0 Sardnao^ Rockwell........................ . MK-MII* Thermal conductivity, 1M d ^M^.ea.p 1*C km 6~t# ftaakt*ace to beat fcontiiKKms), T;..................... 340-400 Beat distortion tamp.* *F........................ . ... I... 2M-800 DtaWetrle etraictb, H to- thlekoceR, abort time, volt* per uati..................................................... Dielertrle strength, H in- thidmeaa; step bj step,-- 100-340 nits per mtt................................................... 75-324. Dielectric constant, 10* cydm.............................. 5-T Dmtfpotioa (power) (actor, 104 cycle*.................... Are resistance, seooadi.......................................... 0.10-4^0 Triees Watar sbeorptlon, 24 hr., H itt. thick, %............... Bnrnhw rate........................................................ 0.10-0,50 . *Vil Effect of weak adds............................................. None to atifbt Effect of stroof acids............................................ Decoap. by odd! in* adds; otbem m, /none Effect of weak aUtattes. Effect of strong alkelfea. DomkU oa s4kaUnity; aL of marked Effect to organic solvents. Hone on bleedproof maCerlalo M acbtning qualities........ Poor Molded qualities................ Paifto good In mold &P3-ft60* iMoo-ul* ftOoi-M** ^ 1.7ft e `W 3,900-4490 ifteoo-u.ooo *.600-9,066 RUO M54M Afaeoatml. Sams as 0.01-0.2 Slow Same as pbs- , notice " * In mold None None toslight Completely [ Fair to good Good i In mold or ; MMjUDMI Fauauamm Cold molded McUe* Inorganic 1.75MI) IftS-lftft O.OOft-O.QOf 5^500-7.000 30,900 9,000-11,000 040-<U0. MU0 10-17 250-400 265 i UAfUL* r (un+*mi .1,466-5400 : ftOOO-lftOOi ftTOft-lftOO* 0.40 MOft-ktoo 600 >400 . 120-12 17.1-12,2 0.000-04116 wot= 16,000 , 2.660^600 W7&-M93 900-1900. >400 250-400 36-116 320 ft 1-6.7 0.041-0.050 120-140 0.00-0.14 AW Nose to slight Decomposes 60-76 6.0 0.07 76-200 5.6-2.6 Nii Slight Decompose* 100-500 0.6-16 Nil Stigbt Decomposes Very tight tt'k SUgnt attack None oa bleedproof colours Pair Good In mold Nona Decomposes Attacked by eome Poor to fair Fair to good In even None None Poor Fair to good In oven C1) Data taken from Modtm PfeifferEacfriepsrfto, 1066 edition. furfuryl alcohol with formaldehyde; screener, the compound is. conveyed furfuryl alcohol and ketones, and to tile oven drier. The galvanised finally the product resulting from iron shell of7 the driers must be the polymerization of furfuryl al acidproof. The continuous convey cohol. ing belt should lie chromium plated. Resins made by reacting phenol and furfural also belong to the furan group, but their properties place them with the phenolics. The compound, spread'in thin lay ers, is dried under very closely con trolled temperature and humidity conditions. During the drying cycle the water content drops from 50 to 1 per cent and. chemical condensa (3 5) Melamine-Formaldehyde tion of the resin proceeds. Molding Compound* Cutting and grinding are the next Calcium cyanamide, a fertiliser steps. Grinding is done in ball mills prepared by heating calcium carbide where pigments, lubricants, and with nitrogen tinder pressure, is tbs catalysts are added. The catalysts starting point in the synthetic prep develop acidity when the compounds aration of melamine. This Watog* are. heated to molding temperatures. soluble material reacts with fbfijttdv These curing .agents reduce the cur- dehyde adjusted to a pff et 7Jf ing. time and make ths molding op to 9.0 by means of caustic sadft.')ke primary advantag**..*! melamine eration faster and mere, economical. The compound taken from the ball formaldehyde rwsnByShtiH&ared wi\S milt la ground to a. fine powder to cheaper urea toMUBfoto' type*' > provide a . more uniform molding are increased staBMCySp hp*t and powder. ,r- hot water, and gjnjjpgp faaistanee to If a molding compound of higher alkalies and fruit }4triSi. Moreover, density is desired; the material is the melamine formaldehyde resins heated from 120 to 220F. in Ban permit use of alkaline tillers, such bury mixers. The partial fusion thus as asbestos. Such fillers cannot be obtained reduces the volume of the used with the urea resins because molding compound. they would inhibit setting. Powders mast be kept in cold Molding powders are prepared by . storage under controlled conditions. miring the liquid resin' with - the desired percentage of filler. Double- (10) Color of Thsrmosstting arra open mixers provided with Maldingw ducts to remove the formaldehyde fumes are used. The damp mass is For most phenolic molding com dumped onto a screener provided pounds used for industrial and many with a device to break up the damp other applications, the colour is not resin-filler mixture. From this important. Colours other than black and brown are available today,,however, and the filler has to be select ed accordingly. (17) Texture* Asbestos of the chrysotile variety, whether in the form of shorts or floats, should be of soft texture. Semi-harsh and harsh chrysotile fibres have a tendency to pulverise during the processing cycles and are more difficult to coat with re sins than are the soft chrysotile fibres. Likewise, the molder will have lesa trouble in formulation if he knows that the physical proper ties of his fibres are not altered during his processing. In the paper. Heat Treatment of Chrysotile Asbestos Fibres (1), it waa stated that this kind of fibre in the form of floats is very good for use in plastics because of its im proved physical properties. Considerable research is being done in the fields of polyester and epoxy resins with asbestos in vari ous forms. These fields may be very important in. the not-too-distant fu ture. (18) Physical Properties of FibreContaining Molding* The accompanying Table, taken from the Modem Plastics Eneydo it) Babollet, M. 3., and Slum, W. C., Heat Treatment of Chrysotile Fibres; C.I.M., Trans., Vol. LVIII, 1956, pp. 33-37. UCC 004646 -42- ; .V?-V-sfe r. pedia for 19S6, show* the various properties of the. asbestos-filled molded compositions of the thermo setting type. Conclusions The role of asbestos in plastics has been reviewed from the view point of its usage in the mold-mold ing, thermoplastic and thermosetting fields. The advantages and disad vantages of chrysotile asbestos in these fields have been discussed, as well as general methods of com pounding the fillers with the resins. The use of asbestos in plastics is important to both the plastics man ufacturer and the asbestos indus try, and it will continue so for a long time. Today, in the competitive market, it is necessary for the asbestos fi bre salesman to understand the us age of asbestos in plastics and to be able to help the manufacturer wher ever possible. His contacts famish the leads for future development by the mines of the proper grades of asbestos for the plastics industry. The closest possible co-operation between the mines and the plastics manufacturer is essential to assure the success of the product by keep ing variations in quality within the narrowest limits. * UCC 004647 -- 43 --  ' h .f *V --'. : - ' Vr>,` \.r'f 1 Asbestos Floats By M. S. BADOLLET* (Ottawa General Meeting, ./anuary, 1952) (Trantactiom, Folume LV, 1952, pp. 185-189) Introduction sbestos floats may be A defined briefly as blends of airborne particles of fibrous asbes tos and dust produced during the milling stages and collected by Cot trell precipitators, dust sheds, or bughouses. The various grades of asbestos floats on the market contain fi brous asbestos particles ranging in length from microscopic to approx imately ^j-inch. The fines or dusts present in the floats are from 40 microns to 2 microns or less in crosssection. Airborne asbestos particles are of diverse length because they are collected at numerous places in the mill. There are: (1) dusts removed from dry rock storage bins, (2) dusts removed from rock and fibre screens, (3) particles from the tops of collectors, and (4) fines removed by suction from the processing equipment. .Sometimes the airborne particles are kept segregated, so that there is a partial separation by gravity. TIiis is accomplished by a series of dust chambers enclosed in a long, rectangular building. The longest and heaviest particles fall nearest to the air flow entrance, the small- ' Research Center, Johus-Manville Corporation, Manvilie, New Jersey, USA. est at a point farthest away and nearest the exit. Sometimes the air from the dust chamber building is passed through a series of baghouses or electric precipitators to collect the extremely fine particles which normally escape to the at mosphere. In other instances, the airborne particles by-pass the dust chambers and are passed through rows of bag collectors. Regardless of the method of col lecting the particles, the milling de partment must select proper fibre sizes for blending, producing uni form floats to meet the requirements of the trade. Sometimes one grade of float can be used successfully in many com mercial products; in other cases, great care must be taken to pro duce a float for use in a specific product. The present total production of all grades of Canadian floats ap proximates 40,000 tons per year and it is possible that this quantity may be greatly increased by the proposed expansion programmes now going into effect in Canada. Since floats are valued at $40 per ton at the Canadian mines, a tonnage of 40,000 has a potential sales value of $1,000,000. This di vision of the asbestos industry is a good business, and it is well worth the concentrated effort of research and development engineers to find new uses, and so expand the mar ket, for all available floats. Physical Properties or Floats According to the Quebec Screen classification, there are two general classes of floats, known as 7HF and 7TF. Samples of various commercial floats were obtained on the market and a series of tests were devised to determine the differences in their physical properties. Some of these tests were similar to those made by many manufacturers who use floats in their products. The results of some of these tests are given in Table I. They do not. however, in clude the official Quebec Screen test. Manufacturers using floats usually set up their own specifica tions, based upon requirements for their particular products. Loose Density The loose density of floats can be measured by slowly sifting the pow der into a can or container of defi nite dimensions so that the weight per cubic foot can be calculated. Although in some products the loose density of the floats is not par ticularly important, in others it is critical, so each float must be considered as an individual case. In the present investigation eleven 7RF floats were tested and their loose densities were found to range Table I Identification il) 7RF. . l'2) 7RF... !3> 7RF. . 141 7RF. . i.5) 7RF. 16) 7RF. . . (7) 7RF.. 181 7RF.. .. (9) 7RF.. .. E10) 7RF .. 01 j 7RF. . . 112) 7TF. . . (13) 7TF... : 14) 7TF. . . Loose. Density lb./cu.ft. 19 20 21 22 22 24 24 20 25 23 14 23 23 26 Material + 100 M % 3 4 4 4 3 5 5 6 7 7 1 2 2 3 Fines -200 M % 96 93 93 93 95 90 89 91 84 88 96 96 95 91 Grit +48M % 0.04 0.14 0.24 0.16 0.12 Tr. 0.06 0.12 0.24 0.46 0.04 Tr. 0.06 0.00 Whiskers +48 M % 1.90 2.50 2.26 1.30 0.80 1.16 1.28 4.12 0.70 2.38 0.50 0.30 0.60 0.10 Grit -48 M +80 M % 0.02 0.14 0.12 0.20 0.10 0.04 0.10 0.56 0.46 0.54 0.02 Tr. 0.06 Tr. Whiskers -48 M +80 M % Oil Adsorition c.c./g. fiber 0.64 0.66 1.18 0.94 0.46 0.96 1.12 1.10 1.30 0.92 0.84 0.66 0.74 0.75 0.68 0.65 0.68 0.71 0.66 0.65 0.65 1.05 0.50 0.70 0.16 0.75 0.65 068 -- 25 UCC 004648 pottUfflf per fell'.- ft. Tbe heaviest ir No, 8 and the light est No. II.- Nos. 1 to 5, inclusive, and No. 8, all with loose densities between.18 arul.39' pounds per cubic loot, may be cMtiit&ifed as falling within the same .rtsrte; as also may Nos. 6, 7, 8, AijPlOy which are slightly heavier' (28. to 26). Float No. 11 is in a class by itself and is light in weight as well as bulky (loose density 14). If density were the only physical property that had to be considered, this record would enable the manufacturer to select the proper one for his purpose. The three TF floats included in the Table differ from the RF floats in degree of particle fineness. Nos. 12 and 13 have identical loose den sity (23) while No. 14 is heavier (26). Classification by Wet Washino Fibre and Grit -j-IQO Meth A classification of the particles can be obtained by a wet-washing method which determines the amounts of fibre and grit plus-100mesb and of fines minus-20O-mesh. This information is particularly use ful if the floats are to be used in molding, extrusion, or spraying. The RF float No. 11 contains only 1 per cent of material larger than 100 mesh. In the other RF floats, the content ranges from 3 to 7 per cent, indicating the presence of material that is sometimes re ferred to as `whiskers'. In the plas tics industry, particles plus 100 mesh may be belpful in producing impact strength in the product. The three TF flouts contain al most identical amounts of plua-100mesh material. In two of them the percentage is lower than in the first ten RF floats. Fine* --Meth - The fines m4amt3$0-meah in the RF floats rangg * 84 to 96 per cent, and in the floats from 91 to 96 per cent. The material between pins 100 mesh (fibre and grit) and minus 200 mesh (fines) would be collected ori the 200 mesh screen. Its amount can be obtained by adding the plus 100 mesh and minus 200 mesb val ues shown in the Table and sub tracting the sum from 100. This test, although useful, does not distinguish between, or give the relative amounts of, `whiskers' (as bestos fibres) and particles of grit that might be present in the floats. &rU +48 Meth In many cases, the grit particles in the floats are of very diverse size. Usually, they are small pieces of serpentine rock and magnetite, or small bundles of asbestos fibre. Complete classification, therefore, requires a further breakdown to de termine the quantities of these ob jectionable particles present in the floats. This test is made by water elutriation and by careful separation of the grit from `whiskers' of fibre bundles. The amount of grit plus-48-mesh in the eleven 7RF floats ranges from a `trace' to 0.46 per cent. The percentage is lowest in samples. Nos. 1, 6, and 11 and highest in No. 10. Although these quantities of grit seem small, they could cause considerable trouble in a manufac turing process by plugging extrusion apparatus or scoring the walls of expensive molds. The three TF floats are almost free from grit plus-48-mesh. `Whitkert' +48 Meth Whiskers' are short asbestos fi bres that may be valuable or ob jectionable, depending upon the use for which the product is required. The quantity of whiskers in the eleven RF floats ranges from 0.50 per cent (to No. 11) to 4.12 per cent (to No. 8). In the TF floats, the range is from 0.10 per cent (No. 14) to 0.60 per cent (No. 13). Grit --48 Meth +80 Mesh In some special products, the presence of grit smaller than 48 mesh, and even smaller than plus 80 mesb. Is considered objection able. Therefore, a further separation is made to determine the quantities of this grit that may be present in these floats. As shown in Table I, the range for the eleven RF floats tested is from 0.02 per cent (Nos. 1 and 11) to 0.56 per cent (No. 8). Two of the TF floats are free from this size of grit and the third (No. 13) contains only 0.06 per cent. `Whiskers' --48 Meth +80 Mesh per cent (No. 9). Corresponding;,^ figures for the TF floats are a low of 0.16 per cent (No. 14) and a high of 0.70 per cent (No. 13). In the - manufacture of plastics, the presence of whiskers results in non-uniform pourability of ih molding powders. This .necessitate* ' a re-screening operation so that,1uniformly coated powders will prop-, erly fill the molds. In many easet+the whiskers and crudy fibre ban dies are not thoroughly covered by^.| the organic plastic material and( this increases the water absorption properties of the plastic material, which may result in the formation of blisters. Oil-Adsorptive Capacity The capacity of a float to adsorb oil is important because it gives an indication of ability to hold an or- game liquid when manufacturing a plastic or caulking compound. This test, made by manufactur- : ers, consists of titrating a given weight of float with oil until its-V adsorptive capacity is reached. In practice, tbe adsorptive capacity considered to have been reached: -s when oil can be released from a ball ijsfc of the thoroughly mixed float and. oil by applying a small amount of pressure against it. The results of this test are expressed in terms of cubic centimeters of oil per gramof float. For the eleven RF floats tested, tbe oil adsorptive capacity ranges from 0.65 to 1.05 cubic centimeters"/] per gram. Tbe value for No. II..+, (1.05 c.c./gm.) is much higher than ? 3 that for any of the others, which all fall between 0.65 and 0.6((.;s c.c./gm. except Nos. 2, 3, and 7';^ (0.71 to 0.75 c.c./gm.). Two of the TF floats. Nos. 18 and 14, have closely similar adsoi^+f| tive capacity, 0.65 and 0.68 c.c./gm., ' respectively. No. 12 gave a liighef jj value (0.75 c.c./gm.). " Miscellaneous Physical Tests Numerous other tests, of import ance to the manufacturer of certain +2 asbestos products, are made on floats. Data for these are given* in Table II and are summarized inthe following paragraphs. The presence of whiskers in the sizes of minus 48 mesh and plus 80 mesb is also objectio'nable because they affect the surface of certain products. The eleven RF floats tested con tain whiskers of this size ranging from 0.46 per cent (No. 5 to 1.30 Surface Area Study of the surface area of each float was made to obtain data on its covering power as a filler. In this . test, the surface area is measured by the air permeability method by means of the Bowen apparatus, fol- -- 26 -- Ifh UCC 004649 i;-v; ; 4*!ff Tablb II IttBNTlFfCA- TlON SUV7ACB AREA lb. /co. ft. % THICXNX88AT 200 Compress. Springback, % Thickness at Max. Compress. cm1 ,gm. 2,000 pjiJ. 3.000 p.s.i. 2,000 8,000 p.s.i. 2,000 p_a.i. 2.000 p.B.I. tl) 7TIF 14,800 t2) 7KF 11,300 <3) 7RF 13,000 (4) 7RF 11.800 89.9 93.0 93.5 96.5 94.7 97.0 99.2 99.1 29 28 28 29 32 2.5 2.8 32 3.1 3.7 32 3.2 3.3 32 3.3 34 <5> 7RF 13,000 95.0 98.2 28 31 2.6 3.4 (S) 7RF i7) 7RF i'8> 7RF (91 7RF < 10) 7RF (IJ) 7RF 14.000 13,900 12.500 1,S00 8.600 20,800 100.0 100.8 102-7 996 101.2 93.6 105.4 105.2 107.7 105.8 105.8 99.2 28 26 26 27 28 35 32 3.8 4.0 32 3.4 4.0 32 3-6 4.2 31 3.4 3.9 31 3.0 3.4 39 5.8 6.7 U2) 7TF 15,400 (13) 7TF 11,300 (14) 7TF 15.500 95.0 94.8 96.0 100.0 99.4 99.5 27 27 27 31 3.3 3.7 30 3.5 3.3 29 3.3 3.1 Surr. Cond. of Pressed SPECIMEN Sm'l whiskers & bundles Grift& few whia. & bund. Sra'I amt. of gritA wish. G ood smooth Grit mostly Good Surface lONIZABUE Slats, Micro- mhos/ cm (10 volte Dry Bulk, Vouop 100*. ce. 219 850 218 335 222 340 208 306 212 300 379 320 398 295 421 360 190 256 243 285 260 475 Good surface I-sxgegrit Good surface 221 176 396 295 290 275 % 0.16 0.17 0.18 0.16 0.17 0.36 0.38 0.26 0.12 0.14 0.15 0.15 0.14 0.36 RIME as Cl % NSTTC Rating* 0.017 4.7 0.024 0.025 0.022 6.0 5.7 ' 0.15 0.15 0.0049 0.0036 0.0015 5.9 3.4 0.022 0.0034 0.16 4.0 3.9 *Sle&iiremeQta start at200p.a.i. uuropoint. lowing the Lea and Norse tech nique (i). The eleven RF floats tested show a wide range of surface area, from 7.000 enri/gm. (No. 9) to 20,800 em'-'/gm. (No. 11). In other words, float No. 9 has the lowest, and float So. 2 1 has the greatest, covering }H>wer as a filler, lit plastics, the surface area of the float governs the amount of filler that can be used .successfully prior to pressing in a given mold. Two of the three TF floats (Nos. 12 and 14) have the same surface area, approximately 15,500 cm-'/gm. For No. 13 the value is 11,300 cin-/gin. The high value of 15,500 for Nos. 12 and 14 indicates the presence in these floats of a large percentage of fines. Density at 2.000 and 3,000 p.s.i. Ten-gram samples of each float were subjected to pressures of (I) 2.000 p.s.i. and (2) 3,000 p.s.i. and their densities calculated in pounds per cuhir foot. These pressures were selected because they correspond to the range of pressures used in the plastic-molding industry, and the data obtained are helpful in select ing the proper asbestos filler for molding powders. At 2.000 p.s.i. the densities range from 89.9 Ib./cu. ft. (No. I) to 102.7 Ib./cu. ft. (No. 8). Several nf the samples have substantially identical density, hut for the group as a whole the differences in density arc such as would influence the selection of the filler to be used for certain products. At 3.000 p.s.i., the densities range from 94.7 Ib./cu. ft. (No. 1) to 107.7 Ib./cu. ft. (No. 8). The in crease in density for the additional fl) For references see end of pa per. 1.000 p.s.i. pressure ranges from 3.2 to 6.2 Ib./cu. ft. C(impressibility of Floats at 2,000 and 3,000 p.s.i. In this test, a 10-gram sample of the float is compressed at 200 p.s.i. and its thickness measured. It is then compressed at (1) 2,000 p.s.i. and (2) 3,000 p.s.i. and its thickness again measured. The re duction in thickness, expressed as a percentage, gives a measure of the compressibility for each float. Thirteen of the fourteen floats test ed show about the same percentage of compressibility (27 to 29). For No. 11, the value (35) is appreci ably higher. This is an important property and must be taken into consideration when pressing a molding powder to a definite size after the molding cavity has been properly filled. Uniform compressibility is impor tant as a bulky fibre will also ex hibit poor dimensions after press ing. Springhack After Release of Pressures The amount of 'springback' of a molding powder is another im portant property considered by plastics manufacturers. If the springback is too great, it will be difficult to obtain the proper di mensions for a molded product. Too much emphasis' cannot be placed npon this property. All fourteen floats were tested for springback at pressures of both 2.000 and 3,000 p.s.i. As will be noted from the data in Table II, the springback factor is uniformly low for all of them except No. 11 which, also, is the sample with the highest percentage of compressibil ity. To use float No. ]], with a springback of 5.8 and 6.7 per cent, allowance must be made for its com pressibility or the plastics manu facturer cannot control the di mensions of his product. Surface Condition of Pressed Blocks The surface characteristics of pressed blocks of the floats are noted in Table II. The surfecas usual ly show long 'whiskers', short stub by fibre bundles, and grit, which generally are considered poor prop erties from the viewpoints of ap pearance and water adsorption. A smooth surface is desirable, provided the molded product meets all other specifications of the manu facturer. Five of the floats give good smooth surfaces and probably will be satisfactory for use in mold ing powders, provided other proper ties are acceptable. Ionisation Salts For the manufacture of some spe cial types of molding powders, it is essentia] that the asbestos fibre have low electrical conductivity. In this ease, some plastics companies make a test on water-soluble materia] leached from floats. Apparently, all floats contain a certain quantity of water-soluble material. Its conduc tivity is determined, and the re sult of the test is expressed in terms of micromhos per centimeter per 10 volts. For the eleven RF floats tested, this factor ranges from 190 (No. 9) to 421 (No. 8). For the TF floats. Nos. 12, 13, and 14, the values are, respectively, 221, 176, and 396. It is not known at present which values are objectionable, but it ap pears that a conductance of 300 mi cromhos or higher per centimeter -- 27 -- UCC 004650 per 10 volts may cause trouble, with the molded plastic product haring a low dielectric strength. Dry Balk The bulking values, of floats are sometimes considered Important fac tors in plastics as well as in drywall joint fillers. By some manufacturers, the balk ing value is expressed as the vol ume. in cubic centimeters, of a given weight, say 100 grams, of the float. Some fillers should have high dryhulk value while others should not; this depends entirely upon the in tended application. The eleven RF floats have dryhulk values ranging from a low of 255 (Mo. 9) to a high of 475 (No. II). For the three TF floats, Nos. 12, 13, and 14, the values are, re spectively, 295, 290, and 275---dif ferences that may lie within experi mental error. Water-Soluble Material All floats were analzed for wat er soluble materials by allowing a sample of each to stand in distilled water for 03 hours and filtering off the clear water. Aliquots of the fil trates were dried and weighed to determine total solids, and these were then analyzed for chlorides. The amount of water-soluble ma terial in the eleven RF floats ranges from 0.12 per cent (No. 9) to 0.38 per cent (No. 7). In the TF floats tile range is about the same, with a maximum of 0.36 per cent for No. Ik No good correlation exists be tween the ionizable salt values and the quantity of water-soluble mate rial. The percentage of chlorine in the residues also was determined. For the eleven RF floats it ranges from 0.0015 to 0.16 per cent, and for the three TF floats from 0.0084 to 0.16 per cent. Magnetic Rating Since many floats are used as fil lers in products employed by the electrical industry, it may be impor tant to learn something about their magnetic ratings. The test, an adap tation of the Mapes (2) test, meas ures the amount of magnetic pres ent. Ratings of the eleven RF floats range from 3.4 (No. 11) to 9.6 (No. 10). The other nine RF floats have ratings between 4.1 to 52) with an average of 5.4. The three TF floats range from 3.9 to 5.0, averaging 4.3. The maximum magnetic rating value for a successful float is not known precisely, but it is believed that the manufacturer would prefer the lowest rating available. It is known that the smallest trace of magnetite can be easily detected in a magnetic field and it may result in the rejection of the plastic ma terial. Us* of Asbbstos Floats Asbestos floats have a definite use in such industrial products as automobile body coatings, adhesives, caulking compounds, dry-wall joint filler, lubricating greases, asphalt and cold-water paints, plastics, molding powders, welding rods, in secticides, radiator scaling com pound, acoustical plasters, cements, and many others. .Asbestos floats offer to manufac turers the advantages of being a low-cost inorganic filler, which will improve impact strength and pro vide good workability, good binding qualities, heat resistance, fair acid and alkali resistance, large surface area, and availability in commercial quantities. A recommendation for the best grade of asbestos floats for a par ticular product should be made care fully, since each product has its own requirements and specifications. Automobile Body Undercoating A float for automobile body coat ing to be applied by spray gun may require the absence of `whiskers' and large particles of grit. If the coating is to be applied by brush, however, the presence of whiskers and grit would not be objectionable. Therefore, the selection of a float for this job depends upon the meth od of application and such other factors as bulk and fluidity when incorporated in a binder. Adhesive* The use of floats in adhesives depends upon the type and appli cation of the adhesive product. Tbe proper recommendation can be made only after knowing the desired prop erties of the adhesives and tbe meth od of application. The amount of floats in adhesives (3) varies be tween 9 and 40 per cent of the mix, depending upon the product. Caulking Compounds Caulking compounds may be sen sitive to changes in grade of floats. For example, a gun grade of caulk ing compound may require a float relatively free from whiskers and grit, while, for a caulking compound applied by knife, a float containing whiskers and some grit could be used. In general, the use of floats in caulking compounds (3) may range from 4 to 16 per cent by weight of compound. Wall Joints The manufacturer of dry-wall joint filler is very careful in his selection of floats. His specifica tions for asbestos fibre are rigid and he insists upon good bulking value, freedom from grit, good cov erage, and no whiskers. Very few natural floats on the market today fulfill these requirements and, therefore, a special float must be made for this job. The amount of floats (3) required for this use may vary between S and 20 per cent of the dry mix ready for the market. Lubricating Greases Various types of floats have been used in some grades of lubricating greases, but in most greases grit is objectionable. Whiskers may be permitted unless the customer's spe cification indicates otherwise. The amount of float used in greases var ies between 10 and 25 per cent of the product (3). Paints Paints, with either asphalt or cold-water base, may require a gritfree and whisker-free float if smooth surface is demanded. Other wise, some grit and whiskers are allowable. Paints may contain from 5 to 11 per cent of floats. Plastics and Molding Powders Floats, with specifications vary ing from customer to customer, are used extensively for plastics and molding powders. Tbe general opinion of the plas tics manufacturer is that fibrous float structure increases impact strength, allows a wide range for adjusting quantity of floats as filler, furnishes good binder retention and workability, imparts hardness and toughness to the moldings, increases heat and fire resistance, reduces natural shrinkage of resins and binders, reduces warpage and de formation, makes cold-molding pos sible by controlling the flow under pressure in the molds, allows blend ing of mineral and organic fillers, imparts good finish, improves the -- 28 -- UCC 004651 ......., electrical ' properties ~ and reduces' the cost of moldings. Molded plastics are carefully checked for specific gravity, flex ural strength, tensile: strength, com pressive strength, impact strength, water absorption, dielectric strength. power factor, shrinkage, heat re sistance, visual observations of molding qualities, and ejection from the wold. Jt is important, therefore, that the plastics manufacturer select asbestos floats with care so that molding powder and molded prod uct have the desired properties. The asbestos floats used as a filler in these materials generally form from 80 to 80 per cent of the mix (3). IFelding Rod* The welding rod manufacturer desires a float wfiich will produce good coating as a filler, and which lacks whiskers and. grit that might clog extrusion equipment. Floats also should be free from any sul phide mineral, or at least should contain less than the 0.01 per cent of sulphur that would produce ob noxious gas during welding. The amount of floats used for coating rods varies between 8 and 10 peT cent*. Insecticide* Floats sometimes are nsed as fill er for insecticides to be dusted or sprayed onto flowers, weeds, and other plants. In this case, the float should be a fine dust so that it will impart large coverage. Floats for -British Patent 535,355; Canadian Patent 385,792. this purpose roust compete with such other powders as talc and diatomaceous earth. The amount of float in a ready-to-use insecticide is approximately 4 to 5 per cent. Radiator Sealing Compound Various combinations of mate rials, including fine asbestos, are used in sealing compounds for au tomobile radiators. The asbestos forms from 1 to about 6 per cent by weight of the solids content of the mixturet. Acoustical Plasters Based upon the weight of the dry compound, some acoustical plasters contain from 6 to 15 per cent of asbestos floats. In this ap plication, the floats function as a filler to provide hulk and fire re sistance. Whiskers and grit are not objectionable unless a spray gun is used. Cements Cements and adhesives are con sidered similar by some authorities, and the amount of floats needed for adhesives would apply also to cements. Depending upon the type of cement and the application, the asbestos floats content ranges from 9 to 40 per cent (3). In many cases, whiskers and grit are permitted. Conclusions -jr (1) Fourteen asbestos floats pro duced in Canada have been exam ined in tests similar to those made fU. S. Patents 2,391,737, 2,315,321. by customers in their own labora tories. (2) Many of these floats have almost identical characteristics; however, one float. No. 11, differs considerably from all the others and has many unique properties. (3) . The type of float required for a particular product depends upon the use for which the product . is manufactured, and each manu facturer has his own specifications and methods for testing the float. (4) Float characteristics such as grit. whiskers, compressibility, springbaek, and magnetite rating are usually carefully checked by the plastics manufacturer, since these qualities affect his products. (5) Bulk, surface area, and den sity values of floats are considered important factors in such products as wall joint fillers, caulking com pounds, some pressed products, and acoustical plasters. (6) The amount of ionizable salts, water-soluble solids, and chlorides in the floats is a matter of importance and frequently is checked by plastics manufacturers interested in improving the elec trical properties of their products. References 1. Lea, F. M., and Nuuss, R. W., Specific Surface of Fine Powders; Soc. Chem. Inc., Trans., Sept, 1939, pp. 227-283. 2. A.S.T.M., Standards fin Textile Materials, D118-50T, Oct., 1950, pp. 197-202. 3. Bennett, H., The Chemical Form ulary, Vol. IX, 1951. HENLEY, Normann, Henley's Twen tieth Century Book of Formulas, Processes, and Trade Secrets, 1947. -- 29 -- UCC 004652