Fillers impurities

Tablel.l6 provides a qualitative assessment of the resistance of plastic and rubbers to attack by microorganisms. The controversial assessment in certain cases may be due to discrepancies in reported data arising from differences in measurement technique, materials used, average molecular weight of materials, fillers, impurities in polymers, etc.

Mineral fillers used are calcium carbonate (CaCOj), China Clay (Al/0H [Si.,0 J), miea especially muscovite (KAyOHjFlJAlSijOj J), silica flour (SiO ), talc (Mg, (OH)j[Si Oj J), and wollastonite (CaSiOj). Parameters that need to be considered during inorganic filler selection are basicity, filler impurities that may influence the resin euring proeess, and filler hardness that eauses abrasion of the mold [1]. Mica filled phenolics are used in electrical parts because mica adds outstanding dielectric properties, high thermal and chemical resistance and low water absorption [1]. 

The emission spectrum from a hollow cathode lamp includes, besides emission lines for the analyte, additional emission lines for impurities present in the metallic cathode and the filler gas. These additional lines serve as a potential source of stray radiation that may lead to an instrumental deviation from Beer s law. Normally the monochromator s slit width is set as wide as possible, improving the throughput of radiation, while being narrow enough to eliminate this source of stray radiation. 

Hardness. The hardness (qv), or related property abrasiveness, is an important filler property. Hardness is determined by comparison to materials of known hardness on the Mohs scale. On this nonlinear scale, diamond is rated 10, quartz 7, calcite 3, and talc 1. The abrasiveness of a filler is also dependent on psd and the presence of impurities, eg, ka olin clay (Mohs hardness of 3) can be quite abrasive because of the presence of quartz impurities. 

Optical Properties. Brightness, or visual whiteness of paper, can be defined as the degree to which light is reflected uniformly over the visible spectmm. Since pulp and typical impurities tend to be yellowish, blue dye is sometimes added in addition to appropriate fillers. The percentage reflectance is usually measured in the blue end of the spectmm at or near 457 nm (14). 

Low ionic impurity levels are imperative. In order to reduce the coefficient of thermal expansion of the final mol ding, and hence minimise stresses on the encapsulated siHcon chip, the highest possible filler loading is desired. This has to be balanced against the need to maintain as low a melt viscosity as possible to minimise the possibiHty of damage to the device during the encapsulation process. 

Cyclohexene oxide [286-20-4] M 98.2, b 131-133 /atm, dj 0.971, n 1.452. Fractionated through an efficient column. The main impurity is probably H2O. Dry over MgS04, filler and distil several limes (b 129-134 /aim). The residue is sometimes hard to remove from the distilling flask. To avoid this difficulty, add a small amount of a mixture of ground NaCl and Celite (1 1) to help break the residue particularly if H2O is added. [Org Synth Coll Vol I 185 7945.]... 

Impurities in mineral fillers can have serious effects. Coarse particles (grit) will lead to points of weakness in soft polymers which will therefore fail under stresses below that which might be expected. Traces of copper, manganese and iron can affect the oxidative stability whilst lead may react with sulphur-containing additives or sulphurous fumes in the atmosphere to give a discoloured product. 

Selective sorption by the filler sorption of one of the matrix components (residual monomer, low molecular homologs, various impurities) may lead to plasticization of the boundary layers and appearance of soft interphases [115,116]. 

Many impurities are present in commercial caprolactam which pass into the liquid wastes from PCA manufacture from which caprolactam monomer may be recovered. Also, the products of die thermal degradation of PCA, dyes, lubricants, and other PCA fillers may be contained in the regenerated CL. Identification of die contaminants by IR spectroscopy has led to the detection of lower carboxylic acids, secondary amines, ketones, and esters. Aldehydes and hydroperoxides have been identified by polarography and thin-layer chromatography. 

Also, nylon-6 waste may be hydrolyzed in the presence of an aqueous alkali metal hydroxide or acid5 to produce an alkali metal or acid salt of 6-aminocaproic acid (ACA). The reaction of nylon-6 waste with dilute hydrochloric acid is rapid at 90- 100°C. The reaction mixture is poured into water to form a dilute aqueous solution of the ACA salt. Filtration is used to remove undissolved impurities such as pigments, additives, and fillers followed by treatment of the acid solution with a strong cation exchange resin. A sulfonic acid cationic exchanger absorbs ACA salt and pure ACA is eluted with ammonium hydroxide to form a dilute aqueous solution. Pure ACA is obtained by crystallization of die solution. 

The recycling of contaminated polyurethane waste is described with reference to a glycolysis process developed by Bayer and Daimler-Benz in which the wastes from three-layer composite instrument panels are treated. The reuse of contaminated PU is achieved by dispersely integrating the impurities in the secondary polyol during the glycolytic dissociation. The impurities are modified in such a way that they act as a filler in the secondary polyol. 3 refs. 

Particulate composites, 26 754-755 ceramics processing, 5 653-654 extensional modulus of, 26 777 fabrication of, 26 766 Particulate emission limits, 13 183 Particulate emissions, reducing, 11 689 Particulate fillers, ll 302t, 303 for rubber, 21 772, 773 Particulate fluidized-bed regime, 11 801 Particulate impurities in gases, 13 464 in high purity gases, 13 466 Particulate matter (PM), 1 798-801 ... 

Kaolin clays are naturally occuring sedimentary deposits composed largely of kaolinite mineral. Typical impurities in these deposits are iron oxides, titanifer-ous minerals, silica, feldspar, mica, sulfides and organic matter. The majority of kaolin clay produced in the world is used in the paper industry as coating and filler materials. This mineral also makes an excellent filler, carrier, opacifier and diluent in a variety of industrial products such as paints, plastics, cement, rubber, pharmaceuticals, etc. 

Before the twentieth century, most government controls were concerned not with drugs but with impure and adulterated foods. Medicines were thought to pose problems similar to those presented by foods. Efficacy was questioned in two respects adulteration of active medicines by addition of inert fillers and false claims made for the so-called patent (secret) medicines or nostrums. Indeed, much of the development of the science of pharmacy in the nineteenth century was standardizing and improving prescription drugs. 

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