Stain contact

Used in combination with other accelerators, the dithiophosphates reduce the risk of bloom and the formation of nitrosamines. Generally reversion stability is improved. The copper dithiophosphate will cause discolouration and contact staining. 

These are made by crosslinking unsaturated oils with sulphur (and an amine catalyst, usually triethanolamine) at 140-160 °C. These products will give dark coloured vulcanisates which have poor contact stain properties when in contact with painted surfaces. 

Contact stain is the stain which occurs on the surface directly in contact with the rubber. 

It must be noted that the stain on the surface directly in contact with the rubber is always contact stain even if the stain has to be intensified by exposure to light after removal of the rubber, whilst any stain outside the area of contact is always migration stain. 

BS 903 Part A3384 is identical to ISO 3865. ASTM D92585 has methods for contact, migration and diffusion (equivalent to penetration) staining. The contact stain method is similar to ISO 3865 except that there is no provision for developing the stain by exposure to light. Migration stain is not measured at the same time. 

Trinitrotoluene (2,4,6-trinilrololueue, TNT [CAS 118-96-7]) Irritating upon direct contact. Stains tissues yellow. Causes sensitization dermatitis. Vapors irritating to the respiratory tract. May cause liver injury, methemoglobinemia (see p 261). Occupational overexposure associated with cataracts. Causes vasodilation, including coronary arteries. Headache and drop in blood pressure are common. Well absorbed by all routes. Tolerance to vasodilation can occur cessation of exposure may precipitate angina pectoris in pharmacologically dependent workers. See also nitrates, p 279. 

Some rubber compositions, for example those containing reactive chlorine, can promote the surface corrosion of metals in contact with them, and in certain applications this can be sufficient to impair component performance. To guard against the use of such materials, a test method is described in ISO 6505 (BS903. Part A37). The procedure is similar to that for contact stain, in that a. sandwich of rubber and test surface, in this case a specified metal, is stored under load in a temperature-controlled environment for a given period. The measurement is a visual one and includes an indication of the ease of separation of the test rubber and the metal at the conclusion of the test. 

Features Pigments wh. and lt.-colored stocks causes mod. bm. discoloration during It. exposure contact stains materials offers exc. physical and elec, props., heal stability, chem. resist. disperses readily Regulatory FDA 21 CFR 175.300,177.1680,177.2280,177.2600 (5% max.)... 

In ammoniacal solution (in which the ion [AgfNHjlj]" is formed) it is readily reduced to silver (see above) by many organic compounds. The use of silver nitrate for marking clothes depends on its reduction by the material to black silver. The reduction also occurs even when the neutral solution comes in contact with the skin, and a black stain is left. Thus solid silver nitrate rubbed on the skin leaves a black deposit and so is used in surgery as a mild caustic—hence the old name for silver nitrate of lunar caustic. 

The tetroxide has been used to detect fingerprints and to stain fatty tissue for miscroscope slides. The metal is almost entirely used to produce very hard alloys, with other metals of the platinum group, for fountain pen tips, instrument pivots, phonograph needles, and electrical contacts. 

In humans, cases of dermatitis have been described after contact with DHBs. Combined exposure to hydroquinone and quinone airborne concentrations causes eye irritation, sensitivity to light, injury of the corneal epithelium, and visual disturbances (126). Cases with an appreciable loss of vision have occurred (127). Long-term exposure causes staining due to irritation or allergy of the conjunctiva and cornea and also opacities. Resorcinol and catechol are also irritants for eyes. 

Water content indirectly affects other lens characteristics. Water evaporation from the lens can result in a dry eye sensation and subsequent desiccative erosion of the cornea. Clinical studies have shown the incidence of corneal erosion as a result of lens desiccation to be a material-dependent and water-content-dependent phenomenon (25,26). The nature of water and sodium ions in hydrogels has been studied primarily by nmr and thermal techniques (27,28). An empirical relationship between water mobility in contact lens polymers and desiccative staining has been proposed (29). 

Water Tests. In colorfastness to water, ISO 10S-E01, the test specimen is placed in contact with the chosen adjacent fabrics, immersed in water, and placed wet between glass plates and left for 4 h at 37°C. After drying, the effect on the test specimen and stain on adjacents are assessed. The test, colorfastness to seawater, ISO 10S-E02, is the same as EOl but uses 30 g/L anhydrous sodium chloride solution instead of water. To test for colorfastness to chlorinated seawater/swimming baths water, ISO 10S-E03, the specimen is immersed in sodium hypochlorite solution containing either 100, 50, or 20 mg of active chlorine per Hter at pH 7.5 for 1 h at 27°C, rinsed, dried, and assessed. 

The best oxidation inhibitors are not usually the best antio2onants (qv). A disubstituted i ra-phenylenediamine such as AJ-isopropyl-AT-phenyl- -phenylenediamine is often selected for that purpose. -Phenylenediamine derivatives iaterfere with cure chemistry and scorchiness, and can stain objects ia contact with the vulcani2ate (114). On balance, /V-(1,3-dimethy1buty1)-/V-phenyl- -phenylenediamine and phenyl /to1y1- -pheny1enediamines have the best combination of properties. They are less scorchy and provide excellent o2one and heat resistance. Additional protection is gained ia blends with a small amount of EPDM mbber (126). 

If the patient wears soft contact lenses, a permanent yellow stain of the lenses may occur. It is a good idea to seek the advice of an ophthalmologist regarding corrective lenses while taking this drug. 

RIFAMPIN The patient is informed about the reddish-orange or reddish-brown discoloration of body fluids (eg, tears, sweat, sputum, saliva). Advise the patient not to wear soft contact lenses during therapy because they may be permanently stained. 

The nurse informs the patient that phenazopyridine may cause a reddish orange discoloration of the urine and may stain fabrics or contact lenses. The nurse assures the patient that this is normal and will subside when use of the drug is discontinued. 

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