Aggression substances

Common packaging materials are a potential source of aggressive substance s, and careful selection is recommended to avoid surface deterioration. Where paper is in contact with aluminium, the chloride content should be below 0-05 7o, sulphate content below 0-25 7o, copper content below 0-01% and the pH of aqueous extracts in the range pH 5-5-7-5, in order to avoid corrosion in damp conditions. Papers and felts used in building applications should also conform to this specification as a minimum requirement and be of the highest quality, since metallic copper found in materials of inferior origin can result in severe local galvanic attack of aluminium. 

Chemical and thermal burns. The causes of chemical bums include the effect of concentrated acids, alkali, liquid ammonia, chlorosilanes and other aggressive substances. Thermal bums are caused with boiling solutions, hot water, vapour, inflamed gases, incandescent contact mass. Preventive and protective measures mostly include strict observance of all the established technological regulations and equipment maintenance order. 

While these techniques are widely used, they do not provide sufficient purity. Liquid phase purification is not an environmentally friendly process and requires corrosion-resistant equipment, as well as costly waste disposal processes. Alternative dry chemistry approaches, such as catalyst-assisted oxidation or ozone-eiuiched air oxidation, also require the use of aggressive substances or supplementary catalysts, which result in an additional contamination. Moreover, in many previous studies trial and error rather than insight and theory approaches have been applied. As a result, a lack of understanding and limited process control often lead to extensive sample losses of up to 90%. Because oxidation in air would be a controllable and enviromnentaUy friendly process, selective purification of carbon nanomaterials, such as CNT and ND, in air is very attractive. In contrast to current purification techniques, air oxidation does not require the use of toxic or aggressive chemicals, catalysts, or inhibitors and opens avenues for numerous new applications of carbon nanomaterials. 

A setup for pulse radiolysis of aggressive substances, such as anhydrous HNO3, has been described [110]. The all-glass flow system is designed to operate by remote control and each point where the unit has contact with the surrounding atmosphere is protected by a suitable guard tube. 

Problem Young people are familiar with acids as substances which can decompose other materials. They are usually not aware, though, that hydroxide solutions are also aggressive substances which should not be placed near the skin but espedally not near the eyes. The decomposing properties are mainly used to dissolve and remove organic leftovers from the kitchen or bathroom. The... 

During the initiation phase aggressive substances (CO2, chlorides) that can depas-sivate the steel penetrate from the surface into the bulk of the concrete ... 

Application of hydrophobic treatment to a concrete surface aims at reducing the capillary absorption of water and dissolved aggressive substances. Hydrophobising concrete leaves the pores open, so it does not affect the ingress of gaseous species. 

Nonwoven surfacing fabrics are used, with special gel coats, to give RPs additional resistance to abrasion and corrosion, optically smooth surface, and stability under load. They have been used for over a half century, meeting extreme fluctuations in temperature, chemically aggressive substances, mechanical stresses, high UV radiation, and... 

PE fibers (Figure 6.7), respectively, when both beams were subjected to about 80% of their corresponding calculated ultimate load in bending. The above results clearly show that the cracks thus formed in the HPFRCC under service load are small enough to resist the penetration of aggressive substances into the concrete and that the durability of RC structures can be enhanced greatly using this material. 

In addition to the known corrosive effects of alkali-metal hydroxide and nitrate solutions, intergranular stress corrosion cracking in unalloyed and low-alloy steels in contact with ammonium carbonate and crude methanol (methanol with low concentration of impurities) has also been observed (Matsukura and Sato 1977 Wendler-Kalsch 1983). When this group of materials comes into contact with various othCT aggressive substances, stress corrosion cracking occurs, primarily with transgranular characteristics. 

According to DIN 1045 concrete must be protected against aggressive substances if the chemical attack is severe and long-term. These are the requirements ... 

Waterproof and resistant to aggressive substances and resistant to the alkalinity of the concrete... 

Since use of gloves can sometimes cause accidents, and the substitution of noxious products by less aggressive substances is sometimes not possible for technical or economical reasons, skin-care products play an important role in the prevention of occupational contact dermatitis. Preventive skin care at the workplace may be divided into pre-exposure protection by protective creams, removal of irritants by mild cleaning agents, and enhancement of barrier-function generation by emollients or moisturisers. More details are given in Chap. 62, Barrier Creams/Emollients,... 

The question of the interaction of deformed cured rubbers with various aggressive substances has long attracted the attention of researchers. The phenomenon of ozone cracking of such rubbers is well known. Yu.S. Zuev [48-54] has shown that this process is not specific only for rubbers and only for ozone. 

We should think that since in most of the real cases, repeated deformation of cured rubbers is accomplished for prolonged periods in a medium containing oxygen or other forms of still more aggressive substances, this process should be considered as a variety of aging. As is well known, mechanical stresses activate chemical processes and inten-... 

The endangerment of technical installations through the impact of noxious substances acting from outside may directly affect the installation to be protected. Such effects may include decomposition of material through aggressive substances, interruption of contacts by chemical/physical reactions as well as various other effects. Once these reactions manage to disable safety-relevant parts or devices, the safety of the technical installation is impaired. Noxious substances act on a technical installation through the atmosphere, water, or soil. 

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