Page 119 - SICCO catalog

SICCO Materials & Glossary
Natural PP
Gas-saving valves or cable lead-ins are products made of natural PP. The thermo- plastic processable Polypropylene has a high hardness and stiffness, is insensitive to stress cracking and shows a better resilience. However low temperatures restrict the ductility. The continuous ser- vice temperature is +110°C, a temporary operation at a temperature of +140°C is possible.
Natural PP is combustible and thus should not get in direct contact with open flames. The material is resistant against aqueous solutions of inorganic salts as well as most inorganic acids and leaches, even at higher concentrations and tempe- ratures up to 60°C. Natural PP is affected by oxidizing chemicals such as oleum, concentrated nitric acid or by halogens.
Black PP
This dyed, non-conductive thermoplas- tic material is used for Iris-Ports and connectors for exhaust system in the glove box as well as electrical boxes on the Automatic Desiccators. The black pigmentation serves especially for better identification of the plastic parts (e.g. compared with Plexiglas) and does not change the properties of the plastic. Properties and application recommenda- tions correspond therefore to the ones of natural PP. The black color can change respectively completely disappear in case of contact with chemicals.
Conductive PE
By addition of sooty particles, Polyethy- lene gets electro-conductive properties. The particles avoid electrostatic charging. Although this material shows conductive properties (spec. surface resistivity < 106 Ohm, DIN EN 60093, fulfils ATEX require- ments), they are significantly lower than those of metals (spec. surface resistivity < 1 Ohm). Conductive PE is used for ex- ample for shelves of Mini Desiccators or for Conductive Cable lead-ins. As the ma- terial has a temperature application area from -20°C to +80 °C, its applications are limited to “extended room temperature”. The material is flammable and should not come into contact with open flames.
White PBTP
A typical application for this ther- moplastic Polybutylenterephtalate
(PBTP) material are Silica Gel Trays in laboratories. It is characterized by a low moisture absorption (0,2 - 05 percent
by weight), a high mechanical strength, shock resistance due to good impact strength and very good electrical insula- tion properties (spec. contact resistance > 1013 Ohm x cm). Trays made of natural PBTP retain their shape up to approx. +165 °C. The material is flammable and should, therefore, not come into contact with open flames. It is resistant to diluted acids and bases at ambient temperature, alcohols, hydrocarbons, ketones, ether, mineral oils, fuels and saline solutions.
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Information on function and safety of dischargeable plastics and elastomers
Plastics and elastomers are characterized by good thermal and electrical insulation properties. If the application requires conductive (=high conducti- vity) respectively dischargeable properties (lower conductivity is sufficient), this will be achieved through the addition of sooty particles. Dischargeable plastics are used to avoid ignition sources through electrostatic charging (see ATEX regulation). In other applications, it protects electronic components from voltage peaks through electrostatic charging. The additional material of the sooty particles is not stable to strong oxidative attacks. In case of contact with aerial oxygen, the dischargeable properties of the plastic or the elastomers do not change. However, strongly oxidizing media such as ozone (O3), hydrogen peroxide (H2O2) or strongly oxidizing acids (concentrated HNO3) decompose the sooty particles so that the electrostatic chargeability
is lost. This can be recognized on the weakening of the originally black color of the parts. Through examination of the surface resistance (in Ω as per IEC 60093) respectively the contact resistance (in Ω*cm as per IEC 60093), this filler diminution can be monitored quantitively. If the chargeability falls below the specificied values after a period of time, the component should be replaced by a new one. The original component safety is no longer given.
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Materials