Chemical resistance immersion tests

Table 4.118 displays some examples concerning the swelling (%) after immersion in various chemicals for 7 days. Negative figures correspond to a decrease in the sample volume. These results relate to some grades only and cannot be generalized. Furthermore, swelling alone is not sufficient to estimate the chemical resistance. Complementary tests are needed. 

ISO 4433 1984 Polyolefin pipes - Resistance to chemical fluids - Immersion test method -System for preliminary classification. 

ISO 4433 [245] Polyolefin pipes Resistance to chemical fluids Immersion test method System for preliminary classification... 

In many commercial brochures, chemical resistance is indicated as excellent, good, fair, or poor. Although the test method is usually outlined, wide interpretation is possible. Immersion tests are usually described in this manner. Hydrolytic stabiUty is tested by salt-spray cycling or autoclave cycling. 

The principal test to establish the chemical resistance of the polymeric landfill liners to liquid wastes and industrial effluents is the immersion of geomembrane in a sample either of a defined chemical mixture or of a leachate from an existing storage site. This is performed either at various elevated temperatures in order to generate an Arrhenius diagram, or at fixed temperatures of 50 °C and at 20 °C, and is followed by a number of, primarily, mechanical evaluation tests. 

Results concerning chemical resistance relate to short immersions at various temperatures that are not representative of long-term exposures. Moreover, most conditions are unknown and some results appear conflicting. The following estimations must be treated with particular caution. These general indications should be verified by consultation with the producer and by tests under operating conditions. General chemical properties are subject to the compatibility of the fillers and reinforcements with the ambient conditions. K the fillers are well adapted, the chemical properties are the same for filled and neat polymers. 

The classic test for chemical resistance (ASTM D-543) measures the percentage weight change of test samples after immersion in different liquid systems. Tests for chemical resistance have been extended to include changes in mechanical properties after immersion. Since chemical attack involves changes in chemical structure, it can be readily observed by many instrumental methods that measure chemical structure, in particular, surface structure. 

Though a standard norm or absolute reference value is not available for comparison in any of the international standard specifications and the technical and research publications with respect to the chemical resistance properties of rubber, liquid immersion tests certainly provide relative and useful data with which the suitability of anticorrosive rubber lining compounds can be assessed with a fair degree of accuracy. For this reason manufacturers and applicators of rubber lining resort to tests under simulated conditions instead of accelerated ageing immersion or swelling tests. 

Immersion testing - Commonly used to determine the resistance of tank lining compounds to various chemicals. See ASTM D-471-Test Method for Rubber Property-Effect of Liquids. 

By spot-tests on coatings and immersion-tests on castings the excellent chemical-resistance of phenalkamine-cured epoxy systems has been demonstrated. In addition, near-infrared cure studies have documented the rapid complete cure of epoxies at room temperature and also satisfactory cure at reduced temperatures when phenalkamines are used as the curing agents. 

Because many polymers are resistant to attack by corrosives, tests for chemical resistance of polymers are particularly important. ASTM-D-543-67 (1977) measures weight and dimensional changes of test samples immersed for 7 days in many different test solutions. These tests may be coupled with tensile tests. Other ASTM tests include those under accelerated service conditions [ASTM-D756-76 (1971)], water absorption [ASTM-D570-63 (1972)], and environmental stress cracking of ethylene plastics [(ASTM-D1693-70)]. 

Air Product and Chemicals, Inc. (USA) have found out that (in the absence of any topcoat) while the doped electrically conductive form of PAni performed well as a corrosion-resistant coating for carbon steel, the undoped, nonconductive form of PAni performed better. This was determined by electrochemical impedance spectroscopy (EIS), immersion testing (3wt % NaCl) and salt fog testing. Perfect performance of undoped PAni could be understood as follows. From the high pore-resistance value observed (2-10 U) it can be concluded that PAni forms a dense, adherent, low porosity film on carbon steel. Such a film would restrict the access of components required for corrosion to occur ... 

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