Susceptibility of plastics

The literature is replete with studies relating to the microbial susceptibility of plasticizers to both fungi and bacteria, and a recent article, describing work by Soviet scientists, suggests that this particular problem does not stop at national boundaries (4). Indeed, microbial degradation has been reported from the equator to the Arctic Circle, on items ranging from those beneath the sea to those orbiting the earth. 

Impact resistance Relative susceptibility of plastics to fracture by shock, e.g., as indicated by the energy expended by a standard pendulum type impact machine in breaking a standard specimen in one blow. 

Pantke, M., 1977, Test methods for evaluation of susceptibility of plasticized PVC and its components to microbial attack, in Walters, A.H. ed. Biodeterioration Investigation Techniques, 51 - 76. Applied Science, London,... 

For many years, the actinomycetes Stv. reticulum had been used as a screening organism in the testing of the susceptibility of plastics. The test adopted by ASTM (American Society for Testing Materials) in recent years utilizing this microorganism is designated as ASTM E-1428-96 (ASTM, 1996). 

Table 6.3 Susceptibility of Plasticizers to Microbial Attack Highly susceptible types...

Thus, an increase in temperature may either increase or reduce the susceptibility of plastics to corona. 

ASTM tests G21-70 and G22-76. Higher numbers are considered to correlate with the susceptibility of the plastic to biodegradation. 

Whereas coiTosion of metals is due to chemical or substantial electrochemical attack, the deterioration of plastics and other non-metals which are susceptible to swelling, cracking, crazing, softening etc. is essentially physicochemical rather than electrochemical. 

There are some aspects in the raw dry NR grades for adhesive manufacturing to be considered. NR tends to suffer oxidative degradation catalyzed by metals (mainly copper). The susceptibility of NR to oxidation can be measured using the plasticity retention index. The better grades of rubber have the higher plasticity retention index. 

In addition to the alloy compositions being of importance with regard to susceptibility to stress-corrosion cracking, the resistance of the alloy can be altered by microstructural factors. Hanninen has reviewed the available literature quite thoroughly and has concluded that a fine grain size is likely to be beneficial. Strain imposed prior to use tends to be deleterious because deformed material usually acts anodic with respect to unstrained material and because the introduction of plastic deformation may also... 

Susceptibility of Metals to Attack by Contaminants from Plastics... 

Environmental stress cracking is the cracking of certain plastic products that becomes exposed to a chemical agent while it is under stress. This effect may be caused by exposure to such agents as cleaners or solvents. The susceptibility of affected plastics to stress cracking by a particular chemical agent varies considerably among plastics, particularly the TPs. 

Part of the wide acceptance of plastics is from their relative compatibility to chemicals as compared to that of other materials. Because plastics are largely immune to the electrochemical corrosion to which metals are susceptible, they can frequently be used profitably to contain water and corrosive chemicals that would attack metals. Plastics are often used in corrosive environments for... 

Nomnetallics As stated, corrosion of metals apphes specifically to chemical or electrochemical attack. The deterioration of plastics and other nonmetallic materials, which are susceptible to sweUing crazing, cracking, softening, and so on, is essentially physiochemical rather than electrochemical in nature. Nonmetallic materials can either be rapidly deteriorated when exposed to a particular enviromnent or, at the other extreme, be practicidly unaffected. Under some conditions, a nonmetallic may show evidence of gradual deterioration. However, it is seldom possible to evaluate its chemical resistance by measurements of weight loss alone, as is most generally done for metals. 

Since it measures the susceptibility of materials to plastic deformation (as contrasted with elastic deformation), hardness is very important for diagnosing the mechanical state of a material, in particular toughness. Purely elastic materials are brittle. Plasticity, by blunting cracks and other defects, allows metals and, to some extent ceramics, to tolerate small flaws and thereby become malleable and tough. 

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