Environments affecting durability temperature

New technological processes closely related with aggressive environments require increases in the manufacture of durable and effective composite materials that can withstand hostile media. Corrosion, the negative effects of radiation and temperatures, high UV radiation, and other adverse natural and anthropogenic effects on building structures are real problems that affect the human living environment. 

Durability of adhesive materials is affected by environmental factors. The specific environments of concern are (1) extreme high temperatures, (2) extreme low temperatures, (3) extreme high humidity, (4) salt water, (5) fire, (6) corrosive gases or liquids, and (7) external stresses. A detailed discussion of the first five factors is given. Future research needs about these factors are also suggested. 

Discriminating between the various effects of heat and moisture on the strength of cyanoacrylate metal-to-metal bonds is not easy. The environment can affect the adhesive, the metal surface, or the interface between them. The reduction in strength may be due to heat alone, or to water, or to both. The most durable adhesive possible today would probably contain a room temperature active crosslinking agent and an adhesion promoter resistant to both heat and moisture. Table XII lists the water durability modifiers discussed in this section. 

In the earlier chapters, various authors have provided basic issues regarding the mechanical and physical properties of composites. An issue that may not have been fully covered, which could be considered as an important factor affecting the durability of pipes and risers made of composite, is the issue of long-term durability of GFRP when in contact with an aqueous environment, especially in the presence of relatively high temperatures. GFRP pipes and risers are subjected to harsh environments the environments... 

However, other approaches have also successfully been adopted. For example, Dickie and Ward [53] have studied single-lap joints exposed to a high humidity at moderately elevated temperatures but maintained a constant stress on the joints. Also, periodically the joints were removed from the high-humidity environment and exposed to a salt solution for a short time period. Using this accelerated-ageing test they were able to rank the durability performance of various adhesive systems in a comparatively short timescale. Further, they reported that not only were the kinetics of mechanisms of environmental attack accelerated, but also the exact details of the mechanisms were affected by the levels of the applied load. For example, for joints which consisted of bonded galvanised steel substrates, the effect of relatively high applied loads was to prevent the formation of an effective barrier of corrosion products, i.e. passivation of the substrate surface was prevented. This allowed the electrochemical corrosion process to proceed unimpeded, and hence at a faster rate than for similar, but unstressed, joints. Thus,... 

An ever-present issue when working with plastics and elastomers is that nearly every one of them is affected by chemicals upon exposure. A chemical environment often poses one of the most demanding tests of a polymer s durability. There are two basic ways that a chemical can affect a polymer chemical and physical. The extent of the impact of the chemicals varies based on a variety of factors. Foremost among these factors are the chemical structure and composition of the polymers, and the properties of the impacting chemical. Increasing the temperature of the environment compounds the effects. There are other factors that influence the severity of the effect of chemicals on plastics and rubbers, which are described in this chapter. 

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