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All materials have advantages and disadvantages inherent in their properties. Whether or not the material is acceptable for a specific application becomes an evaluation of the trade-offs between these advantages and disadvantages when compared to other materials. Thermoplastics incorporate a broad family of materials with a wide spectrum of physical properties. However, plastics in general have some limitations that are consistent for most of them.
Thermoplastics have a limited temperature spectrum for applications, especially when compared to metals. Some plastics start to see a significant loss of strength at temperatures as low as 93.3 degrees Celsius, and there are few plastics that will perform well above 260 degrees Celsius. If a plastic suffers deformation while at elevated temperatures, it rarely returns to its original condition.
Many plastics begin to soften or lose other properties when exposed to organic solvents. Plastics are carbon-based chains, and organic solvents tend to attack the chemical bonds that keep the chains bound to each other. Plastics that do tend to perform better when exposed to solvents are likely to perform poorly when exposed to other chemicals, especially acids.
Direct sunlight degrades the chemical bonds in polymers over time. Plastics that experience significant UV exposure become brittle and break apart easily under even minor impacts. Although there are some UV mitigating additives that can be blended with plastics, they only delay the inevitable rather than eliminate the issue completely.
Thermoplastics can leach out minute amounts of organic chemicals into liquid over time. Some of these chemicals can be hazardous. There are already concerns in society about the long-term effects of exposure to chemicals that leach out of plastic water bottles or other plastic containers.
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