Effects of Fabrication Processes

In summary, the final properties of thermoplastic articles depend both on the molecular structure of the polymer and on the details of the fabrication operations. This is a disadvantage, in one sense, since it makes product design more complicated than with other materials that are less history-dependent. On the other hand, this feature confers an important advantage on plastics because fabrication particulars are additional parameters that can be exploited to vary the costs or balance of properties of the products. 

Nylon-6,6 can be made into articles with tensile strengths around 12,000 psi or into other articles with tensile strengths around 120,000 psi. What is the basic difference in the processes used to form these two different articles Why do poly isobutene properties not respond in the same manner to different forming operations  

Suggest a chemical change andVor a process to raise the softening temperature of articles. 

Which of the following polymers would you expect to have a lower glass transition temperature Which would have a higher melting point Explain why. (Assume equal degrees of polymerization.) 

A rubber has a shear modulus of 10 dyn/cm and a Poisson s ratio of 0.49 at room temperature. A load of 5 kg is applied to a strip of this material which is 10 cm long, 0.5 cm wide, and 0.25 cm thick. How much will the specimen elongate  

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Several tests have been developed over the years to determine the crevice corrosion resistance of alloys. The objectives of these tests include comparison of alloys, qualification of alloys for a given service, evaluation of the effects of fabrication processes on crevice corrosion resistance, quality control, and life prediction. This chapter will briefly describe the types of tests, and their applicability and limitations, with a focus on tests that have been or are now being considered by ASTM Committee G-1 on Corrosion of Metals. While these test principles are applicable to a wide variety of alloys, the information presented is focused on stainless and nickel-base alloys. 

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