Fatih GÜNDÜZ 030060144 11st Week Bonus Words Answers

Thermoset elastomers : (New) (Material)
   Thermoset elastomers can possess varied degrees of unsaturation within their backbone. Unsaturation permits the reactivity required for polymerization and cross-linking. Subsequently, as unsaturation increases, resistance to degradation decreases. The addition of functional side groups to an elastomer can attribute properties not inherent to the parent polymers. For example, elastomers that have oxygen incorporated into their backbone tend to have better low-temperature properties than those that contain only carbon-hydrogen bonds. These heteroatom side chains may also provide reactive cure sites on the backbone of an otherwise saturated polymer.
   Saturated rubbers, for example, ethylene propylene copolymer, tend to be less reactive and more chemically resistant than polymers having higher diene content or those bearing functional side groups, for example, ethylene propylene diene ter-polymer. Because of their innate impermeability to gases, superior heat resistance, and good chemical resistance, formula compositions containing saturated elastomers are the best choice for closures used in parenteral applications.
(Leachables and Extractables Handbook: Safety Evaluation, Qualification, Cheryl L. M. Stults,Lee M. Nagao, P.205)

THERE IS NO OLD DEFİNİTİON !!!


Thermoplastic elastomers : (New) (Material)
Thermoplastic elastomers are a series of synthetic polymers that combine the properties of vulcanized rubber with the processing advantages of conventional thermoplastics. In other words, they allow the production of rubberlike articles using the fast processing equipment developed by the thermoplastics industry.
There arc many different of thermoplastic elastomers, and details of their composition. properties, and applications have been extensively covered in the literature [22-29]. The commercially available materials used in injection molding can be classified into 10 types (Table 2.6). The commonly used abbreviations are listed in Tabic 2.7. The various thermoplastic elastomers are discussed in more detail later in this chapter.
Before dealing with each type individually, we can consider some features that thermoplaslic elastomers have in common. Most thermoplastic elastomers listed in Table 2.6 have one feature in common: They are phase-separated systems (i.e., the chlorinated olefin interpolymer alloys are the exception). One phase is hard and solid at room temperature in these phase-separated systems. The polymer forming the hard phase is the one listed first in this table. Another phase is an elastomer and fluid. The hard phase gives these thermoplastic elastomers their strength. Without it, the elastomer phase would be free to flow under stress and the polymers would be unusable. When the hard phase is heated, it becomes fluid. Flow can then take place, so the thermoplastic elastomer can be molded. Thus, the temperature at which the hard phase becomes fluid determines the processing temperature required for molding.
(Injection Molding Handbook, Tim A. Osswald,Lih-Sheng Turng,Paul J. Gramann, p.53)


 

THERE IS NO OLD DEFİNİTİON !!!