This preview shows pages 1–2. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.View Full Document
Unformatted text preview: d) What is the glass transition temperature?. The glass transition temperature is the temperature at which the Van der Waals bonds melt. It is the temperature at which the elastic properties drop dramatically in thermoplastics. e) Explain the change in moduli of polymers at the glass transition temperature. The Van der Waals bonds “melt” at this temperature, i.e. the thermal vibration exceeds the ability of the bonds to hold the molecules together. Thermoplastics rely on Van der Waals bonds for their elastic response at low temperatures. If these bonds are removed,then the polymer behaves viscoelastically, with the elastic component coming from entanglements between the polymer chains. f) What is the range of temperature in which T G lies for most engineering polymers?. 100-500 K. g) How would you increase the modulus of a polymer? Introduce covalent cross-links. Increase degree of crystallinity. Increase alignment of polymer chains....
View Full Document