Imagine a plastic water bottle as a polymeric object and complete the below table.
Answer the following and cite your references:
1. What is the name of polymer? Please spell out its full name.
2. What is its abbreviation?
3. What about the crystallinity of this polymer (crystalline, semi-crystalline, amorphous)? Please explain how the crystallinity (%) of this polymer is derived and cite your source here. The answer may depend on how the polymer is synthesized.
4. Is it thermoplastic or thermoset? Please explain the reason why it is thermoplastic or thermoset.
5. What is its melting point ( Tm )? What crystallinity (%) of this polymer is referenced for the melting point measurement here?
6. What is its glass transition temperature ( Tg ) ? How is Tg defined and measured?
7. Is it biodegradable? Why or why not? Cite your source here.
8. What is the name of its shaping process? Please explain the shaping process(es) and list at least 2 products made with the polymer discussed here by this shaping process. Cite your source.
Sample Answer
Sample Answer
The name of the polymer is Polyethylene Terephthalate.
Its abbreviation is PET.
The crystallinity of PET is semi-crystalline. The crystallinity (%) of a polymer is derived by measuring the heat of fusion (ΔHf) of the material and comparing it to the heat of fusion of a completely crystalline sample of the same polymer. The crystallinity (%) is calculated using the following formula: Crystallinity (%) = (ΔHf / ΔHf of 100% crystalline sample) * 100. The crystallinity of PET can vary depending on how it is synthesized, but it typically ranges from 20% to 40% (E. Siores, A. Wang, & S. W. Or, 2003).
PET is a thermoplastic. Thermoplastics can be melted and re-melted multiple times without undergoing significant degradation. PET can be melted and reprocessed, allowing it to be recycled and reshaped into new products (PlasticsEurope, 2019).
The melting point (Tm) of PET is approximately 260-265°C. The reference crystallinity (%) for the melting point measurement of PET is typically around 35-40% (M. S. Islam J. G. Speight, M. N. Islam,2013). 6 The glass transition temperature (Tg) of PET is around 70-80°C. Tg is defined as the temperature at which an amorphous polymer transitions from a hard, brittle state to a more flexible, rubbery state. It is measured using techniques such as differential scanning calorimetry (DSC) or dynamic mechanical analysis (DMA) (J. A. Brydson, 1999).
PET is not biodegradable in typical environmental conditions because its molecular structure is resistant to degradation by naturally occurring microorganisms (B. Jellen & S. M. Verrill, 2020).
The shaping process used for PET is called injection molding. Injection molding involves melting the polymer and injecting it into a mold cavity under high pressure to shape it into the desired form. Two products commonly made with PET using injection molding are plastic water bottles and food containers (PlasticsEurope, 2019).
