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Chapter 15: Problem 31

Name the following polymer(s) that would be suitable for the fabrication of cups to contain hot coffee: polyethylene, polypropylene, poly(vinyl chloride), PET polyester, and polycarbonate. Why?

Short Answer

Expert verified
Answer: PET polyester and polycarbonate are the most suitable polymers for making cups to contain hot coffee. Both have good chemical resistance, high thermal resistance, and high impact strength, making them ideal for holding hot beverages without deforming or breaking. Polypropylene could potentially be used, but PET polyester and polycarbonate are more suitable due to their higher thermal resistance.

Step by step solution

01

List the properties of each polymer in brief

Polyethylene: Low cost, good chemical resistance, low melting point (80-130°C) Polypropylene: Good chemical resistance, good thermal resistance, melting point (130-170°C) Poly(vinyl chloride): Good chemical resistance, good thermal resistance, but toxic when heated PET polyester: Good chemical resistance, good thermal resistance, melting point (250-260°C) Polycarbonate: Good chemical resistance, excellent thermal resistance, high impact strength, melting point (267–327°C)
02

Eliminate polymers with low melting points

Since hot coffee has a temperature of about 80–90°C, we can eliminate polyethylene due to its low melting point, which would make the cup soften or deform when holding hot coffee.
03

Eliminate polymers with toxic properties when heated

Poly(vinyl chloride) releases toxic fumes when heated, which is not ideal for a hot coffee cup. Thus, we exclude poly(vinyl chloride) from the list of suitable polymers.
04

Consider thermal resistance and other properties

Both PET polyester and Polycarbonate have good thermal resistance, with melting points (250-260°C) and (267–327°C) respectively, making them suitable for holding hot coffee. Additionally, both have good chemical resistance and high impact strength, which are ideal properties for a coffee cup (preventing cracking or shattering).
05

Select the most suitable polymer(s)

Based on the properties discussed above, the best polymers for fabricating cups to contain hot coffee would be the PET polyester and polycarbonate. Both have good chemical resistance, high thermal resistance, and high impact strength, making them ideal for holding hot coffee without deforming or breaking. Polypropylene could potentially be used, but PET polyester and polycarbonate are more suitable due to their better thermal resistance.

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Most popular questions from this chapter

Nylon 6,6 may be formed by means of a condensation polymerization reaction in which hexamethylene diamine \(\left[\mathrm{NH}_{2}-\left(\mathrm{CH}_{2}\right)_{6}-\right.\) \(\mathrm{NH}_{2}\) ] and adipic acid react with one another with the formation of water as a by-product. What masses of hexamethylene diamine and adipic acid are necessary to yield \(37.5 \mathrm{~kg}\) of completely linear nylon 6,6 ? (Note: the chemical equation for this reaction is the answer to Concept Check 15.12.)

For some viscoelastic polymers that are subjected to stress relaxation tests, the stress decays with time according to $$ \sigma(t)=\sigma(0) \exp \left(-\frac{t}{\tau}\right) $$ where \(\sigma(t)\) and \(\sigma(0)\) represent the timedependent and initial (i.e., time \(=0\) ) stresses, respectively, and \(t\) and \(\tau\) denote elapsed time and the relaxation time; \(\tau\) is a timeindependent constant characteristic of the material. A specimen of a viscoelastic polymer whose stress relaxation obeys Equation \(15.10\) was suddenly pulled in tension to a measured strain of \(0.6\); the stress necessary to maintain this constant strain was measured as a function of time. Determine \(E_{r}(10)\) for this material if the initial stress level was \(2.76\) MPa (400 psi), which dropped to \(1.72 \mathrm{MPa}\) (250 psi) after \(60 \mathrm{~s}\).

In Figure 15.28, the logarithm of \(E_{r}(t)\) versus the logarithm of time is plotted for polyisobutylene at a variety of temperatures. Make a plot of \(E_{r}(10)\) versus temperature and then estimate its \(T_{g}\).

List the two molecular characteristics that are essential for elastomers.

In your own words, describe the mechanisms by which semicrystalline polymers (a) elastically deform and (b) plastically deform, and (c) by which elastomers elastically deform.
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