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Chapter 14: Problem 8

High-density polyethylene may be chlorinated by inducing the random substitution of chlorine atoms for hydrogen. (a) Determine the concentration of \(\mathrm{Cl}\) (in wt\%) that must be added if this substitution occurs for \(8 \%\) of all the original hydrogen atoms. (b) In what ways does this chlorinated polyethylene differ from poly(vinyl chloride)?

Short Answer

Expert verified
Answer: The concentration of Cl in HDPE when 5% of the hydrogen atoms are replaced by chlorine atoms can be calculated using the molecular weight of chlorinated HDPE and the weight percent of Cl. Chlorinated polyethylene (CPE) differs from poly(vinyl chloride) (PVC) in their structure and properties. While both contain chlorine in their polymer chains, CPE retains some of the original HDPE properties due to partial substitution, whereas PVC has distinct properties due to the regular presence of chlorine atoms. PVC is more rigid and has better resistance to chemicals and weathering, in contrast, CPE offers better flexibility, processability, and resistance to heat and continuous stress.

Step by step solution

01

Determine the molecular weight of high-density polyethylene (HDPE) and hydrogen

The repeating unit of HDPE is C2H4, and we will find its molecular weight (M). We'll use the molar masses of carbon (C) and hydrogen (H) which are 12.01 g/mol and 1.01 g/mol, respectively. MolecularWeight_HDPE = (C_molar_mass x 2) + (H_molar_mass x 4)
02

Calculate the molecular weight of HDPE with 5% hydrogen substitution

We need to determine the molecular weight of the new HDPE with 5% of its hydrogen atoms replaced by chlorine atoms (Cl). The molar mass of chlorine (Cl) is 35.45 g/mol. We will replace 0.05 x 4 H atoms with Cl atoms: MolecularWeight_ChlorinatedHDPE = (C_molar_mass x 2) + (H_molar_mass x (4 - (0.05 x 4))) + (Cl_molar_mass x (0.05 x 4))
03

Calculate the weight percent of Cl in chlorinated HDPE

To find the weight percent of Cl in the chlorinated HDPE, we will use the following formula: Weight_percent_Cl = (Total weight of Cl atoms / MolecularWeight_ChlorinatedHDPE) x 100
04

Discuss the differences between chlorinated polyethylene and poly(vinyl chloride)

Chlorinated polyethylene (CPE) and poly(vinyl chloride) (PVC) both contain chlorine in their polymer chains, but their structures and properties are different. In CPE, only some of the hydrogen atoms are replaced by chlorine, whereas in PVC, the chlorine directly replaces one of the hydrogen atoms on every carbon atom. CPE retains some of the original HDPE properties, whereas PVC has distinct properties due to the regular presence of chlorine atoms. PVC is more rigid and has better resistance to chemicals and weathering, but CPE can have better flexibility, processability and can be more resistant to heat and continuous stress due to its HDPE-like properties.

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Most popular questions from this chapter

A random poly(styrene-butadiene) copolymer has a number-average molecular weight of \(350,000 \mathrm{g} / \mathrm{mol}\) and a degree of polymerization of 5000 . Compute the fraction of styrene and butadiene repeat units in this copolymer.

The density and associated percent crystallinity for two polypropylene materials are as follows: $$\begin{array}{cc} \hline \rho\left(g / c m^{3}\right) & \text {Crystallinity (\%)} \\ \hline 0.904 & 62.8 \\ 0.895 & 54.4 \\ \hline \end{array}$$ (a) Compute the densities of totally crystalline and totally amorphous polypropylene. (b) Determine the density of a specimen having \(74.6 \%\) crystallinity.

Sketch portions of a linear polypropylene molecule that are (a) syndiotactic (b) atactic, and (c) isotactic.

Make comparisons of thermoplastic and thermosetting polymers (a) on the basis of mechanical characteristics upon heating, and (b) according to possible molecular structures.

(a) Is it possible to grind up and reuse phenol-formaldehyde? Why or why not? (b) Is it possible to grind up and reuse polypropylene? Why or why not?
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