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Chapter 14: Problem 14

(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?

Short Answer

Expert verified
Why or why not? Answer: No, it is not possible to grind up and reuse phenol-formaldehyde. This is because it is a thermosetting polymer with a cross-linked structure and covalent bonds, which do not allow it to be re-melted or reshaped when exposed to high temperatures. Question: Is it possible to grind up and reuse polypropylene? Why or why not? Answer: Yes, it is possible to grind up and reuse polypropylene. This is because it is a thermoplastic polymer with weaker intermolecular forces, allowing for the chains to slide past one another when heated. As a result, polypropylene can be easily melted, reshaped, and reprocessed for the creation of new products.

Step by step solution

01

Understanding the structure of phenol-formaldehyde

Phenol-formaldehyde is a type of thermosetting polymer. Thermosetting polymers are made up of a network of long chains that are cross-linked with covalent bonds, meaning that once the material is set and hardened, the bonds cannot be easily broken or reformed.
02

Grinding and reusing phenol-formaldehyde

Due to the cross-linked structure and covalent bonds within phenol-formaldehyde, it cannot be easily re-melted or reshaped. When exposed to high temperatures, it becomes infusible and does not soften. As a result, grinding up and reusing phenol-formaldehyde is not possible, as the material's structural properties prevent it from returning to a moldable or processable state.
03

Understanding the structure of polypropylene

Polypropylene is a type of thermoplastic polymer. Thermoplastic polymers have long chains without cross-linking, and when exposed to heat, they can soften and become moldable. Unlike thermosetting polymers, thermoplastics have weaker intermolecular forces, allowing for the chains to slide past one another when heated.
04

Grinding and reusing polypropylene

Polypropylene's thermoplastic properties allow it to be easily melted and re-molded when exposed to heat. This means that, when ground up, polypropylene can be reprocessed and used in the creation of new products. As a result, grinding and reusing polypropylene is possible and commonly done in the plastic industry for recycling purposes.

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Most popular questions from this chapter

Consider the diffusion of oxygen through a low(- density polyethylene (LDPE) sheet \(15 \mathrm{~mm}\) thick. The pressures of oxygen at the two faces are 2000 \(\mathrm{kPa}\) and \(150 \mathrm{kPa}\), which are maintained constant. Assuming conditions of steady state, what is the diffusion flux [in \(\left.\left(\mathrm{cm}^{3} \mathrm{STP}\right) / \mathrm{cm}^{2} \cdot \mathrm{s}\right]\) at \(298 \mathrm{~K}\) ?

Compute repeat unit molecular weights for the following: (a) polytetrafluoroethylene (b) poly(methyl methacrylate) (c) nylon 6,6 (d) poly(ethylene terephthalate)

Sketch cis and trans structures for (a) polybuta( ) diene and (b) polychloroprene. Use two-dimensional schematics per footnote 12 of this chapter.

The permeability coefficient of a type of small ( gas molecule in a polymer is dependent on absolute temperature according to the following equation: $$ P_{M}=P_{M_{0}} \exp \left(-\frac{Q_{p}}{R T}\right) $$ where \(P_{M_{0}}\) and \(Q_{p}\) are constants for a given gaspolymer pair. Consider the diffusion of water through a polystyrene sheet \(30 \mathrm{~mm}\) thick. The water vapor pressures at the two faces are 20 \(\mathrm{kPa}\) and \(1 \mathrm{kPa}\), which are maintained constant. Compute the diffusion flux [in(cm \(\left.\left.^{3} \mathrm{STP}\right) / \mathrm{cm}^{2} \cdot \mathrm{s}\right]\) at \(350 \mathrm{~K}\) ? For this diffusion system, $$ \begin{aligned} &P_{M_{0}}=9.0 \times 10^{-5}\left(\mathrm{~cm}^{3} \mathrm{STP}\right)(\mathrm{cm}) / \mathrm{cm}^{2} \cdot \mathrm{s} \cdot \mathrm{Pa} \\ &Q_{p}=42,300 \mathrm{~J} / \mathrm{mol} \end{aligned} $$ Assume a condition of steady-state diffusion.

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