Thermosetting Polymers Quiz

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Questions and Answers

Which characteristic distinguishes thermosetting polymers from thermoplastics during heating?

Thermosets soften and flow during initial heating. (correct)

Thermosets are capable of repair after hardening.

Thermosets can be reheated and molded multiple times.

Thermosets remain a liquid state indefinitely.

What happens to thermosetting polymers when they are reheated?

They revert to their liquid state.

They degrade and char. (correct)

They soften and become pliable.

They maintain their solid form.

What percentage of the tonnage of all synthetic polymers produced do thermoplastics account for?

50%

70% (correct)

30%

90%

Which of the following is an example of a thermosetting polymer?

Phenolics Signup and view all the answers

Which of the following polymers is NOT classified as a thermoplastic?

Epoxies Signup and view all the answers

How do thermoplastics and thermosets compare in terms of market share?

Thermoplastics account for about 70%, thermosets and elastomers share the remaining 30%. Signup and view all the answers

What is the typical specific gravity of polymers?

1.2 Signup and view all the answers

What is the key symbol used to represent thermosetting polymers?

TS Signup and view all the answers

What characteristic of thermoplastics makes them suitable as electrical insulators?

Insulating electrical properties Signup and view all the answers

Which of the following statements is true regarding the usage of polymers compared to metals?

Current polymer usage exceeds that of metals on a volumetric basis. Signup and view all the answers

What is a key feature of thermosetting polymers?

They become a large macromolecule during curing. Signup and view all the answers

Which of the following is NOT a commercial form of thermoplastic products?

Ceramics Signup and view all the answers

Which property of thermoplastics is typically higher than that of metals and ceramics?

Coefficient of thermal expansion Signup and view all the answers

How are starting plastic materials for thermoplastics typically supplied to fabricators?

In powders or pellets Signup and view all the answers

What happens to a thermosetting polymer during the curing process?

It forms a network of covalent bonds. Signup and view all the answers

Which thermoplastic product is commonly used for protective covering?

Films and sheets Signup and view all the answers

What is a significant reason why polymers are important in manufacturing?

They can be molded into complex shapes without further processing. Signup and view all the answers

Which characteristic is typical of thermoplastic polymers?

They can only have a linear or branched structure. Signup and view all the answers

How does branching in polymer structures affect their properties?

It increases entanglement among molecules, making them stronger. Signup and view all the answers

In terms of energy production, polymers are generally:

Less energy-intensive to produce than metals. Signup and view all the answers

Which of the following statements is true regarding the cost-effectiveness of polymers?

Polymers are cost competitive with metals on a volumetric basis. Signup and view all the answers

What property is NOT associated with plastics used in manufacturing?

They are stronger than all forms of metals. Signup and view all the answers

What is a defining feature of tightly cross-linked or networked polymer structures?

They are associated with thermosetting polymers. Signup and view all the answers

When comparing polymers to metals, which of the following is generally true?

Polymers typically have a lower manufacturing energy requirement. Signup and view all the answers

What is the primary function of the reinforcing phase in composite materials?

To enhance the properties of the matrix material Signup and view all the answers

Which of the following is an example of a Ceramic Matrix Composite (CMC)?

Al2O3 with fibers Signup and view all the answers

What role does the matrix material play in composite materials?

It conceals the reinforcing phase while providing structural support. Signup and view all the answers

Which of the following shapes is NOT commonly found in the reinforcing phase of composite materials?

Plates Signup and view all the answers

Which type of composite is formed from polymer resins embedded with reinforcing agents?

Polymer Matrix Composites (PMCs) Signup and view all the answers

How does the matrix material behave under applied load?

It shares the load with the reinforcing phase. Signup and view all the answers

What is a key characteristic of Metal Matrix Composites (MMCs)?

They are mixtures of ceramics and metals. Signup and view all the answers

What is the generic term often used for the secondary phase in composite materials?

Reinforcing agent Signup and view all the answers

What is one primary benefit of using a sandwich structure with a foam core?

High strength-to-weight ratio Signup and view all the answers

Which of the following best describes FRPs?

Multi-layered, fiber-reinforced plastic Signup and view all the answers

What is a common use for printed circuit boards?

Providing electrical conductivity Signup and view all the answers

What is one advantage of using honeycomb cores in sandwich structures?

Optimized stiffness-to-weight ratio Signup and view all the answers

Which component is NOT typically found in the composition of automotive tires?

Fiber-reinforced plastics Signup and view all the answers

What property do laminated composite structures such as windshield glass provide?

Resistance to shattering Signup and view all the answers

Which material is commonly associated with sandwich structures for enhancing lightweight design?

Low density foam Signup and view all the answers

What is a significant characteristic of laminar composite structures?

Involve bonding multiple layers together Signup and view all the answers

Study Notes

Thermosetting Polymers (TS)

Characterized by highly cross-linked, three-dimensional, covalently bonded structures.
Chemical reactions during cross-linking are called curing or setting.
After curing, the formed part becomes one large macromolecule.
Always amorphous and exhibit no glass transition temperature.
Symbolized by 'TS' and cannot tolerate repeated heating cycles.

Market Shares

Thermoplastics dominate commercially with around 70% of the market share.
Thermosets and elastomers share the remaining 30%, with a slight advantage for thermosets.
Polymers exceed metals in volumetric use.

Examples of Polymers

Thermoplastics include:
- Polyethylene
- Polyvinylchloride
- Polypropylene
- Polystyrene
- Nylon
Thermosets include:
- Phenolics
- Epoxies
- Certain polyesters

Reasons Why Polymers are Important

Plastics can be molded into complex shapes, often with no further processing.
On a volumetric basis:
- Polymers are cost-competitive with metals.
- Polymers generally require less energy to produce than metals.
- Some plastics are translucent or transparent, making them competitive with glass for some applications.

Polymer Structures

Linear structure is the fundamental type for thermoplastics.
Branched structure is another common type found in thermoplastics.
Tightly cross-linked or networked structure is characteristic of thermosets.

Effect of Branching on Properties

Thermoplastics have linear or branched structures, or a mixture of both.
Branching increases entanglement among molecules, leading to:
- Increased strength in the solid state.
- Increased viscosity at a given temperature in the plastic or liquid state.

Physical Properties of Thermoplastics

Thermoplastics have lower densities than metals or ceramics.
- Polymers have a specific gravity of around 1.2.
- Ceramics have a specific gravity of around 2.5.
- Metals have a specific gravity of around 7.0.
Thermoplastics have a higher thermal expansion coefficient than metals or ceramics:
- Approximately five times the value for metals and ten times the value for ceramics.
Thermoplastics have a much lower melting temperature than metals and ceramics.
Thermoplastics are electrically insulating.
Thermoplastics have a higher specific heat than metals and ceramics.

Commercial Thermoplastic Products and Raw Materials

Thermoplastic products include:
- Molded and extruded items.
- Fibers and filaments.
- Films and sheets.
- Packaging materials.
- Paints and varnishes.
Starting materials are typically supplied to the fabricator in powder or pellet form.

Composite Materials

Composites are materials made of two or more distinct phases, resulting in a material with properties different from its constituent parts.
The primary phase is the bulk of material and serves as the base.
The secondary phase is often called a reinforcing agent as it strengthens the material.
Common types of composites include:
- Metal Matrix Composites (MMCs)
- Ceramic Matrix Composites (CMCs)
- Polymer Matrix Composites (PMCs)

Functions of the Matrix Material

The primary phase provides the bulk form of the composite product.
It holds the reinforcing phase in place, often concealing it.
It shares the load with the reinforcing phase, sometimes deforming to transfer stress to the reinforcement.

The Reinforcing Phase

Reinforcement phase strengthens the primary phase.
Most common shapes:
- Fibers
- Particles
- Flakes

Other Laminar Composite Structures

Automotive tires: Multi-layered rubber layers bonded with reinforcing agents.
Fiber-reinforced plastics (FRPs): Multi-layered panels for aircraft, boats, etc.
Printed circuit boards (PCBs): Layers of reinforced copper and plastic for electrical conductivity and insulation, respectively.
Snow skis: Layers of metals, particle board, and phenolic plastic.
Windshield glass: Two layers of glass sandwiching a sheet of tough plastic.

Sandwich Structure

Foam Core: Thick core of low-density foam bonded to thin sheets of a different material.
Honeycomb Core: Alternative to foam core.
Both foam and honeycomb cores achieve high strength-to-weight and stiffness-to-weight ratios.

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Description

Test your knowledge on thermosetting polymers, including their characteristics, market shares, and examples. Understand the differences between thermoplastics and thermosets, and learn about their significance in various applications.