CAM 120 Chapter 7 and 8

Define glass.

An inorganic, nonmetallic compound or mixtures of compounds that cools to a ridged condition without crystallization. (ceramic that is in the glassy state as a solid material.)

Does any polymer ever become 100% crystalline?

No, it can not

Under which type of stress are ceramic materials stronger, compressive stresses or tensile stresses?

The compressive test.

Diamond is a special form of what element?

"Carbon," which possess a cubic crystalline structure with covalent bonding between atoms

What is a polymer?

A compound consisting of long chain-molecules, each molecule made up of repeating units connected together. There can be thousands even millions of units in a single polymer molecule

What is a ceramic?

An inorganic compound consisting of a metal or semimetal and one or more nonmetals

What is the chemical formula of ethylene, the monomer for polyethylene?

C2, H4

What is a plasticizer?

Chemicals added to a polymer to make it softer and more flexible, and to improve its flow characteristics during forming

What type of atomic bonding characterizes the ceramics?

Covalent and ionic bonding are bonds that are stronger than metallic bonding in metals which accounts for high hardness, stiffness but low ductility

What is cross-linking in a polymer?

Crosslinking is the formation of connections between the long-chain molecules ina polymer. It causes the polymer structure to be permanently altered.

Which type of reinforcing filler provides the greatest strengthening effect, powders, or fibers?

Fibers provide the greatest strengthening effect.

What is the feature that distinguishes glass from the traditional and new ceramics?

Glasses are brittle and possess no virtually ductility which is the opposite in ceramics with high hardness, electrical and thermal insulating characteristics.

What is graphite?

Graphite is a versatile material as a powder, lubricant, traditional solid form, and when formed into fibers it is a high strength structural material

What is the name of the curing process used to effect cross-linking in natural rubber?

It is called Vulcanization.

What are the general physical properties of ceramic materials?

Most ceramic materials are lighter than metals and also possess low electrical and thermal conductivities.

What are the four most common elements in the earth's crust?

Oxygen, silicon, aluminum, and iron.

What is the difference between a partially degradable plastic and a completely degradable plastic?

Partially degradable consist of polymer and natural filler, the polymer matrix is petroleum-based which is nonbiodegradable. Completely biodegradable consist of polymer and filler that are both derived from natural and renewable sources " starch, cornstarch, and sugarcane

In addition to fillers and plasticizers, what are some other additives used with polymers?

Pigments, dyes, and, lubricants are also added.

What is glazing, as applied to ceramics?

Putting an application of oxides like silica and alumina on its surface to make the product less previous to moisture and attractive to the eye.

What are the general mechanical properties of ceramic materials?

Ridged and brittle exhibiting a stress-strain behavior "perfect elastic behavior."

1What is the primary ingredient in virtually all glasses?

Silica is the primarily used ingredient

How do thermoplastic elastomers differ from conventional rubbers?

TPEs are different in two basic ways: (1) they exhibit thermoplastic propertiesand (2) their extensibility derives from physical connections between different phases inthe polymer rather than cross-linking.

1What does the term refractory mean?

That refractory materials are used in high heat temperatures and used for thermal insulation which are crucial use in industries that use furnaces to heat or melt materials

What does the term degree of polymerization mean for a polymer?

The mean value of n is the degree of polymerization (DP) affects the properties of the polymer, higher DP increases mechanical strength but also increases viscosity in the fluid state, which makes the processing more difficult

What does the term molecular weight mean for a polymer?

The molecular structure of a polymer is the sum of the molecular weights of the mer in the molecule it is n times the MW of each repeating unit.

Why is the recycling of plastics more difficult than recycling of metals and glasses?

There are several reasons. Metals are more favorable for recycling materials. plastics contain fillers, dyes, and other additives that cannot readily separated from the polymer itself. A common problem in recycling is the fluctuation in the prices of recycled materials.

What are the three basic categories of polymers?

Thermoplastic polymers, thermosetting polymers, and elastomers

Of the three basic categories of polymers, which is produced in the largest tonnage?

Thermoplastics consisting of 70% of tonnage

Why are fillers added to a polymer?

To alter its mechanical properties or to simply reduce material costs

How does step polymerization work?

Two reacting monomers are brought together to form a new molecule of the desired compound and can continue growing. Water is not always the byproduct of the reaction

16.

What is ebonite? A hard rubber

Elastomers and thermosetting polymers are both cross-linked.

Why are their properties so different? To allow elastomers and thermosetting to cross-link

How do the properties of thermosetting polymers differ from those of thermoplastics?

properties of thermosetting plastics are different from those of thermoplastics in general. Thermosets are more ridged, brittle, less soluble in common solvents, capable of higher service temperatures, and not capable of being remelted

Which of the three elements boron, carbon, and silicon, is an important semiconductor?

silicon