ENGR 205 Quiz 8/14/15

Calvin University ENGR 205

Molecules that have double and triple covalent bonds are called _____.

unsaturated

The bonds between molecules in hydrocarbons are _____.

hydrogen

Butane is a _____ at room temperature (20C).

gas

Polymer molecules are _____ compared to gaseous hydrocarbons such as methane.

much larger

The covalent bonds between carbon atoms in a polymer molecule are generally _____ bonds.

single

Long polymer molecules are composed of structural entities called _____.

repeat units

The monomer _____ does not contain hydrogen atoms.

tetrafluoroethylene

A chain composed of two or more different repeat units is called a _____.

copolymer

The functionality of a monomer is the number of _____ the monomer.

bonds formed by

The angle between the bonds of adjacent carbon atoms in a polymer chain is about _____.

109

A polymer chain's end-to-end distance r, is typically _____ the total chain length.

less than

A _____ does not restrict a polymer chain's rotational movement.

single bond between carbon atoms

A _____ polymer has a molecular structure of secondary chains that extend from the primary main chains.

branched

A _____ polymer is joined end to end in single chains.

linear

A polymer with a large number of covalent bonds between adjacent chains is classified as _____.

both a crosslinked polymer and a network polymer

A _____ polymer softens when heated and hardens when cooled.

thermoplastic

When heated to excessively high temperatures, a thermoplastic will experience _____ degradation.

irreversible

Thermosetting polymers are harder and stronger than thermoplastic polymers because of _____.

crosslinked bonds

Side branches of one homopolymer attach to chains of a different homopolymer to form a _____ copolymer.

graft

Styrene-butadiene rubber (SBR) is a(n) _____ copolymer used to make automobile tires.

random

The degree of polymerization of a copolymer is calculated using the _____ molecular weight.

average repeat unit

Polymers' atomic arrangements are _____ complex when compared to metals and ceramics.

more

The degree of crystallinity of a polymer is __%.

0 to 95

High crystallization is common in _____ polymers

linear

The modulus of elasticity for polymers is _____ the modulus of elasticity for metals.

lower than

Highly elastic polymers have ductility of about _____%EL.

1000

The chain axes _____ in the neck during plastic deformation of a semicrystalline polymer.

align parallel to the elongation direction

Right after necking begins in a semicrystalline polymer, subsequent deformation _____ the neck region.

proceeds by propagation of

For _____ behavior, deformation is dependent on time and is not reversible.

viscous

In the definition of the relaxation modulus Er(t), the _____ changes with time.

stress

In the definition of the creep modulus Er(t), the _____ changes with time.

strain

A polymer's susceptibility to viscoelastic creep _____ with increasing degree of crystallinity.

decreases

For most applications of polymers, a ductile-to-brittle transition temperature _____ room temperature is desired.

below

High frequency cycles in fatigue testing of polymers can cause failure due to _____ instead of typical fatigue processes.

softening

The _____ strength of a polymer is of particular importance for thin films in packaging.

tear

Elastic deformation of a semicrystalline polymer begins with the elongation of chain molecules in _____ region(s).

the amorphous

Displacement of molecular chains is resisted by _____ bonds in semicrystalline polymers.

van der Waals

Plastic deformation in semicrystalline polymers is _____.

reversible with proper annealing

The tensile modulus of a semicrystalline polymer _____ with increasing molecular weight.

remain unchanged

Increasing the crystallinity of a semicrystalline polymer will _____ the tensile modulus and _____ the tensile strength.

increase, increase

Predeformation of semicrystalline polymers is similar to _____ of metals.

strain hardening

Increasing the annealing temperature of an undrawn polymer will _____ the strength and _____ the ductility.

increase, decrease

The modulus of elasticity of elastomers is _____.

strain dependent

Elastomers have a(n) _____ structure.

amorphous

To be useful, vulcanized rubber should have a sulfur crosslink every _____ repeat units.

10 to 20

For application where transparency is critical, such as lenses, _____ are ideal.

acrylics

Nonstick coatings on cookware are generally made from _____.

fluorocarbons

_____ is the most frequent substitute for natural rubber.

Styrene-butadiene

_____ should be used for outdoor applications that will expose the material to weather.

chloroprene

_____ is often used to make cooking utensils and medical tubing.

polysiloxane

Fiber polymers are capable of being drawn to at least a _____ length-to-diameter ratio.

100 to 1

Fiber polymers used in clothing must have _____ tensile strength and _____ modulus of elasticity.

high, high

Fiber polymers used in clothing must have _____ melting temperatures and _____ glass transition temperatures.

high, low

An inert foreign substance added to modify material properties

filler

A low-molecular-weight polymer added to enhance flexibility and reduce stiffness

plasticizer

A substance added to prevent rapid deterioration

stabilizer

_____ molding is the most widely used technique for fabricating thermoplastic materials

injection

Preheating of a preform is used to decrease molding time and pressure in _____.

compression molding

The _____ technique is used to produce continuous lengths having a constant cross-section

extrusion

In _____ spinning, fibers are formed by passing a polymer-solvent through a spinneret into a second solvent.

wet

Both fibers and films can be drawn after initial forming to _____ thickness and _____ strength.

decrease, increase

3D printing using _____ does not require a support structure to prevent warping or collapsing.

stereolithography

In the _____ technique of 3D printing, a build platform is raised out of a liquid resin bath.

CLIP

Using _____ allows for printing multicolored objects or objects with different properties at different locations.

polyjet printing

Ductile metals exhibit _____ plastic deformation with _____ energy absorption before fracture.

substantial, high

A stable crack will extend with _____ in the applied stress.

an increase

Ductile fracture requires _____ strain energy compared to brittle fracture.

higher

_____ materials show virtually 100% reduction in area at fracture.

highly ductile

Most ductile materials experience a _____ amount of necking before fracture.

moderate

The long axis of an elliptical crack during the process of ductile fracture is _____ to the direction of the applied stress.

perpendicular

Fractographic studies are performed using a(n) _____ microscope.

scanning electron

Impact testing is used to determine fracture characteristics at _____ temperature and _____ loading rates.

low, high

In the _____ impact test, the specimen is supported on both sides with impact on the side opposite the v-notch.

Charpy

The ductile-to-brittle transition is related to the _____ dependence of the measured impact energy absorption.

temperature

Increasing the carbon content of a steel alloy will _____ the ductile-to-brittle transition temperature.

increase

ductile-to-brittle transition

The transition from ductile to brittle behavior with a decrease in temperature exhibited by some low-strength steel (BCC) alloys; the temperature range over which the transition occurs is determined by Charpy and Izod impact tests.