Exam Review Questions

network modifiers

______ are the oxides that break up the glass network and improve glass processability by decreasing viscosity

2

the functionality of the following monomer is H H I I C = C I I H H a. 1 b. 2 c. 3 d.4

alternating

ABABABAB is an example of ___ copolymer

high will be stronger bc the chains can pack very efficiently; this creates more intermolecular attraction between the chains making it more difficult to break

Explain why low density polyethylene is weaker than high density polyethylene?

ionic solid

Graphite CANNOt be classified as: a. conducting solid b. network solid c. covalent solid d. ionic solid

b. crystallizes

High Density polyethylene cooled slowly from 160 to room temperature. a. is still amorphous b. crystallizes c. is a mixture where some regions are rubbery and some regions are glassy.

low hardness (high temp stability and high mechanical strength are thermosetting properties) (high elongation is a property of elastomers)

One of characteristic property of thermoplastic polymeric materials: a. high temp stability b. high mechanical strength c. high elongation d. low hardness

True

T or F. The glass transition temp of polymer can be changed using a plasticizer.

False; plastic fiber increase strength of a polymer

T or F. addition of a plastic fiber will decrease the strength of a polymer

False-thermosetting has no melting point; just decomposition point

T or F. melting point of polyester (thermosetting) is 200C.

the smaller particles of the organic raw materials combine together by solid state diffusion to convert larger grains

What is the sintering process? what occurs to the ceramic particles during sintering?

once the water molecules are removed the wood will shrink more in the transfers direction than in the longitudinal direct because the water molecules are located between the cellulose fibers in the lumen which are parallel horizontal fibers' when the water is removed the parallel horizontal cellulose fibers become closer making the internal attraction stronger

Why does wood shrink much more in the transverse direction than in the longitudinal direction?

polyethalene polypropelene; eggs(:

___ and ___ would be two examples of polymers

MC= weight wet- weight dry/ weight dry 210-125/125 x 100 =Mc

a piece of wood contains 210 g moisture, after oven drying to a constant weight, it weighs 125 g. What % is moisture content?

monomers

a simple molecular compound that can be covalently bonded to form long molecular chains is known as _____

c. is a glassy material

atactic polystyrene (Tg=100C) quenches (cooled very quickly) from 120 to room temp a. is a rubbery material b. crystallizes c. is a glassy material

number of anions surrounding central cation in an ionic solid

define coordination number in ionic solids

Partly crystalline: as T decreases there is a sudden decrease in specific volume, drop occurs at Tm (melting temp). Non crystalline(amorphous): there is a gradual decrease in specific volume as temp decreases, has a Tg(glass transition temp) not a Tm

during solidification of thermoplastics, how does the specific volume vs. temperature plots differ for noncrystalline and partly crystalline thermoplastics?

c. straightening of molecular chains

elastic deformation in polymers is due to a. slight adjust of molecular chains b. slippage of molecular chains c. straightening of molecular chains d. severe deformation of covalent bonds

aramid or kevlar "Hey thats what we're doing our project on"

fibers made up of aromatic polyamide are known as ____

parallel; to minimize bending/torsional movement; minimize the elasticity, elastic deformation to make stiff so the ball with travel faster

if a tennis racket is made up of wood. Would you orient the wood's fiber direction parallel or perpendicular to the axis of the shaft of the racket? explain with sketch.

b. thermoset

in general the strongest polymer group is: a. thermoplastics b. thermoset c. elastomers d. all polymers

stereoisomers

molecules that have the same chemical composition but different structural arrangement are known as ____

d. only 3. sintering is the atomic diffusion or solid state diffusion of ceramic raw material particles 1. SiO4 4- is the subunit of glass 2. the units are tetrahedrally arranged

read the following statements carefully 1. SiO2 2- is the fundamental subunit of glass 2. in glass, silicate units are octahedrally arranged 3. sintering is the atomic diffusion or solid state diffusion of ceramic raw material particles Which one of the following statements are CORRECT about ceramics? a. all of the above b. only 1 c. 1 and 3 d. only 3

tempering

strengthening of glass by sudden cooling is known as _____

DP= mol wt of polymer/ wt of monomer 100000/28 200000/28 high molecular weight, better strength

the molecular weight of two samples of polyethylene is 100000 and 200000 g/mol. calculate degree of polymerization. mass of a single unit is 28. from which one do you expect better strength. explain why?

DP=150000/28

the molecular weight or molecular mass of high density polyethylene is 150000 g/mol. Calculate the degree of polymerization. Mass of ethylene monomer is 28 g/mer(monomer).

coordination number

the number of anions surrounding the central cation in an ionic solid is known as _______

to decrease the brittle-ductile transition temp (aka glass transition temp) additional info: the glass transition temp is only about the movement of poller chains; when you add a plasticizer into the polymer chains you improve/increase the free movement of the polymer chains

the role of a plasticizer is: a. to increase the molecular weight of the polymer b. to decrease the melting point of the polymer c. to increase the glass transition temp d. to decrease the brittle-ductile transition temp

c. elastomers

these polymers, primarily consist of coil-like polymer chains a. thermoplastics b. thermoset c. elastomers d. all polymers

same chemical composition different structural arrangement; static-least crystalline which are alternating pendant group/ syndiotatic isotatic - all on the same side

what are stereoisomerism? explain syndiotaic stereoisomerism.

it is headed to its softening point and then suddenly cooled which causes the surface to cool first; it becomes compact/rigid, the interior however cools gradually, but the surface will not allow the shape to change so compressive stress is introduced on the surface and tensile stress is introduced to the center; to break the glass tensile>>>> compressive because of this overall strength is improved ex. car window shield

what is tempered glass? describe how it is produced and how it is considered stronger than annealed glass? give applications. draw schematics for full credit.

it improves strength of concrete bc of the compressive stress inside the concrete; pre-tension is simpler and more common than post-tension 1. pre-tension concrete the steel rod is placed and tensile stress is applied before concrete is poured; once concrete is set the force is removed but the steel rod that was in the tensile state wants to go back to its original state and can't bc of the set concrete 2. post-tension

what is the main advantage of pre-stressed concrete?

all of the above

which of the following factors affect the strength of a thermoplastic polymer a. molecular weight b. crystallinity c. presence of a polar atom d. all of the above