transition in polymers

Question 1

name the natural polymers

Answer 1

collagen 
silk
natural rubber
DNA 
protein

Question 2

Synthetic polymers

Answer 2

polystyrene
polyamide
low density polyethee

Question 3

applications of polymers in dentisrty

Answer 3

prosthodontics
operative dentistry
orthodontics
endodontics
equipment

Question 4

performance criteria for dental resins

Answer 4

mechanically strong
physcially stable
easily manipulated
good aesthetic qualities
chemically stable
biocompatible
reaosnable cost

Question 5

dental resins use

Answer 5

bone cements
screw fixation in bone
filler for bone cavities

Question 6

properties of dental resins

Answer 6

acceptable cost for properties
good mechanical properties
biocompatible
suitable for manipulation
aesthetics

Question 7

problems with dental resins

Answer 7

colour stability
shrinking problems
adhesion probelsm

Question 8

how can shrinking of polymer resin be reduece

Answer 8

by adding MMA

Question 9

polymer defifniton

Answer 9

large chain like molecule made up of monomers which are small molecules joined by covalent bonds

Question 10

main polymer materials

Answer 10

metals
ceramics
polymers
composites

Question 11

structures of polymers

Answer 11

linear
cyclic
branched
cross linked

Question 12

molecular forces in polymers

Answer 12

thermoplastic
thermosetting
elastomers

Question 13

What do the physical properties of polymers depend on

Answer 13

how their molecules are arranged (polymer structure)

the strength of the forces between the molecules

Question 14

covalent bonds

Answer 14

strong

join atoms to each other in individual polymer molecules

Question 15

intermolecular forces

Answer 15

weak

attract polymer molecules towards each other

Question 16

Strength and flexibility of the polymer depends on

Answer 16

chain length
side groups
branching
cross linking

Question 17

chain length effect

Answer 17

longer the chain stronger the polyner

Question 18

side groups effect

Answer 18

intramolecular forces give stronger attraction between polymer chains making the polymer stronger

Question 19

branching effects

Answer 19

straight unbranched chains can pack together more closely than highly branched chains
higher density = more crystalline =stronger

Question 20

crystallinity

Answer 20

degree of structure order

Question 21

types of polymers in terms of crystallinity

Answer 21

amorphous

crystalline

Question 22

amorphous polymer

Answer 22

chains of polymers in random structure

Question 23

crystalline polymer

Answer 23

crystal like order

Question 24

what does crystallinity affect

Answer 24

optical 
mechanical
thermal
chemical 
properties

Question 25

thermoplastic polymers (structure, under heat, properties)

Answer 25

linear/branched structure
flow when heated and can be reshaped upon heating
easily moulded and extruded into films?

Question 26

Thermosetting polymers(structure, under heat, properties)

Answer 26

cross linked structures
cannot be reshaped upon heating
hard and durable

Question 27

elastomers(structure, under heat, properties)

Answer 27

rubbery polymers
can be stretched easily
return to original form when stress is released

Question 28

glass transition temperature

Answer 28

temperature at which the polymer chains begin to flow past each other

Question 29

Tg (transition temp) is always lower than..

Answer 29

the melting temperature

Question 30

the weaker the secondary bonds the ..

Answer 30

lower the TG

Question 31

below the Tg

Answer 31

the polymer is solid

Question 32

above the Tg

Answer 32

the polymer can flow

Question 33

polymerisation mechanisms

Answer 33

chemical reaction in which monomers of a low molecualar weight are converted into chains of polymers with a high molecular weigh

Question 34

types of polymerisation

Answer 34

addition

condensation

Question 35

addition polymerisation

Answer 35

reaction between 2 molecules producing a large molecule without elimination of a smaller molecules

Question 36

steps of addition polymerisation

Answer 36

activation
initiation
propagation
termination

Question 37

activators in addition pm

Answer 37

heat
chemical compounds (tertiary amines)
loght

Question 38

what is a radical

Answer 38

has one free e-

Question 39

where does a radical go to

Answer 39

a double bond (High density of e-)

Question 40

acrylate groups

Answer 40

look on Internet or word document for it

Question 41

condensation polymerisation

Answer 41

when a reaction between two molecules produces a larger molecule with elimination of a smaller molecules

Question 42

what is a blend used for

Answer 42

mixing polymer prior to moulding

moderate changed to mechanical properties

Question 43

copolymer

Answer 43

two different types of monomers are joined in the same polymer chain
more noticeable changes in the mechanical properties

Question 44

plasticizer

Answer 44

small molecules added to the polymer
reduced attraction forces between polymerchains
big effect in mechanical properites

Question 45

effect of a plasticiser on polymer

Answer 45

lowers Tg and elastic modulus(e.g. therefore good for brittle polymers)

Question 46

composite

Answer 46

combination of material with different mechanical properties in which the combination material offers superior properties comparing them to the individual components

Question 47

resin based composites

Answer 47

highly cross linked resin reinforced by a dispersion of amorphous silica or organic resin filler particles and or fibres bonded to the polymer matrix by a coupling agent