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Flashcards in midterm Deck (195)
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1

what are the 3 main classes of materials

metals
ceramics
polymers

2

mechanical properties of metals

Hard

Ductile – able to be deformed without losing toughness

Strong

3

bonding properties of metals

Metallic elements have 1-3 electrons in their outer shell which are loosely bound to the nucleus and interact with other electrons from various metals in the alloy to get them together

4

Almost exclusively crystalline in structure – forms grains

microstructure of metals

5

In __, no phase ever represents a pure metallic element

metal alloys

6

Mixture of two or more metallic elements

May be a homogenous mixture or exist in more than one phase

alloy

7

thermal properties of metals

high processing temperatures
thermal conductors

8

what happens when you heat up metals

it will start to look like like polymer, stretch out

9

in metals, Electrons have free mobility so they are ___ and
___ conductive.

thermally and electrically conductive

10

bend without breaking

Ductility

11

mechanical properties of ceramic

hard
brittle(shatters)
strong

12

bonding of ceramic

ionic and covalent bonds

semicrystalline or polycrystalline

13

thermal properties of ceramic

melt at high temp

14

mixture of metallic and nonmetallic elements

ceramics

15

most common ceramics

SiO2 – silicon dioxide
Al2O3 – aluminum oxide
K2O – potassium oxide

16

mechanical properties of polymer

soft
ductile (tough - bends)
weak

17

bonding of polymers

covalent bonds
high MW

18

long polymer chains (nonmetallic) - drive strength and properties from entanglement

polymers

19

use free radical concept to make __

polymers

20

polymers use free radical concept, what does that consist of
*polymerization

activation
initiation
propagation
termination

21

what factors contribute to metal mechanical properties

high processing temps
indirect placement (exception is amalgam)

22

what factors contribute to ceramic mechanical properties

high processing temps

indirect placement (exception is cements)

23

what factors contribute to polymers mechanical properties

lower processing temps
direct placement (exceptions are indirect composites)
impressions, temporary crowns, restorations

24

polymerization can be initiated by (3 things)

light
heat
chemical mixing

25

explain the 1st step in polymerization process

activation - an initiator molecule is activated by either light, heat, or chemical mixing to form free radicals

26

explain 2nd step in polymerization process

initiation- free radicals combine with monomer units present in the polymer mixture - attachment of the free radicals opens up the double bond present on the monomer, creating a new free radical

27

explain the 3rd step in polymerization process

propagation - the constantly forming monomer free radicals continue to bind with other monomers, which become free radicals and bond to other nearby monomers, thus growing the polymer chain

28

as the polymer chain grows in in the propagation phase of polymerization what happens to the volume of the polymer mix

the volume of the polymer mix decreases and begins to shrink (molecules are bound instead of floating free)

29

last and 4th step in polymerization process

termination - a floating free radical bonds to the free radical end of the polymer chain, creating a double bond and capping off the chain

30

what is the difference between a linear polymer and crosslinked polymer?

linear polymer - no long chain branches so can not become tangled

crosslinked polymer - have long chain branches, become tangled and are therefore mechanicall stronger