Biochem Simplified Flashcards
2 reasons we measure mechanical properties
to obtain fundamental properties and to see what properties will affect the material in its final conditions
fundamental properties
strength
elasticity
applied properties
impact
fatigue
abrasion
1st classification of mechanical properties
bulk: whole mass - strength, elasticity
surface: first few layers of atoms - hardness, wear
resistance to indent
hardness
resistance to abrasion
wear
Fundamental - steadily increase load (stress-strain)
Applied - single sudden force (impact), repeated low load (fatigue), time dependent (viscoelastic - plastic bag example)
2nd classification of mechanical properties - Bulk subclassifications (fundamental and applied)
force per unit area, arises from externally applied forces
stress
stress units
Pa, MPa
force/area= stress
calculation
arrows away
tension
arrows towards
compression
bar parallel to the ground, one arrow on top one on bottom
sheer
compression, tension and sheer
torsion
compression and tension
flexure/binding
tensions makes things ___ compared to compression
weak, crack
strain is to ____ as stress is to ____
strain is to deformation as stress is to load
strain calculation
change in L / L(i). or L(f)-L(i)/L(i)
elastic strain is
recoverable
plastic strain is
permanent
phases of plastic and elastic while recording an impression
plastic on insertion(perm) and elastic on displacement from tissue (recoverable)
O –> A on the stress/strain graph is linear and elastic because it hasn’t reached the breaking point so it is _______
recoverable
Law that states that up until A on the stress/strain graph, stress and strain are proportional to each other
Hookes Law
What is that linear portion of the stress/strain graph called and what region does it represent (up until A)
Called the Modulus of Elasticity and is defined as the elastic region of the material
Modulus of elasticity is a measure of ______ / _____-
rigidity/stiffness
High modulus: ____ rigid
more
Low modulus: ____ rigid
less
A,B,C on stress/strain graph
A: proportional limit
B: elastic limit
C: yield point
(PEY for your ABC’s lol)
Stresses below B on the stress/strain graph
elastic
Stresses above B on the stress/strain graph
plastic
Stress at B called
Elastic Limit
Yield point is the point where _____ strain becomes very pronounced
plastic
Reminder - all values of stress on the _ axis
Y
Ductility and Malleability are measures of ___ of ____
% of elongation
High % of elongation: ____ material
ductile
Low % of elongation: ____ material
brittle
relating to TENSION: ductility is the measure of something’s ability to form a ____ shape
wire
relating to COMPRESSION: malleability is the measure of the ability to be _____ into a ____
hammered into a sheet
Elongation is a value of ____
strain (X axis)
OBD triangle on stress/strain graph
Mod. of resilience
Total area under stress/strain graph
Toughness - area units J/m3
Total energy a material can absorb until fracture
toughness
amount of energy a material can absorb without permanently deforming
resilience
hardness indenter circle shape
brinell
hardness indenter small diamond
vickers
hardness indenter long diamond
knoop
what is time dependent (plastic bag stress over time)
viscoelasticity
deform under constant pressure/stress over time
creep
monomers + monomers
polymeric molecules
polymeric molecules + polymeric molecules
polymeric material
ID condensation reactions: Si and O, NO C, eliminating H2O
Silicones
ID condensation reactions: eliminate NaCl
Polysulfides
ID condensation reactions: Chain of C, eliminate H2O
Nylon
Addition / vinyl compound’s two shining stars of the show
Acrylics - resin and acid
hard rigid glass polymer, liquid and then at dentists final polymer is synthesized
Acrylic resin
adhesive water soluble polymer, liquid and ready to be used
Acrylic acid
Common example of vinyl compound / acrylic resin in dentistry
Methacrylate –> PMMA (dentures/dental cements)
G(2)PT - 4 stages of polymerization
Generation of free radicals - activation (heat/light) - initiation (at molecular level) Propagation of rxn Termination of rxn
SAP that alter one another
structure, properties, application
spaghetti example is referring to polymeric materials
length, temp, alignment, disentanglement, sauce
DoP
of repeat units/monomers
MW
DoP x MW of repeating units (in g/mol usually)
Higher the MW, higher the ____/____
strength/rigidity
Higher the DoP, Higher the strength because
more bonds to break
3 physical states of polymers (EAS)
Elastomers Hard amorphous (transparent) Hard semicrystalline (translucent)
why are polymers more flexible at higher temp
easier disentanglement
High Tg leads to
rigid at room temp
Low Tg leads to
flexible at room temp
High Tg - RIGID (hard polymers)
Low Tg - FLEXIBLE (elastomers)
elastics is to ___ and viscous is to break intermolecular bonds and ____
stretch, disentanglement
plasticizers liquids that reduce friction between molecules and ____ and lower Tg
Soften, lower Tg
Cross linking leads to more bonds and results in (3 things)
stronger, more rigid, higher Tg
lead to different arrangements at molecular level (SAME COMPOSITION THO) and results in different properties
co polymers
impressions, rubber for root canal, resin composites are all examples of
polymer application in dentistry
mixture of metals
alloy
metals are polycrystalline which means long, regular arrangement of atoms. in contrast, _____ has no such regularity
amorphous
point imperfections (3)
substitutional, interstitial, vacancies
line imperfection results in ____ in a crystal
dislocation
metal with smaller grains results in a ____, tough and dense but more corrosive metal
strong
plastic deformations in metals results in slip of layers of atoms over each other and is __
permanent
soft metal is one where ___ can be easily moved through crystal structure
easily
makes more dislocations, more interactions between dislocations which makes stronger
cold working
grain growth - from heating, larger grains form, less impediment for dislocation
softer material
to have a solid substitutional you need the same lattice structure and similar ___ size
atomic (au, Cu, Ag, Pt, Pd – FCC)
Steel C atoms in Fe - since carbon is so small compared to Fe results in
Solid interstitial. results in stainless steel and makes dislocation harder
You have metal A and metal B. have a combo of both then that is a variable combo
partial solid insolubility.
metals make compounds but they are very specific and defined composition ex: Ag3Sn - amalgam
Intermetallic compounds
strong, stiff, brittle, but chemically stable and noncorrosive
ceramics
