Flashcards in Exam 1 Deck (53):
Mn, Mw, and PDI, what is PDI=1 mean
Mw = Weight Average molecular weight
Mn = Number average molecular weight
PDI = Mw/Mn
If PDI = 1 --> Similar length chains
Atactic vs. Isotactic vs. Syndiotactic
Atactic = no order = Amorphous
Isotactic = one side = partial crystalline
Syndiotactic = alternating = partial crystalline
Addition of mer (repeated units)
Initiation with radical species, elongation/propagation, and termination
Condensation polymerization involves:
Elimination of certain byproducts (usually water) as a part of the synthesis reaction
Yield Stress vs. Fracture Stress vs. Ultimate Stress
Yield stress = max stress in the ELASTIC region
Fracture stress = Max load at failure
Ultimate stress = max load before necking occurs (absolute max)
PXRD peak sizes narrow vs wide
Amorphous = Wide smooth peaks, smaller crystal size, more noise
Crystalline = narrow peaks, larger crystal size, less noise
Ceramics have what qualities
High compression modulus, low ductility
Calcium Phosphate and HA make up _____ in body
Inorganic bone -- (not ligaments)
HA in human body is (high/low) crystallinity
(high/low) crystallinity is more easily absorbed
Low Crystallinity HA is more easily absorbed
Galvanic Corrosion can occur (not exclusively) when:
Two different metals of DIFFERING potential are placed near each other
Passivation layer is removed, leads to ion loss at the site of pitting
Occurs in metallic devices due to CYCLIC LOADING over time
Passivation on metallic surface (increases/reduces) rate of corrosion
Reduces rate of corrosion
PLGA degrades to:
Acidic degradation products
PLGA/PPHOS composite degrades to:
Neutral byproduct, since PPHOS neutralizes the acidic byproduct of PLGA
Calcium Sulfate used for:
Non-load-bearing injectable bone void filler
Molybdenum added to stainless steel to:
Increase corrosion resistance AND Hardness
Contact angle goniometry measures:
Strength of adhesion and hydrophilicity
Low contact angle = higher adhesiveness
Is Scanning Electron Microscopy suitable for live cell analysis?
No, it kills cells -- Specimen must be conductive and in a vacuum
Secondary Ion Mass Spectroscopy:
Analysis of surface based on MASS AND FORCE
Absorbance/transmittance of IR light energy reflected back from a material's surface
Tg associated with: ____
Tm associated with: ____
Amorphous polymers = Tg
Crystalline polymers = Tm
Sterilization of UHMWPE in ABSENCE of O2 does what?
Increases resistance to wear
Change in pH and/or Temp are both methods for:
Desorbing proteins from a surface
Bulk degrading polymers, what happens:
Molecular weight is reduced, rate of water penetration exceeds rate of material breakdown - hydrophilic
Surface eroding polymers, what happens?
Outside of material peels away like an onion, steady degradation - hydrophobic process
Degradation of Poly(lactide-co-glycolide) :
Affects surrounding environment
Undergoes BULK DEGRADATION
Hydrolysis, turns to Lactic acid + Glycolic acid
Degrades a different rates depending on Polylactide:polyglycolide ratio
Tissue sterilization of bone allografts (Increases/reduces/eliminates) risk of disease transmission between donor and recipient:
Reduces risk, not eliminate
Thermoplasts vs. Elastomers vs. Thermosets, which can be recycled:
Thermoplasts and Elastomers can be recycled
ThermoSET state is SET so they can't be recycled
Process of killing organisms causing infection known as:
EPOCH hip components
75% less stiff than similar Co-Cr implant (less stress shielding)
Exterior is composed of Titanium Fiber mesh
Core composed of metal - surrounding polymer
Composed of: PAEK, Ti, Co-Cr
The nickel-titanium material which goes back to its shape when placed in water
Which surface characterization method involves the creation of secondary electrons as part of analysis:
SEM - Scanning electron microscopy
NOT FTIR or Energy dispersive spectroscopy
Which methods of analysis provide a "fingerprint"
X-Ray diffraction (bulk analysis)
FTIR (surface analysis)
Most common mechanism for degradation in biomedical polymers?
Advantages of bone autografts:
No recipient immune response
Graft is osteoinductive - with all the growth factors
No disease transfer
Osteoinductive vs. Osteoconductive
Osteoinductive = growth factors, osteoblasts stimulated
Osteoconductive = will bone grow on the surface
What influences Ca3(PO4)2 deposition
LOW crystallinity HA easily resorbed - more deposition
NaOH and HA can increase deposition
High crystallinity HA is NOT easily resorbed by the body
BAK/C implants made from
BAK/C implants are for intervertebral discs
Particulate debris from metallic implants results from:
Wear, Fretting, Fragmentation
Which metals suitable for hip replacement?
NOT Stainless Steel
Hydrogels have what properties
Good stability, refractive index, high oxygen permeability
Degree of cross-linking influences: Degradation, diffusion, mesh size, mech. properties
Hydrogels have what functions?
Prevent fluid loss, microorganism entry
Injectable for filling in complex shapes
Bulk degradation vs. Surface erosion - which for drug delivery
Surface erosion for drug delivery -- Degrades over time = controlled release
Bulk degradation - Mw decreased until material experiences catastrophic failure
Benefits of forming polymer/ceramic composite scaffold for bone tissue vs. polymer/ceramics alone
Offset drawbacks of each when used together vs. alone
Polymer offers greater biocompatibility, degradability, and TENSILE strength, and has Greater WORKABILITY.
Ceramic offers greater biocompatibility from ion exchange interactions with bone. It also offers greater COMPRESSIVE strength, but has low ductility. When making degradable materials, a composite can be controlled better than a pure substance.
Describe corrosion and passivation -- How does corrosion occur? What is the effect of passivation and how does it perform this effect?
Corrosion = loss of ions = loss of mass over time
2 different metals placed in an environment with conditions that allow for ion exchange
--> Formation of anode/cathode.
The reduction potential difference determines rate of corrosion.
Passivation - formation of thin protective layer on the surface of the metal that protects substance from corrosion by shielding the material from changes in electrical potential
Advantage of low crystalline HA over highly crystalline HA:
Natural bone in body is made of low crystallinity HA, which is more easily resorbed by osteoclasts and osteoinductive.
High Crystal HA not as osteoinductive - not easily resorbed.
Trabecular metal tech - unique features
Made of tantalum metal - mimics trabecular structure of bone - consists of porous, honeycomb-like structures
Tantalum's porosity allows for much greater biocompatibility with trabecular bone - organic bone can grow on and inside implant, VASCULARIZATION can occur.
Design question: New Hip - What materials?
Use Co-Cr alloy, Titanium, PEEK polymer, and Low Crystallinity HA
Design new hip - WHY materials
Co-Cr for core - high ultimate stress and fracture stress
PEEK for surrounding the core - for elastic modulus similar to bone - LESS STRESS SHIELDING
Ti alloy mesh for a HA framework on surface - low crystal = more mineral deposition on implant = more osteoinductivity = more biocompatible
Design new hip - how to sterilize and why?
Gamma ray radiation, since it penetrates the entire implant and leaves no leftover debris or residue
Design new hip - 3 methods of characterization and why
Contact angle goniometer - determine hydrophilicity - know if material will swell in aq. environment
ESCA (Electron spectroscopy for chem. analysis) - determination of groups present on surface - compare to groups present on desired materials (Low Crys. HA and Ti alloy)
FTIR to make unique fingerprint of surface material - in conjunction with ESCA can determine surface materials.
Any impurities can be detected and fixed before further development to mitigate risks of inflammation or recipient rejection of implant.