BioMaterials Exam 1

Question 1

2. A DSC thermogram of an unknown polymer sample yields two low temperatures transitions and one large temperature transition just before it degrades. Which statement is most accurate?

Answer 1

The sample it’s a polymer blend

Question 2

3. The glass transition temperature Tg of polymers is generally lower than that of metals.

Answer 2

False

Question 3

4. Which statement is least accurate regarding bonding in polymers?

Answer 3

Ionic bonds are prevalent in thermosets.

Question 4

5. The crystalline phase of thermoplastic polymers assumes the random configuration

Answer 4

False

Question 5

6. Which statement is most accurate regarding polymers?
   a. All polymers melt at sufficiently high temp
   b. The Free Volume theory is integral in explaining their Tm.
   c. Only some of the bonding in polymers are directional.
   d. All polymers crystallize via chain folding.
   e. None of the choices are correct

Answer 5

None

Question 6

7. An atactic polymer will have a lower elastic modulus that its isotactic counterpart.

Answer 6

True

Question 7

8. For a given semicrystalline polymer, as molecular weight increases:

Answer 7

The Tg increases.

Question 8

9. An example of a thermoset is

Answer 8

Bakelite (phenol-formaldehyde)

Question 9

10. The equilibrium distance between atoms in a metal also known as the d-spacing can be determined using:

Answer 9

Bragg’s Law

Question 10

16. Which statement is most accurate regarding metals.
    a. The Van Der Waals bonds are broken at high temp
    b. Dipoles in the metal become critical at low temp
    c. All metals are solid at room temp
    d. None
    e. In zero gravity, they behave more like polymers
    f. The molecules are more closely packed than ceramics

Answer 10

None

Question 11

20. From a biocompatibility standpoint, glass is classified as a?

Answer 11

Bioinert

Question 12

21. One can increase the creep resistance of stainless steel by annealing.

Answer 12

False

Question 13

22. Glass, which contain additives, for example Borates, have a lower melt temperature, Tm, than those comprised of silica only.

Answer 13

False

Question 14

23. A quenched sample of polyethylene tends to be clear, while an annealed ample of polystyrene tends to be opaque?

Answer 14

False

Question 15

24. Polymers in solution assume the _________ conformation.

Answer 15

amorphous

Question 16

25. Plasticizers when added to polymers result in a crease in the Tm?

Answer 16

False

Question 17

30. How many atoms compromises the HCP unit cell?

Answer 17

6

Question 18

33. Poly Acrylamide is a hydrogel that is used in contact lens applications. Which statement is most accurate about gels?

Answer 18

The O2 diffusivity increases with water content

Question 19

35. A DSC thermogram of an unknown sample yields a gentle increase in slope as temperature increases as shown below. Which stamen is most accurate?

Answer 19

The sample is a thermoset

Question 20

36. The percent crystallinity may be determined by Dynamic Light Scattering.

Answer 20

False

Question 21

37. Two specimens of stainless steel are being evaluated for possible use in cardiovascular stent application. Specimen A is quenched, while specimen B is slow cooled. Which of the two specimens will exhibit a higher Tg.
    a. Sample A
    b. Sample B
    c. Tg will be the same
    d. None

Answer 21

None

Question 22

38. The molecular weight of a polymer can be determined by Gel Permeation Chromatography?

Answer 22

True

Question 23

39. One can increase the creep resistance of Aluminum by slow cooling.

Answer 23

False

Question 24

40. Describe how you would determine the yield point of a specimen whose stress-strain curve does not exhibit a classic yield point?

Answer 24

take the 0.2% of the strain curve, draw a parallel line of the take-off angle, and where this line intersect the curve, thats the yield point.

Question 25

43. The Tg that is often observed in polymers may be phenomenologically explained by which of the following theories?

Answer 25

Free Volume Theory

Question 26

44. When manufacturing metallic orthopedic implants, strengthening techniques include all, except?

Answer 26

Welding

Question 27

45. When comparing two polymeric specimens, the branched sample will have a higher Tm than it’s unbranched counterpart.

Answer 27

False

Question 28

47. In addition of being used as contact lens material, polymer gels are also used in maxillofacial repair. Which stamen is least accurate about gels?
    a. They are formed from monmers with functionality >2
    b. Explained by Carothers’s theory
    c. At the gel point the viscosity is finite
    d. Early stage of gelation yields small crystals
    e. All choices are correct

Answer 28

d. Early stage of gelation yields small crystals

Question 29

49. Which statement is least accurate regarding bonding in polymers?
    a. Diamond has the same type of primary bonds as polymers
    b. All the bonds in polymers directional
    c. Bonds are not governed by the Free Electron Theory
    d. All choices are correct
    e. They are compromised solely of primary bonds

Answer 29

They are compromised solely of primary bonds