Polymers

Question 1

types of polymer

Answer 1

1. natural (proteins, DNA, polysaccharides)
2. semi synthetic
3. synthetic (plastics, rubbers)

Question 2

what is a polymer

Answer 2

long chain molecule made of monomers joined together. can be linear, branched, crosslinked, colloidal

Question 3

thermoset polymer

Answer 3

burns when heated and irreversibly hardened once shaped. inflexible, curing required (adding crosslinks)

Question 4

thermoplastic polymer

Answer 4

melts when heated and can be remelted and reshaped. flexible and no curing required

Question 5

elastomer

Answer 5

can be thermoplastic or thermoset.
viscoelastic= viscous and elastic properties when deformed

Question 6

HDPE

Answer 6

low/ no branching –> high crystalline content
less transparent, less gas permeable, stiffer

Question 7

LDPE

Answer 7

highly branched (60 branch points for every 100 C atoms)
more transparent, flexible (eg plastic bags)

Question 8

crystallinity

Answer 8

regions of atomic ordering where intra molecular folding/ stacking of adjacent chain occurs
affects resistance, thermal behaviour, stiffness
0–>1 = amorphous –> crystalline

Question 9

strain vs stress

Answer 9

strain (E) -E = l/L
stress (sigma) - sigma = F/A (cross sec. area)

Hookes law = F = -k(constant) x x(l)

Question 10

Youngs moduli

Answer 10

for a solid: stress = -E x strain