4- General Intro to Polymers Flashcards
what is polymer (break down of word)
many repeat unit
saturated hydrocarbons
each carbon is fufilled with as many hydrogens
double bond
ethylene or ethane
tripe bond
acetylene or ethyne
most polymers are defined by
chemical composition
molecular wieght
molecular structure
degree of polymerization (DP)
how many monomers are in a chain
chain length (l)
end to end distance of a stretched out molecule
molecular weight (mw)
weight of chain
end-to-end distance (r)
distance between ends of randomly coiled chain
what are methods of molecular weight determination?
number average molecular weight
weight average molecular weight
viscosity average molecular weight
molecular weight distribution
molecular weight
mass of a mole of chains
define polydisperisty index (PDI)
Ratio of Mw to Mn
degree of polymerization
n= number of repeat units per chain
define conformation
molecular orientation that can be changed by rotation around bonds
define tacticity
stereoregularity of chain
isotactic
syndiotactic
atactic
define isotactic
all R groups on same side of chain
syndiotactic
R groups alternate sides
atactic
R groups random
Cis/trans isomerism
cis- bulky groups on same side of chain
trans- bulky groups on opposite sides of chain
copolymers
two or more monomers polymerized togeher
random
alernating
block
graft
random (copolymer)
A and B randomly vary in chain
alternating (copolymers)
A and B alternate in polymer chain
block (copolymers)
large blocks of A alternate with large blocks of B
graft (copolymers)
chains of B grafted on to A backbone
spherulites
fast growth-forms lamellar (layered structures)
what four fall under the classification of polymers?
thermoplastics, thermosets, elastomers or rubbers, composites
thermoplastic polymers
long chains with limited or no cross-linking
behave like plastic, ductile manner
melt when heated and thus are easily remolded and recycled
thermoset polymers
highly cross linked, 3d network structures
generally brittle
decompose when heated and cant easily be reshaped or recycled
elastomers and rubbers
large amounts of elastic deformation
some cross linking
crosslinks allow material to return to original shape without plastic deformation
name some polymer additives
fillers- added to improve tensile strength and abrasion resistance
stabilizers-antioxidants, uv protectants
lubricants- added to allow easier processing, slides throug hdies easier
colorants
flame retardants
thermoplastic
can be reversibly cooled reheated, recycled
heat till soft, shape as desired, then cool
polyethlylene, polyproplene,polystyrene
