LECTURE 3 (ME PREP) Flashcards
(23 cards)
Polymer name with recycle code of 4
Low-density polyethylene
Calculate the energy for vacancy formation in X [eV/atom], given that the equilibrium number of vacancies at 1174 °C is 3.9 x 1025 /m3. The atomic weight and density for X are, respectively, 77.5 g/mol and 7.15 g/cm3.
0.906 eV/atom
An additive which is particularly important for polyvinyl chloride (PVC) because it reduces glass temperature and provide internal lubrication.
plasticizer
Polymer name with recycle code of 3
polyvinyl chloride
A polymer structure where adjacent linear chains are joined one to another at various positions by covalent bonds.
CROSS-LINKED
A special group of polymers in which molecular chains are entangled but not interconnected. They can be easily melted and formed into useful shapes.
Thermoplastics
Polymer name with recycle code of 2
High-density polyethylene
An additive that prevent deterioration of the polymer due to environmental effects.
stabilizer
A special group of polymers that decompose rather than melt upon heating. They are normally quite brittle due to a relatively rigid, three-dimensional network structure.
Thermosets
In general, strongest polymer group is __________ .
Thermosets
The most widely used technique for processing thermoplastics.
extrusion
a point defect characterized by an absence of an atom from its normal location in a perfect crystal structure
[vacancy]
defects characterized by groups of atoms in irregular positions
[linear defects]
an atom from the crystal that is crowded into an interstitial site
[self‑interstitial
a small void space that under ordinary circumstances is not occupied.
[interstitial site]
_____ a special type of grain boundary across which there is a specific mirror lattice symmetry
______it exists in multiphase materials, in which a different phase exists on each side of the boundary
[twin boundary]
[phase boundaries]
______ a homogeneous mixture made up of solid components in equilibrium with each other
_______impurities where atoms of the parent or solvent metal are bigger than the atoms of the alloying or solute metal, the smaller atoms fit into interstices i.e. spaces between the larger atoms.
[solid solution]
[interstitial impurities]
_______a lattice irregularity having one or more of its dimensions on the order of an atomic diameter.
_______ the element or compound present in greater amount in an alloy
[crystalline defect]
[solvent]
Plastic materials that contain a relatively high volume percentage of small pores.
FOAMS
Polymer name with recycle code of 1.
polyethylene terephthalate
A class of organically based materials that consists of long chain molecules, usually with a carbon “backbone” and with other elements or structural units attached as side groups.
POLYMERS
Polymers that are easily recycled.
THERMOPLASTICS
The following are characteristics of polymers, EXCEPT
a. good thermal insulators
b. good corrosion-resistant
c. light weight
d. good electrical conductors
D. good electrical conductors
