Polymer Characteristics Flashcards
fractures while deforming elastically.
Brittle polymer
the initial deformation is elastic, then followed by yielding and a region of plastic deformation.
Plastic
is totally elastic; large recoverable strains produced at low stress lev
Elastomer
corresponds to the stress at which fracture occurs
tensile strength
property of materials that exhibit both viscous and elastic characteristics when undergoing deformation.
Viscoelasticity
determines whether the deformation is elastic or viscous.
rate of strain
formation prior to cracking
Craze
during crazing there is plastic deformation causing formation of ______ and ________
Microviods, fibrillar bridges
the capability of a material to withstand a suddenly applied load and it is expressed in terms of energy
Impact strength
is the weakening of a material caused by repeatedly applied loads.
Fatigue
the energy required to tear apart a cut specimen such as polymers
Tear strength
represents a material’s resistance to scratching, penetration, dents and so on.
Hardness
_______ of polymers is a process associated with partial alignment of their molecular chains.
Crystallization
These chains fold together and form ordered regions called ______
Lamellae
occurs at relatively low
stress levels on the stress–strain curve.
Mechanism of Elastic Deformation
chain molecules in amorphous regions elongates in the direction of the applied tensile stress.
Mechanism of Elastic Deformation
is the amount of crystallized regions in a material.
Degree of Crystallinity
Corresponds to the neck extension process
Predeformation by drawing
An important stiffening and strengthening technique that is employed in the production of fibers and films
Predeformation by drawing
_________ of semicrystalline polymers can lead to an increase in the percent crystallinity and crystallite size and perfection.
Heat-treating or annealing
eliminates internal stresses and ensures better mechanical and thermal properties.
Heat-treating (or annealing)
Any rubbery material composed of long chainlike molecules, or polymers, that are capable of recovering their original shape after being stretched to great extents.
Elastomers
Is a chemical process used to harden rubber.
Vulcanization
It works by forming cross-links between sections of polymer chain which results in increased rigidity and durability.
Vulcanization
