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Terms in this set (108)
Energy needed to get a reaction started.
The existence of two or more different physical forms of a chemical element.
A copolymer made up of macromolecules comprising two species of monomeric units in alternating sequence.
Having a different value when measured in different directions.
The magnetic moments of atoms or molecules, usually related to the spins of electrons, align in a regular pattern with neighboring spins (on different sublattices) pointing in opposite directions.
A type of polymer chain configuration (stereoisomer) wherein side groups are randomly positioned on one side of the chain or the other.
A randomly ordered molecular structure which does not have a sharp melt point; instead amorphous materials soften gradually as the temperature rises. Amorphous thermoplastics are often clear or translucent.
Atomic Mass Unit.
Atomic Packing Factor (APF)
The volume of atoms in a selected unit cell divided by the volume of the unit cell.
Body-centered cubic packing describes a way in which atoms (considered as hard spheres) pack together to fill space. It comprises a cube of 8 atoms, with another atom at the center.
Binary Phase Diagram
A temperature composition map which indicates the equilibrium phases present at a given temperature and composition.
Identical repeat units are clustered in blocks along the chain.
A polymer having a molecular structure of secondary chains that extend from the primary main chains.
Fracture that occurs by rapid crack propagation and without appreciable macroscopic deformation.
Little/No plastic deformation, rapid crack growth can be catastrophic.
The direction and magnitude of the slip caused by a single dislocation.
Impact test in which the standard specimen contains a notch where an impact occurs to complete a three-point bending.
The number of immediately adjacent atoms to a given atom.
A polymer consisting of two or more different monomers.
Covalent Dislocation Movement
Covalent bonds are directional and resist movement.
Crack will grow if max stress at a point exceeds the critical stress.
Creep Rate (Cold Flow)
The tendency of a solid material to move slowly or deform permanently under the influence of mechanical stresses. It can occur as a result of long-term exposure to high levels of stress that are still below the yield strength of the material.
Critical Resolved Shear Stress
Stress required to cause slip in pure metal single crystal. Depends on crystal structure, atomic bonding characteristics, temp, orientation of slip plane.
A bond that links one polymer chain to another.
Permanently bonded, tangled polymers. A crosslinked polymer can never melt. It's the most flexible and the most dense polymer.
A solid that is made up of crystals in which particles are arranged in a regular, repeating pattern.
The arrangement of the atoms in a material into a regular repeatable lattice.
Any of the seven groups (cubic, hexagonal, rhombohedral, tetragonal, orthorhombic, monoclinic, and triclinic) of crystals. Classified according to the possible relations of the crystal axes.
Degree of Polymerization
The number of repeating units within the chain.
A factor that determines the rate of total movement of a substance by diffusion, it's a property that depends on the particle size of the substance and the nature of the medium in which diffusion is occurring.
How fast the foreign mass can transfer across and area.
The line extending along the extra partial plane of atoms in an edge dislocation.
A force that encourages change in a specific direction.
A mode of fracture that is attended by extensive gross plastic deformation.
Able to be deformed without losing toughness; pliable, not brittle.
The transition from ductile to brittle behavior with a decrease in temperature.
Ability of a material to stretch or deform under a load without breaking.
A line defect; a slip of the part of crystal over an atomic plane relative to another part is perpendicular to this plane.
Occurs when an object changes shape because of a stress being applied, but snaps back into shape when the stress is removed.
Polymers with viscoelasticity and weak intermolecular forces.
The arrangement of electrons in an atom.
Tending to acquire electrons and form negative ions in chemical reactions.
Tending to lose electrons and form positive ions in chemical reactions.
A degradation of material surface due to mechanical action.
A homogeneous solid mix of atomic and/or chemical species, forming a joint super-lattice, by striking a unique atomic percentage ratio between the components.
Upon cooling one liquid phase is transformed into two solid phases.
A two-phase micro-structure resulting from the solidification of a liquid having the eutectic composition; the phases exist as lamellae that alternate with one another.
Solid phase transforms to two different solid phases.
The failure of a structure subjected to repeated loading at stress levels below those required to cause general yielding. The process of fatigue may involve the initiation and growth of cracks from stress concentrations. However, the initiation stage is often by-passed since micro-cracks are usually introduced into a structure during processing.
Gap forms, pitting like corrosion.
The number of stress cycles that will cause a fatigue failure at some specified stress amplitude.
Stress below which there is no fatigue failure whatever the number of cycles.
The stress to which a metal can be subjected for a specified number of cyclic changes of stress.
Face-centered cubic describes a way in which atoms pack together to fill space. The first layer (A) consists of an hexagonal array of atoms. The next layer (B) sits in the hollows of the first layer. The third layer (C) does not duplicate either A or B layer, giving an ABCABC... structure.
The amount of flexural stress a material can withstand before breaking. measured through the bend test.
Glass Transition Temperature
One of the most important properties of any epoxy and is the temperature region where the polymer transitions from a hard, glassy material to a soft, rubbery material.
The interface separating two adjoining grains having different crystallographic orientations.
The third step in the formation of crystallites, which is dependent on temperature and can be described using the arrhenius equation.
Refers to various properties of matter in the solid phase that give it a high resistance to its shape changing when force is applied.
Cold works a material. Repeated hardness test at same spot makes material harder and score increase.
Hexagonal Close-Packed (HCP)
Most common non-cubic bravais lattice, 6 atoms form a hexagon on both the top and bottom and a single atom positioned in the center between the two hexagonal rings.
A measure of the energy absorbed during the fracture of a specimen of standard dimensions and geometry when subjected to very rapid (impact) loading; Charpy and Izod impact tests are used to measure this parameter, which is important in assessing the ductile-to-brittle transition behavior of a material.
A fracture that follows the grains of the material. If the material has multiple lattice organizations, when one lattice ends and another begins, the fracture changes direction to follow the new grain. This results in a fairly jagged looking fracture with bumpy edges.
Intermediate Solid Solution
A solid solution or phase having a composition range that does not extend to either of the pure components of the system.
Atoms migrate from an interstitial position to a neighboring one that is empty , this occurs more rapidly than vacancy diffusion because interstitial atoms are smaller and more mobile.
Interstitial Solid Solution
A solid solution wherein relatively small solute atoms occupy interstitial positions between the solvent or host atoms.
Any spot on a phase diagram where three phase are in equilibrium.
Having the same structure. When applied to a phase diagram, indicating that the solid phase has the same structure and hence complete solubility at every composition.
A type of polymer chain configuration (stereoisomer) wherein all side groups are positioned on the same side of the chain molecule.
The edge lengths and angles of a unit cell.
Mechanical analog for the mass balance with which one can calculate the amount of each phase present in a two phase microstructure.
Polymer in which the molecules form long chains without branches or cross-linked structures.
The structural features of an alloy that can be seen under a microscope.
Modulus of Elasticity
A coefficient of elasticity of a material, expressing the ratio between a unit stress and the corresponding unit strain caused by the stress, as derived from Hooke's law and represented by the slope of the straight-line portion of the stress-strain diagram.
The molecular weight of a compound is the sum of the atomic weights of all atoms in the molecule.
A simple molecule that can combine with other like or unlike molecules to make a polymer.
A polymer in which monomers are connected in a three-dimensional cross-linked network.
System does not reach equilibrium while cooling. Less creep resistant because different melting temperatures at boundaries.
The onset of a phase transition in a small region such as with the formation of a bubble or of a crystal from a liquid.
The void space among close-packed, hard-sphere atoms or ions for which there are six nearest neighbors; an octahedron (double pyramid) is circumscribed by lines constructed from centers of adjacent spheres.
During precipitation hardening, aging beyond the point at which strength and hardness are at their maxima.
Reactive materials become unreactive.
A three phase reaction where a solid phase and liquid phase transform to a single solid phase upon cooling.
Any part of a sample with uniform composition and properties.
Small scratch or dent, horizontal surfaces. Reduce by smoothing surfaces.
A material with a molecular structure made up of long strands of similar units bonded together.
A more specific molecular structure with a sharp melting point which is difficult to thermoform., but they have a lower coefficient of friction.
Strain and Stress
Strain is the response of a system to an applied stress. When a material is loaded with a force, it produces a stress, which then causes a material to deform.
A phenomenon of exactly zero electrical resistance and expulsion of magnetic flux fields occurring in certain materials, called superconductors, when cooled below a characteristic critical temperature.
A periodic structure of layers of two (or more) materials. Typically, the thickness of one layer is several nanometers.
A manufacturing process where a plastic sheet is heated to a pliable forming temperature, formed to a specific shape in a mold, and trimmed to create a usable product.
'Molecular deterioration as a result of overheating'. At high. temperatures the components of the long chain backbone of the polymer can begin to separate. (molecular scission) and react with one another to change the properties of the polymer.
A class of copolymers or a physical mix of polymers (usually a plastic and a rubber) which consist of materials with both thermoplastic and elastomeric properties.
Polymers that can not be reheated with the same level of flow.
Polymers which only solidify after being chemically set.
The temperature at which a substance acquires or loses some distinctive property, in particular superconductivity.
The property of materials that exhibit both viscous and elastic characteristics when undergoing deformation.
A liquid's resistance to flowing.
Process of treating rubber or rubberlike materials with sulphur at great heat to improve elasticity and strength or to harden them.
Point a which, when exceeded, a material will no longer completely return to its original shape after removing the applied load.
Temperature at which the particles stop moving.
The temperature at which the vapor pressure is equal to the atmospheric pressure.
The change of a gas to a liquid.
A molecule or a part of a molecule that contains both positive and negative charged regions.
Dipole - Dipole Force
Intermolecular force between polar molecules.
The basic mechanism by which certain materials (such as iron) form permanent magnets, or are attracted to magnets.
A polymer compound built of hydrocarbon base monomer units. Besides carbon and Hydrogen the following atoms may be in polymer molecules: Oxygen, Nitrogen, chlorine, fluorine, silicon, phosphorous, and sulfur.
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