ABS (acrylonitrile – butadiene – styrene) Acrylonitrile and styrene liquids and butadiene gas are polymerized together in a variety of ratios to produce the family of ABS resins.
Acrylate Resins See acrylic resins.
Acrylic Plastic A thermoplastic polymer made by the polymerization of esters of acrylic acid or its derivatives. The acrylic group is dominated by two resins – one used principally for blending with other resins and as a fiber [(poly)Acrylonitrile (PAN)] and the other used principally for molding (PMMA).
Acrylic Fiber A manufactured fiber in which the fiber-forming substance is any long chain synthetic polymer composed of at least 85% by weight of acrylonitrile units [-CH2-CH(CN)-].
Acrylic Resins (1) A polymer of acrylonitrile, used in the production of manufactured fibers, as a fabric finish and as a size. (2) A synthetic resin prepared from acrylic acid or from a derivative of acrylic acid. Polymers of acrylic or methacrylic esters, sometimes modified with nonacrylic monomers such as the ABS group. The acrylates may be methyl, ethyl, butyl, or 2-ethylhexyl. Usual methacrylates are methyl, ethyl, butyl, laural, and stearyl. The resins may be in the form of molding powders or casting syrups and are noted for their exceptional clarity and optical properties. Acrylics are widely used in lighting fixtures because they are either slow burning or self-extinguishing and do not produce harmful smoke or gases in the presence of flame.
(poly)Acrylate A thermoplastic resin made by the polymerization of an acrylic compound.
Acrylonitrile (1) A colorless, volatile, flammable liquid used as a raw material in the manufacture of acrylic polymers and fibers. (2) A monomer with the structure (CH2:CHCN). It is most useful in copolymers. Its copolymer with butadiene is nitrile rubber, and several copolymers with styrene exist that are tougher than polystyrene. It is also used as a synthetic fiber and as a chemical intermediate.
(poly)Acrylonitrile (PAN) A base material or precursor used in the manufacture of certain carbon fibers. PAN-based carbon fibers have a ribbon like structure and possess high strength (400 GPa, or 60 × 106 psi, tensile modulus).
Actuator A mechanical device for moving or controlling something.
Advanced Material Engineered material (see Materials Science).
Aggregate Inert particles such as sand, gravel, crushed stone, or expanded minerals, in a concrete or plaster mixture.
Alloy A substance composed of two or more metals, or of a metal and a non-metal constituent; a mixture of metals; for example, brass, which is an alloy of copper and zinc. But when mercury is one of the metals, the compound is called an amalgam.
Alpha Rockwell Hardness Index of the resistance of a plastic to surface penetration by a specified indenter under specified load applied with a Rockwell hardness tester. Higher values indicate higher indentation hardness. (ASTM D-785)
Amalgamation Combination, mix, or blend of components or characteristics consolidated into unit.
Angle (plane angle) The spatial relationship between two straight lines which meet; the point of meeting is the vertex of the angle. Angles are measured in degrees or, alternatively, in radians. A complete revolution is 360 degrees (360°). If two lines are parallel, the angle between them is zero. A straight line forms an angle of 180° and a right angle is 90°.
Angle 109.47° The decimal approximation of 109°28’16". This angle is ubiquitous among the minimal-surface cellular structures found in nature, including bubbles in a froth. It is the bond angle of carbon atoms in the diamond structure. It is also the common angle formed by joining the center of a tetrahedron to its vertices.
Angle 120° The interior angle of the hexagon. It is prevalent among cellular structures found in nature, including bubbles in a froth.
Angular (1) having an angle or angles. (2) consisting of, situated at, or forming an angle. (3) of, pertaining to, or measured by an angle.
Angular Momentum Product of the moment of inertia of a body and its angular velocity.
Anisotropic Exhibiting properties with different values when measured in different directions. For example, the tendency of a material to react differently to stresses applied in different directions.
Arch A structural device that supports a vertical load by translating it into axial, inclined forces; a means of spanning an opening by resolving vertical pressure into horizontal or diagonal thrust.
Area The extent of a surface, measured in units of length squared. For example, the area of a rectangle is the product of its length and breadth.
Area-minimizing Principle A soap film contained by any fixed boundary will acquire its minimum free energy when it reaches equilibrium. As the free energy of a film is proportional to its area, the area also will be minimized.
Array An ordered arrangement of items.
Assembly The process of joining parts by any of several methods.
Asymmetric porosity Porosity that is not evenly aligned. For example, the random distribution of voids found in foamed materials.
Axial In a direction parallel to the long axis of a structure.
Axial Strain The strain in the direction that the load is applied, or on the same axis as the applied load.
Axiom (postulate) In a mathematical or logical system, an initial proposition or statement that is accepted as true without proof and from which further statements, or theorems, can be derived. In a mathematical proof, the axioms are often well-known formulae for which the proof has already been established.
Axis (1) A line about which a figure is symmetrical. (2) One of the fixed reference lines used in a graph or a coordinate system. (3) A line about which a curve or body rotates or revolves. (4) The line of intersection of two or more coaxial planes.