Agglomerates Weakly bonded particle clusters. Aggregates Strongly bonded particle clusters. Compatibility Miscibility on a molecular scale. Composites A material consisting of two or more components, which largely retain their identities and yet result in many properties that cannot be achieved with either of the constituents acting alone.

Copolymer A polymer in which chemical combination exists in the main chain between two polymers [A]„ and [B]„. A copolymer can be a block copolymer [AAA... ] [BB... ] or a random copolymer ABAABAB, the latter having no long sequences of A or B units.

Crystallization of polymers The macromolecular chains fold in a regular manner forming ordered structure. Dispersion Break up of agglomerated particles and separation of the resulting fragments to a point where reagglomeration will not occur.

Failure In a tensile stress-strain experiment, the sample is elongated until it breaks. Stress-strain studies are usually relatively slow, of the order of mm/s. Impact strength measures the material's resistance to a sharp blow, typically m/s. In both stress-strain and impact studies, energy is absorbed within the sample by viscoelastic deformation of the polymer chains, and finally by the creation of new surface areas. Glass transition A transition describing the change between glassy and rubbery states in polymers. At the glass transition temperature, the amorphous portions of a polymer soften. Carried out under ideal conditions, glass transition is a type of second-order transition. Graft Long macromolecular chains of a polymer are chemically attached to the base material.

Initiation Radical chain polymerization is a chain reaction consisting of a sequence of three steps-initiation, propagation and termination. The initiation step is considered the production of free radicals by any one of a number of reactions. The initiation involves the addition of this radical to the first monomer molecule to produce the chain initiating species.

Interface A surface formed by a common boundary of filler and matrix that is in contact with and maintains the bond in between. A polymer composite interface consists of a polymer and a nonpolymer. Usually the nonpolymer is a solid phase such as glass, carbon, or boron fibers, steel, or particulates such as calcium carbonate or titanium dioxide. In such a case the polymer cannot interdiffuse into the nonpolymer surface but may bond and adhere to it. Monomers Small molecules that combine with each other to form polymer molecules.

Polymer A long molecule containing atoms held together by primary covalent bonds along the molecule. When one speaks of polymers, one is concerned with materials whose molecular weights may reach into the millions.

Polymerization Reactions by which the monomers combine building up macromolecules.

Thermoplastics Linear or branched polymers, that is, uncrosslinked ones, which soften, melt and flow upon heating. Almost all of the polymers produced by chain polymerization are thermoplastics. There are only a relatively few such polymers which are crosslinked.

Wetting Polymer wets the filler and squeezes into its void spaces, such that losse filler particles disappear and air introduced into the compound by entrapment in the filler agglomerates is replaced.

Young's modulus A parameter characterizing stiffness of materials, which relates the stress to the strain for uniaxial tensile or compressive loading.

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