Reaction Injection Molding (RIM) - A process that involves the mixing of two or more reactive liquid components and injecting into a closed mold at low pressure.

Recycled Plastic - A plastic prepared from discarded articles that have been cleaned and re-ground. Recycled plastic may or may not be reformulated by the addition of fillers, plasticizers, stabilizers, pigments, etc.

Regrind - Waste material from molding and extrusion operations, which has been reclaimed by shredding or granulating.

Reinforced Plastics - A plastic with enhanced mechanical properties due to the addition of high strength fillers imbedded in the composition.

Release Agent - A material added to a compound or applied to the mold cavity, or both, to reduce parts sticking to the mold.

Resin - A pseudo-solid or solid organic material often of high molecular weight. It has a tendency to flow when subjected to stress, usually has a softening or melting range, and usually fractures conchoidally.

Runner - The secondary feed channel in an injection or transfer mold that runs from the inner end of the sprue or pot to the cavity gate.

SMC - Sheet Molding Compound

Sheet - Sheets are made of a continuous phase plastic in a form in which the thickness is very small in proportion to length and width. The thickness is greater than 0.25 millimeters.

Shrink Mark - An imperfection; a depression in the surface of a molded material where it has retracted from the mold.

Slip Agent - An additive that provides surface lubrication during and immediately following processing of the plastic material. It acts as an internal lubricant which will eventually migrate to the surface.

Specimen - A piece or portion of a sample used to make a test.

Sprue - The main feed channel that connects the mold-filling orifice with the runners leading to each cavity gate. Sprue is also the piece of plastic material formed in this channel.

Sprue Gate - The passage through which molten resin flows from the nozzle to the mold cavity.

Stabilizers & Surface Modifiers - Some additives included in this category include antioxidants and antiozonants, antistats, biocides, and fungicides, heat stabilizers, light and UV stabilizers and absorbers.

Stress Crack - A crack, either external or internal, in a plastic caused by tensile stresses less than its short-time mechanical strength.

Structural Foam Molding - The process of molding thermoplastic articles with a cellular core and integral solid skins in a single operation.

Surfactants - The use of these chemicals allows the formation of an emulsion or intimate mixture of otherwise incompatible substances by modifying the surface properties and influencing the wetting and flowing properties of liquids.

TMC - Thick Molding Compound

Tackifiers - Additives used to enhance the adhesiveness or bonding ability of a material.

Thermoplastics - Resins capable of being softened by applying heat, and solidified by removing heat. The process is repeatable.

Thermosets - Resins or plastics compounds, which in their final state are infusible and insoluble. After being fully cured, thermosets cannot be re-softened by heat.

Transfer Molding - A process of forming articles by fusing a plastic material in a chamber, then forcing the whole mass into a hot mold to solidify.

Vacuum Forming - A process whereby a heated plastic sheet is drawn against a mold surface by evacuating the air between it and the mold.

Virgin Material - A plastic material that has not been subjected to use or processing other than that required for its initial manufacture. It can be in the form of pellets, granules, powder, floc, or liquid.

Viscosity - The property of resistance of flow exhibited within the body of a material.

Void - An unfilled space in a cellular plastic which is substantially larger than the individual cells. Can also be an empty space in any material or medium.

Vulcanization - An irreversible process during which a rubber compound, through a change in its chemical structure (for example, crosslinking), becomes less plastic and more resistant to swelling by organic liquids. The resulting elastic properties are conferred, improved, or extended over a greater range of temperature.

Warpage - A non-uniform change in internal stresses resulting in distortion or warp of the material.

Wet Lay-up - A reinforced plastic manufacturing process where the polymer compound is applied as a liquid as the reinforcement is put into place.

Wetting Agent - Wetting is produced when this surface-active agent decreases the cohesion within a liquid. For wetting to occur, the adhesive force between the two phases (solid and liquid) is greater than the cohesive force within the liquid.

Wet Winding - A fiber reinforcement material is coated with a polymer compound as a liquid prior to wrapping on a mandrel in the filament wound manufacturing process.

Whisker - A single-crystal, short fiber.

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