Glossary

Plastics Glossary - N

Nest plate A retainer plate with a depressed area for cavity blocks.

Neutralization Number mg of KOH required to neutralize the acid in 1 g of oil.

Newton Viscometer Instrument that measure the resistance of a fluid to motion between two parallel sliding plates. A Newton viscometer is often used on high-viscosity materials.

Newton’s Law of Similarity Material systems are dynamically similar when the ratio of forces acting upon corresponding mass elements at corresponding times is constant. Such forces include pressure, inertia, gravity, viscosity, elasticity, and surface tension.

Newtonian Fluids Fluids whose viscosity is independent of the rate of shear. Pure liquids, true solutions, and dilute suspensions are generally Newtonian.

NF National Formulary.

NIOSH Abbreviation for the National Institute for Occupational Safety and Health.

Nip Distance between rolls in mill or calender.

Nonelectrolyte Substance whose water solution will not noticeably conduct an electric current.

Nonionic Surfactants Covalent emulsifying agent that will not ionize in solution; they include alkyl ethers, alkylar ethers, thio-ethers, esters, and amides.

Non- Newtonian Suspensions In viscous flow, the viscosity of a non- Newtonian suspension is a function of the rate of shear and duration of the shear. Non-Newtonian classes of materials include Bingham plastics, pseudoplastics, dilatants, thixotrop, and rheopectics.

Nonpolar Having no concentration of electrical charges on a molecular scale; thus, incapable of significant dielectric loss.

Nonpolar Liquids Liquids whose molecules possess little or no dipole moment.

Nonpolar Having no concentration of electrical charges on a molecular scale; thus, incapable of significant dielectric loss.

Non-return valve Valve that permits material to flow in one direction and closes to prevent back flow. In front of injection screw. The valve assembly on the screw tip that keeps plastic from returning back down the screw flights during injection.

Normal Hydrocarbons Hydrocarbons with straight, not branched, molecular chains.

Notch Sensitivity The extent to which the sensitivity of a material to fracture is increased by the presence of a surface notch or sudden change in section.

Nozzle back Another name for the sprue break where the carriage is retracted during the cycle to pull the nozzle away from the mold sprue bushing.

Nozzle contact point The point where the nozzle seats against the mold when the carriage is moved forward.

Nozzle In injection molding, the orifice-containing plug at the end of the injection cylinder which contacts the mold sprue bushing and conducts the molten material into the mold.

Nucleating agent Nucleating agents are additives that provide sites for crystal formation in the polymer melt. Certain pigments are nucleators. Certain other additives commonly found in colorants (calcium stearates) will neutralize nucleators.

Nylon resin Family of thermoplastic resins that are strong, tough, abrasion resistant, have good fatigue resistance, good lubricity, and low coefficient of friction. Types include 6, 66, 6/10, 6/12, 11, 12. Semi-crystalline material.