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Term |
Definition |
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Narrow Mouth
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A finish of a plastic container in which the diameter is small relative to the diameter of the body.
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Neck
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The part of a container where the shoulder cross section area decreases to form the finish.
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Neck Bead
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A protruding circle on a container at the point where the neck meets the finish, the diameter of which usually equals the outside diameter of the closure.
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Neck Insert
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Part of the mould assembly which forms the neck and finish. Sometimes called Neck Ring.
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Neck-in
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In extrusion coating, the difference between the width of the extruded web as it leaves the die and the width of the coating on the substrate.
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Needle Blow
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A specific blow moulding technique where the blowing air is injected into the hollow article through a sharpened hollow needle which pierces the parison.
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Nest Plate
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A retainer plate with a depressed area for cavity blocks used in injection moulding.
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Nip
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The V formed where the pressure roll contacts the chill roll.
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Nitriding (Gas)
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The surface hardening of certain alloy steels by heating the steel in an atmosphere of nitrogen (ammonia gas) at approximately 9500F. A very hard (70+Rc) case depth of .007" to .0 15" results which is wear-resistant. Process is commonly used for barrel inside diameters, screws and valve components.
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Nitriding (ION)
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The surface hardening of certain alloy steels by heating the steel (to approximately 600 OF) in an atmosphere of hydrogen gas, adding an electrical charge to the steel and nitrogen gas, allowing a bombardment of the positively charged steel by hydrogen and nitrogen gas ions. This creates a hard (70+Rc) wear resistant, case hardness to a slightly greater and more uniform depth than gas nitriding with less distortion or contamination of the work piece. Process is commonly used on screws and valve components.
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Nitrile Resins
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This family of resins started to appear in the late 1960s and early 1970s. They are called barrier resins since one of their prime attributes is their resistance to the transmission of gas, aroma or flavor, making them useful in packaging applications. These thermoplastic resins are composed of acrylonitrile [CH2CHCN] along with comonomer such as acrylates, methacrylates, butadiene [CH2CHCHCH2] and styrene [C6H5CHCH2]. Both straight copolymers and copolymers grafted onto elastomeric backbones are available.
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No Flow Temperature
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The temperature at which the viscosity of a material is so high that it effectively cannot be made to flow.
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Nonpolar
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Having no concentrations of electrical charge on a molecular scale, thus, incapable of significant dielectric loss. Examples among resins are polystyrene and polyethylene.
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Non-Return Valve
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A device mounted at the discharge end of an injection screw that uses a sliding ring to allow flow of plastics in one direction only. On screw recovery it allows flow forward. On injection stroke it allows no flow and makes the screw perform like a plunger.
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Nonrigid Plastic
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A non-rigid plastic is one which has stiffness or apparent modulus of elasticity of not over 50,000 p.s.i at 25ºC when determined according to ASTM test procedure D747-43 T.
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Nonwoven
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Nonwoven, solid, flat sheet consisting of bundled glass filaments or glass staple fibres (surfacing mat)
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Nose Cone
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The conical surface at the discharge end of an extrusion screw.
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Notch Sensitivity
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The extent to which the sensitivity of a material to fracture is increased by the presence of a surface in homogenity such as a notch, a sudden change in section, a crack, or a scratch. Low notch sensitivity is usually associated with ductile materials, and high notch sensitivity with brittle materials
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Nozzle
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The hollow cored metal nose screwed into the extrusion end of (a) the heating cylinder of an injection machine or (b) a transfer chamber where this is a separate structure. A nozzle is designed to form under pressure a seal between the heating cylinder of the transfer chamber and the mould. The front end of a nozzle may be either flat or spherical in shape.
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Nozzle Tip
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A device that threads into the injection nozzle and adapts between the nozzle and the sprue bushing of the injection mould.
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