Glossary of Plastics Terms Continued...

22 Jul 2013

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If you deal in plastics or need them in your business, there are some terms you will need to know. Over the next few blog posts, Atlantic Poly, a plastic bag and products company in MA, would like to acquaint you with some of the more necessary plastics terms. The last two weeks we listed some of the terms, here are  few more...

Foam: Process for producing plastic sheet or molded article with a cellular construction. Either a chemical or gaseous blowing agent is introduced into the polymer melt while the melt is being prepared in the extruder barrel. As the plastic melt exits the die, it expands a predetermined amount forming a cellular wall.

Film: Sheet material having a nominal thickness not greater than 10 mil.

Flame Retardant: Reactive compounds and additive compounds to render a polymer fire resistant. Reactive compounds become an integral part of the polymer.

Gauge: Thickness of plastic film measured in decimal inches or mils.

Gel: Small globular mass which as not blended completely into the surrounding material resulting in a fault in the film or sheet.

Glass Transition Temperature: The temperature at which a reversible change occurs in an amorphous polymer when it is heated to a certain temperature and undergoes a rather sudden transition from a hard, glassy, or brittle condition to a flexible or elastomeric condition.

Gloss: Brightness or luster of a plastic resulting from a smooth surface.

Gravure Printing: The depressions in an engraved printing cylinder or plate are filled with ink, the excess raised portions being wiped off by a doctor blade. Ink remaining in the depressions is deposited on the plastic film or other substrates as it passes between the gravure roll and resilient back-up roll.

Haze: Cloudiness in plastic film. Measured as percent haze, anything below 5 percent is generally considered high clarity.

Heat Sealing: The process of joining two or more thermoplastic films or sheets by heating areas in contact with each other to the temperature at which fusion occurs, usually aided by pressure.

High-Density Polyethylene: This term is generally considered to include polyethylene's ranging in density from about 0.940 to 0.960 and over.

Homopolymer: The result of the polymerization of a single monomer, a homopolymer consists of a single type of repeating unit.

Jfold: Folding of a film along the length to obtain a two layered product with one layer wider than the other.

Lamination: Bonding of a polymeric or non-polymeric substrate to a polymeric film using heat and pressure.

Linear Polymer: A polymer in which the monomeric units are linked together in linear fashion with little or no long chain branching. Examples are linear low-density polyethylene and high-density polyethylene.

Linear Low-Density Polyethylene: Includes polyethylene's ranging in density from 0.915 to 0.935.

Low-Density Polyethylene: This term is generally considered to include polyethylene's ranging in density from about 0.915 to 0.925. In low density polyethylene's, the ethylene monomeric units are linked in random fashion, with the main chains having long and short side branches. This branching prevents the formation of a closely knit pattern, resulting in material that is relatively soft, flexible and tough, and which will withstand moderate heat.

Masterbatch: A concentrated blend of pigment, additives, filler, etc. in a base polymer.

Melt Fracture: Is a phenomenon of melt extrudate in which the surface appears rough or wavy upon exit from the die. Melt fracture may appear uniformly or in certain sections only.

Melt Index: The number of grams, of a thermoplastic resin which can be forced through a 0.0825 inch orifice when subjected to 2160 grams force in 10 minutes at 190°C.

Melting Point: The temperature at which a resin changes from a solid to a liquid.

Modulus of Elasticity: The ratio of stress to strain below the yield point of the material.

Molecular Weight (MW): The sum of the atomic weights of all atoms in a molecule.

Molecular Weight Distribution (MWD): The relative amounts of polymers of different molecular weights (MW) that make up a specific polymer.

Mono layer: A homogenous film formed by pumping molten polymer from an extruder through a die assembly to form a film or sheet.

Neck-In: In extrusion coating, the difference between the width of the extrusion die opening and the width of the coating on the substrate.

Nip: The V-shaped gap between a pair of calender rolls where incoming material is nipped and drawn between the rolls.

Octene: A comonomer used in the production of linear low-density polyethylene's.

Offset Printing: A printing process in which the image to be printed is first applied to an intermediate carrier such as a roll or plate, then is transferred to a plastic film or molded article.

Oleamide: An ivory-colored powder used as a slip additive in polyolefin's.

Orange Peel: An uneven surface texture of a plastic article or its finished coating somewhat resembling the surface of an orange, see Melt Fracture.

For information on any plastic products, contact Atlantic Poly.