Tuesday, July 16, 2013

More Plastics Glossary Terms - Atlantic Poly

If you deal in plastics, as in manufacture them, sell them, use them, order them 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. Last week we listed some of the terms, here are  few more….

Calcium Carbonate: A filler and extender used in thermoplastics. It occurs naturally in the form of minerals such as calcite, chalk, limestone, marble, and whiting.

Cast: The cast film process involves the extrusion of molten polymers through a flat slot die to form a thin film or sheet. This film of molten polymer is then quenched by passing through a set of chill rolls (typically water-cooled). The film quenches immediately, and the edges are trimmed prior to winding or stacking.

Centerfold: Folding a film along the length to obtain a two layered product with half the width.

Cfold: Folding of a film along the length to obtain a two layered product with flaps folded on each side of the folded product. The folded film profile looks like a stapled pin from a stapler.

Chill Roll: A cored roll, usually temperature controlled with circulating water, which cools a molten polymer web on contact before winding.

Coextrusion: Fabrication of a multi-layer film by pumping materials through separate extruders and then merging the extruded material into a common die assembly. These die assemblies are constructed to maintain distinct material layers with fusion occurring at the boundaries due to the pressures and temperature of the extruded material.

Color Concentrate: A plastics compound which contains a high percentage of pigment to be blended into base resins. The term masterbatch is sometimes used for color concentrate as well as for concentration of other additives. Comonomer: A monomer which copolymerizes with another monomer.

Copolymer: A polymer resulting from the polymerization reaction of two chemically different monomers.

Corona Treat: The process by which the surface energy of plastic films, foils and paper is increased in order to allow improved wettability and adhesion to inks, coatings and adhesives.

Degradation: A deleterious change in the chemical structure, physical properties, or appearance of a plastic caused by exposure to heat, light, oxygen, or weathering.

Density: Weight per unit volume of a substance usually reported in g/cm3 or lb/ft3.

Die: A steel block containing an orifice through which plastic is extruded, shaping the extrudate to the desired form.

Die Gap: Distance between the metal faces forming the die opening.

Die Lines: Vertical or horizontal marks on the extrudate and in the finished product caused by damaged die elements or by contamination held up in the die land.

Differential Scanning Calorimetry (DSC): Method used to determine thermal histories of polymers such as melting points and glass transition points.

Drawdown: In extrusion, the process of pulling the extrudate away from the die at a linear speed higher than that at which the melt is emerging from the die, thus reducing the cross-sectional dimensions of the extrudate.

Elasticity: The property (of plastic materials) of recovering original size and shape after deformation.

Elastomer: A material which, at room temperature, can be stretched under low stress to at least twice its original length and, upon immediate release of the stress, will return with force to its approximate original length.

Elongation: Deformation caused by stretching; the fractional increase in length of a material stressed in tension.

Embossing: The process used to modify the surface texture of a smooth film to achieve special surface properties such as surface area, coefficient of friction, gloss, adhesion, etc., and alter the bulk density of the film. For example, embossing forms a waffle from a pancake.

Erucamide: A fatty acid-based slip additive used in polyolefin resins.

Ethylene Vinyl Acetate (EVA): Copolymeric member of the polyolefin family derived from random copolymerization of vinyl acetate and ethylene.

Extruder, Single Screw: Basic machine consists of a screw, barrel, drive mechanism, resin feed arrangement and controls. The constantly turning screw augers the resin through the heated barrel where it is heated to proper temperature and blended into a homogeneous melt. Before the melt can leave the barrel, it must pass through a breaker plate and screen pack. The melt is then extruded through the die into the desired shape.

Extrusion: Compacting and melting a plastic material and forcing it through an orifice in a continuous fashion.

Blown Film: Process involves extruding a continuous thin walled tube of plastic and inflating it immediately after it leaves the die. The pressure is such that the tube stretches, increasing its diameter and reducing its wall thickness to desired gauge. Air is trapped within the blow tube (bubble) between the die and collapsing rolls which convert it to layflat film to facilitate winding onto a roll.

Cast Film: Process by which a polymer is extruded from a slot die onto the surface of a water-cooled roll. Film is clearer and has more sparkle than blown film.

Coating: Coating of a substrate by extruding a thin film of molten polymer and pressing it onto the substrate.

For information on anything plastic, contact Atlantic Poly.