All
| Term | Definition |
|---|---|
| Flexural Strength |
Resistance of a plastic material to cracking or breaking during bending. |
| Flight |
The outer surface of the helical ridge of metal on an extrusion or injection molding screw. |
| Floating Platen |
Moveable platen(s) between the stationary platen and actuated platen on a vertically operating compression press. |
| Flow |
During processing by injection, compression, or transfer molding, the flow of a plastic is measurement of fluidity. |
| Flow Lines |
Distinctive surface marks caused when two flow fronts meet and weld together during molding or film extrusion. |
| Flow Rate |
The ASTM condition of 190 |
| Foam |
Process for producing plastic sheet or folded 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. |
| Fome-Cor® |
Fome-Cor Board is an extruded polystyrene foam board with white or black clay coated liners. Fome-Cor is the original graphic arts foam board - it is perfect for die cutting and provides a compressed edge that stays closed, it is uniquely embossable, and incudes a broad selection of specialty products. Fome-Cor is a registered trademark of Alcan Composites USA. |
| Fractionation |
A method of determining the molecular weights distribution of polymers based on the fact that polymers of high molecular weight are less soluble than those of low molecular weight. Tow basic methods in use are precipitation fractionation and extraction fractionation. |
| Free Radical |
An atom or group of atoms having at least one unpaired electron. Most free radicals are short lived intermediates with high reactivity and high energy, difficult to isolate. They play a role in many polymerization processes. |
| Frostline |
In the extrusion of blown film, a ring-shaped zone of frosty appearance located at the point where the resin solidifies, caused by a reduction in film temperature below the melting point of the resin. |
| Gate |
Opening through which the plastic enters the injection mold cavity. |
| Gate Mark |
Blemish on the molded part by the mold gate. |
| Gatorfoam® |
Gatorfoam is an extruded polystyrene foam board bonded between two layers of wood-fiber veneer. Gatorfoam is the original, heavy-duty graphic arts board. It has an excellent reputation for great performance, offers 5' x 10' large format capabilities, and its new, bright white facer is the brightest board of its kind and great for digital and screenprinting. Gatorfoam is a registered trade mark of Alcan Composites USA. |
| Gauge |
Thickness of plastic film measured in decimal inches or mils. |
| Gel |
Small globular mass which has not blended completely into the surrounding material resulting in a fault in the film or sheet. |
| Gel Permeation Chromatography |
A developed column chromatography technique employing a stationary phase (gel) in the presence of a diluent which is a nonsolvent for the polymer. The polymer to be analyzed is introduced at the top of the column and then is diluted with a solvent. The polymer molecules diffuse through the get at rates dependent on their molecular size. As they emerge from the bottom of the column, they are detected by a differential refractometer coupled to a recording chart, on which a molecular size distribution curve is plotted. |
| 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. |
| Gradient Tube Density |
A method for measuring densities of very small samples, often used in the plastics industry, A vertical glass tube (the gradient tube) is filled with a heterogeneous mixture of two or more liquids, the density of the mixture varying linearly or in other known fashion with the height. A drop or small particle of the specimen is introduced in the tube and falls to a position of equilibrium which indicates its density by comparison with positions of known standard samples. |
| Granular |
Composed or coarse particles. Often used in reference to Granular LLDPE. |
| 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. |
| Guide Pins |
In compression, transfer, and injection molding, hardened steel pins that maintain proper alignment of the mold halves as they open and close. |
| Gussets |
The inward fold in the sides of bags which reduce the width of the bag and allow the bags to assume a rectangular form when opened. |
| Haze |
Cloudiness in plastic film. Measured as percent haze, anything below 5 percent is generally considered high clarity. |
| Heat Distortion Point |
The temperature at which a standard test bar deflects a specified amount under a stated load. |
| 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. |
| Heater Bands |
Electrical heating units shaped to fit extruder barrels, injection molding cylinders and the like, for heating the plastic material to the desired temperature. |
| Helix Angle |
The angle of the flights on an extruder screw. |
| Hexene |
A comonomer (hexene-1 or 4-methyl pentene-1) used in the production of linear low-density and high-density polyethylene. |
| High Load Melt Index |
The ASTM condition of 190 |
| High-Density Polyethylene |
This term is generally considered to include polyethylenes ranging in density from about 0.940 to 0.960 and over. Whereas the molecules in low-density polyethylene are branched in random fashion, those in the higher density polyethylenes have fewer side branches, resulting in more rigid material with greater strength, hardness, chemical resistance, and higher softening temperature. |
| Hmw High-Density Polyethylene |
High molecular weight high-density polyethylene is usually defined as a polyethylene with a density of 0.940 or greater and a flow rate of 1 to 20 (190 |
| Homopolymer |
The result of the polymerization of a single monomer, a homopolymer consists of a single type of repeating unit. |
| Hopper |
In polymer processing, the container holding a supply of molding material to be fed to the screw or ram. The hopper may be intermittently filled or continuously fed. |