Glossary

A B C D E F G H I J K L M O S T U Y

ANTIBLOCK   Additive used to give surface of film a rougher texture at a microscopic level. Without additives, film has tacky texture similar to cling wrap. Prevents film from sticking together, or “blocking.”  ANTISTAT   Plastic has a natural tendency to attract static electricity. Additives put in to dissipate static are referred to as antistats. There are many standardized tests, such as MIL B – 81705C to measure the effectiveness of antistatic agents ASTM  American Society for Testing and Materials. www.astm.org BAREFOOT POLYETHYLENE  Resins which have no additives (slip or antiblock.)  BIODEGRADABLE PLASTIC   A degradable plastic in which the degradation results from the action of naturally occurring micro-organisms such as bacteria.There are three standards – EN 13432, ASTM D6400 and ASTM D6954-04 BUTENE  Can be used as a monomer in the formation of polymers, most commonly linear low density polyethylene, hence the name “butane LLD.”  CENTERFOLD Film which is folded on one side and open on the other. Centerfold "A" Wind Centerfold "B" Wind COF (COEFFICIENT OF FRICTION) / ASTM D 1984 Measure of tackiness or slipperiness of a film. There is an inverse relationship between the value of a COF and the slipperiness of the film. In other words, the lower the COF, the more slippery the film.  Low slip      COF greater than 0.45 Medium Slip COF 0.35 to less than 0.45 High slip   COF 0.20 to less than 0.35 Very high slip COF less than 0.15 Three possible combinations: 1. Treat to treat 2. Untreated to untreated 3. Untreated to treated When calling out COF, it is critical to specify the range and surface interface. COMONOMER One of the compounds that constitute a copolymer.   COMPOSTABLE PLASTIC / ASTM D 6400 / EN 13432 Biodegradable by definition and compliant with ASTM D 6400. A plastic that undergoes biological degradation during composting to yield carbon dioxide, water, inorganic compounds and biomass at a rate consistent with other know compostable materials and leaves no visually distinguishable or toxic residues.  COPOLYMER  Joint polymerization of two or more different monomers or polymers.    DART DROP TEST / ASTM D 1709A Determines resistance to puncturing of the film. Measured in grams.   DENSITY    Measure of how closely molecules are packed together. Called out as the number of grams per cubic centimeter. General purpose low density PE films are around .925 gm/cc. Density affects characteristics of film. Density ranges are as follows:  Low Density Under .929 Medium Density Between .930 to .940 High Density Over .940 DIFFERENTIAL SCANNING CALORIMETRY (DSC) MELTING POINT   Used to measure the melting point of plastics. Different test method that vicat softening point, so different values result. DOUBLE WOUND SHEETING   Two plies of sheeting wound together Double Wound Sheeting DYNE LEVEL  Measure of surface tension. Higher level of surface tension is achieved by passing an electrical charge across the film. The higher the value, the greater the amount of tension. Untreated film has a natural dyne level of about 33. For film to accept solvent-based ink for printing, it is necessary to treat film to 38 to 40 dynes. For water-based inks and laminations, a treat level of 45 dynes is required.  ELMENDORF TEAR TEST / ASTM D1922 Originally developed to measure tear resistance of paper, this test measures the resistance to tearing. ETHYLENE C2H4  The basic monomer building block of polyethylene, extracted from either natural gas or naptha. Note: neither of these feedstocks is suitable for deriving gasoline.  EVA  Short for ethylene-vinyl acetate. Also vinyl acetate copolymerized with polyethylene. It is a copolymer that enhances sealability and clarity. The higher the VA percentage, the lower the melting point and stiffness. High percentage EVA’s are popular choice for total batch inclusion bags which must melt often at temperatures less than 200°F. Very low density metallocenes have rendered EVA obsolete for applications requiring fast tack and low seal initiation temperature.  FDA approval  The US Food and Drug Administration never actually approves a resin for prolonged and direct food contact. A resin can only be listed as compliant with CFR 212, section 177.1520, 175:30 (or 21 CFR 177.1630 sections h(1), (ii) ) for prolonged and/or direct contact for food packaging.  FRACTIONAL MELT  Resin which has a melt index less than 1.0, hence the name “fractional.” GAUGE Thickness of film GLOSS 45° /  ASTM D 2457 Measure of how much light is reflected by a film. GUSSET Folds, or “pleats” put into film as it is collapsed. ½ of the total gusset width is on each side. HAZE / ASTM D 1003 Measure of clarity of film. Expressed in percent. For example, a resin which has a haze of 5.5 allows 94.5% of light to pass through the film.  HEXENE   Used as a monomer in the formation of polymers, usually LLDPE resin. Stronger film strength than butene.  HIGH DENSITY POLYETHYLENE (HDPE) Polyethylene resin with a density over .940 gm/cc. Much stiffer than low density polyethylene. Common examples of HDPE are milk jugs, motor oil bottles and plastic grocery sacks.  IONOMER Copolymers of ethylene and acrylic acids that have been neutralized to some degree to form metal salts. The dramatic bond strength from the most commercial brand, Surlyn ® from DuPont, results from an ion which shares orbits with adjacent molecules. IQF  “Individually quick-frozen.” Freezes bagged meat or vegetables rapidly by exposing it to blast of air at approximately –40º F.  J SHEET   Film which looks like the letter “J”. Has a “short” and “long” side.    "J" Sheet "A" Wind   "J" Sheet "B" Wind KOSHER APPROVAL LAYFLAT TUBING   Flexible polyethylene tubing which has been pressed flat. Layflat Tubing LINEAR LOW DENSITY POLYETHYLENE (LLDPE)    Polyethylene which has more crystallinity than LDPE. Can be produced with butene, hexene or octene comonomer for a wide variety of properties usually stronger than conventional LDPE  LOW DENSITY POLYETHELENE (LDPE)  Polyethylene of a density ranging from .915 to .929 grams/cc.  MACHINE DIRECTION (MD) Direction the film is being pulled through a machine MEDIUM DENSITY POLYETHYLENE (MDPE) Polyethylene having a density ranging from .929 to .940 grams/cc.  MELT INDEX (MI)  a.k.a “melt flow index” or “melt flow rate”. Measure of viscosity (resistance to flow) of a resin by ASTM D 1238. The amount of polymer which exits the die in ten minutes is measured in grams. In general terms, the lower melt index resin which has more viscosity will be stronger than a higher melt index and trade off clarity or haze. If the number of grams extruded is less than 1, the resin is referred to as a “fractional melt” (less than 1.0.)  METALLOCENE POLYETHYLENE  Latest generation of resin technology utilizing a metallocene catalyst which is basically tiny particles of positively charged metal ions sandwiched between two rings of carbon atoms that have five atoms apiece.   Metallocene is not a comonomer; it is a catalyst which imparts consistent molecules.   Metallocenes are not necessarily stronger than LDPE or LLDPE.  MIL   One thousandths ( 1/ 1000 ) of an inch expressed as “001”. Metric equivalent is 25.4 microns. MONOMER Small molecule ( ethylene, propylene, styrene, etc. ) that may become chemically bonded to other monomers to form a polymer. OCTENE Comonomer in production of usually linear low density ( LLD ) polyethylene. OTR   Oxygen transmission rate as measured by ASTM D 3985. Measure of the amount of oxygen which passes across the film. SEAL INITIATION TEMPERATURE   Measure of lowest temperature at which the required hot tack and seal strength levels are both achieved. Seal range is the temperature range over which hot tack and seal strength are greater than the acceptable minimum required levels. Maximum hot tack level indicates what maximum loading the sealing material can sustain during the packaging cycle. SECANT MODULUS / ASTM D 882 Measure of stiffness. Higher the number, the stiffer the film. SINGLE WOUND SHEETING.  Single ply of film Single Wound Sheeting     TRANSVERSE DIRECTION Cross direction or sideways dimension 90 degrees orientation to the machine direction    TREAT  a.k.a. corona discharge treatment. Method of raising the surface energy and to some extent etching of films in order to accept adhesives and inks. Most commonly achieved by arcing of electricity across the film. “Corona” refers to the original method of flame treating. ULDPE /VLDPE   Specialized form of linear low-density polyethylene having density between .86 and .90 grams/cc. UVI - ULTRAVIOLET   INHIBITOR  Retards the degrading effect of sunlight on polyethylene.  YIELD  Net weight per 1,000 lineal feet of film. (Handy Math) back to top of page