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Glossary of Terms
Agents added to films to reduce the tendency for films to “block,” which is an undesirable attraction between surface layers of wound film (commonly roll form) that makes it difficult to separate during the converting process. Anti-block works to disrupt the surface of film on a microscopic level, significantly reducing the static force that results when two smooth surfaces are in contact. This is often seen as a suction effect: for example, two layers of glass with liquid between them. In this case, air acts as the liquid causing static interaction between film layers.
Barrier – refers to plastic film that is manufactured in a multilayer process (see coex film) containing unique layers formulated to impede oxygen/moisture, which can damage or shorten the shelf life of sensitive products packaged within (e.g., meats, cheese).
High Barrier – commonly referred to as films with high levels of moisture barrier performance.
Blow Up Ratio (BUR)
Unique term within the blown film industry; a numerical value that refers to the mathematical ratio of the diameter of a blown film bubble (at its largest point) in comparison to the diameter of the extrusion die it comes out of. The higher the BUR, the larger the bubble diameter is in relation to the die.
Common manufacturing process in which raw plastic is melted/blended and extruded through a circular die and blown up using air to desired size and thickness to form consistent flexible plastic films with unique properties; often referred to as tubular film extrusion.
The manufacturing process involving the extrusion of polymers melted through a slot or flat die to form a thin, molten sheet or film. The polymer is then pulled from the die(becoming thinner as it is drawn) and cooled continuously on chilled rolls.
Coefficient of Friction (COF)
The force resisting the relative motion of solid surfaces sliding horizontally over one another; measured as a dimensionless ratio.
Manufacturing process in which multiple layers of raw plastic are melted and extruded through a circular die to form a singular film consisting of unique layers of different polymers. When combined in this fashion, the resulting film can possess properties unattainable by mixing various polymers as one product.
Plastic film that is formed by combining multiple layers of polymers to generate one film with vastly different properties as each layer contributes undiluted unique properties. For example, combining moisture barrier of an HDPE resin with the puncture resistance and sealing properties of LLDPE.
Process to increase the surface energy of plastic films to allow improved wettability and adhesion of inks, coatings and adhesives.
A component of the blown film extrusion process that controls the amount of raw plastic resin that is metered into the extruder to be mixed; it consists of a load cell, hopper, auger/sleeve and sphincter valve to precisely measure and add raw materials critical to the film formulation.
A technique which provides a textured surface to plastic film. Embossing can change the physical characteristics of the film, as well as increase the thickness of the material without adding weight.
Component in the film extrusion process that is responsible for melting and mixing raw materials in the manufacturing of plastic film. Resin enters as solid pellets, metered by the dosing unit, and then melted under high temperature and pressure to generate a homogeneous mixture that becomes the flexible plastic product/layer.
The half of a product package in which the product is formed/pressed into the plastic creating a secure mold shaped by the product itself; common for packaging products that are of irregular shape.
The cover or seal of a container; lidding films work to maintain an environment in modified atmosphere packaging (MAP). Commonly, lidding is used with barrier applications to eliminate contamination/spoilage of products within the container by preventing oxygen from disrupting the modified atmosphere in which the product is preserved, e.g., meats, fish, dairy products, fruits and vegetables.
A film that consists of a single layer of polymer(s) that is uniform in its composition.
Moisture Vapor Transmission Rate (MVTR)
Also referred to as water vapor transmission rate (WVTR); a measure of the permeation of water vapor through a film. Many packaging and film applications exist that demand moisture control. Moisture resistance is measured in a specialized chamber where it is divided vertically into two environments by the substrate/barrier film: a dry atmosphere on one side and a moist atmosphere on the other. The value is measured by detecting the level of moisture that permeates through the film and contaminates the dry atmosphere, reported in g/100in2/24hr.
The half of a product package in which the formation of a seal around the entire product can be generated via direct contact with the forming web containing the product that has been formed/molded into its half of the package.
Oxygen Transmission Rate (OTR)
A measure of the permeation of oxygen through a film. Many packaging and film applications exist that demand oxygen control. Oxygen resistance is measured in a specialized chamber where it is divided horizontally into two environments by the substrate/barrier film: a nitrogen atmosphere on one side and an oxygen-rich atmosphere on the other. The value is measured by detecting the level of oxygen that permeates through the film and contaminates the nitrogen atmosphere, reported in cc/100in2/24hr.
Any of a class of polymers produced from a simple olefin(also called an alkene with the general formula CnH2n) as a monomer. Polyethylene and polypropylene are common polyolefins.
The measurement of thickness variation around the circumference of the bubble. Measurements are taken with a specialized camera and generated while cycling around the bubble during production to capture and record production data. Common industry quality is ~10%; our standard to enter production state is 4%.
- LDPE – Low-density polyethylene (LDPE) is a thermoplastic made from the monomer ethylene.
- MDPE – Medium-density polyethylene (MDPE) is a type of polyethylene defined by a density range of 0.926–0.940 g/cm3. It is less dense than HDPE, which is more common.
- HDPE – High-density polyethylene (HDPE) or polyethylene high-density (PEHD) is a polyethylene thermoplastic made from petroleum.
- LLDPE – Linear low-density polyethylene (LLDPE) is a substantially linear polymer (polyethylene) with significant numbers of short branches, commonly made by copolymerization of ethylene with longer-chain olefins.
- EVA – Ethylene-vinyl acetate (EVA), also known as poly(ethylene-vinyl acetate) (PEVA), is the copolymer of ethylene and vinyl acetate. The weight percentage of vinyl acetate usually varies from 10 to 40%, the remainder being ethylene.
- Metallocene – A metallocene is a compound typically consisting of two cyclopentadienyl anions bound to a metal center in the oxidation state II, with the resulting general formula (C5H5)2M. Closely related to the metallocenes are the metallocene derivatives, e.g., titanocene dichloride, vanadocene dichloride. Certain metallocenes and their derivatives exhibit catalytic properties.
- ULDPE – An ultra-low-density polyethylene (ULDPE).
- EMA (Ethylene-Acrylic-Acid) / EAA (Ethylene-Methacrylic-Acid) Copolymers – EAA and EMA are produced by free radical copolymerization of ethylene with acrylic acid and methacrylic acid, respectively. They have excellent adhesion to metals such as aluminum and are used in metal laminates, as well as precursors to ionomers.
- Surlyn – Surlyn is an ionomer resin providing clarity, toughness and versatility. Surlyn also provides an excellent barrier for oily or greasy products.
- Polypropylene – Polypropylene (PP), also known as polypropene, is a thermoplastic polymer used in a wide variety of applications, such as packaging and labeling, plastic parts and reusable containers of various types, and automotive components.
- EVOH – Ethylene vinyl alcohol (EVOH) is a formal copolymer of ethylene and vinyl alcohol. EVOH copolymer is defined by the mole percent ethylene content: lower ethylene content grades have higher barrier properties; higher ethylene content grades have lower temperatures for extrusion. The plastic resin is commonly used as an oxygen barrier in food packaging.
- Nylon – Nylon is a generic designation for a family of synthetic polymers, more specifically aliphatic or semi-aromatic polyamides. They can be melt-processed into fibers, films or shapes. In films, it is mostly used for food packaging.
- Center fold sheeting – Two layers with a fold on one end and a cut edge on the other.
- J-sheeting – Two sheets of film with a fold on one edge and cut on the other. Each side on the cut edge will be a different length.
- Single wound sheeting – Single sheet of film.
- Double wound sheeting – Two layers of film cut on both edges.
- Flat tubing – Two sheets of film with uncut or folded edges on both sides.
Agents added to films to reduce the surface coefficient of friction for films, which can be used to enhance processing or end-use customer applications. Any desired slip level can be achieved from high to low, based on polymer structure and additive dosing. These are often combined with additives such as anti-static and anti-blocking agents to provide improved surface performance characteristics. All slip-containing films can be approved for direct food contact.
Stand-Up Pouch (SUP)
Refers to a package format/design in which the bottom of the package is formed in such a way that the pouch can stand up on its own, presenting a package that does not require additional components to achieve desired marketing or product presentation requirements. These can often be integrated with functional components such as customer-friendly zippers, re-closures, tear notches and hang hole features.