Additives
Additives are materials that are added to a polymer to enhance material properties to the desired level or produce a desired change in characteristics. A wide variety of additives such as plasticizers, mineral fillers like TiO2, CaCO3 are currently used in thermoplastics, to expand or extend material properties, enhance processibility, modify aesthetics, or increase environmental resistance. Additives enhance properties like flame retardancy and UV light stability.
Alloy - Two or more immiscible polymers mixed together with or without a compatibilizer, to form a plastic resin having enhanced performance properties.
Amorphous phase – Disordered region of the polymer morphology where polymer chains are arranged in random fashion. At processing temperatures, the plastic is normally in the amorphous state
Annealing - A process of heating up a material at a temperature and holding at that temperature for specific amount of time to permit stress relaxation without distortion of shape. It is often used on molded articles to relieve stresses set up by flow into the molds.
Antioxidants & Antiozonants - These additives are used to resist degradation by oxygen and ozone on the resin materials.
Average Molecular weight (viscosity method) - The molecular weight of the polymer determined by the viscosity of the polymer in solution at a specific temperature. This gives an average molecular weight of the molecular chains in the polymer independent of specific chain length. This usually falls between weight average and number average molecular weight.
Bulk Density - The weight per unit volume of a loosely packed material, such as a molding powder or pellets.
Cast Film - A cast film is made by placing a layer of molten plastic or solution of plastic onto a surface, then solidifying and removing the film from that surface.
Composite - A structural material consisting of reinforcements of materials. Typically, one of the materials is a strengthening agent, the other being a thermoset or a thermoplastic resin.
Compound
A mixture of resin and the ingredients which modify the resin to a form suitable for processing into finished articles.
Compounding
It is a process where additives are incorporated into a polymer to obtain desirable properties for particular uses. Modification of the polymer properties is done by ingredients such as polymeric resins, plasticizers, fillers, reinforcing agents, various stabilizers, lubricants, coloring agents, flame retardants, etc.
Copolymer
It is a polymer of two chemically distinct monomers bonded chemically.
Coupling Agents – It is a material used to enhance the bonding between the polymer and glass fiber or a mineral filler by forming a chemical bridge between them.
Cradle-To-Grave Analysis
It is a methodology that quantifies energy consumption and environmental emissions at each stage of a product's life cycle, from raw material extraction and proceeding through processing, manufacturing, consumer use, and final recycling, reuse or disposal
Crosslinking - The formation of a three dimensional polymer network through interchain reactions resulting in changes in physical properties.
Crystallinity – Uniform and compactness of molecular structure of polymer chains in some resins. These have formation of solid crystals having a definite geometric form.
Curbside Collection
A collection process where consumers place designated recyclables at the roadside or curb, usually in a special container or bag, for collection separate from non-recyclable material such as garbage
Cycle
Complete, repeating sequence of operations for plastics molding.
Cycle Time
In a molding operation, cycle time is the time elapsing between a particular point in one cycle and the same point in the next cycle.
Densification
A process that lowers the volume-to-weight ratio in order to reduce shipping costs. Baling is the most common form of densification, although some handlers of post-consumer plastics granulate or grind collected material.
Density/Specific Gravity
Density and specific gravity are used interchangeably, which is formally incorrect. The difference is the following: density is mass per unit volume of a material; specific gravity is the mass of a given volume of material divided by an equal volume of water at the same temperature. The conversion is: density = specific gravity X 0.99756. The often used English term "relative density" has the same meaning as "specific gravity.
Design for Recycling
This is a process where pre-production planning for safe and efficient recycling by elimination as much as possible, of hazardous and non-recyclable materials from the production process is achieved.
Discards
The components of Municipal Solid Waste (MSW) remaining after recovery for recycling and composting. These discards are presumably combusted or disposed of in landfills, although some MSW is littered, stored, disposed of on site or burned on site, particularly in rural areas.
Elasticity/Plasticity
It is the ability of a material to return to its original state after deformation before the yield point. Plastics in general are elastic in nature. If a material’s yield point is exceeded when stressed, it does not return to its original state after removal of the stress which is permanent deformation by plastic behavior. Plasticity is the inverse of elasticity. Some materials – such as methacrylates – will be broken when they have been strained only a small amount, and while still showing essentially elastic behavior. Other materials – such as polycarbonates – can be stretched many times their original length before they break. The latter have a yield point, and a corresponding yield stress.
Engineering Plastics
All plastics, with or without fillers or reinforcements, which have superior mechanical, chemical and thermal properties compared to commodity resins and are suitable for use, in construction, machine components and chemical processing equipment.
Environmental stress cracking - The susceptibility of a thermoplastic article to crack or craze formation under the influence of certain chemicals and stress.
Extrudate
The product or material extruded through an extruder die, for example, film, pipe profiles, sheets, etc.
Extruder
A machine for producing more or less continuous lengths of plastics sections such as rods, sheets, tubes, and profiles and also strands to then cut and convert them to pellets.
Extrusion
The process of forming continuous shapes by forcing a molten plastic material through a die, attached to the extruder barrel.
Film
Films are distinguished from sheets in the plastics industry only according to their thickness. In general, films have thicknesses no greater than 0.010".
Finish
The surface texture of a finished article, normally given by a mold or die.
Flow
The ability of the molten resin to move or travel. Flow can be influenced by temperature, part geometry, process conditions and tool design.
Foaming
Foaming is the process of producing a cellular or porous plastic by using foaming agents. A foaming agent is a material mixed with or dissolved in a plastic to make it foam. It includes expanding agents that produce gas on heating – such as easily volatile solvents – or chemical blowing agents that produce gas by thermal decomposition. Weight reduction is the percent volume of a foamed part which contains gas instead of resin. High weight reductions result in reduced material properties when compared to low weight reductions.
Forming
It is a process in which the shape of plastic pieces such as sheets, rods or tubes is changed to a desired configuration or geometry.
Glass Transition Temperature (Tg) - The approximate midpoint of the temperature range over which the glass transition i.e. transformation from solid to glassy state takes place.
Hardness
The hardness of a material can be measured by its resistance to scratching or to indentation. Mostly used hardness tests involve the determination of the material resistance to indentation under standardized conditions. A hard indenter of standard shape is pressed into the surface of the material under a specified load. The resulting area of indentation or the depth of indentation is measured and assigned a numerical value. For plastics, the most widely used methods are Ball hardness, Rockwell and Shore methods.
Heat Deflection temperature - The temperature at which a standard test bar (ASTM D648) deflects 0.010 in. under a stated load of either 66 or 264 psi. This test is used to determine approximate continuous use temperature of a plastic material.
Heat Stabilizers - These additives increase the ability of the material to withstand the negative effects of heat exposure, and stabilize the material against breakdown and degradation.
Homopolymer
Homopolymers are polymers which are made up of one single repeated basic unit or (mono)mer.
Hydrolysis - Chemical decomposition of a substance in the presence of water.
Hygroscopic – Polymers which absorb moisture.
Inhibitor - A substance used in low concentration which suppresses a chemical reaction
Injection Molding
The method of forming objects from granular or powdered plastics, most often of the thermoplastic type, in which the materials is fed from a hopper to a heated chamber in which it is softened, after which a ram or screw forces the material into a mold. Pressure is maintained until the mass has hardened sufficiently when cooled, for removal from the mold.
ISO - International Organization of Standardization
Leach - To extract a soluble component from a mixture by the process of percolation.
Linear polymer - A long chain polymer molecule as contrasted to one having many side chains or branches or cross linked structure.
Lubricant - Internal lubricants, without affecting the fusion properties of a compound, promote resin flow. External lubricants promote release from metals which aids in the smooth flow of melt over die and mold surfaces.
Masterbatch - A concentration of a substance (an additive, pigment, filler, etc.) in a base polymer, used to add to a larger batch of polymer to attain certain small percentage for better dispersion.
Mold - (v.) To shape plastic melt or finished articles by heat and pressure. (n.) (1) The combination of core and cavity into which the plastic composition is placed and from which it takes its form. (2) The assembly of all the parts and tools that function collectively in the molding process.
Monomers
A monomer is the molecular unit from which polymers are prepared. A polymer is a molecular chain formed by combining many smaller molecules called monomers.
Oxidation - The addition of oxygen to a compound or the reduction of hydrogen, which normally leads to breakdown of the polymers.
Plasticity
The ability of a material to withstand continuous and permanent deformation by stresses exceeding the yield value of the material without rupture.
Plasticize
To render a material softer, more flexible and/or more moldable by the addition of a plasticizer.
Plasticizer
A substance or material incorporated in a material (usually a plastic or an elastomer) to increase its flexibility, workability or extensibility. Some plasticizers have been known to have detrimental effects on certain types of plastic, end use testing is recommended.
Plastic(s) - A material that contains as an essential ingredient, one or more organic polymeric substances of large molecular weight, is solid in its finished state, and at some stage in its manufacture or processing into finished articles, can be shaped by flow due to heat.
PLC (Performance Level Categories)
As defined by UL: "In order to avoid an excessive level of implied precision and bias, material performances for several tests are recorded as PLC, based on the mean test results (rather than recording the exact numerical results)". PLC levels are assigned to electric properties, tested according to UL 746A
Polymer (Synthetic)
The product of a polymerization reaction. The product of polymerization of single type of monomer is called a homopolymer, monopolymer or simply a polymer. When two different monomers are polymerized simultaneously the product is called a copolymer. The term terpolymer is sometimes used for polymerization products of three monomers.
Polymerization
The process of converting a monomer or a mixture of monomers into a polymer. Addition polymerization is the stepwise addition of a simple repeated unit where monomers are joined together to form long chains. Or, the reaction that yields a product that is an exact multiple of the original monomeric molecule. Condensation polymerization is the combination of functional molecules, leading to the formation of a polymer with the liberation of by-products, usually water.
Polymer Structure
A general term referring to the relative positions, spatial arrangement and freedom of motion of atoms in a polymer molecule.
Polyolefins
The class of polymers made by polymerising relatively simple olefins monomers.
Recycled Plastic - A plastic prepared from discarded articles that have been cleaned and re-ground. Recycled plastic may or may not be reformulated by the addition of fillers, plasticizers, stabilizers, pigments, etc. The percentage in which recycled plastic can be used is also limited by the application requirements.
Reinforcement
An inert fibrous or non-fibrous material incorporated in a plastic to improve or modify mechanical or physical properties.
Reinforced Plastic
A plastic with high-strength fibers embedded in the polymer matrix, resulting in increased strength properties superior to those of the base resin.
Resin (Synthetic)
The term is use to designate any polymer that is a basic material for plastics.
Rheology - Study of the deformation and flow of matter in terms of stress, strain and time.
Shrinkage
The percentage of reduction in overall part dimensions. Shrinkage occurs during the cooling phase of the forming process.
Society of Plastics Engineers, Inc. (SPE)
A technical society for the plastics industry that is a preferred supplier of engineering, scientific and business knowledge required by the SPE membership. Its goal is to promote this knowledge and increase education of plastics and polymers worldwide.
Society of the Plastics Industry, Inc. (SPI)
A trade organization of more than 2,000 members representing all segments of the plastics industry in the United States. SPI's operating units and committees are composed of resin manufacturers, distributors, machinery manufacturers, plastics processors, moldmakers and other industry-related groups and individuals
Stabilizer
A substance used in the formulation of plastics to help maintaining the properties of the material during processing and service life.
Thermal degradation - Deterioration by heat, through chemical breakdown of bonds of the molecule.
Thermoplastics
Materials that become soft when heated and solid when cooled to room temperature. This softening and setting may be repeated many times.
Thermoplastics vs. Thermosets
A thermoplastic is a polymeric material or plastic which becomes soft and formable when heated and rigid when cooled. This process may be repeated a number of times without chemically altering the material. A thermoset is a polymeric material which undergoes irreversible chemical changes when cured through heat, catalysts or ultraviolet light: cross-linking prevents movement of molecular chains after curing. Once cured, the structure cannot be changed.
UV absorber
An additive which protects materials by absorbing UV radiation.
UV stabiliser
Additive which stabilises organic materials against UV radiation.
Virgin Material
Any plastic compound or resin that has not been subjected to use or processing other than that required for its original manufacture.
Viscosity
Viscosity is the resistance to steady flow shown within the body of a material. It is internal friction or the measure of a polymer melt’s resistance to flow. In testing: the ratio of the shearing stress to the rate of shear of a fluid. Which ‘Newtonian viscosity’, the ratio of shearing stress to rate of shearing strain is constant. In non-Newtonian behavior – which is the usual case with plastics – the ratio is not constant but varies with the shearing stress. Such a ratio is often called the apparent viscosity at the corresponding shearing stress. It represents one point on the flow curve.
MFR and MV
MFR, or melt flow rate, is the mass of thermoplastic material extruded in a given time through a defined orifice under specified conditions. MV, or melt viscosity, is a measure of a polymer at a given temperature at which the molecular chains can move relative to each other. It is expressed as the quotient of the real shear stress t and the real rate of shear y. Melt viscosity is considerably dependent on the molecular weight: the higher the molecular weight the greater the entanglements and the greater the melt viscosity.