A
Abrasion Resistance:
The measurement of material loss when samples are abraded by a given size grinding wheel or belt for a specific period at a given load. Can be misleading and tests under actual conditions are a much b...
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ASTM:
American Society for Testing and Materials....
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A Scale:
Measurements of hardness for Polyurethane are generally made using hand held Durometers or Shore A meters, giving readings between 10A and 90A. Harder grades will use the D Scale meters. IRHD ar...
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Adiprene (Registered trade mark of Chemtura):
A range of high performance polyurethane elastomers, originally introduced by Dupont....
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Aliphatic Polyurethanes:
More expensive than the more common Aromatic Polyurethanes, Aliphatics suffer less from discolouration due to UV attack. They also offer better physical properties in some cases but are regarded...
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Air traps:
These tend to be created when air running in front of the flowing liquid polyureathane is trapped against undercuts in moulds. Venting, tilting moulds, vacuum casting or “over casting&rdqu...
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Ambient Temperature:
The typical environment temperature surrounding the component under consideration....
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B
BDO:
Abbreviation for 1,4 Butanediol, a Glycol Chain Extender....
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Bad Mix:
The correct component ratios have not been used, resulting in a material with poor mechanical properties. A “Cheesy” consistency is often the first observation and the material can b...
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Bending Modulus:
The force required to induce bending around a specific radius, giving a measure of stiffness....
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Bleeding:
The migration of plasticizers, waxes or similar materials to form a film or beads on the surface of the polyurethane....
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Blemish:
A mark or slight surface imperfection, which impairs appearance but generally does not affect performance....
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Blisters:
A raised spot on the surface or a separation between layers usually formed by trapped air or solvent....
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Bond:
An exceptionally strong joint between two materials, which can be stronger than the materials being joined. Bond strength can be more important than the polyurethane quality..e.g. it is no use h...
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Brand:
A mark, symbol or logo may be added to a mould (in reverse), or may be hot stamped into the moulded surface of a moulding, to give manufacturing or ownership details, part numbers etc....
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Buffing Marks:
Polyurethane is often cast oversize or with Runners or Risers, to allow excess air to trap within a sacrificial layer. This layer can be machined away or in some cases abraded away by Grinding, ...
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Butt Joints:
Polyurethanes, typically in strip form, can be joined (Thermoplastic Polyurethanes can be heat welded) and where the plain edges are brought together, this is termed a Butt Joint....
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Blow holes:
true blow holes are created when moisture has reacted with the isocyanate to give off carbon dioxide. When controlled, this can be a good thing, in that foams can be created but generally in hot...
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Bottom Feed or Fill:
Since air inclusions can be a problem in the final polyurethane moulding, various methods of filling the mould from the bottom, rather than the top or side can be utilized to help carry the air ahead ...
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C
C Scale:
a little used hardness range for elastomers, conversion to A scale is possible....
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Cast:
High performance polyurethanes are generally hot cast. The raw materials are heated and mixed (preferably under vacuum in computer controlled mixing and dispensing machines) and are poured , ie ...
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Catalyst:
A material, normally metal based, that initiates or accelerates the rate of chemical reaction during the polyurethane process. The liquid materials become solid quicker or gain demould strength ...
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Cavities:
Moulds are produced with one or multi-cavities or impressions. Lower unit costs are achieved by increasing the number of cavities....
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Centrifugal Casting:
A variation on the normal casting method, used to produce high quality thin sheet and mouldings requiring high definition and all the benefits of a thermoset polyurethane. High speed spinning re...
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Chute Linings:
Polyurethane linings have shown themselves to be exceptionally resistant to the severe abrasion encountered in metallic chutes where minerals, metals or grains are impacting and sliding in huge tonnag...
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Coefficient of Friction:
The ratio of the force required to move an object across a surface to the weight of the object. Hard Polyurethanes with Coefficients of Friction as low as 0.2 are possible, whereas soft Polyuret...
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Cold Flex:
Low temperatures affect the properties of Polyurethane but without degradation. Below 0 degrees C, an increase in Young’s modulus, with a corresponding increase in Shore Hardness, tensile and te...
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Cold Mould Effect:
When the mould temperature is slightly below the requires level (some mould materials lose heat quickly, especially in thin sections, when removed from an oven for casting), the final product can have...
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Compression Set:
When a material has been subjected to a compressive force for a period of time, after the release of that force, the material will recover but not to the its original size. The resultant deforma...
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Cracking:
A sharp break or fissure in the elastomer surface. Often a result of excessive strain (eg due to rapid shrinkage), not to be confused with cuts created by knife trimming. Cracks near flex points...
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Crosslinking:
Diisocyanate polyaddition reaction process that forms a cured elastomer from the polymer....
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Curing Agent:
Common terminology for the Chain Extender or Cross Linking Agent, which when mixed with the Prepolymer results in the chemical reaction that produces the Polyurethane. Diamines, especially Moca ...
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Cut Resistance:
The ability of Polyurethane to withstand the cutting action of sharp instruments (See Cut Tear Resistance). Polyurethane resists “Digging In” of sharp objects extremely well and tend...
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Cycle Time:
The time taken to complete a full moulding cycle, from mould preparation, application of release agent, loading of inserts, assembly of the mould, heating to pouring temperature, dispensing or hand mi...
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D
D Scale:
Harder polyurethanes (generally 95A+) and plastics are measured on D scale Durometers or Shore hardness machines. 95 Shore A is approx 45 Shore D. Better hardness definition is possible....
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Debond:
Where a bond fails, generally through poor preparation or the working conditions or loadings are too severe for the bond strength. Heat build up due to flexing when overloaded or , in the case o...
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Deburring bowls:
Vibratory plant for the polishing or deburring of metal components, lined with polyurethane because of its outstanding abrasion resistance and noise reducing qualities....
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Degassing:
The liquid raw materials for producing polyurethane are often hygroscopic (absorb water) and when the liquid components are mixed by hand air is introduced to the mix, causing bubbles. Degassing...
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Demould Time:
The interval between the dispensing or casting of the liquid polyurethane into the mould and the point at which the polyurethane solid has sufficient strength to allow the component to be stripped fro...
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Dewatering panels:
Vibratory screens or trommels using Scandura Polyurethane dewatering modules and mats allow fine particles such as sand to have excess water removed at rapid rates, whilst standing up to the very abra...
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Dip Coating:
It is possible to retard the cure of a polyurethane mixture by using solvents. Components can then be dipped into the solution and after the solvent evapourates, the polyurethane coating will cu...
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Draft Angle:
To aid stripping from moulds, if possible, the inclusion of a slight taper in the right direction, will help component removal and speeds up the cycle time. Typical draft angle is 2 degrees....
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Dumb Bell:
An “Hour Glass” shape where the centre width is less than the width at its two ends. Test specimens cut from sheet 2.2mm thick are cut with a Dumb Bell standard shape for Tensile, Mo...
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Dunnage:
Stillages and pallets carrying components in need of protection utilize polyurethane mouldings and polyurethane coated steel to separate and hold goods firmly but gently in position during transit.&nb...
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Durometer:
An instrument for measuring the hardness of polyurethanes and rubbers by measuring the resistance to penetration of an indentor into the surface of the material. Results expressed as “Duro...
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Dynamic Fatigue:
The loss in physical properties of a polyurethane when continually subjected to flexing or cyclic stress....
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Dynathane:
Microcellular polyurethane foam with outstanding physical and dynamic properties. (Dynathane is the registered trade mark of Hyperlast ). It is used in spherical bearing seals, crane and l...
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E
Elastic Limit:
The limiting extent to which an elastomer may be stretched or deformed and yet return approximately to its original length or shape after removal of the deforming force....
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Elastollan (registered trade mark of Elastogran BASF):
A range of high performance thermoplastic polyurethanes (TPU’s), suitable for extrusion and injection moulding. Good physical properties and excellent cosmetic qualities are achieved in ma...
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Elastomer:
An elastic, rubber-like material that has the ability to return to shape after being deformed....
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Elongation at Break:
Polyurethanes are tested by pulling specific size samples with a suitable laboratory test machine, until the sample breaks. The percentage increase in length at the break point is a useful measu...
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Exotherm:
Heat generated by chemical reaction. The heat generated during the chemical reaction when manufacturing Polyurethane, is an example of an Exothermic Reaction....
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Extrusion:
TPU (Thermoplastic Polyurethane) granules are heated and driven under pressure by a screw, forcing the hot material through a die to form specific profiles, tubes, solid cord etc. Cooling by wat...
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F
Filler:
A material added to the polymer mix to lower cost or to change a particular quality. E.g. fillers are added to print rolls to aid the grinding process. In some cases, the use of the filler...
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Film:
Thin sheets of Polyurethane, less than 1mm thick, are normally referred to as Films. More often than not, the film polyurethanes are thermoplastic and can be welded....
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Fire Retardant:
Polyurethane materials used in high risk fire areas, such as mines, can be manufactured with Fire Retardant Additives that will reduce the rate of burn and smoke emission and normally the material wil...
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Flash:
Material protruding from a moulded part where a mould joint line or vent is evident. Flash is normally removed from moulded parts by knife trimming or abrading with emery cloth....
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Flex Cracking:
Repeated bending or flexing of Polyurethanes can lead to surface cracking. Formulations can be arrived at that will lessen the possibility of flex cracking, if resistance is key to the component...
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Flex Life:
The relative ability of a polyurethane material to withstand dynamic bending stresses....
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Flexibility:
The ability to be bent repeatedly without cracking....
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Fungicide:
Fungi inhibiting agent that can be added to polyurethane formulations. Ester based polyurethanes are particularly susceptible to fungi attack....
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H
Hydrolysis:
In humid conditions, polyurethanes can suffer from attack from hydrolysis. Mainly a problem with Ester based polyurethanes, the material is degraded, sometimes rapidly, suffering cracks and fizz...
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Hysteresis:
Constant flexing of elastomers, including polyurethane, creates heat build up within the material. When a stress is applied to the material, there is small time lag before the material takes up ...
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M
MDI:
Abbreviation for Diphenymetyhane Diisocyanate....
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MbOCA (MOCA):
Abbreviation for 4,4 Methylene bis (o-chloroaniline), a Diamine crosslinking agent that produces polyurethanes with excellent physical properties. Responsible processors will handle with extreme...
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Masterbatch:
To improve the ratio control where small quantities of one component are involved, a preliminary mix of two or more of the component constituents can be made in a larger batch, which will enable bette...
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Mildew:
Fungal growth or mold growth on the surface....
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Modulus, 100%:
The stress required to stretch the elastomer by 100%. A commonly quoted physical property for means of material comparison. Similarly with the 300% Modulus figure....
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Monomer:
A simple compound that can react to create a polymer....
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Moulds:
Typically machined aluminium or steel moulds are used for casting solid elastomer parts but Fabricated Steel moulds, GRP moulds or Polyurethane Reverse casts from Masters, can all be used, subject to ...
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P
PPL:
Short for Polyurethane Products Ltd, one of Europe’s largest polyurethane moulding and processing companies, based in Retford, Nottinghamshire, England....
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Part Mould Costs:
Most Polyurethane Moulders charge a Part Mould Cost, which gives joint ownership of moulds. The moulder is generally investing mould design time and holds the copyright to the mould design and w...
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Pigments:
Colouring agents added for cosmetic reasons mainly but they can also reduce UV degradation, act as Colour Coding for components. Careful selection required if Food Contact is a feature of the ap...
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Plasticizer:
An additive which can change the physical and chemical properties of a polymeric compound. Typically used in polyurethane formulations to lower hardness and increase flexibility. Caution, ...
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Plate Finish:
The moulded surface of the polyurethane will reflect the mould or hot plate metal finish. Generally, a Plate Finish will result from a “Commercially Smooth” but not polished, hotplat...
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Polyethers:
The common polyethers used in the manufacture of solid polyurethane elastomers are the Polytetramethylene Glycols (PTMEG) and Polypropylene Glycols (PPG). PPG’s are lower cost materials an...
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Polyesters:
The polyester most widely used for the production of solid polyurethane elastomers is Polyethylene Adipate. Mixed polyesters , such as Polyethylene Propylene Adipate are fairly common....
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Polyureas:
Fast reacting sytems , normally used in Spray applications. They allow quick coating, in thick layers and offer excellent physical properties. Polyureas do not suffer from the problems enc...
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Post Cure:
After the initial cure that brings the polyurethane to a strength where demoulding can take place, the moulded component is placed in a circulating hot air oven at a controlled temperature for a speci...
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Pot Life:
Once the reaction initiating agent is added, there is a period of time before the polymeric compound reaches a stage where the hardening material becomes too stiff to pour as a liquid material. ...
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Pot Life:
Once the reaction initiating agent is added, there is a period of time before the polymeric compound reaches a stage where the hardening material becomes too stiff to pour as a liquid material. ...
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PPG:
Polypropylene Glycols (see Polyethers)...
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Prepolymer:
Isocyanate reacted with all or a portion of Polyol....
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PTMEG:
Abbreviation for Polytetramethylene Glycol (see Polyethers)....
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R
RIM Polyurethanes:
Reaction Injection Moulded Polyurethanes are produced in closed moulds, the highly reactive materials being shot into the mould from high or low pressure mixing and dispensing machines. The mate...
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Release Agents:
To prevent the polyurethane from adhering to the mould or hot plate surfaces, Release Agents based on Silicone or Wax are sprayed, brushed or rolled onto the mould surface. Semi- Permanent mould relea...
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Rotational Coating:
A method of applying polyurethane to rollers using a special mixing and dispensing machine traversing back and forth above a rotating roll between centres. The liquid polyurethane is Thixotropic...
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S
Scraper Blade:
Strips of polyurethane or moulded profiles, used to remove materials from the surface of moving conveyor belts for continuous cleaning....
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Screen Mat/Module:
Vibratory separating equipment utilizes polyurethane tensioned mats or modules with apertures that allow the grading of particle sizes or the de-watering of minerals. The process is extremely ar...
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Shore A:
Hardnesses of polyurethanes and rubbers are tested using an indenter meter, E.g. Durometer. Softer polyurethanes , up to 90 Shore A, can be measured fairly accurately with hand held meters but h...
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Shrinkage:
Thermoset polyurethanes shrink towards an imaginary centre by typically 1.5%-2%. Heat is the major factor affecting the shrinkage rate. Moulds are manufactured with an allowance for shrink...
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T
TDI:
Isocyanates based on Toluene (Tolylene)Diisocyanate. These materials are used with various curatives or cross linking agents to create huge range of polyurethane elastomers. Softer grades ...
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Thermoplastic:
Materials that can be softened by heating and whilst softened, can be shaped by flow, E.g. Injection Moulding and Extrusion or joined by welding processes E.g. heat welding or RF welding....
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Thermoset:
Materials that have undergone a chemical reaction involving heat and/or catalyst, the result of which is a cross linked state unaffected by temperature until the decomposition point is reached. I.e. c...
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TPU:
Abbreviation for Thermoplastic Polyurethane....
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Tufthane:
Designers and manufacturers of polyurethane Dunnage, mainly for the automotive industry....
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V
Vacuum Casting:
Components required to be bubble free may need to be cast into a mould that has been evacuated by vacuum. The process best suits long Pot Life materials but it is possible to fill direct from a ...
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Voids:
The absence of material from an area, usually due to mixed in air or trapped air. The use of modern mixing and dispensing machines and good mould design, with correct venting, will usually elimi...
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Vulkollan (trademark of Bayer Sciences):
NDI Ester polyurethanes with superb dynamic properties. The original polyurethane developed by Otto Bayer. Vulkollan is still the best performing solid tyre material for fork lift trucks e...
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