Adiprene
Uniroyal’s trade name for polyurethane based on toluene diisocyanate and polyether glycols.
Allophanate groups
Formed by the reaction between isocyanate groups and urethane groups.
Amines
Ammonia derivatives where one or more hydrogen atoms in ammonia have been replaced by carbon-containing radicals. Amines are used, among other things, as chain extenders (curatives) and catalysts in the manufacture of polyurethanes.
Aliphatics
Acyclic compounds in which the carbon atoms are bonded to each other in open, straight, or branched chains.
Aliphatic isocyanates
Isocyanates based on aliphatic compounds.
Aromatics
Homocyclic compounds with six carbon atoms in the ring, which are unsaturated. Aromatics can consist of several such rings. The simplest aromatic compound is benzene.
Aromatic isocyanates
Isocyanates based on aromatic compounds. They are cheaper than aliphatic ones but discolor upon aging.
Antioxidants
Chemical compounds that are sometimes added to prevent oxidation of, among other things, polyurethane.
Elongation at break
The elongation when the specimen breaks under load.
Pot life
English: “pot life”. The period during which a mixture of prepolymer and chain extender remains castable.
Butanediol
Difunctional alcohol, which is used, among other things, as a chain extender in the manufacture of polyurethanes.
Castomer
Baxenden Chemicals’ trade name for a series of urethane prepolymers.
Hydrogen cyanide
Highly toxic. Can be formed when heating polyurethanes and isocyanates.
Diisocyanates
Contains two isocyanate groups (see isocyanate). O=C=N-R-N=C=O.
Tensile strength at break
The highest tensile stress a material can withstand before it breaks.
Elastomers or elasts
Collective term for rubber and thermoplastic elastomers. According to ISO 1382: “polymeric material that rapidly returns to almost its original dimensions and shape upon unloading after having been subjected to severe deformation by the action of low mechanical stress.”
Modulus of elasticity
E-modulus, Young’s modulus gives the relationship between stress (σ) and strain (ε). For practical use, steel follows Hooke’s law E=σ/ε. Polymeric materials follow Hooke’s law only at very low strains.
Elasticity
The ability of molecular chains to return to their original position when the load ceases.
Ester groups (-COOR)-
Occur in polyester urethanes. Provide good mechanical properties but can impair hydrolysis resistance.
Ether groups -O-
Provide good hydrolysis resistance in polyurethane systems, but particularly soft polyurethanes have lower mechanical properties than corresponding polyester urethanes.
“Green strength”
Refers to the strength at the time of demolding.
Rubber
Elast that is cross-linked or can be cross-linked so that it is practically insoluble (but can swell) in boiling solvents such as benzene and methyl ethyl ketone.
Hydrophilic
Opposite of hydrophobic.
Hydrophobic
Water-repellent
Hydrolysis
From the Greek hydro=water, lysis=decomposition. Certain polyester urethanes are easily hydrolyzed by hot water or steam.
Hydrolysis stabilizer
Carbodiimides added to polyester urethanes to delay hydrolytic degradation.
Hydroxyl
Reactive group -OH
Curative
Chain extender used to cure prepolymers into polyurethane. Multifunctional amines and glycols are used as curatives.
Hardness
The ability of the surface to resist penetration. For polyurethanes, it is most often measured in Shore A or D. There is a certain relationship between E-modulus and hardness.
Isocyanates
Reactive groups – N=C=O, which react, among other things, with hydroxyl groups (-OH) to form urethanes and with amine groups (NH2) to form urea (carbamide).
Blowing agent
Used in the manufacture of cellular plastics. Blowing agents for polyurethanes include hydrofluorocarbons, hydrochlorofluorocarbons, and carbon dioxide (formed by the reaction between isocyanate and water).
Catalysts
Substances that accelerate a chemical reaction without being consumed themselves. For polyurethane production, amines and tin salts are used as catalysts.
Chain extender
See curative
Chain length
The length of the polymer chains. Mechanical properties improve with increasing chain length.
Compressibility
Rubber materials are practically considered incompressible. At high pressures, however, compressibility must be particularly considered for polyurethanes and silicone rubber.
Nitrogen oxides
Hazardous to health. Formed during the combustion of polyurethanes and isocyanates.
LIM
Liquid Injection Moulding.
MDI
Diphenylmethane diisocyanate. An aromatic diisocyanate for the manufacture of solid and cellular polyurethanes. Not as volatile as TDI.
Abrasion resistance
A material’s ability to resist abrasion. Distinguish between abrasion parallel to the surface and “abrasion” caused by incoming material at a large angle of incidence.
Polymer
From the Greek poly=many and mer=unit, i.e., large molecules.
Polyurethane
Polymer containing urethane groups.
Pot life
See pot life
Prepolymer
Not fully polymerized product.
RIM
Reaction Injection Moulding. Often used solely for high-pressure molding.
R RIM
Reinforced Reaction Injection Moulding. Reaction molding of reinforced polymers.
Impact strength
A material’s ability to withstand impact stresses.
Silicone oil
Often used release agent for polyurethane. Causes adhesion problems during bonding and painting.
Slitan
UW-ELAST’s trade name for a series of polyether and polyester urethanes.
Stress
Denoted by σ and is the force F divided by the area A. Often expressed in MPa.
Compression set
Residual deformation after loading.
Thermoelast
Elast in which the cohesive forces necessary for the material’s elastic deformation are of a physical nature and can thus be canceled by heating, whereby the material becomes plastically deformable at elevated temperatures to return to its highly elastic state upon cooling.
Toluene diisocyanate
Commonly occurring aromatic diisocyanate for the manufacture of solid and cellular polyurethanes. Due to volatility and health risks, a polyurethane is often manufactured first.
Trekollan
Trekollan is both a polyurethane material and a former company that is now part of UW-ELAST AB.
Viscoelasticity
The polymer returns, with a certain time delay, to its original shape after loading. The viscoelastic part is mechanically reversible but thermodynamically irreversible.
Vulkollan
Bayer’s trade name for a polymer based on naphthalene diisocyanate and polyester glycols.
Urea groups -NHCONHR
Formed by the reaction between isocyanates and amine groups NH2. Also called carbamide.
Urethane groups -NHCOOR
Formed by the reaction between isocyanates -N=C=O and hydroxyl groups -OH.
Urethane prepolymer
Reactive viscous liquid, usually isocyanate-terminated. Provides, among other things, lower health risks than monomeric isocyanates.
Vibrathane
Uniroyal’s trade name for a series of castable polyurethanes.