The polyurethanes (PUR) are synthetic polymers that are characterized by the presence in the chain of urethane groups similar to those which are obtained by reaction between an isocyanate and an alcohol. You are obtained through a complex synthesis that involves the chemical reaction between polyisocyanates and polyols, in the presence of necessary additives (catalysts, surfactants, blowing agents, flame retardants, fillers, anti-aging agents, colorants, antistatic agents and separating agents). From a structural point of view, the PUR plastics are not „pure“, it is rather a composite polymer chemical structure.
The urethane group, which gives its name to the whole family of materials, it is often only a secondary part of the macromolecule, so much so that there are also PUR urethane group or for which the structural profile is mostly determined by characteristics other than those of the structure urethane. This explains why there are so many types of polyurethane materials: there are flexible foams (PUR-W), the rigid foam (PUR-H), the structural foam (PUR-I) and the full PUR (PUR-M). The polyurethanes are known mainly as foams, elastomers, and molded parts of large dimensions.
CHARACTERISTICS AND APPLICATION FIELDS
The particularity of isocyanates is constituted by the fact that the isocyanate groups are very reactive: they can react with active hydrogen compounds, with compounds without reactive hydrogen and between them. The rate of reaction with the reactive partners depend so much on the structure of the same partners as the structure of the whole molecule. During the main reaction you can create a secondary chain reaction, thus forming the other chemical structures that can influence a lasting material properties. For the production of PUR are possible two processing systems: the first consists in stirring the whole amount of polyisocyanate with the polyols and dosage of additives, thus making it react in one step (one shot method); the second consists in transforming before the entire dose of polyisocyanate with a portion of polyols and subsequently mixing the substance obtained by the remaining polyols and the necessary additives (prepolymerization method). Regardless of the system used, the possibility of influencing the reactivity of the components of polyisocyanate and polyol and the wide range of available additives allow the use of various processing techniques: casting, spraying, expansion molding, extrusion, lamination, coating spinning.
Like all organic materials, also PUR are fuels: for their use and storage are subject to the general fire precautions generally taken for flammable industrial products. The PUR-W are little stable to plastic deformation in the presence of compressive stresses, while the PUR-H to present a relatively high deformation stability, in addition to the very low thermal conductivity and the ability to provide fixed links with almost all the flexible cover layers or rigid. The PUR-I can only be expanded to moldings, they are highly reactive and may present the core and surface devoid of cells. The PUR-M are used as molded parts, sheets, films and coatings; the liquid starting components can harden at room temperature or at higher temperatures (from 60 ° C to 130 ° C). They have a range of hardness from 10 Shore A to 70 D.
The PUR-W are shown for the production of upholstered furniture, mattresses, interior of motor vehicles and technical articles (noise and shock absorbers panels). The PUR-H are used for the production of sheets for acoustic insulation, cold storage and prefabricated walls. The PUR-I are particularly required for the realization of external bodywork parts, technical articles for the industry and for the sport. The PUR-M are used for the realization of gaskets, rings, rotor bearings, clutches, wheels, screeners funds, coatings for equipment and coatings for rollers, as well as in shipbuilding and automotive construction.
Shown below are the most common PUR trade names available at LIMA.
|LM940||BLACK ADIPOL 72|
|LM941||BLUE ADIPOL 80|
|LM942||ORANGE ADIPOL 90|
|LM943||AMBER ADIPOL 95|
|LM944||HONEY ADIPOL 60|
Shown below are the most common trade names for the PUR material.
Please remember that LIMA can provide both generic materials and materials covered by trademark (ie that show the TM or ® endorsements), based on the requirements of the customer. If the customer wishes to details made of plastic material covered by trademark, LIMA will stock up directly by the holding company of the said trademark.