{"id":807,"date":"2025-01-08T08:33:23","date_gmt":"2025-01-08T13:33:23","guid":{"rendered":"http:\/\/www.hotmarksystem.com\/?page_id=807"},"modified":"2025-01-08T08:48:35","modified_gmt":"2025-01-08T13:48:35","slug":"introduction-to-polyurethane","status":"publish","type":"page","link":"\/\/www.rushplease.com\/introduction-to-polyurethane","title":{"rendered":"Introduction to Polyurethane"},"content":{"rendered":"

WHAT IS POLYURETHANE ?
\nUnlike most other polymers such as polyethylene, polystyrene and polyvinyl
\nchloride which are polymers of the monomeric units ethylene, styrene and vinyl
\nchloride respectively, polyurethanes are not polymers with repeated units of
\nurethane in the regular manner and do not generally have an empirical formula that
\nis representative of all. They are basically polymeric reaction products of
\npolyhydroxy polymers such as polyether (or polyester) polyols and isocyanates. In
\nshort, they are polymers containing the urethane linkage ( -NH-CO-O- ) which are
\nin no way the predominat chemical linkage in the polymers.
\nThe majority of the polyurethanes made and used are foams which can range from
\nthe super-soft and flexible to the hard and rigid. They can be produced as slabstock
\nor moulded into different shapes and sizes.<\/p>\n

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Blowing agent \u53d1\u6ce1\u5242
\nA substance incorporated in the polymerising reaction mixture between a diisocyanate and a polyol to form gas bubbles, thereby producing foam.
\n\uf06e Branching \u63a5\u679d\u6750\u6599
\nLateral extension points in a polymer chain.
\n\uf06e Catalyst \u50ac\u5316\u5242
\nsubstance which accelerates the reactions of chemicals without being
\nconsumed itself.
\n\uf06e Chain extenders \u6269\u94fe\u5242
\nSubstances which lengthen the main chain of a polymer molecule causing
\nend-to-end attachments.
\n\uf06e Cross-linking \u67b6\u6865\u5242
\nFormation of bridges between different polymer chains.
\nSolid polyurethanes \u786c\u56fa\u6001\u805a\u6c28\u916f
\nAlthough foamed polyurethanes form some 90% by weight of the total market for
\npolyurethanes, there is a wide range of solid polyurethanes used in many, diverse
\napplications.
\n\uf06e Solid polyurethane elastomers \u5f39\u6027\u4f53
\nMost polyurethane elastomers have excellent resistance to abrasion and attack by
\noil, petrol and many common solvents. They can be tailored to meet the needs of
\nspecific applications, as they may be soft or hard, of high or low resilience, solid or
\ncellular.
\n\uf06e Adhesives, binders and coatings \u7c98\u5408\u5242\u80f6\u6c34\u6d82\u6599
\nPolyurethanes are also used in flexible coatings for textiles and adhesives for film
\nand fabric laminates. Polyurethane coatings give the highest wear resistance to
\nsurfaces such as floors and the outer skins of aircraft. Polyurethane binders are used
\nto bind waste to produce new materials ranging from construction boards to sports
\nsurfaces.
\nCure \u719f\u5316
\nRefers to the completeness of the chemical reaction processes.
\n\uf06e Di-isocyanate \u4e8c\u805a\u4f53
\nA reactive chemical grouping of a nitrogen atom bonded to a carbon atom
\nbonded to an oxygen atom; -N = C = 0; a chemical compound, usually
\norganic, containing one or more isocyanate groups.
\n\uf06e Elastomer \u5f39\u6027\u4f53
\nA synthetic rubber-like material capable of rapid, reversible extension.
\n\uf06e Filler \u586b\u5145\u6750\u6599
\nAn inert material added to a polyurethane reaction mixture. Fillers are usually
\nsolid, particulate materials such as glass, silica or barytes.
\n\uf06e Flame retardant \u963b\u71c3\u5242
\nAn added substance which inhibits the initiation and\/or spread of flame.
\n\uf06e Functionality \u5b98\u80fd\u56e2
\nThe number of reactive groups in a chemical molecule.
\n\uf06e Hydroxyl \u7f9f\u503c
\nAn alcoholic group (-O-H). The reactive group in polyols.
\n\uf06e Mold \u6a21\u5177
\nEnclosure, usually metal, in which a polyurethane mixture reacts to give a
\nshaped article.
\n\uf06e Polyisocyanate \u805a\u8132
\nA polyisocyanate contains more than one isocyanate group.
\n\uf06e Polymer (Copolymer)\u9884\u805a\u4f53
\nA substance, natural or synthetic, which can be represented as at least two
\nrepeated monomer units. A copolymer contains more than one type of
\nmonomeric unit.
\n\uf06e Polyol
\nA substance containing several hydroxyl groups. A diol, triol and tetrol contain 2,
\n3 and 4 hydroxyl groups respectively.
\n\uf06e Polyurethane \u6c28\u57fa\u7532\u9178\u916f
\nPolymeric substance containing many urethane linkages.
\n\uf06e Self skinning \u81ea\u7ed3\u76ae
\nA foam reaction mixture which forms a skinned surface on being molded at a
\nspecified temperature and pressure.
\n\uf06e Slabstock \u5757\u6ce1
\nRigid or flexible polyurethane foam made in the form of a continuous block,
\nusually of approximately rectangular cross-section.
\n\uf06e Surfactants \u8868\u9762\u6d3b\u6027\u5242\u7845\u6cb9
\nSelected surfactants (surface-active materials), or mixtures of surfactants,
\nhelp in mixing incompatible components of the reaction mixture.
\n\uf06e Urethane \u7532\u9178\u916f
\nThe chemical group.
\n\uf06e Foams \u6ce1\u6cab
\nFoams are made by forming gas bubbles in the polymerising mixture, with the use
\nof a blowing agent. Foam manufacture can be carried out continuously, to produce
\ncontinuous laminates or slabstock, or discontinuously, to produce moulded items or
\nfree-rise blocks.
\n\uf06e Flexible foam \u8f6f\u6ce1\u6d77\u7ef5
\nFlexible foams can be produced easily in a variety of shapes by cutting or
\nmolding. Widely used in the furniture and automotive markets as comfortable and
\ndurable seating foam, they are also popular for mattresses and pillows.
\nFlexible foams can be produced in high and low densities. Low-density flexible
\nfoams are materials of densities 10-80kg\/m3, composed of lightly cross-linked,
\nopen cells, which enables air to flow through the structure very easily. Semi-rigid
\nvariants also have an open cell structure but different chemical formulations.
\nHigh density flexible foams have densities above 100kg\/m3. The range includes
\nmoulded self-skinning foams and microcellular elastomers. Self-skinning foam
\nsystems are used to make moulded parts with a cellular core and a relatively dense,
\ndecorative skin. The biggest applications of self-skinning foams and microcellular
\nelastomers are in moulded parts for upholstery and vehicle trim, and for shoe soling.
\n\uf06e Rigid foam \u786c\u6ce1
\nLow-density rigid foams (30kg\/m3 – 80kg\/m3) are highly cross-linked polymers
\nwith a closed cell structure – each bubble within the material has unbroken walls so
\nthat gas movement is impossible. These materials offer good structural strength in
\nrelation to their weight, combined with outstanding thermal insulation properties.
\nThis has led to their widespread use as an insulant in buildings, refrigerators,
\nfreezers and refrigerated transport vehicles.
\nAn HCFC (hydrochlorofluorocarbon), HFC (hydrofluorocarbon) or other
\nblowing agent is usually contained within the cells, and as these substances have a
\nmuch lower thermal conductivity than air, such closed-cell foams have a significantly lower conductivity than any open-celled foam. To retain this low
\nthermal conductivity the gas must not leak out. Consequently, rigid polyurethane
\nfoam insulation must have at least 90% closed cells and a density above 30kg\/m3.
\n\"\"
\n\"\"<\/p>\n","protected":false},"excerpt":{"rendered":"

WHAT IS POLYURETHANE ? Unlike most other polymers such as polyethylene, polystyrene and polyvinyl chloride which are polymers of the monomeric units ethylene, styrene and vinyl chloride respectively, … <\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-807","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"\/\/www.rushplease.com\/wp-json\/wp\/v2\/pages\/807","targetHints":{"allow":["GET"]}}],"collection":[{"href":"\/\/www.rushplease.com\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"\/\/www.rushplease.com\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"\/\/www.rushplease.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"\/\/www.rushplease.com\/wp-json\/wp\/v2\/comments?post=807"}],"version-history":[{"count":5,"href":"\/\/www.rushplease.com\/wp-json\/wp\/v2\/pages\/807\/revisions"}],"predecessor-version":[{"id":816,"href":"\/\/www.rushplease.com\/wp-json\/wp\/v2\/pages\/807\/revisions\/816"}],"wp:attachment":[{"href":"\/\/www.rushplease.com\/wp-json\/wp\/v2\/media?parent=807"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}