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, polyurethanes are not polymers with repeated units of
urethane in the regular manner and do not generally have an empirical formula that
is representative of all. They are basically polymeric reaction products of
polyhydroxy polymers such as polyether (or polyester) polyols and isocyanates. In
short, they are polymers containing the urethane linkage ( -NH-CO-O- ) which are
in no way the predominat chemical linkage in the polymers.
The majority of the polyurethanes made and used are foams which can range from
the super-soft and flexible to the hard and rigid. They can be produced as slabstock
or moulded into different shapes and sizes.
Blowing agent 发泡剂
A substance incorporated in the polymerising reaction mixture between a diisocyanate and a polyol to form gas bubbles, thereby producing foam.
Branching 接枝材料
Lateral extension points in a polymer chain.
Catalyst 催化剂
substance which accelerates the reactions of chemicals without being
consumed itself.
Chain extenders 扩链剂
Substances which lengthen the main chain of a polymer molecule causing
end-to-end attachments.
Cross-linking 架桥剂
Formation of bridges between different polymer chains.
Solid polyurethanes 硬固态聚氨酯
Although foamed polyurethanes form some 90% by weight of the total market for
polyurethanes, there is a wide range of solid polyurethanes used in many, diverse
applications.
Solid polyurethane elastomers 弹性体
Most polyurethane elastomers have excellent resistance to abrasion and attack by
oil, petrol and many common solvents. They can be tailored to meet the needs of
specific applications, as they may be soft or hard, of high or low resilience, solid or
cellular.
Adhesives, binders and coatings 粘合剂胶水涂料
Polyurethanes are also used in flexible coatings for textiles and adhesives for film
and fabric laminates. Polyurethane coatings give the highest wear resistance to
surfaces such as floors and the outer skins of aircraft. Polyurethane binders are used
to bind waste to produce new materials ranging from construction boards to sports
surfaces.
Cure 熟化
Refers to the completeness of the chemical reaction processes.
Di-isocyanate 二聚体
A reactive chemical grouping of a nitrogen atom bonded to a carbon atom
bonded to an oxygen atom; -N = C = 0; a chemical compound, usually
organic, containing one or more isocyanate groups.
Elastomer 弹性体
A synthetic rubber-like material capable of rapid, reversible extension.
Filler 填充材料
An inert material added to a polyurethane reaction mixture. Fillers are usually
solid, particulate materials such as glass, silica or barytes.
Flame retardant 阻燃剂
An added substance which inhibits the initiation and/or spread of flame.
Functionality 官能团
The number of reactive groups in a chemical molecule.
Hydroxyl 羟值
An alcoholic group (-O-H). The reactive group in polyols.
Mold 模具
Enclosure, usually metal, in which a polyurethane mixture reacts to give a
shaped article.
Polyisocyanate 聚脲
A polyisocyanate contains more than one isocyanate group.
Polymer (Copolymer)预聚体
A substance, natural or synthetic, which can be represented as at least two
repeated monomer units. A copolymer contains more than one type of
monomeric unit.
Polyol
A substance containing several hydroxyl groups. A diol, triol and tetrol contain 2,
3 and 4 hydroxyl groups respectively.
Polyurethane 氨基甲酸酯
Polymeric substance containing many urethane linkages.
Self skinning 自结皮
A foam reaction mixture which forms a skinned surface on being molded at a
specified temperature and pressure.
Slabstock 块泡
Rigid or flexible polyurethane foam made in the form of a continuous block,
usually of approximately rectangular cross-section.
Surfactants 表面活性剂硅油
Selected surfactants (surface-active materials), or mixtures of surfactants,
help in mixing incompatible components of the reaction mixture.
Urethane 甲酸酯
The chemical group.
Foams 泡沫
Foams are made by forming gas bubbles in the polymerising mixture, with the use
of a blowing agent. Foam manufacture can be carried out continuously, to produce
continuous laminates or slabstock, or discontinuously, to produce moulded items or
free-rise blocks.
Flexible foam 软泡海绵
Flexible foams can be produced easily in a variety of shapes by cutting or
molding. Widely used in the furniture and automotive markets as comfortable and
durable seating foam, they are also popular for mattresses and pillows.
Flexible foams can be produced in high and low densities. Low-density flexible
foams are materials of densities 10-80kg/m3, composed of lightly cross-linked,
open cells, which enables air to flow through the structure very easily. Semi-rigid
variants also have an open cell structure but different chemical formulations.
High density flexible foams have densities above 100kg/m3. The range includes
moulded self-skinning foams and microcellular elastomers. Self-skinning foam
systems are used to make moulded parts with a cellular core and a relatively dense,
decorative skin. The biggest applications of self-skinning foams and microcellular
elastomers are in moulded parts for upholstery and vehicle trim, and for shoe soling.
Rigid foam 硬泡
Low-density rigid foams (30kg/m3 – 80kg/m3) are highly cross-linked polymers
with a closed cell structure – each bubble within the material has unbroken walls so
that gas movement is impossible. These materials offer good structural strength in
relation to their weight, combined with outstanding thermal insulation properties.
This has led to their widespread use as an insulant in buildings, refrigerators,
freezers and refrigerated transport vehicles.
An HCFC (hydrochlorofluorocarbon), HFC (hydrofluorocarbon) or other
blowing agent is usually contained within the cells, and as these substances have a
much lower thermal conductivity than air, such closed-cell foams have a significantly lower conductivity than any open-celled foam. To retain this low
thermal conductivity the gas must not leak out. Consequently, rigid polyurethane
foam insulation must have at least 90% closed cells and a density above 30kg/m3.
