Polyurethane polymers properties

Thermosensitive hydrogels, 13 743 THERMOSET Thermoset recycling pyramid, 13 780-781 Thermoset elastomers, 20 71 Thermoset epoxy resins, curing of, 10 421 Thermoset flexible polyurethane foams properties of, 25 461 Thermoset matrix composites, 21 456 Thermo set molding properties of diallyl isophthalate, 2 262t Thermoset polymers, 25 455 cured, 10 425... 

For the work presented here, the polymers considered are in the general class of materials known as polyurethanes. Polyurethanes are particularly attractive for a study of the effect of chemical structure on damping since it is possible to change their Tg s over a wide range of temperatures (>100"C). This corresponds to a damping peak location that spans more than 10 decades of frequency. In addition, changes in polyurethane structure can be used to produce a transition that can vary from narrow to broad. To take advantage of these desirable properties, one must understand the dependence of Tg on the chemical structure of polyurethane polymers. 

Polyurethane is a condensation polymer generally formed by the reaction between a di-isocyanate and a hydroxylated-terminated resin known as polyol in the presence of a catalyst and a foaming agent The urethane foam formed as a result of this reaction is a cellular polymer that derives its mechanical properties in part from the cell matrix formed during its manufacture and in part from the intrinsic polymer properties. Choice of the di-isocyanate and polyol dictates the inherent polymer properties in addition filler materials may be added to the polymer to improve its mechanical properties. 

Homo and copolymers of tetrahydrofuran (THF) and alkylene oxides (AO) are used as soft segment glycols in the preparation of polyurethanes. In the process of producing the THF-AO homo and copolymers certain oligomeric cyclic ethers are also produced and can comprise 7-15 % of the polymer. These cyclic ethers are undesirable because when the polymers are used to prepare polyurethane the cyclic ethers tend to degrade the polyurethane s properties. 

The specific reactions of the uretoneimine additive and its derivatives are certainly not representative for polyurethane polymers in general. They still give further evidence for characteristic processes in the interphase on different metals. In addition, the mobility of the polymer network of this specific adhesive formulation and its mechanical properties will of course be affected by the associated substitution of each uretoneimine triple interlink by two linear connections. 

Urethane rubbers are produced from a number of polyurethane polymers. The properties exhibited are dependent upon the specific polymer and the compoimding. Urethane (AU) rubber is a unique material that combines many of the advantages of rigid plastics, metals, and ceramics, yet still has the extensibility and elasticity of rubber. It can be formulated to provide a variety of products with a wide range of physical properties. 

Synthetic-Natural Hybrid Polymers Based on Polyurethane Structures, Properties, and Applications... 

Chem. Descrip. Waterborne aliphatic polyester polyurethane polymer Uses Urethane for industrial wood, metal, and plastic coatings Features General purpose good adhesion to wide variety of substrates Properties Translucent dens. 8.8 Ib/gal vise. 125 cps pH 8.3 tens. str. 4000 psi elong. 200% (break) hardness (Sward) 70 VOC 261 g/l 35% solids 8.5% NMP Sancure 825 [Noveon]... 

There are numerous possibilities for the synthesis of polyurethanes, which provides a distinct advantage for tuning the polymer properties to specific applications. Table 4 overviews some possibilities. In addition, the use of surface-modifying additives (typically 1% or less by weight) in polyurethanes can enhance their biostability, or add other functionality to the polymers. ... 

As one of the blocks becomes polar relative to the other, the Krause theory (Section 4.7.1) predicts that phase separation will occur with shorter block lengths. Given the shorter block lengths, we are required to consider multiblock polymers of the form ABABAB in order to maintain high molecular weight and concomitant polymer properties. This chapter will consider two important classes of multiblock copolymers, the polyurethanes and the ionomers. 

In formulating polyurethane/urea systems using ultra-low monol PPG polyols, it was found that polyol MWD has a major effect on polymer properties. A broadened MWD is required to achieve a property profile similar to a PTMEG-based system. The MW-distribution effect is illustrated using TDI prepolymers cured with MBOCA, TDI moisture-cured prepolymers and aqueous polyurethane/urea dispersion coatings. 

Saraf, V., Glasser, W. G., Wilkes, G. L., and McGrath, G. E. Engineering plastics from lignin IV. Structure property relationships of PEG-containing polyurethane networks, Journal Applied of Polymer Science, 30, 2207 (1985). Sarkar, S. and Adhikari, B. Thermal stability of lignin-hydroxy-terminated polybutadiene-co-polyurethanes. Polymer Degradation and Stability, 73, 169-175 (2001). 

Polyurethanes prepared via transesterification of soybean and linseed oils with n-butanol in the presence of lipozyme (a lipase), also possess these improved properties, particularly in the case of MDI-based polyurethanes. Mechanical properties such as tensile strength, percentage elongation, elastic modulus, wear resistance, tear resistance. Shore A hardness, and thermostability of vegetable oil-based polyurethane IPNs showed significant improvement at a critical vinyl or acrylic polymer level. 

K. Kojio, S. Nakashima and M. Furukawa, Microphase-separated structure and mechanical properties of norbornane diisocyanate-based polyurethanes . Polymer, 2007, 48, 997-1004. 

C. Zhang and S. Feng, Effect of glycols on the properties of polyester polyols and of room-temperature-curable casting polyurethanes , Polym Int, 2004, 53, 1936-40. 

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