Polyurethanes polyurethane-based materials

Sherman LM (2007) Polyurethanes bio-based materials capture attention. Plastics technology online. Available at http //www.ptonline.com/articles/200712fa4.html. Accessed 30 May 2011... 

Among the new being consider for reactive processing into polyurethane-based materials, the so-called polyester amines, in combination with chain extenders, which also contain amine groups, are especially promising.19 Using these materials allows the synthesis of polymers with polyurea instead of polyurethane bonds. This results in materials with improved impact strength and lower water absorption. 

The most successful application of the RIM-process is in the production of polyurethane-based materials. Other systems, such as composites based on polycaproamide, epoxy resins, and unsaturated polyesters can also be processed by reactive injection molding. New reactive systems have also been specially created for the RIM-process260 because of the exceptional opportunities it offers for manufacture of finished articles from engineering plastics with a high modulus of elasticity and impact strength. The automotive industry, which is the main customer for RIM-articles, can utilize this technology to manufacture of massive parts such as body panels, covers, wings, bumpers and other made of newly developed plastics. 

A coating described by Worley and coworkers was shown to efficiently kill both on contact and by release [137], The polyurethane-based material contains quarternary ammonium groups for contact-killing and AMialamine groups for releasing chlorine... 

Polyurethane-based materials having hot water resistance, strength, and chlorine and chemical resistance were prepared by the author [4] by reacting poly(n-butyl acrylate) containing mercapto termini with 4,4 -diphenylmethane diisocyanate and 1,4-butanediol. 

Other industrial applications include the fabrication of two-part epoxy resins (similar to those commonly found in household maintenance stores) [95-97], These were synthesized using triglycerides and diamines. These resins are often used as adhesives these have also been studied using soybean oil, which provided beneficial properties in terms of fast curing, thermal stability and ease of removal (peel strength) [98], A blend of divinylbenzene/styrene/tung oil mix gave a polyurethane-based material which behaved like a smart polymer with shape memory behaviour [66]. 

P. Alves, P. Ferreira, M.H. Gil, Biomedical Polyurethane-Based Materials, in Polyurethane Properties, Structure and Applications, Nova Publishers, New York, 2012. ISBN ... 

F.J. Davis, G.R. Mitchell, Polyurethane based materials with applications in medical devices, in Bio-materials and Prototyping Applications in Medicine, Springer, NY, 2008, pp. 27 8. 

Christensen L (2002) HOME OF the blue morpho butterfly. New York Times (12 May) Crossland RK, Harlan Jr, JT (1975) Block copolymer adhesive compositions. U.S. Patent 3917607 Davis FJ, Mitchell GR (2008) Polyurethane based materials with applications in medical devices. In Bartolo P, Bidanda B (eds) Bio-materials and prototyping applications in medicine. Springer, New York, pp 27 8. ISBN 9780387476827 Djiauw LK, Icenogle RD (1986) Low smoke modified polypropylene insulation cranpositions. U.S. Patent 4622352... 

H.W. Bonk and D.J. Goldwasser, Membranes of polyurethane based materials including polyester polyols, US Patent 7 078 091, assigned to Nike, Inc. (Beaverton, OR), July 18,2006. 

Synthetic Resins. Various polymers and resins are utilized to produce some specialty carbon products such as glassy carbon or carbon foam and as treatments for carbon products. Typical resins include phenoHcs, furan-based polymers, and polyurethanes. These materials give good yields of carbon on pyrolysis and generally carbonize directly from the thermoset polymer state. Because they form Httle or no mesophase, the ultimate carbon end product is nongraphitizing. 

Thermoplastic polyurethane elastomers have now been available for many years (and were described in the first edition of this book). The adipate polyester-based materials have outstanding abrasion and tear resistance as well as very good resistance to oils and oxidative degradation. The polyether-based materials are more noted for their resistance to hydrolysis and fungal attack. Rather specialised polymers based on polycaprolactone (Section 25.11) may be considered as premium grade materials with good all round properties. 

Whilst approximately twice the raw material cost of TPO- and S-B-S-type polymers, thermoplastic polyurethane elastomers find applications where abrasion resistance and toughness are particular requirements. Uses include gears, timing and drive belts, footwear (including ski boots) and tyre chains. Polyether-based materials have also achieved a number of significant medical applications. There is also some minor use as hot melt adhesives, particularly for the footwear industry. 

Example 11. One-Component, Moisture-Cure Polyurethane Sealant. This example is of a low-hardness, high-elongation, moisture-curable polyurethane sealant. The material is based on a low-%NCO prepolymer made from 4,4 -MDI and a low-unsaturation (low-monol-content) Acclaim polyol from Bayer. It is adapted from (a) J. Lear et al., Adhesives Age, February 1999, pp. 18-23 and (b) B. Lawrey, et al., presented at UTECH 2000, The Hague, The Netherlands, March 30, 2000, Crain Communications London, 2000. 

Siloxane containing interpenetrating networks (IPN) have also been synthesized and some properties were reported 59,354 356>. However, they have not received much attention. Preparation and characterization of IPNs based on PDMS-polystyrene 354), PDMS-poly(methyl methacrylate) 354), polysiloxane-epoxy systems 355) and PDMS-polyurethane 356) were described. These materials all displayed two-phase morphologies, but only minor improvements were obtained over the physical and mechanical properties of the parent materials. This may be due to the difficulties encountered in controlling the structure and morphology of these IPN systems. Siloxane modified polyamide, polyester, polyolefin and various polyurethane based IPN materials are commercially available 59). Incorporation of siloxanes into these systems was reported to increase the hydrolytic stability, surface release, electrical properties of the base polymers and also to reduce the surface wear and friction due to the lubricating action of PDMS chains 59). 

Most automobile and furniture seating, foam mattresses, carpet underlay-ment, and other similar products are made from polyurethanes based on polypropylene glycol (PPG). PPG is the preferred raw material for these type of polymers because of the wide variation of possible properties of the end product and the relatively low cost. 

Polyols and polyisocyanates are major ingredients for polyurethane (PU)-based composite propellants in addition to chain extenders and catalysts etc. A brief description on these materials is considered necessary in order to understand the chemistry of composite propellants in a better way. Polyols are the largest group of raw materials for PUs. The properties of PUs/PU products are largely determined by their chemical composition and molecular mass. They may be broadly classified [87] as ... 

There has been a group of catalysts developed by polyurethane raw material suppliers with the polyurethane market in mind. Mercury-based catalysts, because of their toxicity, have been banned in some countries or severe restrictions placed on their use. Bismuth-based catalysts are recommended in their place. 

Heat plays an important part in the curing of polyurethanes. The reaction itself gives out heat, so this must be taken into account in determining the temperature of the mold. The mold should be at the maximum temperature the curing prepolymer will reach. An MDI-based system will release heat more rapidly than a TDI-based system therefore the mold has to be hotter than when using a TDI-based material. 

There are two methods to soften (plasticize) polyurethanes. The first is to use reactive plasticizers such as long-chain hydroxyl or amine-based materials, and the second is to use a compatible nonreactive plasticizer such as DIOP or Benzoflex 9-88. 

Polyether polyurethanes are less stable to higher temperatures than the polyester-based materials. The ether linkage in the soft segment is attacked... 

The hardness of polyurethanes can be obtained by either the density of the hard segments, the choice of curative, or the addition of plasticizer. The importance of hardness is to control the rigidity of the part (if not reinforced) or its softness to conform to the shape of some other object it passes over. For very low hardness (< 60 A) applications such as rolls, TDI esters are the most suited, whereas ether-based materials are least suited. Hard materials do have better abrasive resistance than soft materials. 

Low-temperature applications are controlled by the stiffening of the polyurethane as the temperature goes from 20°C down to -20°C. In these applications, MDI ethers are the most suited, whereas ester-based materials become very stiff. At very low temperatures, esters have a lower brittle point than ethers but they must be kept from crystallizing. 

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