Modified polyurethanes

Urethane alkyds and urethane oils are oil and alkyd resin-modified polyurethanes dissolved in a volatile solvent. Upon application and solvent evaporation, the coating is crosslinked and cured via oxidation by atmospheric oxygen. 

Coal tar-modified polyurethane is a cold-applied liquid waterproofing system. The system by Sonneborn is an example of this approach to waterproofing. It is applied as a liquid at the rate of 10-15 mils/coat. The coating dries hard, but has some elasticity. This material may be attacked by acids in groundwater but can be defended by a protection board. The performance of any liquid-applied waterproofing systems is limited by the capabilities of the applicator (it is difficult to achieve even coats on vertical surfaces). 

Polymer-modified asphalt is a cold-applied liquid waterproofing system. As with the Sonneborn system mentioned above, the quality of the installation depends on the applicator (it is difficult to achieve an even coating on a vertical surface). High-grade polymer-modified asphalt is superior to coal tar-modified polyurethane in elasticity, crack-spanning ability, and resealability, but inferior in its resistance to chemicals. 

These criteria were developed by the UK PU foam industry and were intended to differentiate the melamine or exfoliated graphite containing combustion modified PU foams from the standard, high resilience and flame retarded (chloro and bromo phosphate) containing PU foams (Table IV). This distinction was required because large scale burning tests of real arm chairs and furnished rooms had demonstrated the superiority of the combustion modified polyurethane foams. 

Adherent films would not necessarily require formation of covalent bonds at the Interface, since localized lntermolecul u dispersion forces that u e operative In the adsorption of coatings (with good wetting properties) should provide stable interfacial bond conditions. Among candidate materials which could fulfill the requirements of good adhesion and substrate protection from moisture are epoxy-modified polyurethanes and epoxy-siloxane polymers. 

Imanishi et al. [33] pointed out that there was an optimum point at which the tethering density of PEO chains makes a polybutadiene urethane surface biocompatible. They also reported that bovine plasma FGN and bovine y-globulin adsorbed on the PEO-modified polyurethane were completely denatured, in comparison with 4-38% denaturation of BSA adsorbed. 

Mathur AB, Collier TO, Kao WJ, Wiggins M, Schubert MA, Hiltner A, Anderson JM. In vivo biocompatibility and biostability of modified polyurethanes. Journal of Biomedical Materials Research 1997, 36, 246-257. 

Another manufacturing method involves irradiation by UV light, in which acrylic-modified polyurethane resins are used. Reactive fluorinated oligomers are reviewed in Reference 36. 

Najafi-Mohajeri, N. Jayakody, C Nelson, G.L. Cone calorimetric analysis of modified polyurethane elastomers and foams with flame-retardant additives. In Fire and Polymers. Materials and Solutions for Hazard Prevention, Nelson, G.L., Wilkie, C.A., Eds. ACS Symposium Series 797 American Chemical Society Washington, 2001 pp. 79-89. 

Polymerizing acrylic monomers in the presence of oil-modified polyurethane leads also to a grafting onto the polyacrylics, resulting in dispersions suitable for stable water-borne latexes with good adhesion properties and fair hardness properties [103]. 

Comparative studies are presented that demonstrate that homopolyurethane and segmented copolyurethane elastomers and plastics and rubber-modified polyurethane glasses with properties similar to counterparts formed from oil-... 

Table IV. Tensile Properties of Polymyrcene-Modified, Polyurethane Resins...

Foams Component/Modifier Polyurethanes Collagen-based a 230... 

Modified polyurethanes as shown in Fig. 4.6 are used for valuable hand variations and as additives for cellulose crosslinkers. Their flexible and elastic films on the fibre surface improve elastic resilience, which is, for example, important for pile fabrics. The principle of their elasticity is, as in elastan fibres, the molecular combination of so-called weak and hard segments. The large weak... 

Nelson (16, 39) reported a method of making polyurethane-foam composites by means of the SRIM process. Two different types of polyurethane materials were used an amine-modified polyurethane suitable for static elastomer uses and a polyurethane material with high crosslink density designed for use as a microcellular structural material. 

Although polyurethane has been the principle polymer commercialized 1n the RIM process, modified polyurethane and... 

Table 4 summarizes wire enamels such as a standard polyurethane, an imide modified polyurethane, a solderable poly(ester-imide), and a standard polyfes-ter-imide) for comparison of properties and soldering characteristics. 

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