Poly urethane s

Biobased polyols with high functionality have been synthesized by ring-opening epoxidized sucrose esters of soybean oil with methanol under acidic conditions, and were subsequently formulated with blocked isocyanates to form one package PUs (16). Biobased PU coatings were prepared by formulating the polyols with blocked polyisocyanates based on isophorone diisocyanate and hexamethylene diisocyanate (HDI). 

The coatings can be applied to steel substrates. A commercial soybean oil polyol was used and was found to have a lower modulus and a lower crosslink density and glass transition temperature compared to coatings formulated with sucrose soyate polyols (16). 

Naturally occurring oleic acid and undecylenic acid derivatives can be used to S5mthesize semicrystalline PUs via an AB-type polycondensation. The AB-type monomers were self-polycondensed in two ways (17)  

Reasonably high molar mass PUs can be obtained. These PUs exhibit a fair thermal stability with no significant weight loss below 200°C. PUs based on imdecylenic acid show a thermoplastic behavior with well-identified melting transitions. PUs prepared from imdecylenic acid using different methods show different glass and melting transitions. 

Two glass transition temperatures are ascribed due to soft and hard segments in the case of PUs synthesized from oleic acid. Thus, a phase-separated morphology is suggested (17). 

Examples of useful acid scavengers for poly(urethane)s (PU)s include hydroxides, carbonates, bicarbonates, amines, zeolites, hydro-talcites that will all adequately neutralize acid that may be generated during the PU reaction. 

However, some common acid scavengers will adversely affect the PU reaction as they result in materials with poor physical properties. Thus for PUs, more preferred acid scavengers are selected from the group of epoxides and diepoxides (8). 

Transparent two phase polyester-polycarbonate compositions, US Patent 7425590, assigned to Eastman Chemical Company, 

Sukhadia, E.M. Lanier, and L. Moore, Polyethylene compositions, WO Patent 2 007 055 977, assigned to Chevron Phillips Chemical Co. and Sukhadia Ashish M and Lanier Elizabeth M and Moore Louis, May 18,2007. 

Bheda and A. Dorman, Propylene polymer compositions stabilized with potassium citrate as an acid scavenger, US Patent 6090877, assigned to BP Amoco Corp., July 18,2000. 

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PIB based thermoplastic poly(urethane)s (TPU)s have been synthesized. These composites exhibit enhanced mechanical properties. Poly(tetramethylene oxide) (PTMO) has been used as a compatibi-lizer. 

Liao and coworkers [88] copolymerized poly(urethane)s with BMI to im-... 

The isocyanate moiety is highly reactive towards poly(ol)s. This reaction is utilized in the preparation of poly(urethane)s (PU)s. With catalysts such as amines, the reaction occurs rapidly at room temperature. Consequently, urethane polymers are mostly prepared from two components, one containing the isocyanate component, and the other containing the polyol component. The components are nuxed prior to curing. 

Blends of a PAI and poly(aryl ether ketone) exhibit improved solvent resistance and hydrolytic stability. Blends of sulfonated poly(ether ether ketone) and PAI have been tested as membrane materials for direct methanol fuel cells. Miscible blends can be obtained. Blends of poly(urethane)s (PU)s and PAI, as the minor component have been reported for membrane applications. The resulting membranes are immiscible. Phase separation occurs when the amount of PU decreases. 

A large variety of hyperbranched polymers with acrylate, vinyl ether, allyl ether, or epoxy functions were studied as multifunctional cross-linkers in coatings and in thermosets, using thermal as well as UV curing methods Clearly, polyesters are most prominent in the field, with the Perstorp Boltom products leading in technical studies. The commercialized poly(esteramide)s from DSM, sold under the trade name Hybrane polyethylenimines from BASF AG, available under the trade name TupasoF and poly(urethane)s (PUs) and polyesters developed by BASF are examples for hyperbranched polymers suited for coatings and resin products. 

Eventually, bis(2-hydroxyethyl)isosorbide may be chemically modified to form, bisacrylate esters or bis vinyl ethers, which can be used in photochemical or thermal cured vinyl resin compositions. Alternatively, this compound may be reacted with epichlorohy-drin and bases to form bis(glycidyl ether) adducts which may be used in epoxy resins. Bis(2-hydroxyethyl)isosorbide will find use as a monomer in many polymeric compositions, such as polyesters, poly(urethane)s, poly(ether sulfone)s. 

Studies of the cytocompatibility indicated that all poly (urethane)s are nontoxic. The sulfonic acid groups affect solubility in water imder alkaline conditions and the materials become insoluble in acidic conditions. This pH sensitivity makes the pol5uner attractive for biopiinting applications. By adding acetic acid into an inkjet cartridge and printing it onto a poly(urethane)s solution with a pH above 8.7, precision fabricated scaffolds can be obtained (71). 

Labow RS, Tang Y, McCloskey CB et al (2002) The effect of oxidation on the enzyme-catalyzed hydrolytic biodegradation of poly (urethan)s. J Biomater Sci Polym Ed 13 651-665... 

Labow RS, Meek E, Santerre IP. The biodegradation of poly(urethane)s by the estero-lytic activity of serine proteases and oxidative enzyme systems. 1 Biomater Sci Polym Ed 1999 10(7) 699-713. 

Plasticized poly(vinyl chloride) (PVC), poly(urethane)s, poly(eth-ylene) (PE), and poly(ester)s are particularly sensitive to microbial attack. Flexible PVC is by far the main plastic in which biostabilizers are incorporated, followed by poly(urethane) foams, and other resins. PVC itself is resistant to microbial attack, however, plasticizers, fillers, pigments, lubricants, and other additives used in PVC are... 

Since poly(ester) poly(urethane)s bear ester groups they are likewise subject to hydrolytic degradation (5). 

In addition, poly(urethane)s and segmented polyfurethane urea)s derived from lysine diisocyanate, can be enzymatically degraded by various proteases. Thiol proteases, such as papain, bromelain, and ficin, show a high activity. In addition, protease K and chymotrypsin hydrolyze the poly(urethane)s (9). 

Hydrol)dic stabilizers can be included in poly(ester) poly(ol) based poly(urethane)s. Two commercially available carbodiim-ide based hydrolytic stabilizers are known as Stabaxol P and Stabaxol P-100. They are available from Rhein Chemie of Trenton, N.J., and are effective at reducing the susceptibility of the material to hydrolysis (5). 

Besides of hydrolytic stabilizers, the hydrolytic stability of poly-(urethane)s can be tailored by the structure of tire backbone. 

Synthetic Gels Prepared by the Formation of Poly(Urethane)S... 

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