Polyurethane degradable segmented

Skaija GA and Woodhouse KA. In vitro degradation and erosion of degradable, segmented pol3mreth-anes containing amino acidbased chain extender. J Biomater Sci Polym Ed, 2001, 12, 851-873. Fromstein JD and Woodhouse KA. Elastomeric biodegradable polyurethane blends for soft hssue application. J Biomater Sci Polym Ed, 2002, 13, 391 06. 

As in the case of 73-series adhesives, degradation of 87 and 88-series polyurethanes was bimodal (Fig. 9). These adhesives were somewhat more stable than the 73-series (compare Fig. 6 with Fig. 9). Volatilization began at about 250°C. Assuming that the hard segments degrade first, this implies that the polyurea hard segments of 87- and 88-series polymers have better thermal stability than the polyurethane hard segments of the 73-series adhesives. 

After ammonolysis, ammonia is evaporated and can be reused after liquefaction, while degradation products of polyurethane hard segments (e.g., amines and chain extenders) and urea are removed by extraction. The pure polyol is left in the reactor. It can be removed mechanically or by extraction with liquid ammonia in which it is soluble. The recovered amines can be converted to the corresponding isocyanates and can be reused, along with polyols, in the same applications as before. A flow scheme of the recycling process is shown in Figure 6.9. 

Several studies have been conducted on biostable polyurethanes to elucidate the effects of hard segment chemistry on polyurethane degradation rate. Tang et al. [104,105] observed the effects of hard segment chemistry and hard segment content... 

Kavlock KD, Whang K, Guelcher SA, Goldstein AS. Degradable segmented polyurethane elastomers for bone tissue engineering effect of polycaprolactone content J Biomater Sci Polym Ed 2013 24(l) 77-93. 

In an NMR analysis of the effects of /-irradiation induced degradation on a specific polyurethane (PU) elastomer system, Maxwell and co-workers [87] used a combination of both H and 13C NMR techniques, and correlated these with mechanical properties derived from dynamic mechanical analysis (DMA). 1H NMR was used to determine spin-echo decay curves for three samples, which consisted of a control and two samples exposed to different levels of /-irradiation in air. These results were deconvoluted into three T2 components that represented T2 values which could be attributed to an interfacial domain between hard and soft segments of the PU, the PU soft segment, and the sol... 

Xia et al. found that the incorporation of MWNTs and SWNTs did not improve the first degradation temperature, but did improve the second degradation temperature (21). This indicates that carbon nanotubes may preferably interact with the soft segment in polyurethane structure. There were no significant differences between... 

A popular theory with azo materials is that their degradation products are always aromatic amines such as azo dyes. Ueda and coworkers observed that the azo bonds in segmented polyurethanes were reduced to hydrazo intermediates after incubation with human... 

Ethanox 376 is a stabilizer that provides heat stability by preventing thermo-oxidative degradation during processing and service life. It provides compatibility with resins and extraction resistance. It can be applied in polyolefins, such as polyethylene, polypropylene, polybutene-1 and other polymers such as engineering plastics, styrenes, polyurethanes, saturated and unsaturated elastomers, styrenics, rubber modified styrenics, segmented block copolymers, and PVC. 

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 sensitivity to hydrolysis is a key issue in many applications. The ester bond in 4GT-PTMO copolymers is sensitive to hydrolysis however, it is fairly protected since most of the ester is contained in a crystalline structure. The addition of a small amount (1-2%) of a hindered aromatic polycarbodiimide substantially increases the lifetime of this material in the presence of hot water or steam (Brown et al., 1974). Polyurethanes are susceptible to hydrolytic attack, especially those with polyester soft segments. However, polyester soft segment polyurethanes are generally more resistant to oils, organic solvents, and thermal degradation. lonomers will swell when exposed to water in fact, a commercial hydrated perfluorosulfonic ionomer (Nation) is used as a membrane separator in chlor-alkali cells. Styrene-diene copolymers and polyolefin TPEs are insensitive to water. 

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